Proposal Report 6

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University ofManchester

School of Electrical & ElectronicEngineering

Embedded Systems

Project

PROPOSALREPORT

Sensor Selection andNavigation Strategy

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Table of contents

Introduction..

Aims andObjectives.

Teamorganization.

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I. Introduction

Most often, the general description of a project does not allow the visualization of all its

complexity. With the Embedded System Project it is not different. Despite the general

description just present the construction of a line follower buggy, is when we divide the project

into smaller parts that it become possible to identify all the specifications necessary to perform

each of the objectives to be achieved.

Much of the importance of the Proposal Report is on the intention to scale a guide for all future

activities needed to complete the project. A well planned project, with divisions of tasks well

organized and that takes into account realistic deadlines and possible unforeseen is more likely

to be successful.

Thinking about it, this report was developed in order to specify the most number of points

possible. Firstly, will be presented the group's objectives and the requirements that it must

have reached until the end of the project. Then will be shown how the group was organizedduring the initial phase of the project, including the positive and negative experiences of the

form of development adopted so far. These experiments were used to organize a new work plan

to be accomplished during the course of the next semester, which is a crucial phase of the

project development. This new work plan is also presented in this report. Finally, will be

presented all technical specifications of the project, including Software Specifications, Budget,

Chassis, Gearbox, Sensors, Interface and Risk Assessment. Additional information necessary to

the correct understanding of each of the sessions was included in the appendix added to the

end of the report.

II. Aims and Objectives

The project that started to be develop during this semester and will be finished in the next one

aims to provide a practical introduction to the microcontroller-based implementation of

embedded systems, what will be achieved through the planning and construction of a buggy.

This buggy should be capable of navigating around a track, up a slope and coming to a

controlled stop, without human intervention. The track will have the following characteristics:

* Will be bordered by a wall at least 50mm high in all places.

* Will have a white line, which will be at least 150mm away from each wall

* There may be breaks in the white line of up to 2mm in the direction of travel and 50mm

laterally.

* The white line will not change direction by more than 45 every 50mm for an angle bend, andwill have a minimum bend radius of 50mm for a smooth bend

*The white line will stop at least 200mm from the target wall and the buggy should stop in acontrolled manner at the end of track.

The winning buggies will be the one that completes the course in the fastest time and the most

cost effective one. A rough layout of the track can be represented for the following picture:

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Fig 1: Layout of the likely test track, fig 1 of [1].

From the analysis of Fig1 and the specifications presented above, system requirements can be

represented by the following figure. Specify and detail the manner that we are going to deal

with all the actions cited in this image is the main objective of this report.

Fig 2: Project Requirements.

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A copy of this image with the text in readable size was added to appendix 1.

The project aims to give students an understanding of the specification, analysis, design,

implementation and testing of embedded systems through practical application of relevant

theory and techniques, as well as how to develop a systematic approach to testing and

debugging both hardware and software [1].

III. Team Organization

This session aims to explain the organization of the group during this first semester and how we

intend to organize the same during the next semester

The Facebook group of the Embedded System Project was built in week 3, semester 1. This

Facebook group is a great place to communicate among the team members as every team

member is asked to log in Facebook every day. All meetings, with the specification of time andplace are noticed in this group and if any of the members has a special query related to the

project, it can also be posted, as the other members will try to solve it.

The group is also used as a logbook, as all the files, pictures and agendas are stored there and

we have found it a convenient way for source sharing.

During this first semester, the tasks performed by each member of the group varied in each

part of the project, seeking to give opportunity to each member to acquire new knowledge.

The group also sought the realization of constant meetings, and an agenda was maintained for

each of them.

The weekly reports were responsibility of the member Gabriela Maciel, who served as secretary

of the group during the semester. The reports were always posted in the group on Monday or

Tuesday that preceded the next meeting so that group members could give their opinion on it

before it was sent to the group`s tutor (Dr. Rob Sloan).

A picture of our Facebook group (Fig 2), one of our weekly reports (Fig 3) and one of our

meeting agendas are available in appendix 1 (Fig 4).

Based on the experiences gained this semester, the preferences of each members andanalyzing the areas where each of them showed a performance of bigger quality, tasks for the

next semester were divided as follows:

Gabriela Maciel: Will be part of the software team and will act like the group`s menager.

