基于故障树的数控伺服刀架可靠性分配方法研究

发布时间：2018-03-08 16:36

本文选题：数控伺服刀架　切入点：FMECA　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：数控伺服刀架是数控车床的核心子系统之一,其可靠性直接影响着数控车床的可靠性水平。对数控伺服刀架可靠性进行深入研究,找出其薄弱环节,并在进行优化改进设计时,提供合理的零部件可靠性分配方案,对我国数控伺服刀架的专业化生产及可靠性水平提升具有重要的指导意义。但由于数控伺服刀架故障数据较少且难获取,目前传统的基于数理统计获得的故障数据所进行的可靠性设计,存在成本高,设计周期长等缺点,且数控伺服刀架结构复杂,可靠性指标的分配只能进行到子系统。针对这些问题,本文提出了基于故障树的数控伺服刀架可靠性分配方法,本文的研究工作如下:(1)首先对SFW系列数控伺服刀架进行了结构分析,利用FMECA(Failure Mode,Effects and Criticality Analysis故障模式、影响和危害性)方法,得到了所有可能出现的故障模式、故障原因,并找到了数控伺服刀架的薄弱环节,针对每条故障原因给出了改进措施,为可靠性设计及后续故障树模型的建立提供了依据。(2)利用FTA(Fault Tree Analysis故障树)方法,建立了故障树模型并进行了定性分析;针对故障数据获取周期长,现有数据少等问题,采用了专家评判与模糊集理论相结合的方法对故障树进行定量分析,将专家经验转化为故障树基本事件的模糊故障率,得到了故障树基本事件、两级中间事件及顶事件的故障率,并与现有同类型刀架可靠性水平进行对比分析,验证了该算法的有效性;同时得到了各事件的概率重要度。(3)结合故障树模型,提出了基于故障树的数控伺服刀架可靠性分配方法,以故障率为分配指标将数控伺服刀架系统的总体故障率有层次的分配到零件:首先利用基于概率重要度方法将规定的总体故障率分配到一级中间事件,其次利用可靠性再分配法将一级中间事件的故障率分配到二级中间事件,再利用层次分析法将可靠性发生改变的二级中间事件的故障率分配到基本事件。最终完成数控伺服刀架的可靠性分配,并对比分析了分配结果的合理性。(4)利用MATLAB-GUI(图形用户界面)编制了基于故障树的数控伺服刀架可靠性分配软件。该软件以专家判断语为输入实现了故障树定量分析,包含故障树基本事件、两级中间事件及顶事件故障率的计算、各事件重要度的计算;实现了可靠性分配计算,包含基于概率重要度的顶事件概率分配计算、基于可靠性再分配法的一级中间事件概率分配计算、基于层次分析法的二级中间事件概率分配计算;以及所有计算结果的显示与输出存储;并利用人工计算结果验证了软件计算结果的正确性。该软件具有简单易操作,计算效率高等特点,实现了算法的工程化应用。
[Abstract]:NC servo tool holder is one of the core subsystems of NC lathe, and its reliability directly affects the reliability level of NC lathe. It is of great significance to provide a reasonable reliability distribution scheme for the NC servo tool holder in China. However, the fault data of the NC servo tool holder is less and difficult to obtain. At present, the traditional reliability design based on the fault data obtained from mathematical statistics has the disadvantages of high cost and long design period, and the structure of NC servo tool holder is complex. The distribution of reliability index can only be carried out to subsystems. In order to solve these problems, this paper presents a method of reliability allocation for NC servo tool holder based on fault tree. The research work of this paper is as follows: (1) first of all, the structure of SFW series NC servo tool holder is analyzed. By using the method of FMECA(Failure mode effects and Criticality Analysis fault mode, influence and harmfulness, all possible fault modes and fault causes are obtained. The weak links of NC servo tool holder are found, and the improvement measures are given for each fault reason, which provides a basis for reliability design and the establishment of subsequent fault tree model. The method of using FTA(Fault Tree Analysis fault tree is provided. The fault tree model is established and analyzed qualitatively, and the fault tree is analyzed quantitatively by the combination of expert evaluation and fuzzy set theory, aiming at the problems of long acquisition period of fault data and less existing data. The expert experience is transformed into the fuzzy failure rate of the basic event of the fault tree, and the failure rate of the basic event of the fault tree, the intermediate event and the top event of the fault tree are obtained, and the reliability level of the same type of tool holder is compared and analyzed. The validity of the algorithm is verified, and the probability importance of each event is obtained. In combination with the fault tree model, a fault tree based reliability allocation method for NC servo tool holder is proposed. The overall failure rate of the NC servo tool holder system is assigned to the parts hierarchically with the failure rate as the allocation index. Firstly, the total failure rate is assigned to the first intermediate event based on the probability importance method. Secondly, the failure rate of the first intermediate event is allocated to the secondary intermediate event by using the reliability redistribution method. Then the failure rate of the secondary intermediate event is assigned to the basic event by using the analytic hierarchy process. Finally, the reliability distribution of the NC servo tool holder is completed. The rationality of the distribution results is compared and analyzed. (4) the reliability distribution software of NC servo tool holder based on fault tree is developed by using MATLAB-GUI (graphical user interface). The software realizes the quantitative analysis of fault tree with the input of expert judgment language. It includes the basic events of the fault tree, the calculation of the failure rate of the two level intermediate events and the top events, the calculation of the importance of each event, the calculation of the reliability assignment, including the calculation of the probability distribution of the top events based on the probability importance. The first intermediate event probability allocation calculation based on reliability redistribution method, the second intermediate event probability allocation calculation based on AHP, and the display and output storage of all calculation results; The software is simple and easy to operate, and the efficiency is high, so the engineering application of the algorithm is realized.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG519.1

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