Kinematic analysis of generalized parallel manipulator systems

This paper investigates the kinematic features of a general form of parallel manipulator systems, in terms of deficiency, singularity and redundancy, and its kinematic performance in terms of dexterity or load capacity. First, the task space is decomposed into three orthogonal instantaneous motion spaces (IMSs) of a parallel manipulator: deficient, uncontrollable, and controllable IMSs. Based on the IMSs, the deficiency and singularity of a parallel manipulator are described and explored to devise their remedies. Three types of redundancies of a parallel manipulator are then introduced by increasing actuators and limbs in three different ways. Next, the manipulabilities of a parallel manipulator are defined under the hypothetical actuation of joints, such as actuation, unactuation and freezing. Based on the characterization of the manipulabilities, the IMSs are identified to derive the formulas for the deficiency and singularity. The derived formulas serve as an effective tool for analyzing the kinematic features and kinematic performance of a parallel manipulator. The three types of redundancies are shown to improve either dexterity or load capacity of a parallel manipulator, as well as to prevent its singularity