Design and Evaluation of Cable-driven Manipulator with Motion-decoupled Joints

In this paper, we present the design of a cable-driven servomanipulator with motion-decoupled joints. The cable transmission connecting the actuators to the joints remotely, causes a motion coupling problem where the length or tension of the cable is changed due to an unwanted motion interference at joints. To maintain the cable length constant regardless of the rotation of the arm, we used three different schemes such as a motion-decoupled structure for a shoulder joint, a novel motion decoupling mechanism for an elbow joint, and an optimization of the geometric parameters for a wrist joint. Experimental results show that the overall cable length variation at the cable-driven joints is less than 0.01 mm. Therefore, we expect that the suggested decoupling methods could assure a more accurate motion control for a cable-driven servomanipulator.