Abstract: Hybrid series-parallel mechanism, which contains the advantages of both series and parallel mechanisms, is used more and more widely in the manufacturing equipment for parts with complex free curved face. A 3-DOF parallel 3-PSP mechanism, which can realize one translational and two rotational motions, is proposed. The 3-PSP mechanism has accompanying motions. According to the analysis of motion mode, tilt-torsion angle for describing the motion of moving platform is adopted instead of traditional Euler angle, and based on that, kinematic model is built to solve the complete kinematic problem including accompanying motions and passive joint variables. Furthermore, the range of the joint, velocity characteristic, and accuracy characteristic are analyzed to demonstrate that the 3-PSP mechanism is fully suitable for parallel module in hybrid series-parallel frame which can fulfill the requirement of the complex parts in aerial, space, and automotive fields.

Key words: 3-DOF parallel mechanism, Accuracy analysis, Kinematics