Vol. 1, Issue 1 - 2017 AUTOMATIC CONTROL SYSTEM FOR THE

International Journal on Recent Innovation in Instrumentation & Control Engineering

Vol. 1, Issue 1 - 2017

© Eureka Journals 2017. All Rights Reserved. www.eurekajournals.com

AUTOMATIC CONTROL SYSTEM FOR THE BLDC MOTOR

A2212/13T USING ARDUINO UNO PLATFORM

MS MAZINDER*, S BORDOLOI

*, PK BORDOLOI

*

ABSTRACT

An Automatic Control System for the BLDC motor A2212/13T using Arduino Uno

platform is designed to study the performance of the motor. The present work

involves a comprehensive study of the motor with open-loop, close-loop and PID

controller modes with analysis of the performance parameters like speed, supply

voltage, torque, load power etc under varying load conditions. A detailed study

of the control components like optical pick-up, electronic speed controller (ESC)

and microcontroller (ATmega328p/ Arduino UNO) is also covered.

KEYWORDS: BLDC Motor, Electronic Commutation, Optical Pick-Up, Arduino

Uno, PWM.

INTRODUCTION

BLDC motor stands for Brushless Direct Current

motor. As the name implies, BLDC motors do not

use brushes for commutation; instead, they are

electronically commutated. They are one of the

motor types rapidly gaining popularity.

They are designed for high speeds, long life, and

high power density. They are ideal for stop/ go

and continuous running applications, such as

pumps, conveyors, tools, fans, and much more.

A BLDC motor is essentially a synchronous motor

with integrated power electronics that operate

the motor from DC supply [1].

The geometry of the windings in a BLDC motor

gives it a trapezoidal back EMF waveform. In this,

the rotor consists of permanent magnets, and the

stator has steel laminations with windings

through axial slots. The windings are wound in a

trapezoidal fashion and produce a trapezoidal

back EMF. For the best performance, the drive

current should match the back EMF waveform, so

BLDC motors should be driven with trapezoidal

waveforms (direct current). Trapezoidal drives

are sometimes referred to as square-wave drives,

although true square waveforms are rarely used

due to their sharp transition between positive

and negative values. Instead, modified square, or

quasi-square current is used (Fig. 1) [2].

In BLDC motors, commutation is the process of

switching the current in the motor phases to

generate motion. BLDC motors come in 1-phase,

2-phase and 3-phase. The number of phases

matches the number of windings on the stator

while the rotor poles can be any number of pairs

depending on the application. Because the rotor

of a BLDC motor is influenced by the revolving

stator poles, the stator pole position must be

tracked in order to effectively drive the 3 motor

phases. *Department of Applied Electronics and Instrumentation Engineering, Girijananda Chowdhury Institute of

Management and Technology, Guwahati-781017, Assam, India.

Correspondence E-mail Id: [email protected]

Automatic Control System for the Bldc Motor A2212/13t using Arduino UNO Platform

Mazinder MS et al. 2


Figure 1.Modified Square or Quasi-square Current [2]

Hence, a motor controller is used to generate a 6-

step commutation pattern on the 3 motor

phases. These 6-steps, or commutation phases,

move an electromagnetic field which causes the

permanent magnets of the rotor to move the

motor shaft [3].

The BLDC motor is an important part of

equipment in many industrial applications

requiring variable speed and load characteristics

due to its ease of controllability. Several studies

on this motor and its control systems have been

done over years.

Jose Carlos Gamazo-Real, et al. [4] had studied

the position and speed control of BLDC motors

using sensorless techniques and application

trends.

Nishtha Shrivastava, et al. [5] presented the

design and simulation of 3-phase double layer

coil BLDC motor for Hybrid (HEV) and Electric

Vehicles (EV) using ANSYS software.

Dinesh Kumar, et al. [6] had performed a

hardware project in speed control of BLDC motor

by using Arduino, and which is designed to

control the speed of a BLDC motor using closed

loop control technique. The proposed system

provides a very precise and effective speed

control system. The user can enter the desired

speed and the motor will run at that exact speed.

