备件保障度评估与备件需求量模型研究

基于更新过程理论,给出了部件寿命服从不同分布(指数分布、威布尔分布、正态分布和Г分布)情况下,单不可修部件的备件保障度模型;然后给出了多不可修部件和多可修部件的备件保障度模型．通过具体算例,验证了模型的正确性;最后在备件保障度模型的基础上,给出了备件需求量模型。     

Operational Availability and Reliability Model

The operational Availability and Reliability (OAR) model is designed to evaluate the availability and reliability of systems with components in any combination of series, parallel, and r-out-of-n:G combinations. In terms of the OAR model, systems are composed of Optimal Replaceable Units (ORUs). Failure, corrective maintenance, and spare acquisition probabilities are calculated via random sampling of the ORU failure, corrective maintenance, and spare acquisition distributions. ORU failures are statistically independent and, to allow for versatility in describing system characteristics, ``3-parameter Weibull' distributed. System availability and reliability are then computed by employing the system failure, corrective maintenance, and spare acquisition data.     

The northeast New Jersey route guidance system (RGS): Case study of a distributed system

The general trend in the computer industry today is moving from centralized toward distributed processing. The same trend is impacting the traffic-control field and is being fueled by the availability of low-priced microprocessors in a general environment of increasing communications costs. The Northeast New Jersey Route Guidance System (RGS), now in the final design phase, serves as an example to illustrate the reasons behind this current trend. One of the major decisions facing the traffic-control system designer concerns the selection of the communications system to be used between a central control base and the remote controllers/processors. Whereas in the past it was possible to separate communications system design decisions from control design decisions, such separation is no longer possible. A portion of the decision is outlined by which a 1972 recommendation for central control, made as part of a surveillance-and-control system feasibility study, was modified to distributed control in 1977, during the preliminary design phase of that project. Five communication alternatives, analyzed for use in the RGS, are described. Two of the five alternatives, requiring the least expensive communication-media leasing costs, entail distributed rather than central control.     

Availability-based life cycle cost model: A simulation approach

Life Cycle Costing (LCC) has become a popular technique for studying operating facility designs prior to their construction. However, many such designs have operating characteristics that are marked by uncertainty. In particular, component failure rates and repair/replacement rates are uncertain. Thus, downtimes and maintenance costs are similarly uncertain. These various costs and uncertainties must be balanced if intelligent cost-based design decisions are to be made. This paper developes a model of Life Cycle Cost which integrates various availability parameters of reliability and maintainability. A simulation algorithm is presented as the appropriate tool for studying life cycle cost of a plant design.     

Cost Effective Spares

This paper presents a method for selecting spare modules to support system availability in a cost-effective manner. We apply the method to determine the sparing requirements for a specialized power unit used throughout a telephone transmission system. The method has been extensively used to generate spares complements for large military systems and to perform reliability tradeoffs.     

Designing risk-management strategies for critical engineeringsystems

Effective management of the tradeoff between productivity and safety is a challenge in many industries that operate critical engineering systems such as nuclear power plants or offshore oil platforms. The objective of this paper is to link risk-management strategies to a system's safety and productivity over its lifetime. These strategies involve decisions that affect the physical system both directly and indirectly though the performance of the personnel that design, construct, or operate it. The problem is thus to link the different components of such risk-management strategies to human and system performance. In this paper, we present the basis of a decision support framework for the design and assessment of different risk-management strategies in risk-critical systems. First we discuss the inherent difficulty in balancing productivity and safety in the short and the long term and the different components of a risk-management strategy. We present a model involving both production failures and catastrophic failures as a function of strategic alternatives. This model is based on a probabilistic and dynamic risk analysis of a system, linking different aspects of risk-management strategies to specific characteristics of the physical system. We show how this model, coupled with explicit value judgments, can be used to design optimal strategies, e.g., to balance initial costs, long-term operations and maintenance costs, and the potential costs of catastrophic failures. To illustrate the concepts we use the case of the maintenance of a corporate airplane     

