Kinematic feature analysis of parallel manipulator systems

This paper presents an in-depth analysis on the kinematic features of parallel manipulators, such as deficiency, singularity, and redundancy. Parallel manipulators under consideration are of a general form, with no restriction on their structure. Three orthogonal instantaneous motion spaces (IMSs) of a parallel manipulator are identified, including deficient, uncontrollable, and controllable IMSs. Based on the IMSs, the deficiency and singularity of a parallel manipulator are described and analyzed, and their remedies are devised. Three types of redundancies of a parallel manipulator are introduced, including the redundancies in serial chain, joint actuation, and parallelism. The three types of redundancies are shown to overcome the singularity of a parallel manipulator, as well as to improve either its dexterity or load capacity