Reliability Optimization of a Series-Parallel System

A mathematical model is formulated for optimizing the reliability of a system subject to given linear constraints; the system has several stages in series; each stage has parallel redundancy to improve the reliability. Part I shows a new way to transform the model of constrained optimization to a saddle point problem by using Lagrange multipliers. Conditions are derived for maximizing the reliability function; Newton's method is used to solve the resulting multidimensional nonlinear algebraic equations. Further modifications are provided to avoid inverting the large Jacobian matrices; therefore this method is practical for large systems. Part II shows how to transform the model of constrained optimization to a multistage decision process and uses the Maximum principle to arrive at the optimal decision. This approach is easy to apply, formulate, and program. The solution can be obtained without fear of nonconvergence (very often experienced with earlier methods) besides providing considerable saving in computer time. Design alternatives can be easily considered.     

Optimal Reliability Design of a System: A New Look

The reliability literature offers an abundance of methods for the optimal design of systems under some constraints. In most of the papers, the problem considered is: given reliabilities of each constituent component and their constraint-type data, optimize the system reliability. This amounts to the assignment of optimal redundancies to each stage of the system, with each component reliability specified. This is a partial optimization of the system reliability. At the design stage, a designer has many options, e.g., component reliability improvement and use of redundancy. A true optimal system design explores these alternatives explicitly. Our paper demonstrates the feasibility of arriving at an optimal system design using the latter concept. For simplicity, only a cost constraint is used, however, the approach is more general and can be extended to any number of constraints. A particular cost-reliability curve is used to illustrate the approach.     

Optimal Design for System Reliability and Maintainability

A complex system consisting of N modules that are logically interconnected for mission success is to be placed in the field for a fixed period of time. For some modules, standby units can be provided, for others this option is not available, but we must select from among several design alternatives differing in cost, weight, and reliability. The problem is to determine simultaneously the module designs and the numbers of standby units to maximize the system reliability, subject to cost and/or weight constraints. Other authors have considered a similar problem for a pure series inter-connection of modules, but we permit the system to be any configuration of modules in series and/or parallel. A dynamic programming model is presented for this problem. The notion of the generalized decomposition operator is used to develop a set of recursive relations. An example is included.     

Optimal Reliability of a Complex System

In a complex system where the redundant units cannot be reduced to a purely parallel or series configuration, the reliability is obtained by using Bayes' theorem. A mathematical model is formulated for the reliability of a system with nonlinear constraints. The system reliability is optimized based on the model and the solution is obtained by using the sequential unconstrained minimization technique (SUMT). This method is an efficient method for solving this type of problem. Two life support systems, one is the communication system of a two-man space capsule and another is a high-pressure oxygen supply system in a space capsule, have been identified to have the complex system configuration treated in this work.     

Identifying Optimal Components in a Reliability System

The first step in a reliability optimization process is to make a reliability assessment for each component in the system. If this assessment is made in a qualitative way, by grouping together components with the same reliability, and establishing a prevalence order among groups, is there a way to decide which components have the greatest Birnbaum measure without computing the exact value of this measure? In this paper, three relations between components are introduced and studied, and it is proved that they are useful for selecting the components that have the biggest effect on the system reliability in the sense of Birnbaum. An algorithm that uses the results in the paper to select these important components is also provided.     

Optimal System Reliability Parameters with Minimum Costs

This paper gives a procedure for a repairable complex system which will determine the failure and repair rates as well as the number of redundant components to achieve minimum total s-expected cost for a given availability. The total s-expected cost is the s-expected investment and operating costs. The capital investment cost function is related to the steady-state availability of each component and the operating cost function to the steady-state probability of the system's being in a particular state.     

Optimal Redundancy Allocation for Non Series-Parallel Networks

This paper presents general algorithms for solving redundancy optimization problem for non series-parallel networks. Using closed form expressions for star-delta and delta-star conversions, the exact system reliability expression (objective function) is written down in a straightforward manner. The Box method has been employed to get the optimal continuous solution. The integer solution is obtained by a modified Box method and Branch and bound technique. The scheme is illustrated with an example. The parametric method is used throughout     

Optimal Reliability Design of Process Systems

The optimal design of system reliability which takes into account the quantitative aspect of systems throughput or capacity is proposed. It is based on the concept of an r-out-of-n configuration instead of the conventional parallel 1-out-of-n configuration and is especially suitable for treating problems which arise in process systems. The problem is solved by the pseudo-Boolean programming method of Lawler and Bell.     

Optimal Allocation of Effort to Improve System Reliability

The optimal allocation of development effort to improve reliability for systems of general, but fixed, structure is discussed from a deterministic standpoint and also when there is uncertainty in component reliabilities at various stages of development. A computational algorithm is given for implementing the optimal allocation, called the optimal policy, and the form of the solution is related to the special case of a series system when development effort functions are the same for all components. This methodology is a useful aid to decision-making about reliability improvements.     