Comparison of Monte Carlo Techniques for Obtaining System-Reliability Confidence Limits

Digital computer techniques are developed using a) asymptotic distributions of maximum likelihood estimators, and b) a Monte Carlo technique, to obtain approximate system reliability s-confidence limits from component test data. 2-Parameter Weibull, gamma, and logistic distributions are used to model the component failures. The components can be arranged in any system configuration: series, parallel, bridge, etc., as long as one can write the equation for system reliability in terms of component reliability. Hypothetical networks of 3, 5, and 25 components are analyzed as examples. Univariate and bivariate asymptotic techniques are compared with a double Monte Carlo method. The bivariate asymptotic technique is shown to be fast and accurate. It can guide decisions during the research and development cycle prior to complete system testing and can be used to supplement system failure data.     

An overview of collection, analysis, and application of reliabilitydata in the process industries

Issues relevant to the collection, analysis, and application of reliability data are discussed. In terms of analysis, attention is given to: current common practice and its limitations; the need for feedback-to-data collection process; lack of high-quality software for reliability analysis; contribution of exploratory analysis techniques; problems of small data sets and of over interpretations: and critical need for sensitivity analysis in reliability studies. In terms of applications, attention is given to the alternative purposes for which such reliability data can be used: safety, cost, legislation, and system availability evaluation; maintenance and replacement decisions; logistic support and spares provisioning; initial design and quality changes; and procedural and monitoring changes     

Availability of a series system with warm spares

We discuss two models for the availability of a series system of components with warm spares, serviced by a single service facility. Replacement of failed components by a spare has pre-emptive priority over repair of the failed components; for the restart model, in which interrupted repairs restart from the beginning, we find the availability of the system; for the resume model, in which interrupted repairs resume from where they left off, we show how to obtain the availability of the system. Some numerical examples and the distributions of system downtime are given for both models.     

Mesh-Restorable Networks with Enhanced Dual-Failure Restorability Properties

We consider extensions of the most common mesh-restorable network capacity design formulation that enhance the dual-failure restorability of the designs. A significant finding is that while design for complete dual-failure restorability can require up to triple the spare capacity, dual failure restorability can be provided for a fairly large set of priority paths with little or no more spare capacity than required for single-failure restorability. As a reference case we first study the capacity needs under complete dual-failure restorability. This shows extremely high spare capacity penalties. A second design model allows a user to specify a total capacity (or budget) limit and obtain the highest average dual-failure restorability possible for that investment limit. This formulation, and a relationship between dual-failure restorability and availability, can be used to trace-out the capacity-versus-availability trade-off curve for a mesh network. A third design strategy supports multiple-restorability service class definitions ranging from best-efforts-only to an assurance of complete single and dual-failure restorability on a per-demand basis. This lets a network operator tailor the investment in protection capacity to provide ultra-high availability on a service-selective basis, while avoiding the very high investment that would be required to support complete dual-failure restorability of the network as a whole.     

US Army Reliability Initiatives?In Concert with Air Force R&M 2000

This paper describes how the US Army is improving readiness through enhanced reliability, availability, and maintainability (RAM). The Army is serious about supplying its personnel with the kind of equipment that stays on line. The US Army Materiel Command is taking aggressive steps to ensure that systems achieve their RAM requirements. Too often the Army has been accused of settling for minimum performance. As is well known, industry is reactive; it responds to pressure to improve what the customer thinks is important. An important step to getting higher levels of reliability and maintainability is to stand together with the Air Force and Navy customers and demand that RAM design and manufacturing disciplines are carried out and contractual RAM requirements are achieved. The achievement of requirements must be accomplished during system development and fielding. Improved RAM results in improved productivity, user satisfaction, and lower operating and support (O&S) costs. Linking R&M initiatives with O&S cost is an important step in justifying the up-front design and manufacturing disciplines that improve field performance. Meeting RAM requirements is the beginning and not the end of Army reliability efforts. Continued efforts to improve RAM are the thrust. For each system, the Army strives for continued improvement. Increased reliability reduces O&S costs while improving fielded mission accomplishment. Contractors will continue their efforts to improve production quality and to eliminate systemic causes of field failures.     

