Line Following rOBOT 2

Presented by Rodrigue Tchamna

Kang dong-hoonPark jang sung

June 2010

• Line follower is a machine that can follow a path. The path can be

visible like a black line on a white surface (or vice-versa)

or it can be invisible like a magnetic field.

• Sensing a line and maneuvering the robot to stay on course, while constantly correcting wrong moves using feedback mechanism forms a simple yet effective closed loop system.

APPLICATIONS OF A LINE FOLLOWER Automated cars running on roads with embedded magnets; guidance system for industrial robots moving on shop floor

deliver mail within an office building and deliver medications in a hospital.

Tour guides in museums and other similar applications.

following a line in a warehouse (to distribute goods)

the technology has been suggested for running buses and other mass transit systems, and may end up as part of autonomous cars navigating the freeway.Tour guides in museums and other similar applications.

OBJECTIVES OF A LINE FOLLOWERFollow any complex black curves It should be capable of taking various degrees of

turnsThe robot must also be capable of following a line

even if it has breaks. The robot must be insensitive to environmental

factors such as lighting and noise.Stop and reverse if the line disappearsStop if an obstacle is presentSo the robot will also need its own illumination

source. The weapon here will is to use Infra Red (IR) light.

THE BLOCK DIAGRAM

PIC 16F873Microcontroller

H - BridgeDC Motor Control

LeftMotor

Right Motor

Clock6 MHz Main Power

Supply

Motor Power Supply

HEX Inverter

Sensor Array

Analog Comparators

Threshold Voltage

PIN CONFIGURATION OF THE MICROCONCONTROLLER

IN1 IN2 IN3 IN4 OPERATION

0 1 1 0 BOTH MOTORS FORWARD(MOVE FORWARD)

1 0 0 1 BOTH MOTORS BACKWARD(MOVE BACKWARD)

0 1 0 0 RIGHT MOTOR BACKWARDLEFT MOTOR FORWARD

(TURN RIGHT)

0 0 1 0 RIGHT MOTOR FORWARDLEFT MOTOR BACKWARD

(TURN LEFT)

1 1 1 1 FULL STOP

CIRCUIT

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.

The potential at point ‘2’ is proportional toRsensor / (Rsensor + R1).

Again, a good sensor circuit should give maximum change in potential at point ‘2’ for no-light and bright-light conditions.

However, it would be nice if the signal that we get could be TTL (on or off, 0V, 5V). So to do this one need a comparator

Normally, all we need in order to track a black line on a white surface is Light Emitting Diode (Emitter) and Photo Diode (Receiver Sensor)

ALGORITHM

L= leftmost sensor which reads 0; R= rightmost sensor which reads 0.If no sensor on Left (or Right) is 0 then L (or R) equals 0;

L4

L3

L2

L1

R1

R2

R3

R4

1 1 1 0 0 1 1 1left Right

CenterL=1 and R = 1 L=R so go straight forward

The two Center sensors that track the line

Assumption: The width of the track is at least the distance between 2 subsequent sensors

The algorithm tries to position the robot such that L1 and R1 both read 0 and the rest read 1.

LEDPhoto diode sensor

8 4 2 1 8 4 2 1

=0xE7

9 ,A, B, C, D, E, F10

11

12

13

14

15

ALGORITHML= leftmost sensor which reads 0; R= rightmost sensor which reads 0.If no sensor on Left (or Right) is 0 then L (or R) equals 0;

L4

L3

L2

L1

R1

R2

R3

R4

1 1 0 0 1 1 1 1left Right

CenterL=2 and R = 0 L>R so turn left



9 ,A, B, C, D, E, F10

11

12

13

14

15

=0xCF

8 4 2 1 8 4 2 1

=0x9F

ALGORITHM

L= leftmost sensor which reads 0; R= rightmost sensor which reads 0.If no sensor on Left (or Right) is 0 then L (or R) equals 0;

L4

L3

L2

L1

R1

R2

R3

R4

1 1 1 0 0 1 1 1left Right



Assumption: The width of the track is at least the distance between 2 subsequent sensors

The algorithm tries to position the robot such that L1 and R1 both read 0 and the rest read 1.



L4

L3

L2

L1

R1

R2

R3

R4

1 1 0 0 1 1 1 1left Right





L4

L3

L2

L1

R1

R2

R3

R4

1 0 0 1 1 1 1 1left Right





L4

L3

L2

L1

R1

R2

R3

R4

1 1 1 1 0 0 0 1left Right

CenterL=0 and R = 3 R>L so turn Right




L4

L3

L2

L1

R1

R2

R3

R4

1 1 1 0 0 0 0 1left Right

CenterL=1 and R = 3 R>L so go straight forward




L4

L3

L2

L1

R1

R2

R3

R4

1 0 0 0 0 1 1 1left Right

CenterL=3 and R = 1; L>R so Go LEFTeft




L4

L3

L2

L1

R1

R2

R3

R4

1 0 0 0 0 0 0 1left Right




2. If all sensors read 1 go to step 3,else,If L>R Move LeftIf L<R Move RightIf L=R Move ForwardGoto step 4

3. Move Clockwise if line was last seen on Right Move Counter Clockwise if line was last seen on Left Repeat step 3 till line is found.

