Kinematics of Elastic Tendons for Tendon-Driven Manipulators With Transmission Friction

This article proposes a novel differential kinematics of elastic tendons for tendon-driven manipulators where tendons transmit actuator force/torque to remote links via a train of pulleys. The local variability of tension and longitudinal speed in each tendon is carefully investigated in terms of the rest lengths of the virtually partitioned tendon segments along the tendon. A significant attention is paid to building a proper friction-tension mechanic model between the pulleys and tendons to identify the no-slip points that are important to be used as kinematic constraints. The kinematic relations of tendon are obtained for two possible types of tendon-pulley transmission, i.e., free-free ended and fixed-free ended types, and then a complete kinematics of tendon is formulated by augmenting all the kinematic relations existing in the entire system. Simulation and experimental results are provided to validate the proposed kinematics of tendon by comparing with a previous simple spring model where the tension was determined by the relative positions of consecutive pulleys.