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 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>

Human Reliability Analysis of Soft Control Operations in Nuclear Power Plants: Issues and Perspectives

Seung Jun Lee,Wondea Jung 대한인간공학회 2013 大韓人間工學會誌 Vol.32 No.1

Objective: The aim of this study is to describe several issues which should be considered in the human reliability analysis of soft control operations in nuclear power plants. Background: The operational environment of advanced main control rooms is totally different from that of conventional control rooms. The soft control is one of the major distinguishable features of the advanced main control rooms. The soft control operations should be analyzed to estimate the effects on human reliability. Method: The literatures, about task analysis, simulation data analysis, and a human reliability analysis method for the soft control, were reviewed. From the review, important issues for the human reliability analysis of the soft control were raised. Results: The results of task and simulation data analysis showed that the soft control characteristics could have large effect on human reliability and they should be considered in the human reliability analysis of the soft control operations. Conclusion: The soft control may affect human error and performance of operators. The issues described in this paper should be considered in the human reliability method for the advanced main control rooms. Application: The results of the soft control operation analysis might help to design more efficient interface and education/training program for preventing human errors. The described issues might help to develop a human reliability analysis method for soft control operations.

Bayesian approach for reliability analysis of side load spring design problem

안다운(Dawn An),최주호(Jooho Choi),원준호(Junho Won) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

Bayesian approach for the structural reliability analysis is proposed, which can deal with the epistemic uncertainty arising due to the limited number of data. Until recently, the conventional reliability analysis mostly dealt with the aleatory uncertainty in which the statistical properties are completely known. In practice, however, this is not the case due to the insufficient data for estimating the statistical information, which makes the existing methods less useful. In the Bayesian approach, the probability itself is a random variable conditioned by the observed data, and is represented by a PDF, which is obtained by conducting a double loop of reliability analyses. KDRM is employed for the efficient implementation of the reliability analysis, which can construct the PDF of the limit state function with favorable accuracy under a small number of analyses Mathematical examples are used to verify the proposed method. A reliability problem of a side load spring is solved as an example for practical application.

Reliability and Validity of Measurement Using Smartphone - Based Goniometer of Tibial External Rotation Angle in Standing Knee Flexion

In-cheol Jeon,Oh-yun Kwon,Jong-hyuck Weon,Sung-min Ha,Si-hyun Kim 한국전문물리치료학회 2013 한국전문물리치료학회지 Vol.20 No.2

The purpose of this study was to assess the intra-rater test-retest reliability of tibial external rotation angle measurement using a smartphone-based photographic goniometer, DrGoniometer (DrG) compared to a three-dimensional motion analysis system (Vicon). The current study showed an interchangeable method using DrG to measure the tibial external rotation angle in standing knee flexion at 9°. Twelve healthy subjects participated in this study. A rest session was conducted 30 minutes later for within-day reliability and five days later for between-day intra-rater test-retest reliability. To assess the validity of the measurement using DrG, we used a three dimensional motion analysis system as a gold standard to measure the angle of tibial external rotation. Intra-class correlation coefficient (ICC) and the standard error of measurement (SEM) values were used to determine the within-and between-day intra-rater test-retest reliability of using DrG and a three dimensional motion analysis system. To assess validity, Pearson correlation coefficients were used for two measurement techniques. The measurement for tibial external rotation had high intra-rater test-retest reliability of within-day (ICC=.88) and between-day (ICC=.83) reliability using DrG and of within-day (ICC=.93) and between-day (ICC=.77) reliability using a three-dimentional motion analysis system. Tibial external rotation angle measurement using DrG was highly correlated with those of the three-dimensional motion analysis system (r=.86). These results represented that the tibial external rotation angle measurement using DrG showed acceptable reliability and validity compared with the use of three-dimensional motion analysis system.

Reliability Improvement of Machine Tool changing Servo Motor

Sung, Baek-Ju,Lee, Jong-Bae The Korean Institute of Electrical Engineers 2011 The Journal of International Council on Electrical Vol.1 No.1

First of all, it is the most important to know the cause and effect of major failures to increase the reliability of servo motor. All reliability parameters can be achieved after analysis of them and experiments based on the analysis data. So, we firstly made out the failure analysis data of servo motor such as FMMA, FMECA, FTA, and 2-stage QFD considering the reference materials, field failure data, and the opinion of experts of servo motor. And the test items were decided which are needed to evaluate the performance characteristics of servo motor as analysis results of failure analysis data. And then, the major reliability parameters are deduced by experiments and MINITAB analysis. In addition, according to prove a major failure mode of servo motor by above analysis results, we produced FEA (Finite Element Analysis) model about shape of stator and rotor of servo motor to find out the reducing method of cogging torque. This paper presents the useful major reliability parameters, detailed failure mode analysis data, experimental results using 3 samples, and a cogging torque reducing method of servo motor, and also verified the validity of the deduced parameters and analysis data.

L.E.O. Satellite Power Subsystem Reliability Analysis

Zahran M.,Tawfik S.,Dyakov Gennady The Korean Institute of Power Electronics 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; $(1^{st})$ paying attention to details, and $(2^{nd})$ handling uncertainties. This paper uses some of the basic concepts, formulas and examples of reliability theory in application. 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.

