Simplified Markov Model for Reliability Analysis of Phased-Mission System Using States Merging Method

This paper presents a simplified Markov model to evaluate the reliability of phased-mission system (PMS). The time cost and storage requirement are very huge for traditional Markov model to analyze the PMS reliability as the number of components increases to a large scale. The states merging method proposed in this paper can account for the PMS with subsystems consisting of identical components, and similar PMSs are common in real-world systems. The simplified Markov model by states merging has smaller number of system states, compared with the traditional one. Furthermore, for the above subsystems, the size of our model increases only linearly as the number of components increases, while the size of the traditional model exponentially increases. Finally, the effectiveness and correctness of our approach are analyzed by comparing with the traditional Markov method.     

Reliability analysis of electrical system of computer numerical control machine tool based on bayesian networks

The core of computer numerical control (CNC) machine tool is the electrical system which controls and coordinates every part of CNC machine tool to complete processing tasks, so it is of great significance to strengthen the reliability of the electrical system. However, the electrical system is very complex due to many uncertain factors and dynamic stochastic characteristics when failure occurs. Therefore, the traditional fault tree analysis (FTA) method is not applicable. Bayesian network (BN) not only has a unique advantage to analyze nodes with multiply states in reliability analysis for complex systems, but also can solve the state explosion problem properly caused by Markov model when dealing with dynamic fault tree (DFT). In addition, the forward causal reasoning of BN can get the conditional probability distribution of the system under considering the uncertainty; the backward diagnosis reasoning of BN can recognize the weak links in system, so it is valuable for improving the system reliability.     

随机选择修理工且修理延迟的可修系统的可靠性分析

研究了可随机选择修理工且修理延迟的可修系统．假定系统的寿命、延迟修理时间和修理时间均为广义指数分布．通过引进补充变量法并利用广义马尔可夫过程和拉普拉斯变换方法求出了系统的可用度、可靠度、维修频度和系统等待修理的概率等重要可靠性指标．     

共因失效修理工多重休假的两相同部件串联系统的可靠性分析

研究了共因失效修理工多重休假的两相同部件串联系统的可靠性,在假定部件的失效分布服从指数分布,修理工修理时间和休假时间均服从一般连续型分布的条件下,利用补充变量法,得到了该系统的瞬时可用度和稳态可用度、系统的可靠度、系统的瞬时和稳态故障频度等重要可靠性指标。     

Approximate method for reliability assessment of complex phased mission systems

Phased-mission systems (PMSs) have wide applications in engineering practices, such as manmade satellites. Certain critical parts in the system, such as cold standby, hot standby and functional standby, are designed in redundancy architecture to achieve high reliability performance. State-space models such as Markov process have been used extensively in previous studies for reliability evaluation of PMSs with dynamic behaviors. The most popular way to deal with the dynamic behaviors is Markov process, but it is well known that Markov process is limited to exponential distribution. In practice, however, the lifetime of most machinery products can follow non-exponential distributions like the Weibull distribution which cannot be handled by the Markov process. In order to solve this kind of problem, we present a semi-Markov model combined with an approximation algorithm to analyze PMS reliability subjected to non-exponential failures. Furthermore, the accuracy of the approximation algorithm is investigated by comparing to an accurate solution, and a typical PMS (attitude and orbit control system) is analyzed to demonstrate the implementation of the method.     

牵引供电系统可靠性建模方法

采用基于遗传算法的拟合方法,提出了一种以威布尔分布模型为基础的牵引供电系统的可靠性建模方法。以京广线郑州南段牵引供电系统为例,根据统计的14年设备失效率信息,采用建模方法建立了牵引供电系统各设备的可靠性模型,运用BDD算法得到整个牵引供电系统的可靠性模型,计算了系统的有效寿命。拟合优度的K-S和W2检验结果表明:该建模方法是一种适用于牵引供电系统特别是接触网系统可靠性分析的。有效寿命的计算结果表明:牵引供电系统与接触网的有效寿命分别为3.116年与3.215年,供电系统的可靠性在很大程度上取决于接触网的可靠性。     

Reliability Analysis of Excavator Rectifier Feedback System with Multi-State Components Based on Belief Universal Generating Function Method

In view of the complexity and uncertainty of system, both the state performances and state probabilities of multi-state components can be expressed by interval numbers. The belief function theory is used to characterize the uncertainty caused by various factors. A modified Markov model is proposed to obtain the state probabilities of components at any given moment and subsequently the mass function is used to represent the precise belief degree of state probabilities. Based on the primary studies of universal generating function(UGF)method, a belief UGF(BUGF) method is utilized to analyze the reliability and the uncertainty of excavator rectifier feedback system. This paper provides an available method to evaluate the reliability of multi-state systems(MSSs) with interval state performances and state probabilities, and also avoid the interval expansion problem.     

