Reliability Prediction Techniques for Complex Systems

As electronic systems continue to evolve into more and more complex structures, the search for better and more efficient reliability prediction techniques naturally takes on added momentum. Needed are not only systematic methods of mathematical model building that will simplify the procedures involved but also noncomplex ways of obtaining solutions to many practical problems. This paper illustrates the applicability of transition diagram in describing the state space of a complex system, repairable or nonrepairable, and shows the methodology of writing the set of first-order linear differential equations representing the system performance by inspection of the transition diagram. A discussion of some applicable properties of linear signal-flow graphs is included. Methods of solving problems by inspection techniques are clearly explained and specific examples are given to illustrate the concepts. The mean time Tm for a system to pass for the first time from its initial state to a failed state is usually a statistic of prime interest. Certain properties of Laplace transform are used to illustrate how Tm of a general complex system, repairable or nonrepairable, can be obtained by solving a set of simultaneous algebraic equations. Flow graph techniques of solution by inspection are shown to be a valuable tool in obtaining analytical solutions for Tm of many practical systems.     

Reliability Prediction for Continuously Operating Systems

The paper considers the prediction of reliability for a complex system designed for continuous operation. The state of the system is defined by identifying the subsystems which are functioning, the remainder undergoing repair (no inactive standby). The system is described as up whenever it is in one of an arbitrarily selected set of the system states. It is assumed that maintenance facilities are always adequate, and that the system conforms to a few other very mild restrictions. An exponential failure law is not assumed. Formulas are developed giving the mean durations of system up-times and down-times in terms of the corresponding quantities for the subsystems. The sensitivities of the formulas to errors in the input data are considered.     

高复杂度综合系统的可靠性预计

针对装备可靠性工作的焦点问题,在各个设备的可靠性要求的框架下,依据国家军用标准及美军标手册MIL-HDBK-217<电子设备可靠性预计手册>的应力分析法,采用比较实用、高效的ITEM ToolKit可靠性平台对某高复杂度仪器设备进行可靠性预计,在任务实施中探索一种比较实用、...     

复杂系统进行快速的可靠性预计和设计

重视可靠性设计,开发与应用快速、实用的预计和设计软件,是落实可靠性工程的必要条件。对已经开发成功的、可以快速地进行复杂系统可靠性预计和设计的软件进行了示例介绍。     

武器装备的全寿命周期可靠性预计

阐述了周全地考虑武器装备寿命周期可靠性的必要性，给出了全寿命周期可靠性预计方法和模型。以某机载武器为例，预计其全寿命周期可靠性，并分析、改进了原设计方案，使其满足规定的可靠性指标。     

A Cut Set Method for Reliability Evaluation of Systems Having s-Dependent Components

The cut set method presently assumes components to be s-independent. This paper presents a method called MCS approach for extending the cut set approach to systems involving s-dependencies. The method is based on MCS theorem and consists in decomposing the system by cut sets and using the Markov processes for calculating terms in the cut set equations. The Markov process associated with only the members of one cut set need be considered at a time and the transition rate matrix of the entire system need not be generated. The MCS approach is feasible when Pr{C?i} and F(S) can be calculated from the transition rate matrix of the members of Ci. This is possible when the MCS theorem applies and the MP of the entire system can be merged to obtain the MP of Ci. However, in many situations where the MCS theorem does not rigorously apply, approximate results may still be possible by the MCS method. The judgment in such cases is based on how approximately does the MCS theorem apply.     

高入纤功率光纤通信系统的可靠性研究

掺铒光纤放大器(EDFA)和拉曼放大器(FRA)的使用,使得光纤通信系统中的入纤功率有了很大的提高.较高的入纤功率不仅会在光纤中引起各种非线性效应,对光脉冲的传输产生影响,也会对光纤本身的可靠性产生影响,为此介绍了高入纤功率对光纤系统的影响,分析了其产生的机理,并提出了应对措施.     

A Bayesian Reliability Assessment of Complex Systems for Binomial Sampling

This paper presents a reliability assessment procedure that systematically combines complete system binomial test data with lower level binomial test data obtained from either partial system or component tests. The procedure uses beta prior distributions of all reliabilities, Bayes theorem, and probability moments. The result is a posterior distribution of system reliability that can be used to determine Bayes point and interval estimates. The beta prior distributions evolve from data on predecessor systems similar to the system in question and engineering knowledge about what the various test-alternatives measure.     

Reliability of a System Having Quasi-Redundancy

Reliability mathematical models of a certain type of system with a branching configuration, possessing quasi-redundant properties, are developed for the nonrepair environment. A simple system of this type is chosen as a vehicle to illustrate the method of approach when in a repair environment. To solve the simultaneous differential equations for such a system in a repair environment, analog computer simulation is found to be very suitable.     