Review of Optimal Reliability Design, Fundamentals and Applications

This reference covers the extent of the state-of-the-art in optimizing systems reliability. The book consists of fifteen chapters and an appendix. The main part of the book is organized by problem type and solution method. Some of the topics covered include: redundancy allocation methods using heuristics, dynamic programming solutions and discrete optimization methods; reliability optimization using nonlinear programming and meta-heuristic algorithms; and methods to solve reliability-redundancy optimization. The book may serve as a textbook for students or as a reference for researchers and practitioners. It is a comprehensive book that is recommended for anyone concerned with designing reliable systems.     

Generalized Optimal Trajectory Control for Closed Loop Control of Series-Parallel Resonant Converter

The series parallel resonant converter (SPRC) is known to have combined the merits of the series resonant converter (SRC) and the parallel resonant converter (PRC). However, the series PRC (SPRC) has a three-element LCC structure with complex transient dynamics and without control of the resonant circuit's dynamics, the converter's closed loop bandwidth to switching frequency ratio will be much reduced compared to that of pulsewidth modulation converters. In this paper, the generalized optimal trajectory control (GOTC) for the SPRC is presented. It allows the nonlinear resonant circuit of the SPRC having an arbitrary starting state to reach a desired steady state in one cycle with two optimally controlled switching instances. It is a generalized form of optimal trajectory control (OTC) which is restricted to transitions between steady states. Based on GOTC, a traditional controller with inner current and outer voltage state-feedback is designed for an SPRC based dc–dc converter. The GOTC based feedback controller allows use of higher feedback gains compared with one using OTC or frequency control and gives higher closed loop bandwidth. This results in either better disturbance rejection for the converter or the possibility of reducing output filter sizing. Experimental results confirm the theoretical claims.     

A Note on Heuristic Methods in Optimal System Reliability

Many optimization techniques have been used to solve redundancy allocation problems, most of which result in noninteger solutions. A few, including dynamic programming and integer programming, as well as a host of heuristic methods give integer solutions. This note critically reviews six promising heuristic approaches. The advantages and disadvantages of each of the approaches are discussed. An extended approach is presented which incorporates some of the ideas of the previous methods for solving a general non series-parallel system. The extended approach appears to be quite efficient and is general. The simplicity and efficiency of the approach will lend itself to solving large practical problems.     

半桥串并联谐振变换器的分析与设计

详细介绍了串并联谐振变换器(LCC型)在f_s>f_r下的工作原理,根据等效电路给出了稳态分析及最佳设计原则。最后以100kHz半桥ZVS-SPRC实验电路为例,给出了简单设计步骤、实验结果及相关波形。     

Reliability Assessment Of Computer System Design

This paper is intended to introduce a general purpose software and hardware design reliability assessment methodology based on the analysis of failure occurrence trend previous to modeling of failure processes. The failure data is collected at test phases and during the system operating life time. The maintenance requirement is used to qualify the Tropico R switching system, according to both hardware components and design failures.     

Electronic System Thermal Design for Reliability

Thermal design and analysis are important in Reliability/Availability/Maintainability R/A/M programs for electronic systems. A thermal design approach emphasizing the coupling of heat transfer theory and experiment to basic reliability considerations is illustrated here by discussing typical thermal problems on several system integration levels for a high reliability, multi-cabinet hybrid computer system. This paper emphasizes a particular attitude toward the thermal aspects of equipment design, one that is flexible in the methods of analysis, comprehensive in its treatment of each integration level in a complementary fashion, and oriented toward the goals of the R/A/M program as a whole. The examples show that conventional analytic solutions, when coupled with reliability theory and a modicum of experimental results, lead to effective thermal design.     

基于Web技术的监控系统及其可靠性设计

本文从适应internet/Intranet发展需要出发,较为详细地介绍了基于Web及网络一体化技术的监控系统的设计与实施方法,实现了工厂真正的“企业综合自动化“,同时对网络中Infranet控制层的硬件、软件及其可靠性设计作了分析介绍.     

半导体激光器可靠性评估系统设计

介绍了一种基于单片机控制的可预置工作电流值、工作温度值的半导体激光器可靠性评估系统的软、硬件设计方法.该方法以89C51单片机为核心部件,通过闭环反馈控制系统对工作电流、工作温度进行比较、调整,提高系统精度.该可靠性评估系统可实时显示工作电流及工作温度值.     

软件可靠性衡量体系设计

提出了一套软件可靠性衡量体系,重点研究了衡量体系中的软件可靠性建模和软件可靠性评估方法。研究了适用于软件测试阶段的Musa模型以及模型的使用前提条件、模型表示、数据要求和参数估计;同时针对软件可靠性评估的主观性和受多因素影响的特点,提出采用模糊综合评判法进行评估,给出了评估步骤和方法;最后通过实例说明如何进行可靠性建模和评估。     

公共广播系统主机的可靠性设计

公共广播系统的可靠性设计包括广播系统主机的可靠性、电源的可靠性、功放的可靠性、传输线路的可靠性等.通过实例描述了公共广播系统主机的可靠性设计.     

Time-Dependent Error-Detection Rate Model for Software Reliability and Other Performance Measures

This paper presents a stochastic model for the software failure phenomenon based on a nonhomogeneous Poisson process (NHPP). The failure process is analyzed to develop a suitable meanvalue function for the NHPP; expressions are given for several performance measures. Actual software failure data are analyzed and compared with a previous analysis.