Bankole Sodipo: Will be part of the Software team. May also help in the hardware team ifhis knowledge is needed.

Min jin: Will be part of the hardware team and act like the groups secretary.

Min Yao: Will be part of the software team. May also help in the hardware team if hisknowledge is needed

Kush Shah: Will be part of the hardware team and take care about the group`s budget.

Because tasks related to software development require more time than the tasks related tohardware assembly, when the members of the hardware team conclude their tasks, they willjoin the software team to enable more speed in completing tasks, as explained in greater detail

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in the next session

.

IV. Project Plan

The project planning was organized to meet the specifications required for each technical

demonstration. The deadlines were set after research with project groups from previous years,

to allow enough time for each task to be performed with ease.

According to the tasks of each member already specified in the previous session, the activities

of the next semester will be held according the following workflow:

Tasks Start Week Duration Dependenc

ies

A-Chassis,

Gearbox and

Motors

assembly

Week 2 1 weeks Availability

of the

component

s

B-Software

Development 1

Week 2 2 weeks -

C-Test 1 Week 4 1 week A, B

D-Sensor`s

circuit assembly

Week 4 1 weeks Availability

of thecomponent

s

E-Software

Development 2

Week 4 2 weeks -

F-Test of

sensors

Week 6 1 week D, E

G-Assembly the

sensors to the

rest of thebuggy

Week 6 1 week -

H-Software

Development 3

Week 6 2 weeks B, E

I-Test of the

buggy

Week 8 1 week G, H

J-Improvements

in the buggy

design

Week 8 2 weeks G

K-Improvements Week 8 2 weeks G, H

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and changes in

the software

L-Final tests Week 9 1 weeks J, K

Table 1: Project plan

First Technical Demonstration:As the object of the first technical demonstration is to state the assembled chassis, gearbox and

motors, under the control of the microprocessor, the members Min Jin and Kush Shah, will be

responsible of assembling all the parts of the buggy (excluding sensors). The estimated time for

the realization of this activity is one week.

The members Gabriela Maciel, Bankole Sodipo and Min Yao, responsible for the software part,

will be in charge of developing the following features:

The successful use of the pulse width modulation (PWM) output features ofthe PIC;

Driving both motors independently from PIC PWM outputs, fed through the

drive PCB;

An appropriate selection of PWM switching frequency and inverter bridge

control mode;

A fully-assembled chassis with gearbox, motors and wheels and batteries,

(at this stage there is no need to have fitted the sensors);

Independent control of the buggy wheels from the microprocessor [1].

After concluding their hardware tasks, the members Min Jin and Kush Shah will also help in the

software development.

The estimated time for the realization of this activity is also two weeks.

After the completion of these two tasks, there will be a week to the junction of the hardware

and software parts of the project, then placing the realization of tests to verify if the project

meets all the needs that will be evaluated in the first demonstration

Second Technical Demonstration:The objective of the second demonstration is show the correct operation of the sensor(s).

Confirming that individual sensor outputs change as predicted, when

moved between a white line and the dark background.

Showing that the microprocessor detects changes in the sensed values as

expected.

Showing that the microprocessor can successfully identify the location of

the line, and the absence of a line.

Demonstrating how conditions for a controlled stop will be distinguished

from those of a line break [1].

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The members Min Jin and Kush Shah will be responsible of the assembly of the sensors` circuit

while the members Gabriela Maciel, Bankole Sodipo and Min Yao will be responsible of the

development of the software that meets all these specifications. The estimated time for the

realization of these two activities is two weeks. The sensors do not need to be mounted on the

buggy for this demonstration.

After the realization of these two activities, a week was set aside for the realization of the

sensor testing.

Third Technical Demonstration:The objective of the third demonstration is show the buggy following a section of white line on a

flat surface, under control of the microprocessor, including curves and breaks. The buggy

should be capable of following a straight section of white line along a flat surface, following a

curve, negotiating a break in the line and coming to a controlled stop at the end of the line [1].

