GIST RESEARCHERgist.edu.in/gist/wp-content/uploads/2019/03/GIST-RESEARCHER_Jul… · GIST RESEARCHER Journal of Science and Technology Vol. 3 Issue. 2 July 2015 Improvement of Power

GIST RESEARCHER Journal of Science and Technology

Vol. 3 Issue. 2 July 2015

Improvement of Power Quality with Fuzzy Based Unified Power Quality Conditioner with Fast

Energy Storage S.Sridhar, N.Sri Lakshmi Nanda

Simulation of Grid Connected PV System with Power Quality Improvement Using Fuzzy Logic

Controller T.Ravi Kumar , K.Sai Vasanthi

Low Power Multi-Bit Flip-Flops Design for VLSI Applications Yeturi Mallikarjuna, Chiranjeevi

Thokala

Employee Retention and its Improvement Strategies Sd. Ghousul Asvia Begum

Effects of Road Geometrics on Accidents: A case Study of NH-45 through Nellore to Kavali

Pranay Kumar.G, Anvesh Kumar.M, Dr.Suresh Babu.T

Role of Medicinal Plants in Health Care Importance and Conservation B.Sirisha

IAAS: Improving Efficiency of Cloud Architecture Using DAS and SAN B.Susrutha,

K.VenkataRamana, I.Shalini

Study and Comparisons of Mechanical Properties, Durability and Permeability of M15, M20, M25

Grades of Pervious Concrete with Conventional Concrete Sai Sindhu K, Suresh Babu T

Closed Loop Speed Control of BLDC Motor with PI Controller under Different Loading

Conditions Murali Dasari , M.Ashok

GEETHANJALI INSTITUTE OF SCIENCE & TECHNOLOGY Approved by AICTE, New Delhi & Affiliated to JNTU, Anantapur)

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Patrons

D. B. Ravi Reddy, Chairman, Ushodaya Educational Society

N. Sudhakar Reddy, Secretary, Ushodaya Educational Society

Chief Editor

Dr. G. Subba Rao,

Principal, GIST

Associate Editor

Dr. Shaik. Mahaboob Basha,

Professor in ECE & Head R & D, GIST

Honorary Editors

Dr. K. Hemachandra Reddy, Prof. in Mechanical Engg., JNT University,

Ananthapur

Dr. S.Varadarajan, Prof. in ECE & Head, ECE, SV University, Tirupathi

Dr. Nagendra Prasad, Prof. in Civil Engg., & Registrar, VSU, Nellore

Dr. S. Ramakrishna, Dean, KL University, Vijayawada

Dr. G. Sriram, Head, Mech. Engg., SCSVMV University, Kanchipuram

Dr. R. Ramesh, Prof. in Mech. Engg., SVCE, Chennai

Editorial Board

Prof. T.N.V.L.N.Kumar, Prof. & Head, Dept. of EEE

Dr. T.Suneel Kumar, Prof. & Head, Dept. of Mechanical Engg

Mr. P.Raghava Reddy, Head &Assoc. Prof. in Dept. of ECE

Mr. C. Prakash, Prof. & Head, Dept. of Civil Engg

Dr. Y. Jahnavi, Prof. & Head, Dept. of CSE

Dr. A. Jaffar Sadiq Ali, Professor in Dept . of EEE

Dr. P. Vinoth Kumar, Associate Professor in Dept . of EEE

Mr. K. Naveen, Asst. Prof. in ECE Dept.

Mr. T. Ravi kumar, Assoc. Prof. in EEE Dept. Mr.

Mr.V.Venkateswarlu , Asst.Prof in English.

Mr.M.Ganapathi, Assoc.Prof in Maths

Mr.K.Narayana, Asst.Prof in Maths

Mrs.D.Swaroopa, Asst.Prof in S&H

EDITORIAL The GIST RESEARCHER, Journal of Science and Technology, launched from Geethanjali

Institute of Science & Technology, Nellore, aims at providing a forum to the research community for

presentation of original work, reviews and discussion of latest developments in various fields of

engineering. Research culture should form an integral part of an Engineering College and a Technical

Journal with papers and articles exclusively contributed by the faculty members of the College will go a

long way in inculcating the apt research culture in the institution. This In house Journal of Science and

Technology, the first issue of which is being launched, is an attempt in this direction. The current

volume contains research papers as well as perceptive articles by the staff and students of the college.

The papers span a wide range including basic sciences and management science, apart from the

engineering disciplines.

This Journal is a culmination of our efforts in adding a scientific and technological flavor to the

services that are offered from GIST. The scenario of globalization had provoked the theme of quality

and standard blended with high level of competence amongst the industrial sectors. The present day

technological advancements are more rapid and recommend an amalgamated Engineering curriculum

warranting students to equip with creative thoughts and multi level skills.

This Journal shall motivate the young minds to put forward their technical ideas in a lucid way

and develop the art of publishing one’s own technical findings. This issue is exclusively devoted for

publishing the research/project works carried out experimentally, analytically or both in different fields

of Science, Engineering and Technology. I wish the editorial Board for their strenuous efforts in making

this issue blossom with contents. Indeed such efforts are never possible for us without the stupendous

support of our noble and service minded Management members.

I hope all our readers would be enlightened through this issue, which shall knock the doors of

numerous enthusiastic readers every year. I request all the teachers and students keep writing to us and

send their valuable technical articles for publication.

CONTENTS

Title of the Paper Page No.

Improvement of Power Quality with Fuzzy Based Unified Power Quality Conditioner

with Fast Energy Storage S. Sridhar, N. Sri Lakshmi Nanda 01

Simulation of Grid Connected PV System with Power Quality Improvement Using

Fuzzy Logic Controller T. Ravi Kumar, K. Sai Vasanthi 08

Low Power Multi-Bit Flip-Flops Design for VLSI Applications Yeturi Mallikarjuna,

Chiranjeevi Thokala 15

Employee Retention and its Improvement Strategies Sd. Ghousul Asvia Begum 21

Effects of Road Geometrics on Accidents: A case Study of NH-45 through Nellore to

Kavali Pranay Kumar.G, Anvesh Kumar.M, Dr.Suresh Babu.T 26

Role of Medicinal Plants in Health Care Importance and Conservation B.Sirisha 31

IAAS: Improving Efficiency of Cloud Architecture Using DAS and SAN B.Susrutha,

K.VenkataRamana, I.Shalini 34

Study and Comparisons of Mechanical Properties, Durability and Permeability of

M15, M20, M25 Grades of Pervious Concrete with Conventional Concrete 42

Sai Sindhu K, Suresh Babu T

Closed Loop Speed Control of BLDC Motor with PI Controller under Different Loading 48

Conditions Murali Dasari , M.Ashok

GIST RESEARCHER In-house Journal of Science and Technology, VOLUME-3, ISSUE-2, JULY-2015

1

Improvement of Power Quality with Fuzzy Based Unified Power

Quality Conditioner with Fast Energy Storage

*S.Sridhar, **N.Sri Lakshmi Nanda,

*Associate professor & HOD, Department of EEE, Geethanjali Institute of Science & Technology, SPSR Nellore,

**PG Student, M.Tech (Power Electronics), Geethanjali Institute Of Science & Technology, SPSR Nellore,

Abstract - One of the major concerns in electricity

industry today is power quality. It becomes especially

important with the introduction of advanced and

complicated devices, whose performance is very

sensitive to the quality of power supply. The electronic

devices are very sensitive to disturbances and thus

industrial loads become less tolerant to power quality

problems such as voltage dips, voltage sags, voltage

flickers, harmonics and load unbalance etc. At

present, a wide range of very flexible controllers,

which capitalize on newly available power electronics

components, are emerging for custom power

applications. Among these, the distribution static

compensator, dynamic voltage restorer and unified

power quality conditioner which is based on the VSC

principle are used for power quality improvement. In

this paper, a fuzzy logic controller with reference

signal generation method is designed for UPQC. This

is used to compensate current and voltage quality

problems of sensitive loads. The results are analyzed

and presented using matlab/simulink software.

Keywords: power quality, upqc, voltage sag, fuzzy

logic controller

I. INTRODUCTION

HERE has been a continuous rise of nonlinear loads

over the years due to intensive use of power electronic

control in industry as well as by domestic consumers of

electrical energy. The utility supplying these nonlinear

loads has to supply large vars. Moreover, the harmonics

generated by the nonlinear loads pollute the utility. The

basic requirements for compensation process involve

precise and continuous VAR control with fast dynamic response and on-line elimination of load harmonics. To

satisfy these criterion, the traditional methods of VAR

compensation using switched capacitor and thyristors

controlled inductor coupled with passive filters are

increasingly replaced by active power filters (APFs).

The APFs are of two types; the shunt APF and the

series APF. The shunt APFs are used to compensate

current related problems, such as reactive power

compensation, current harmonic filtering, load

unbalance compensation, etc. The series APFs are used

to compensate voltage related problems, such as voltage

harmonics, voltage sag, voltage swell, voltage flicker, etc. The unified power quality conditioner (UPQC)

aims at integrating both shunt and series APFs through

a common DC link capacitor. The UPQC is similar in

construction to a unified power flow controller (UPFC).

The UPFC is employed in power transmission system,

whereas the UPQC is employed in a power distribution

system. The primary objective of UPFC is to control the

flow of power at, fundamental frequency. On the other

hand the UPQC controls distortion due to harmonics

and unbalance in voltage in addition to control of flow

of power at the fundamental frequency. The schematic block diagram of UPQC is shown in Fig. 1. It consists

of two voltage source inverters (VSIs) connected back-

to-back, sharing a common DC link in between. One of

the VSIs act as a shunt APF, whereas the other as a

series APF. The performance of UPQC mainly depends

upon how quickly and accurately compensation signals

are derived. Control schemes of UPQC based on PI

controller has been widely reported. The PI control

based techniques are simple and reasonably effective.

However, the tuning of the PI controller is a tedious job.

Further, the control of UPFC based on the conventional PI control is prone to severe dynamic interaction

between active and reactive power flows. In this work,

the conventional PI controller has been replaced by a

fuzzy controller (FC). The FC has been used in APFs in

place of conventional PI controller for improving the

dynamic performance. The FC is basically nonlinear

and adaptive in nature. The results obtained through FC

are superior in the cases where the effects of parameter

variation of controller are also taken into consideration.

The FC is based on linguistic variable set theory and

does not require a mathematical model. Generally, the

input variables are error and rate of change of error. If the error is coarse, the FC provides coarse tuning to the

output variable and if the error is fine, it provides fine

tuning to the output variable. In the normal operation of

UPQC, the control circuitry of shunt APF calculates the

compensating current for the current harmonics and the

reactive power compensation. In the conventional

methods, the DC link capacitor voltage is sensed and is

compared with a reference value. The error signal thus

derived is processed in a controller. A suitable

sinusoidal reference signal in-phase with the supply

voltage is multiplied with the output of the PI controller to generate the reference current. Hysteresis band is

normally (most often but not always) is imposed on top

and bottom of this reference current. The width of the

hysteresis band is so adjusted such that the supply

current total harmonic distortion (THD) remains within

the international standards. The function of the series

APF in UPQC is to compensate the voltage. The control

circuitry of the series APF calculates the reference


2

voltage to be injected by the series APF by comparing

the terminal voltage with a reference value of voltage.

II. POWER QUALITY PROBLEMS IN

DISTRIBUTION NETWORK WITH HIGH

PENETRATION OF DGS

In distribution network with high penetration of DGs,

enough power support is used to restraint output power

fluctuation. The power could be supplied by energy

storage technology, which includes two aspects: one is

high efficient mass storage, and the other is fast and

efficient energy conversion. Energy storage technology

applied in power system can realize peak load shifting

and system reserve demand reduction. Meanwhile, it would provide technical support for reducing network

power loss and improving power quality. Super

capacitor storage is normally used for smoothing the

power of short duration, high power load or used in

high peak power situation such as high power DC motor

starting and dynamic voltage restorer. When it comes to

voltage sags or instantaneous disturbance, Super

capacitor storage technology is able to improve the

power supply and quality. Thus, this technology is

suitable for solving power quality problems in

distribution network with high penetration of DGs.

Custom power technology, based on power electronic technology, could provide power supply up to reliability

and stability level which users required in MV/LV

distribution network system. UPQC, with feature of

series compensation and parallel compensation being

integrated together, has been considered as the most full

featured and effective one of all DFACTS technologies

so far. To improve power quality of distribution

network with the high penetration of DGs, developing

custom power technology based on UPQC, which can

inject active power during the voltage regulation and

integrate to reactive compensation, is a feasible strategy.

Fig.1. Structure scheme of UPQC

Traditional UPQC used in power distribution system,

integrating series compensation voltage principle and

parallel compensation voltage principle in one device,

can compensate three-phase asymmetric and

harmonicon both mains supply voltage and nonlinear

loads. UPQC is composed of the main circuit shown in

Fig.1, including series and parallel PWM converter, and

the control circuit. There are two basic control

strategies, i.e. direct control scheme and indirect control

scheme. Direct control scheme means series converter

is controlled as sinusoidal current source to isolate

voltage disturbance comes from grid and load. And

parallel converter is controlled as sinusoidal voltage

source to avoid load reactive power, load harmonic

current and unbalance from being injected into grid. On

the other side indirect control scheme means series converter works as a non-sinusoidal voltage source,

outputting compensation voltage which offsets grid

voltage distortion and fundamental deviation,

accordingly it ensures load voltage being rated

sinusoidal voltage.

Meanwhile, parallel converter works as an non-

sinusoidal current source, outputting reactive power and

harmonic current which offset reactive load power and

load harmonic current, accordingly it could make the

injected current be sinusoidal and running under unit

power factor by compensating reactive power and harmonic current. Indirect control scheme by researched

more common is mainly discussed in this paper. With

the series and parallel PWM converter topology, three

phase four-leg circuit structure implements both three-

phase and single phase structure, as a result, it is more

flexible and versatility. And three-phase control

systems can drive unbalanced loads as a result of three

phases being mutually independent. Therefore, it

chooses the three-phase four-leg circuit structure as the

topology of power quality improving device.

In view of the above, this paper presents a kind of three phase four-wire power quality conditioning device

based on fast energy storage named Energy-storage

UPQC (UPQC) aiming for power quality problems in

distribution network with high penetration of DGs.

III. STRUCTURE OF UPQC

As shown in Fig. 2, the main circuit system structure of

UPQC includes series converter, parallel converter,

booster and discharge unit which consisting of super

capacitor energy storage and DC/DC converter,

outputting power transformer TsA~TsCof series converter, output filters Ls and Cs of series converter

and inductance Lp of parallel converter. The electric

interfaces A1, B1, C1, and N1 connect distribution

network source and the A2, B2, C2, and N2 connect

various loads. Two sets of three-phase four-leg

converter respectively compose the series and parallel

converters of the UPQC. The series converter output

enters into distribution network via LC filter and

transformer in series, while the parallel device output

enters into distribution network with filter inductance in

parallel.

The switching sequence could be shown in Fig.2. When UPQC accesses to distribution network and sets to

work, the DC bus voltage equals to that of the super

capacitor bank. Then close contactors KMp2, 380V AC


3

power supply charges to the dc side via pre-charge

resistance R1 and parallel converter. When charging

completes, close KMp1, and break KMp2 and DC/DC

converter starts to work. Adjust the DC side voltage to

nominal reference level 690V. Detect unbalanced

degree and harmonic content of mains supply voltage

and load current in load side, in order that parallel

converter could be put into operation when over ranging

problem happens. And when voltage problems like

voltage sag and swell happen to mains supply, series converter will be put into operation and output

compensation voltage until the problems are solved.

Then series converter quits working and the SCRA,

SCRB and SCRC bypass.

Fig.2. Main circuit system structure of UPQC

The single phase structure schematic diagram of UPQC

is illustrated in Fig. 3. Series converter output voltage

vector to compensate voltage unbalance and harmonic

of power supply side. Parallel converter is used to solve

power quality problems in load side, such as unbalance

and harmonic of nonlinear load including reactive compensating and current harmonic. Super capacitor

energy storage and DC /DC converter buffer reactive

power, exchange and provide energy for voltage

compensation. As a result, decoupling series converter

and parallel converter is implemented. Moreover,

voltage quality problems of power interruption, which

beyond the reach of traditional UPQC, can be resolved

successfully.

Fig. 3.The single phase structure schematic of UPQC

Fig.4.Control schematic of UPQC

The ultimate purpose of UPQC control is to keep load

voltage on a constant level and be sinusoidal feature,

compensate load reactive power and harmonic and

ensure power supply has unity power factor

characteristic in all circumstances. As is the control

schematic of UPQC shown in Fig.4, series converter

works as a non-sinusoidal voltage source, outputting

compensation voltage uc which offsets grid voltage

distortion and fundamental deviation, accordingly it

ensures load voltage uL being rated sinusoidal voltage.

Meanwhile, shunt converter works as a non-sinusoidal

current source, outputting reactive power and harmonic

current Ic which offset reactive load power and load

harmonic current, accordingly it could make the

injected current Is be sinusoidal by compensating

reactive power and harmonic current. And the angle

between the injected voltage us and the injected current

is is zero at the moment, namely the power factor in grid side is unity.

IV. THE CONTROL STRATEGY OF UPQC

The control of UPQC mainly includes three aspects: the

control of series converter, the control of parallel

converter and the control of DC bus voltage. In control strategy diagram of series converter shown in Fig. 4.5,

usa, usb, usc are distribution network three-phase

voltage respectively. Through software phase-locked

loop, we could get t ω sin andt ω cos, which is essential

to dqrotary transformation. And then we perform dq

transform and dq inverse transform on three phase

standard voltage to make it in-phase with mains supply

voltage. Then subtract the distribution network


4

unbalance voltage from this standard voltage to get

three phase reference compensation voltage Compare

reference voltages with three phase actual compensation

voltage uca , ucb , ucc, and constitute closed loop

control by using a PI regulator. Specifically, in SPWM

mode three phase driving signal of series converter is

generated, consequently series converter is controlled to

output corresponding voltage vector to compensate.

The control of the forth leg of series converter is

aiming to keep load zero sequence voltage to zero, which function is implemented through closed loop

control with feed-forward control for voltage

constituted by a PI regulator. Symbols uLa, uLb, uLcin

Fig.4.5 represent three-phase load voltage respectively.

Fig. 5. Series converter control strategy diagram

As parallel converter control strategy diagram shown In

Fig. 4.6, perform dq transform on three phase load

current iLa, iLb, I Lc.

Then let the transformed current pass low-pass filter to

generate active component id and reactive component

iq. Perform dq inverse transform on these two

components to get fundamental component of three

phase load current. Subtract load current from this

standard current to get three phase reference compensation current. Compare the reference currents

with three phase actual compensation current ica, icb,

icc, and constitute closed loop control by using a PI

regulator. The same as the series converter control

mode, in SPWM mode three phase driving pulse signal

of parallel converter is generated, consequently parallel

converter is controlled to output corresponding current

vector to compensate. The control of the forth leg of

shunt converter is aiming to keep load zero sequence

current to zero, which function is implemented through

closed loop control constituted by a PI regulator. Symbols isa, isb, iscin Fig. 4.6 represent three-phase

power supply current respectively.

