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Over the past few decades, the two-wheeled driven cart, also known as the unicycle wheeled mobile robot or wheeled mobile robot with independently driven wheels, has been a favorite case study in the literature on nonholonomic control. In this paper, we show how input-output linearization of a cart can be leveraged for a novel and practical application, closed-loop control of a differential-drive sheet registration device. The current state of the art for control for such a device, typically found in xerographic engines like printers and copiers, is open-loop motion planning. We present a closed-loop method that achieves full-state trajectory tracking via input-output linearization and asymptotically stable internal dynamics. To achieve rapid convergence while satisfying acceleration constraints, we apply elementary gain scheduling to the output tracking controller of the linearized input-output system. Experimental results are presented to demonstrate the effectiveness of the discrete-time implementation of our control strategy, which is based on a kinematic model with acceleration as the control input.
Date of Publication: July 2008