The members Min Jin and Kush Shah will be responsible of gathering the hardware parts of thetwo previous demonstrations, what mean mount the sensors in the buggy. The members

Gabriela Maciel, Bankole Sodipo and Min Yao will be responsible of gathering the software parts

already developed and transform it in a code capable of perform all the specifications stated

above. After concluding their hardware tasks, the members Min Jin and Kush Shah will also help

in the software development.

There will be a time of two weeks for the realization of these activities and after their

conclusion; there will be a one week time for the realization of testes before the technical

demonstration.

Last Technical Demonstration \ Race Day:For the final demonstration on race day, the buggy should be able to navigate the entire length

of the track and stop in a controlled manner at the end of track. As the buggy mounting must

be completed before demonstration 3, the time space between the third and the fourth

demonstration will be dedicated to the realization of improvements in the software and

eventual changes in the buggy design. The members Min Jin and Kush Shah will be responsible

for the design while the members Gabriela Maciel, Bankole Sodipo and Min Yao will be

responsible for the conclusion of the software that will be used in the race day. This part of the

project will last two weeks and a final week to test the expected performance of the buggy in

the race day will be allocated.

A Gantt chart with all the information provided in this session is presented in appendix 2, fig 1.

Contingency Plan:Before each technical demonstration there is a time of three weeks for the completion of tasks,

being the last week apart for testing only.

In relation to hardware, if any component is not functioning up to the middle of the second

week, it should be substituted so that the completion of the task is possible until the end of the

second week and tests will be performed in the subsequent week.

In relation to software development, as it is entirely dependent on the performance of group

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members, the contingency plan boils down to devote enough time to the completion of each

task, being possible, in the latter case, the utilization of the tests week for the conclusion of

activities.

If any member of the group is unable to perform his duties during a certain period of time, due

to illness or some other justifiable reason, its activities will be divided among the other groupmembers in order to not overload any of them.

V. Software Specifications and Use Case Model

Functional Summary:

When the buggy is switched on, it will move at full speed for a short burst and then control of

the motors will be assumed by the PIC microcontroller (PIC18lf8722). Its aim is to keep moving

forward till it reaches the finish line. The 5 sensors infront of the buggy will send a voltagecorresponding to the amount of reflected Infra-red reaching them and from this, the PIC will

determine where the line is. The IR sensor at the rear, IR 6 ensures allignment.

When there is a bend in the line the sensors send a different voltage to the PIC. Based on the

difference between the left and right sensors, the PIC can determine whether to bear left or

right. If there is a break in the line, the PIC could interprete a tempoary break in the tape or the

end of the track. It can distinguish between these using the sensor at the rear.

On encountering a slope, the current sensing element attached to the motors will experience a

surge in the current demanded and indicate to the PIC to supply more torque to both motors.

To confirm the completion of the track, the PIC will compare all data from the sensors and if it

gets equal readings indicating a black surface, the end has been reached.

Constraints

- 10MHz clock frequency: This is the PICs maximum operating speed. This means the team

will have to avoid complex operations such as floating point arithmetic.

- Budget: The team is restricted to 50 to design a fully functional buggy

- Power: limited power is left for use on the sensor array due to the load of the motors and thePIC.

System Context

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from the sensorsand store thereading inallocated memoryspaces.

data takenfrom the sensorinputs anddecide on whatthe next courseof action will

be.

the end of the track byfollowing a white line.

to a controlledstop when itreaches the endof track.

Description To periodicallycheck and processsensor data todetermine whichside of the linethe buggy isdeviating towards.

The data fromthe sensors isto be analysedby a function oftheprogrammingand will decideon which of thenext course of

actions are tobe carried out.

Then use this data toalter the motor speedsin order to guide buggyin the correct direction.

Uses the datafrom sensorinputs to detectwhen the buggyhas lost thewhite line.Buggy carriesout a check toconfirm it has

reached theend of the whiteline. If thecheckingprocedureconfirms thatthe track hasfinished, buggystops.

Variation of

Externalobject

Detects whether

each sensor isabove a whiteline, above ablack backgroundor on the edge ofthe line andbackground.

Strategic placement of

sensors allows formonitoring of bothchange in line directionand also buggydeviation.

