Extended-state-observer-based pressure compensation anti-disturbance control method for hydraulic secondary regulation system

The hydraulic secondary regulation system, which utilizes hydraulic servo motors for throttle-free operation, is a prevalent energy-saving fluid transmission mechanism. The incorporation of accumulators, while improving energy recovery, also affects the system pressure. Most studies focus on controlling the secondary regulation system within a constant pressure network, which often compromises the accuracy of system position control. To resolve this challenge, this paper introduces a pressure compensation disturbance rejection control strategy based on extended state observation to enhance the performance of secondary regulation systems under variable pressure conditions. A disturbance model for the accumulator's pressure variation is developed, and a pressure compensation term is formulated using system pressure feedback. The influence of displacement tracking errors of the hydraulic servo motor on position control is also considered. An extended state observer is then designed to detect and mitigate the system's residual matching uncertainty disturbances, thereby increasing robustness. A Lyapunov function is used to prove that the proposed control method achieves bounded stability. Experimental results indicate that the proposed method improves control accuracy by 55.2 and 32.1% compared to conventional PID control and adaptive robust control methods, respectively, under fluctuating system pressures. This advancement significantly enhances the position control precision of secondary regulation systems with variable pressure.