Energy recovery charging of an accumulator in a low-pressure compensation circuit of an electro-hydrostatic actuator

An electro-hydrostatic actuator (EHA) comprising:

• a main hydraulic circuit having installed therein:
• a bidirectional pump-motor rotationally coupled to an electric motor that is operable to drive a pumping operation of said bidirectional pump-motor;
• a hydraulic cylinder;
• and
• main circuit valving and connections between the first bidirectional pump-motor and the hydraulic cylinder by which the EHA is operable in four distinct operating quadrants, including a first actuator-extending pumping quadrant, a second actuator-extending motoring quadrant, a third actuator-retracting pumping quadrant and a fourth actuator-retracting motoring quadrant;
• and
• in connection with the main circuit, a low-pressure charging circuit having installed therein:
• an accumulator;
• a reservoir tank;
• a charge pump;
• and
• charge circuit valving co-operable with the accumulator and the charge pump to (i) during the third and fourth quadrants, charge the accumulator using return flow from the main hydraulic circuit;
• (ii) during the first and second quadrants, in instances thereof characterized by a charged state of the accumulator, deliver compensatory flow to the main hydraulic circuit from the accumulator;
• and (iii) during the first and second quadrants, in instances thereof characterized by an inadequately charged state of the accumulator, deliver compensatory flow to the main hydraulic circuit from the charge pump;
• wherein said charge circuit valving comprises an electro-proportional pressure-reducing valve configured to act on the compensatory flow from the accumulator.