- Buggy deviation: Ifthe left-hand-sidedeviation sensorsenses a strongerwhite line signal,then the right-hand-side motors speed will

be increased to steerbuggy towards correctpath. And vice-versa.- Change in linedirection: If the right-hand-side turningsensordetects thewhite line, then(when referencesensordetectsbeginning of turn) left-

hand-side motor turnsforward and right-hand-side motor turns

When the

sensors detecta no whiteline signal, thebuggy pivots90 left andthen 180 rightto scan thefront semi-circlearea of thetrack at thebuggysposition. If the

white line isfound, then thebuggycontinues itsmovement inthat direction.However, if theline is not foundduring thisprocess, theback sensor willbe checked andif no signal isdetected, the

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in reverse in order forbuggy to pivot in thecorrect direction untilanother sensorconfirms that thebuggy is facing correct

direction. And vice-versa.

microchipprocessorrealises that thetrack has endedand stops allpower to the

motors,bringing thebuggypermanently toa halt

Table 3: Use case Model

Use case Diagram

Figure 4: Use case diagram.

Power up and move:

Send full current to motors

Continue operation for short time

Exit loop and begin the rest of the program

Read sensors:

Convert analogue data from sensors to digital

Read the values for each sensor

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Store values in data array

Send array to control case, Follow line

Or if end of track detected, activate case Stop motion

Follow line:

Check which sensor is receiving the most reflected IR

Find the desired alignment

Equate appropriate Pulse frequency for motors

Stop motion

Cut all current to both motors

Object Diagram

Figure 5. Object Diagram.

This gives an idea of all the objects and communications that will be going on in the buggy.

Details of all functions are given in Appendix 3.

VI. Hardware Specifications

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In this session, information regarding to the Chassis Base Plate Drawing, Gearbox Assembly and

Circuit Diagram of Sensors/Pic Interface will be provided.

The buggy that the group should build consists ofmany components, all of which mount onto

the chassis. The main components are: A 9V battery-pack, MicroChip PIC18f8722 processor,

break-out board, drive board, sensors, gearboxes, motors and wheels.

Like specified in the previous report, our sensors will be connected to the analogue ports of

the processor, where the threshold levels for detecting different sensor inputs can be

defined within the code of the processor. This eliminates the need for any extra signal

conditioning circuits, which would increase the complexity of the sensor circuits, decrease

the efficiency of the electronic system and negatively affect the budget for the project.

Further information about the sensor`s choice is available in appendix 4 and appendix 6.

The previous tests done for the conclusion of the first technical report, the reading of the

project handbook and further studies showed that varying the voltage across a motor can

proportionally vary its output speed, hence this property of the motors will be exploited,

through the use of the pulse-width-modulation (PWM) function on the processor, to control

the speed of the motors. A PWM signal creates an average voltage that depends on the

PWMs mark-space ratio. The 9V power supply from the battery pack will be adjusted to a

suitable voltage using PWM techniques.

Technical Drawings of all main details of our buggy design is available in appendix 4, includingthe Chassis Base Plate Drawing (Fig 1, Fig 2 and Fig 3), Pictures of the gearbox Assembly (Fig 4,Fig 5, Fig 6), Circuit Diagram of Sensors (Fig 7) and 3D pictures of the buggy design (Fig 8, Fig 9and Fig 10).

VII. Budget

The budget costs include the components we will be using as seen on the table below (table 3).

It covers the 6 Reflective Optical sensors we will be using on the buggy and a further 4 more

standing by as insurance.

Component Supplier Stock

Number

Unit

Quantity

Unit

Price ()

Units

Required

Cost

()Threaded Spacers RSComponents

221-184 50 0.578 1 0.578

Angle Brackets RSComponents

749-1686 10 2.235 1 2.235

Wire RSComponents

724-4345 1 16.98 0.1 1.698

Reflective OpticalSensors

RSComponent

s

708-5017 5 0.608 2 1.216

10K OhmsResistors

RSComponent

135-910 10 0.017 1 0.017

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s

150K OhmsResistors

RSComponents

131-514 10 0.019 1 0.019

Perspex Chassis

Total Budget 5.763Budget Limit 50

Amount Left Over 44.237

Table 4: Budget

Further reference for the components prices is available in appendix 4.

