Force control of electro-hydrostatic actuator using pressure control considering torque efficiency

To develop a robot system for collaboration with humans, robots are required to perform accurate external force detection and flexible motion from the prespective of safety. Electro-hydrostatic actuators (EHAs) can achieve high backdrivability mechanically. However, in a hydraulic system, torque efficiency decreases due to nonlinear elements, including friction and the internal leakage of hydraulic fluid, which results in lower backdrivability. In other words, in EHAs that can achieve high backdrivability mechanically, further improvement of backdrivability can be achieved by performing force control through nonlinear element compensation. Therefore, herein, we modeled the torque efficiency and attempted to improve the force control performance by model-based pressure control.