Path Following Robot

UNIVERSITY OF MORATUWA

Department of Computer Science and Engineering

Group Name:- Phoenix

Group members:-

Gunasinghe U. L. D. N. 100162X Sashika W. A. D. 100487X Siriwardena M.P. 100512X Udara Y.B.M. 100544V Wijayarathna D.G.C.D. 100596F

Path Following Robot

Content.

1. Abstract

2. Acknowledgment

3. Introduction

3.1. What is a line follower?

3.2. Why build a line follower?

3.3. Prerequisites

3.4. Microcontroller- 16F877A

4. Overview

4.1. Block Diagram and Architectural Overview

4.2. The Algorithm

5. Implementation

5.1. Sensor Circuit

5.2. Analog to Digital Converter

5.3. PIC Simulation Circuit

5.4. Motor Interface and Control Circuit

5.5. Source Code

6. Possible Improvements

7. References and Resources

7.1. Books and Links

7.2. Discussion with Experts

7.3. Parts and Prices

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Abstract

“The Path following Robot” is the project work done by our group in the fulfillment

of the “Engineering Design” and “Skill Development” courses in level1-term A2.

This will be useful to reach the places where human can’t reach. A practical example

is guidance system for industrial robots moving on shop floor etc.

We have used IR sensors to detect the road and PIC 16F877A as our central

processing unit.

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Acknowledgment

Apart of from the effort of us, the success of this product depends largely on the

encouragement and guidelines of many others. We take this opportunity to express our

gratitude to the people who have been instrumental in the successful completion of this

project.

First of all we would like to thank our project coordinator Dr. MalakaWalpola, who

guided us to do “The Path Following Robot” as our project and helped us throughout the

whole period.

We are grateful to Eng. B.S. Samarasiri and Prof. J.A.K.S. Jayasinghe who gave us

instructions about doing such project.

We specially thank our friend Mr. ArunaUpul of Electronic and Telecommunication

Engineering department (Level 1) who helped us in designing electronic circuits and

correcting the problems in circuit boards. Without him we would not come so far. Also we

would like to thank Mr. SupunTharanga of Electronic and Telecommunication Engineering

department (Level 1) for giving us a great support to all the works we carried out.

Then we would like to thank our mentor Mr. PubuduGunawardena of Computer

science and Engineering Department (Level 4) for giving us instructions and useful

references.

In addition to all of them we would like to thank to all others who helped us in various

ways.

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Introduction

What is a line Follower?

A machine which is built to follow a specific path is defined as a Line Follower. The

line may have different appearances

A Black line on a white surface or vice-versa.

An Invisible line as a magnetic field.

Why build a line Follower?

There we can find places where humans face troubles when they try to reach these

places. In such situations we can use a machine which has the ability to take decisions as

humans. A line follower is such a machine.

As the level 1 Engineering Design project we were instructed to create a line

following robot which identify black path on the white surface and follow it, and also it

should be able to make decisions itself to turn at a junction according to a mark situated

before it.

Prerequisites

Basic knowledge about electronic components.

Basic knowledge on electronic circuit designing and making.

Basic knowledge on C Programing.

Innovative brain and perseverance.

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Microcontroller-16F877A

As we analyze the problem we realize that we have to get seven

inputs and four outputs. So we decided that the most suitable

microcontroller for our requirements is the 16F877Amicrocontroller.

It consists of four input/output ports and PWM module. This

persuades us to use it in our circuit.

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Overview

Block Diagram and Architectural Overview

The robot uses IR sensors to sense the line, a set of 7 IR sensorsfacingthe ground has been used in this setup. The output of the sensors is an analog signal whichdepends on the amount of light reflected back, this analog signal is given to the comparator toproduce 0s and 1s which are then fed to the micro controller.

2 cm

3 cm

Let’s take the middle sensor as M Starting from the center, the sensors on the left are named L1, L2, L3 and those on the right are named R1, R2, R3.Let us assume that when a sensor is on the line it reads 1 and when it is off the line it reads 0.

The micro controller decides the next move according to the algorithm given below which tries to position the robot.

When going in road straight it position such as M reads 1 while L1 and M1 reads0. When R1 or L1 reads 1 it says that robot is away from road and take it to the road.