Parallel converter can realize reactive compensation by

controlling reactive component iq. If iq=0, then all

reactive power of the load is provided by parallel

converter.

Fig.6.Parallel converter control strategy diagram

DC side of UPQC, consisting of bi-directional DC-DC

converter based on super capacitor fast energy storage,

is able to solve problems of deeper voltage sag and

voltage instantaneous interruption. Fig. 4.7 illustrates

control strategy of DC/DC converter. After comparing

reference voltage Udef with DC bus voltage Ud, the

two voltages pass through closed loop PI control and

then compared by limited driver to generate PWM

signal. They could drive IGBT3 and IGBT4 in Fig. 4.2

respectively to implement the control of DC/DC

converter. And then use the output to maintain Ud at a stable level. The function of discharge circuit

comprising IGBT1 and IGBT2 could avoid over tension

happens to DC bus voltage Ud

Fig.7.DC/DC converter control strategy diagram

V. FUZZY LOGIC CONTROLLER

In FLC, basic control action is determined by a set of

linguistic rules. These rules are determined by the

system. Since the numerical variables are converted into

linguistic variables, mathematical modeling of the

system is not required in FC. The FLC comprises of

three parts: fuzzification, interference engine and defuzzification. The FC is characterized as; i. Seven

fuzzy sets for each input and output. ii. Triangular

membership functions for simplicity. iii. Fuzzification

using continuous universe of discourse. iv. Implication

using Mamdani‟s „min‟ operator. v. Defuzzification

using the „height‟ method.

Fig.8 Fuzzy Logic Controller

Fuzzification

Membership function values are assigned to the

linguistic variables, using seven fuzzy subsets: NB

(Negative Big), NM (Negative Medium), NS (Negative Small), ZE (Zero), PS (Positive Small), PM (Positive

Medium), and PB (Positive Big). The partition of fuzzy

subsets and the shape of membership function adapt the

shape up to appropriate system. The value of input error

E(k) and change in error CE(k) are normalized by an

input scaling factor shown in Fig. 8

Table1. Fuzzy Rules


5

In this system the input scaling factor has been designed

such that input values are between -1 and +1. The

triangular shape of the membership function of this

arrangement presumes that for any particular input there

is only one dominant fuzzy subset. The input error E(k)

for the FLC is given as

(a)

(b)

Fig. 9(a) & 4(b) Membership functions

Interference Method

Several composition methods such as Max–Min and

Max-Dot have been proposed in the literature. In this

paper Min method is used. The output membership

function of each rule is given by the minimum operator

and maximum operator. Table 1 shows rule base of the

FLC.

Defuzzification

As a plant usually requires a non-fuzzy value of control,

a defuzzification stage is needed. To compute the output

of the FLC, „height‟ method is used and the FLC output

modifies the control output. Further, the output of FLC

controls the switch in the inverter. In UPQC, the active

power, reactive power, terminal voltage of the line and

capacitor voltage are required to be maintained. In order

to control these parameters, they are sensed and

compared with the reference values. To achieve this, the

membership functions of FC are: error, change in error

and output as shown in Figs. 9(a), (b) In the present

work, for fuzzification, non-uniform fuzzifier has been

used. If the exact values of error and change in error are

small, they are divided conversely and if the values are

large, they are divided coarsely.

Where α is self-adjustable factor which can regulate the

whole operation. E is the error of the system, C is the

change in error and u is the control variable. A large value of error E indicates that given system is not in the

balanced state. If the system is unbalanced, the

controller should enlarge its control variables to balance

the system as early as possible. One the other hand,

small value of the error E indicates that the system is

near to balanced state. Overshoot plays an important

role in the system stability. Less overshoot is required

for system stability and in restraining oscillations. C in

(12) plays an important role, while the role of E is

diminished. The optimization is done by α. During the

process, it is assumed that neither the UPQC absorbs active power nor it supplies active power during normal

conditions. So the active power flowing through the

UPQC is assumed to be constant. The set of FC rules is

made using Fig. 4 is given in Table 1.

VI. MATLAB/SIMULINK RESULTS

Case 1: by using PI controller

Fig.10. Matlab/Simulink Model of UPQC Based on fast energy

storage


6

Fig.11.shows load voltage, DVR injected voltage and source voltage

Fig.12.shows source current, load current and compensating current

Fig.13.harmonic spectrum for source current

Case 2: by using fuzzy controller

Fig.14.Simulation results for load voltage, dvr injected voltage and

source voltage

Fig.15.Simulation result for source current and load current

Fig.16.harmonic spectrum for source current

VII. CONCLUSION UPQC using Fuzzy Controller (FC) has been

investigated for compensating reactive power and harmonics. It is clear from the simulation results that

the UPQC using FC is simple, and is based on sensing

the line currents only. The THD of the source current

using the proposed FLC is well below 5%, the harmonic

limit imposed by IEEE- 519 standard.

REFERENCES

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8

Simulation of Grid Connected PV System with Power Quality

Improvement Using Fuzzy Logic Controller

T.Ravi Kumar* , K.Sai Vasanthi**

*Associate Professor, Department of EEE, Geethanjali Institute Of Science & Technology, SPSR Nellore,

**PG Student, M.Tech (Power Electronics),Geethanjali Institute Of Science & Technology, SPSR Nellore,

Abstract— Due to continue using Fossil Fuel to

generate Electrical energy increasing air pollution,

global warming concerns, diminishing fossil fuels

and their increasing cost have made it necessary to

look towards Renewable Energy Sources (RES) as a

future energy solution. Renewable Energy Sources

demand increasingly at the distribution level due to

increase in load demand which utilize power

electronic converters. Due to the large use of power

electronic devices, disturbances occur on the

electrical supply network. These disturbances are

due to non-linear devices. These will produce

harmonics in the power system thereby causing

equipment overheating, damage devices, EMI

related problems etc. Active Power Filters (APF) is

used to compensate the current harmonics and load

unbalance. In this paper present the new control

strategy to control the inverter in such a way that to

maximum utilizes Renewable energy with grid. The

proposed system consists of RES connected to the dc

link of a grid-interfacing inverter. In this both load

are connected that is non-linear load as well as

unbalance load at distribution. Grid is connected to

step down transformer with reduce voltage level for

distribution side. For injecting Renewable energy to

grid inverter that is power electronic devices is used.

Power electronic devices produces the unwanted

harmonics to reduce this shunt active power filter is

used. The proposed control concept is implemented

with MATLAB/Simulink and the simulation results

are validated. EXTENSION: In extension Fuzzy

logic controller is implemented by using

MATLAB/SIMULATION software to improve the

power quality and the results are verified.

Key Words - distributed generation (DG), distribution

system, grid interconnection, power quality (PQ),

renewable energy, Point of common coupling (PCC).

I. INTRODUCTION

Electrical power is the most widely used source of

energy for our household’s equipments, industries and

work places. Population and industrial growth have led

to significant increases in power consumption over the past decades. Natural resources like petroleum, coal and

gas that have driven our industries, power plants and

vehicles for many decades are becoming depleted at

Avery fast rate. This is an important issue, which has

motivated nations across the world to think about

alternative forms of energy which utilize inexhaustible

natural resources. The combustion of conventional

fossil fuel across the globe has caused increased level of

environmental pollution .Several international

conventions and forums have been set up to address and

resolve the issue of climate change. These forums have motivated countries to form national energy policies

dedicated to pollution control, energy conservation,

energy efficiency, development of alternative and clean

sources of energy. Renewable energy like solar, wind,

and tidal currents of oceans is sustainable, inexhaustible

and environmentally friendly clean energy. Due to all

these factors, wind power generation has attracted great

interest in recent years. Undoubtedly, wind power is

today's most rapidly growing renewable energy source.

Distributed generation (DG) is termed as the integration of Renewable energy source (RES) at the distribution

level. The number of distributed generation (DG) units,

including both renewable and non-renewable sources,

for small rural communities not connected to the grid

and for small power resources connected to the utility

network has grown in the last years. The integration of

renewable energy systems (RESs) in smart grids (SGs)

is a challenging task, mainly due to the intermittent and

unpredictable nature of the sources, typically wind or

sun. So for the reliable operation of the system,

continuous control is needed. This can be obtained by the help of digital control and power electronic devices

which may improve the power quality of the system at

the PCC. The quality of power in the system is mainly

affected by the harmonic current produced by the non-

linear loads and power electronic based instruments

[1],[2].

In the distributed system, the intermittent RES is

connected using current controlled voltage source

inverters. New control strategies for grid connected inverters with PQ solution have been proposed. In [3]

an inverter operates as active inductor at a certain

frequency to absorb the harmonic current. The control


9

performance may be decreased because of the

complexity in exact calculation of network impedance

in real time. In [4] a cooperative control of multiple

active filters based on voltage detection for harmonic

damping throughout a power distribution system is

proposed. In [5], a control strategy for renewable interfacing inverter based on p-q theory is proposed.

This strategy includes both load and inverter current

sensing which is required to compensate the load

current harmonics. Voltage harmonics which is caused

by non-linear load current harmonics can create serious

PQ problem in the power system network. To

compensate this, Active power filters (APF) are

extensively which may result in additional hardware

cost. This papersuggests how to include the APF in the

conventional inverter interfacing renewable with the

grid, without any additional hardware cost.

In this paper that the grid-interfacing inverter can

effectively be utilized to perform the following four

important functions: 1) transfer of active power

harvested from the renewable resource (wind); 2) load

reactive power demand support; 3) current harmonics

compensation at PCC; and 4) current unbalance and

neutral current compensation in case of 3-phase 4-wire

system. All the four objectives can be accomplished

either individually or simultaneously with adequate

control of grid-interfacing inverter. So without additional hardware cost the PQ constraints at the PCC

can therefore be strictly maintained within the utility

standards.

three phase four leg VSI is modeled in Simulink by

using IGBT. The driving voltage across the inductance

determine the maximum di/dt that can be achieved by

the filter. A large valve of inductance is better for

isolation from the power system and protection from

transient distribution it also limit the ability of the active filter to cancel higher order harmonics.

Fig. 1.Schematic of proposed renewable based distributed generation

system.

II. SYSTEM DESCRIPTION

The proposed system consists of RES connected to

thedc link of a grid-interfacing inverter as shown in Fig.

1. It isshows that both load are connected that is non-

linear load aswell as unbalance load at distribution. Grid

is connected tostep down transformer with reduce

voltage level fordistribution side as shown in fig. 1. For

injecting Renewableenergy to grid inverter that is power

electronic devices isused. Power electronic devices

produces the unwantedharmonics to reduce this shunt

active power filter is used.Shunt active power filter is

used to compensate load currentharmonics by injecting equal but opposite compensatingcurrent.

In this paper three phase four wire voltage

sourcecurrent controlled inverter is used. Generally

three wireinverter is used but in this fourth terminal is

used tocompensate the neutral current.A voltage source

inverter is convert renewable DCenergy into Ac with

required magnitude, phase angle andfrequency. It also

converts the DC voltage across storagedevices into a set

of three phase AC output voltages. It isalso capable to

generate or absorbs reactive power. If theoutput voltage

of the VSC is greater than AC bus terminalvoltages, is

said to be in capacitive mode. So, it willcompensate the

reactive power through AC system. Thetype of power switch used is an IGBT in anti-parallel with adiode. The

III. CONTROL STRATEGY

A. DC-Link Voltage and Power Control Operation

Due to the intermittent nature of RES, thegenerated

power is of variable nature. The dc-linkplays an

important role in transferring this variablepower from

renewable energy source to the grid. RESare

represented as current sources connected to thedc-link

of a grid-interfacing inverter. Fig. 1 shows thesystematic representation of power transfer from

therenewable energy resources to the grid via the

dclink. The dc-capacitor decoupled the RES from

gridand allows the independent control of inverter

oneither side of dc link. P1 to P8 switching signal of

inverter where P 7 and P8 are multiplied with constant

zero to compensate the neutral current.

B. Control of Grid Interfacing Inverter

The control diagram of grid- interfacing inverter for a 3-

phase 4-wire system is shown in Fig. 2. To compensate

the neutral current of load, a fourth leg is provided to

the inverter. The proposed approach is mainly

concerned about the regulation of power at PCC during three conditions like, when 1) PRES = 0; 2) PRES <

total power (PL); and 3) PRES > PL. During the power

management operation, the inverter is controlled in such

a way that it always draws/ supplies fundamental active


10

power from/ to the grid. If the load connected to the

PCC is non-linear or unbalanced or the combination of

both, the given control approach also compensates the

harmonics, unbalance, and neutral current. By the

control, duty ratio of inverter switches are varied in a

power cycle in order to get the combination of load and

inverter injected power to be appearing as balanced

resistive load to the grid

Fig. 2. Block diagram representation of grid-interfacing inverter control.

The exchange of active power in between renewable

source and grid can be obtained from the regulation of

dc-link voltage.Thus the output of dc-link voltage

regulator results in an active current (Im). The

multiplication of this active current component (Im) with unity grid voltage vector templates (Ua,Ub, and Uc

) generates the reference grid currents (I*a,I*b , and

I*c) for the control process. The reference grid neutral

current (I*n) is set to zero, being the instantaneous sum

of balanced grid currents. Phase locked loop (PLL) is

used to generate unity vector template from which the

grid synchronizing angle (0) is obtained.

(1)

(2)

(3)

The actual dc-link voltage (VDC) is sensed and passed

through a first-order low pass filter (LPF) toeliminate

the presence of switching ripples on the dclink voltage

and in the generated reference currentsignals. The

difference of this filtered dc-link voltage and reference

dc-link voltage (VDC*) is given to a discrete-PI

regulator to maintain a constant dc-link voltage under

varying generation and load conditions.

The dc-link voltage error VDCerr(N) at nth

samplinginstant is given as:

(4)

The output of discrete-PI regulator at nth sampling

instant is expressed as

(5)

Where KPVdcand KIVdc are proportionaland integral gains of dc-voltage regulator. Theinstantaneous values of reference three phase gridcurrents are computed as

(6)

(7)

(8)


11

The neutral current, present if any, due to the loads

connected to the neutral conductor should be

compensated by forth leg of grid-interfacing inverter

and thus should not be drawn from the grid. In other

words, the reference current for the grid neutralcurrent

is considered as zero and can be expressed as:

(8)

The reference grid currents (IA*, IB*, IC* and IN) are compared with actual grid currents (IA, IB, IC and IN) to compute the current errors as:

(9)

(10)

(11)

(12)

These current errors are given to hysteresis

currentcontroller. The hysteresis controller then

generates the switching pulses (P1, P2, P3, P4, P5, P6,

P7, and P8) for the gate drives of grid-interfacing

inverter.

The switching pattern of each IGBT insideinverter can

be formulated on the basis of errorbetween actual and

reference current of inverter, which can be explained as:

If IInvA< (IInvA*- hB), then upper switch will be OFF (P1=0) and lower switch S4 will be ON (P4=1) in the phase “A” leg of inverter.

If IInvA> (IInvA*-hB), then upper switch will be ON (P1=1) and lower switch S4 will be OFF (P4=0) in the phase “a” leg of inverter.

Where hb is the width of hysteresis band. Similarly switching pulses are derived for other three leg.

IV. INTRODUCTION TO FUZZY LOGIC

CONTROLLER

A new language was developed to describe the fuzzy

properties of reality, which are very difficult and

sometime even impossible to be described using

conventional methods. Fuzzy set theory has been widely used in the control area with some application to

dc-to-dc converter system. A simple fuzzy logic control

is built up by a group of rules based on the human

knowledge of system behavior. Matlab/Simulink

simulation model is built to study the dynamic behavior

of dc-to-dc converter and performance of proposed

controllers. Furthermore, design of fuzzy logic

controller can provide desirable both small signal and

large signal dynamic performance at same time, which

is not possible with linear control technique. Thus,

fuzzy logic controller has been potential ability to

improve the robustness of dc-to-dc converters. The

basic scheme of a fuzzy logic controller is shown in Fig 5 and consists of four principal components such as: a

fuzzy fication interface, which converts input data into

suitable linguistic values; a knowledge base, which

consists of a data base with the necessary linguistic

definitions and the control rule set; a decision-making

logic which, simulating a human decision process, infer

the fuzzy control action from the knowledge of the

control rules and linguistic variable definitions; a de-

fuzzification interface which yields non fuzzy control

action from an inferred fuzzy control action [10].

Fig.3. General structure of the fuzzy logic controller on closed-loop

system

The fuzzy control systems are based on expert

knowledge that converts the human linguistic concepts

into an automatic control strategy without any

complicated mathematical model [10]. Simulation is

performed in buck converter to verify the proposed

fuzzy logic controllers.

Fig.4. Block diagram of the Fuzzy Logic Controller (FLC) for dc-dc

converters

Fuzzy Logic Membership Functions:

The dc-dc converter is a nonlinear function of the duty cycle because of the small signal model and its control

method was applied to the control of boost converters.

Fuzzy controllers do not require an exact mathematical

model. Instead, they are designed based on general

knowledge of the plant. Fuzzy controllers are designed

to adapt to varying operating points. Fuzzy Logic


12

Controller is designed to control the output of boost dc-

dc converter using Mamdani style fuzzy inference

system. Two input variables, error (e) and change of

error (de) are used in this fuzzy logic system. The single

output variable (u) is duty cycle of PWM output.

Fig. 5.The Membership Function plots of error

Fig.6. The Membership Function plots of change error

Fig.7. The Membership Function plots

Fuzzy Logic Rules:

The objective of this dissertation is to control the output

voltage of the boost converter. The error and change of

error of the output voltage will be the inputs of fuzzy

logic controller. These 2 inputs are divided into five

groups; NB: Negative Big, NS: Negative Small, ZO:

Zero Area, PS: Positive small and PB: Positive Big and

its parameter [10]. These fuzzy control rules for error

and change of error can be referred in the table that is shown in Table II as per below:

Table II

Table rules for error and change of error

V. SIMULATION RESULTS

For the simulation studies to verify the proposed control

approach to achieve multi-objectives for grid interfaced

DG systemsconnected to a 3-phase 4-wire network is carried out using MATLAB/Simulink. To achieve

balanced sinusoidal grid currents at unity power factor

(UPF) despite of highly unbalanced nonlinear load at

PCC under varying renewable generating conditions, a

4- leg current controlled voltage source inverter is

actively controlled. A RES with variable output power

is connected on the dc-link of grid-interfacing inverter.

On the PCC, an unbalanced 3-phase 4-wire nonlinear

load, whose unbalance, harmonics, and reactivepower

need to be compensated, is connected.

