Wheel Calibration

edit

What u mean by velocity controlled?

Δx/Δt: periodically check the nr of encoder counts, convert to radians and divide by sampling period. Then use that with a (pid) controller to expose a velocity controlled interface to each of your motors (ideally: wheels). 1rad/s == 1rad/s, irrespective of what your motor controller does.

That makes things closed-loop. From your description I got the impression that you're currently using an open-loop approach (ie: % PWM or something) and assuming that both motors behave the same. If you add some sensors (ie: encoders), you can make them behave the same.

yes, i convert the joint command in the hardware interface to PWM on the Arduino and update the joint position/velocity from the encoders https://github.com/DeborggraeveR/ampr... will do some reading about velocity controlled and see what i need to change

The velocity control would be done on the arduino-side, probably / preferably. If you don't already have it, you would probably have to run some control loop on the Arduino that checks desired velocity against effective. Then PD control that.