Hybrid control of underactuated systems with discontinuous friction
We propose a hybrid controller for a class of 2-DOF underactuated mechanical systems with discontinuous friction in the unactuated joint. The control objetive is the regulation of both unactuated and actuated variables. The design of the control law is divided in two parts. First we design a discontinuous control for the unactuated joint, then we propose another discontinuous control for the actuated joint. The proposed controller guarantees the convergence of the position error to zero, and it is robust with respect to some uncertainty in the discontinuous friction coefficients. We ilustrate the technique with its application to a physical system.