Abstract Comparing with the currently almost exclusively used serial structures, Parallel kinematic robots are a promising alternative in all application fields. The principal advantages of parallel kinematic robot are its high structure stiffness and its ability to reach large acceleration. In parallel kinematic robot, besides active joints-driving mechanism, passive joints is indispensable. These passive joints have more translational and rotational degree of freedom in most cases. The major requirements of these joints are big mobility, high stiffness, small mass and compact structure space. The currently available joints cannot meet these requirements.