基于KDE及Markov的高速列车传动系振动评价及可靠性分析

为研究高速列车运行过程中传动系的振动情况及可靠性，对CRH3型高速列车传动系关键部件的振动加速度数据进行实车采集，采用核密度估计（KDE）法对采集数据统计处理，得出各关键部件在各方向上振动响应的概率密度函数近似曲线，据此对传动系的关键部件进行振动评价；通过MATLAB计算各关键部件振动加速度的最优置信区间；对传动系及传动系的关键部件定义“安全”和“故障”两种状态，建立关键部件的威布尔比例失效率模型及传动系的Markov状态转移模型，以传动系当前状态为初始状态，基于实时故障率及维修率分析传动系可靠性的变化. 研究结果表明:传动系中轴箱轴承、齿轮箱以及电机轴承的垂向振动最强，振动加速度集中分布在25倍、20倍、10倍重力加速度范围内，概率99.75%的均方差值分别在20.5026倍、17.6712倍、11.4693倍重力加速度内；计算得到各关键部件振动加速度概率为99.75%的最优置信区间，为系统的振动监测阈值优化及故障评估提供参考；故障率及维修率是影响传动系统状态概率的关键因素，当故障率增加30%时，系统的状态概率约下降10%，当维修率由0.05提升至0.10时，可使系统的可靠性提高20%.      

分层结构热备冗余系统的可靠性分析

热备冗余结构在安全苛求系统中应用广泛．智能化输入输出模块和逻辑处理模块的分离形成了分层结构,层内两个模块相互热备,层与层串联后实现系统功能．采用Markov分析方法,考虑模块失效率和维修率,对分层热备冗余系统的可靠性进行了研究．按照优先恢复系统功能的维修策略建立了系统状态转移图,并由此得出了系统可靠性计算方法．依据仿真计算结果,不同模块的失效率和维修率对系统可靠性的影响程度相似,低优先级修复的模块对系统可靠性的影响程度增大．     

基于马尔可夫过程的船舶电力系统可靠性和维修性分析

针对船舶电力系统的可靠性、维修性计算问题,从该系统主要运行方式的基本模型出发,提出了基于马尔可夫过程的船舶电力系统可靠性、维修性分析方法,建立了船舶电力系统可靠性、维修性的数学模型,推导出船舶电力系统可用度与可靠度的表达式,并给出了在船舶电站控制系统中的一个工程应用实例.     

服务台可修的离散时间GI/G/1重试排队系统

讨论了服务器可修的离散时间GI/G/1重试排队系统,其中重试时间服从Bernoulli分布,服务器的寿命为几何分布而修理时间为一般分布.将该系统转化为一个水平相依的拟生灭过程(QBD)并通过矩阵分析方法(MAM)进行分析.通过算法进行逼近,将一个水平相依的Markov链转化为一个有较大边界的与水平不相依的Markov链.最终得到了重试空间中顾客人数的分布,并且通过一些数值算例进一步说明了不同参数对系统的影响.     

Simulation on Reliability Enhancement Testing Technology of Ramming System

Ramming system is the key device to guarantee the firing speed of self-propelled gun. Based on traditional reliability enhancement testing method, a new kind of reliability enhancement testing simulation method of ramming system is put forward firstly. In CAD software Pro/E and dynamic simulation software ADAMS, the virtual prototype of ramming system is established. In EASY5 software, the corresponding hydraulic system and control system models are built. The reliability enhancement testing virtual environment of ramming system is developed using the mechanical-electrical-hydraulic co-simulation technology. Based on the load spectra provided by virtual prototype, and the stress distribution provided by finite element analysis and material's S-N curve(S is fatigue strength, N is fatigue life), a model of fatigue enhancement coefficient is established through the failure mechanism analysis. The simulation processes and simulation results show the feasibility of reliability enhancement testing based on virtual prototype, and provide sufficient theory reference for structure improvement and optimization of ramming system.     

