Media transport system with high precision position and speed control

Abstract

A media transport system for controlling the position and velocity of media in a document production apparatus marking engine having a media positioning system driven by a motor, includes a motion control loop to control the motor; a sensor adapted to detect the position of the media and to create a trigonometric signal characteristic of the position of the media, the trigonometric signal comprising frequency and phase components; a resolver electronics subsystem adapted to trigonometrically process the trigonometric signal to create a resolved signal; and means for comparing the resolved signal to a reference clock signal of predetermined frequency and phase to provide an error signal used to control the motor that drives the media positioning system. The trigonometric signal may include a sine portion and a cosine portion. The sine portion of the trigonometric signal is sin(.omega..sub.e *t+.phi..sub.e) and the cosine portion of the trigonometric signal is cos(.omega..sub.e *t+.phi..sub.e); where .omega..sub.e is the trigonometric signal frequency component, .phi..sub.e is the trigonometric signal phase component, and t is the time. The resolver electronics subsystem may include a first multiplier adapted to output the product of the sine portion of the trigonometric signal and a reference cosine command cos(.omega..sub.r *t+.phi..sub.r); a second multiplier adapted to output the product of cosine portion of the trigonometric signal and a reference sine command sin(.omega..sub.r *t+.phi..sub.r), where .omega..sub.r is the frequency of the reference command and .phi..sub.r is the phase of the reference command; and means to add the outputs of the first and second multipliers.