Simple line follow routine using Fuzzy logic for robot project

I used to play with that little Cybot project that came with the Eaglemoss publications "Real Robots" magazine.

Recently I got very board with it, so, being me, I ripped out its microprocessors, leaving only the sensory and motor control components, and introduced the beloved PIC!

I began with a program that would allow the robot to follow a black line on a white surface.

Check HERE and HERE for the schematics.

It's very simple, the pair of IR sensors feed into a comparator, the black line absorbs IR, the white reflects. When the robot is on the edge of the line, the result would be, one IR sensor at logic 1 and the other at logic 0. The comparator outputs logic 1 to the processor when one input is at logic 1 and the other is a logic 0, otherwise it will output logic 0.

I spend some time thinking about this one, and after a lesson on Fuzzy Logic in IT class at school I finally got it!

So here's how:

Code:

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'****************************************************************
'*  Name    : LineFollow.BAS                                    *
'*  Author  : CIT Systems (Darren Carter)                      *
'*  Notice  : Copyright (c) 2009 CIT Systems (Darren Carter)    *
'*          : All Rights Reserved                              *
'*  Date    : 2009/02/02                                        *
'*  Version : 1.0                                              *
'*  Notes  : Include in PIC-Bot Processor                      *
'*          :                                                  *
'****************************************************************

'Line Follow loop   
LineFollow:
    Lcdout $FE, $C0, "~~ LiNe FoLlOw ~~"    ' Display current mode on LCD.
    Lcdout $FE, $94, "...Scan Line..."      ' Tell user line is being followed.
    low RHF                                ' Stop right motor.
    low LHF                                ' Stop left motor.
    PWM LHF,60,18                          ' Move slightly RIGHT.
    pause 100                              ' Take a break.
    if linecom = 0 then gosub moveleft      ' Check the line, if you no on it, adjust LEFT, otherwise, continue.
   
    low RHF                                ' Stop right motor.
    low LHF                                ' Stop left motor.
    PWM RHF,60,18                          ' Move slightly LEFT.
    pause 100                              ' Take a break.
    if linecom = 0 then gosub moveright    ' Check the line, if you no on it, adjust RIGHT, otherwise, continue.
   
    gosub chkctrl                         
    goto linefollow                        ' Repeat the process
   
MoveLeft:
    Lcdout $FE, $94, "Correct Left"        ' Tell user, correcting LEFT.
    repeat                                 
        low RHF                            ' Stop right motor.
        low LHF                            ' Stop left motor.
        PWM RHF,60,20                     
        pause 100                          ' Take a break.
    until linecom = 1                      ' Do this until back on line.
    pause 50                                ' Take a break, and get ready to move ahead by adjusting a little more LEFT.
    low RHF
    low LHF
    PWM RHF,60,18
    return                                  ' Go back to LineFollow loop.
   
MoveRight:
    Lcdout $FE, $94, "Correct Right"        ' Tell user, correcting RIGHT.
    repeat                                 
        low RHF                            ' Stop right motor.
        low LHF                            ' Stop left motor.
        PWM LHF,60,20                      ' Move a little RIGHT.
        pause 100                          ' Take a break.
    until linecom = 1                      ' Do this until back on line.
    pause 50                                ' Take a break, and get ready to move ahead by adjusting a little more LEFT.
    low RHF
    low LHF
    PWM LHF,60,18
    return                                  ' Go back to LineFollow loop.
   
end

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As you can see, its quite simple, Fuzzy Logic... If the processor is doing one thing, and an error occurs, fix it by doing the opposite.

I've tested this a couple of time, sometimes the robot does move off course and gets lost, but this just a matter of timing and sensitivity, i.e. the motors move too quickly or move the robot too far for the processor and IR sensor to react to change, and/or reaction from the input from the comparator is happens too quickly, so a kind of "debounce" might be necessary.

It's all a matter of trial and error, lots of time, and PIC flashing until it eventually reaches its 2 000 000 000 threshold, LOL :p but that's what hobby robotics is all about.