Type synthesis of symmertrical non-overconstrained 3-dof translational parallel manipulators based on srew theory

Based on screw theory,a systematic method is proposed to synthesis symmertrical non-overconstrained 3-DOF translational parallel manipulators(TPMs). Firstly,the configuration conditions of non-overconstrained TPMs are analysis. The generation of symmertrical non-overconstrained TPMs is reduced to design the structure of serial chains with one infinite pitch wrench,and to combine the same serial chains inparallel.Finally,making sure that, the union of the wrench for the same serial chains in each combination constitutes a three infinite pitch wrench system.we get all the 3-legged symmertrical non-overconstrained TPMs.