Park position control apparatus for a sheet transport system

Abstract

A method and apparatus for assuring proper park positioning of a sheet gripper device. A reference signal is generated by a master control board causing the sheet gripper to commence its movement along the belts of a sheet transport system. An index marker and encoder coupled to a servo motor generate pulses based on the rotation of the shaft of the servo motor. A registration control board coupled to the servo motor generates an index interrupt after receipt of a predetermined number of pulses from the index marker. The number of rising and falling edges of a system clock that occur between the generation of the reference signal and the index interrupt is computed by the registration control board and sent to the master control board. The master control board compares this distance value to a predetermined resynchronization value. Based on the discrepancy between the two values, the master control board recalculates a park position value which is sent to the registration control board. The park position value is the amount of time that elapses after the sheet gripper has passed a gripper home sensor. Thus, recalculation of the park position value insures accurate park positioning prior to the performance of each job.