4. Goto step 1.

1. L= leftmost sensor which reads 0; R= rightmost sensor which reads 0.If no sensor on Left (or Right) is 0 then L (or R) equals 0;

TRACE HEIGHT

8


0110 0111

RememberThe motor moves only when the LED’s light (white color) hits the black track and light is reflected back to the photo diode sensor

Starting point

FWD = Forward

L = Left

R= Right

Go FWD

0000 1111 Go LEFTeft

0110 0111 Go FWD

1110 0000 Go RIGHT

1110 0100 Go FWD

1111 0001 Go RIGHT

1110 0100 Go FWD

1111 0000 Go RIGHT

1110 0101 Go FWD

1111 0110 Go RIGHT

1110 0100 Go FWD

1111 0110 Go RIGHT

1110 0100 Go FWD

1110 0100 Go LEFT

1111 0100 Go FWD

0110 0000 Go LEFT

1011 0111 Go FWD

0000 1111 Go LEFT

0011 0111 Go FWD

0100 1111 Go LEFT

1010 0111 Go FWD

0110 1111 Go LEFT

0110 0111 Go FWD

0110 1111 Go LEFT

0110 0111 Go FWD

0110 0011 Go LEFT

End point

0110 0111 FwD0000 1111 Left1111 0100 Left1100 0100 FwD0110 0000 Left1011 0111 FwD0000 1111 Left0011 0111 FwD0100 1111 Left1010 0111 FwD0110 1111 Left0110 0111 FwD0110 1111 Left0110 0111 FwD0110 0011 Left

So Finally

0110 0111 FwD1110 0000 Right1110 0100 FwD1111 0001 Right1110 0100 FwD1111 0000 Right1110 0101 FwD1111 0110 Right1110 0100 FwD1111 0110 Right1110 0100 FwD

FWD0110 0111 1110 0100 1110 0101 1100 0100 1011 01110011 0111 1010 0111

Left0000 1111 1111 0100 0110 00000100 1111 0110 1111 0110 0011

Right1110 0000 1111 0001 1111 0000 1111 0110

Left = 0x (0F, F4, 60, 4F, 6F, 63)

FWD= 0x (67, E4, E5, C4, B7, 37, A7)

After reduction,

Right= 0x (E0, F1, F0, F6)

LIMITATIONS• The width of line to track depends on the disposition

and distance between the sensors array and cannot be changed by software.

• Thin curves are not tracked efficiently, and must be avoided.

RESULT AND CONCLUSIONThe Robot could Follow any complex black curves, with various degrees of turnsThe robot was insensitive to environmental factors such as lighting and noise.It could Stop and reverse when line disappears

THANK YOU FOR LISTENING

EXTRACT OF CODE

while (1){if(PIND!=0xff)

{rotpow=255;ldev=rdev=0;

if(PD3==0)rdev=1;if(PD2==0)rdev=2;if(PD1==0)rdev=3;if(PD0==0)rdev=4;

if(PD4==0)ldev=1;if(PD5==0)ldev=2;if(PD6==0)ldev=3;if(PD7==0)ldev=4;

L4

L3

L2

L1

R1

R2

R3

R4

1 1 1 0 1 1 1 1

PD0PD1PD2PD3PD4PD5PD6PD7

if(rdev>ldev)move(R,0,Speed1);if(rdev<ldev)move(L,0,Speed2);if(rdev==ldev)move(FWD,0,speed_FWD);

}

}; //End While

} //End Main

CODE• //PORTB=0x39; stop• //PORTB=0x18; straight• //PORTB=0x10;Left• //PORTB=0x08; Right• // PORTB=0x21; Reverse

• #include <avr/io.h>• #include <avr/interrupt.h>• #include <util/delay.h>

• #define FWD 0x18• #define REV 0x21• #define R 0x08• #define L 0x10• #define STOP 0x39

• #define CW 0x99• #define CCW 0x66

• #define SPEED0 255• #define SPEED1 0• #define SPEED2 0• #define SPEED3 0

• #define MAX 3• #define HMAX 1

• void move (unsigned char dir,unsigned char delay,unsigned char power);

• unsigned int Speed1=1000, Speed2=1000 ,speed_FWD=2000;

• unsigned char i,rdev,ldev,ip,delay,dir,power,dirl,history[MAX],hcount=0,rotpow;

• int main(void)• {

DDRB=0xff;//motor(PB4->ena_a / PB1->in1 / PB0->in2

PORTD=0xff;DDRD=0x00; // DDR = Data Direction

RegisterTCCR1A=0xA3;TCCR1B=0x02;//8 Busy

while (1) { if(PIND!=0xff) { rotpow=255; ldev=rdev=0; if(PD3==0) rdev=1; if(PD2==0) rdev=2; if(PD1==0) rdev=3; if(PD0==0) rdev=4;

if(PD4==0) ldev=1; if(PD5==0) ldev=2; if(PD6==0) ldev=3; if(PD7==0) ldev=4; if(rdev>ldev) move(R,0,Speed1); if(rdev<ldev) move(L,0,Speed2); if(rdev==ldev) move(FWD,0,speed_FWD); //_delay_ms(100); //sleep(10); }

else { for(i=0,dirl=0;i<MAX;i++) { if(history[i]==L) {dirl++;} }

if(rotpow<160) {rotpow=160;} if(rotpow<255) {rotpow++;} if(dirl>HMAX){move(CW,0,rotpow);} else{move(CCW,0,rotpow);} } OCR1A = Speed1; OCR1B = Speed2; }; //End While

} //End Main

• void move (unsigned char dir,unsigned char delay,unsigned char power) • {• PORTB=dir;• //Speed1=power;• //Speed2=power;• if(dir==L || dir==R) • {• hcount=(hcount+1)%MAX;• history[hcount]=dir;• }• //LSPEED=RSPEED=2000;//power• Speed1=Speed2=2000;• speed_FWD=2000;• //delay_ms(delay);• }

Line Following rOBOT 2

Documents

r equals

l4 l3 l2 l1 r1 r r r

rightmost sensor

right center

leftmost sensor wh

photo diode receiver

good sensor circuit

center sensors