Open AccessElastostatic Stiffness Analysis for the US/UPS Parallel Manipulators
Author(s) -
Weizhong Zhang,
Wei Ye,
Chao Yang
Publication year - 2020
Publication title -
mathematical problems in engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.262
H-Index - 62
eISSN - 1026-7077
pISSN - 1024-123X
DOI - 10.1155/2020/1975428
Subject(s) - stiffness , virtual work , screw theory , direct stiffness method , wrench , stiffness matrix , actuator , work (physics) , finite element method , strain energy , constraint (computer aided design) , position (finance) , control theory (sociology) , mathematics , mechanism (biology) , structural engineering , kinematics , engineering , computer science , mechanical engineering , geometry , classical mechanics , physics , control (management) , finance , artificial intelligence , quantum mechanics , economics , electrical engineering
The virtual joint method (VJM) cannot calculate the strain energy stored in each rod. In order to solve the problem, a modeling method of the elastostatic stiffness was investigated for the UP/UPS parallel manipulators (PMs), taking the example of the 6-SPS PM. The modeling method was based on screw theory, Castigliano’s theorem, and strain energy (where U, P, and S, respectively, denote universal, prismatic, and spherical joints). First, the actuator and constraint wrenches of the mechanism were obtained by screw theory. Second, compact limb stiffness matrices were obtained in terms of strain energy and Castigliano’s second theorem. Finally, analytic expressions for the overall stiffness matrix of the mechanism and the amplitudes of the actuator force were obtained by adopting the virtual work principle and the balance equation for the mobile platform. All relative errors between the results of the analytical model and the finite element model are below 2%, which validates the effectiveness of the elastostatic stiffness model. The virtual work index was adopted to evaluate the stiffness performance of the mechanism, and the results show that the stiffness is not only related to position and orientation but also closely related to the directions of external loads. It is also demonstrated that the method has general adaptability for the stiffness analysis for the US/UPS PMs, laying the foundation for further reasonable dynamic design and optimization of such manipulators.