Case 1: By using PI controller

Fig.8.simulink circuit for proposed system


13

Fig.9. simulation results for (a) source voltage (b) source current (c)

load current (d) compensated currents

Fig.10. simulation results for source power factor

Fig.12. FFT analysis for source current by using PI controller

Case 2: By using fuzzy controller

Fig.13. simulation results for (a) source voltage (b) source current (c)

load current (d) compensated currents

Fig.14. simulation results for source power factor

Fig.15. FFT analysis for source current by using fuzzy controller

V.CONCLUSION

This paper has introduced a new control of an existing

grid interfacing inverter to improve the power quality at

PCC for a 3-phase 4-WireDGsystem. The ability of the

grid-interfacing inverter to be effectively used for the

power conditioning without affecting itsnormal operation of real power transfer is also shown. The grid-

interfacing inverter with the proposed technique can be

utilized to:

i) inject real power generated from RES to the grid,

and/or,

ii) operate as a shunt Active Power Filter (APF).

This approach helps to improve the quality of power at

PCC without the need of additional power conditioning

equipment. Extensive MATLAB/Simulink results have


14

validated the proposed approach and have shown that

the grid-interfacing inverter canbe utilized as a multi-

function device. The simulation demonstrates that the

PQ enhancement can be achieved under three different

scenarios: 1) PRES = 0; 2) PRES <PLoad; and 3) PRES

>PLoad. The current unbalance, current harmonics and load reactive power, due to unbalanced and non-linear

load connected to the PCC, are compensated effectively

such that the grid side currents are always maintained as

balanced and sinusoidal at unity power factor. The

fourth leg of inverter prevents the load neutral current

from flowing into the grid side by compensating it

locally. When the power generated from RES is more

than the total load powerdemand, the grid-interfacing

inverter with the proposed control approach not only

fulfills the total load active and reactive power demand

(with harmonic compensation) but also delivers the

excess generated sinusoidal active power to the grid at unity power factor.

[7] J. M. Carrasco, L. G. Franquelo, J. T. Bialasiewicz, E. Galván, R.

C. P. Guisado, M. Á. M. Prats, J. I. León, and N. M. Alfonso,

“Powerelectronic systems for the grid integration of renewable energy

sources: A survey,” IEEE Trans. Ind. Electron., vol. 53, no. 4, pp.

1002–1016, Aug. 2006.

REFERENCES [1] J. M. Guerrero, L. G. de Vicuna, J. Matas, M. Castilla, and J.

Miret, “A wireless controller to enhance dynamic performance of

parallel inverters in distributed generation systems,” IEEE Trans.

Power Electron., vol. 19, no. 5, pp. 1205–1213, Sep. 2004.

[2] J. H. R. Enslin and P. J. M. Heskes, “Harmonic interaction

between a large number of distributed power inverters and the

distribution network,” IEEE Trans. Power Electron., vol. 19, no. 6, pp.

1586–1593, Nov. 2004.

[3] U. Borup, F. Blaabjerg, and P. N. Enjeti, “Sharing of nonlinear

load in parallel-connected three-phase converters,” IEEE Trans. Ind.

Appl., vol. 37, no. 6, pp. 1817–1823, Nov./Dec. 2001.

[4] P. Jintakosonwit, H. Fujita, H. Akagi, and S. Ogasawara,

“Implementation and performance of cooperative control of shunt

active filters for harmonic damping throughout a power distribution

system,” IEEE Trans. Ind. Appl., vol. 39, no. 2, pp. 556– 564,

Mar./Apr. 2003.

[5] J. P. Pinto, R. Pregitzer, L. F. C. Monteiro, and J. L. Afonso, “3-

phase 4-wire shunt active power filter with renewable energy

interface,” presented at the Conf. IEEE Rnewable Energy & Power

Quality, Seville, Spain, 2007.

[6] F. Blaabjerg, R. Teodorescu, M. Liserre, and A. V. Timbus,

“Overview of control and grid synchronization for distributed power

generation systems,” IEEE Trans. Ind. Electron., vol. 53, no. 5, pp.

1398–1409, Oct. 2006.


15

Low Power Multi-Bit Flip-Flops Design for VLSI Applications

Yeturi Mallikarjuna* , Chiranjeevi Thokala ** *Asst.Professor, Geethanjali Institute of Science and Technology, Nellore.

**Asst.Professor, Geethanjali Institute of Science and Technology, Nellore.

ABSTRACT-

The utilization of power has turned into a

smoldering issue in current VLSI design. Power

consumption can be lessened by substituting some

flip-flops with less multi-bit flip-flops. Multi-bit flip-

flops are one of the strategies for reducing the clock

power consumption. This project concentrates on

diminishment of clock force utilizing multi-bit flip-

flops by clock synchronization. Diminishment of the clock power consumption with two single bit flip-

flops are synchronized with single clock pulse.

Uniting single bit flip-flops into one multi-bit flip-

flop evades duplicate inverters, brings down the

aggregate clock power utilization which lessens the

total area. A mixture table is fabricated to acquire a

multi-bit flip-flop which can store the flip-flops that

can be consolidated. This task concentrates on D

flip-flop which builds the loading of the clock

signal. QCL adder is utilized as an application for

multi-bit flip-flop. Highest ‘1’ bit finding algorithm

is utilized to discover the highest 1 bit from the yield of QCL adder. This calculation checks the yield of

QCL adder in each one cycle.

Keywords: QCL, SOC, Mbffs, merging, power

reduction, clock buffer.

I.INTRODUCTION

Because of the prominence of compact electronic

items, low power framework has pulled in more

consideration lately. As technology advances, a

system-on-a-chip (SOC) configuration can contain more parts that prompt a higher power density. This

makes power dissipation achieve the cutoff points of

what packaging, cooling or other framework can

help. Decreasing the power consumption can upgrade

battery life as well as can evade the overheating

issue, which would build the level of trouble of

packaging or cooling consequently, the thought of

power consumption in complex SOCs has turned into

a huge test to designers. In addition, in advanced

VLSI plans, power consumed by clocking has taken a

significant piece of the entire plan particularly for

those designs using deeply scaled CMOS technologies. In this way, a few strategies have been

proposed to decrease the power consumption of

clocking.

For a given plan that the areas of the cells

have been firm, the power consumed by clocking can

be decreased further by substituting a few flip-flops

with multi-bit flip-flops. At clock tree synthesis, less

number of flip-flops implies reduced number of clock sinks. Therefore, the resulting clock system uses

reduced power consumption and utilizes less routing

resource.

Furthermore, smaller flip-flops are

substituted by bigger multi-bit flip-flops; gadget

varieties in the relating circuit can be orderly

reduced. As the CMOS technology progresses, the

driving capacity of an inverter-based clock buffer

increments fundamentally. The ability to drive a

clock buffer can be assessed by the quantity of least

measured inverters that it can drive on a given rising

or falling time. Due to this sensation, a few flip-flops

can impart a common clock buffer to evade unnecessary waste of power.

Fig. 1 shows the block diagrams of 1- and 2-

bit flip-flops. If we replace the two 1-bit flip-flops as

shown in Fig. 1(a) by the 2-bit flip-flop as shown in

Fig. 1(b), the total power consumption can be

reduced because the two 1-bit flip-flops can share the

same clock buffer.

Fig.1: Example of merging two 1-bit flip-

flops into one 2-bit flip-flop.(a) Two 1-bit flip-flops

(before merging). (b) 2-bit flip-flop (after merging)

In any case, the areas of some flip-flops

would be changed after this substitution, and subsequently the wire lengths of nets connecting pins


16

to a flip-flop are additionally changed. To abstain

from damaging the timing imperatives, we confine

that the wire lengths of nets uniting pins to a flip-flop

can't be longer than detailed values after this

procedure. On the other hand, to ensure that another

flip-flop can be put inside the desired region, we

likewise need to consider the area capacity of the

region.

The power plays a significant part in any

design one may need to focus on power reduction

strategies. To diminish the power consumption, a lot

of low-power plan procedures have been presented,

for example, clock gating, power gating making

multi-supply-voltage plans, dynamic voltage per frequency scaling, and minimizing clock system.

Among these procedures, minimizing and fusing the

clock system is essential in reducing power

consumption of a Soc (System on Chip). By

diminishing the power in circuit design it naturally

reduces the many-sided quality and wire length. In

this manner, distinctive systems have been proposed

[2], [3] to design a reduced power consumption

design.

The power had been expanded for diverse

stages are static and dynamic power. In dynamic power, change in input signal at distinctive rationale

level will result in exchanging and short out force in

the configuration. In static force, it doesn't have any

impact of level change in information and yield. The

Multi-bit Flip-flop (MBFF) is a successful power

reduction procedure. It is utilized to decrease the

quantity of Flip Flop away stage. Sending numerous

bits of information with single FF utilizing single

clock pulse is called MBFF. The idea of MBFF is

presented in adder application which is utilized to

diminish the quantity of FFs which are not

empowered in the circuit outline. Mbffs have advantage over SBFF as more modest outline zone,

controllable clock, less delay on clock system and

effective use of routing resources.

The working of multi-bit flip flop is same as

single-bit flip-flop, at whatever point the clock gets

dynamic state flip flop latches all data to yield. For

idle state the flip flop holds the information. The

fundamental structure of multi-bit flip failure is given

in Fig. 1, it demonstrates that as opposed to utilizing

single bit FF we can supplant into multi bit FF as 2-

bit FF, 4-bit FF and 8-bit FF are produced as a different assignment. At the point when will the

obliged bit of capacity FF is required the specific

errand is, no doubt brought in active region and

others will be in-active (sleep mode) region.

In the proposed work it takes after that it is

utilized to store the quantity of bits that are

empowering specifically flip-flop utilizing single

check and others are in sleep mode. It doesn't devour

power for other flip-flop which is not empowered

during the storage stage.

Fig. 2 Block diagram of MBFF

The multi smaller FF is supplanted by larger

MBFF utilizing the less clock source; all the more

over gadget varieties in the relating circuit can be

successfully reduced. The FF can be fused with the

assistance of combinational table which will be

powerfully empowered built in light of the number

of bit capacity necessity with force thought. The

FF going to be united can be utilized for memory

shows. By decreasing the quantity of Ffs, the clock

sinks area and clock dynamic power have been viably

diminished.

II. EXISTING METHOD

Ya-Ting Shyu et al [1] had utilized the

numerous single bit flip- flop are supplanted by

multi bit flip-flop. Because of this force is expanded

and intricacy in configuration. The procedure [4]

used to diminish control in the post-arrangement

stage. In this work a chart based method is utilized

within request to decrease the clock power. The flip-

lemon is spoken to for every hub in the chart. The

flip-failure relating to the hubs in an m-inner circle

can be supplanted by an m-bit flip lemon. The

calculation is utilized to discover m-coteries in a chart are extension and-bound and backtracking

calculation. An alternate calculation is additionally

used to discover the most extreme autonomous

gathering of factions is ravenous heuristic

calculation. In this work there is a probability of

discovering outlandish mix of flip tumble in a

library. Because of this it may prompt the wastage

of time and more number of Ffs is utilized within


17

every hub.

III. PROPOSED METHOD

In the past technique [1] the measure of time

is wasted by discovering the impossible

combination of FF furthermore numerous single bit

FF is utilized. This may expand the complicated

nature. So as to decrease the power MBFF idea is

utilized. it portrays that need to recognize a legal

placement region for every FF. In first stage, the

reasonable placement regions of a FF connected

with diverse pins are discovered focused around the

timing stipulations characterized on the pins. At that

point, the legal placement region of the FF can be obtained by overlapped area of these regions.

Nonetheless, these regions are fit as a

diamond shape; it is not simple to recognize the

overlapped region. Accordingly, the overlapped

zone can be recognized all the more effectively in

the event that it can change the coordinate

arrangement of cells to get rectangular regions. In

the second stage, it might want to manufacture a

combination table, which characterizes all

combinations of FF keeping in mind the end goal to get another multi-bit Ffs given by the library.

Fig.3 Flow-chart of merging flip-flop

The flip-flops can be united with the

assistance of the table. After the legal placement

regions of flip-flops are discovered and the

combination table is fabricated, we can utilize them

to merge flip-flops. To accelerate our project, we

will isolate a chip into a few canisters and

consolidation flip-flops in a neighborhood bin.

However, the flip-flops in diverse bins

might be mergeable. In this way, we need to

consolidate a few bins into a bigger bin and repeat

this venture until no flip-flop can be fused any

longer. In this area, we would detail each one phase

of our technique. In the first subsection, we

demonstrate a basic equation to change the original

coordination framework into another one so that a

legal placement region for each one flip-flop can be

distinguished all the more effectively. The second

subsection shows the flow of building the combination table. At long last, the substitutions of

flip-flops will be depicted in the last subsection.

A.TRANSFORMATION OF PLACEMENT SPACE

The equations used to transform coordinate

system are shown in (1) and (2). Suppose the

location of a point in the original coordinate system

is denoted by (x, y). After coordinate

transformation, the new coordinate is denoted by

(x‟, y‟). In the original transformed equations,

each value needs to be divided by the square root of 2, which would induce a longer computation time.

Since we only need to know the relative

locations of flip-flops, such computation are

ignored in our method. Thus, we use x” and y”, to

denote the coordinates of transformed locations.

B.COMBINATION TABLE

A few flip-flops can be replaced by multi-

bit flip-flop. In this proposed methodology, the

combination table is assemble, which is utilized to

get achievable flip-flops before substitution. This

makes to use for recognizing the specific flip-flop

which will be empowered in active region and

cannot be covered. Utilizing this combination table,

the flip-flop can be bit by bit replaced and this makes

lessens the multifaceted nature of the configuration.

Since one and only combination of flip-flop need to

be considered in each one time, the clock signal can be successfully decreased.

IV APPLICATION DEVELOPED

The 1-bit, 2-bit, 4-bit and 8-bit Ffs are

created as partitioned assignment as demonstrated

in Fig. 3. The two inputs zone and b, is spoken to as

input1 and b is spoken to as input2. These two


18

inputs are included and put away in the FF

updating. After that it checks the bits that are

accessible in the area. The chosen Ffs are used

when it is empowered and yield is shown. This

makes decreases the power and delay in the design.

The low power affects in the expense, size, weight,

execution and unwavering quality.

The multiplier application can likewise be

carried out in this proposed work. As opposed to

including the bits, reproducing is possible and it is

put away in the specific enabled flip-flop. For case,

accept that a library just helps two sorts of flip- flops whose bit widths are 1 and 4 methods the

specific flip-flop will be chosen and it will be

empowered in the area and will be in sleep mode

(in-active region).

The D-FF is utilized as a part of this

proposed work. It gives synchronous information

exchange and utilized for capacity reason. In any

case, a dissimilar latch element, a FF just duplicates

the information from the data pin to the yield once

for every clock period and does not permit various

multiple logic values to be passed in a clock cycle. Information is exchanged at either the rising or the

falling clock edge, contingent upon the flip-flop

setup. Unlike latch, a FF is not level-sensitive, yet

rather edge-activated. As it were, information gets

put away into a FF just at the dynamic edge of the

clock. The 16 bit FF can likewise be produced as

indicated in Fig. 4; it diminishes the power and

memory gadgets contrasted with single bit flip

lemon. By and large, the snake libraries comprises

AND, XOR as well as dominant part doors. The

register banks are utilized to store the bit when it is enabled.

Fig. 4 Block diagram for MBFF used for

application module

The D Flip-flop is the edge-triggered variation of the transparent latch. On the rising (typically, albeit negative edge triggering is possible) edge of the clock, this defer is given the estimation of the D data at that minute. This defer can be just change at the clock edge, and if the data changes at different times, the yield will be unaffected.

D flip-failures are by a wide margin the most well-known sort of flip-flops and a few gadgets are made altogether from D flip-flops. They are regularly utilized for shift- registers and input synchronization.

Objectives

1. Reduce the power consumption.

2. To reduce to the area.

3. To reduce the delay and power of a clock network.

4. To control clock skew because of common clock signal.

The above objectives can be achieved by merging several flip-flops and synchronizing with clock signals.

Quandary Statement

The following quandary statement has been

identified:

1) Several Flip-flops needs a separate clock signal, hence Power consumption, is high.

2) Since several flip-flops needs a separate clock signal area consumed is also high.

V. BLOCK DIAGRAM AND ITS

MODULES

This deals with the block diagram of the proposed method and its modules.

Block Diagram

The block diagram of the Application of Multi-bit flip-flop using QCL Adder as shown in figure 4.Two inputs are given to QCL adder. QCL adder are developed by Majority Logic XOR, AND, OR gate. The output of QCL adder is fed to highest bit "1‟ finding Algorithm. This Algorithm finds the number of bits and the combination table is built in order to merge the Flip-flops and it is stored in the Variable register banks.

Modules

This focuses on three different types of modules which are explained below.


19

1) Devise And Analysis Of Multi-Bit Flip-

Flops

2) Devise Of Memory Device Using Multi-Bit Flip Flop

3) Devise and analysis of the application module

Devise and Analysis of Multi-Bit Flip-Flops

This module is utilized to decrease the power utilization by substituting some flip flop with less Multi-Bit flip flops. We are utilizing the Multi-Bit flip flop rather than more single bit flip flop to expand the clock synchronization. This will diminish the unnecessary force wastage through the utilization of numerous clock sinks.

Devise of Memory Device Using Multi-Bit Flip Flop

This is the application module to be developed. The memory designed by mainly using the multi-bit flip flops. In this, power consumption of memory devices is reduced compare to the single bit memory.

Analysis and Devise of the application Module

We are integrating all the sub modules and output signals are simulated.

VI. RESULTS

For the application module given above

section was simulated. For adder, when clock leading

edge input is 0 and the trailing edge input is 1, reset input is 1, input for a is 0000000 and the input for b

is 01111111.The output is 01111111 as shown in the

Fig below.

For example if the a input is 0000011 and if

the b input is 0000011 the output will be 00000110

and the clock signal is given to the flip-flop that is

required to show the output. The number of one’s is

two, so the two bit register was enabled the

remaining flip-flops are in deactivation mode. By this

we can reduce the power that is required for the

operation in the system on chip.

COMPARISION TABLE

This table shows the delay and the power

consumption by the clock utilization. The delay and

clock power was almost same for all the designed

flip-flops.

1 bit 0.487 0.017

4 bit 0.487 0.018

8 bit 0.487 0.018

Fig. 5: shows simulation output of adder

VII. CONCLUSION

This project has proposed a methodology for flip-

flop substitution for power reduction in digital

integrated circuit design. The system of flip-flop

substitutions is relying upon the combination table,

which records the connections among the flip-flop

types. By the rules of substitutions from the

combination table, the incomprehensible combinations of flip-failures won't be viewed as that

reductions execution time. Other than power

reduction, the destination of minimizing the

aggregate wire length likewise considered to the

expense capacity. The verilog source code had

produced for the application module as indicated in

above areas and simulated utilizing the Isim test

system. The single bit and multibit flip-flops source

code additionally planned and reproduced and

combined utilizing Xilinx ISE Design suite. This

methodology can be appropriate for any circuit

comprising of various flip-flops like counters registers.

