Inverse Transmission Model and Compensation Control of a Single-Tendon-Sheath Actuator

Tendon-sheath actuation mechanism is popular in many applications such as surgical robots, robotic hands, and exoskeleton devices due to its simplicity, dexterity, and remote transmission. There exist, however, undesirable nonlinear dynamic properties like backlash, hysteresis, and friction in tendon-sheath transmission. Controlling the distal-end position and force accurately is a very challenging task, since the needed sensors can hardly be placed at the distal end of the system. This paper develops a displacement transmission model of a single-tendon-sheath transmission system based on the force transmission model and proposes a new approach to control the distal-end force and position by inverse transmission without any feedback from the output side. The inverse model is calibrated by offline measurements using the sensors mounted at the proximal end. An experimental setup of single-tendon-sheath actuation is presented, and the improved control performance, with respect to distal-end position and force tracking, is validated by experiments.