An Improved Nonlinear Extended Disturbance Observer for Sliding Mode Control in Electro-Hydraulic Servo System

Nonlinearities and unknown disturbances are widely present in mechanical systems. This study investigates an improved nonlinear extended disturbance observer and its application in electro-hydraulic servo system, which represents a typical nonlinear system. The focus lies in estimating the external disturbance and its nth-order derivates of the system to enhance the robustness and precision of the control system. Additionally, we introduce a high gain observer dedicated to estimating the system's velocity. Finally, we establish a sliding mode controller based on the improved disturbance observer and high gain observer, aiming to mitigate the impact of external force disturbances. Comparative experiments have been conducted to prove the effectiveness of this approach.