Passive control of an electrohydraulic actuator using an electrohydraulic passive valve

A passive control scheme for bilateral teleoperated one degree of freedom hydraulic actuator is proposed. The overall system enables a human operating a motorized joystick to feel as if he is manipulating a rigid mechanical tool with which the work environment is also in contact. By ensuring that the closed loop system behaves like a passive two port device, safety and stability when coupled to other systems are improved. The control scheme is developed by first passifying a four way directional control valve via active feedback, and then by the design of a passive teleoperation control based on the low frequency dynamics of the passified valve. The coordination error between the joystick and the hydraulic actuator converges to 0 for sufficiently low manipulation bandwidth. Experimental results verifies the characteristics of the control scheme.