R. Giridhar Balakrishna, et al. [7] had designed a

low cost microcontroller based speed control of

BLDC motor.

Geethu Zacharia, et al. [8] had provided a

technical review of back EMF sensing methods

for sensorless BLDC motor drives. The study

included an overview of back-EMF sensing

methods, which included Back-EMF Zero Crossing

Detection method, PWM schemes, Third

Harmonic Voltage Integration, Back-EMF

Integration and Free-wheeling Diode Conduction

method.

Rithvik Gambhir, et al. [9] had studied the

construction, working principle, and various

applications of the Brushless DC Motor (BLDC).

The BLDC was also compared with the

conventional DC motor and AC Induction motor.

Premalatha D., [10] had presented the direct

torque control PI and Fuzzy controller for

minimizing torque ripples of BLDC motor. The

BLDC motor was fed from the inverter where the

rotor position and current controller was the

input. Effectiveness of the proposed control

method was verified through MATLAB/

SIMULINK.

James J. Carroll, et al. [11] had introduced an

integrator back stepping technique for the design

of high-performance motor controllers. The


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approach was applied to the design of embedded

computed torque and output feedback

controllers for PM-BLDC motors. The proposed

controllers were simulated and experimentally

verified on a user-developed digital desired

output waveform. The rate of switching

determined the output frequency of the inverter

signal processor (DSP) based data acquisition and

control (DAC) system.

M. D. Singh, et al. [12] had observed that a 3-

phase inverter circuit changes DC input voltage of

a 3-phase variable frequency, variable voltage

output. A 3-phase bridge inverter can be

constructed by combining 3-single-phase half-

bridge inverters. The switches are opened and

closed periodically in the proper sequence to

produce the waveform.

SYSTEM DESIGN

A simple design of an automatic control system

for BLDC motor is proposed in this work. The

various components required in this design are:

a) M-G Set.

b) Optical Pick-Up.

c) Arduino UNO (ATmega328p).

d) Electronic Speed Controller (ESC).

Figure 2 shows the schematic of the automatic

feedback control system for BLDC Motor with

12V battery supply connected to the potential

divider to vary the voltage from 10-12V. An

ammeter is connected in series to measure the

input current and a voltmeter in parallel to

measure the input voltage. The ESC drives the

BLDC motor and the feedback is taken from the

motor shaft with the optical pick-up assembly.

The RPM measurement circuit of the optical pick-

up assembly measures the RPM and feeds the

feedback signal to the microcontroller

ATmega328p where the feedback voltage is

compared with the reference input voltage and

generates an error signal. The respective error

signal is given to the PID controller which will

maintain a constant speed of the BLDC motor at

varying load conditions. The error voltage and the

RPM values are displayed in the serial monitor for

continuous supervision of the system. The BLDC

motor is coupled with a DC machine for electrical

loading. The ammeter and voltmeter are

connected to the load side for the measurements

of load current and load voltage respectively.

Figure 2.Schematic for the BLDC Motor for Electrical Loading




The operations of different blocks of the system

are discussed as follows:

M-G SET

A BLDC motor and a DC machine are coupled

together to form a M-G set for electrical loading

(Fig. 3).

OPTICAL PICK-UP

Optical pick-up used in the system is a type of

rotary encoder. Rotary encoders (incremental or

absolute, magnetic or optical) track the rotation

of the motor shaft to generate a digital pulse

indicating the motor shaft rpm. They are used

extensively in industrial and commercial designs.

Figure 3.M-G Set with Optical Pick-up Assembly

Figure 3 shows the optical pick-up where the

transmitter section is designed using an IR LED

and the receiver section using a photodiode. A

rotating disc is mounted in between the

transmitter LED and the receiver LED on the

shaft. When the rotating disc intercepts the light

between the transmitter and the receiver then

pulses are developed at the receiver end of the

RPM measurement circuit (Fig. 4). This digital

pulse is used for RPM measurement and

feedback pulse for the system and it is fed to the

Arduino board.

