METHOD AND APPARATUS FOR MINIMIZING THE OPEN LOOP PAPER POSITIONAL ERROR IN A CONTROL SYSTEM FOR AN ELECTROPHOTOGRAPHIC PRINTING APPARATUS

A method of minimizing error in an estimate of a position of a sheet of print medium in an electrophotographic machine includes providing a transport system including a gearing system to drive a roll for moving the sheet of print medium along a print medium path. The gears are in constant mesh with each other and with an actuator. The electrophotographic machine is provided with a toner transfer point at which the toner can be transferred to the moving sheet of print medium. A sensor is placed at a set distance away from the transfer nip along the print medium path. This distance is approximately equal to an integer multiple of the resulting distance traveled by the medium during one revolution of the lowest frequency component of the transport system. The frequencies associated with all other components in the transport system, including the actuator and an encoder wheel, are designed to be an integer multiple of this lowest frequency. The gearing system is actuated with a rotating actuator such that the actuator rotates approximately an integer number of times during a corresponding rotation of the lowest frequency component. An encoder wheel is also used to provide feedback to a control algorithm. A position of the sheet of print medium is sensed with the sensor.