Tendon-Driven Manipulator Actuated by Magnetorheological Clutches Exhibiting Both High-Power and Soft Motion Capabilities

Tendon-driven manipulators (TDMs) are capable of large workspaces and low link inertias in compact embodiments. However, as most TDMs are powered by electromechanical actuators, their performance is fundamentally limited by either the high output inertia of electric geared motors, or by the large volume and weight of direct-drive electric motors. To improve upon the conventional TDM designs, this paper presents a TDM actuated by magnetorheological (MR) clutches. The MR-TDM concept combines the advantages of lightweight electric geared motors with the high dynamic performance of MR clutches. The main objective of this paper is to investigate the overall performance of the MR-TDM and demonstrate its wide range of applications. Analytical studies show the higher open-loop natural frequency (60 Hz) and lower reflected output inertia of the MR-TDM compared to the TDM powered by traditional actuators. Furthermore, experiments with a 2-DOF MR-TDM prototype demonstrate the usefulness of the approach for a wide variety of tasks ranging from a soft and precise control to a high impulse response and fast trajectory tracking.