Selection and Reporting of Statistical Methods to Assess Reliability of a Diagnostic Test: Conformity to Recommended Methods in a Peer-Reviewed Journal

Park, Ji Eun,Han, Kyunghwa,Sung, Yu Sub,Chung, Mi Sun,Koo, Hyun Jung,Yoon, Hee Mang,Choi, Young Jun,Lee, Seung Soo,Kim, Kyung Won,Shin, Youngbin,An, Suah,Cho, Hyo-Min,Park, Seong Ho unknown 2017 KOREAN JOURNAL OF RADIOLOGY Vol.18 No.6

<P><B>Objective</B></P><P>To evaluate the frequency and adequacy of statistical analyses in a general radiology journal when reporting a reliability analysis for a diagnostic test.</P><P><B>Materials and Methods</B></P><P>Sixty-three studies of diagnostic test accuracy (DTA) and 36 studies reporting reliability analyses published in the <I>Korean Journal of Radiology</I> between 2012 and 2016 were analyzed. Studies were judged using the methodological guidelines of the Radiological Society of North America-Quantitative Imaging Biomarkers Alliance (RSNA-QIBA), and COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) initiative. DTA studies were evaluated by nine editorial board members of the journal. Reliability studies were evaluated by study reviewers experienced with reliability analysis.</P><P><B>Results</B></P><P>Thirty-one (49.2%) of the 63 DTA studies did not include a reliability analysis when deemed necessary. Among the 36 reliability studies, proper statistical methods were used in all (5/5) studies dealing with dichotomous/nominal data, 46.7% (7/15) of studies dealing with ordinal data, and 95.2% (20/21) of studies dealing with continuous data. Statistical methods were described in sufficient detail regarding weighted kappa in 28.6% (2/7) of studies and regarding the model and assumptions of intraclass correlation coefficient in 35.3% (6/17) and 29.4% (5/17) of studies, respectively. Reliability parameters were used as if they were agreement parameters in 23.1% (3/13) of studies. Reproducibility and repeatability were used incorrectly in 20% (3/15) of studies.</P><P><B>Conclusion</B></P><P>Greater attention to the importance of reporting reliability, thorough description of the related statistical methods, efforts not to neglect agreement parameters, and better use of relevant terminology is necessary.</P>

Selection and Reporting of Statistical Methods to Assess Reliability of a Diagnostic Test: Conformity to Recommended Methods in a Peer-Reviewed Journal

박지은,한경화,성유섭,정미선,구현정,윤희망,최영준,이승수,김경원,신영빈,안수아,조효민,박성호 대한영상의학회 2017 Korean Journal of Radiology Vol.18 No.6

Objective: To evaluate the frequency and adequacy of statistical analyses in a general radiology journal when reporting a reliability analysis for a diagnostic test. Materials and Methods: Sixty-three studies of diagnostic test accuracy (DTA) and 36 studies reporting reliability analyses published in the Korean Journal of Radiology between 2012 and 2016 were analyzed. Studies were judged using the methodological guidelines of the Radiological Society of North America-Quantitative Imaging Biomarkers Alliance (RSNA-QIBA), and COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) initiative. DTA studies were evaluated by nine editorial board members of the journal. Reliability studies were evaluated by study reviewers experienced with reliability analysis. Results: Thirty-one (49.2%) of the 63 DTA studies did not include a reliability analysis when deemed necessary. Among the 36 reliability studies, proper statistical methods were used in all (5/5) studies dealing with dichotomous/nominal data, 46.7% (7/15) of studies dealing with ordinal data, and 95.2% (20/21) of studies dealing with continuous data. Statistical methods were described in sufficient detail regarding weighted kappa in 28.6% (2/7) of studies and regarding the model and assumptions of intraclass correlation coefficient in 35.3% (6/17) and 29.4% (5/17) of studies, respectively. Reliability parameters were used as if they were agreement parameters in 23.1% (3/13) of studies. Reproducibility and repeatability were used incorrectly in 20% (3/15) of studies. Conclusion: Greater attention to the importance of reporting reliability, thorough description of the related statistical methods, efforts not to neglect agreement parameters, and better use of relevant terminology is necessary.

Reliability analysis of laminated composite shells by response surface method based on HSDT

Sandipan N. Thakur,Subrata Chakraborty,Chaitali Ray 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.2

Reliability analysis of composite structures considering random variation of involved parameters is quite important as composite materials revealed large statistical variations in their mechanical properties. The reliability analysis of such structures by the first order reliability method (FORM) and Monte Carlo Simulation (MCS) based approach involves repetitive evaluations of performance function. The response surface method (RSM) based metamodeling technique has emerged as an effective solution to such problems. In the application of metamodeling for uncertainty quantification and reliability analysis of composite structures; the finite element model is usually formulated by either classical laminate theory or first order shear deformation theory. But such theories show significant error in calculating the structural responses of composite structures. The present study attempted to apply the RSM based MCS for reliability analysis of composite shell structures where the surrogate model is constructed using higher order shear deformation theory (HSDT) of composite structures considering the uncertainties in the material properties, load, ply thickness and radius of curvature of the shell structure. The sensitivity of responses of the shell is also obtained by RSM and finite element method based direct approach to elucidate the advantages of RSM for response sensitivity analysis. The reliability results obtained by the proposed RSM based MCS and FORM are compared with the accurate reliability analysis results obtained by the direct MCS by considering two numerical examples.