ANALYSIS OF HYBRID CABLE-ACTUATED PARALLEL MANIPULATORS WITH A CONSTRAINING LEG FOR LOWER-DEGREE-OF-FREEDOM OPERATION

This paper presents a kinetostatic analysis of a class of hybrid cable-driven parallel manipulators consisting of cables and a rigid-link serial leg for lower-degree-of-freedom tasks. The serial leg provides the task constraints and the cables provide the required actuation to move the platform in the task space. Having a rigid-link serial leg providing the required constraints for the moving platform in lower-degree-of-freedom applications reduces the number of cables required to support the moving platform in the task space. As a result, the manipulator can be designed with fewer cables and actuators. In order for the manipulator to balance arbitrary applied wrenches, redundant actuation is required. This redundant actuation can be obtained from a redundant actuator mounted on one (or more) serial-leg joint(s). Conditions for analyzing the capability of the redundant actuation to generate cable tension are explained in the paper. A discussion is also given on the optimization of the cable layout and the redundant actuator forces to minimize the tension generated in the cables.