Paper sheet control using steerable nips

Many high speed color printers require that sheets be accurately controlled in order to achieve a precise alignment of colors. To accomplish this goal, a steerable nips mechanism has been proposed as an actuator to propel sheets along the printer´s paper path. This steerable nips mechanism allows the sheet to be precisely controlled in the longitudinal, lateral and skew directions. In this paper we develop a control strategy based on linearization by state feedback and dynamic surface control (DSC) to precisely control the position of the sheet. The proposed controller is able to move the sheet from an initial to a final state under the condition that the sheet has nonzero initial and final velocities. The system model is nonlinear and subject to four nonholonomic constraints. Two of these constraints are related to the fact that the velocities perpendicular to the wheels must be zero, and the other two constraints are due to the non-slip condition.