VIII. REFERENCES

[1] Ya-Ting Shyu, Jai-Ming Lin, Chun-Po

FF size Delay(ps) Clock Power(w)


20

Huang, Cheng-Wu Lin, Ying- Zu Lin, and Soon-

Jyh Chang, 2013, „Effective and efficient approach

for power reduction by using Multi-bit Flip-flops

in IEEE transactions on VLSI, vol. 21, no. 4.

[2] H. Kawagachi and T. Sakurai, 1997, „A

reduced clock-swing flip-flop (RCSFF) for 63%

clock power reduction , in VLSI Circuits Dig. Tech.

Papers Symp., pp. 97–98. [3] Y. Cheon, P.-H. Ho, A. B. Kahng, S. Reda, and

Q. Wang, 2005, Power-aware placement , in Proc.

Design Autom. Conf., pp. 795–800.

[4] Y.-T. Chang, C.-C. Hsu, P.-H. Lin, Y.-W.

Tsai and S.-F. Chen, 2010, Post-placement power

optimization with multi-bit flip- flops , in Proc.

IEEE/ACM Comput.-Aided Design Int. Conf.,

SanJose, CA, pp. 218–223.

[5] P. Gronowski, W. J. Bowhill, R. P. Preston,

M. K. Gowan, and R.L. Allmon, “High-

performance microprocessor design,” IEEE J. Solid-State Circuits, vol. 33, no. 5, pp. 676–686, May

1998.

[6] L. Chen, A. Hung, H.-M. Chen, E. Y.-W.

Tsai, S.-H. Chen, M.-H. Ku, and C.-C.Chen,

“Using multi-bit flip-flop for clock power saving

by Design Compiler,” in Proc. Synopsys User

Group (SNUG), 2010.

[7] J.-T. Yan and Z.-W. Chen, “Construction of

constrained multi-bit flip-flops for clock power

reduction,” in Proc. ICGCS, pp. 675–678, 2010. [8] S.-H. Wang, Y.-Y. Liang, T.-Y. Kuo, and W.-

K. Mak, “Power-driven flip-flop merging and

relocation,” in Proc. ISPD, pp. 107–114, 2011.

[9] J. M. Rabaey, A. Chandrakasan, and B.

Nikolic, 2003, Digital Integrated Circuits: A

Design Perspective, 2nd ed. Upper Saddle River,

NJ: Prentice-Hall

[10] Y. Kretchmer, 2001, “Using multi-bit

register inference to save area and power,” EE

Times Asia.


21

Employee Retention and its Improvement Strategies

Sd. Ghousul Asvia Begum, M Com, MBA, M Phil., PGDHRM, PGDCA,AP SET

Asst. Professor, Geethanjali Institute of Science and Technology, Nellore.

ABSTRACT

Every organization invests time and money to

groom a new entry, make a corporate ready

material and bring at parity with the existing

employees. Employee retention as relating to the

efforts by which employers attempt to retain

employees in their workforce. Employee retention

can be represented by a simple statistic (for

example, a retention rate of 80% usually indicates

that an organization kept 80% of its employees in

a given period). In this sense, retention becomes

the strategies rather than the outcome. Employee

retention takes into account the various measures

taken so that an individual stays in an

organization for the maximum period of time. A

distinction should be drawn between low-

performing employees and top performers, and

efforts to retain employees should be targeted at

valuable, contributing employees. The

organization is completely at loss when the

employees leave their job once they are fully

trained.

Key words: Employee turnover, Employee-

manager relationship, Morale, Motivation,

Organizational behavior

I. INTRODUCTION

Employee retention refers to the ability of

an organization to retain its employees. It involves

various policies and practices which let the

employees stick to an organization for a longer

period of time. Employee turnover is a symptom of

deeper issues that have not been resolved, which

may include low employee morale, absence of a

clear career path, lack of recognition, poor employee-manager relationships or many other

issues. A lack of satisfaction and commitment to

the organization can also cause an employee to

withdraw and begin looking for other opportunities.

Pay does not always play as large a role in inducing

turnover as is typically believed. Employee

retention techniques go a long way in motivating

the employees for them to enjoy their work and

avoid changing jobs frequently.

Employee retention techniques go a long

way in motivating the employees for them to enjoy

their work and avoid changing jobs frequently.

Employers can improve retention rates and

decrease the associated costs of high turnover.

Employers can seek "positive turnover" whereby

they aim to maintain only those employees whom

they consider to be high performers.

II. WHY DO EMPLOYEES/LEAVE?

The Research says that most of the

employees leave an organization out of frustration

and constant friction with their superiors or other

team members. In some cases low salary, lack of

growth prospects and motivation compel an

employee to look for a change. The management

must try its level best to retain those employees

who are really important for the system and are known to be effective contributors.

It is the responsibility of the line managers as well

as the management to ensure that the employees are

satisfied with their roles and responsibilities and

the job is offering them a new challenge and

learning every day.

Let us understand the concept of employee

retention with the help of an example:

Misha was a talented employee who delivered her

best and completed all her work within the desired

time frame. Her work lacked errors and was always found to be innovative and thought provoking. She

never interfered in anybody else’s work and stayed

away from unnecessary gossips and rumours. She

avoided hang around at the workplace, was serious

about her work and no doubts her performance was

always appreciable. Greg, her immediate boss

never really liked Misha and considered her as his

biggest threat at the workplace. He left no stone

unturned to insult and demotivates Misha. Soon,

Misha got fed up with Greg and decided to move

on.

Situation 1 - The HR did not make any efforts to retain Misha and accepted her resignation.

Situation 2 - The HR immediately intervened and

discussed the several issues which prompted Misha

to think for a change. They tried their level best to

convince Misha and even appointed a new boss to make the things better for her.

Situation 1 would most likely leave the

organization in the roll. It is not easy to find an

employee who gels well with the system and

understands the work. Hiring an employee, training

him and making him fit to work in an organization

incur huge costs and thus sincere efforts must be

made to retain the employee. Every problem has a


22

solution and the management must probe into the

exact reasons of an employee’s displeasure.

Employees sticking to an organization for a longer

time tend to know the organization better and

develop a feeling of attachment towards it. The

employees who stay for a longer duration are

familiar with the company policies, guidelines as

well as rules and regulations and thus can contribute more effectively than individuals who

come and go.

Most business owners and managers think

retention is based on compensation issues--wage

and salary levels, incentives, and golden handcuffs-

-when in reality the drivers go much deeper into the

human psyche to the actions and attitudes that

make employees feel successful, secure and

appreciated.

III. SOUND RETENTION

STRATEGY

As a result, a sound retention strategy

should focus on and tactically address four key

elements--performance, communication, loyalty

and competitive advantage.

1. Performance. The benefit of having measurable

objectives for employees is fairly obvious to most business owners and managers, but this perception

usually stops short of relating performance metrics

to employee retention. When people sense their

actions are fulfilling this desire, they begin to

develop a sense of belonging and a feeling that

your company is their company. Clear, achievable

objectives that measure personal, team and

company performance provide the feedback

employees need to confirm they're making valuable

contributions and accomplishing desirable goals.

2. Communication. The second essential element in a retention strategy is communication, specifically

a communications process that's structured to

inform, emphasize and reaffirm to employees that

their workplace contributions are having an impact.

Communication with the staff will provide the

insights in order to know how the employees feel

about working for the business. An effective and

sensitive communications plan can provide with the

insight on exactly what's driving employee morale

and how the staff members feel about the company.

3. Loyalty. The third element in a successful

employee retention strategy is employee loyalty. True loyalty is not an enforced requirement but an

earned response to the trust, respect and

commitment shown to the individuals in your

company. When someone demonstrates loyalty to

their employees, they'll reciprocate with

commitment and loyalty to their business.

4. Competitive advantage. The fourth and final

element in the strategy to retain employees has to

do with the competitive advantage. While that may

seem odd at first, think about it: People want to

work for a winner. What sets your company apart

from your competition? How are you--and as a

result, your employees--making a difference in

your industry, in your community, and for your

customers? Take the time to identify and inform the

clients and the employees about the unique

competitive advantage. If the product is similar to others in the marketplace, the service can be what

distinguishes the company. People want to be with

a winner...and that includes employees.

Together, these four elements can provide

with a retention strategy capable of producing

amazing results.

IV. NEED & IMPORTANCE

OF EMPLOYEE RETENTION

Let us understand why retaining a

valuable employee is essential for an organization.

Hiring is not an easy process: The HR

Professional shortlists few individuals from a large

pool of talent, conducts preliminary interviews and

eventually forwards it to the respective line

managers who further grill them to judge whether

they are fit for the organization or not. Recruiting

the right candidate is a time consuming process.

An organization invests time and money in

grooming an individual and makes him ready to

work and understand the corporate culture: A new

joinee is completely raw and the management

really has to work hard to train him for his overall

development. Finding a right employee for an

organization is a tedious job and all efforts simply

go waste when the employee leaves.

When an individual resigns from his

present organization, it is more likely that he would join the competitors: In such cases, employees tend

to take all the strategies, policies from the current

organization to the new one. Individuals take all the

important data, information and statistics to their

new organization and in some cases even leak the

secrets of the previous organization. To avoid such

cases, it is essential that the new joinee is made to

sign a document which stops him from passing on

any information even if he leaves the organization.

Strict policy should be made which prevents the

employees to join the competitors. This is an effective way to retain the employees.

The employees working for a longer

period of time are more familiar with the

company’s policies, guidelines and thus they adjust

better: They perform better than individuals who

change jobs frequently. Employees who spend a

considerable time in an organization know the

organization in and out and thus are in a position to

contribute effectively.

Every individual needs time to adjust with

others: One needs time to know his team members

well. Organizations are always benefited when the


23

employees are compatible with each other and

discuss things among themselves to come out with

something beneficial for all. Individuals find it

really difficult to establish a comfort level with the

other person. After striking a rapport with an

existing employee, it is a challenge for the

employees to adjust with someone new and most

importantly trust him. It is a human tendency to compare a new joinee with the previous employees

and always find faults in him.

It has been observed that individuals

sticking to an organization for a longer span is

more loyal towards the management and the

organization: They enjoy all kinds of benefits from

the organization and as a result are more attached

to it. They hardly badmouth their organization and

always think in favour of the management. For

them the organization comes first and all other

things later. It is essential for the organization to retain

the valuable employees showing potential: Every

organization needs hardworking and talented

employees who can really come out with

something creative and different. No organization

can survive if all the top performers quit. It is

essential for the organization to retain those

employees who really work hard and are

indispensable for the system.

The management must understand the

difference between a valuable employee and an

employee who doesn’t contribute much to the

organization. Sincere efforts must be made to

encourage the employees so that they stay happy in

the current organization and do not look for a

change.

V. COST OF LOSING AN

EMPLOYEE

Consider the real "total cost" of losing an

employee:

Cost of hiring a new person (advertising,

interviewing, screening, hiring)

Cost of on boarding a new person (training,

management time)

Lost productivity (a new person may take 1-2

years to reach the productivity of an existing

person)

Lost engagement (other employees who see

high turnover disengage and lose productivity)

Customer service and errors (new

employees

take longer and are often less skilled at solving

problems). In healthcare this may result in much higher error rates, illness, and other very expensive

costs (which are not seen by HR)

Training cost (over 2-3 years you likely invest

10-20% of an employee's salary or more in

training, that is gone)

Cultural impact (whenever someone

leaves

others take time to ask "why?"). And most importantly of all, we have to

remember that people are what we call an

"appreciating asset." The longer we stay with an

organization the more productive we get - we learn

the systems, we learn the products, and we learn

how to work together.

VI. THE ECONOMIC VALUE

OF EMPLOYEES OVER TIME

The following simple chart shows that initially

most employees are a "cost" to the organization,

and that over time, with the right talent practices,

they become more and more valuable. Our job in

HR is to attract the "right people" and move them

up this curve as rapidly and effectively as possible.

Fig 1: Economic Value of an Employee to the

Organization over Time

Obviously for us as employees, we see

this same effect. Early in our days in a new job we

feel somewhat unproductive and often search for

ways to add more value. But in the right

environment (on boarding, coaching, training,

teamwork) we rapidly "find our place" and start to

add more and more value.

A New Model to Drive Retention: Your Talent

"System"

Right now retention has become an

important topic for many reasons. The economy is

picking up; young employees want more career

growth; the work environment in companies has

not kept up with the outside world; management

doesn't always understand how to motivate younger

people; and in developing economies the workforce

is simply in great demand and the competition for

talent is severe. And we know that high-performing


24

companies have loyal employees. One of the most

important studies on this was done by Harvard

many years ago and it proves that only by making

your employees happy can you ultimately make

your customers happy.

Other researcher called "Lay off the

Layoffs" similarly shows that companies that push

layoffs on their employees create long term problems which often take years to fix. Layoffs,

like retention problems, create low levels of

employee commitment which in turn move

employees back down the value curve.

Typically the model involves a whole variety

of factors, and these factors take on different

weights depending on the age, demographic, and

role of the employee. Some of the interesting things

to consider:

Compensation plays a role, but not as much as

you may think. All the experience we have shows that for mid-performing people compensation is a

"hygiene" factor - too little money will definitely

create high mix, but over compensating people

won't make up for a poor work environment.

Job fit is critically important. For years,

companies have talked about the "employee value

proposition." In reality there is a "job value

proposition." Some jobs are particularly

demanding. If one honestly explains these roles

and their positives and negatives they will attract

people that "fit."

Career opportunities matter. Today most

companies are going through a "crew shift" as

boomer generation employees retire and young people enter management and high value positions.

Younger people are motivated by growth, career

opportunity, and meaning. Some research several

years ago showed that while young people want

the same types of benefits and work-life balance as

older people, they are particularly focused on fun,

collaboration, and the ability to be with others they

enjoy. So the prospect of a "career" is more than

just advancement.

The work environment matters. It includes

recognition, engagement, leadership, and management. It all shows clearly that people at

work respond through Maslow's Hierarchy of

Needs. Once they are "safe" – i.e. paid well, they

look for more meaningful value at work. These

"non-compensation" and "non-job" factors are

bigger than ever now.

VII. HOW TO IMPROVE

EMPLOYEE RETENTION?

The benefits of improved retention are

enormous, reduced turnover costs, improved

service productivity, higher customer satisfaction, a

more knowledgeable workforce and better

employee morale. Retention is a result of thinking

strategically and doing many things well. There is

no one tool or technique that alone will get

results. The entire talent supply chain must be

reviewed to get maximum benefit.

1. Many organizations ignore the basics: Be data driven: Good data will drive good

decisions.

Few organizations truly understand the

cost of turnover: Costs include recruitment,

selection, orientation, loss of productivity, vacancy

costs and customer impact costs. Knowing the

costs is an important first step because it creates the

resolve to make changes.

Know why your employees are leaving

your organization. Exit interviews are helpful, but

may not give you accurate data.

Know the best sources for your new hires.

Cultivate relationships with these sources to increase the number of candidates

applying for positions.

2. Develop a profile of your ideal candidate:

Retention begins with recruitment. Identify the key

elements of the kinds of people you want to attract

and keep - those that will fit your culture, support

your mission and enjoy their work.

3. Develop a compelling value proposition: The

challenge is to differentiate from all other competitors. Too many organizations focus on pay,

when in fact, the work itself is often what can be

most attractive to the right candidates.

4. Increase your pool of candidates: To increase

retention, one must hire only the candidates who

are most likely to stay and be productive. Identify

the most productive, best places to recruit, then put

together a focused recruitment plan to increase the

numbers of viable candidates.

5. Improve your selection process: The selection

process needs to be fast and valid so that one can identify good candidates and make offers quickly.

Map the selection process and work through

solutions to improve both cycle time and the

quality of hires. Focus on the ideal candidate

characteristics and select for the profile traits.

6. Invest in employee orientation: One must make

sure a person has a positive entry experience in the

organization. Half of all people who leave a job in

the first ninety days make that decision on day one

or two.

7. Focus on people development: People will

check out mentally long before they check out physically. Mentor programs can be highly

effective in boosting retention of great employees.

Well designed mentor programs speed

development of both the new employee and the

mentor. Identify ways to keep people learning and

developing even after a few years on the job. For

example, special projects or a transfer to a different


25

part of the organization can help keep high

performers stimulated and challenged.

8. Develop your managers: There are several

factors that will keep an employee in one

company. The most important factor is quality

managers. Employees stay where they have a

manager who truly manages them. Great managers

listen to employee ideas and encourage collaboration. One has to make sure that the

managers and supervisors demonstrate high quality

skills. When employees leave, they usually leave

managers, not companies.

9. Run a high-performing organization: People

want to work for winners. The best performing

organizations have a tremendous advantage in getting and keeping good people.

Align your strategy, structure, people and

processes. Make sure your employees understand the big picture and can see how they individually

support the strategy. Establish measures and let

everyone know how you're doing on a regular

basis.

10. Provide employee recognition: Employees stay

where they feel appreciated. Encourage individual

management recognition but also develop

organizational recognition vehicles. Simple

recognition of jobs well done in the quarterly

newsletter, pictures on the bulletin board, dinner

gift certificates, and other small rewards provide a high return on investment.

VIII. CONCLUSION

A methodical approach to assessing the

talent chain is the best way to identify ways to

improve outcomes. Retention becomes the

strategies rather than the outcome. Employee

retention takes into account the various measures

taken so that an individual stays in an organization

for the maximum period of time. A distinction

should be drawn between low-performing

employees and top performers, and efforts to retain

employees should be targeted at valuable, contributing employees. Remember, retention is the

result of doing many things well.

REFERENCES [1] Hall, R. (2005). Practical

Retention Strategies, Hooked on

training.

[2] Irwin, T. (2011, November 29).

United Kingdom: Five Top

Employee Retention Strategies

[3] Vishal Gupta; Shweta

Shrivastava. (2007, November),

Employee retention-Key to

success. [4] Paul R. Ahr Thomas B. Ahr

(Paperback-December 2000)

Overturn turnover: Why some

employees leave, why some

employees stay & ways to keep

the ones you want to stay.

[5] Philips (2008), Managing

Employee Retention-A Strategic

Accountability Approach.

