Mechatronic design of a class of planar cable-driven parallel robots

In this paper, a novel class of planar cable-driven parallel robots is discussed. The design allows an arbitrary rotation of the end effector by wrapping the cables around a cylindrical fixture on the end-effector platform. In contrast to the state of the art, this results in a simple and robust design without additional moving parts attached to the end effector. The inverse kinematics and dynamical equations of motion for this class of robot are derived and analyzed. Furthermore, the motor redundancy is resolved by enforcing a required tension in the cables. Classical manipulability measures known from the literature are found to be inappropriate for the analysis of cable-driven robots. In order to capture the minimum tension in the cables and the directional dependence of the achievable forces, which are the determining factors for the workspace, a new force manipulability measure is employed. The mechanical design of an experimental setup is presented and the main design choices are elaborated. The experimental results demonstrate the feasibility of the proposed approach and validate the theoretical investigations.