• 품질경영학회지
• /
• 제26권3호
• /
• pp.71-81
• /
• 1998

In reliability analysis, the time difference between the expected next failure time and the current failure time or the Mean Time Between Failure(MTBF) is of significant interest. Until recently, in reliability growth studies, the reciprocal of the intensity function at current failure time has been used as being equal to MTBE($t_n$)at the n-th failure time $t_n$. That is MTBF($t_n$)=l/$\lambda (t_n)$. However, such a relationship is only true for Homogeneous Poisson Process(HPP). Tsokos(1995) obtained the upper bound and lower bound for the MTBF($t_n$) and proposed an estimator for the MTBF($t_n$) as the mean of the two bounds. In this paper, we provide the estimator for the MTBF($t_n$) which does not depend on the value of the shape parameter. The result of the Monte Carlo simulation shows that the proposed estimator has better efficiency than Tsokos's estimator.

• 한국ITS학회:학술대회논문집
• /
• 한국ITS학회 2004년도 제3회 정기총회 및 추계학술대회
• /
• pp.192-197
• /
• 2004

• 한국산학기술학회논문지
• /
• 제17권11호
• /
• pp.432-436
• /
• 2016

열상 감시 장비의 핵심부품인 냉각기는 검출기 온도를 낮춰서 열상 감시 장비가 제 기능을 발휘하게 해준다. 해외 도입품으로서 기준사용시간이 20,000시간으로 제시되었고 이에 맞춰서 운용하고 있다. 양산 후 운용 중에 고장이 발생하기 시작했고, 그 고장으로 인해 냉각기의 MTBF분석을 해볼 필요성을 느꼈다. 군과 방산 업체에서 열상 감시 장비의 냉각기 고장데이터를 수집하였고 221개의 납품된 냉각기 중 73개의 냉각기가 운용 중에 고장이 발생하였다. 이 고장데이터에 생존확률 함수를 모수적 접근방법을 사용하여 적합한 분포를 파악을 하였고, 로그 로지스틱 분포가 적합하다고 추정되었다. 로그로지스틱 분포의 모수를 기반으로 냉각기의 MTBF를 분석하였다. 해외 업체가 제시한 MTBF와 비교하였고 또한 냉각기의 시간대별 신뢰도를 분석해보았다. 군 운용환경 중 고장이 발생한 냉각기의 MTBF를 분석함으로써 품질보증활동의 개선점을 찾을 수 있다. 실측 MTBF는 해외 업체에서 제시한 것보다 높게 나왔지만 운용 환경과 분석 방법론에 따른 차이는 존재한다. 이 분석 결과는 군에서 해외 도입품을 운용하는 현시점에 장비 정비주기와 운영시간에 영향을 줄 수 있고, 향후 냉각기 국산화 시 보조 자료로 기여할 것이라 판단된다.

• Journal of Information Technology Applications and Management
• /
• 제24권1호
• /
• pp.25-32
• /
• 2017

For repairable software systems, the Mean Time Between Failure (MTBF) is used as a measure of software system stability. Therefore, the evaluation of software reliability requirements or reliability characteristics can be applied MTBF. In this paper, we want to compare MTBF in terms of parameter estimation using Makeham life distribution. The parameter estimates used the least square method which is regression analyzer method and the maximum likelihood method. As a result, the MTBF using the least square method shows a non-decreased pattern and case of the maximum likelihood method shows a non-increased form as the failure time increases. In comparison with the observed MTBF, MTBF using the maximum likelihood estimation is smallerd about difference of interval than the least square estimation which is regression analyzer method. Thus, In terms of MTBF, the maximum likelihood estimation has efficient than the regression analyzer method. In terms of coefficient of determination, the mean square error and mean error of prediction, the maximum likelihood method can be judged as an efficient method.

• 산업공학
• /
• 제1권2호
• /
• pp.67-74
• /
• 1988

MTBF (Mean Time Between Failures) is one of the measures to express the reliability for a repairable system, especially for a military weapon system. But MTBF is meaningless without a clear definition of the system failures. In this paper we discuss two failure definitions, one is defined by US Army Training and Doctrine Command jointly with US Army Materiel Command and the other one is used to M1 Tank.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제18권3호
• /
• pp.250-259
• /
• 2018

Purpose: Previously, missile reliability prediction is based on theoretical failure prediction model. It has shown that the predicted reliability is inadequate to real field data. Although an MTTF based reliability prediction method using real field data has recently been studied to overcome this issue. In this paper, we present a more realistic method, considering MTBF concept, to predict missile reliability. Methods: In this paper we proposed a modified survival model. This model is considering MTBF as its core concept, and failed missiles in the model are to be repaired and redeployed. We compared the modified model (MTBF) and the previous model (MTTF) in terms of fitness against the real failure data. Results: The reliability prediction result of MTBF based model is closer to fields failure data set than that of MTTF based model. Conclusion: The proposed MTBF concept is more fitted to real failure data of missile than MTTF concept. The methodology of this study can be applied to analyze field failure data of other similar missiles.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제18권3호
• /
• pp.201-207
• /
• 2018

Purpose: To develop the reliability growth planning for a subsystem of guided weapon system using PM2-Continuous model. Methods: The target MTBF of the subsystem is set by allocating the system target MTBF to the lower level, where ARINC method is applied. Other model parameters such as initial MTBF, management strategy ratio and average fix effectiveness factor are chosen from historical growth parameter estimates. Given the values of model parameters, the reliability growth planning curve using PM2-Continuous model is constructed and the sensitivity analyses are performed for the changes of model parameters. Results: We have developed the reliability growth plan for a subsystem of guided weapon system using PM2-Continuous model. It was found that the smaller the ratio of initial MTBF to target MTBF, the smaller the management strategy ratio, the smaller the average fix effectiveness factor, and the shorter the development test period, the higher reliability growth is required. Conclusion: The result of this study will be used as a basis for establishing the reliability growth plan, the test period setting and the budget appropriation for the similar system entering the system development stage in the future.

• 산업공학
• /
• 제4권2호
• /
• pp.35-42
• /
• 1991

Many authors derived MTTF/MTBF for an operating system by analyzing its actual life time data. However, it is difficult to derive MTTF/MTBF when few breakdowns accur throughout a year. In this paper, we address a new approach to solve that problem under a preventive maintenance policy, in which few breakdowns occur, and also introduce a case study using the results obtained.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2006년도 춘계학술대회 논문집
• /
• pp.1215-1220
• /
• 2006

• 대한기계학회논문집A
• /
• 제36권2호
• /
• pp.157-164
• /
• 2012

많은 기능 또는 임무를 수행하는 다수의 부품들로 구성되어 있는 다기능 시스템 개발에 있어 시스템과 부품의 신뢰도(reliability), 가용도(availability) 그리고 정비도(maintainability)를 결정하는 것은 설계 단계에서의 중요한 일이다. 본 논문에서는 시스템을 구성하고 있는 최하위 부품을 대상으로 개발기준의 시스템 목표가용도(target availability)를 만족하는 각 구성품의 MTBF 와 MTTR 을 결정하고자 한다. 대안 생성을 위해 휴리스틱 기법(heuristic method)을 개발하였으며, 각 대안의 시스템 가용도와 수명주기비용을 계산하기 위해 시뮬레이션을 이용한다. 그리고 수치예제를 통해 모형매개변수의 영향을 알아 본다.