A method and system of correcting a medium velocity error in a
photoreceptor belt of an image forming device with a controller,
including measuring a velocity error of the photoreceptor belt when the
medium is used in the image forming device, the velocity error comprising
a velocity error due to the image forming device dynamics and a velocity
error due to torque disturbance on the photoreceptor belt, filtering high
frequency velocity error from the measured velocity error, removing the
velocity error due to the image forming device dynamics from the measured
velocity error to produce a remaining velocity error, converting the
remaining velocity error to torque disturbance, determining a correction
factor on the basis of the torque disturbance, and correcting the medium
velocity factor on the basis of the determined correction factor.