VIII. Justification of Proposed Design

Chassis Material:Please refer to the table 1, in appendix 6, for the data quoted for these comparisons.

From the list of available material choices, our final decision for the chassis material is Glass-

Reinforced Laminate (GRL).

As can be seen from the table, GRL is the cheapest material available to us, and since the

project is designed with a limited budget in mind, this material is the most suitable.

Furthermore, GRL is the second least dense material, minimising the weight, which means thatthe less power is needed to get the buggy moving. Since power consumption is one of the

constraints of this project, and then minimising the power wastage is a key concern.

Finally, relative to the thickness of GRL, as compared to the only other plastic available,

Perspex, the Flexural Strength is more desirable, with a value of 255MPa, with a thickness of

2mm, compared to the thicker 3mm Perspex, which can only sustain 105MPa. The metals

materials, as expected, did have greater Flexural Strength, with values of 310MPa and 414MPa

for Aluminium and Mild Steel respectively. Perspex, though less dense was discounted, since

the cost price was almost twice that of GRL.

Finally the Ultimate Tensile Strength of GRL was almost triple the value of Perspex, so it is moreappropriate for the chassis, since the buggy will be subject to a pressure test, and so GRL will

perform better under this particular.

Gear Ratio:

The chosen value for the gear ratio was 12 and further information about this choice is providedin appendix 6.

Sensors:

The chosen sensor was the TCRT5000 (REFLECTIVE OPTCAL SENSOR). Please refer to the datatables in appendix 6 for the data quoted. Our choice of sensor was decided after muchdeliberation, and extensive testing of the available sensors, and their performance under

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different conditions.

IX. Risk Assessment

The group has devoted considerable effort to identify as many possible causes of accidents

during the work development. Great care and considerations have been made, with regards to

Health and Safety, in order to minimize risk to the team and other people related to this work.

During all stages, the risks have been carefully assessed and evaluated, and this can be seen

from the detailed Risk Assessment table. [Please refer to Table 1 of Appendix 7]

X. Conclusion

In conclusion, this proposal document has detailed our design proposal and how we are going toorganize the time and divide the task with the members of the group in the next semester. Thereport also showed the main aspects of the project that were developed during this firstsemester and that helped the group in the making decisions about the design and programmingof the buggy.

The winning features of this design are that we are working well within the budget, and havemet the initial system requirements spending just over 10% of our budget.

The following images are what we intend out buggy to look like. Further information about thatis available in appendix 4.

XI. References

[1] Aplsey, J and Green, P. 2012. Embedded Systems Project Handbook. 2nd ed. Manchester:

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School of Electrical & Electronic Engineering.

Appendix 1: Supporting Material

This appendix provide additional information required to the correct understand of the report.

Fig 1: Systems Requirements.

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Fig 2: Facebook Group.

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Fig 3: Meeting Agenda.

Appendix 2: Gantt Chart

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This appendix presents the Gantt chart that illustrates the project schedule for the nextsemester.

Fig 1: Gantt chart.

Appendix 3: Function prototypes

This appendix presents the C functions prototypes that will be used in the softwaredevelopment of the project. The functions are:

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unsigned int sensor_array[6] read_sensors(void): Returns an array of 6 integers from

sensors. Estimated operation time is approximately 500 us.

unsigned int to_motor[2] compute_direction(unsigned int x[6]) : takes the array from

read_sensors() and uses a control algorithm to determine whether the buggy should be goingstraight, left or right and how sharp the turn should be. This function is only intelligent or

thinking part of the program. It then returns an array of two integers used to set appropriate

PWM duty cycles for each motor.

unsigned char pulse_motors (unsigned int y[2]) : This will take the array produced by

compute_direction() and send that duty cycle to the left and right motor. All PWM functions are

contained here. A character would be returned to indicate to another function whether the

buggy has moved straight, left or right and give an idea how fast its moving.

#pragma code isr:This interrupt service routine will be called upon by an external source

which will be triggered by the current surge due to the buggy reaching the slope. It will deliver

more current to the motors and the function stop_race will never be called except this isr has

been run.

void stop_race (void): This will be called by compute_direction() when it has been determined

thhe buggy has reached the end of the track. The function will then stop the buggy

appropriately.

