Research On Dynamics Of Compliant Bistalbe Mechanisms

With the rapid development of science and technology and modern industry, theperformance of mechanical products are put forward new demands, and the traditionalrigid mechanisms can not meet the growing needs of people. Compliant mechanismswith fewer parts, shorter assembly time or no assembly,can reduce friction, wear andvibration between components, as well as improve the reliability and accuracy ofmechanism kinematic. Therefore, compliant mechanism has gradually become a newhot spot area of kinematic of machinery. Compliant bistable mechanism is a newresearch direction of compliant mechanism. At present, the domestic and foreignresearches on compliant bistable mechanism mainly concentrate on the aspects ofmechanism kinematics and structure design. However, the study of the dynamics ofcompliant bistable mechanisms is lacking. Needless to say, how to improve thedynamic characteristics of bistable compliant mechanism, has great theoreticalsignificance and practical value for further development, improvement of compliantbistable mechanism theory and expanding the application range of compliant bistablemechanism.By taking the planar compliant bistable mechanisms as subject investigated, thedynamics and synthesis of the compliant mechanisms are studied in aspects of dynamicmodeling, conditions of bistable characteristics, dynamic characteristics and optimaldesign.Firstly, the dynamic models of compliant mechanisms with compliant links arecreated. Fully considering the dynamics of the impact of the flexible links, the dynamicmodel of compliant bistable mechanism is established by pseudo-rigid-body modelwhich is modified on static state. And a numerical example is given to verify thecorrectness of the modeling method. A dynamic model of compliant mechanism haslaid a good foundation for carrying out research work in this paper.Secondly, bistable characteristics of compliant mechanisms are studied.Thebistable characteristics of the compliant mechanism which contains only one flexiblejoint or two flexible joints are respectively studied by the energy theorety and thepseudo-rigid-body model.And it proves the correctness of the theory by the compliantmechanism examples.Thirdly, the dynamic characteristics of compliant mechanisms are investigated. The influence of the geometric parameters of flexible links on the frequencycharacteristics and sensitivity of compliant bistable mechanism is researched.Thedriving characteristics of bistable compliant mechanism is analyzed.And it shows thatthe geometrical parameters of flexible links and the initial position of the mechanismhave impact on the driving characteristics. Then,the variation of mechanism’s dynamicstress and strain in the motion process are analyzed. The value and position of maximalstress were derived through theoretical derivation and finite element simulation. On thebasis of analysis of dynamic stress and strain,the fatigue life of compliant bistableswitch is predicted.Fourthly, optimal designs of compliant bistable mechanisms are investigated.Take the maximum range of mechanism’s motion,reducing the quality and themaximum strain energy as the optimization objectives.And natural frequency anddynamic stresses are taken as constraints. The optimal design of compliant bistableswitch is performed.