scottyjr:
Recently I had a similar problem. What I did was PWM motor 1 to a constant, but lower than 255, value (e.g. the PWM value to motor 1 is never greater than 245). After a time interval, check the encoder counts of the two motors and have the code automatically adjust, up or down, the PWM value of motor 2 by a fixed value (e.g. 5). I realize that your robot will most likely not move at the same speed all the time but the code could be written to have the PWM of motor 2 adjust to the the PWM value of motor 1. - Scotty
you mean like keep constantly checking the speed of both motors by the encoder rotation count, and for example if left motor count is high 20 counts decrease it speed and viceversa?