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Sensor

Panel

Analog to Digital

ConverterPIC

Motor Controller

Circuit

Analog Signal

Digital Signal

M

L3 L2 L1 R1 R2 R3


L2 and M2 has positioned to detect the signs that indicate which side to turn in a junction. L3 and R3 has positioned to detect whether the robot has reached to a junction.There are two motors to drive the robot. Those can rotate in both ways, to front and back.

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Algorithm

1. If M=0 and all others are equal to 0 then robot should go straight. So both motors should rotate in same way to front.

2. If L1=1 then robot should turn to left. So left motor should stop and only right motor should turn forward.

3. If R1=1then the robot should turn right. So right motor should stop and only left motor should turn forward.

4. If L2=1 and L3=0 while the variable junction=0 and variable junction_over=0, then robot has detected a sign which says to turn to left in next junction. So the variable turn_left should take the value 1 and variable turn_right should take the value 0.

5. If R2=1 and R3=0 while the variable junction=0 and variable junction_over=0, then robot has detected a sign which says to turn to left in next junction. So the variable turn_right should take the value 1 and variable turn_left should take the value 0.

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L3=0 L2=0 L1=0 M=1 R1=0 R2=0 R3=0

L3=0 L2=0 L1=1 M=1 R1=0 R2=0 R3=0

L3=0 L2=0 L1=1 M=0 R1=0 R2=0 R3=0

L3=0 L2=0 L1=0 M=1 R1=1 R2=0 R3=0

L3=0 L2=0 L1=1 M=1 R1=1 R2=0 R3=0

L3=0 L2=1 L1=1 M=1 R1=0 R2=0 R3=0

L3=0 L2=0 L1=0 M=1 R1=1 R2=1 R3=0


6. If R3=1 or L3=1 then the robot has reached to a junction, then the variable junction should take the value 1.

7. While variable turn_right=1, and junction=1 then the robot should turn right in the detected junction. So the left wheel should rotate forward and right wheel should rotate back.

8. While variable turn_left=1, and junction=1 then the robot should turn left in the detected junction. So the right wheel should rotate forward and left wheel should rotate back.

9. While variable junction=0 and turn_right or turn_left equals to 1, then half of the turning has been completed. So variable junction should take the value 0 and variable junction_over should take the value 1.

10. While variable junction_over=1 and variable turn_right=1 still the robot has to turn to right. So the left wheel should rotate forward and right wheel should rotate back.

11. While variable junction_over=1 and variable turn_left=1 still the robot has to turn to left.So the right wheel should rotate forward and left wheel should rotate back.

12. While variable_junction_over=1 and if M=1 the turning has been completed. So the variable junction_over=0, turn_right=0 and turn_left=0.

13. While turn_right=0 and turn_left=0 if L3=1 or R3=1 then robot has reached a junction which it has to go without turn. So the robot has to go straight from the junction. So it has to go straight without considering any mark while it reach the L3=1 or R3=1which is not the one detected first and till it passes it.

14. If M=0, R1=0 and L1=0 then it has to go straight. So both wheels should rotate forward.

15. These steps should be done until power is disconnected from robot.

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L3=1 L2 L1 M R1 R2 R3

L3 L2 L1 M R1 R2 R3=1

L3 L2 L1 M=0 R1 R2 R3

L3=0 L2=0 L1=0 M=0 R1=0 R2=0 R3=0


Implementation

Sensor Circuit

We used IR sensors detect difference between black road and the white background. The resistance of the sensor decreases when IR light falls on it. A good sensor will have near zero resistance in presence of light and a very large resistance in absence of light. We have used this property of the sensor to form a potential divider.

Sensor Panel

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2cm

1.5cm1.5cm 2.5cm2.5cm 2cm2cm

Sensor

IR LED


Sensor Circuit

Analog to Digital ConverterWe

used operational amplifiers to convert analog signal comes from the sensor. Depending on the amount of Infra Red waves reflected from the path, sensor gives a voltage output. This voltage varies from 0V to 5V. This circuit gives an output 5V if the voltage input from the sensor is above a certain level and otherwise 0V. We can adjust this using variable resistor.

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To PIC

10K

1K

GND

+5V


PIC Simulation Circuit

We give the input to the PIC which comes from ADC converter circuit through PORT B. we have used pin 1 to 7 in the PORT B. We get output from the PIC through PORT D. For this we have used pin 0, 3, 4, 5 in PORT D. We gives the output from the PIC to the motor control circuit.

