How to implement a PID controller

Thric

Hi,
I need some advice on how to use a PID controler. I've never used a PID controller before but I believe I know the basics however I'm having difficulty in understanding the exact meaning of the output.

What I'm trying to do is have an rc car go toward a heading. I supply the heading i want to go, I know my current heading (I'm using gyros) and than I have to set the steering servo so that the car goes toward that heading. I treed using http://obex.parallax.com/objects/200/ however i'm not getting the results I'm looking for. I'm probably doing something terrible wrong, i'm most likely misunderstanding how a PID controller works, but any advice is greatly appreciated.

I'm using the propeller if that helps.

thanks

Martin_H

Here's an article on the basics of a PID line follower: http://www.chibots.org/index.php?q=node/339 It might help you with your problem. One of these days I'm going to implement it on my robot as it looks pretty slick.

erco

Another good read on PID at http://www.seattlerobotics.org/encoder/200108/using_a_pid.html This guy starts to get heavy into the math and theory, then he runs out of time before an odometry contest and fakes his way through, only implementing part of the ultimate PID strategy. Nonetheless he wins the contest!