Chances are it's not the motor controller's fault, unless one side is
drastically slower than the other. Like your robot turns in small circles, not just drifts slowly off of straight. Even then, it's more likely to be wiring or mechanical.
Options:
- The slower side is mechanically bound up some how. power off your robot and turn both sides by hand and see if one is easier than the other.
- If you're using more than 1 CIM per side, maybe you're not driving one of them because of a bad motor controller, bad motor, or bad wiring.
- You may not be driving both sides equally. Wire has resistance, resistance reduces voltages, voltage drives the speed of a motor. (It's like that Mentat chant from Dune.) Anyways, if you have more wire from the PDP to the motor controller and from the motor controller to the motor, that motor will run slower. So check and make sure you have the same amount of wire running to your left and right side motors.