Characteristic investigation of digital control four quadrant electro-hydrostatic actuator with separated hydraulic motor

The asymmetric electro-hydrostatic actuator (EHA) is a promising distributed hydraulic actuation solution for the more-electric aircraft (MEA). However, the flow asymmetry is a common problem causing the poor position control accuracy and dynamics of EHA. To achieve good flow control in all quadrants and save energy in the assistive quadrants, a digital control four quadrant electro-hydrostatic actuator with a separated hydraulic motor using a novel four-quadrant division principle was proposed in this article. The theoretical model of the proposed EHA has been developed in MATLAB/Simulink and validated in the experiments. The theoretical results indicated that the increased external force allows the proposed EHA to have a constantly and partly linearly and varied motion velocity of the cylinder piston in the resistive and assistive quadrants, and the latter is determined by the specific external forces of 0.5 and 2.8 kN, respectively, in the extension and retraction quadrants. Compared with EHA without SHM, in the second and fourth quadrants, the energy dissipation is reduced by 104% and 36.7%, respectively, while the motion velocity of the cylinder piston is reduced by 12.9% and 25.6%, respectively. The theoretical and experimental results indicated that the proposed four quadrants division method effectively corrects the misjudgment of quadrants by using the existing four quadrants division method under the lower external force.