A hybrid adaptive wavelet neural network control and sliding mode control for electro-hydraulic servo system

In order to enhance the performance of electro-hydraulic servo system including nonlinearities, parameter uncertainties and load disturbance, a hybrid control scheme, integrating wavelet neural network controller(WNNC)and sliding mode controller is presented. WNNC is the main controller that is used to mimic the equivalent control, and a sliding mode controller is designed to compensate for the difference between the equivalent control and the WNNC. The online adaptive laws are proposed to guarantee the tracking error is asymptotical stability in the Lyapunov stability theorem and Barbalat´s lemma. In addition, in order to relax the requirement of approximation error bound, an estimation law is derived to estimate the error bound. Finally, the theoretical results are illustrated in the design of a controller for an electro-hydraulic servo system compared to the sliding mode controller; computer simulations show the superiority of the proposed design method.