[6] www.mondaq.com

http://www.mondaq.com/


26

Effects of Road Geometrics on Accidents: A case Study of NH-

45 through Nellore to Kavali

,

ABSTRACT

Pranay Kumar G 1 , Anvesh Kumar M2, Dr.Suresh Babu T 3

1M.Tech student, IV semester, Visvodaya Engineering College , Kavali, 2 Assistant Professor, Department of Civil Engineering, Visvodaya Engineering College , Kavali, 3Professor and Head ,Department of Civil Engineering, Visvodaya Engineering College , Kavali,

due to road traffic crashes. Developing

countries account for up to 85% of all the

Accidents are not natural but they are caused is a

common saying in the area of traffic safety. Thus,

if accidents are caused by some factors, those can

be identified and appropriate remedial measures

can be developed and implemented to the extent feasible. It is strongly felt that most of the

accidents, being a multi factor event, are not

merel y due to drivers fault on account of driver's

negligence or ignorance of traffic rules and

regulations, but also due to many other related

factors such as abrupt changes in road conditions,

flow characteristics, road user's behaviour,

climatic conditions, visibility and absence of

traffic guidance, control and management

devices. In the present study, the accident data of

the proposed stretch from the year 2010 -2014 has

been collected from concerned police stations in prepared data formats. The data sheet covers all

the accident details. At each police station First

Information Reports were referr ed to note down

the accident particulars. The analysis work was

carried out for the proposed stretch and black

spots were identified. After this, the main data

required is the geometrics of the road way which

will be useful for the evaluation of the black spot

locations. A model is built with the accident rate

as dependent variable and road environment

factors such as road width, shoulder width,

curvatures, sight distances, radius, and number of cross roads or junctions, no of culverts etc as

independent variables.

Keywords: Key words : Crash Density, Super

Elevation, Crash frequency , Sight distance,

Crash rare, Accident rate .

I. INTRODUCTION

People, roads and vehicles form the same

important combination all over the world that

of being able to transfer themselves or goods from one place to the other. Road accidents

became a serious problem throughout the

world, in social, health and economic terms.

Over twenty million people are injured and

over one million are killed every year globally

fatalities. Traffic accidents in developing

countries have been increasing rapidly and

have in some cases become more deadly than

the diseases that historically affected the

population.

II. OBJECTIVES OF THE STUDY The objectives of the present study are

To identify the Blackspot locations

To identify the road design elements that affect road safety

To develop models to determine the appropriate balance between road design standards and road safety.

III. METHODOLOGY AND

INVESTIGATION

The First stage of the study includes preparation of

accident data format to collect the accident data

from the police stations. The forms are prepared as per IRC: 53 1982. These forms if filled properly provide the necessary information about the accidents like date of occurrence, day of occurrence, time of accident, type of area, chainage, weather condition, Classification of the accident, number of deaths, number of injured, nature of accident, accused vehicle driver gender and age, person driving vehicle, type of accused and victim vehicles, type of license, type of maneuver, responsibility of driver, type of junction, type of traffic control, cause of accident, and collision diagram. The formats of the forms have been designed to facilitate computer processing such that each data is divided into different sub categories and all those categories are given coding. For example type of area is divided into ten sub categories and given coding like near school or college, nea r a bus stop, near a temple, at pedestrian crossing etc.

Accident data collection from secondary sources

The accident data of ah45 through Nellore to kavali for five consecutive years i.e. 2010, 2011, 2012, 2013, and 2014 has to be collected from fir reports. In the fir reports the complete details about the accidents will be available, and whatever data


27

is necessary to fill the accident data sheet that has to be noted down for each accident that was recorded in that police station. In the same way in all the police stations covering AH-45 through Nellore to kavali, the accident data has to be collected.

Selection of black spot identification method

after the general analysis, depending up on data availability, two or more black spot identification methods are to be selected for comparison among them. For the present study crash density and crash frequency methods are considered. From the crash density method a stretch (section of road under a police station area) can be selected in which more number of accidents occurred when compared with length of the stretch. From the crash frequency method accident prone locations in that stretch can be identified.

Analysis and identification of black spots black spots are to be identified according to crash density and crash frequency methods through the analysis of accident data collected. Critical crash density and critical crash frequency values are to be calculated for all the locations. The locations which are having the more crash frequency or crash density values than their critical va lues are said to be critical locations i.e, blackspot locations.

Selection of major black spots

from the identified black spots a few major black spots are to be selected which are having the highest crash frequency and crash density for the further continuation of work i.e collection of geometric features.

Collection of geometric features at selected

black spot

in this section the geometric features of each selected black spot like cross-section details, camber, super elevation, signs and markings, drainage, sight distance, horizontal and vertical profiles and encroachment details will be collected. The total station instrument is going to be used for the present study to collect the geometrical details. From the total station instrument north- east coordinates of different locations has to be recorded.

Tabulation and extraction of geometric details from the collected data

the geometric details like camber, super elevation, distances, gradients etc are to be extracted from the data collected in the field and tabulated to proceed for further analysis.

Modelling for accident prediction

statistical model has to be developed from the available data to give the predicted accident count when the geometric details of a particular section were known. For this, mini tab software is going to be used. Mini tab software is statistical software from which all types of statistics can be performed based on the data available. For the present study multiple regression equation is to be developed for the prediction of accidents for a section with known geometrical details. From the analysis and comparisons, the proposals for the accident reduction measures can be given.

Name of the Police Station

Total no of accidents

in 5

years

On AH-45 near Eenadu office Road 69

On AH-45 near Ayyappagudi Circle 17

On AH-45 Near Kanuparthipadu 64

On AH-45 Near Saakshi office 47

On AH-45 Near Narayana Engineering College 24

On AH-45 Near Prashanthi nagar 27

Table 1 : Number of accidents at locations

IV. ANALYSIS OF ACCIDENT DATA

AH 45 is a National Highway passing through the Nellore and Kavali, having a total length of 58 km, all with two lane bitumen surface.

The accident data was collected from the

FIR reports in the police stations covering the

AH45 through Nellore to Kavali. For this data

recording, an accident data format was prepared

and all the data was recorded on those sheets. A

total number of 804 accidents were recorded in the

entire stretch. A sample of the data sheet was

shown in Appendix A. The collected data was

tabulated in MS-Access and general analysis has

been done like consolidating the total no accidents

in each police station, severity wise, monthly

distribution of accidents, type of accused and

victim vehicle, nature of accident occurred, time

wise distribution, type of area, responsibility of

driver, etc. Accident data is summarized in Tables

4.1 and 4.8.

Table 4.1 shows the police station wise distribution of accidents throughout the AH45 through Nellore to Kavali. In the total accident data 9% accidents are recorded in Near Eenadu Press and next 18% of accidents are recorded in Gowravaram police station area.


28

Table 2 : Nature of accident

Table 3 Accident details based on Classification of Accident

Average crash density = 4.71

Standard deviation of crash density = 2.41 Critical Crash Density = 4.71+2.41 = 7.12

As per Crash frequency Method Average Crash Frequency = 5.44 StandardDeviation of Crash Frequency = 3.51

Critical Crash Frequency = 5.44+3.51 = 8.95

Table 4:Characteristic wise peak accident records

out of 816 accidents

From the above table it can be clearly observed that rear end collisions are occurring in maximum amount at near or inside a village. The main accused vehicle is lorry/truck and victim vehicle is two wheeler. The main reason for more number of accidents is exceeding lawful speed while crossing another vehicle.

V. GEOMETRIC DETAILS

Horizontal Profile

Characteristic

Type of Characteristic

with

No of

accidents

max number of

Accidents

Nature of accident

Rear end collision

216

Type of area Near or inside a village 85

Type of accused vehicle

Lorry/DCM/Tractor/Truck

167

Type of victim vehicle Two wheeler 133

Type of maneuver Crossing 146

Classification of accident Minor injury 167

Nature of accident No of accidents % of accidents

Over turning 56 7

Head on collision 118 14.46

Rear end collision 216 26.5

Collision brush / Side swipe 86 10.5

Right angled collision 54 6.25

Skidding 76 9.3

Right turn collision 125 15.31

Others 85 10.41

Class ification of

accident

No of

accidents

% of

accidents

Fatal 303 37.13

Grievous injury 346 42.40

Minor injury 167 20.47


29

Vertical Profile

V.RESULTS

Location of Accident

Length of

stretch (km)

Degrees of

curvature per Km

S.E

(%)

Sight

distance (m)

Total

Rise (m)

Crashes

CR

On AH-45 near Eenadu office Road

165

0

2.9

130

2.3

11

1.5

On AH-45 Near Kanuparthipadu

690

0

3.2

125

5.6

2

1.7

On AH-45 Near

Saakshi office

419

0

3.4

145

3.8

4

0.8

On AH-45 Near Gowravaram Village

1052.2

62.56

6.9

70

4.6

16

3.3

On AH-45 Near

Musunuru Village

525

9.33

6.8

75

4.2

8

1.4

MODEL DEVELOPMENT

Since ,

CR = 0.006979X1 -0.0892 X2 + 0.011731 X3 +

0.3783 X4 - 5.3888

Table : Actual and Predicted crash rates

R square value = 1, Where

X3 = Sight Distance X4 =

Number of Crashes

X1 = Length of the

curve X2 = Degree of

Curvature

Using the equation, crash rates are predicted for

the same data from which the equation was

developed. Those actual and predicted crash rates

were given in table

Location of Accident

Actual CR Predicted

CR

On AH-45 near Eenadu

office Road

1.5

1.449865

On AH-45 Near

Kanuparthipadu

1.7

1.650485

On AH-45 Near Saakshi

office

0.8

0.750396

On AH-45 Near Gowravaram

Village

3.3

3.248922


30

VII. Conclusions

From the analysis of the accident data it is clear that rear end collisions are occurring more (44%), accidents are occurring at near or inside a village (54%), while the major accused vehicle is a lorry (44%) and major victim is vehicle (31%) is two wheeler. Crossing is the major type of maneuver (50%), and exceeding lawful speed (88%) is the major characteristic when responsibility of driver is considered. From the cross analysis of accident data it was observed that when the accused vehicle is a lorry and victim vehicle is a two wheeler (12%) more number of accidents have been taken place. In the same way, while crossing type of maneuver fatal accidents are recorded as 15% and minor accidents are recorded as 30%. And when lorry crosses any other vehicle, 22% of accidents were taken place. 10% of accidents occurred while some vehicle crosses two wheeler. While considering responsibility of driver, exceeding lawful speed is the major reason for which type of accused vehicle is lorry (38%), victim vehicle is two wheeler (28%), and type of maneuver is crossing (46%). From the crash density method Gowravaram Rural police station stretch was selected for analysis as its crash density is 17.25. From the model developed it was observed that the relation between crash rate with degrees of curvature and total rise is positive and with super elevation and sight dis tance is negative. From the field observation it was observed that at cross roads or junctions the chances of occurrence of an accident is more.

VIII. References

1. Road safety risk reporter The effect of geometric road design standards on road safety Aug 2006, published by ARRB group. ( www.arrb.co m.au)

2. Schelling, A.G.O.A. (1997), Manual of Road Safety Audit , Road Directorate, Road Safety and Environmental Division, Denmark

3. Road safety guidelines for Asian and Pacific Region, sa fe planning and design of roads by Asian Development Bank . ( www.adb.org)

4. AASTHO, Mass highway design manual, a policy on geometric design of highways and streets2001 April 2003.

5. Arvind Ku mar Mavoori., An activity plan for Indian Road Safety , Department of Science and Technology Linköpings University, Sweden, 2005.

6. G. M. Gibreel, S. M. Easa, Y. Hassan and I . A. El-Dimeery., State of the art of Highway

Geometric Design consistency, Journal of

Transportation engineering July/august

1999/313

7. Jacobs.G, Tho mas.A, Astrop.A (2002)

Estimating global road fatalities, Global Road Safety Partnership , TRL Report 445, U.K

8. I A Sayar (1994) Accident Black spot Investigation Transport Research Laboratory , Crowthorne Berkshine United Kingdom.

9. T.S.Reddy, B. Srin ivasa rao, E.Madhu, and Santhosh Jalhal Accident Study on National Highway - 5 between Anakapalli to Visakhapatnam Proceedings of the Eastern Asia Society for Transportation Studies , Vo l. 5, pp. 1973 - 1988, 2005

10. City of Happy Valley Municipal Code , Public Works Department Engineering Division Engineering Design and Standards Details Manual

11. Road accident form A-1 and 4 , IRC:53-1982.

12. Mittal.N, Sarin.S.M , (2001), Cost effective safety measures for metropolitan cities in India, Indian Highways, August 2001.

http://www.arrb.co/


31

ROLE OF MEDICINAL PLANTS IN HEALTH CARE

IMPORTANCE AND CONSERVATION

B.SIRISHA Assistant professor of chemistry

Geethanjali Institute of Science and Technology, Nellore.

ABSTRACT

A Medicinal plant is any plant which in one or

more of its organ contain substances that can be

used for the therapeutic purposes or which are

precursors for the synthesis of useful drugs

“Since the dawn of history the medicinal plants

have been used for treatment of illness and

diseases. These medicinal plants contain bioactive

chemical substances such as alkaloids, tannins,

quinines, lactones, glycosides, resins etc. The

active ingredients of medicinal plants can be

found either in roots, leaves, stems, flowers, bark,

fruits or seeds. During the past three decades the

demand and utilization of medicinal plants has

increased globally. There is now a consenses

regarding the importance of medicinal plants and

traditional health systems in solving the

healthcare problems, safety of medicinal plants in

curing of many diseases. The agricultural and

anthropogenic activities leads to loss and extinct

of some useful species. To this end some measures

to be considered to ensure sustainability and

conservation of palnts.In conclusion the vital role

of medicinal plants will aim at formulating an

integrative health system for the overall goal of

maintaining, enhancing and sustaining good

health care

Keywords: Medicinal plants, BioactivcChemical substances, Parts of the plant, Health care, Sustainability, Conservation

I. INTRODUCTION

Plants have been used from ancient times

to attempt cures for diseases and to relive physical suffering. Medicinal plants are those plants that are

used (parts, extracts) in treating and preventing

specific ailments and diseases that affect human

beings. These plants are provided with rich sources

of bioactive compounds formed during the

metabolic processes. Most of these bioactive

compounds are found in medicinal plant parts

[roots, bark, leaves, flowers, fruits,seeds] which are

the precursors of the synthesis of useful drugs.

Recently the World Health Organisation (WHO)

estimated that 80% of the worldwide population

depend on medicinal plants for their primary health

care. It is a ray of hope for many people that traditional herbal medicines research will play a

critical role in global health

II. BIOACTIVE COMPOUNDS-

DEFINITION

The term "bioactive" is composed by two words:

bio- and -active. In etymology: bio- from the Greek

(βίο-) "bios" [bio] refers: life. And –active from the

Latin "activus", means: dynamic, full of energy,

with energy [1-3], or involves an activity. In a

strictly scientific sense, the term "bioactive" is an

alternative term for "biologically active". In medical dictionaries, a bioactive substance is

defined as a substance having an effect on the

living tissues A compound (or a substance) having

biological activity, if it has a direct effect on a

living organism. These effects may be positive or

negative depending on the substance, the dose

or the bioavailability . Indeed, these compounds

have wide range of effects, starting with the good

maintenance of health even healing effect, or be

dangerous even fatal. The ingested dose of

bioactive compounds is often decisive for whether

the effect positive or adverse.. Schrezenmeir J. et al.(2000) consider that the definition of bioactivity

is usually refined by two caveats. One has already

been discussed (positive and negative health

effects), and the other requires in the bioactive

component to give a measurable biological effect in

a physiologically realistic level.

Bioactivecompounds contain chemical Bioactive

compounds contain chemicals that are found in

Small quantities in plants and certain foods (such as

fruits, vegetables, nuts, oils and whole grains); they

have actions in the body that can promote good

health Thus; plants are not the sole source of

bioactive substances. These substances are also

found in other living organisms and

microorganisms, such as bacteria, mushroom, and

in some groups of animals.

The bioactive compounds present in the medicinal

plants are Alkaloids, Flavanoids, Resins, Saponins

Glycosides, Tannins, Phenols etc,


32

III. PRESENCE OF BIOACTIVE

COMPOUNDS-MEDICINALPLANTS

(PARTS, MEDICINAL USES)

Generally, it is found that the bioactive

compounds are present in the storage organs of the

plants especially in roots andseeds, and less in bark,

leaves, fruits. The amount of the bioactive chemical

substances present in any organ is so small, but

most likely the action is valuable to humans in the

treatment of diseases. The following is the

illustration.

S. No

Plant name

Part Bioactive compound

Medicinal use

1. Aloevera Leaves Alkaloids, Wound healing, skin burns, ulcer

2. Azadirac

hta

Indica

Whole

plant

Flavanoids,

tannins,

alkaloids

Small

pox, cholera ,diarrhoea

3. Bombax

ceibo

Stem

,roots

seeds

Phenols,

glycosides,

tannins

Rheumatism,

leprosy, dysentery

4. Centella

asiatica

Roots,

leaves

Alkaloids,

glycosides

Abdominal

tumors,cancerstub

erculosis

5. Daturam

etel

Fruits,

seeds,

leaves

Alkaloids,trit

erpenes

Piles,diarrhoea,ski

n diseases

6. Gmelina

arborea

Leave

roots

Resins,

alkaloids

Anemia,leprosy

stomachic

abdominal pains

7. Polyalthi a logifolia

Leave, bark.

Alkaloids resins,tannin s

Influenza,respirato ry troubles,diabetis

8. Saracaso

ca

Leave Phenols,quin

ine,essential oils

Expectorant in

bronchitis,ringwor m

9. Terminal

ia

bellirica

Fruits Tannins,

resins

Cardiac

weakness,cough,

hyperacidity

10. Vitexneg

undo

Leaves

stem,

bark

Alkaloids

essential oils

Swelling of joints,

rheumatic attacks

IMAGES OF THE MEDICINAL PLANTS:

1)ALOEVERA

2) POLYALTHIALOGIFOLIA

3) DATURAMETEL

4) GMELINA ARBOREA

5) SARACA ASOCA

6) ITENEXNEGUNDA

7) TERMINALIA BELLIRICA

8) CENTELLA ASIATICA


33

9) BOMBAXCEIBO

10) AZADIRACHTAINDICA

\

IV. DISCUSSION

A number of medicinal plants ranging from

grasses to shrubs and to tall tree are considered.

Some exist in the wild while others are

domesticated.

The basic active ingredients used for treating

various ailments are accumulated in the different

parts of plants such as leaves, roots, bark, seeds and

fruits. The different methods of preparation depend

on the parts of the plant by which these bioactive

ingredients are found. Some herbs were discovered

to have the ability of curing while some are specific on a particular ailments .Administration of

medicinal extracts varies with the different ailments

and parts of the body in which they used for.

V. MAINTENANCE-MEDICINAL

PLANTS-CONSERVATION

Medicinal plants form part of the natural

ecosystems, their exploitation despite how

sustainable ,will inevitably have some effect on the

biodiversity of these systems leading to change(or)

even loss of some species with vital curative

ingredients. Utilization should therefore always go

hand in hand with means to ensuring sustainability

and conservation of the resources.

Such measures include:

1) Non-Destructive harvesting.

2) Setting aside, reserves areas and

cultivation of botanical gardens.

3) Conservation and recovery of

endangered medicinal plants species

4) Introduction of new species into

cultivation to take the pressure of wild species

population. 5) Establishment of conservation stock

and collection of seeds.

