Modeling repairable systems with failure rates that depend on ageand maintenance

A general repairable system model that includes age and preventive maintenance (PM) dependent failure rates is proposed. This model introduces the concept of system availability as a random variable, leading to availability measures for individual realizations, rather than for the average over many trials. Thus this model generalizes the classical definition, and serves as a performance index for system design. A design scheme suggested to maximize the probability of achieving a specified stochastic cycle availability with respect to the duration of the operating interval between PMs. Numerical computations of the results for Weibull-like distributions illustrate the design criteria. Asymptotic behavior of the performance with no PM has been studied. Extension to other distributions is straightforward     

联机检修的冗余结构使用可用度模型修正

现场故障更换对象由电子和机电元器件改变为电子和机电更换模块后,备件保障就成为联机检修冗余结构任务可靠度和使用可用度模型中必须包含的一个关键参数。但在传统的联机检修任务可靠度和现行的使用可用度模型中没有得到或没有完全得到应有的反映。对此,提出了修正模型。在使用可用度模型中还对同时检修的平均修复时间模型作出了改正。     

基于综合环境加速寿命试验的 电子装备故障预测研究

 对某型雷达天控系统的20kHz信号板进行均匀正交试验,利用试验数据对试验结果进行了深层次的分析,总结出温湿度条件下电子装备性能衰退的一般规律;针对在故障预测中占有重要地位的电子装备可靠性预测问题,提出了一种基于综合环境加速寿命试验的电子装备可靠性预测新方法,该方法将性能退化理论拓展为加速性能退化理论,将该理论与传统可靠性预测方法相结合,有效地解决了加速寿命试验中无失效数据的处理问题,最后通过具体的算例验证了该方法的有效性.     

Performance prediction methodology based on pattern recognition

Performance prediction is crucial to increasing drill availability and reliability as well as facilitating further proactive maintenance. This paper presents a novel method for pattern recognition based performance prediction. The features of vibration signals are extracted by wavelet packet transform after de-noising, and then band energy based feature measures are identified by ant colony clustering analysis to form an input vector for the performance assessment model. Prediction of performance degradation trend of drill is carried out using feature mapping based on the established performance assessment model. Experimental results have shown that the proposed method can analyze drill degradation quantitatively, and predict problems before they occur. Furthermore, ant colony clustering algorithm is improved to adjust comparison probability dynamically and detect outliers. Compared with other ant colony clustering algorithms, the algorithm has higher convergence speed to meet requirements of real-time analysis as well as further improvement of accuracy. Finally, effectiveness and feasibility of the proposed method are verified using vibration signals acquired from a drill test bed.     

The reliability parameter and its importance for life cycle management

Increasing importance is being attached to the concept of Life Cycle Management, in military circles at least. The essential element in this concept is to take account of the total cost of ownership and operation of an equipment, or system - the initial capital cost, and the subsequent costs of operation and maintenance over the operational “life” of the equipment. The reliability parameter enters into both classes of cost, but not in any simple way. It interacts with a number of other factors - the complexity of the equipments, the planned availability, the response time for maintenance, the geographic distribution of the equipment, the length of the operational life, the end item cost, and the average cost of a repair action - to mention a few. In this paper we will discuss the nature of the interactions and give some parametric calculations to show the order of magnitude of the effects.     

Health-monitoring method of note PC for cooling performance degradation and load assessment

Health monitoring technologies, which can evaluate the performance degradation, load history and degree of fatigue, have the potential to improve the effective maintenance, the reliability design method and the availability in the improper use conditions of electronic equipment. In this paper, we propose a method to assess the cooling performance degradation and load history of printed circuit boards in electronic equipment by use of a hierarchical Bayes model based on Computer Aided Engineering (CAE) results of thermal-stress simulation and experiment data from observed measurements. We applied this method to note PC that can monitor the device load factor and revolution number of cooling fan. It is shown that this method can estimate the temperature and deformation distribution of the printed circuit board from monitoring variables through latent variables such as thermal dissipation of the device and thermal boundary condition by use of the hierarchical Bayes model. And it is confirmed that the statistical load assessment concerning thermal cyclic load and the maximum load distribution can be conducted using the estimated temperature and deformation data. Furthermore, we verified that the cooling performance degradation can be assessed, if the temperature difference per unit thermal value between two suitable points on the printed circuit board can be obtained. It is concluded that the proposed method can be effective to assess the thermal load history and cooling performance degradation.     

