Improving the pose accuracy of a planar 3RRR parallel manipulator using kinematic redundancy and optimized switching patterns

In the present paper kinematic redundancy is proposed in order to improve the achievable pose accuracy of a parallel robot's traveling platform. An additional prismatic actuator is applied to a 3RRR planar parallel manipulator. It allows a selective reconfiguration of the kinematic structure according to several optimization criteria. Based on an index that we denote the gain of the Jacobian matrix the position of the redundant actuator is changed in a discrete manner. The resulting optimized switching patterns lead to a great increase of the traveling platform's pose accuracy. Between two switching operations the prismatic actuator's position is supposed to be locked. Hence, sources of error, e.g. the joint clearance, can be minimized. Several analysis examples demonstrate the effectiveness of the proposed concept in combination with the developed optimization procedure.