총 수명유지비를 고려한 무기체계 신뢰도 할당 모형

문미남,고선용,나호영,유권태 육군사관학교 화랑대연구소 2010 한국군사학논집 Vol.66 No.1

A minor defect in weapon systems such as aircraft, high-speed vehicle and nuclear power system, can cause fatal consequences. Thus, the weapon systems are requested high reliability to guarantee the use in the battlefield without any defects. Most of researches dealt with reliability maximization problem under considering the limited budget. But in practice, the majority of defense acquisition program go over their budget. Therefore, weapon developers have to consider the use of cost within the budget as well as reliability. Usually, reliability allocation problems are classified into two types :Maximization of the reliability within the budget and minimization of the cost with target reliability. In this research, unlike the previous two types of reliability allocation models which considered the initial acquisition cost in the phase of R&D, we suggest a new reliability allocation model which considers the maintenance costs after the force integration. Initial acquisition cost of weapon systems which have series and parallel mixed structure is expressed as a function,and Markov Chain model is used to calculate the expected value of maintenance cost which can be raised by fault repair and replacement. Based on that, we suggest a reliability allocation mathematics model of the objective function of total required costs optimization by nonlinear programing. In conclusion, we can figure out that, in case of weapon system acquisition program within the budget, the reliability allocation which optimize the maintenance costs while achieving target reliability with minimum cost is more efficient than traditional way of allocating reliability into sub-structures of weapon system with maximization of total reliability.

L.E.O. Satellite Power Subsystem Reliability Analysis

M. Zahran,S. Tawfik,Gennady Dyakov 전력전자학회 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.2

Satellites have provided the impetus for the orderly development of reliability engineering research and analysis because they tend to have complex systems and hence acute problems. They were instrumental in developing mathematical models for reliability, as well as design techniques to permit quantitative specification, prediction and measurement of reliability. Reliability engineering is based on implementing measures which insure an item will perform its mission successfully. The discipline of reliability engineering consists of two fundamental aspects; (1<SUP>st</SUP>) paying attention to details, and (2<SUP>nd</SUP>) handling uncertainties. This paper uses some of the basic concepts, formulas and examples of reliability theory in application.<br/> This paper emphasizes the practical reliability analysis of a Low Earth Orbit (LEO) Micro-satellite power subsystem. Approaches for specifying and allocating the reliability of each element of the power system so as to meet the overall power system reliability requirements, as well as to give detailed modeling and predicting of equipment/system reliability are introduced. The results are handled and analyzed to form the final reliability results for the satellite power system. The results show that the Electric Power Subsystem (EPS) reliability meets the requirements with quad microcontrollers (MC), two boards working as main and cold redundant while each board contains two MCs in a hot redundant.

Reliability Analysis and Prediction on Tunnel Roof under Blasting Disturbance

Pengfei Wu,Tianjiao Yang,Weichao Jia 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.9

The parameters of underground structure have the characteristics of large spatial heterogeneity and strong uncertainty. Recently, people gradually begin to use the idea of probability to analyze the safety of underground structures. However, few articles analyze the dynamic response of structural reliability. In this paper, the reliability of tunnel roof under blasting disturbance is studied, and the influence of the number of disturbances and the distribution of random variables on the structural reliability is analyzed. The prediction model of structural reliability is proposed. The sensitivity of different parameters to the structural reliability is discussed. The results show that the traditional method of evaluating the structural safety status is more dependent on the design value of each parameter. However, the design value does not represent the true state of the structure in a completely accurate way, which will result in a certain deviation between the assessment of the structural safety state and the actual state. Single disturbance has a limited impact on the structural reliability, while repeated disturbances can still have a noticeable effect on the structural reliability. When the disturbance reaches a certain number of times, the reliability of the structure can drop sharply. This paper proposes the prediction function of structure reliability according to the decay of structure reliability after blasting disturbance. Only a small number of parameters are needed to predict the structure reliability at different times. The error between the forecast results and the actual results is about 1%. With the increase of the number of blasting disturbances, the sensitivity coefficient of the structural resistance factor gradually decreases, and the sensitivity coefficient of the loaded effect gradually increases. The control of the blasting strength should be gradually increased to ensure the structural safety. Even if the mean and mean square error of random variables are the same, different distribution forms will have a great impact on the calculation results.

