Dynamics Analysis And Optimization Of Planar Compliant Four-bar Mechanism

Compliant mechanism motion and function depend on the elastic deformation of compliant links. Compliant mechanisms have many advantages such as it has less even no kinematic pairs, no friction and others aspects. Contrast with the traditional mechanisms, it has great improvements in performance because of these advantages. Compliant links can improve the performance of the traditional mechanisms, so, compliant mechanisms have attracted much attention. Originally, the research results of compliant mechanism are mainly about static analysis and structure design. In recent years, the topology optimization of compliant mechanism design gradually becomes a research hotspot. Most of these researches are only been short of the study of the dynamics of compliant mechanisms and fatigue damages due to the dynamic stress and fatigue reliability. Previously, the dynamics analysis of compliant mechanisms have been investigated, but mostly analysis are about flexure hinge, compliant links and overall analysis are deficiency. Because the movement characteristics of the compliant mechanism are overall in the application, the research on the overall movement of compliant mechanisms has important theoretical significance and application value.In this paper, taking the planar compliant mechanisms as the research object, the main contents of dynamics and synthesis of the compliant mechanisms are in aspects of dynamic modeling, dynamic analysis, optimal design and reliability.Firstly, the dynamic models of compliant mechanisms with compliant links are established. Considering the large deflection of compliant links, the dynamic characteristics of the compliant links is inferred. The dynamics model for any compliant four-bar mechanisms is deduced.Secondly, the dynamic characteristics of compliant mechanisms are investigated. The natural frequency, dynamic stress and strain of the compliant mechanism are analyzed. The system sensitivity about design parameters is also inferred. Through modal analysis can infer that, in the later stage of vibration-order modal, there will be distortions of the links inevitably. The distortions of the links will have bad impacts in the performance of the enhancement and improvement. The dynamic analysis provides optimization goals for compliant mechanisms.Thirdly, optimal design of compliant mechanisms is investigated. Based on the characteristics analysis, the standard of material selection is discussed. Taken the maximum equivalent stress the compliant mechanisms could absorbed and the minimum total mass as the optimization objective, and taken natural frequency and dynamic stress as the constraints, the optimal design of compliant mechanism with compliant links is performed. Through explaining the characteristics of all kinds of different materials and their different application scope, the optimization of compliant mechanism can used to change parameters, in addition to change the material to achieve the purpose of optimization.Finally, reliability analysis of compliant mechanisms is discussed. Based on the reliability of the significance and characteristic, the necessary of reliability analysis which carried out on the mechanisms can be illustrated. Based on the Mr Cumulative fatigue damage theory, the fatigue life of the flexible bar is predicted. According to the fatigue cumulative damage theory, fatigue life analysis was carried out on the links, the position of the stress concentration and life insufficient can be placed. Then the reliability of the compliant mechanisms is analyzed.