Earticle

A new algorithm combined Eagle Strategy with PSO is proposed. The new algorithm performs by two phases: First Eagle Strategy is used to do global search; Second PSO algorithm is used to do fast local search around a promising solution. The balance of global search and local search is considered simultaneously. It is not only help to jump out of local optimum but also accelerate local convergence. Experimental results on three benchmark problems illustrate that the presented approach is effective, efficient and accurate for solving reliability redundancy optimization problems.

This article is based on the mixture of tabu search algorithm and interior search algorithm(ISA) to address the reliability redundancy assignment problem. Iinterior search algorithm is immersed in a tabu search algorithm. TS is used to search solution space and ISA is applied to generate neighborhood solutions. The merit of two algorithms is considered at the same time. And a mixed TS-ISA method is proposed to deal with three benchmark reliability redundancy optimization problem. The experimental results show that a the method is effective and efficient for RRAP by comparing with other results in the previous literaturs.

This paper deals with the problem of redundancy allocation for the mixed reliability system in an optimal way. Two kinds of the reliability system are considered for optimal allocation of parallel redundancy. The problem is approached as the optimization problems using th standard method of dynamic programming(DP). The algorithm for solving the optimal redundancy allocation is proposed and then the DP algorithm is applied to two numerical examples such as maximization of reliability subject to an allowable cost-constraint and minimization of the total cost subject to the specified minimum reliability-constraint. A consequence of this study is that the developed computer program package can be applied to the optimal redundancy allocation for the mixed reliability system.

The reliability of system is to become a important concern in developed industry. The controller based on the reliability is so important position. A reliable system is for system protection and human life by fault detection and control action against the transient condition of system. The aerospace system , nuclear reactor and chemical reactor are representative of a reliable system. This paper presents analysis of reliable system reliability, formal problem statement of optimal redundancy based on the reliability for a reliable system. And the problem is optimized by genetic algorithm. The genetic algorithms is useful algorithm in case of...

신뢰도란 임의의 시스템이 주어진 환경 하에서 의도하는 기간 동안 의도한 목적의 기능을 정상적으로 발휘할 확률로 정의되며, 실제 산업현장에서 제품설계 시 중요한 척도로 고려되고 있다. 혼합 중복전략을 고려하는 신뢰도-중복 최적화 문제는 비용, 무게 등의 제약 내에서 시스템의 신뢰도를 최대화하는 대안부품, 중복설계 부품수, 그리고, 중복전략을 동시에 선택하는 문제이다. 기존 연구들은 Cold-standby 중복 k-out-of-n 서브시스템의 정확한 신뢰도 평가가 난해함에 따라 근사 신뢰도 모형을 적용하고 있다. 따라서 본 연구에서는 Cold-standby 중복이 적용되고, 고장감지기를 Imperfect S/W로 고려한 k-out-of-n 서브시스템의 정확한 신뢰도를 평가할 수 있는 연속시간 마코프체인(CTMC) 모형을 제안하였다. 또한, 수치실험을 통해 기존 연구의 근사 신뢰도 모형 사용에 유의하여야 함을 보였으며, CTMC 신뢰도 모형을 기반으로 RROP의 Benchmark 문제의 최적해를 제시하였다.

The reliability is defined as a probability that a system will operate properly for a specified period of time under the design operating conditions without failure and it has been considered as one of the major design parameters in the field of industries. Reliability-Redundancy Optimization Problem(RROP) with choice of redundancy strategies involves selection of components with multiple choices, redundancy levels and strategies(active and cold standby) for maximizing system reliability with constraints such as cost, weight, etc. In existing studies, the approximated reliability stochastic model was used because it is hard to obtain the exact reliability for k-out-of-n subsystem designed by cold standby. Therefore, this paper suggests the Continuous Time Markov Chain(CTMC) model in order to calculate the exact reliability of k-out-of-n subsystem applied cold standby with imperfect switching. The error of approximate reliability stochastic model of existing studies is analyzed by numerical experiment and the result show that it should be carefully used. Also, the optimal solutions of benchmark problem for RROP is provided based on CTMC model is suggested in this study.