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Motor Interface and Control Circuit

The L298 Motor Driver has 4 inputs to control the motion of the motors and two enable inputs which are used for switching the motors on and off. To control the speed of the motors a PWM waveform with variable duty cycle is applied to the enable pins.

The 1N4004 diodes are used to prevent back EMF of the motors from disturbing the remaining circuit.

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Source Code

#include "H:\roba\gggg.h"

/* ROBOT CONTROLLING PROGRAMME BY PHEONEX*/

void main()

{

int1 turn_right=0;

int1 turn_left=0;

int1 junction=0;

int1 junction_over=0;

setup_adc_ports(NO_ANALOGS);

setup_adc(ADC_OFF);

setup_psp(PSP_DISABLED);

setup_spi(FALSE);

setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);

setup_timer_1(T1_DISABLED);

setup_timer_2(T2_DISABLED,0,1);

setup_comparator(NC_NC_NC_NC);

setup_vref(FALSE);

// TODO: USER CODE!!

while(TRUE)

{

//We used B0,B1,B2,B3,B4,B6,B7 and D0,D3,D4,D5as outputs

//THIS PART DRIVE ROBOT IN NORMAL ROAD(NOT IN JUNCTION)

if(junction==0&&junction_over==0)

{

if((input(PIN_B4))&&(!(input(PIN_B0)))&&(!(input(PIN_B5))))

{

output_D(0b00010001);

delay_us(100);

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}

if(!(input(PIN_B4)) && (!(input(PIN_B0))) && (!(input(PIN_B5))))

{

output_D(0b00010001);

delay_us(100);

}

if((!(input(PIN_B6)))&&(input(PIN_B2))&&(input(PIN_B0))&&(input(PIN_B4))&&(input(PIN_B5)))

{

output_D(0b00000001);

delay_us(100);

}

if((!(input(PIN_B2)))&&(input(PIN_B6))&&(input(PIN_B0))&&(input(PIN_B4))&&(input(PIN_B5)))

{

output_D(0b00010000);

delay_us(100);

}

if((!(input(PIN_B2)))&&(input(PIN_B6))&&(!(input(PIN_B0)))&&(input(PIN_B4))&&(input(PIN_B5)))

{

output_D(0b00010001);

delay_us(100);

}

else if((!(input(PIN_B0))) && (input(PIN_B5)))

{

output_D(0b00010000);

delay_us(100);

}

if((input(PIN_B2))&&!(input(PIN_B6))&&(input(PIN_B0))&&(input(PIN_B4))&&(!(input(PIN_B5))))

{

output_D(0b00010001);

delay_us(100);

}

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else if((input(PIN_C0)) && (!(input(PIN_B5))))

{

output_D(0b00000001);

delay_us(100);

}

//this part detect the marks that leads robot through a junction

if((input(PIN_B6))&& (!(input(PIN_B7))))

{

turn_right=1;

turn_left=0;

}

if((input(PIN_B2))&& (!(input(PIN_B1))))

{

turn_left=1;

turn_right=0;

}

}

//This part turns the robot to right in a junction

if(((input(PIN_B1))|| (input(PIN_B7))) && turn_right==1)

{

junction=1;

}

if(junction==1 && turn_right==1 && input(PIN_B4))

{

output_D(0b00000001);

delay_us(100);

}

if(junction==1 && turn_right==1 && (!( input(PIN_B4))))

{

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junction=0;

junction_over=1;

}

if(junction_over==1 && turn_right==1 && (!( input(PIN_B4))))

{

output_D(0b00000001);

delay_us(100);

}

if(junction_over==1 && turn_right==1 && ( input(PIN_B4)))

{

junction_over=0;

turn_right=0;

}

//This part turns the robot to left in a junction

if(((input(PIN_B1))|| (input(PIN_B7))) && turn_left==1)

{

junction=1;

}

if(junction==1 && turn_left==1 && input(PIN_B4))

{

output_D(0b00010000);

delay_us(100);

}

if(junction==1 && turn_left==1 && (!(input(PIN_B4))))

{

junction=0;

junction_over=1;

}

if(junction_over==1 && turn_left==1 && (!(input(PIN_B4))))

{

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output_D(0b00010000);

delay_us(100);

