Coordinated Operation of Dual-Pump Electro-Hydrostatic Actuators for Advanced Motion Control

Electro-hydrostatic actuators (EHAs) are highly energy-efficient, directly controlled by variable-speed or variable-displacement pumps. Thus, the control performance completely relies on the pump, but the pump often suffers from low flow accuracy and dynamic response problems when rotating at a low speed or starting from zero speed. To further enhance the control performance of the EHA, advanced motion control with coordinated operation modes is developed herein, specifically for a dual-pump EHA. While still ensuring power source redundancy for safety in applications like aviation and aerospace, the dual-pump architecture is not treated as a simple enhancement of the single-pump setup nor as a typical dual-pump EHA. Instead, the dual pumps are coordinated and operate in counter-rotating directions, and the flow rates of the two pumps are subtracted and directed to the hydraulic cylinder. This configuration eliminates the essential reversal of the pump and improves dynamic performance when the cylinder changes directions. First, the working principles are defined and formulated to enable coordination of the dual pumps. Then, a nonlinear model-based adaptive robust controller is developed to manage the nonlinearities and uncertainties of the EHA system. Finally, comparative experiments are conducted with a typical single-pump EHA and a typical dual-pump EHA, demonstrating higher tracking accuracy and faster dynamic response.