안전무결성 수준 및 MTTFd를 활용한 개발단계의 고성능 지상체 신뢰도 예측 방안

이민영,김상부,배인화,강소연,곽우영,이성근,오극기,최대림 한국산업융합학회 2024 한국산업융합학회 논문집 Vol.27 No.3

System reliability prediction in the development stage is increasingly crucial to reliability growth management to satisfy its target reliability, since modern system usually takes a form of complex composition and various complicated functions. In most cases of development stage, however, the information available for system reliability prediction is very limited, making it difficult to predict system reliability more precisely as in the production and operating stages. In this study, a system reliability prediction process is considered when the reliability-related information such as SIL (Safety Integrity Level) and MTTFd (Mean Time to Dangerous Failure) is available in the development stage. It is suggested that when the SIL or MTTFd of a system component is known and the field operational data of similar system is given, the reliability prediction could be performed using the scaling factor for the SIL or MTTFd value of the component based on the similar system’s field operational data analysis. Predicting a system reliability is then adjusted with the conversion factor reflecting the temperature condition of the environment in which the system actually operates. Finally, the case of applying the proposed system reliability prediction process to a high performance mooring platform is dealt with. ReliabilitSystem reliability prediction in the development stage is increasingly crucial to reliability growth management to satisfy its target reliability, since modern system usually takes a form of complex composition and various complicated functions. In most cases of development stage, however, the information available for system reliability prediction is very limited, making it difficult to predict system reliability more precisely as in the production and operating stages. In this study, a system reliability prediction process is considered when the reliability-related information such as SIL (Safety Integrity Level) and MTTFd (Mean Time to Dangerous Failure) is available in the development stage. It is suggested that when the SIL or MTTFd of a system component is known and the field operational data of similar system is given, the reliability prediction could be performed using the scaling factor for the SIL or MTTFd value of the component based on the similar system’s field operational data analysis. Predicting a system reliability is then adjusted with the conversion factor reflecting the temperature condition of the environment in which the system actually operates. Finally, the case of applying the proposed system reliability prediction process to a high performance mooring platform is dealt with.y Prediction, Safety Integrity Level, MTTFd, Scaling Factor, Conversion Factor

Reliability prediction of engineering systems with competing failure modes due to component degradation

손영갑 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.7

Reliability of an engineering system depends on two reliability metrics: the mechanical reliability, considering component failures, that a functional system topology is maintained and the performance reliability of adequate system performance in each functional configuration. Component degradation explains not only the component aging processes leading to failure in function, but also system performance change over time. Multiple competing failure modes for systems with degrading components in terms of system functionality and system performance are considered in this paper with the assumption that system functionality is not independent of system performance. To reduce errors in system reliability prediction, this paper tries to extend system performance reliability prediction methods in open literature through combining system mechanical reliability from component reliabilities and system performance reliability. The extended reliability prediction method provides a useful way to compare designs as well as to determine effective maintenance policy for efficient reliability growth. Application of the method to an electro-mechanical system, as an illustrative example, is explained in detail,and the prediction results are discussed. Both mechanical reliability and performance reliability are compared to total system reliability in terms of reliability prediction errors.