Iterative Method for Steady State Reliability Analysis of Complex Markov Systems

An iterative procedure for evaluating steady-state probabilities of complex Markov systems is proposed; it is based upon a generalization of Seidel's method for solving systems of linear algebraic equations. The probabilities are evaluated with desired accuracy by sequentially solving equation sets of much lower order than this of the entire system. For the systems with states transmitting only to states of higher and (or) lower probability magnitude orders, simple, easily composable recurrent formulas for state probabilities are obtained. An illustrative example is included.     

A New Real-Time Reliability Prediction Method for Dynamic Systems Based on On-Line Fault Prediction

While a specific system is in use, its reliability will decrease gradually after the infant mortality period because of the components' degradation, or external attacks. Thus, reliability is a natural characteristic of a system's health, and can be used for condition monitoring & predictive maintenance. This paper introduces a new real-time reliability prediction method for dynamic systems which incorporates an on-line fault prediction algorithm. The factors that may reduce a system's reliability are modeled as an additive fault input to the system, and the fault is assumed to be varying linearly with time, approximately. The time-varying fault is roughly estimated based on a modified particle filtering algorithm at first. Then, as a time series, the fault estimate sequence is smoothed, and predicted by an exponential smoothing method. Mathematical analysis shows that the effects of the system, and measurement noises on the fault estimates are greatly reduced by exponential smoothing, which indicates that the comparatively high accuracy of the fault estimates & predictions is guaranteed. Based on the particle filtering & fault prediction results, the whole system's predictive reliability is computed through a Monte Carlo simulation strategy. The effectiveness of the proposed real-time reliability prediction method is validated by a computer simulation of a three-vessel water tank system.     

Reliability Analysis on the δ-Shock Model of Complex Systems

We investigate the delta-shock model of complex systems consisting of n i.i.d. components. We first obtain a general lifetime distribution for the delta-shock model of a general complex system by reducing the system to a linear combination of parallel systems. We then consider coherent system structures including series, parallel, and k-out-of-n, then derive some useful results including reliability bounds, bounds on the mean lifetime, limiting distributions, and Laplace-Stieltes transforms     

Quadrilateral-Star Transformation: An Aid for Reliability Evaluation of Large Complex Systems

Although delta and star transformations are usually adequate for reliability evaluation, they can fail for some complex networks. Under these conditions the quadrilateral-star transformation introduced in this paper can be used with success. The quadrilateral-star transformation is not exact; however, it yields results having adequate accuracy.     

The Reliability of Repairable Complex Systems Part B: The Dissimilar Machine Case

A generalization of the reliability model given in Part A of this reliability study is made. The failure and repair rates are assumed to be exponential as in Part A, but the model equations are changed so that the following ramifications are possible. 1) The label case: it is necessary to know which of the similar machines are broken down in order to decide if a system failure has occurred. 2) The parameter case: the values of the failure and repair rates are not the same on each machine. 3) The type of failure case: the system goes from state i to i + j after a failure, j ? 1, and to i - k after a repair, k ? 1, whereas in Part A j = k = 1 only. A procedure for finding dissimilar machine model equations with time delays before failure and time restoration constraints after repair are given.     

可靠性预计方法及思考

本文介绍了可靠性预计的目的,并对当前较为常见的可靠性预计模型或方法做了比较和说明,也对造成可靠性预计局限性的原因做了分析,最后对在可靠性工程工作中对待可靠性预计的态度做了探讨.     

基于Bellcore标准的电子产品可靠性预计方法及案例研究

介绍了Bellcore标准进行可靠性预计的理论基础,包括元器件失效率与单元失效率模型等。利用Bellcore现行的TelcordiaSR-332标准手册,对某用于商用环境中的单板计算机进行了可靠性预计。给出了该单板计算机MTBF预计的过程和方法,以及失效率和MTBF的预计结果,并与军用标准的预计结果进行了对比,说明了Bellcore标准目前存在的一些问题。     

Optimization of Systems Reliability

The purpose of this paper is to obtain an optimum redundancy of the parallel system by a variational technique. The objective function is to maximize the system profit. A simple computational procedure is obtained for the optimum design of the multistage parallel systems by this method. Two numerical examples are given in detail.     

全面而正确地认识可靠性预计

<电子产品可靠性与环境试验>2001年第5期刊登了韩庆田等同志的<可靠性预计及其发展趋向>一文,读后对文中的部分观点有不同看法,今借本期刊一角,浅谈个人的观点,供大家参考.