A Double Closed-Loop Digital Hydraulic Cylinder Position System Based on Global Fast Terminal Sliding Mode Active Disturbance Rejection Control

Due to the coupling of multiple nonlinear factors in the position control system of the double closed-loop digital hydraulic cylinder, achieving precise and stable control of complex nonlinear systems with a single structural controller is difficult. To address this problem, we propose a Global Fast Terminal Sliding Mode Active Disturbance Rejection Control (GFTSMADRC). Firstly, by focusing on the mathematical model of the current double closed-loop digital hydraulic cylinder, the high-order nonlinear state equation of the system is derived, and employing active disturbance rejection control (ADRC), the high-order nonlinear system is transformed into a second-order integral series control system. Secondly, we propose Sliding Mode Active Disturbance Rejection Control (SMADRC) by integrating sliding mode variable structure control. Thirdly, to further enhance system performance, we propose a GFTSMADRC strategy by incorporating global fast terminal sliding mode variable structure control. The control law and adaptive law of the system are derived based on the Lyapunov stability theorem. Specifically, the effectiveness of the proposed control method is validated through simulation and experimentation.