Development of high-power and backdrivable linear electro-hydrostatic actuator

Actuator with high power output and durability is a important factor in developing humanoid robots with high mobility. Development of such actuator with force sensitivity is a challenge. We developed linear electro-hydrostatic actuator (EHA) to realize high-power output, high durability, and backdrivability. This paper presents mechanical design of a linear EHA that reduces friction. Low friction piston seal was employed to significantly improve volumetric efficiency while keeping loss of backdrivability minimum. To test this device, a testing device with reaction mass is proposed. This device can be used to give external force to actuator under dynamic movement with high repeatability. Backdrivability, maximum cylinder force, and frequency response were evaluated to show the efficacy of the proposed actuator.