Appendix 4: Hardware Specification TechnicalDrawings

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Chassis Base Plate drawing:

Fig 1: Technical Drawing of the Chassis.

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Fig 2: technical Drawing of the Chassis with further specifications.

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Fig 3: Location of the components in the chassis.

Gearbox Assembly:

Fig 4: Gear Specifications.

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Fig 5: Gearbox plate.

Fig 6: Gearbox plate further specification.

Circuit Diagram:

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Fig 9: Front Design of the Buggy.

Fig 10: Side design of the Buggy.

Appendix 5: Budget

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Here are references to prices found for each the components. The pages were consultedbetween the days 12/06/12 and 12/12/12.

Threaded Spacers: http://uk.rs-online.com/web/p/threaded-standoffs/0221184/?searchTerm=221-184&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D424552267573743D3232312D3138342677633D4E4F4E4526

Angle Brackets: http://uk.rs-online.com/web/p/angle-brackets/7491686/?searchTerm=749-1686&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5

C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D424552267573743D3734392D313638362677633D4E4F4E4526

Wire: http://uk.rs-online.com/web/p/single-core-control-cable/7244345/?searchTerm=724-4345&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D424552267573743D3732342D343334352677633D4E4F4E4526

Reflective Optical Sensors: http://uk.rs-online.com/web/p/reflective-optical-

sensors/7085017/?searchTerm=708-5017&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D424552267573743D3730382D353031372677633D4E4F4E4526

10k Ohms resistors: http://uk.rs-online.com/web/p/through-hole-fixed-resistors/0135910/?searchTerm=135-910&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D4

24552267573743D3133352D3931302677633D4E4F4E4526

150k Ohms resistors: http://uk.rs-online.com/web/p/through-hole-fixed-resistors/0131514/

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Appendix 6: Proposed DesignChassis Material:

Table 1: Materials specifications.

Gear Ratio:

According to data obtained from the first lab session. The maximum torque motor can provided

is 0.0105Nm. The design of the buggy has been improved and the up limit of the maximum

weight of the buggy is set to be 1.2kg (the empty weight of the buggy frame is 0.389kg) and

the output torque from each motor to insure buggy go up the slope is 0.084Nm refer to the

previous calculation. The gear combination implemented within our gearbox has two stages. So

the efficiency is approximately 72.25%, the total output torque needed is 0.1163Nm. Hence

the gear ratio should be0.1163

0.0105=11.07 (using the maximum output torque during the climbing

stage). Considering the unexpected efficiency loss and the manufacturing reason (there is no

suitable gear combination available for us to achieve such a gear ratio). The actual gear ratio is

set to be 12 to make it suitable to achieve and have spare capability to deal with the

unexpected situation.

Sensors Testes and Choice:

1. Test using a White L.E.D and a LDR

The LDR adjusted its resistance according to the brightness of the light, the brighter the light, the higher

the resistance hence the decrease in voltage. This is shown in the graph below.

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Fig 1: RMS voltage against Distance.

2. Test using IR LED Emitter and a Phototransistor

The phototransistor detected Infra-red signals, the stronger the signal the lower the voltage.


3. Test using IR LED Emitter and Photodiode

A photo diode works in a similar way to a phototransistor. In this case the output voltage with reflective

tape is seen to increase with distance and without tape it is shown to increase very slowly.


These 3 sensors are seen to be very sensitive with short distances showing their range is short. Their

angle readings have to be calculated precisely to use them with good accuracy which proves to bedifficult. The last 2 sensor circuits require large resistances to operate which take up a lot of space due to

many resistors.