Figure 4.RPM Measurement Circuit


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ARDUINO UNO

Arduino Uno boards are basically development

boards holding a microcontroller ATmega328p.

The microcontroller is programmed to generate a

PWM signal with respect to an analog input fed

to pin A0 through a 100Ω potentiometer. An

analog input of 0-5V is given to the analog pin A0

with the help of the potentiometer providing a

variable set point to the system. The

microcontroller ATmega328p is programmed in

the Arduino software or IDE (Integrated

Development Environment) and uploaded to the

physical programmable circuit board with the

help of a USB connector.

ELECTRONIC SPEED CONTROLLER (ESC)

Electronic Speed Controller (ESC) is an electronic

circuit to vary the speed, direction and possibly to

act as a dynamic brake, of a brushless motor. The

general connection diagram of ESC is shown in

Fig. 5. The PWM pulse is received from the

Arduino and all the controlling is done inside the

ESC to drive the BLDC motor.

Figure 5.Motor Driver: ESC

PROGRAMMING LOGIC USED FOR MOTOR

SPEED CONTROL

The Programming Logic used for speed control of

BLDC motor is a simple procedure as given in the

flow chart (Fig. 6). The logic diagram (Fig. 7)

shows the basic idea behind the programming of

microcontroller (ATmega328p). The ATmega328p

microcontroller has a 10-bit analog to digital

converter (ADC). A reference analog voltage of 5V

is fed to the microcontroller ADC which is

sampled to 210

samples (i.e. 1024). This sampled

value of 0-1023 is scaled down to servo degrees

of 0-179 and then compared with the feedback

signal coming from the RPM measurement

circuit. The difference between the reference

voltage and the feedback signal generates the

error signal. This error voltage is then fed to the

PID controller. PID controller has optimum

control dynamics including zero steady-state

error, fast response (short rise time), no

oscillations, and higher stability. Depending on

the value of the error voltage, the PID controller

generates a controlled PWM signal to drive the

motor at a constant speed.




Figure 6.Flow Chart of ATmega328p Programming

Figure 7.Logic Diagram used for the Motor Speed Control


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EXPERIMENTAL RESULTS

FEEDBACK SIGNAL

The pulse output waveform obtained at the

receiver end of the RPM measurement circuit is

shown in Fig. 8. A typical value of the calculated

RPM of the motor based on the optical sensor

was found to be 2049 against the average

measured RPM of 2050 which were comparable.

Figure 8.Feedback Waveform at the Receiver End of the RPM Measurement Circuit

LINE VOLTAGE WAVEFORMS

The line voltage waveforms obtained at the three

input motor terminals are shown in Fig. 9.

As the line voltage waveforms shown in Fig. 9,

have been recorded at different instants of time,

the waveforms have been normalized with VBC

taken as reference and is shown in Fig. 10 which

indicates the trapezoidal nature of the

waveforms with phase shift among the line

voltages.

Figure 9.Line Voltage Waveforms VAB, VBC, and VBC, VCA Recorded on Two Occasions and Superimposed for

Comparisons (1ms time/division)

Figure 10.Normalized Line Voltage Waveforms: Trapezoidal Waveforms with Phase Shift




The following observations are made from the

waveforms (Figs. 9 and10):

1. The envelope of the voltage waveform is

symmetrical and alternating.

2. Each half-cycle envelope of the voltage

waveform consists of a pulse train having

nearly 30 pulses.

3. Pulse structure of each half-cycle waveform

is due to the controlled PWM feeding the

inverter of the driving unit.

4. The line voltage waveforms are having a

phase difference of 1.2ms.

5. At a particular instant, only two phases, one

from each half, are energized.

6. Harmonics are present in the waveforms.

7. Time Period of one cycle = 8ms.

8. Frequency = 125 Hz.

LINE CURRENT WAVEFORMS

Brushless DC motors, also known as electronically

commutated motors, are synchronous motors

that are powered by a DC electric source via an

integrated inverter switching power supply,

which produces an AC electric signal to drive the

motor. In this context, alternating current doesn’t

imply a sinusoidal waveform but rather a

bidirectional current with no restriction on

waveform [12]. BLDC motor needs quasi-square

current waveforms, which are synchronized with

the back EMF to generate constant output

torque. Also, only two phases are conducting and

the third phase is inactive [13].

