Robust Nonlinear Control of Parametric Uncertain Systems With Unknown Friction and Its Application to a Pneumatic Control Valve

Abstract

A robust nonlinear control approach is presented for parametric uncertain systems with unknown friction. First- and second-order systems are considered, respectively. A model reference controller is developed such that the tracking error is bounded and converges to zero in the presence of the parameter uncertainty and the unknown friction. Then, the controller is extended to general case with any order. To design the controller, exact friction force is not required, only the upper bound for the level. Lyapunov’s direct method is used to prove robust global convergence of the tracking error. Finally, experimental results are given by applying the proposed controller to a pneumatic control valve. [S0022-0434(00)01802-5]