Bilateral control between electric and electro-hydrostatic actuators using feedback modulator

Abstract

This study investigates bilateral control between electric and electro-hydrostatic actuators (EHAs) using a feedback modulator (FM). In bilateral control, we apply a local robot as a master driven by an electric actuator and a remote robot as a slave driven by an EHA. EHAs exhibit a high power-to-weight ratio with low energy loss. However, there would be difficulties when it comes to control designs because of non-linear characteristics such as friction. In order to exhibit high control performance of bilateral control, the effect of static friction which occurs in the hydraulic actuator of the slave has to be eliminated. An FM is applied to reduce the effect of static friction of the hydraulic systems and to enhance responses of actuators. We apply the FM to an oblique-coordinate-bilateral-control system and investigate the control performance. The experimental results indicate that the FM reduced the effect of static friction and the position control performance was improved. Besides, the conventional method is not able to transmit the reaction force because of the large static friction in the low-speed domain. However, the proposed method stabilizes the contact motion by applying the FM.