The Analysis And Optimal Design Based On Reliability Of Compliant Mechanisms

Traditional rigid-body mechanisms present some disadvantages, including large number of parts, high cost of machining and fitting, unavoidable clearance and friction, and so on. But compliant mechanisms happen to go with the harmonious tide of human being and nature, and become a hot research in both domestic and overseas mechanism field, because of its particular performances and characteristics, and its widely application in medical treatment, communication, microelectronmechanical system s(MEMS), etc. Research on compliant mechanisms can not only develop the theories of related subjects, but also apply itself to solving the practical technical problems of production and assembly, and satisfy the practical demand of national economy and social life. Based on the above aspects, the following aspects are studied in this dissertation.Firstly, the configurations of different flexible members in the compliant mechanisms are analyzed, and the main structural parameters of the pseudo-rigid- body model are determined. Based on the Bernoulli-Euler beam equation which is generally applicable to a flexible beam, the deflection path or track of the flexible member is analyzed, and the deflection is simulated with Matlab. Considering the equivalent force-deflection characteristics between physical model and original compliant mechanism, the pseudo-rigid-body model of compliant mechanism is established, and the unknown parameters are determined by the methods of optimization and polyfit.Next, this paper develop a optimal design method of compliant mechanisms based on fatigue reliability. Based on the pseudo-rigid-body model and aiming at the maximal reliability, an optimal design method of the compliant mechanism is developed. Firstly, the reliability model of the random variables is established and the method of conversion of the probabilistic constraints to deterministic forms is presented. Secondly, considering of the deflection characteristic of the compliant mechanism, the stochastic endurance strength and the maximal stress are calculated. Some typical constraints are analyzed. Finally, the numerical results of an example are obtained on the basis of the previous analysis, which show the validity of the method.Finally, the actuation characteristic of large-deflection compliant mechanisms is analyzed as a primary study. In the first place, different flexible members in the compliant mechanisms are modeled according to the pseudo-rigid-body model method; Next, in term of the deflection ormotion requirement of the follower members, the physical model is analyzed with the theories of rigid mechanisms when the deflection bounds of flexible members is considered at the same time, and the actuation characteristic of the initiative member is gained.