6) Proper management of the population

of endemic species to maintain their demographic

integrity and genetic variability.

7) Principles of sustainable use of

medicinal plants and equitable sharing of benefits

integrated into national and local legislation and

community awareness

VI. CONCLUSION

Any plan of action for enhancing a

sustainable identification and traditional uses of

medicinal palntsmust be tailored to the specific

needs of particular situation in the appropriate

method. The efficiency of any plant as medicine

cannot be determined through guessing but by

knowing the major active principles (ingredients) in such plant and what is capable of curing. This calls

for further research and analysis of the popular

medicinal plants and consequent integration of

traditional plants in the nation’s health sector

Some of the medicinal plants identified so

far should serve as guide to the Government,

healthcare workers, Agricultural extension experts in formulating an integrative health system that

could serve the common goal of maintaining,

enhancing and sustaining good health care

REFERENCE

[1] Emereonye,K.R.(2007),(Medicinal plants: an

Alternative in health care delivery, A HND thesis ,Imo State Polytechnic Umuagwo,Imo

State,Nigeria [2] Manikandan,L.,Senthilkumar,

G.P.Rajesh,L.TandSureh,R.(2006).Cancerche mopreventive agents from medicinal plants.In:Trivedi,P.C(ed).Medicinal plants:ethnobotanical Approach.Agrobios,India.p.410

[3] 2011 IUCN ,International Union for Conservation of Nature and Natural Resources

[4] Alaribe ,S.I.(2008).A survey of the importance and problems of traditional health care medicine ,A case study of Ezinihitte L.G.A.ImoState.Unpublished B.Sc.project,A.I.F.C.E. Owerri, Imo State

[5] Stary F (1998). The Natural Guide to Medicinal Plantsand Herbs.Tiger Books International, London.pp.12-1


34

IAAS:Improving Efficiency of Cloud Architecture Using DAS

and SAN

1B.Susrutha ,2 K.VenkataRamana,3I.Shalini 1Asst.Professor,Department of CSE,Geethanjali Institute of Science and Technology, Nellore.

2Asst. Professor, Department of CSE , Geethanjali Institute of Science and Technology, Nellore. 3 Asst. Professor, Department of CSE ,PBRVITS,Kavali.

ABSTRACT

“Cloud computing” is a term, which involves

virtualization, distributed computing, networking,

software and web services. A cloud consists of

several elements such as clients, data center and

distributed servers. Cloud computing refers to the

delivery of computing and storage capacity as a

service to a heterogeneous community of end

recipients. Cloud computing provides scientists

with a completely new model of utilizing the

Computing infrastructure. Compute resources,

storage resources, as well as applications, can be

dynamically provisioned (and integrated within

the existing infrastructure)on a pay per use basis.

We identify three categories of cloud computing

services: Infrastructure-as-a-Service (IaaS), that

is raw, infrastructure and associated middleware,

Platform-as-a-Service (PaaS), that is, APIs for

developing applications on an abstract platform,

and Software-as-a-Service (SaaS), that is, support

for running software services remotely.[36]

The scientific community has not yet started to

adopt PaaS or SaaS solutions, mainly to avoid

porting legacy applications and for lack of the

needed scientific computing services, respectively.

Thus, in this study we are focusing on IaaS

providers.

Keywords: : Infrastructure as a service, API, Software as a service

I.INTRODUCTION

Cloud Computing, the long-held dream of computing as a utility, has the potential to

transform a large part of the IT industry, making

software even more attractive as a service and

shaping the way IT hardware is designed and

purchased. Developers with innovative ideas for

new Internet services no longer require the large

capital outlays in hardware to deploy their service

or the human expense to operate it. They need not

be concerned about overprovisioning for a service

whose popularity does not meet their predictions,

thus wasting costly resources, or underprovisioning for one that becomes wildly popular, thus missing

potential customers and revenue. Moreover,

companies with large batch-oriented tasks can get

results as quickly as their programs can scale, since

using 1000 servers for one hour costs no more than

using one server for 1000 hours. This elasticity of

premium for large scale, is unprecedented in the

history of IT.

Cloud Computing refers to both the applications

delivered as services over the Internet and the

hardware and systems software in the datacenters

that provide those services. The services

themselves have long been referred to as Software

as a Service (SaaS). The datacenter hardware and software is what we will call a Cloud. When a

Cloud is made available in a pay-as-you-go manner

to the general public, we call it a Public Cloud; the

service being sold is Utility Computing. We use the

term Private Cloud to refer to internal datacenters

of a business or other organization, not made

available to the general public. Thus, Cloud

Computing is the sum of SaaS and Utility

Computing, but does not include Private Clouds.

People can be users or providers of SaaS, or users

or providers of Utility Computing. We focus on SaaS Providers (Cloud Users) and Cloud Providers,

which have received less attention than SaaS.

Infrastructure-as-a-Service (IaaS) clouds are

becoming a rich and active branch of commercial

ICT services. Users of IaaS clouds can provision

“processing, storage, networks, and other

fundamental resources” [1] on-demand, that is,

when needed, for as long as needed, and paying

only for what is actually consumed. For the past

five years, commercial IaaS clouds such as

Amazon’s EC2 have gained an increasing user base, from small and medium businesses [2] to

scientific HPC users [3], [4]. However, the

increased adoption of clouds and perhaps even the

pricing models depend on the ability of

(prospective) cloud users to benchmark and

compare commercial cloud services. In this article,

we investigate the IaaS cloud-specific elements of

benchmarking from the user perspective. An

important characteristic of IaaS clouds is good

performance, which needs to be ensured on-

demand and sustained when needed over a long

period of time. However, as we have witnessed happening to several other new technologies while

still in their infancy, notably with grid computing,

we believe IaaS clouds may also undergo a period

of inconsistent performance management.

Benchmarking is a traditional approach to verify

that the performance of a system meets the

requirements. When benchmarking results are

published, for example through mixed consumer-

provider organizations such as SPEC and TPC, the


35

consumers can easily compare products and put

pressure on the providers to use best-practices and

perhaps lower costs. At the moment, the use of

clouds is fragmented across many different

application areas, such as hosting applications,

media, games, and web sites, E-commerce, On-

Demand Workforce and CRM, high-performance

computing, search, and raw resources for various usage. Each application area has its own (de facto)

performance standards that have to be met by

commercial clouds, and some have even developed

benchmarks (e.g., BioBench for Bioinformatics and

RUBiS for online business). For IaaS clouds, we

conjecture that the probable characteristics of

current and near-future workloads can be derived

from three major trends emerging from the last

decade of grid and large-scale computing. First,

individual jobs are now predominantly split into

smaller compute or data-intensive tasks (many tasks [5]); there are almost no tightly coupled

parallel jobs. Second, the duration of individual

tasks is diminishing with every year; few tasks are

still running for longer than one hour and a

majority requires only a few minutes to complete.

Third, compute-intensive jobs are split either into

bags-of-tasks (BoTs) or DAG-based workflows,

but dataintensive jobs may use a variety of

programming models, from MapReduce to general

dataflow. Cloud benchmarking is not a

straightforward application of older benchmarking

techniques. In the past, there have been several large-scale computing environments that have

similarities with clouds. Already decades ago, such

institutes as CERN and the IBM T.J. Watson

Research Center had large numbers of mainframes

(using virtualization through the Virtual Machine

operating system!) that also used multitenancy

across their departments. Similarly, some vendors

had large-scale installations for paid use by

customers through Remote Job Entry facilities. In

these environments, benchmarking and capacity

planning were performed in close collaboration between owners and customers. A big difference,

and advantage, for customers wishing to

benchmark their prospective computing

environments is that they can simply use access by

credit card to deploy and benchmark their

applications in the cloud: clouds do not only offer

elasticity on demand, they also offer (resources for)

capacity planning and benchmarking on demand.

The new challenge is that customers will have to

gain, through benchmarking, sufficient trust in the

performance.

II. QUADRANT FOR CLOUD

INFRASTRUCTURE

In the context of this Magic Quadrant, cloud

compute IaaS (hereafter referred to simply as

"cloud IaaS" or "IaaS") is defined as a

standardized, highly automated offering, where

compute resources, complemented by storage and networking capabilities, are owned by a service

provider and offered to the customer on demand.

The resources are scalable and elastic in near real

time, and metered by use. Self-service interfaces

are exposed directly to the customer, including a

Web-based UI and an API. The resources may be

single-tenant or multitenant, and hosted by the

service provider or on-premises in the customer's

data center. We draw a distinction between cloud

infrastructure as a service, and cloud infrastructure

as a technology platform; we call the latter cloud-

enabled system infrastructure (CESI). In cloud IaaS, the capabilities of a CESI are directly

exposed to the customer through self-service.

However, other services, including noncloud

services, may be delivered on top of a CESI; these

clouds-enabled services may include forms of

managed hosting, data center outsourcing and other

IT outsourcing services. In this Magic Quadrant,

we evaluate only cloud IaaS offerings; we do not

evaluate cloud-enabled services. (See "Technology

Overview for Cloud-Enabled System

Infrastructure," "Technology Overview for CloudEnabled Managed Hosting" and "Don't Be

Fooled by Offerings Falsely Masquerading as

Cloud Infrastructure as a Service" for more on this

distinction.) This Magic Quadrant covers all the

common use cases for cloud IaaS, including

development and testing, production environments

(including those supporting mission-critical

workloads) for both internal and customer-facing

applications, batch computing (including high-

performance computing [HPC]) and disaster

recovery. It encompasses[7] both single-application

workloads and "virtual data centers" (VDCs) hosting many diverse workloads. ) hosting many

diverse workloads. It includes suitability for a wide

range of application design patterns, including both

"cloud-native" application architectures and

enterprise application architectures.

III. Workflows of CLOUD

The fundamental building block of an infrastructure is a ‘workload.’1 Workloads can be thought of as the amount of work that a single server or ‘application container’ can provide given the amount of resources allocated to it. Those resources encompass processing (CPU & RAM), data (disk latency & throughput), and networking


36

(latency & throughput). Frequently, but not always, cloud workloads are delivered in virtual servers. Figure 2 (right) shows how a single workload (circled in red) might be delivered using a single virtual server spanning a variety of physical resources including compute, storage, and networking. A workload is an application or part of an application[8]. Examples of workloads include: • Transactional Database • Fileserver • Application Server • Web Server • Batch Data Processing (e.g. running Monte Carlo simulations) This means that a web application might have three distinct workload types: database, application business logic, and web serving. What you’ll notice about these three workloads is that they have differing requirements in terms of computation, storage, and networking. A database may require large amounts of CPU & RAM, fast storage, and low latency networking, while an application server might require large amounts of CPU & RAM only. Web servers need very little resources other than networking. When someone says “It depends on the workload” this is what they are referring to. Understanding workloads, designing your cloud for certain workload types, and the requirements those workloads may put on your underlying infrastructure is critical to success. This is why cloud providers must ask themselves: “Who is my customer and how can I make them.

IV.IAAS Architecture considerations

IaaS architecture is the structural design of a

computing network that enables the delivery of

computing resources as a service via the cloud.

Physical resources such as processing capacity and

data storage are examples of common components

that may be incorporated into a cloud computing

environment, under the IaaS (infrastructure as a

service) model of IT resource delivery.As with

traditional computing network design, IaaS

architecture aims to achieve optimal levels of efficiency, in the delivery of computing services to

end users. This requires an architectural design that

provides a highly available pool of cloud based IT

resources and which also adequately delivers its

resources in an elastic or scalable manner,

especially during times of peak demand. Since

cloud computing services are delivered to

consumers in a manner similar to a utility (e.g.

Water or electric services), organizations that

provide IaaS via the cloud need to develop and

implement an IaaS architecture that successfully optimizes the use of its physical computing

resources, in order to maximize cost savings and/or

revenue for the organization.

As with SaaS (software as a service) and PaaS

(platform as a service) solutions, the architectural

design of an IaaS solution is impacted by the

specific business requirements and goals of each

organization that delivers its IT resources via the

cloud. For example, a private enterprise typically

requires a different IaaS architecture than what is required by an IaaS vendor whose service

offerings[10] are primarily driven by revenue

concerns.Nevertheless, within the IaaS landscape

lies an opportunity that many enterprise private

cloud IaaS managers are frequently unaware of,

which is the ability for a private enterprise to to

monetize its IaaS offerings on a spot market,

thereby providing a secondary revenue stream that

can offset the normal operational costs of

delivering IT services within an enterprise.

Innovative companies are already capitalizing on

this facet of IaaS. Monetization of IaaS enterprise private cloud resources may be facilitated through

cloud computing clearinghouses who serve as

intermediaries or brokers for trading cloud

computing resources between buyers (consumers)

and sellers (cloud services providers).In the final

analysis, an organization needs to carefully

consider its current and future IT strategy, to ensure

that the design of its IaaS architecture can be scaled

to meet present organizational needs,while

retaining the capacity to capitalize on an ever

evolving model of IT service delivery in the cloud.

The cloud economy

BIZ

PROCESS(SOA

Enaled)

Application

Platform

Infrastructure


37

V.Layers of Iaas

IaaS can be delivered via a public cloud, a private cloud, a community cloud or a hybrid cloud. The infrastructure that is delivered by IaaS resides on the bottom layer of a cloud computing stack; with PaaS delivery occurring on the middle layer and SaaS delivery occurring on the top layer. In many cases, IaaS is bundled together with PaaS and SaaS delivery – as a complete cloud computing solution, as is the case with the hosted cloud services delivered by providers such as Amazon.com (i.e. its AWSoffering), Google (i.e. its App Engine offering) and Microsoft (i.e. its Azure/AppFabric offerings). In addition, IaaS frequently incorporates virtualization into its design in order to facilitate optimal levels of utilization for physical computing resources. Network connectivity and storage capacity are also included in the IaaS definition, since these resources are a part of the physical computing resources that are delivered by IaaS.[21]

Iaas provided by cloud as very good impact on todays computers era. A web application might have three distinct workload types: database, application business logic, and web serving. Iaas needs to provide integrity, confidentiality and security for a better performance improvement. So many vendors such as aneka,emc2 , Google, Rackspace, and so many other or involved in providing infrastructure for iaas. IaaS architecture aims to achieve optimal levels of efficiency, in the delivery of computing services to end users. In this article, we investigate the IaaS cloud-specific elements of benchmarking from the user perspective.

A) POD ARCHITECTURE IN IMPROVING IAAS PERFORMANCE

Large clouds have been working around these problems for a long time using a technique calling ‘podding’ or ‘sharding .There are many architectural decisions to be made, each of which has its own tradeoffs. As a guideline, design your pods based on workload needs, business requirements, and scale desirability. Find a partner with a strong track record to assist you if this is your first time.

There are many dimensions to consider, but let’s pick one to illustrate further in this section such as your storage architecture.

Fig: Cloud Control Systems.

There are a many ways to build a storage

architecture for virtualization, but we will constrain

the discussion to two options:

Direct-Attached Storage (DAS)[29] and Storage

Area Networks (SAN). Network-Attached Storage

(NAS), like NFS, would also be a fine choice for

your storage architecture, but is left out of this

paper for brevity’s sake6. Another reason to limit

our selves to DAS and SAN is that they are the

dominant storage architectures in most public

clouds. The first public clouds such as Amazon’s EC2, Rackspace, and GoGrid use a combination of

the open source Xen hypervisor along with

DAS.[29] The latest entrants, such as Savvis,

Terremark, and AT&T’s Synaptic Services use the

VMware hypervisor along with SAN. Their choices

are driven largely by cost and architecture. In the

case of the early entrants, they positioned

their clouds as consumer clouds using Xen and

DAS for their lower price point (‘free’ and cheap,

respectively). The latest

public clouds chose to position themselves as ‘business’ or enterprise clouds using the VMware

ESX hypervisor. VMware’s recommended

deployment model uses centralized SAN storage,

which allows for a number of features, such as live

migration (Aka ‘VMotion’ in VMware parlance)

where you can move a virtual server from one

physical server to another. The enterpriseclass

cloud choices are strategic in nature. They hope

that businesses will pay a premium for ‘advanced’

features or brand names. Regardless, a Xen pod can

be built with SAN and a VMware pod can be built

with DAS. The choices made by the currentcrop of providers are reflective of where they sourced their

architectural models: Amazon EC2 or VMware’s

best practices.

Let’s take a closer look.

.

POD ARCHITECTURE (DAS)

The DAS model dictates that everyphysical server

(“cloud node”) will have its own local storage system (Figure 5 to right). This means that from a

storage perspective a pod can be quite large as each

node added to the pod also adds storage capacity.

As a downside, the DAS model also means that

since there is no common storage system across all

servers some features like live migration are

extremely difficult or impossible to implement.

DAS forces your cloud operations or IT team into

managing a large amount of decentralized and

distributed storage. This can be a challenge at scale,

which is part of why centralized Storage Area

Networks (SAN) became quite popular. Imagine


38

that every node has 8 disk drives and you have

1,000 nodes. That is 8,000 disk drives spread over

60 racks. Each node may also have a local RAID

controller. Your team will have to tightly manage

the firmware of disk drives and RAID controllers

both in order to reduce hard to diagnose failure

conditions. Guaranteeing homogeneity of firmware

and chip versions across so many servers is difficult. This can be a significant management

challenge if not planned for.

Fig: POD Architecture Using DAS

POD ARCHITECTURE (SAN)

[29] In contrast to DAS, SAN embraces

centralization, which brings its own positives and

negatives. On the positive side, live migration and similar technologies are now possible, lowering the

operational overhead associated with running a

large scale cloud. Other capabilities like backups

and high availability in the case of a node’s failure

are also quite easy.

The negative is that pods must be much smaller.

The reason is that any given SAN will have some

kind of scaling limitation. It can only be so big and

can only serve so many cloud nodes. You could

deploy more than one SAN per pod, but you then

break the pod architectural model.

Here is a list of a few enterprise strength cloud computing IaaS providers:

Individual Consumer Advances in cloud computing

technology have brought the cost of cloud services

down, making it possible for individuals to benefit

and leverage them. Box.net is a Cloud Storage

provider, which is used by both individuals and

Fortune 500 companies. The “pay-per-use” model

works great for individuals and corporations.

No. Vendor Name

Description

1

Amazon

Web Services

Amazon Web Services offers a complete set of

infrastructure and application services that enable you to

run virtually everything in the cloud: from enterprise

applications and big data projects to social games and mobile apps. One of the key

benefits of cloud computing is the opportunity to replace up-

front capital infrastructure expenses with low variable costs that scale with your

business.

2

Bluelock

BlueLock is an Infrastructure- as-a-Service company that

specializes in Cloud Computing and disaster recovery. The company provides Virtual Cloud

Computing through Infrastructure-as-a-Service

(IaaS) where clients subscribe monthly to just the right amount of computing,

storage and bandwidth capacity needed today with

the ability to grow “on demand” in the future.

