Research of driving force coordination mechanism in parallel manipulator with actuation redundancy and its performance evaluation

Actuation redundancy makes it possible for parallel manipulator to optimize the driving force distribution when operating scheduled trajectory. As number of actuation exceeding its degrees of freedom, actuation coordination becomes one of the most important issues of redundantly actuated parallel manipulator. This study focuses on the driving force coordination of parallel manipulator with actuation redundancy under scheduled trajectory. In this paper, dynamic model for general redundantly actuated parallel manipulator is established and, with that, driving force coordination mechanism is analyzed. Two new performance indexes, coordination ratio and coordination factor, are put forward to evaluate the parallel manipulator. With the indexes, two methods are studied to improve the control performance of parallel manipulator with actuation redundancy. One is a control algorithm for driving force adjustment to enhance actuation coordination, and the other is control strategy optimization to enhance control stability. Examples with 6PUS + UPU and 3RPR validate the effectiveness of proposed methods.