| State of the art high speed color printers require that sheets be accurately positioned as they arrive at the image transfer station. To accomplish this goal a steerable nips mechanism must be added to the paper path mechanism, upstream from the image transfer station, to precisely control a sheet in the longitudinal, lateral, and skew directions.; In this dissertation, the design of a steerable nips mechanism, which has been designed and built at the University of California Berkeley, is presented. This mechanism is a Multi-Input Multi-Output (MIMO) system. The dynamics of a sheet under the control of the steerable nips mechanism are nonlinear and are subject to four nonholonomic constraints. This mechanism is equipped with standard printer parts, such as a feeder and an exit roller. A microcontroller and various sensors are also part of the experimental setup.; Three different control strategies were developed. The control objective of these strategies is to control, using the developed steerable nips mechanism, a sheet's position and angular orientation from an initial to a final state under the condition that the sheet has nonzero velocities at all times. Each of these strategies assumes a different type of actuator dynamics. The first control strategy assumes that the acceleration of the rotating rollers and the steering angle velocity of each of the rollers can be manipulated by the controller. The second control law considers a more realistic form of actuator dynamics; it assumes that the rotating and steering angular acceleration for both rollers can be manipulated by the controller, this results in a system that fails to have vector relative degree. A third control strategy assumes each actuator as a simple servo system that is represented by a second order differential equation; this strategy was successfully implemented on an experimental setup. Techniques used in the development of these static and dynamic control strategies include linearization by state feedback and Dynamic Surface Control. |
