Research On Reliability Analysis And Optimization Design Of Uncertain Elastic Mechanism

Modern mechanisms are trending to high speed, light mass and high precision, the research on the reliability analysis and optimization design based on Kineto-Elastiodynamics has important theoretical significance and research worthiness. In this paper, the random reliability model, fuzzy reliability model and non-probabilistic reliability model are established by taking the uncertain parameters of the elastic mechanism as random variables, fuzzy variables and interval variables respectively. And the optimization design of the elastic mechanism based on reliability is made. The main research works can be described as follows:1. The planar linkages, screw mechanism and gear driven mechanism, which are used widely in engineering, are taken as analytic objects. The Kineto-Elastodynamics analytic models of the mechanisms are built respectively, and then the Kineto-Elastodynamics analyses are made. The necessity of mechanism analysis based on Kineto-Elastodynamics.is proved by examples. Thereby, the theoretical basis for the further research is offered.2. Based on above, the dynamic reliability models of the mechanism are given by taking the uncertain parameters of the mechanism as random variables, and the dynamic reliability analyses are made. Through examples, the influence of the mechanism's parameters on the reliability of the output kinematic accuracy of the mechanism is investigated, some instructive conclusions are obtained, and those conclusions contribute to improving design quality.3. In accordance with the complexity and time-consuming character of the dynamic analysis of the elastic mechanism, a new dynamic analysis method is presented that is based on BP(Back-propagation) network. By using the approximate functional relationship between the input parameters and the output parameters given by the trained network, the formula of the sensitivity of the network output parameters is derived. The feasibility and validity of the method presented here are verified through examples. Application of the method decreases the time for the dynamic analysis obviously, increases the design efficiency effectively and makes the reliability numerical simulation can be actualized. Furthermore, for the formula of the sensitivity of the dynamic response can be given, so the equivalent treatment of some probability constraints can be actualized, this will accelerate the optimum procedure.4. The fuzzy reliability problem of mechanisms is discussed detailedly. Fuzzy reliability analysis based on fuzzy limit state and fuzzy design rule is made first. Then the fuzzy reliability analysis based on fuzzy strength and stress is studied. Finally, the fuzzy reliability of the elastic mechanism with fuzzy parameters is analyzed by transforming the fuzzy variables into equivalent normal random variables. The relevant examples show that the method is practicable and effective, and the influence of the mechanism's parameters on the reliability of the output kinematic accuracy of the mechanism is investigated, with the similar conclusion as attained from random reliability obtained.5. In according with the difficult of applying the existing probability reliability model under conditions of small sample and poor information in the reliability analysis and design, the interval analysis of the elastic mechanism is made by taking the uncertain parameters as interval variables, applying Taylor series expansion and Monte-Carlo simulation based on BP (Back-propagation) network respectively. Based on above, the non- probabilistic reliability model is established. Finally, through examples, the results comparison of Taylor series expansion and Monte-Carlo show the model is rational and the method is practicable and effective.6. The optimization problem of the uncertain elastic mechanism based on reliability is discussed. The optimization model of the elastic linkage mechanism based on reliability is built by taking the reliability of strength and stiffness of the mechanism as constraints. In the optimum iterative procedure, the gradient and feasible direction algorithms are adopted to calculate. The rationality of the model and the availability of the arithmetic are verified through an example. The optimization model of the elastic linkage mechanism based on non-probabilistic reliability is built by taking the non-probabilistic reliability of strength and stiffness of the mechanism as constraints. The two steps optimization method is presented to calculate. Finally, the model and method given here are inspected by example, with some instructive conclusions obtained.