Abstract: A method for storing and reutilizing energy during operation of a hydrostatic actuator (EHA) having a hydraulic cylinder, a first bidirectional pump-motor rotationally coupled to an electric motor, and EHA valving and connections between the first pump-motor and the hydraulic cylinder. During at least one of two motoring quadrants, a hydraulic accumulator is charged using a second pump-motor whose rotation is driven by load-driven motoring of the first bidirectional pump-motor. During at least one of the pumping quadrants, driven rotation is imparted to the second pump-motor using stored energy from the accumulator, and said driven rotation of the second pump-motor is used to augment powered rotation of the first bidirectional pump-motor by the electric motor.

Abstract: A single-rod hydrostatic actuator or pump-controlled actuator, comprises a hydrostatic pump connected in a closed circuit to a single-rod hydraulic cylinder where the cylinder velocity is directly controlled by the pump flow, without the need of intermediary valves. Due to the absence of throttling losses, the efficiency of hydrostatic actuators is considerably superior to the efficiency of conventional valve-controlled circuits. However, because of the differential areas at the cap and rod sides of the cylinder, the flows coming into and out of the cylinder do not match. Several attempts have been made to this date to produce a stable, robust and reliable circuit that can be used in everyday applications but no circuit has ever been conceived to reach the high standards of reliability and robustness required by industry. The current invention solves the problem of the differential flows with a design that is reliable, oscillation-free and robust.

Abstract: A single-rod hydrostatic actuator or pump-controlled actuator, comprises a hydrostatic pump connected in a closed circuit to a single-rod hydraulic cylinder where the cylinder velocity is directly controlled by the pump flow, without the need of intermediary valves. Due to the absence of throttling losses, the efficiency of hydrostatic actuators is considerably superior to the efficiency of conventional valve-controlled circuits. However, because of the differential areas at the cap and rod sides of the cylinder, the flows coming into and out of the cylinder do not match. Several attempts have been made to this date to produce a stable, robust and reliable circuit that can be used in everyday applications but no circuit has ever been conceived to reach the high standards of reliability and robustness required by industry. The current invention solves the problem of the differential flows with a design that is reliable, oscillation-free and robust.