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数控机床可用性耦合建模及影响度分析

Coupling Modeling and Influence Analysis for Availability of Numerical Control Machine Tools

【作者】 魏领会

【导师】 申桂香;

【作者基本信息】 吉林大学 , 工业工程, 2011, 博士

【摘要】 数控机床是机械制造业的关键设备,其产量和技术水平在某种程度上代表着一个国家的制造业水平和竞争力。数控技术的发展,关系到国家工业战略地位和综合国力水平。近年来中国数控机床市场需求不断增加,面对中国市场的旺盛需求,外资企业纷纷抢滩中国市场,增加在华的投资力度,由于我国技术水平和工业基础还比较落后,数控机床的性能、可用性水平等与工业发达国家相比,还有不小的差距。残酷的竞争,对中国数控机床市场造成很大的冲击,使国内机床市场的发展面临巨大压力和严峻挑战。在压力和挑战面前,唯有快速提高数控机床产品的质量和可用性,才能使国产数控机床产业立于不败之地。因此,提高数控机床产品的质量和可用性,成为目前大多数国内机床制造企业亟待解决的问题。可用性是从用户角度看到的产品质量,是产品竞争力的核心。要想提高数控机床的可用性水平,基础技术研究是前提和保障。本文依托国家自然基金课题“基于全寿命周期的数控机床可用性影响度耦合模型及分析技术”,以国产数控机床为研究对象,进行数控机床“可用性耦合建模及影响度”理论的探索性研究,为促使数控机床趋向“要用时就能用”的可用性工作状态开辟新途径、新方法。可用性的研究以大量的现场数据为基础,只有拥有真实、可靠的数据才能进行完善的可用性耦合建模及影响度分析。结合课题,通过与数控机床用户的机床操作者、维修人员、设备管理部门,机床制造厂的售后服务人员协同,共同制定了本次可用性试验方案,采用课题研究中开发的可用性数据采集和信息交互技术平台,收集到大量数控车床现场故障信息。可用性耦合建模及影响度分析,必须结合试验数据首先摸清可用性耦合的两个方面—可靠性与维修性状况,才能更好的挖掘可靠性、维修性对可用性影响的内在联系和耦合规律。数控机床可用性耦合因素分析,探寻可靠性与维修性状况,建立整机及子系统可靠性模型、整机及子系统维修性模型。在进行整机可靠性建模时,基于所取得的截尾数据,进行不完整数据的可靠性估计、模型初选和参数估计。参数估计采用图解法与相关系数相结合,以图解法的结果作为相关系数法迭代的初始值,综合图解法简单但估计精度低、相关系数法精度高但迭代运算复杂,且初值影响运算结果的特点,最后通过k-s检验法确定考核数控车床的故障时间分布模型,包括故障时间分布函数F(t)、故障时间概率密度函数f(t);整机维修性建模,通过修复时间数据的模型判断,极大似然法参数估计、假设检验,确立维修度函数M(t)、维修概率密度函数m(t)和修复率函数μ(t)。子系统可靠性建模,结合实验室多年的研究经验,对数控车床子系统进行重新划分,同时为提高建模的精度,首次采用适用于小样本的灰色GM(1,1)模型。最后通过对子系统修复时间分布类型的假设、参数估计和拟合检验,确定各个子系统的维修性模型。可用性耦合因素分析,为快速识别出整机中的关键子系统、进一步可用性耦合建模和影响度分析奠定基础。数控机床可用性耦合建模,首先分析数控机床结构和动态运行特点,构建耦合关系框架与基于随机Petri网理论的数控车床可用性动态运行过程模型,随机Petri网动态运行模型结合蒙特卡洛仿真,进行数控车床可用性耦合的数值分析。子系统耦合建模以转塔刀架为例综合故障率和修复率的变化,主要分析可用性与不可用性的变化规律。耦合过程分析以可用性为核心,将可靠性和维修性耦合在可用性的求解过程之中。分析结果为制定机床可用性提升措施和维修决策提供依据,制定可用性提升措施与最佳维修周期,对减少维修损失和停机费用,提高数控机床的使用效率具有实际意义。可用性影响度分析,就是要研究和评估各子系统在所期望的时间区间内对整机可用性影响的大小,衡量各子系统对整机可用性的权重序列,识别至关重要的少数关键子系统和可用性薄弱环节。首先,结合可用性耦合建模,对数控机床的生命周期作了划分,并对机床不同生命时期的运行特征及故障机理进行分析,根据可用性影响因素和耦合建模的结果,对受试数控车床可用性影响采用早期故障期和偶然故障期的分段研究。随后,分析可用性特征的层次结构,采用可拓方法的优度评价原理,确定可用性的指标权重和多指标模型,客观地反映出数控机床运行中可用性特征元素的真实情况;从定性和定量两个方面分析受试数控机床早期故障期和偶然故障期子系统对整机的影响程度,得出不同故障时期影响数控机床可用性至关重要的子系统,为该系列数控机床的可用性改进指明了方向。最后,通过早期故障期与偶然故障期影响度分析结果的对比,针对至关重要的少数子系统和可用性薄弱环节,提出了早期故障试验、早期故障排除、关键子系统的故障纠正和可用性增长等可用性影响度的具体改进措施,为促进数控机床新产品可用性提高提供了依据。针对课题研究内容在异地厂校之间搭建信息采集的互动平台,进行基于网络化的数控装备可用性数据采集和信息交互技术的研究。首先提出可用性数据采集和信息交互的体系结构框架,可用性数据采集和信息交互体系由数控装备研究所、机床用户、数控机床制造企业三方的功能模块构成,在对网络技术与数据库等关键技术和实现模式研究的基础上,开发了通用于数控车床、加工中心等数控装备的可用性数据采集和信息交互技术平台,该平台包括数控车床、数控铣床、加工中心等机床类型的信息录入;装备中心的信息查询、数据导出、数据分析、发布处理结果、查看发布信息;用户知识库、机床信息培训课程、虚拟实验室、故障案例库等内容。可用性信息采集及信息交互技术平台的开发,使数控机床可用性信息采集更加高效;使可用性分析更方便、快捷;使机床制造企业、数控装备研究所和机床用户之间实现了可用性信息资源的共享;使不同机床企业的可用性资源得以充分发挥更大作用。