신뢰도란 임의의 시스템이 주어진 환경에서 의도하는 기간 동안 의도한 목적의 기능을 정상적으로 발휘할 확률로 정의되며, 산업현장에서 제품의 고장, 수명과 관련된 품질을 대표하는 척도로서 제품 설계의 주요 요인으로 고려되고 있다. 또한, 기업의 사회적 책임 및 소비자 중심주의의 대두로 생산자는 소비자가 원하는 품질과 신뢰도를 충족해 주어야 하며, 이는 기업의 경쟁력과 직결되는 중대한 요소가 되었다. 일반적인 신뢰도-중복 최적화 문제에서는 서브시스템을 구성하는 부품들의 중복전략을 활성중복 또는 대기중복 중 단일 중복전략을 고려하고 있으나, 본 연구에서는 서브시스템별 최적 중복전략을 고려하였다. 즉, 본 연구의 혼합 중복전략을 고려하는 신뢰도-중복 최적화 문제는 비용, 무게 등의 제약 하에서 시스템의 신뢰도를 최대화하기 위한 최적의 대안부품, 중복설계 부품수, 중복전략(활성/ 대기중복)의 조합을 선택하는 문제이다. 기존 연구들에서는 대기중복 서브시스템에 대하여 근사 신뢰도 모형을 적용하고 있다. 본 연구에서는 Imperfect S/W를 갖는 대기중복 서브시스템의 정확한 신뢰도를 평가할 수 있는 연속시간 마코프체인(CTMC) 모형을 제안하였다. 또한, 기존의 근사 신뢰도 모형과 CTMC 모형을 기반으로 직렬-병렬 시스템의 신뢰도-중복 최적화 문제의 최적해를 도출하고, 이를 비교하였다.

The reliability is defined as a probability that a system will operate properly for a specified period of time under the design operating conditions without failure. It has been considered as one of the major design parameters in the field of industries because it is a standard representing the quality level related to fault and life-time of products. Furthermore, by raising company's social responsibility and consumerism, the producer must satisfy the consumer's demand for quality and reliability of products, and this satisfaction is the very core for competitiveness of the company. While in the general studies of the Reliability-Redundancy Optimization Problem(RROP), the redundancy strategy considered for the parts that form the subsystem was chosen from either the active redundancy or the standby redundancy. However, an optimal redundancy strategy that incorporates both were considered for each subsystem in this study. RROP with mixed redundancy strategies(active and cold standby) involves selection of components with multiple choices, redundancy levels and strategies for maximizing system reliability with constraints such as cost, weight, etc. In existing studies, the approximated reliability model for cold standby subsystem was used because it is hard to obtain the exact reliability. Therefore, this paper suggests the Continuous Time Markov Chain(CTMC) model in order to calculate the exact reliability of cold standby subsystem with imperfect switching, and compares the system reliability evaluated by model of existing studies and CTMC model.

MTBF(Mean Time Between Failure)와 MTBSF(Mean Time Between Service Failure) are two representative quantitative reliability requirements for railway systems. There are the case that both of the two requirements are presented and the case that only one of them is presented in the specification of railway systems. we deal with the redundancy allocation problem to meet the two reliability requirements. The redundancy increases MTBSF while it decreases MTBF. Parallel redundancy and the exponential lifetime distribution of components are considered for the series systems. Mathematical model and example are presented for the redundancy optimization problem of minimizing the cost subjecting to MTBF and MTBSF requirements.

In this paper, we supposed allocating the number of redundancies as the model of 0-1 knapsack problem and formulated the problem to maximize the systems reliability for a mission length. The formulated problem reduced the problem size using the modified branch and bound algorithm by Lagrangian relaxation. The subgradient method can optimize the set of solution. To verify the proposed method, we presented the improved resutls of the systems composed of two and ten component groups as the commparison of those in other papers.

지금까지 대부분의 리던던시 할당문제(RAP: redundancy allocation problems) 관련 연구들에서는 최상위 수준에서의 시스템 리던던시보다는 최하위 수준인 부품의 리던던시를 고려하였다. 이는 최하위 수준에서의 리던던시가 최상위 수준의 리던던시보다 효과적이라고 알려진 일반적 원리 때문이었다. 최근 한 연구에서는 동일하지 않은 예비부품을 사용하여 리던던시를 실시하는 경우 직렬구조의 시스템에서도 일반적 원리와 다른 결과가 나타날 수 있음을 보이고, 시스템을 구성하는 모든 수준에서 리던던시가 가능한 다수준 리던던시 할당문제(MRAP: multi-level RAP)를 제시하였다. 그러나 MRAP는 모든 수준에서의 리던던시를 고려하지만 단지 한 수준을 선택하여 리던던시를 할 수 있다는 가정사항을 포함하고 있다. 본 연구에서는 MRAP의 이러한 가정사항을 완화하여 시스템을 구성하는 모든 수준에서 리던던시를 위한 수준을 복수로 선택 가능한 혼합 다수준 리던던시 할당문제(MMRAP: multiple MRAP)를 제시하고 모형화하며, 문제의 해법을 위한 유전자 알고리듬(GA: genetic algorithm)을 제시한다. 제시한 GA를 활용한 몇 가지 수치실험을 통해 모형이 기존의 RAP 경우보다 효과적임을 입증한다.