Systematic Approach for Structure Analysis of 3-DoF Parallel Manipulators with Special Displacement

Screw theory is used to analysis limb structure for 3-degree-of freedom (DoF) parallel manipulators. The procedure of limb joint screw system is consummated, and a better completely list of the limb structure with the special displacement for 3-DoF parallel manipulators is explored. Given the limb wrenches system, the joint screws are determined by a linear combination of the basis screws, the characteristics with the special displacement of the moving platform will be enumerated and classified according to the screws system of joints and links making up the limbs. The kinematical property of platform and the geometrical conditions for special displacement are presented.