Development of a hybrid actuator with controllable mechanical damping

This paper presents a novel hybrid actuator with controllable mechanical damping. It has been developed to provide subsequently the actuation means for haptic interfaces that can demonstrate intrinsic passive performance when rendering hard contacts. The overall actuator is a dual actuation system where one actuator is responsible for generating the joint motion while the second is dedicated to regulating the physical damping through a semi-active friction mechanism. This semi active friction mechanism applies a purely dissipative torque on the joint, which can be continuously controlled to render damping levels ranging from completely free to heavily damped and even a completely locked joint. The present work focuses mainly on the mechatronic details of the actuator design and in particular on the modelling and control of the damper. The proposed variable damping mechanism is evaluated in a simple 1-DOF joint. Experimental results are presented to demonstrate that the unit is capable of replicating physical damping with adequate performance.