Wyniki wyszukiwania - Biblioteka Nauki

1

Reliability modeling of fault tolerant control systems

100%

Li H. , Zhao Q. , Yang Z.

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tom 17

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nr 4

491-504

EN

This paper proposes a novel approach to reliability evaluation for active Fault Tolerant Control Systems (FTCSs). By introducing a reliability index based on the control performance and hard deadline, a semi-Markov process model is proposed to describe system operation for reliability evaluation. The degraded performance of FTCSs in the presence of imperfect Fault Detection and Isolation (FDI) is reflected by semi-Markov states. The semi-Markov kernel, the key parameter of the process, is determined by four probabilistic parameters based on the Markovian model of FTCSs. Computed from the transition probabilities of the semi-Markov process, the reliability index incorporates control objectives, hard deadline, and the effects of imperfect FDI, a suitable quantitative measure of the overall performance.

2

Reliability evaluation of renewable energy-based power system containing energy storage

100%

Ghaeedi A. , Noroozi E.

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tom Vol. 10, nr 32

198--205

EN

In recent years, renewable energy based power plants, especially wind and solar farms are increasingly installed and operated for electric power generation. Uncertainty nature associated to the generated power of these power plants, arisen from variability of wind speed or solar radiation, effects on different aspects of power system such as reliability, operation, dynamic and so on. Energy storages in connection with renewable power plants can reduce the variability and uncertainty nature of these renewable resources. In recent years the flow batteries such as vanadium redox (VR) with large capacities are developed and so in this paper effect of this largecapacity energy storages on the reliability performance of power system containing large-scale wind and photovoltaic (PV) farms are investigated. The renewable energy-based power plants and also energy storages are different from conventional units, so, for study of power system containing these resources new methods and techniques must be developed. To this end in this paper for reliability evaluation of renewable-energy based power system containing energy storage, an analytical approach is proposed. This approach can be employed both in planning and also operation studies of the power system when large scale wind and photovoltaic farms with energy storages exist. Data associated to wind speed of Manjil and solar radiation of Jask regions both in Iran are utilized for studying the reliability evaluation of RBTS and also IEEERTS in planning phase.

3

Fault analysis and reliability evaluation for motorized spindle of cycloidal gear grinding machine based on multi-source bayes

88%

Wang H. , Zhang Z. , Li J. , Xin W. , Han C.

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tom Vol. 26, no. 1

art. no. 175010

EN

A Monte Carlo simulation method based on multisource bayes is proposed to improve the reliability of motorized spindles in cycloid gear grinding machines and reduce their failure rate. Based on field investigations and motorized spindle maintenance records, a fault tree model of a motorized spindle was established, and the fuzzy importance of each bottom event was evaluated. The fault tree of a motorized spindle was used as a Monte Carlo reliability simulation model, and its importance was used as the input parameter for the simulation. The reliability evaluation index of the motorized spindle was obtained at different simulation times. The feasibility and accuracy of the reliability simulation were verified by comparing the importance and simulation importance. A vibration test was designed for bearing faults with high importance, and fault extraction was performed by combining the wavelet packet transform and empirical mode decomposition. This method can also be used to simulate and analyze the reliability of other equipment or machine tools.

4

Reliability analysis of the products subject to competing failure processes with unbalanced data

63%

Li J. , Zhang Y. , Wang Z. , Fu H. , Xiao L.

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tom Vol. 18, no. 1

98--109

EN

Considering the degradation and catastrophic failure modes simultaneously, a general reliability analysis model was presented for the competing failure processes with unbalanced data. For the degradation process with highly unbalanced data, we developed a linear random-effects degradation model. The model parameters can be estimated based on a simple least square method. Furthermore, to fully utilize the degradation information, we considered the last measured times of the degradation units that had only one or two measured time points as zero-failure data or right-censored data of the catastrophic failure mode. Then the incomplete data set was composed of zero-failure data and catastrophic failure data. To analyze the incomplete data, the definition of the interval statistics was firstly given. The best linear unbiased parameter estimators of catastrophic failure were obtained based on the Gauss-Markov theorem. Then, the reliability function of the competing failure processes was given. The corresponding two-sided confidence intervals of the reliability were obtained based on a bootstrap procedure. Finally, a practical application case was examined by applying the proposed method and the results demonstrated its validity and reasonability.

PL

W pracy przedstawiono ogólny model analizy niezawodności procesów związanych z powstawaniem uszkodzeń konkurujących, który pozwala na wykorzystanie danych niezbilansowanych oraz umożliwia jednoczesne uwzględnienie uszkodzeń wynikających z obniżenia charakterystyk i uszkodzeń katastroficznych. Opracowano liniowy model efektów losowych dla procesu degradacji o wysoce niezbilansowanych danych. Parametry tego modelu można określić na podstawie prostej metody najmniejszych kwadratów. Ponadto, aby w pełni wykorzystać informacje dotyczące obniżenia charakterystyk, dane pochodzące z ostatniego pomiaru jednostek podlegających degradacji, dla których przeprowadzono tylko jeden lub dwa pomiary, rozpatrywano jako dane o zerowym uszkodzeniu lub jako ucięte prawostronnie dane dotyczące uszkodzenia katastroficznego. W ten sposób otrzymano zbiór niepełnych danych składający się z danych o uszkodzeniach zerowych oraz danych o uszkodzeniach katastroficznych. Aby móc przeanalizować uzyskane niepełne dane, podano definicję statystyki przedziałowej. Najefektywniejszy nieobciążony estymator liniowy (BLUE) parametrów uszkodzeń katastroficznych uzyskano na podstawie twierdzenia Gaussa-Markowa. Następnie, podano wzór funkcji niezawodności procesów związanych z powstawaniem uszkodzeń konkurujących. Odpowiednie dwustronne przedziały ufności dla oszacowanej niezawodności uzyskano metodą bootstrapową. Na koniec, przedstawiono przypadek praktycznego zastosowania proponowanej metody, którego wyniki wykazały jej trafność i zasadność.