Bilateral Control Between Electric and Hydraulic Actuators Using Linearization of Hydraulic Actuators

In this study, bilateral control between electric and hydraulic actuators is investigated. Bilateral control realizes telemanipulation of remote robots with the sense of touch. We focus on the system of local (master) robots, manipulated by operators that are driven by electric actuators, and slave robots, which work in remote places that are driven by hydraulic actuators. To obtain bilateral control in this situation, we find that combination of three key techniques is necessary. The first key is oblique coordinate control, which can decouple position and force controllers of bilateral control. The second key is linearization of hydraulic actuators as third-order systems including oil compression by using disturbance observers. In the absence of linearization, the design becomes practically impossible because of the need to apply complicated models. Since the master robots are second-order systems, and the slave robots are linearized as third-order systems, oblique coordinate control cannot be implemented. Then, the last key is the agreement of system order of electric and hydraulic actuators by using a pseudodifferentiator. Two conventional controllers and the proposed method are experimentally and analytically compared. The proposed method shows the best tracking performance and is the most stable in contact control among the three controllers.