Toward High Power-to-Weight Ratio Electro-hydrostatic Actuators for Robots

Electro-hydrostatic actuators (EHAs) exhibit excellent backdrivability and therefore mechanical robustness. However, it has been difficult to design an EHA which satisfies the requirements on the same level of power-to-weight ratio as widely used actuators with gear reducers. To address this challenge, we developed a revolute EHA module realizing a high power-to-weight with a frameless motor and integrated modular design. Its output power was preliminary estimated by formulating its losses prior to the future experiment. In addition, its backdrive performance was experimentally evaluated to demonstrate the superiority of our EHA over gear reducers. The design method, achieving a high power-to-weight ratio and high backdrivability, offers the possibility of the EHA as an alternative to existing robotic actuators.