[Brian C]

The most common cause of this is that the CIM motors will be more powerful in one direection than in the other. This is common to most all DC electric motors and has to do with the timing of the commutator brushes. The motors are designed to be efficient in one direction.

The easiest way to fix this is to use software to "dial back" full throttle on the motor that is more powerful in a given direction.


For example: If the robot veers left while driving forward modify the code to have the right motor see a lower number than 256 when the joystick is fully forward. Continue to change the value down until the robot no longer veers off. While some may argue that your motors will now be going slower it's not really a problem because you will never be able to faster than your slowest motor.

You have probably noticed that the robot veeers in the other direction when you go in reverse. You can use the above example to adjust for that as well.



or


Being that you are center drive with 4 casters the problem could be that 1 of the casters is jamming up a bit.

Also the center drive wheel "may" be slightly off center and causing it to veer slightly as well.