转向机构的时变可靠性分析与综合

发布时间：2018-01-01 04:10

本文关键词：转向机构的时变可靠性分析与综合　出处：《西华大学》2012年硕士论文　论文类型：学位论文

【摘要】：在不确定性下研究机构时变运动可靠性问题是近年来机构学研究的热点课题之一。由于机构受几何尺寸、运动副间隙、工作原理及使用环境的影响，其运动输出往往具有不确定性，从而可能引起机构运动精度可靠度下降、机构动作不可靠等问题。就机构运动精度可靠性而言，目前大多方法属于点可靠度分析方法，点可靠度只是提供了某一瞬时时间点上机构运动输出满足期望运动输出或实现预定功能的可能性。显然，从整个运动区间来考察机构的可靠性往往比点可靠性更加合理、更加符合实际。因此，在不确定性条件下研究机构的时变（区间）运动可靠性及其优化设计（综合）问题，具有极为重要的理论意义和实际价值。本文以整体式转向机构和齿轮齿条式转向机构为研究对象，在分析转向机构时变运动可靠性和优化综合的同时，对时变运动可靠性方法进行了详细的论述。本文主要研究工作可以概括如下： 1在对目前汽车中广泛使用的整体式转向机构和齿轮齿条式转向机构进行运动分析的基础上，综合考虑构件尺寸的不确定性（随机性）和机构自身结构误差，建立了转向机构误差概率模型。 2引入结构可靠性分析方法中上穿越率和下穿越率概念，并结合一次二阶矩法（FOSM）和首次穿越的Poisson近似方法推导出机构时变（区间）运动可靠度解析表达式。以此为基础建立了整体式转向机构和齿轮齿条式转向机构的时变运动可靠性模型。并通过相关算例将其与点可靠性进行比较分析，结果表明机构时变可靠度总是小于等于点可靠度，满足点可靠度并不意味着满足时变可靠度。显然，机构时变运动可靠性比传统的点可靠性更加合理，它以整个运动区间为考察对象，能够体现机构在整个运动过程中满足预期功能的可能性。 3针对机构优化设计（综合）问题，提出了机构时变运动可靠性优化综合方法。建立了整体式转向机构时变运动可靠性优化模型，通过数值实例将其与该机构的确定性优化方法及点可靠性优化方法进行比较分析。结果表明，机构时变运动可靠性优化方法比确定性优化方法和点可靠性优化方法更加优越，不仅可以在满足可靠性要求的同时减小机构的结构误差，而且其求得的优化解往往也比其余两种优化方法稳定。
[Abstract]:In recent years, the study of time-varying motion reliability of mechanism is one of the hot topics in mechanism research, because the mechanism is affected by geometric size, clearance of motion pair, working principle and operating environment. The motion output of the mechanism is often uncertain, which may cause the reliability of the mechanism motion accuracy to decline and the mechanism action to be unreliable, etc. In terms of the mechanism motion accuracy reliability. At present, most of the methods belong to the point reliability analysis method. The point reliability only provides the possibility of the mechanism motion output meeting the expected motion output or realizing the predetermined function at a certain instantaneous point in time. The reliability of the mechanism from the whole range of motion is usually more reasonable than that of the point. In this paper, the time-varying (interval) motion reliability and optimal design (synthesis) of the mechanism are studied under uncertain conditions. This paper takes the integral steering mechanism and the gear-rack steering mechanism as the research object, while analyzing the time-varying motion reliability and optimization synthesis of the steering mechanism. The method of time-varying motion reliability is discussed in detail. The main research work of this paper can be summarized as follows: On the basis of the kinematic analysis of the whole steering mechanism and the gear rack steering mechanism which are widely used in the automobile at present, the uncertainty of the component size (randomness) and the structure error of the mechanism are considered synthetically. The error probability model of steering mechanism is established. (2) the concepts of upper and lower traversing rate are introduced in the structural reliability analysis method. The time-varying (interval) of the mechanism is derived by combining the first-order second moment method and the Poisson approximation method of the first crossing. On this basis, the time-varying motion reliability models of integral steering mechanism and gear rack steering mechanism are established and compared with point reliability through relevant examples. The results show that the time-varying reliability of the mechanism is always less than or equal to the point reliability, and meeting the point reliability does not mean the time-varying reliability. Obviously, the time-varying motion reliability of the mechanism is more reasonable than the traditional point reliability. It takes the whole motion range as the object of investigation and can reflect the possibility of the mechanism meeting the expected function in the whole motion process. (3) aiming at the problem of mechanism optimization design (synthesis), this paper presents an optimal synthesis method for the time-varying motion reliability of the mechanism, and establishes an optimization model of the time-varying motion reliability of the integrated steering mechanism. A numerical example is given to compare it with the deterministic optimization method and the point reliability optimization method of the mechanism. The time-varying motion reliability optimization method is superior to the deterministic optimization method and the point reliability optimization method. It can not only meet the reliability requirements but also reduce the structural error of the mechanism. Moreover, the optimal solution obtained is more stable than the other two optimization methods.
【学位授予单位】：西华大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH112

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