Abstract: Aiming at the decrease of reverse drive performance caused by static friction, backlash and oil leakage on electro-hydrostatic actuator (EHA), a high-precision force feedback estimation method based on the combination of three controllers was proposed. Firstly, the static friction was compensated by a feedback modulator, and the relative speed between the motor side and the load side was suppressed by using a backlash and oil leakage compensator (without any model). Then, a force feedback observer composed of a pressure sensor and an encoder was proposed. Finally, the actual test was carried out on an experimental device composed of hydraulic actuator and 1-DOF mechanical arm. The research results show that comparing with the traditional pressure sensor, the RMS error of the reaction torque obtained by the force feedback observer of the traditional pressure sensor can be reduced by 3.31 N·m, and the force feedback can be estimated very accurately.

Key words: electric hydrostatic actuator（EHA）; force feedback estimation; static friction compensation; compensation of backlash; oil leakage compensation