System Operational Readiness and Equipment Dependability

The concept of operational readiness of repairable systems is defined in terms of finite queueing theory as the probability that a multidevice, multimodal system will meet specified operational requirements at any given time. The primary determinants are shown to be design parameters and use parameters. Design parameters, which include reliability and maintainability (as measured by MTBF and MTR), can be lumped into a single non-dimensional design parameter, the ``dependability ratio.' Relationship of this design parameter to single-device availability is first shown. Next, the more general cases are developed: Readiness of exactly N devices, assuming Q ? N repairmen (multiple or compound availability). Readiness of at least N - k devices, assuming Q ? N repairmen (operational readiness). Single-device availability is shown to be a special case of operational readiness in which full-time availability of a repairman is implicitly assumed. By the use of an example, certain possibilities for tradeoffs among men, machines, and operational requirements are examined, along with implications for design costs vs. procurement costs vs. personnel costs, using the nondimensional dependability ratio as a system variable. For repairable systems, the tradeoff possibilities between reliability and maintainability are indicated. Limitations of the work to date are noted, and directions for further work are indicated. An appendix contains a derivation of singledevice availability for Weibull-distributed time to failure and repair.     

以LRU的RMS参数表达的战备完好率模型

首次导出了备件在定期补充方式下的备件供应体制为两站制和三站制的备件延误时间模型,由此可用现场更换模块（LRU）的可靠性、维修性、备件保障性（RMS）参数来表达可靠性串联结构的系统战备完好率模型,从而可以对任务成功率、能执行任务率和使用可用度进行具体的工程设计。     

A Wear Model for Assessing the Reliability of Cylinder Liners in Marine Diesel Engines

Stringent in-service and operating requirements oblige marine diesel engines to possess high levels of reliability and availability. To achieve the desired reliability and availability levels, it is necessary to carry out costly maintenance activity on the cylinder liners, the wear on which is a major factor in causing diesel engine failure. This paper presents a s-based methodology that can be used to carry out a condition-based estimate of liner reliability with respect to failure through excessive wear, and to plan condition-based maintenance activity. The wear process is described through an ad hoc cumulative damage model, and the reliability of the liners is estimated on the basis of wear measures, and predictions of wear increase. The approach proposed allows reducing maintenance costs without noticeably affecting liner reliability. In fact, it gives the probability of inspecting or replacing liners only when there is a high likelihood that their wear level will exceed the wear limit before the next inspection date. The proposed model, and planning procedure have been applied to a data set consisting of wear measures of the cylinder liners of two SULZER RTA 58 engines equipping twin ships of the Grimaldi Group     

Dynamic multistage software estimation

This paper develops dynamic models that advance the state-of-the-art in software estimation to meet the analytic requirements of the most current spiral and prototyping software development process paradigms. These models account for the dynamics of changing requirements, system design, and other policy factors. The dynamic formulation permits analysis of the effect of current-stage decisions on future decision opportunities in light of multiple objectives associated with cost overrun and schedule delay. A linear-normal dynamic model with closed-form solution is developed first and provides the context for defining the components of the software cost-estimation dynamic model and for describing the interaction of these components. A second model relaxes the linearity and normal distribution restrictions, employing nonlinear state and observation equations derived from the Intermediate COCOMO and COCOMO II models     

