New type backstepping adaptive controller for electro-hydraulic system

YUAN Zhaohui, YUAN Ming

(Department of Automatic Control, Northwestern Polytechnical University, Xi′an 710072, China)

Abstract: Aiming at controlling a class of nonmatching uncertain nonlinear systems, a new type backstepping adaptive control algorithm which is based on the basic backstepping control method was proposed. The algorithm does not need to comprehend the controlled system uncertain function as well as its derivative bound. Adaptive control law and CMAC weight adjustment information was proposed based on Lyapunov function. The calculation expansion problem was avoided by using the CMAC to approximate the system uncertainties and the derivative of virtual control input online. In addition, the discontinuous robust control term was added in the last step of backstepping recursion to overcome the CMAC online approximation error of uncertainties. For solving the chattering problem caused by the discontinuous input of discontinuous robust control term, the lowpass filter was added before the practical control input. Finally, the proposed control algorithm was applied to the electric hydraulic servo system. The stability analysis shows that the control method can guarantee the output tracking error asymptotically convergent to zero. The simulation results indicate that the algorithm is effective and robust to system uncertainties and unknown disturbances.

Key words: electrohydraulic servo system; nonlinear system; adaptive backstepping control; online learning system; lowpass filter