Abstract: In order to describe the dynamic characteristics of a compliant mechanism, the dynamic model thereof is built. Based on the finite element method, the dynamic equation of compliant mechanism is developed by using Lagrange equation. On this basis, the natural frequencies and modes of the mechanism are derived. A method for calculating the sensitivity of natural frequencies and modes to the design variables is then presented. An algorithm for calculating the strain at any point on a flexible link in the compliant mechanism is derived. Nonlinear terms in the strain are also reckoned in the algorithm. The dynamic stress at any position on the flexible link is solved, and the maximum stress and its position on the link at any time are also calculated. The numerical simulation of a compliant four-bar mechanism indicates that the dynamic characteristic analysis of compliant mechanism based on finite element is feasible and effective, and the analysis on strain and dynamic stress of the link of compliant mechanism has important significance to the optimization design of compliant mechanisms.

Key words: Compliant mechanisms, Dynamic characteristics, Dynamic model, Finite element method