Real-time performance reliability prediction

The purpose of this paper is to describe an approach to real-time reliability prediction, applicable to an individual product unit, operating under dynamic conditions. The concept of conditional reliability estimation is extended to real-time applications using time-series analysis techniques to bridge the gap between physical measurement and reliability prediction. The model is based on empirical measurements, self-generating, and applicable to online applications. This approach has been demonstrated to the prototype level. Physical performance is measured and forecast across time to estimate reliability. Time-series analysis is adapted to forecast performance. Exponential smoothing with a linear level and trend adaptation is applied. This procedure is computationally recursive and provides short-term, real-time performance forecasts which are linked directly to conditional reliability estimates. Failure clues must be present in the physical signals, and failure must be defined in terms of physical measures to accomplish this linkage. On-line, real-time applications of performance reliability prediction are useful in operation control as well as predictive maintenance     

基于信息熵的电子装备软故障预报

针对电子设备的故障识别提出了一种基于性能退化数据的缓变故障预报方法,以不同层次的可观测功能模块为基本的故障预测和定位单位,利用信息熵的概念建立性能检测数据波动趋势的信息模型,对模块进行功能故障预测。试验表明：熵可以比较准确地指明功能电路的软故障与器件老化,对以替换现场可更换单元为主要手段的电子装备原位维修与应急维修有重要的现实意义。     

Computation availability of crossbar systems in a non-uniform traffic environment

Multiprocessor systems can provide higher performance, reliability, and availability than single processor systems. In order to properly assess the effectiveness of multiprocessor systems, measures that combine performance and reliability are needed. Most previous studies have considered the performance and reliability/availability separately. Only a limited number of studies have been carried out by considering the performance and reliability together in the presence of a uniform traffic in the network. Hot spots in a multiprocessor system result in a non uniform traffic in the network and results in a degradation in the performance of the network. The aim of this paper is to study the combined performance and reliability of a crossbar system in the presence of a hot spot in the system. Computation availability is taken as the criteria for measuring the combined performance and reliability. Markov chain models have been developed to compute the above measurement criteria.     

基于一维漂移布朗运动的SLD退化失效建模

超辐射发光二极管(SLD)集LD大输出功率和LED宽光谱优点于一体,是光纤陀螺仪中的关键元件与薄弱环节,其可靠性在很大程度上决定了光纤陀螺仪的可靠性。针对SLD寿命长、失效数据难于获取的特点,研究了基于性能退化数据的可靠性评估方法。在对SLD进行失效机理分析的基础上,提出用一维漂移布朗运动模型对产品在环境应力作用下的退化特性进行建模,基于所得模型,由SLD的性能退化信息估计模型中的参数进而评估得到SLD的可靠性指标。这克服了传统可靠性分析方法依赖寿命数据的缺点,能够在没有寿命数据的情况下评估得到SLD的可靠性指标,从而可节约大量的试验经费和试验时间,在工程应用上具有重要的价值。     

An approximation analysis for the availability of a parallel redundant system with general distributions

This paper presents an approximation method for deriving the availability of a parallel redundant system with general distributions. The system discussed is composed of two identical units. A single service facility is available for the performance of preventive maintenance(PM) and repair. The failure times, repair times and PM times are assumed to be arbitrarily distributed. The presented method formulates the problem of the availability analysis of a parallel redundant system as a semi-Markov process which represents the state transitions of one specified unit in the system. This method derives the availability easily and accurately. Further, when all the distributions are exponential, the availability obtained by this method is exact.     

联机检修结构可靠性模型在雷达设计中的应用

联机检修可靠性模型能够充分地发挥冗余结构的潜力,大幅度地提高冗余结构的任务可靠性。为了验证联机检修模型在工程中的应用,结合某军航雷达的设计,对该模型进行了详细的论证;通过在该军航雷达中采用联机检修模型而大大提高了整机的任务可靠性,实现了总体单位的研制任务书要求,对其他型号地面雷达的可靠性设计起到一定的指导作用。     

Reliability assessment of the metallized film capacitors from degradation data

Metallized film pulse capacitors are the key component of an inertial confinement fusion (ICF) facility. The reliability of the capacitors has a significant impact on the operational reliability and maintenance expenses of the entire system. For high-reliability capacitors that do not normally fail in a reasonable length of time, it is difficult to assess reliability by using the traditional time-to-failure analysis method. Analyzing the degradation mechanisms of the metallized film capacitors, this paper presents a life distribution model whose parameters can be estimated from the degradation measures of the capacitors, and which has proven to be very accurate and economical in test costs.     

