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.     

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.     

The delta-doped field-effect transistor (δFET)

A field-effect transistor (FET) using a two-dimensional electron gas (2DEG) as an electron channel is fabricated from GaAs grown by molecular-beam epitaxy. The doping profile of the field-effect transistor is described by the Dirac delta (δ) function. The subband structure of δ-doped GaAs is calculated. The characteristics of the δFET are a high concentration of the 2DEG, a high breakdown voltage of the Schottky contact, a narrow distance of the 2DEG from the gate, and a high transconductance. These properties are analyzed. Preliminary results for the extrinsic transconductance and for the transit frequency are obtained from δFET's having nonoptimized structures.     

A Model for the Reliability Estimation of Space Systems

The general problem and need for reliability estimation and prediction is discussed. Various types of reliability estimates are considered. A general probabilistic model is defined in a set-theoretic framework. The model considers the operation of a system over several time-periods where the operating mode-of the system may change from period to period. A general expression is given for the reliability of a system and also upper and lower bounds. Several theoretical examples are shown by using the model and it is shown how particular applications yield different results depending on the physical situation considered. In addition brief mention is made of a particular reliability study, namely a certain phase of the 3-orbit mission of Project Mercury.     

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.     

关于计算机系统的可靠性技术分析

随着互联网时代的到来,计算机成为了人们日常工作生活所不可或缺的实用工具之一,在提高工作效率的同时,也在一定程度上丰富了人们日常生活内容,有效的推动了社会进步。然而,计算机系统在运行时受制于自身系统以及外部运行环境而发生运行异常或故障情形,导致其可靠性降低。文章选取了几种能够提高计算机系统可靠性的技术加以深入分析,以为各种技术的推广使用积累经验。     

Reliability Analysis of Large Nonrepairable Systems

When analyzing reliability of large systems, the great number of states require much computing time and a large memory, neither of which are readily available. This paper describes a method of partitioning a set of possible states into subsets. An algorithm may be devised on the basis of this method requiring much less memory as compared to other well known methods.     

Reliability Analysis of 3-State Systems

This paper describes a reliability analysis of a system where its components take one of three states-good, degraded, or bad. For this 3-state system, the analogy of 2-state system is investigated. The calculation of system reliability can be reduced to that of the reliability of a corresponding 2-state system, provided that it is a generalized S-P system, with or without artificial, degraded components. Consequently, methods for evaluating the exact system reliability and useful bounds on system reliability of 2-state s-coherent system directly apply to 3-state systems. Some basic properties of system reliability with s-independent components are then presented. Further, some reliability bounds on systems with s-associated components are derived. Finally, the method is extended to multi-state systems. This state reduction can be used somewhat in analyzing models where time plays a role.     

A Reliability Growth Projection Model for One-Shot Systems

This paper offers several contributions to the area of discrete reliability growth projection. We present a new, logically derived model for estimating the reliability growth of complex, one-shot systems (i.e., the reliability following implementation of corrective actions to known failure modes). Multiple statistical estimation procedures are utilized to approximate this exact expression. A new estimation method is derived to approximate the vector of failure probabilities associated with a complex, one-shot system. A mathematically-convenient functional form for the s -expected initial reliability of a one-shot system is derived. Monte-Carlo simulation results are presented to highlight model accuracy with respect to resulting estimates of reliability growth. This model is useful to program managers, and reliability practitioners who wish to assess one-shot system reliability growth.     

A Reliability Model for Error Correcting Memory Systems

This paper evaluates the reliability of a memory system incorporating any sort of linear error-correcting code. If the failure hypothesis is too simple (viz, a failure affects the entire memory chip or only one memory bit) an evaluation of reliability can be wrong. The following considerations are thus important: 1. The failure model is based on the internal design of the memory chip. 2. The memory system hardware is accurately accounted for. The resulting model is very close to the hardware implementation and depends on six parameters. The model is very useful for easily comparing memory systems and for deriving tradeoffs among the implementation possibilities for the design of memory systems.     

A Reliability Model for Interconnected Electric Power Systems

An interconnected model is developed, whereby system reliability is studied from both the standpoint of the probability of failure and also the expected value of unserved load. Explicit algorithms (for use on a digital computer) are presented for the calculation of both of these values. Unlike a previous model, this one involves summing over the failure states, thereby allowing the study of each of these aspects of reliability; it also takes into account tie-line limitations. Interconnections could produce a more reliable pair of systems than an expansion would.     

