Robot Drifting

[Ryan M.]

Originally Posted by AsimC

Our team is having trouble with our robot drifting to the right while driving straight. We feel that is because one drill motor is running in reverse. I know there is a way to compensate for in in the programming but im not really sure how to do it. Would the Current Sensors help in programming the motors? Any suggestions or examples of code would be very helpful to us. Thanks alot.

The easiest way to do this is to have to enocders on the dirve wheels. FIgure out using those how much faster the one motor is turning than the other. From that figure out how much of a reduction in PWMs you need to make them balance and store that value in a #define. Use the define as an addition/subtraction to what you would normally be putting out on the fast side. If the difference between the motors ever changes, just change the #define value, recompile, and download.

Here is a quick example:

// Somewhere t the top of the file. Comp is short for compensation
// This is the amount of difference in PWMs that makes the motors approzimatly even
#define COMP_SPEED 15
 
 
// In some function that use the motors.
// Go forward. pwm02 is on the slow side
pwm01 = 255;
pwm02 = 255 - COMP_SPEED;
 
// At some later point in the function.
// Go in reverse.
pwm01 = 0;
pwm02 = 0 + COMP_SPEED; // The 0 isn't nessecary, it's just there to illustrate the point

That isn't the optimal solution, of course. The best idea is to have your program monitoring the enocoders and if it sees one side going faster than the other when it shouldn't be, it autonomatically corrects. But, that is more complicated and you should be able to get away with the first solution.