Control of two contact point sheet registration devices for xerographic printers

Xerographic printers printing on pre-cut sheets need to register (align) each sheet with its corresponding image before image transfer. There exists a variety of sheet registration devices that perform this function, utilizing different actuator and sensor configurations. A majority of these devices have three or more degrees of freedom and contact the sheet at two points during registration. A control algorithm for this class of devices has been developed. The main contribution of the proposed control approach is that it avoids explicitly dealing with the non-holonomic constraints of the combined sheet and registration device system. This simplifies the control design compared to other approaches. The proposed control algorithm comprises of two parts: a generic part for two contact point devices and a registration device specific part which depends on the actuator configuration and kinematics of the registration device. It can also incorporate active control of the buckle that may form in the sheet portion between the two contact points during registration, hereby minimizing the possibility of sheet damage and jams.