High-Precision Control Solution for Asymmetrical Electro-Hydrostatic Actuators Based on the Three-Port Pump and Disturbance Observers

Flow mismatch, strong nonlinearity, and complex disturbance are the main challenges that electro-hydrostatic actuator (EHA) control faces. This article proposes a three-port piston pump to replace the two-port piston pump in traditional EHA to solve the flow mismatch problem caused by asymmetric cylinders. Then, for the complex disturbance problem in EHA control, an extended state observer and a nonlinear disturbance observer are designed to estimate matched and mismatched disturbances, respectively. On this basis, the virtual decomposition control method is adopted. The EHA is virtually decomposed into three subsystems, and the controllers of each subsystem are designed separately to realize the high-precision nonlinear control of the EHA. Next, the stability of the proposed control method and observer is proved. Finally, the proposed three-port pump, observer, and controller are systematically verified based on the simulation model and the EHA experimental platform. Simulation and experimental results show that the proposed three-port pump solves the flow mismatch problem without increasing the weight and volume of the EHA. The designed two observers can accurately estimate the matching and mismatching disturbances during the EHA operation. By combining designed observers and the virtual decomposition control method, the accuracy and robustness of EHA control can be greatly improved.