雷达故障自动修复设计

雷达作为一个大规模的电子产品,在使用过程中出现部分设备性能下降或故障的可能性很大,本文分析了传统的故障修复方法,并以可靠的状态采集处理和充分的冗余设计为基础,利用监控计算机控制系统的自动修复,减少了操作人员的检修时间,提高雷达在使用过程中的可用度,降低了使用维修成本,保证了雷达作战性能的发挥。在无人值守和少人值守的雷达设计上具有十分重要的意义。     

On-line reliability estimation of individual components, usingdegradation signals

This paper provides a unique approach that allows 'determination of a component's reliability as it degrades with time' by monitoring its degradation measures. The concepts have been implemented using: finite-duration impulse response multi-layer perceptron neural networks for modeling degradation measures, and self-organizing maps for modeling degradation variation. The specific application considered is in-process monitoring of the condition of the drill-bit in a drilling process, using the torque and thrust signals. An approach to compute prediction limits for any feedforward neural network, critical for on-line performance reliability monitoring of systems using neural networks, is introduced by combining the network with a self-organizing map. Experimental results show that neural networks are effective in: modeling the degradation characteristics of the monitored drill-bits, and predicting conditional and unconditional performance reliabilities as they degrade with time or usage. In contrast to traditional approaches, this approach to on-line performance reliability monitoring opens new avenues for better understanding and monitoring systems that exhibit failures through degradation. Essentially, implementation of this 'performance reliability monitoring' reduces overall operations costs by facilitating optimal component-replacement and maintenance strategies     

A new R&M measure and its estimation

The reliability and maintainability measure is referred to as MTUT. It is the mean time to restore an equipment and its maintenance system to its original working status; it is expressed as a proportion of the mean time to failure for any given equipment. This measure integrates maintenance and repair time expenditures of all types from three levels of maintenance. Other measures discussed in the literature such as availability, mean time to repair, and average queue length are compared to MTUT. A testing program for the demonstration phase of equipment development is presented. Estimation and discrimination procedures are derived for MTUT using data from the outlined testing program. Large-sample theory is used to construct both interval estimates and discrimination procedures for the MTUT, using data acquired from the assessment phase of equipment development     

Traffic monitoring and analysis for the optimization of a 3G network

Recent years have recorded a surge of research activities on IP traffic monitoring, enabled by the availability of monitoring hardware and large-scale storage at accessible costs. More recently, passive monitoring has been applied to operational 3G networks. The passive observation of network traffic, coupled with advanced traffic-analysis methods, can be a powerful and cost-effective means to infer the network status and localize points of performance degradation without requiring complete access to all network elements. Furthermore, the availability of high-quality traces can be exploited to predict the load of the network under hypothetical conditions, variations of the actual network configuration at the capturing time. Both approaches can be useful for some engineering and reoptimization tasks that are commonly encountered in the lifetime of an operational 3G network. In abstract terms, the availability of high-quality traces can greatly empower the measurement-based optimization cycle, with human experts in the loop, thus driving an already operational 3G network toward improved performances. In this article we discuss the contribution that traffic monitoring and analysis (TMA) can provide to the optimization of an operational 3G network     

Weapons systems analysis,part I: System effectiveness

Often, a weapon system may be approved based on a particular required military capability without due consideration given to other missions which it might or might not be able to perform. This paper puts forward a methodology for the analysis of weapons systems, and examines various criteria and attributes that relate to system effectiveness. Criteria and attributes included are system performance, operational readiness, life cycle costing, design to cost, reliability, availability, maintainability, producibility, operability, capability, adequacy and logistics.     

Stochastic behaviour of a two-unit cold standby redundant electronic equipment under human failure

This paper presents a mathematical model to evaluate availability and M.T.T.F. of a two-unit cold standby system with three possible states of each unit; viz. good, partially failed and failed, incorporating the concept of human failure. The model has been developed for exponential failures and general repairs. Single service facility is available in each state during the operational stage of the electronic equipment. Laplace transforms of the various state probabilities have been obtained. Steady-state probabilities, steady-state availability and mean time to failure have been derived.     

连续工作型电子装备战备完好率预计算法

运用可靠性和维修性的累积时间预计法，得出了装备的可靠性、维修性预计信息，基于装备的产品树结构，从战备完好的定义出发，给出了连续工作型电子装备战备完好率的算法，并对此进行了缜密的推导。