冗余结构容错系统的可靠性区间指标分析

本文针对冗余结构容错系统的可靠性分析中存在的问题，提出了区间分析方法。该方法能定量地反映冗余结构容错系统的可靠性改善情况，是评价冗余结构容错系统的方法之一。     

煤炭码头自动化运输系统容错控制方法

为了解决煤炭码头自动化运输系统对控制的可靠性和安全性要求,提出了一种容错控制方法。运用径向基函数神经网络构造故障诊断器,通过容错故障范例检索,建立了从故障诊断到控制律重构之间的映射关系,实施运输系统的控制律实时重构。应用结果表明:所提出的容错控制方法明显提高了煤炭码头自动化运输系统的技术性能和安全可靠性,系统的各类故障的识别率大于97%,各类故障的误诊率小于1%,系统的有效度由原来的90%提高到98%以上。     

Wind turbine gearbox reliability analysis based on the system level stress-strength model

In order to estimate the reliability of wind turbine gearbox based on the system level, a generalized stress-strength model is introduced. Considering that the system works properly under a variety of random stresses which affect every component, the total stress on the system is given by a known linear combination of the stresses of all components. Then the strength of the system can be viewed as a linear combination of the strengths of relative components. In this model, stress and strength are independent of each other. Reliability of the system is the probability that strength exceeds stress. Finally, the reliability of wind turbine gearbox is estimated by the multivariable reliability calculation method. The corresponding result is compared with the results of reliability in the extreme cases(completely dependent and completely independent) by the traditional evaluation method.     

基于响应面法的连续刚构桥梁体系可靠度分析

为了解决分析桥梁结构可靠度时功能函数不存在显式的问题,在现有响应面法的基础上,提出了改进的响应面法;利用有限元软件,对某高墩大跨连续刚构进行了受力分析;选取压应力、拉应力和稳定性失效3类失效模式,在改进的响应面法基础上,利用编程软件MATLAB,实现连续刚构桥梁体系可靠度的计算.算例分析表明,该方法迭代次数少,效率较高,可实现连续刚构桥功能函数重构和体系可靠度计算.     

基于可靠度的桥梁构件三维地震易损性分析

为了评估桥梁结构近场抗震性能,建立了桥梁构件的三维地震易损性分析流程. 基于工程结构可靠度理论,用构件三维失效曲面表征墩柱、支座构件的损伤状态,将包含多个单一损伤指标的损伤状态方程作为三维地震易损性分析的损伤指标;其次在既有墩柱弯曲和剪切失效曲面研究的基础上,构建了墩柱弯曲和剪切破坏的损伤状态方程;并基于支座地震损伤的相对变形,建立了支座损伤状态的方程. 在此基础上,构建了墩柱和支座三维地震损伤状态的判别准则,并对不同损伤状态进行了量化. 结合各国桥梁抗震设计规范和工程结构可靠度理论,最后实现了三维地震易损性的计算分析. 通过一维地震易损性的简化验证,表明所提方法可用于桥梁结构的地震易损性分析中,并且所得结果与PSDA （probabilistic seismic demand analysis）法的最大概率偏差小于4%.      

基于Markov模型的电解电容可靠性评估

基于Markov（马尔可夫）模型提出了一种对电解电容可靠性评估的方法.文中分析了电解电容的等效电路模型、老化损伤机理,通过RESR（等效串联电阻）表征了电解电容的失效率,然后将电解电容分为正常、老化损伤和完全失效三状态.根据马尔可夫模型建立电解电容的状态转移图,求出其可靠性,以开关电源的BUCK电路为例,通过仿真试验算出了电解电容实时的RESR和失效率,进而完成了对其可靠性的表征.     

Reliability Analysis of Systems with Common Cause Failure Based on Stress-Strength Interference Model

Many mechanical systems have the characteristics of multiple failure modes and complex failure mechanisms. On the basis of stress-strength interference (SSI) model, this paper takes the mechanical system with common cause failure (CCF) as the research object. The relationship between the stress distribution and the strength distribution is studied, and the failures of components are independent of each other under the deterministic stress. Then, the concept of conditional reliability is introduced to build the system reliability models under the action of one-stress and multi-stress for both series and parallel systems. Finally, the corresponding properties of the proposed methods are discussed to show their advantages.     

城市轨道交通牵引变电所继电保护可靠性评估

为了掌握城市轨道交通牵引变电所继电保护可靠性,寻找继电保护系统薄弱环节,为故障排查提供指导,进行城市轨道交通牵引变电所继电保护可靠性评估研究. 首先针对城市轨道交通牵引变电所继电保护系统特点,确定可靠性指标;其次根据系统构成及其故障模式,建立继电保护装置故障树模型以及不同配置方案的保护系统故障树模型;最后考虑微机自检功能,基于马尔科夫理论及蒙特卡洛方法,仿真计算城市轨道交通牵引变电所继电保护可靠性指标. 研究结果表明:方法能够获取丰富的可靠性指标,进行牵引变电所继电保护可靠性评估,从而识别系统薄弱环节;自检率为0.9时,继电保护装置误动故障概率占装置故障概率比例高出拒动故障17.93%,装置误动及拒动自检成功率分别为86.09%与74.37%,保护装置可用度为99.88%;后备保护能够降低保护系统拒动概率,但由其误动造成的保护系统误动占比30%～50%,因此,在选用保护配置时需要考虑保护误动风险影响.