[DonRotolo]

How?
Create 2 variables, "Out" and "Old_Out", default them to 127. Store the real final PWM output to Out, and subtract Old_Out, and if the difference is greater than some rate of change (say 50), reset the value to the rate of change (Out - 50). Then set Old_Out == Out, and repeat each loop. You'll have to manage the math a little bit, to prevent exceeding 255 or zero, and maybe elsewhere, but that basic idea is a simple PID loop with only D being used.

Good idea? Maybe not. Driver training is probably a better approach.

Don