Adaptive Backstepping Control of Electro Hydrostatic Actuator with Improved Parameter Estimation

Electro hydrostatic actuator (EHA) is a pump-controlled hydraulic system and has been successfully applied in the aeronautical field by the advantages of miniaturization and energy-savings. However, due to the high order dynamics and the existence of various nonlinearities and uncertainties in the EHA system, it is a challenge to achieve accurate motion control. Most of the recent research on adaptive hydraulic control only focuses on the position tracking control performance while the parameter adaptation performance is unsatisfying. Therefore, this paper proposes a adaptive backstepping control algorithm for EHA system, especially considering improved hydraulic parameter estimation. Firstly, the parameter estimation errors are formulated by introducing an auxiliary filter operation that avoided used the system acceleration information. Then a novel adaptive law is designed to update the parameter estimation using both the position tracking errors and the estimation errors which improve the parameter estimation performance compared traditional adaptive law. Moreover, due to the higher-order dynamics of the system, the motion controller is designed using a modified backstepping method, in which the proposed adaptive law is used to on-line estimate the unknown parameters at each step. Theoretically, the stability of the EHA system and asymptotic motion tracking and parameter convergence performance can be proved by Lyapunov function. Finally, comparative simulations are conducted to vaelidata the effectiveness and superiority of the proposed control approach.