【Abstract】 Numerical control(NC) machine tool is the key equipment on the mechanical manufacturing industry, and its yield and technology level stands for manufacturing level and competitiveness of a country in some extent. The development of NC machine tools technology is related to national industrial strategic status and the comprehensive national strength level. The market demand of NC machine tool increases continuously in china in recent years. Facing the strong demand of Chinese market, foreign-capital enterprise are subordinate to the Chinese market for expanding market in China in succession, and begin to increase investment. Even so, there is still a certain gap compared with developed countries on the performance and availability level of NC machine tool because of the lag of China’s technical level and industrial base. Brutal competition imposes very great impact on NC machine tool market of China, and makes enormous pressure and severe challenge on domestic market. In the face of pressure and challenge, the only way to make homemade NC machine tool industry invincible is to improve the quality and availability of NC machine tool. Therefore, the most critical problem of the domestic NC machine tool manufacturer that should be solved at present is to improve the quality and availability of NC machine tool.Availability is the product quality from view of the user, and the core of products competitiveness. To improve the availability level of NC machine tool, basic technology research is prerequisite and guarantee. This article relies on the National Natural Science Foundation of China "The coupling model of availability influence and analysis techniques for NC machine tools based on life cycle ", studies on China-made NC machine tool to research on the theory of " the coupling modeling and influence of availability ", and opens up new ways and new methods for availability work state to promote NC machine tool tend to be "to use when you can use ".The research of availability bases on a large number of field data, and only has true and reliable data that can analyze coupling modeling and influence for availability perfectly. Combining with the subject, the availability experiment program was made through the coordination among operators of NC machine tool consumer, maintenance personnel, equipment management department, and manufacturer service personnel. In this program, large number fault information from the field of NC lathe was gathered using the data collection and information exchange technologies platform developed in this subject. In order to dig the reliability and maintainability which impact on the internal relations and coupling rules of availability better, the analysis of coupling and influence combining with field data should find out two aspects of availability-the status of reliability and maintenance.According to analyze the coupling and influencing factors of availability and seek the status of reliability and maintenance, the reliability and maintenance model for whole machine and subsystem were established. When whole machine reliability model was making based on censored data obtained, the reliability estimation, model primary and parameter estimation from the incomplete data were conducted. The method combing with Graphical method and correlation coefficient, using the result of graphical method as initial value of the correlation coefficient iteration was brought in the parameter estimation. This method also integrate the point that graphical method simply but low precision, the correlation coefficient iteration precise but iterating complexity, and the initial value of whole machine influencing on the result. The fault time distribution model of NC lathe selected for check was made according to the method of k-s inspection, which includes the fault time distribution function F (t), fault time probability density function /(t). According to judge the model of repair time date for whole machine modeling, using the method of maximum likelihood method parameter estimation and hypothesis testing, the functions were established such as maintenance function M (t), maintenance probability density function m (t) and the repair rate functionμ(t). When conducting subsystem reliability modeling, the subsystem was reclassified combining with laboratory research experience of many years, and the gray small sample GM (1,1) model was referred in order to improve accuracy first time at the same time. Finally, each maintenance model of subsystem was established according to the assumptions of subsystem repair time distribution type, parameter estimation and fitting inspection. The coupling analysis of