Design and Control of a Variable Viscous Damping Actuator (VVDA) for Compliant Robotic Joints

Due to the increasing demand for safe human-robot or environment-robot interaction, the development of intrinsically compliant actuators becomes a key issue to the robotic design. However, the introduction of compliance in an actuation system will increase system oscillations and reduce the mechanical bandwidth of the system making the system difficult to control. In order to solve such problems, this paper proposes a novel Variable Viscous Damping Actuator (VVDA) which has a hydraulic transmission unit placed in parallel with a series elastic transmission element. The hydraulic transmission unit utilizes a servo motor and slider-crank linkage to change the area of internal orifices and therefore regulates its viscous damping coefficient. The dynamic model of the VVDA is then formulated and the orifice effect in the hydraulic transmission unit is analyzed. Experimental results show that the VVDA is able to reduce the vibration in a position control process by actively change the viscous damping of the system.