Structure synthesis of a class of parallel manipulators with fully decoupled projective motion

This paper describes the structure synthesis of a special class of parallel manipulators with fully decoupled motion, that is, a one-to-one correspondence between the instantaneous motion space of the end-effector and the joint space of the manipulator. A notable finding of this study is that a fully decoupled design can be achieved for parallel manipulators with any number of degrees-of-freedom (DOFs) when the rotational DOF of the end-effector is expressed in the form of a projective angle representation. On the basis of the geometrical reasoning of the projective motion interpreted by screw algebra, a systematic approach is developed for synthesizing the structures of f-DOF (f ≤ 6) parallel manipulators with fully decoupled projective motion. Several 2-, 3-, 4-, 5-, and 6-DOF parallel manipulators with fully decoupled projective motion were designed for illustrating the developed method