A Method for Solving the Additional Stiffness Introduced by Flexible Joints in Stewart Platform Based on FEM Modal Analysis

Abstract

The usage of flexible joints has greatly facilitated the widespread application of the Stewart construction mechanism in many advanced fields. This research focuses on the problem that the flexible joints in the Stewart mechanism cause additional stiffness effects on the whole system. A method for solving the additional stiffness of flexible joints combining the finite element method (FEM) is proposed, which avoids the complex theoretical derivation process and allows the advantages of high versatility and accuracy. Three aspects make up the main content. Firstly, based on dynamics theory, the theoretical analysis and demonstration of the method are conducted according to the symmetry characteristics of the Stewart platform. Next, the additional stiffness of a designed Stewart platform with flexible joints was solved following the method proposed, and the obtained results were verified through FEM simulation under the given conditions, which give a maximum natural frequency deviation against the theory of 2.26%. Thirdly, dynamics tests associated with the Stewart platform were conducted, and the deviation between the Stewart Platform’s natural frequencies separately obtained from the tests and the theory does not exceed 5%, which demonstrates the effectiveness and accuracy of the method in engineering applications. This study aims to provide technical support for the development of Stewart mechanisms with flexible joints.