발목관절 복합체의 가동범위 측정을 위한 중립위치와 측정방법의 신뢰도

홍완성,김기원,Hong, Wan-Sung,Kim, Gi-Won 대한물리치료학회 2011 대한물리치료학회지 Vol.23 No.4

Purpose: To determine the correct measurement methods of the ankle joint complex range of motion for measuring the neutral position and evaluate the rater reliability. In addition, the impact of training on the rater reliability was also assessed. Methods: The subjects were eleven healthy women, who were evaluated by two physical therapists and one physical therapist recorded the results of the study. Standard goniometer was used as the measurement tool. The ankle and subtalar joint neutral position and the active range of motion of the ankle and subtalar joint were measured. Intra-rater reliability and inter-rater reliability measures were analyzed with intraclass correlation coefficients. Results: Intra-rater reliability and inter-rater reliability ranged from high to medium for the neutral position of the ankle joint complex. Intra-rater reliability for dorsiflexion and plantarflexion measurements was medium, while the inter-rater reliability was high. The range of motion of the subtalar joint was measured, and the intra-rater reliability and inter-rater reliability were low and medium, respectively Also, the intra-rater reliability was increased with formal training of the measurement techniques. Intra-rater reliability was reduced in case the raters had not undertaken the training. Conclusion: In summary, the results obtained with the measurement tools and joint measurement of position, indicate the consistency of repeated measurements made by the same observers. Under the same circumstances along with repetition of the same measurement technique during training caused an increase in the rater reliability of formally trained raters.

Reliability growth analysis of <i>k-out-of-N</i> systems using matrix-based system reliability method

Byun, Ji-Eun,Noh, Hee-Min,Song, Junho Elsevier 2017 Reliability engineering & system safety Vol.165 No.-

<P><B>Abstract</B></P> <P>The advent of ever more complex systems in extensive areas of industries hampers efficient and accurate analysis of reliability and effective reliability-based decision making. Such difficulties may arise from the intricate formulation of system failure events, statistical dependence between component failure events, and the convoluted quantification of underlying probabilities of basic events. So-called <I>k-out-of-N</I> systems, which survive or succeed when at least <I>k</I> components are available among the total of <I>N</I> components, give rise to a high level of complexity. This type of systems are commonly introduced to secure a proper level of redundancy in operating engineering systems, but the intricate definition of the system events may elude the system reliability analysis. It is noted that such <I>k-out-of-N</I> systems are often tested and corrected over a certain period of time before their official usage or release in order to assure the target reliability of the system. For the purpose of reliability prognosis based on the data collected from the test period, reliability growth models (RGMs) have been widely used in software and hardware engineering. However, RGMs have been applied mostly to individual components, not at the system level. Furthermore, in complex systems such as <I>k-out-of-N</I> system, it is challenging to relate the reliability growth of components with that of the system. To address this need, in this paper, the matrix-based system reliability (MSR) method is extended to <I>k-out-of-N</I> systems by modifying the formulations of event and probability vectors. The proposed methods can incorporate statistical dependence between component failures for both homogeneous and non-homogeneous <I>k-out-of-N</I> systems, and can compute measures related to parameter sensitivity and relative importance of components. The reliability growths of components represented by RGMs are incorporated into the proposed system reliability method, so that the trend of <I>system</I> reliability growth can be effortlessly evaluated and predicted. Two numerical examples are introduced in this paper to demonstrate the proposed method and its applications: (1) hypothetical systems each consisting of series, parallel and <I>k-out-of-N</I> subsystems, and (2) a simplified high speed train system modeled by multiple <I>k-out-of-N</I> subsystems. Two types of RGMs, i.e. non-homogeneous Poisson process (NHPP) and Duane models are employed in these examples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MSR method is extended to evaluate the reliability growth of <I>k-out-of-N</I> systems. </LI> <LI> The time-varying reliability of system can be evaluated from that of components. </LI> <LI> The extended MSR method can account for statistical dependence between components. </LI> <LI> By-products of reliability analysis can support systematic decision-making. </LI> <LI> Numerical examples show the MSR method is applicable to various configurations. </LI> </UL> </P>

Reliability-Based Design for Market Systems (RBDMS) : Case Study on Electric Vehicle Design

Ungki Lee(이웅기),Namwoo Kang(강남우),Ikjin Lee(이익진) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11