}

if(junction_over==1 && turn_left==1 && (input(PIN_B4)))

{

junction_over=0;

turn_left=0;

}

//If no signl found before junction this part leads robot through without turning

if(turn_right==0&&turn_left==0&&(input(PIN_B7)))

{

while(!input(PIN_B1))

{

if((input(PIN_B4))&&(!(input(PIN_B0))))

{

output_D(0b00010001);

delay_us(100);

}

if(input(PIN_B0))

{

output_D(0b00010000);

delay_us(100);

}

}

while(input(PIN_B1))

{


{

output_D(0b00010001);

delay_us(100);

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}

if(input(PIN_B5))

{

output_D(0b00000001);

delay_us(100);

}

}

}

if(turn_right==0&&turn_left==0&&(input(PIN_B1)))

{

while(!input(PIN_B7))

{


{

output_D(0b00010001);

delay_us(100);

}

if(input(PIN_B5))

{

output_D(0b00000001);

delay_us(100);

}

}

while(input(PIN_B7))

{


{

output_D(0b00010001);

delay_us(100);

}

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if(input(PIN_B0))

{

output_D(0b00010000);

delay_us(100);

}

}

}

output_D(0b00000000);

delay_us(10);

}

}

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Possible Improvements

In this project we haven’t use PWM (Pulse Width Module) method to control our motors. Because we didn’t have an enough knowledge about using it. But we could expect better performance if we could include.

We are using a 6V power pack with a lengthy wire as the power source. If we can use a sufficient and constant voltage, the robot will become more portable.

References and Resources

Books and Links

http://www.google.lk/search?

q=line+follower&hl=en&prmd=ivnsb&source=univ&tbs=vid:1&tbo=u&sa=X&ei=g2KUTaatOM

WHrAeqzo3jCw&ved=0CDsQqwQ

http://robotika.yweb.sk/skola/AVR/visionrobo%20com/Line%20Follower%20tutorial

%20v1.1.pdf

http://www.botskool.com/tutorials/electronics/8051/line-follower

http://www.kmitl.ac.th/~kswichit/ROBOT/Follower.pdf

http://www.docstoc.com/docs/64977263/Line-following-robot-tutorial

http://www.richardvannoy.info/building-a-line-following-robot.pdf

http://www.tombot.net/beam/linefollowingcircuit.html

http://www.ermicro.com/blog/?p=1097

http://docs.google.com/viewer?

a=v&q=cache:WXamZCglK3UJ:vjtirobotics.files.wordpress.com/2008/09/

linefollower_tricks.doc+build+line+follower&hl=en&gl=lk&pid=bl&srcid=ADGEES

hm4TXBoqBpvNTwScbQKoI_Wayxn0HBz_QMKTbHpnaf8pVJAK2wPJUIjkFJdz2

No0UjmtN8BWTi1BOmqTi0a-QGbgootbW42Px3xw2nz6dY-j_oFezBrJojYMM-

QFs84oBD5kjz&sig=AHIEtbS8vwB7pLdTJEJoU0PeJOoDoLeBmA&pli=1

http://www.youtube.com/watch?v=I_NU2ruzyc4

http://www.youtube.com/watch?v=BLfXXRfRIzY

http://www.youtube.com/watch?v=6QznAAwL8rI

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http://www.google.lk/search?q=line+follower&hl=en&prmd=ivnsb&source=univ&tbs=vid:1&tbo=u&sa=X&ei=g2KUTaatOMWHrAeqzo3jCw&ved=0CDsQqwQ




Discussion with Experts

Discussion with Mr. Aruna Upul(Level I) of Electronic and Telecommunication Department.Discussion with Mr. Pubudu Gunawardena (Level IV) of Computer Science and Engineering Department.

Parts and Prices

Item Quantity Unit Price CostPIC 16F877A 1 Rs 450.00 Rs 450.00PIC and IC Bases Rs 70.00 Rs 70.00Gear Motors 2 Rs 2200.00 Rs 2200.00Sensor Devices 7 Rs 80.00 Rs 560.00H-Bridge Driver IC 1 Rs 220.00 Rs 220.00PCB 1 Rs 600.00 Rs 600.00Other Components Rs 1400 .00 Rs 1400.00

Total Rs 5500.00

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Education

Path Following Robot