Line Follower Design Challenging Problems

[Michael Chua]

Good Day to all.

Firstly, thanks for browsing.

Yes, I am facing some problem with the design of a line follower. I am building a line follower which which is self-guided and work by inductively sensing a wire loop, carrying an AC current. There is the sensors, control system and motor drive circuit.


I like to develop this line follower by using just logic based controller instead of using a microcontroller.

Sensor System:
Sensor will be ferrite core inductors. Two sensors used and when making a left turn, left sensor will have more induced voltage than the right. The two voltages will be compared through a voltage comparator.


Motor System:
Motor System will received the control signal. The steering direction is control by inputting a voltage range of 0-5V to steering motor. So when on a straight line, there is no need to input voltage to the steering motor. 0Volt for full left, 5V for full right. The motor drive is single and not dual. Hence, everything need to be control by the motor drive IC

Control System:

Three possibilities:
Test Point 1 (left) > Test Point 2(right)
Test Point 2(right) > Test Point 1 (left)
Test Point 1(left) = Test Point 2(right)

Case 1:
Test Point 1 (left) > Test Point 2(right)
Output of Comparator A turn on.

Case 2:
Test Point 2(right) > Test Point 1 (left)
Output of Comparator B turn on.

Case 3:
Test Point 1(left) = Test Point 2(right)
Do nothing

Problem 1:
In case 1, vehicle know it have to steer left. So circuit can pull the output A to zero voltage which is send to the steering motor for a full left turn.
But if it's a full left turn? How can it adjust proportionally for steering. From 0 - 2.5 V
In fact, there is a potentiometer connected at the steering motor at front? But How do I use that?? What sort of logic is required?

And additional functions to reacquire the track if lost.

Regards
Michael

Any help is appreciated...

 

[ravix]

I think this will be a difficult task without a microcontroller. What you are describing is proportional feedback. If you want the line-follower to have reasonably fluid motions you'll need a derivative element, too.

Although the sensing method is different, this site has a good example of a line-follower robot. At the bottom he has a video of the performance with only proportional control. The car veers off course and doesn't perform well.

It will be easier to learn to use a PIC than to try to make this work with logic IC's.