Xingchao Zhang, Hongbo Wang, Yu Rong, Jianye Niu, Junjie Tian, and Yuansheng Ning
Parallel mechanism, over-constrained, kinematics analysis, stiffness analysis
This paper studies the kinematics and stiffness of a novel 4-degree- of-freedom (DOF) over-constrained parallel mechanisms (PMs). First, a novel over-constrained 2RPU+PRPU PM consisting of two revolute–prismatic–universal (RPU) type legs and one prismatic– revolute–prismatic–universal (PRPU) type leg is proposed, where P, U, and R represent the prismatic joint, universal joint, and revolute joint, respectively. Next, the configuration of the PM is described, the velocity constraint equation of 2RPU+PRPU PM is established, and based on this, the DOF of this PM is analysed. Then, the kinematic models are established, the kinematic performance indexes are established using the screw theory, and the kinematic performance of the 2RPU+PRPU PM is analysed according to these indexes. Finally, the stiffness model of the 2RPU+PRPU PM is deduced using the principle of virtual work and the deformation decomposition method. Meanwhile, the stiffness performance maps of the mechanism under different external loads are obtained based on this model. This work is expected to provide a new idea for the design of PMs.
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