A framework for reliability-aware design exploration on MPSoC based systems

Applying system-level fault-tolerant techniques such as active redundancy is a promising way to enhance the system reliability for safety-related applications. Embedded system design using active redundancy is a challenging task that involves solving two major problems, namely finding the optimal redundancy configuration and mapping/scheduling of the application (including the redundant components) to the platform under timing and reliability constraints. This paper presents a framework for automatic synthesis of fault-tolerant designs on multiprocessor platforms. The core of the framework consists of: (1) a reliability analysis, that computes the system-level reliability in the presence spatial and temporal redundancy, and (2) an optimization approach for reliability-aware design space exploration. The proposed approach considers both transient and permanent faults and is among the first to support system design using imperfect fault detectors. The framework takes an application model, a platform model and a set of application requirements as input, and generates the recommended design parameters, including task-to-processor binding, task schedule and the selection/placement of redundancy. The effectiveness of our approach is illustrated using several case studies.     

Reliability analysis of real-time fault-tolerant task models

One notable advantage of Model-Driven Architecture (MDA) method is that software developers could do sufficient analysis and tests on software models in the design phase, which helps construct high confidence on the expected software behaviors and performance, especially for safety-critical real-time software. Most existing literature of reliability analysis ignores the effects from those deadline requirements of tasks which are critical properties for real-time software and thus cannot be ignored. Considering the contradictory relationship between the deadline requirements and time costs of fault tolerance in real-time tasks, in this paper, we present a novel reliability model, which takes schedulability as one of the major factors affecting the reliability, to analyze reliability of the task execution model in real-time software design phase. The tasks in this reliability model has no restrictions on their distributions and thus could be distributed on a multiprocessor or on a distributed system. Furthermore, the tasks also define arrival rates of faults and fault-tolerant mechanisms to model the occurrences of non-permanent faults and the corresponding time costs of fault handling. By analyzing the probability of tasks still being schedulable in the worst-case execution scenario with faults occurring, reliability and schedulability are combined into an unified analysis framework, and two algorithms for reliability analysis are given. To make this reliability model more pragmatic, we also present an estimation technique for estimating the fault arrival rate of each task. We show through two case studies respectively the detailed derivation process under static-priority scheduling in a multiprocessor system and in the design process of avionics software, and then analyze the factors affecting the reliability analysis by setting up simulation experiments. When no assumptions of fault occurrences made on the task model, this reliability model regresses to a generic schedulability model.     

相控阵雷达分布式温湿度调控系统可靠性设计

雷达长期在复杂的温湿度环境中工作,容易造成其内部的电子元器件失效而影响整个雷达的稳定运行。 针对这种状况,根据某相控阵雷达分布式温湿度调控系统的可靠性设计需求,运用可靠性理论分别对该系统在硬件和软件方面的 可靠性进行设计。其中,硬件可靠性设计主要包括滤波技术、隔离技术、屏蔽技术、接地技术等;软件可靠性主要包括恢复 技术与低功耗模式、时间冗余技术、集成电路通信、RS485 通信、FATFS文件系统等。对系统进行相关试验验证,结果表 明:系统在给定的试验环境中能够正常稳定地运转,其温度和湿度的重复性、迟滞性结果均满足相应的标准,所采集和反馈的数据与试验环境数据相符,能够满足可靠性设计要求。     

Implantable cardioverter defibrillators

The electrical design challenges for implantable defibrillators are discussed based on the following criteria: device evolution, system architecture, therapy delivery, mid heart activity sensing circuits. The discussion includes the incidence of sudden cardiac death and the clinical requirements of device hardware. System architecture includes the three dependent entities that define the system mid the functional components of the implanted device     

Routing Connections With Differentiated Reliability Requirements in WDM Mesh Networks

Reliability has been well recognized as an important design objective in the design of modern high-speed networks. While traditional approaches offer either 100% protection in the presence of single link failure or no protection at all, connections in real networks may have multiple reliability requirements. The concept of differentiated reliability (DiR) has been introduced in the literature to provide multiple reliability requirements in protection schemes that provision spare resources.