Optimization of a redundantly actuated parallel kinematic mechanism for a 5-degree-of-freedom hybrid machine tool

In this article, a novel redundant 3-degree-of-freedom parallel kinematic mechanism with high rotational capability is proposed and alternate configurations are presented. Taking the motion/force transmissibility into consideration, a local minimized transmission index is introduced and suggested to act as the performance evaluation criterion for this redundantly actuated parallel kinematic mechanism. On this basis, the optimum design of the proposed parallel kinematic mechanism is carried out and its rotational capability is investigated. The result indicates that the rotational capability of the proposed mechanism can surpass 115 degrees. Compared with traditional parallel kinematic mechanisms, this represents a substantial advantage for practical applications. Using the redundant parallel kinematic mechanism as the parallel module, a redundant hybrid machine tool capable of five-face machining in one setup is developed and applied in the manufacture of parts with freeform surfaces.