The line current waveforms obtained are shown

in Fig. 11.

Figure 11.Line Current Waveform at 5ms time/division

Figure 12.Normalized Line Current Waveform

The following observations are made on the

waveforms shown in Figs. 11 and 12:

1. The waveforms are alternating, each half

constituted by a train of pulses and zero

current periods.

2. The positive side depicts the forward current

and the negative side shows the regenerative

current flowing in the reverse direction

through the freewheeling diodes.


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3. Due to the existence of zero-current periods

between positive and negative pulses, there

is no sharp zero cross over point.

4. Each envelop consists of nearly 25 pulses.

5. Time Period of one cycle = 8 ms.

6. Frequency = 125 Hz.

7. Harmonics are present in the waveforms.

RESPONSE OF THE BLDC MOTOR TO 3-PHASE

AC SUPPLY

As a BLDC motor is also referred to as a

permanent magnet synchronous motor (PMSM),

it has been decided to test the response of the

BLDC motor on AC supply. An experiment was

performed to test the same. A 3-phase AC supply

of 110V (L-L) was stepped down to 3-phase 10V

(L-L) and was applied to the three terminals of

the BLDC motor. There was mechanical vibration

in the motor due to AC supply but didn’t rotate.

The possible reasons are:

i. Unlike the conventional 3-phase synchronous

motors having equal number of stator and

rotor poles, the BLDC motor under test has

12 stator poles and 14 rotor poles.

ii. Whereas the stator winding of a 3-phase

synchronous motor is a 3-phase distributed

winding designed for sinusoidal excitation,

the stator windings of BLDC motor are of

salient type designed for trapezoidal

excitation.

EFFICIENCY CURVE

Direct loading is used to determine the above

performance curves. Mechanical loading is

applied to the BLDC motor through a Prony brake

(with springs calibrated).

To determine the efficiency of a d.c. machine it is

necessary to have a knowledge of the power

input and the power output. In this work a brake

test is carried out with the help of a Prony brake

arrangement to determine the efficiency. The

load on the motor is varied by varying the tension

of the springs. The readings of a spring in grams

are converted to equivalent Newtons by the

relationship:

1 gm = 0.001 kg × 9.8 m/s2 = 0.0098 N (1)

For obtaining the efficiency curve, the following

formulae are used:

Torque T = (Reading at spring A - Reading at

spring B) × Effective radius of the pulley; (Nm) (2)

Output (Shaft) Power POUT = 2лNRPST; (W) (3)

Input Power PIN = VIN× IIN; (W) (4)

Overall Efficiency η = (Pout/Pin) ×100; (%) (5)

Figure 13.Calibration Curve for Spring Balance A in Newton




Figure 14.Calibration Curve for Spring Balance B in Newton

In Figs. 13 and 14, it is observed that there is a

little difference between the actual values of the

weights to the observed values in the springs A

and B. This difference has been neglected for the

graphical analysis of the results.

Figure 15.Efficiency Curve of A2212/13T BLDC Motor

Figure 15 shows the relationship between the

efficiency and the output power. It is observed

that with an increase in output power, efficiency

first increases and reaches its peak at 80% with

9W output power, and then gradually decreases

to nearly 60%.

ELECTRICAL LOADING

The generator which is coupled to the motor

converts mechanical power into electrical power

and that electrical power is used for electrical

loading. Due to fluctuation of speed during

loading, the average value is considered for

performance analysis.

Figure 16.Relationship between Supply Voltage and Motor Terminal (L-L) Voltage

Figure 16 shows the relationship between DC

input voltage and line voltage at the motor

terminals. The motor voltage varies linearly w.r.t.

the supply voltage.


