Alternative Motion Control of a Parallel Mechanism With Actuation Redundancy

Among the advantages of redundantly actuated mechanisms, one can mention the higher operational robustness, the feasibility of reduced power actuators, increasing the load capacity of the mechanism. This work proposes a motion control for a parallel mechanism with actuation redundancy, characterized by simplicity and effectiveness related to the implementation and accuracy, respectively. Hence, an experimental test-bed is built with three main systems, where the end-effector location is directly determined. Regarding the motion planning, some indices are proposed in order to select the appropriate non-redundant actuation modes that can achieve comparable performances with respect to the redundant one. Experimental results evidenced a good correlation between those indices and the path tracking error. For the longest path, the mean and maximum values of this metric for a non-redundant actuation mode were 20 % lower than the redundant mode. Moreover, other experimental tests revealed that the proposed control has the capability to switch between the actuation modes and to overcome type-II singularities.