3

GoGrid

GoGrid’s cloud hosting platform provides automated provisioning of infrastructure over the Internet. You can provision and scale virtual

and physical servers, storage, networking, load balancing,

and firewalls in real time across multiple data centers

using a web-based management console or

GoGrid’s API.

4

IBM

Cloud infrastructure as a service (IaaS) from IBM

enables speed and dexterity for the faster delivery of new offerings and services. IaaS

frees up resources your organization would otherwise

use to house, run and maintain the equipment. This approach is best suited for

resource intensive activities, such as development and

http://aws.amazon.com/



http://www.bluelock.com/

http://www.gogrid.com/

http://www.ibm.com/cloud-computing/us/en/iaas.html


39

12

Citrix

Citrix CloudPlatform provides the latest and most advanced

open source software platform to build highly

scalable and reliable cloud computing environments.

Conclusion In this paper, we have introduced IAAS

architecture and the various advanced techniques to

improve the performance of IAAS architecture. In

some of the architectures we have introduced

PODS and we have to aggregate as many

workloads in each pod depending on some factors. How many workloads needs to be aggregated

based on public cloud or private cloud ,but the

main issue is to prototype and test your initial pods

to determine their scalability & capacity. The

Cloud Infrastructure component has its own

vulnerable issues which would impact the whole

cloud’s computing security. An IAAS security

model needs to be proposed for assessing and

enhancing security in each layer of IAAS delivery

model. Our future research focus will be on two

directions to provide confidentiality, integrity, and

secure infrastructure management for IAAS service. First, extending techniques such as

proposed in TCCP into IAAS layer to improve

confidentiality and integrity of VMs. Second,

integrating TCCP with secure resources

management schemes to get more controlled

isolation environment. Finally, a prototype will be

implemented to demonstrate the system feasibility

and performance.

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5

Openstack

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[36] Making Infrastructure-as-a-Service in the

Enterprise a Reality

Mrs. B. Susrutha working

as an Assistant Professor in Geethanjali Institute of

Science and Technology pursued her B.tech degree

in Computer science & Engineering from Narayana

Engineering College, Nellore during the AY 2002-

2006.She pursued her M.tech in CS from

PBRVITS,Kavali, Affiliated to JNTUA.She is

having 5.5 years of Teaching experience and 3

Years of IT industry experience as a SAP

Basis/Security Consultant.

Mr K.VenkataRamana

working as an Assistant Professor in Geethanjali

Institue of Science and Technology received the

B.tech degree in Computer Science & Engineering

from Gokula Krishna College of Engineering,

Sullurpet in 2006.He pursued M.Tech in CSE in AVS College of Engineering &Technology,

Venkatachalam Affiliated to JNTUA

http://www.springerlink.com/content/v4q33816117

http://doi.acm.org/10.1145/1165389.945450

http://doi.acm.org/10.1145/1165389.945450

http://dx.doi.org/10.1109/VTDC.2006.4

http://dx.doi.org/10.1109/VTDC.2006.4


42

Study and Comparision of Mechanical Properties,

Durability and Permeability of M15, M20, M25 Grades of Pervious Concrete with Conventional Concrete

Sai Sindhu K, Suresh Babu T

Sai Sindhu K M. Tech student, IV semester, Visvodaya Engineering College, Kavali

Dr. Suresh Babu T Professor and Head, Department of Civil Engineering, Visvodaya Engineering College,

Kavali

Abstract Pervious concrete is a special type of concrete with high porosity. It is used for concrete flatworks application that allow the water to pass through it, thereby reducing the runoff from a site and allowing ground water recharge. The high porosity is attained by a highly interconnected void content. Typically pervious concrete has water to cementisious material ratio of 0.28 to 0.4.The mixture is composed of cementisious materials, coarse aggregates and water with little to no fine aggregates. Addition of a small amount of fine aggregates will generally reduce the void content and increase the strength. The present project deals with the study and comparison of mechanical properties, workability density and permeability of different grades of pervious concrete (M15, M20, M25).

Keywords: pervious concrete, no fines, hyper plasticizer, permeability, Sulphate attach.

1. Introduction One of the disadvantages of concrete is the high self weight of concrete. Density of normal concrete is in the order of 2200 to 2600 kg/m3. This heavy self weight will make it to some extent an uneconomical structural material. Attempts have been made in the past to reduce the self weight of concrete to increase the efficiency of concrete as a structural material. The light weight concrete density varies from 300 to 1850 kg/m3. Light weight concrete has become more popular in recent years and have more advantages over the conventional concrete.

Pervious concrete is nothing but no fines concrete, which is also known as porous, gap

graded or permeable concrete mainly consists of normal Portland cement, CA, water. In

which FA are not existent or present in very small amount i.e < 10% by weight of the total

aggregates. In general, for making porous concrete, we will use the aggregates of size which passes through 12.5mm sieve and retained on 10mm sieve. In this project we have taken single size aggregates i.e 12.5mm. the single size aggregates make a good no-fines concrete, which addition to having large voids and hence light in weight, also offers architecturally attractive look.

Fig 1: test specimens

43

GIST RESEARCHER In-house Journal of Science and Technology, VOLUME-1, ISSUE-1, JAN-2015

Common applications for pervious concrete are parking lots,

side walls, path ways, tennis courts, slope stabilization, swimming pool decks, green house floors, drains, highway

pavements. Generally which is not used for concrete

pavements for high traffic and heavy wheel loads. structural

advantages.

2. Aim and Objectives The aim of the research is to study the strength, durability and permeability of pervious concrete for different grades (M15, M20, M25). The objectives include

To study the workability of concrete. To study the density of concrete. To study the mechanical properties such as compressive,

tensile and flexural strength of concrete. To study the durability of concrete by sulphate attach

(by using MgSo4 curing). To study the permeability of concrte.

3. Materials The present investigation the following materials were used: Ordinary Portland Cement of 53 Grade cement

conforming to IS: 169-1989 Fine aggregate and coarse aggregate conforming to IS:

2386-1963.

Water. Hyper plasticizer (ECMASHP-902)

3.1 Cement

Ordinary Portland Cement of 53 Grade of brand name Ultra

Tech Company, available in the local market was used for

the investigation. Care has been taken to see that the

procurement was made from single batching in air tight

containers to prevent it from being effected by atmospheric

conditions. The cement thus procured was tested for physical

requirements in accordance with IS: 169-1989 and for chemical requirement in accordance IS: 4032-1988. The

physical properties of the cement are listed in Table –

Table 1: Properties of cement

physical requirements such as gradation, fineness modulus, specific gravity and bulk density in accordance with IS: 2386-1963. The individual aggregates were mixed to induce the required combined grading. the particular gravity and water absorption of the mixture are given in table.

Table 3: Properties of coarse aggregates

Specific Gravity of coarse aggregate 2.60

Water absorption 1%

Water Potable water fit for drinking is required to be used in the concrete and it should have pH value ranges between 6 to 9.

Hyper Plasticizers

Hyper plasticizers are standard chemical admixtures for

concrete employed in the reduction of water to cement

quantitative relation while not moving workability, and to

avoid particle saggregation within the concrete mixture.

These are called high vary water reducers (HRWR),

fluidifiers, and dispersants as these are capable of reducing

water to cement quantitative relation by forty.0%. These

chemical admixtures are additional within the concrete

simply before the concrete is placed. These admixtures facilitate to enhance strength and flow characteristics of the

concrete. In this project we used ECMASHP-902 as

admixture with an amount of 0.2% by weight of cement.

Mix proportions as Per ACI 211.1-91

Table 4: Mix proportions for M15 grade of concrete

Sl. No Properties Test

results IS: 169-1989

1. Normal consistency 0.32

2. Initial setting time 60min Minimum of 30min

3. Final setting time 320min Maximum of

600min

4. Specific gravity (a) 3.14

Fine Aggregates River sand locally available in the market was used in the investigation. The aggregate was tested for its physical requirements such as gradation, fineness modulus, specific gravity in accordance with IS: 2386-1963.The sand was surface dried before use.

Table 2: Properties of Fine Aggregates Table 6: Mix proportions for M25 grade of concrete

Fineness modulus 2.4

Specific Gravity of fine aggregate 2.55

Free moisture 2%

Coarse Aggregates Crushed aggregates of less than 12.5mm size produced from local crushing plants were used. The aggregate exclusively passing through 12.5mm sieve size and retained on 10mm sieve is selected. The aggregates were tested for their

materials

Proportions for

Conventional

(kg/m3)

Proportions for

No fines concrete

(kg/m3)

Cement 277.7 277.7

Fine aggregates 642.04 0

Coarse aggregates 1193.94 1193.94

Water cement ratio by mass

0.3 0.3

Admixture(ml) 55.54 55.54

Table 5: Mix p

materials

roportions for M20 gr Proportions for

Conventional

(kg/m3)

ade of concrete Proportions for

No fines concrete

(kg/m3)

Cement 380 380



Water cement ratio by mass

0.3 0.3

Admixture(ml) 76 76

materials

Proportions for

Conventional (kg/m3)

Proportions for

No fines concrete (kg/m3)

Cement 452.38 452.38



Water cement ratio by

mass 0.3 0.3

Admixture(ml) 90.47 90.47

44


4 Sulphate Attack To determine the resistance of various concrete mixtures to sulphate attack, the residual compressive strength of concrete mixtures of cubes immersed in alkaline water having 5% of Magnesium sulphate (MgSO4) by weight of water was found. The concrete cubes which were cured in MgSO4 were removed from the curing tank and allowed to dry for one day. The weights of concrete cube specimen were taken.. The resistance of concrete to sulphate attack was found by the % loss of weight of specimen and the % loss of compressive strength on immersion of concrete cubes in 3- 5% magnesium sulphate water.

5 Experimental Results Workability: Results obtained from compaction factor test showing that the workability of concrete

Table 7: Compaction factor for conventional concrete and No fines concrete

Grades Of Concrete

Compaction Factor

Conventional Concrete No Fines Concrete

M15 0.8 0.85

M20 0.84 0.89

M25 0.87 0.92

Fig 2: Workability variation of conventional and pervious concrete for different grades

Compressive Strength These results are obtained by testing the total 6 specimens for 7 days and 28 days and by considering the average of the test results and that are tabulated in table

Table 8: compression strength of No fines concrete cubes cured in water and cured in MgSo4.

Table 9: compression strength of conventional concrete cubes cured in water and cured in MgSo4.

Fig 3: Seven days compressive strength variation of conventional and No fines concrete cured in water and cured in MgSo4.

Fig 4: Twenty eight days compressive strength variation of conventional And No fines concrete cured in water and cured in

MgSo4.

Split Tensile Strength: These results are obtained by testing the total 6 specimens for 7 days and 28 days and by considering the average of the test results that are tabulated in table

Table 10: Split tensile strength of No fines concrete cylinders cured

in water and cured in MgSo4.

Table 11: Split tensile strength of conventional concrete cylinders

cured in water and cured in MgSo4.

Grades Of Concrete

Compressive Strength(N/MM2)

Cured In Water Cured In MgSo4

7 Days 28 Days 7 Days 28 Days

M15 14.6 19.1 13.03 18.8

M20 17.26 25.44 15.6 24.03

Grades Of Concrete

Split Tensile Strength(N/mm2)



M15 0.98 1.22 0.84 1.08

M20 1.17 1.57 1.04 1.39

M25 1.41 2.05 1.29 1.82

Grades Of Concrete

Compressive Strength(N/mm2)



M15 11.02 16.32 8.96 15.1

M20 14.98 20.79 12.82 18.74

M25 19.86 24.4 17.2 25.53

Grades Of Concrete

Split Tensile Strength(N/mm2)



M15 2.11 3.26 1.65 2.92

M20 3.19 4.7 2.93 3.99

M25 4.04 5.2 3.11 4.82

45


M25 21.3 30.88 19.3 28.87

46


Fig 5: Seven days split tensile strength variation of conventional And No fines concrete cured in water and cured in MgSo4.

Fig 6: Twenty eight days split tensile strength variation of conventional And No fines concrete cured in water and cured in

MgSo4.

Flexural Strength These results are obtained by testing the total 6 specimens for 7 days and 28 days and by considering the average of the test results that are tabulated in table

Table 12: Flexural strength of No fines concrete beams cured in water and cured in MgSo4.

Grades Of Concrete

Flexural Strength(N/mm2)



M15 3.79 5.18 3.13 4.91

M20 6.68 7.36 6.09 7.06

M25 8.89 10.28 8.26 9.92

Table 13: Flexural strength of conventional concrete beams cured in water and cured in MgSo4.

Fig 7: Seven days flexural strength variation of conventional And No fines concrete cured in water and cured in MgSo4.

Fig 8: Twenty eight days flexural strength variation of conventional

And No fines concrete cured in water and cured in MgSo4.

Density of Concrete

The density of concrete cubes for different grades of

conventional and no fines concrete are shown below.

Table 14: Density of conventional concrete and No fines concrete

Grade Of Concrete

Density Of Concrete (kg/m3)

Conventional Concrete

No Fines Concrete

M15 2340 1612

M20 2375 1656

M25 2394 1685

Permeability Test These results are obtained by testing the total 9 specimens for conventional and no fines concrete by varying the pressure differences and the results are tabulated in the table.

Table 15: Permeability of conventional concrete and No fines concrete

Pressure Difference

(Pa)

Permeability Of Conventional Concrete(cm/sec) Permeability Of No Fines Concrete (cm/sec)

M15 M20 M25 M15 M20 M25

5 5.6X10-14 3.2X10-14

1.39 X10-14 6.6 X10-3

1.01X10-3 9.42 X10-4

10 1.8X10-14 9.48 X10-15

7.47 X10-15 1.2 X10-3

8.2 X10-4 6.01 X10-4

15 8.6X10-15 6.23 X10-15

3.25 X10-15 8.9 X10-4

5.4 X10-4 2.9 X10-4

Grades Of Concrete

Flexural Strength(N/mm2)



M15 5.43 7.1 4.51 6.37

M20 8.44 10.12 7.32 9.55

M25 10.37 12.57 9.03 11.12


46

Discussion

Compressive Strength

A decrease in the compressive strength of M15,M20 and M25

grades of no fines concrete by 18.2%, 14.5% and12.6%

respectively is found compared to the conventional concrete.

The computed values of the compressive strength of both

conventional and no fines concrete establish that

compressive strength of no fines concrete is less than that of conventional concrete.

Split Tensile Strength

It is evident from the study that the tensile strength of M15, M20 and M25 grades of no fines concrete is decreased by 40.2%, 38.4% and 36.2% respectively in comparison with the conventional concrete. The calculated split tensile strength values of both conventional and no fines concrete prove that the tensile strength of no fines concrete is less than that of conventional concrete.

Flexural Strength Observations conclude that the flexural strength of M15, M20 and M25 grades of no fines concrete is decreased by 29.9%, 27.6% and 24.6% respectively when compared to the conventional concrete. Illustrative computation of flexural strength values of both conventional and no fines concrete prove that flexural strength of no fines concrete is less than that of conventional concrete.

Density of Concrete

It is observed that the density of M15, M20 and M25 grades of no fines concrete is decreased by 31.1%, 30.2% and 29.6% as against that of conventional concrete. The computed density of no fines concrete is noted to have decreased in comparison with that of conventional concrete.

Permeability It has been observed that coefficient of permeability of M15, M20 and M25 grades of no fines concrete is increased by 82.4%, 79.6% and 72.8% respectively in comparison with the conventional concrete. Computations establish that the coefficient of permeability

values is more for no fines concrete than the conventional

concrete.

Workability Form the calculated workability values it is observed that for M15, M20 and M25 grades of no fines concrete are increased by 5.8%, 5.6% and 5.4% respectively when compared to the

conventional concrete.

Durability by Sulphate Attack

Compressive Strength: (A) No Fines Concrete

The compressive strength of M15, M20 and M25 grades of no

fines concrete is decreased by 15.5%, 16.2% and 12.8%.

(B) Conventional Concrete The spilt tensile strength of M15, M20 and M25 grades of no fines concrete is decreased by 14.8%, 13.7% and 15.05%respectively.

Split Tensile Strength

(A) No Fines Concrete

The spilt tensile strength of M15, M20 and M25 grades of no fines concrete is decreased by 11.4%, 11.46% and 11.21% respectively.

(B) Conventional Concrete

The spilt tensile strength of M15 M20 and M25 grades of no fines concrete is decreased by 10.42%, 11.5% and 9.4% respectively.

Flexural Strength

(A) No Fines Concrete

The flexural strength of M15, M20 and M25 grades of no fines concrete is decreased by 11%, 10.1% and 8.2% respectively.

(B) Conventional Concrete

The spilt tensile strength of M15, M20 and M25 grades of no fines concrete is decreased by 10.28%, 8.5% and 11.5% respectively.

Conclusions The following conclusions are drawn based on the experimental investigations on compressive strength, split tensile, flexural, durability, permeability considering the

“environmental aspects” also:

Pervious concrete has less strength than conventional

concrete by 18.2% for M15, 14.5% for M20 and 12.6%

for M25.

Similarly the tensile and flexural strength values are also comparatively lower than the conventional concrete by 30%.

Though the pervious concrete has low compressive,

tensile and flexural strength it has high coefficient of

permeability hence the following conclusions are drawn based on the permeability, environmental effects and

economical aspects.

It is evident from the project that no fines concrete has

more coefficient of permeability. Hence, it is capable of capturing storm water and recharging the ground water. As a result, it can be ideally used at parking areas and at residential areas where the movement of vehicles is very moderate.

Further, no fines concrete is an environmental friendly

solution to support sustainable construction. In this

project, fine aggregates as an ingredient has not been

used. Presently, there is an acute shortage of natural

sand all around. By making use of FA in concrete,

indirectly we may have been creating environmental

problems. Elimination of fines correspondingly

decreases environment related problems. In many cities diversion of runoff by proper means is

complex task. Use of this concrete can effectively control the run off as well as saving the finances invested on the construction of drainage system. Hence, it can be established that no fines concrete is very cost effective apart from being efficient.


References 1. Aguado A. he told that highly permeable materials

provide drainage and noise-absorption properties that are useful in pavement top layers, 1999.

2. Yang J, Jiang G. In this paper, a pervious concrete

pavement material used for roadway is introduced.

Using the common material and method, the strength of

the pervious concrete is low, 2003.

3. Mulligan AM. This thesis investigated prior studies on the compressive strength on pervious concrete as it relates to water-cement ratio, aggregate-cement ratio, aggregate size, and compaction, 2005.

4. Valavala S, Montes F. They concluded that Pervious

concrete is an alternative paving surface that can be used

to reduce the nonpoint source pollution effects of storm

water runoff from paved surfaces, 2006.

5. Suleiman M, Kevern J. this paper summarizes a study

performed to investigate the effects of compaction

energy on pervious concrete void ratio, compressive

strength, tensile strength, unit weight, and freeze-thaw

durability, 2007.

