Combined compensation control for Wiener-Hammerstein systems with backlash nonlinearities

For Wiener-Hammerstein systems with asymmetric backlash nonlinearities, we propose a novel combined compensation control consisting of the output feedback and a dynamic inverse compensation for backlash. The piecewise linear parametric representation is first utilized to simultaneously estimate the characteristic parameters of the asymmetric backlash and the unknown coefficients in the linear transfer function. Then, we build a new error-bounded dynamic inverse model for the backlash; this model makes it possible for the driving signal to be quickly switched between different line segments of the backlash. On this basis, we develop the robust compensation law. Meanwhile, by using output feedback, we build a compound controller for the input linear loop. The stability of the closed-loop is proved by means of Lyapunov method. Simulation is carried out on a single-motor servo system with speed reducer. Results show that the proposed method provides not only excellent tracking accuracies, but also the desirable dynamic response as well.