Type Synthesis of Planar Parallel Mechanism Incorporating Actuated Limb with Zero/One Constraint with Set Conception

Abstract

This paper presents a method of type synthesis for planar parallel mechanisms (PPMs) incorporating actuated limbs with zero/one constraint with set conception. Firstly, according to their contributions to the moving platform, the limbs of PPMs can be classified as four categories: actuated limb with zero constraint, fully-constrained limb with zero actuator, fully-constrained limb with one actuator and under-constrained limb with one actuator. Followed by the descriptions of actuated space and constrained space for the end of the limbs by virtue of the screw theory, the type syntheses of the four type limbs are carried out. Then different sets and functions are defined respectively, whose elements and variables are the topologies of four type limbs. The different function values and the composition principle of PPMs lead to existence of PPMs topologies by four solutions. Finally, taking three typical PPMs with linear motors for examples, their virtual prototypes are obtained with commercial 3-dimensional CAD software.