availability settles the foundation for identifying the key subsystem quickly, analyzing the coupling and influence of availability further.When making the availability coupling of NC machine tool, the characteristics of structure and dynamics running of NC lathe should be analyzed firstly, and the coupling relations framework and dynamic running process model that was based on stochastic Petri net theory was built. The dynamic model of stochastic Petri net combined with Monte Carlo simulation for numerical analysis on NC lathe availability was used. The coupling model of subsystem which put turret cutter as an example synthesized with the change of fault rate and repair rate, and mainly analyzed the change rule of availability and non availability. The analysis of coupled process made the availability as the core, and put the reliability and maintainability coupled to solving process. The result of analysis provided the basis for making the improvement measures and maintenance decisions. It is practical significance for the loss of reduced maintenance, downtime costs and improving the use efficiency for NC machine tool since developing improvement measures and best maintenance period for availability.The analysis of availability influence is to study and evaluate each subsystems that influence the size of the whole machine in the desired interval time, measure proportion sequence of each subsystem that effects the whole system, identify a few key sub-systems and weak links. First of all, this article divided the life cycle of NC machine tools into part combining with the coupling modeling results of the availability, and analyzed the character that runs in different life time and fault mechanism. The segmentation research method was adopted in the period of early fault and occasional fault to study the availability influence of NC machine tool selected according to the analysis result of influence factors and coupling process. Then, the hierarchy structure of availability features was analyzed, using the method of the goodness evaluation principles of extension to determine the index weight and multi-index model,and this reflected the real situation of characteristic elements exist in running of NC machine tools objectively. The influence degree which early fault and occasional fault of subsystem impacted on whole system was analyzed qualitatively and quantitatively, after that, the critical subsystems that effected on availability during different fault time was obtained. All these point out the direction of improvement for this series of NC machine tool. Finally, specific improvement measures of availability influence such as early fault tested, early fault eliminated, and critical subsystems fault corrected and availability growth was proposed after compared the analyzed result of influence between the early faults and occasional faults and aimed at a small number of critical subsystems and availability weak links. All these provided the basis for improvement availability of new products.The interactive platform that combined with task research content was built between the school and factory from different place for information collection, and was used for research on data collection and information exchange technology for NC equipments base on network. Architecture framework was first putted forward on data collection and information exchange of availability. This system was consisted of three function module as follows:the institute of NC equipment, NC machine tool users, and NC machine tool manufacturers. Based on key technology and implementation pattern such as database and network, the data collection and information exchange technology platform was developed that can be used commonly for NC lathes, machining centers, etc. This platform include:information recorded for some type of NC machine tool like NC lathes, NC milling machines and machining centers; equipment center like information query, data export, data analysis, results published, information viewed; the content of user knowledge base, machine information and training courses, virtual labs, fault case database and so on. The development of availability information collection and information exchange technology platform makes NC machine tool availability information collection more efficient, make availability analysis more convenient and shortcut, make different machine manufacturers, research institutes and users share resources information of availability, and make resources of availability play a greater role fully in different NC machine tool companies.

  • 【网络出版投稿人】 吉林大学
  • 【网络出版年期】2012年 01期
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