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Figure 17.Relationship between Motor Terminal Voltage (L-L) and Speed

Figure 17 shows the relationship between motor

terminal voltage and speed of the motor. The

speed of the motor is directly proportional to the

motor terminal voltage (L-L). Kv is the motor

velocity constant, measured in RPM (unloaded)

per volt. The Kv rating for A2212/13T BLDC motor

is 1000RPM/V.

Figure 18.Speed versus Input Voltage without Coupling and With Coupling

Figure 18 shows the relationship between speed

and input voltage, without coupling and with

coupling of the BLDC motor to the brushed DC

motor. It is observed that:

1. When supply voltage is increased, the speed

of the BLDC motor increases almost linearly.

2. Coupling of the loading generator results in

mechanical loading and drop in speed.

Figure 19.Speed vs. Load Power at Different Supply Voltages





and load power at three different supply voltages

(10V, 11V, and 12V). The following observations

can be made from the graph:

(i) Speed drops with increasing load and the

rate of decrease increases with decrease in

supply voltage to the motor.

(ii) For a particular load speed increases with

increase in supply voltage.

Figure 20.Speed vs. Torque at Different Supply Voltages


and load torque at three different input voltages

i.e. 10V, 11V, and 12V. It is observed that:

(i) Speed slightly decreases with increase in

torque under open-loop and close-loop

conditions.

(ii) Speed-Torque curve obtained with PID

controller are flat in nature.

CONCLUSIONS

The complete control system for the BLDC motor

(A2212/13T) has been organized, built, and

tested to ensure correct and reliable

performance of all the functional blocks in open-

loop, close-loop, and PID controller modes at

varying load conditions. The observations and

conclusions arrived at from the results are listed

below:

• The motor terminal voltage (L-L) waveform is

alternating with each half cycle having a

trapezoidal shape (Figs. 9 and 10). Each half-

cycle waveform is constituted by a train of

pulses.

• The line voltage waveforms VAB, VBC, and VCA

are having a phase shift of 1.2ms (Figs. 9 and

10).

• At a particular instant, only two phases are

‘ON’ and the third phase is ‘OFF’, depicting

120° degree electronic switching operation

(Figs. 9 and 10).

• The current waveforms are alternating in

nature with zero-current periods. Each

current pulse is constituted by train of pulses.

The positive side depicts the forward current

and the negative side shows the regenerative

current flowing in the reverse direction

through the freewheeling diode (Figs. 11 and

12).

• Harmonics are present in the waveforms

(Figs. 9, 10, 11, and 12).

• The motor has a normal efficiency curve. The

maximum efficiency of the motor is nearly

80% at output power of 9W (Fig. 15).


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• The speed of BLDC motor is directly

proportional to the supply voltage (Figs. 18

and 19).

• The speed drops with increasing load and this

rate of decrease in speed increases with

decrease in supply voltage to the motor (Fig.

19).

• The torque-speed curve is flat in nature (Fig.

20).

• The BLDC motor isn’t responsive to 3-phase,

50 Hz supply at its terminals.

DISCUSSIONS

The number of areas where problems were

encountered have been deliberated upon in the

following paragraphs. They are as follows:

• The response of the optical pick-up decreases

with increase in speed beyond 2500 rpm

affecting the feedback signal (voltage).

• As the mechanical coupling between the

BLDC motor and the loading generator is not

perfect, the operating speed is kept below

2500 rpm.

• As the specifications of the loading PMDC

machine are not available, it has been

observed that at the operating speeds of the

BLDC motor, the output (both voltage and

power) of the machine has been found to be

low.

• As there is fluctuation in the speed of the

BLDC motor, only the average value is taken

for result analysis.

• As the electrical connection of the stator

winding phases isn’t known or can’t be

experimentally determined, the information

on various phase quantities like voltage,

current, resistance, inductance etc., couldn’t

be found.

• The performance of the BLDC motor gets

improved with the implementation of PID

controller with conservative gain constants

(Kp= 1, Ki = 0.05, and Kd = 0.25) and with

aggressive gain constants (Kp= 4, Ki = 0.2, and

Kd = 1). There is no further appreciable

change in the performance of the BLDC

motor with the changes of the gain

constants.