32

Distance(mm)

WithTape(V)

WithoutTape (V)

10 2.875 4.48420 3.343 4.396

30 3.663 4.37240 3.889 4.31550 3.994 4.31360 4.003 4.28570 4.04 4.268

Table 1

Distance(mm)

WithTape(V)

WithoutTape (V)

5 1.06 3.26610 1.359 3.28215 1.502 3.3520 1.756 3.53825 2.235 3.60930 2.844 3.92935 4.013 4.059

Table 2

Distance

(mm)

WithTape

(V)

Without

Tape (V)5 2.521 3.87510 2.779 3.99615 2.93 4.03620 3.387 4.05325 3.941 4.10630 4.1 4.17735 4.143 4.194

Table 3


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TCRT5000 (REFLECTIVE OPTCAL SENSOR)The experiment compared the output voltage from TCRT5000 phototransistor in different height againstthe same reflection background (made by the surface of the toolkit or a printed black paper as the blackbackground as well as a white tape line). The circuit used to test the sensor of TCRT5000 is showed below(Fig 4). The phototransistor within the TCRT5000 is acting as a receiver. The resistance of thephototransistor will become smaller when it receives infrared emitted by the diode. When the receiverreceived reflection from the white tape surface, the voltage across the receiver dropped in different level(depends on the type of the receiver used). The amplitude of the voltage difference between thereflection from white line and from black background indicated the sensitivity of the sensor combination.The selection of the proper sensor can be made by comparing the voltage drop in the same verticaldistance the test background off the sensor.

Fig 4: Circuit test.

Reference voltage:4.645V Height of the sensor:0.2cm

Vertical Distance(cm) 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5

white tape surface(V)0.19

50.22

20.25

2.48

3.193.59

3.954.11

4.26

black background surface(V)3.42 3.61

4.09

4.27

4.354.46

4.524.56

4.59

Voltage difference(black andwhite)(V)

3.23 3.393.84

1.79

1.160.87

0.570.45

0.33

Table 4

Reference voltage:4.645V

Horizontal Distance(cm)

Vertical distance (cm)

0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5

0.252.95

V3.48

V3.62

V3.86

V4.26

V4.34

V4.38

V4.44

V4.50

V

0.53.23

V3.57

V3.93

V4.21

V4.32

V4.40

V4.48

V4.51

V4.54

VTable 5

According to the data showed in Table 4 and 5, the initial voltage across two sides of the phototransistoris 4.645V when the receiver receives no reflection. The sensor is placed in parallel with the white line(emitter is on the front and the receiver is on the back). The voltage difference can be observe clearly(more than 1V) when the phototransistor received the different reflection from the white line and blackbackground in a certain vertical distance (from top of the sensor to the reflection background) varied

from 0.5cm to 1.75cm. The voltage change is also detectable when the sensor has a horizontal distancefrom the border of the white line in a certain vertical distance. The moment the horizontal distance isover 0.5cm, the voltage across the phototransistor is almost the same with the condition it is totally

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under the black zone. Therefore there is no need to measure the output from the horizontal distance over0.5cm. In general the output voltage from the TCRT5000s phototransistor is very stable. The voltagedifference between reflection from white line and black background is significant within a relatively largevertical and horizontal distance.After test and compared the data from all four different types of sensors. The ultimate choice for our

sensor is the Reflective Optical Sensor with Transistor Output TCRT5000 (REFLECTIVE OPTCAL SENSOR).

The main components of it include an infrared emitter and a phototransistor as well as a daylight blockingfilter. The phototransistor is able to detect the reflection from various types of reflective materials for

instance paper and tape. And this is corresponding to the reflective background we used to test the

sensor as well as the material could be used on the track of the buggy race. The emitter integrated on

the TCRT5000 emits infrared and therefore avoid a major part of the interference from the daylight or the

light source installed within the race room. With the help of the daylight blocking filter it is possible to

further eliminate the potential outside light or other electro-magnetic wave interference to make the

detection as accurate as possible. The other consideration in choosing this type of sensor is that the

space needed to install it is the smallest. The high integration of the TCRT5000 makes it possible to save

the space which is needed to place the LEDs and receivers compared to other sensor choices. The place

on the buggy is very limited with the possibility to contain extra components in the future design and

improvement. The voltage difference is stable and significant compared to other choices of sensors(showed in Fig 1, 2 and 3). Therefore choosing the TCRT5000 can provide the buggy control system a

clear and accurate input data.

Appendix 7: Risk Assessment

Below is a table of the risks identified, alongside their associated activity, a severity score forthis risk, and the actions taken to reduce this risk.

NOTE: In the cases where a range of consequences was identified, then the severity ratingquoted takes the most severe event for the risk assessment.

Table x: Risk Assessment of Identified risks and management strategies.

Documents

Proposal Report 6