When designing a product, both engineering uncertainty and market heterogeneity should be considered to reduce the risk of failure in the market. Reliability-based design optimization (RBDO) approach allows decision makers to achieve target confidence in product performance under engineering uncertainty. On the other hand, design for market systems (DMS) approach helps decision makers to find profit-maximized product design under market heterogeneity. This paper proposes a reliability-based design for market systems (RBDMS) framework for electric vehicle (EV) design by integrating RBDO and DMS approaches. In RBDO, the product quality is controlled based on arbitrarily defined reliability. However, from the viewpoint of the company, it is necessary to set the appropriate reliability since the increased reliability increases both consumer satisfaction and manufacturing cost. Therefore, by modeling how reliability affects the customer choice, the optimum reliability which maximizes the profit can be derived. The “reliability” in the framework is used as follows: (1) a decision variable; (2) an attribute that directly influences the customer preference; (3) standards to determine advertised performance; and (4) reliability constraints in engineering model. We optimized and compared four scenarios depending on whether engineering systems are deterministic or probabilistic, and whether a market is homogeneous or heterogeneous. The results show that designing an entry EV model with low reliability is recommended under engineering uncertainty and market heterogeneity, while designing a premium EV model with high reliability is recommended to ensure the robustness of the profit.

Reliability of Hip Migration Index in Children with Cerebral Palsy: The Classic and Modifi ed Methods

Sun Mi Kim,박은숙,Eun Geol Sim,Seong Gyu Lim 대한재활의학회 2012 Annals of Rehabilitation Medicine Vol.36 No.1

Objective To determine reliability and clinical use of two methods of migration index (MI) in CP patients with or without hip dysplasia. Method The materials included radiographs of 200 hips of children with cerebral palsy. Conventional anteroposterior radiographs of the pelvis were taken with the child in the supine position with standardized methods. Two rehabilitation doctors measured the migration index using two methods. In the classic method,the lateral margin of the acetabular roof was used as a landmark and in the modifi ed method the lateral margin of the sourcil was used as a landmark. Each rater measured the migration index at three separate times with a time interval of at least one week. Intraclass correlation (ICC) was used to test the inter- and intra-rater reliability. Results MI shows excellent intra-rater reliability in both the classic and modified methods, but the inter-rater reliability was higher in the classic method than in the modified method. When categorized according to the sourcil classifi cation, inter-rater reliability was higher in the normal sourcil type and lower in the dysplastic sourcil types. Conclusion Generally, the classic method showed higher reliability than the modifi ed method, even though the reliability of the MI measurement was relatively high with both methods. Objective To determine reliability and clinical use of two methods of migration index (MI) in CP patients with or without hip dysplasia. Method The materials included radiographs of 200 hips of children with cerebral palsy. Conventional anteroposterior radiographs of the pelvis were taken with the child in the supine position with standardized methods. Two rehabilitation doctors measured the migration index using two methods. In the classic method,the lateral margin of the acetabular roof was used as a landmark and in the modifi ed method the lateral margin of the sourcil was used as a landmark. Each rater measured the migration index at three separate times with a time interval of at least one week. Intraclass correlation (ICC) was used to test the inter- and intra-rater reliability. Results MI shows excellent intra-rater reliability in both the classic and modified methods, but the inter-rater reliability was higher in the classic method than in the modified method. When categorized according to the sourcil classifi cation, inter-rater reliability was higher in the normal sourcil type and lower in the dysplastic sourcil types. Conclusion Generally, the classic method showed higher reliability than the modifi ed method, even though the reliability of the MI measurement was relatively high with both methods.

Reliability Evaluation of Power System Operations Considering Time-Varying Features of Components

Bo Hu,Ying Zheng,Hejun Yang,Yun Xia 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.4

The reliability of power system components can be affected by a numbers of factors such as the health level of components, external environment and operation environment of power systems. These factors also affect the electrical parameters of power system components for example the thermal capacity of a transmission element. The relationship of component reliability and power system is, therefore, a complex nonlinear function related to the above-mentioned factors. Traditional approaches for reliability assessment of power systems do not take the influence of these factors into account. The assessment results could not, therefore, reflect the short-term trend of the system reliability performance considering the influence of the key factors and provide the system dispatchers with enough information to make decent operational decisions. This paper discusses some of these important operational issues from the perspective of power system reliability. The discussions include operational reliability of power systems, reliability influence models for main performance parameters of components, time-varying reliability models of components, and a reliability assessment algorithm for power system operations considering the time-varying characteristic of various parameters. The significance of these discussions and applications of the proposed techniques are illustrated by case study results using the IEEE-RTS.