Determination of Optimal Wrench-closure Configuration of Reconfigurable Cable-driven Parallel Robots to Move on a Given Trajectory

Because of the fact that cable-driven parallel robot ​possess limited moment resisting/exerting capabilities and relatively small orientation workspaces, in this paper, a method for determination of optimal configuration of reconfigurable cable-driven parallel robots is presented to improve their performance. In such robots, actuators can move the cable attachment points on the base with respect to the motion of the end-effector in its trajectory. In the determined configuration, any external wrench on the end-effector can be balanced, using cable forces for all poses near to a pose of the robot. The largest wrench-closure circular zone centered at an arbitrary point of a trajectory for a given range of orientation around a reference orientation of the end-effector is computed. Taking the area of such zone into account and with the aim of enlarging them, the optimal configuration of the robot is determined. The optimal configuration is found by appropriately changing the position of the moving attachment points on the base of the robots. By applying this procedure on a number of points on a given trajectory iteratively, proper actuation schemes are obtained. In this paper, this method is utilized for reconfigurable planar cable-driven parallel robots and the quality of their actuation schemes is compared with the robots with fixed cable attachment points on