基于蒙特卡罗仿真与逆向FTF的复杂系统可靠性分析

针对复杂系统可靠性评估问题,提出了一种基于FTA(故障树)仿真与FMECA(故障模式影响及危害性分析)相结合的逆向FTF综合分析方法,该方法通过故障树的蒙特卡罗仿真计算系统中的重要部件和系统薄弱环节,再利用FMECA有针对性的对重要部件进行详尽分析,提高了可靠性分析的效率,增强了评估的客观性。并以某无人机为例进行了计算和分析,结果表明:该方法对复杂系统可靠性设计具有一定的指导作用和实用价值。     

Decomposition in Reliability Analysis of Fault-Tolerant Systems

Two important problems which arise in modeling fault-tolerant systems with ultra-high reliability requirements are discussed. 1) Any analytic model of such a system has a large number of states, making the solution computationally intractable. This leads to the need for decomposition techniques. 2) The common assumption of exponential holding times in the states is intolerable while modeling such systems. Approaches to solving this problem are reviewed. A major notion described in the attempt to deal with reliability models with a large number of states is that of behavioral decomposition followed by aggregation. Models of the fault-handling processes are either semi-Markov or simulative in nature, thus removing the usual restrictions of exponential holding times within the coverage model. The aggregate fault-occurrence model is a non-homogeneous Markov chain, thus allowing the times to failure to possess Weibull-like distributions. There are several potential sources of error in this approach to reliability modeling. The decomposition/aggregation process involves the error in estimating the transition parameters. The numerical integration involves discretization and round-off errors. Analysis of these errors and questions of sensitivity of the output (R(t)) to the inputs (failure rates and recovery model parameters) and to the initial system state acquire extreme importance when dealing with ultra-high reliability requirements.     

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.     

复杂系统故障的综合诊断模型

为了提高对复杂系统所产生故障的诊断效率,提出一种基于遗传算法(GA)和人工神经网络(NN)的练合诊断模型.该诊断模型的运行分为两步:1)利用NN对故障诊断数据进行预处理;2)运用GA进行诊断.将嵌套神经网络与遗传算法有机结合,嵌套神经网络的功能相当于一种预处理器,可以减少由遗传算法处理的故障类型的数量.弥补了遗传算法不能诊断出可信度和神经网络难以鉴别出最可能故障点的缺点.提高了诊断结果的精确性、可靠性和一致性,而且在一定程度上减少了总运行时间.     

New Insights Into the BDD-Based Reliability Analysis of Phased-Mission Systems

We present a generalized analysis methodology for binary decision diagram-based fault tree analysis of a wide range of phased-mission systems, with various mission requirements, and structure characteristics. This methodology includes 1) four alternative variable ordering schemes: forward/backward phased dependent operations, and forward/backward concatenation; 2) a strategy to choose an adequate ordering scheme to process a new phased-mission system instance depending on its phase and mission configuration; and 3) efficient generation and evaluation algorithms for generalized phased-mission system binary decision diagrams adopting any arbitrary ordering scheme. The advantages of this methodology are in the low computational complexity, broad applicability, and easy implementation.      

几种典型系统可靠度区间上下确界的计算

对系统可靠性串联、并联和n中取k可靠度区间的最小上界（LUB）和最大上界（GLB）进行了分析，这里假设系统的寿命分布是负指数型，并就系统中不同部件数目下，针对各种情况进行了详细的研究。     

Capacity Consideration in Reliability Analysis of Communication Systems

This paper presents a simple method for deriving a symbolic reliability expression of some practical systems such as a communication system having fixed channel capacities of its links, a power distribution system having limited power ratings of its power lines, a transport system which might not allow traffic more than a particular value, or a chemical system in which oil or gas flow through pipes is permissible only up to some safe limits. A system is good if and only if it is possible to transmit successfully the required capacity from source node to the sink node. This paper defines a group as a set of branches such that success of these branches ensures system success, as defined above. All such groups are obtained from a knowledge of the minimal paths of the system graph. The method is computerized and implemented on DEC-20 computer. Two examples are considered and their solutions presented to illustrate the technique.