Position Control of Electro‐Hydraulic Actuator System With Disturbances Compensation

ABSTRACT This paper proposes a new output feedback controller based on global fast terminal sliding mode with disturbances rejection to achieve accurate position tracking control for electro‐hydraulic cylinder system. The typical mathematical model of the asymmetric cylinder electro‐hydraulic system is established as Brunovsky form. Then high‐order sliding mode observer is designed to estimate system states with only available displacement signal, and nonlinear disturbance observer is introduced to estimate and compensate for lumped disturbances including external disturbances, modeling errors and parameter uncertainties. Besides, a global fast terminal sliding mode control method is proposed to improve system convergence speed and position tracking accuracy, whose stability is proved through Lyapunov theory. Furthermore, simulations are carried out to verify the estimation performance of the designed state observer and disturbance observer, and the estimation accuracy of the disturbance observer reaches 82.71%. Finally, an asymmetric cylinder test rig is constructed and the experimental results show that the tracking accuracy of sinusoidal motion with 100 mm amplitude and step motion with 20 mm amplitude can reach 97.2% and 93.9% respectively compared with the total stroke of the motion, indicating the superiority of the designed output feedback controller.