6. Wolfersberger C. in this paper, Pervious concrete usually requires much less maintenance. But inspection

and some attention will keep it working for many years,

2008. 7. Wang K. This paper describes the current state of

practice in pervious concrete placement methods and presents results from a laboratory-based study to compare various placement practices and develop QA/QC criteria, 2008.

8. Meininger RC. in this paper Conclusions are drawn

regarding the percentage of air voids needed for

adequate permeability, the optimum water-cement ratio

range, and the amounts of compaction and curing

required, 2009.

47


48

Closed Loop Speed Control of BLDC Motor with PI Controller under Different Loading Conditions

Murali Dasari* , M.Ashok**

*Assistant Professor, Department of EEE, Geethanjali Institute Of Science & Technology, SPSR Nellore,

**Assistant Professor, Department of EEE, Geethanjali Institute Of Science & Technology, SPSR Nellore,

Abstract- In the recent past, variable speed driving

systems have sprouted in various small scale and large

scale applications like automobile industries, domestic

appliances etc. The usage of green and eco friendly

electronics are greatly developed to save the energy

consumption of various devices. This lead to the

development in Brushless DC motor (BLDCM). The

usage of BLDCM enhances various performance factors

ranging from higher efficiency, higher torque in low-

speed range, high power density ,low maintenance and

less noise than other motors. The BLDCM can act as an

alternative for traditional motors like induction and

switched reluctance motors. In this paper the simulation

is carried out for 120 degree mode of operation. The test

results shows that the performance of BLDCM which

are highly acceptable. Finally Proportional and Integral

controller (PI controller) is applied for closed loop

speed control under various loading conditions.

Index Terms- Brushless DC motor (BLDCM), bipolar starting, unipolar starting drive, PI controller, 120 degree mode.

I INTRODUCTION

Using of Permanent Magnet in electrical machines have

so many benefits and advantages then electromagnetic

excitation machines these are zero excitation losses result

in high efficiency, simple construction, low cost less

maintenance and high torque or high output power per unit

volume . In early 19th century permanent magnet excitation

system was used for first time in electrical machines. The

performance of this machine was very poor due to poor

quality of hard magnetic material, this made it less usable.

Rare earth permanent magnets improve the power density

and dynamic performance of the machine. Induction motors

are most popular machine in the 20th century due to its

simple construction, less price, reasonable reliability and

low maintenance. Due to small air gap, lower efficiency

and low power factor than synchronous machine make

synchronous machine prevalent in industrial applications.

Due to high power to weight ratio, high torque, good

dynamic control for variable speed applications, absence of

brushes and commutator make Brushless dc (BLDC)

motor, best choice for high performance applications. Due

to the absence of brushes and commutator there is no

problem of mechanical wear of the moving parts [2], [3].

As well, better heat dissipation property and ability to

operate at high speeds [4] make them superior to the

conventional dc machine.

However, the BLDC motor constitutes a more difficult

problem than its brushed counterpart in terms of modeling

and control system design due to its multi-input nature and

coupled nonlinear dynamics. Due to the simplicity in their control, Permanent-magnet brushless dc motors are more

accepted used in high-performance applications. In many

of these applications, the production of ripple-free torque

is of primary concern. There are three main sources of

torque ripple production in BLDCMs: cogging torque,

reluctance torque, and mutual torque. Cogging torque is

created by the stator slots interacting with the rotor

magnetic field and is independent of stator current

excitation. Reluctance torque is caused by the variation in

phase inductance with respect to position. Mutual torque is

created by the mutual coupling between the stator winding current and rotor magnetic field. In general, surface-

mounted magnets are used in many high-performance

BLDCM’s. Because the permeability of the magnet

material is nearly equal to that of air, the effective air gap

is enlarged by the magnet. This fact ensures minimum

armature effect on the rotor field from the stator currents.

If a BLDCM is designed with low saliency and either the

stator slots or rotor magnets are skewed by one slot pitch,

the effects of the first two torque components can be

greatly reduced. Therefore, if the waveforms of the phase

back EMF and phase current are perfectly matched, torque

ripple is minimized and the mutual torque component is maximized.

Conventionally controller are most popular controllers

and widely used in most closed loop appliances however

recently there are many researchers reported successfully

adopted PI Controller to become one of intelligent

controllers to their application, with respect to their

successful methodology execution. This kind of

methodology implemented in this paper is using PI

controller with feed back by introduction of speed output

respectively. The introduction of speed output in the circuit

will be fed to PI controller to give appropriate measure on steady state signal. For this propose the PI controller serves

as intelligent controller.

PI Control is one of the most successful of today’s

technology for developing sophisticated and advanced

control system applications. With it aid complex

requirement so may be implemented in amazingly

simple, easily minted and inexpensive controllers. The


49

past years have witnessed a rapid growth in number and

variety of application of PI control. The application

ranges from consumer products such as cameras,

camcorder, washing machines, and microwave ovens to

industrial process control, medical instrumentation, and

decision- support system. Many decision-making and

problem solving tasks are too complex to be

understood quantitatively however, people succeed by using knowledge that is imprecise rather than precise. In

this paper finally closed loop speed control is done by

using PI controller under various loading conditions.

II. PRINCIPLE OF OPERATION

In conventional BLDC motor during bipolar operation,

at any time across DC bus, two phases come in series. Only

half of the DC bus voltage is applied to each phase,

resulting in addition of torque constant on both phases there

by achieving high starting torque. But speed will be

limited. To get higher speed, full DC bus voltage is to be

applied to each phase. This can be achieved in unipolar

operation, where each phase conducts only in one direction

which in turn reduces the starting torque. Thus in order to

get high torque, motor should operate in bipolar mode and to get high speed motor should operate in unipolar mode.

Shifting of modes between unipolar and bipolar operation

is achieved based on speed requirement. The proposed

inverter consists of 4 legs. The 3 phases of BLDC motor is

connected to first 3 legs and neutral point is connected to

the fourth leg as shown in Fig.1. In bipolar operation first 3

legs are active and the 4th leg is inactive. Here we have

considered only bipolar operation.

Fig. 1 Proposed Inverter Circuit

By switching on Q1 and Q4, phase A conducts in

positive direction and phase B conducts in negative

direction. By switching off Q4 and switching on Q6, a free-

wheeling path is established through phase B, diode D3,

switch Q1 and Phase A as shown in Fig. 2.

By switching off Q1 and switching on Q3 and Q6, the free-wheeling energy in positive conducting phase A flows

through resistor Rs, D2, phase A, phase C, and Q6, as shown in Fig. 3.

Fig. 2 Free-wheeling of negative conducting B Phase

Fig. 3 Free-wheeling of positive conducting A phase

III MODELLING of BLDC MOTOR

Modeling of a BLDC motor can be developed in the

similar manner as a three phase synchronous machine.

Since its rotor is mounted with a permanent magnet,

some dynamic characteristics are different. Flux linkage from the rotor is dependent upon the magnet. Therefore,

saturation of magnetic flux linkage is typical for this kind

of motors. As any typical three phase motors, one structure

of the BLDC motor is fed by a three phase voltage source

as shown in Fig. 4. The source is not necessary to be

sinusoidal. Square wave or other wave- shape can be

applied as long as the peak voltage is not exceeded

the maximum voltage limit of the motor. Similarly, the

model of the armature winding for the BLDC motor is

expressed as follows.

(1)

(2)


50

Or in the compact matrix form as follows.

Where

is the arma

M is

the mutual inductance

Armature resistance in ohm

Are the terminal phase voltages in volts

(3)

(4)

The resultant torque, TE, can be obtained by the following expressions.

(9)

(10)

(11)

(12)

With the Newton’s second law of motion, the angular

motion of the rotor can be written as follows.

(13)

Motor input current in amperes

Are the motor back emf in volts

P in the matrix represents

Due to the permanent magnet mounted on the rotor, its back emf is trapezoidal as shown in Fig. 5. The expression

of back emf must be modified as expressed in

(5)

(6)

(7)

Where KE is the back emf constant and ω is the

mechanical speed of the rotor.

Where TL load torque in N-m J rotor inertia in [kgm2] B damping constant

Ea

ωt

Ia

Eb

Ib

Ec

Ic

30 60 90 120 150 180 210 240 270 300 330 360

½ Vdc

½ Vdc

R L-M

R L-M

R L-M

Fig.5 BLDC Motor back emf and the motor phase currents

IV. PI CONTROLLER

PI controllers were developed because of the desirable

property that systems with open loop transfer functions

have zero steady state error with respect to a step input. A

PI controller is a special case of the PID controller in which

the derivative (D) of the error is not used. PI controller forms control signal in the following way:

Fig. 4 BLDC Motor Control System

The permanent magnet also influences produced torques due to the trapezoidal flux linkage. Given that KT is the torque constant. The produced torques

. /ω (8)

Where: Ti -Integral time constant of PI controller.

Ea

Eb

Ec


51

Fig.6. Basic block of a PI controller

The controller output is given by

dt

Where ∆ is the error or deviation of actual

measured value (PV) from the set point (SP).

To obtain the Kp and Ki values PI controller is tuned, general approach for tuning is 1. Initially have no integral gain (TI large)

2. Increase KP until get satisfactory response

3. Start to add in integral (decreasing TI) until the steady

state error is removed in satisfactory time (may need to

reduce KP if the combination becomes oscillatory)

V. SIMULATION RESULTS

Fig. 7 SIMULINK model of BLDC motor

Fig.7 shows the Matlab/Simulink model of BLDC

motor with closed loop control. This Model consists of four

sub blocks named as torque – speed block, back emf block,

converter block and torque block.

Fig.9 Trapezoidal back emf loop of the BLDC motor

Fig.9 shows the Trapezoidal back emf block of the

BLDC motor. The input of this block is angular speed and

rotor angle, and output is back emf.

Below figure 10 shows the SIMULINK model of the

converter block in the BLDC motor.

Fig. 10 SIMULINK model of the converter block

The inputs of the converter block is speed, rotor

position, back emfs and voltage, the output of the block is

current. Here simulation is carried out for four cases. In

case 1 BLDC with open loop control, Case 2 BLDC with

Closed loop PI Control on No Load, Case 3 BLDC with Closed loop PI Control on Increasing Load, Case 4 BLDC

with Closed loop PI Control on Decreasing Load.

Table I: The test parameters of the motor taken for simulation are given

below

Parameters Value

Rated Power 1000 W

Rated Voltage 100V

Resistance of the stator (R) 0.2ohm

Inductance of the stator (L) 0.01H

Moment of Inertia (J) 0.01Kg-m/Sec2

Back emf constant (Kb) 0.5V/rad/s

Load Torque (TL ) 1N-m

Motor Torque constant (Kt) 0.5N-m

No of Pole Pairs 4

A. Case 1 - BLDC with open Loop Control

3

2 .5

4

x 10

Fig: 8 SIMULINK model of the Torque speed loop

Fig. 8 shows the SIMULINK model of the Torque

speed loop in the BLDC motor circuit. The input of the

block is load torque and electromagnetic torque. The output

of the block is the rotor angle and angular speed.

2

1 .5

1

0 .5

0 0 0 .002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02

Time in sec

Fig. 11 Output waveforms of the speed of the motor

SP +

e(t)

-

PV

+

-

MV

P K P e(t)

I KI e()d

Process

Spee

d in

rpm


52

Tor

que

in N

/m

Fig. 11 shows the no load speed of the motor with open

loop control. At no load with open loop control motor is

achieving a speed of 25000 RPM.

3

2

1

0

-1

-2

Fig. 15 shows the no load speed of the motor with PI

control. Here reference speed is taken as 12000 rpm the

motor reaches the reference speed very quickly with PI

control. 1.5

1

0.5

0

-0 .5

-3 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02

Time in sec

Fig.12 Back EMF of the BLDC motor

Fig. 12 shows the trapezoidal back emf wave form.

Here we have considered 120 degree mode of operation.

-1

-1.5

0.5

0.4

0 0.005 0.01 0.015 0.02 0.025 0.03

Time in sec


0.3

0.5

0.4

0.3

0.2

0.1

0

-0 .1

-0 .2

-0 .3

0.2

0.1

0

-0 .1

-0 .2

-0 .3

-0 .4

-0 .5

0 0.005 0.01 0.015 0.02 0.025 0.03

ime in sec

-0 .4

-0 .5

0 0.0 0 2 0.0 0 4 0.0 0 6 0.0 0 8 0.0 1 0.0 1 2 0.0 1 4 0.0 1 6 0.0 1 8 0.02

Ti m e i n se c

Fig.13 Output waveforms of the currents.

-4

x 1 0 6

5

Fig.17 Output waveforms of the currents

Fig.13 shows the three phase currents of motor. Initially

current is high, once the speed reaches steady value then

the current will decreases. 3

-4

x 1 0 6

5

4

3

2

1

0

0 0.0 0 2 0.0 0 4 0.0 0 6 0.0 0 8 0.0 1 0.0 1 2 0.0 1 4 0.0 1 6 0.0 1 8 0.0 2

Ti m e i n se c

Fig.14 Output waveform of the torque of the motor

Fig.14 shows the electromagnetic torque generated by

the motor. Initially torque is high, once the speed reaches

steady value torque will decreases.

B. Case 2 - BLDC with Closed Loop PI control on No

Load

2

1

0 0 0.0 0 5 0.0 1 0.0 1 5 0.0 2 0.0 2 5 0.0 3

Ti m e i n se c




steady value torque will decreases since it is no load case

so torque is small value equivalent to friction torque.

C. Case 3 - BLDC with Closed Loop PI control for

Increasing Load

12000

10000

8000

6000

12000

10000

8000

4000

2000

0

6000

4000

2000

-2000

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02

Time in sec


0

0 0.005 0.01 0.015 0.02 0.025 0.03

Time in sec


Fig. 19 shows the speed of the motor with PI control.

Here reference speed is taken as 12000 rpm the motor

reaches the reference speed very quickly with PI control.

Spee

d in

rpm

Cur

rent

s in

am

ps

Back E

mf

Tor

que

N/m

spee

d in rp

m

Cur

rent

s Ba

ck E

mf

4


53

qu

Here load torque is increasing from 0.1 to 0.2 N-m at time

t=0.01 sec. At this time there is a small decrease in the

speed of the motor. 1.5

1

0.5

0

-0 .5

-1

Fig. 23 shows the speed of the motor with PI control.

Here reference speed is taken as 12000 rpm the motor

reaches the reference speed very quickly with fuzzy

control. Here load torque is decreasing from 0.2 to 0.1 N-m

at time t=0.01 sec. At this time there is a small increase in

the speed of the motor.

0.5

0.4

0.3

-1 .5

0.5

0.4

0.3

0.2

0.1

0

-0 .1

-0 .2

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02

Time in sec


0.2

0.1

0

-0.1

-0.2

-0.3

-0.4

-0.5

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02

Time in sec


-0 .3

-0 .4

-0 .5

0 0.0 0 2 0.0 0 4 0.0 0 6 0.0 0 8 0.0 1 0.0 1 2 0.0 1 4 0.0 1 6 0.0 1 8 0.0 2

Ti m e i n se c



current is high, once the speed reaches steady value current

will decreases to rated value. At t=0.01 sec load torque is

increased to double the value so current also increase by

same percentage.



steady value torque will decreases to rated value. At t=0.01

sec load torque is increased to double the value so

Electromagnetic torque also increase by same percentage -4


current is high, once the speed reaches steady value, current will decreases to rated value. At t=0.01 sec load torque is

decreased to half the value so current also decreased by

same percentage. -4

x 10 6

5

Tor 4

3

2

1

0

x 1 0 6

5

4

3

2

1

0 0 0.0 0 2 0.0 0 4 0.0 0 6 0.0 0 8 0.0 1 0.0 1 2 0.0 1 4 0.0 1 6 0.0 1 8 0.0 2

Ti m e i n se c


D. Case 4 - BLDC with Closed Loop PI control for

Decreasing Load 12000

10000

8000

6000

4000

2000

0

-2000 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02

Time in sec


0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02

Time in sec




steady value torque will decreases to rated value. At t=0.01

sec load torque is decreased to half the value so Electromagnetic torque also decreases by same percentage.

V. CONCLUSION

Permanent-magnet brushless dc motors is more widely

used in high-performance applications because of their

higher efficiency, higher torque in low-speed range, high

power density, low maintenance and less noise than other

motors. In this paper closed loop speed control of BLDC is

carried out using PI controller and the simulation results are

presented for the performance of the motor. The results

show that the dynamic performance of the motor is quite

satisfactory. Simulation results are shown for various

loading conditions.

Spee

d in rp

m

Cur

rent

in a

mps

Ba

ck E

mf

Tor

que

in N

/m

Currents

in a

mp

e in N/m


54

VI. REFERENCES

[1] R. Civilian, and D. Stupak, "Disk drive employing multi mode

spindle drive system," US patent 5471353, Oct 3, 1995.

[2] G.H. Jang and M.G. Kim, “A Bipolar-Starting and Unipolar-Running

Method to Drive an HDD Spindle Motor at High Speed with Large

Starting Torque,” IEEE Transactions on Magnetics, Vol. 41, no.2, pp.

750-755, Feb. 2005.

[3] E.Grochowski and R.F. Hyot,”Future trends in hard disk drives”,IEEE

Tran. On Magnetics, vol.32, no.3, pp1850-1854, May 1996.

[4] J.D.Ede, ,Z.Q.Zhu and D.Howe,”Optimal split ratio control for high

speed permanent magnet brushless DC motors”, in Proc.5th

Int,Conf..Electrical Machines and Sytems’,vol.2,Aug 2001,pp 909-912

[5] S.X.Chen, M.A.Jabbar, O.D. Zhang and Z.J.Lie,”New Challenge:

Electromagnetic design of BLDC motors for high speed fluid film bearing

spindles used in hard disk drives”,IEEE Trans. Magnetics ,vol32,no.5,

pp3854-3856,Sep. 1996.

[6] T.Kenzo and S. Nagamori, Permanent Magnets and Brushless DC

Motors, Tokyo,Japan,Sogo Electronics,1984.

[7] J.R.Hendershot and Miller,”Design of Brushless Permanent Magnet

Motors, Oxford Univ. Press,1994

[8] S.W.Cameron.”Method and apparatus for starting a sensorless

polyphase dc motors in dual coil mode and switching to single coil mode

at speed”, U.S.Patent 5455885,, Nov.28,1995

[9] T.Gopalaratnam and H.A.Toliyat, “A new topologyfor unipolar

brushless dc motor drives”,. IEEE TransPower Electronics, vol.18,No.6,

pp 1397-1404,Nov.2003.

[10] Bhim Singh and Sanjeev Singh, “State of art on permanent magnet

brushless Dc motor Drives”, Journal of Power Electronics”, vol.9 no.1 pp

1-17 Jan.2009.

[11] Maxon Precision Motors Inc., http://www.maxonmotor.com.

http://www.maxonmotor.com/

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