The effect of joint elasticity on bilateral teleoperation

In applications such as space and surgical robotics, the use of thin, lightweight manipulators and cable-driven end- effectors results in flexibility of the manipulator. In bilateral teleoperation, however, any flexibility in a link or joint of the robot reduces the transparency of teleoperation. In this paper, we analyze master-slave teleoperation transparency under slave robot joint elasticity and evaluate the added benefits of using extra sensors at the end-effector of the elastic-joint robot. It is shown that velocity (or position) feedback from the output shaft of the elastic joint improves free-space position tracking performance, which in the absence of such feedback is hampered by the joint´s anti-resonance. Also, when the interaction forces with an environment are measured by a force sensor and fed back to the user, end-effector velocity feedback improves hard-contact force tracking performance. If the operating trajectories correspond to low frequencies, both free-space position tracking and hard-contact force tracking are satisfactory regardless of end-effector feedback, yet the elasticity in the joint will be transmitted to the user during a hard contact task unless end-effector velocity feedback is used.