Improvement Solution for the Electro-Hydrostatic Actuator with Variable Displacement Pump Used in Aircraft Flight Controls

In order to control an electro-hydrostatic actuator (EHS), as is well known in the literature, it is possible either to modify the speed and direction of rotation of the electric motor or to vary the displacement of the hydraulic pump. In a previous paper, the advantages and disadvantages of each solution were highlighted. Varying only the motor speed leads to demanding operating conditions for the electric motor, whereas varying only the hydraulic pump displacement results in continuous energy consumption that becomes excessive during long-duration flights. Combined solutions for controlling an EHS can also be found in the literature, but they generally require highly sophisticated control algorithms. In this paper, a solution is proposed in which the electric motor is switched off when the EHS remains in an idle condition for long periods of time. In this way, the large amount of energy consumed during idle operation is eliminated, while preserving the improved dynamic performance associated with the variable-displacement pump configuration.