Interconnection and damping assignment passivity-based control of a class of underactuated mechanical systems with dynamic friction

This paper considers the extension of the interconnection and damping assignment passivity-based control methodology for a class of underactuated mechanical systems with dynamic friction. We present a new damping assignment approach to compensate friction by means of a nonlinear observer. Friction at the actuated joints is assumed to be captured by a bristle deflection model: the Dahl model. Based on the Lyapunov direct method we show that, under some conditions, the overall closed-loop system is stable and, by invoking the theorem of Barbashin-Krasovskii, we arrive to asymptotic stability conditions. Experiments with an underactuated mechanical system, the Furuta pendulum, show the effectiveness of the proposed scheme when friction is compensated. Copyright (c) 2010 John Wiley & Sons, Ltd.