ACKNOWLEDGEMENT

The author wishes to express her deep gratitude

and sincere thanks to Dr. Sandip Bordoloi, B.E.,

M-Tech., PhD., Asstt. Professor and HoD i/c,

Department of Applied Electronics and

Instrumentation Engineering, Girijananda

Chowdhury Institute of Management and

Technology, Azara, Guwahati, Assam for valuable

guidance and constant encouragement

throughout the period of this work. The author is

highly grateful to Prof. P. K. Bordoloi, B.E., M-

Tech., PhD., Senior Professor, Department of AEI,

Prof. P. K. Brahma, B.E., M.S., Visiting faculty,

Department of CSE and Mr. Tridib Roy, B.E.,

Technical Assistant, Department of AEI, GIMT

Guwahati, Assam for the wholehearted

cooperation and valuable suggestions on the

project work. The author is thankful to her

parents and brother for their encouragement and

support throughout the period of this work.

REFERENCES

[1]. https://en.m.wikipedia.org/wiki/Brushless-

electric-motor.

[2]. www.motioncontroltips.com/faq-trapezoi

dal-back-emf/.

[3]. https://googleweblight.com/i?u=https://w

ww.digikey,com/en/article/techzone/2017

//feb/what-is-the-most-effective-way-to-

commutateabldcmotor&grqid=Unpb191u

&hl=en-IN.

[4]. Gamazo-Real JC, Vázquez-Sánchez E,

Gómez-Gil J. Position and Speed Control of

Brushless DC Motors Using Sensorless

Techniques and Application Trends.

Sensors 2010; 10; 6901-47.

[5]. Shrivastava N, Brahmin A. Design of 3-

Phase BLDC Motor for Electric Vehicle

Application by Using Finite Element




Simulation. International Journal of

Emerging Technology and Advanced

Engineering Jan 2014; 4(1).

[6]. Kumar D, Ali M, Kumar P et al. Speed

control of BLDC Motor using Arduino.

Imperial Journal of Interdisciplinary

Research 2017; 3(2): 1060.

[7]. Balakrishna RG, Reddy PY. Speed Control of

Brushless DC Motor Using Microcontroller.

International Journal of Engineering

Technology, Management and Applied

Sciences Jun 2015; 3(6).

[8]. Zacharia G, Raina A. A Survey on Back EMF

Sensing Methods for Sensorless Brushless

DC Motor Drives. International Journal of

Emerging Trends in Engineering Research

Feb 2014; 2(2).

[9]. Gambhir R, Jha A. Brushless DC Motor:

Construction and Applications The

International Journal of Engineering and

Science 2013; 2(5): 72-77.

[10]. Premalatha D. Minimization of Torque

Ripple in the Brushless Dc Motor Using

Direct Torque Control. International

Journal of Emerging Research in

Management & Technology Dec 2014;

3(12).

[11]. Carroll JJ Jr., Dawson DM. Integrator

Backstepping Techniques for the Tracking

Control of Permanent Magnet Brush DC

Motors. IEEE Transactions on Industry

Applications Apr 1995; 31(2).

[12]. https://googleweblight.com/i?u=https://en

.m.wikipedia.org/wiki/Brushless-DC-electr

ic-motor&grqid=fji kfoQz&hl=en-IN.

[13]. https://www.google.co.in/url?sa=t&source

=web&ct=j&url=http://www.sarkanyellato.

hu/wpcontent/up loads/2011/10/RCTimer

10.18.30.40AESCInstruction.pdf&ved=0ahU

KEwiR4KviPTAhXEto8KHeJnAAYQFggiMAI&

usg=AFQjCNFswDLy5tGynZh4YjlAjTn_q1QQ

&sig2=ge19zbD-B8yXFUU-tcFe3A.

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Vol. 1, Issue 1 - 2017 AUTOMATIC CONTROL SYSTEM FOR THE