Wyniki wyszukiwania - BazTech

1

Imperfect maintenance in correlated bivariate Wiener model

Bautista Lucía, Castro Inma T., Bérenguer Christophe, Gaudoin Olivier, Doyen Laurent

Safety and Reliability of Systems and Processes

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2023

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Summer Safety and Reliability Seminar 2023

7--17

EN

A two-unit system subject to imperfect maintenance is analyzed in this chapter. The deterioration of the system follows a bivariate Wiener degradation process. This process is built from the trivariate reduction method by sharing a common noise that describes the dependence between both units. This dependence is measured through the Pearson’s correlation coefficient between both degradation trajectories of the bivariate Wiener process at time t. A maintenance strategy consisting of periodic inspections in which the accumulated deterioration of the system is reduced by a certain quantity is implemented. Some results on the monotonicity of the Pearson’s correlation coefficient in different scenarios are obtained.

2

Selective maintenance optimization with stochastic break duration based on reinforcement learning

Liu Yilai, Qian Xinbo

Eksploatacja i Niezawodność

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2022

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Vol. 24, no. 4

771--784

EN

For industrial and military applications, a sequence of missions would be performed with a limited break between two adjacent missions. To improve the system reliability, selective maintenance may be performed on components during the break. Most studies on selective maintenance generally use minimal repair and replacement as maintenance actions while break duration is assumed to be deterministic. However, in practical engineering, many maintenance actions are imperfect maintenance, and the break duration is stochastic due to environmental and other factors. Therefore, a selective maintenance optimization model is proposed with imperfect maintenance for stochastic break duration. The model is aimed to maximize the reliability of system successfully completing the next mission. The reinforcement learning(RL) method is applied to optimally select maintenance actions for selected components. The proposed model and the advantages of the RL are verified by three case studies verify.

3

Maintenance grouping optimization for offshore wind turbine considering opportunities based on rolling horizon approach

Lua Y., Suna L., Kanga J., Zhang X.

Polish Maritime Research

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2018

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nr 2

123--131

EN

In future, offshore wind turbines may be consider a crucial part in the supply of energy. Maintenance processes are directed to attain a safe and reliable operation of offshore machines and wind turbines. In this paper, an opportunistic maintenance strategy for offshore wind turbine is proposed, considering imperfect maintenance and the preventive maintenance durations. Reliability Centric Maintenance serves as a proactive tactic to operations and maintenance by inhibiting the possible reasons of poor performance and controlling failures. Other components can implement the opportunistic preventive maintenances if one component has reached its reliability threshold. According to the rolling horizon approach, it is of great importance to update the maintenance planning for the sake of the short-term information. By figuring out the best combination, the maintenance schedule in the mission time has been finally determined. Failure information are obtained from previous studies to accomplish the calculations. The outcomes indicate that the maintenance cost has been dramatically reduced through the application of opportunistic maintenance.

4

Sequential preventive maintenance policies with consideration of random adjustment-reduction features

Peng W., Liu Y., Zhang X., Huang H.-Z.

Eksploatacja i Niezawodność

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2015

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Vol. 17, no. 2

306--313

EN

In existing literature, imperfect maintenance has been widely studied and many studies treat the effectiveness of imperfect maintenance as a fixed constant. In reality, it is more realistic to regard the maintenance efficiency as a random quantity as it may not be precise value due to the lack of sufficient data and/or the variation from system to system. In this paper, a hybrid imperfect maintenance model with random adjustment-reduction parameters is proposed, and a maintenance policy, namely the sequential preventive maintenance in periodic leisure interval, is studied based on the proposed hybrid random imperfect maintenance model, and the corresponding maintenance strategy is optimized by the genetic algorithm (GA). A numerical example and an example of the fuel injection pump of diesel engines are presented to illustrate the proposed method.

PL

W literaturze, temat konserwacji niepełnej został szeroko zbadany i wiele z opisywanych badań traktuje wydajność konserwacji niepełnej jako wartość stałą. W rzeczywistości jednak wydajność konserwacji należy traktować jako wielkość losową, ponieważ nie można jej dokładnie określić ze względu na brak wystarczających danych i / lub różnice między poszczególnymi systemami. W niniejszej pracy zaproponowano model hybrydowy konserwacji niepełnej łączący pojęcia parametrów losowej korekcji i losowej redukcji wieku. Na podstawie proponowanego modelu hybrydowego losowej konserwacji niepełnej przebadano strategię sekwencyjnej konserwacji zapobiegawczej przeprowadzanej okresowo w czasie wolnym od pracy; omawianą strategię konserwacji zoptymalizowano za pomocą algorytmu genetycznego (GA). Proponowaną metodę zilustrowano przykładem liczbowym oraz omówiono na przykładzie pompy wtryskowej paliwa do silników wysokoprężnych.

5

Inspection optimization model with imperfect maintenance based on a three-stage failure process

Yang R., Zhao F., Kang J., Li H., Teng H.

Eksploatacja i Niezawodność

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2015

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Vol. 17, no. 2

165--173

EN

Rolling element bearings are one of the most widely used and vulnerable components in complex systems. The condition monitoring work is very critical for sustaining the system’s availability and reducing the maintenance cost. Shock pulse method (SPM) is a common technique to measure the operating condition of rolling bearings as a three color scheme, e.g., green, yellow and red. This paper proposes an inspection model based on a three-stage failure process which aims to optimize the inspection interval of bearings by minimizing the expected cost per unit time. The three-stage failure process divides the bearings life into three stages before failure: good, minor defective and severe defective stages, corresponding to the three color scheme of SPM. Considering the need to lubricate bearings when the minor defective stage is identified by inspection in industrial applications, we assume that maintenance at the time of inspection identifying the minor defective stage is imperfect. The concept of proportional age reduction is used to model the effect of imperfect maintenance on the instantaneous rates of the minor defective stage, the severe defective stage and failure. Perfect maintenance however is carried out if inspection detects bearings being in the severe defective stage. Failure can be found once it occurs and replacement has to be implemented immediately. Finally, a numerical example is presented to illustrate the effectiveness of the proposed model.

PL

Łożyska toczne są jednymi z najczęściej stosowanych i jednocześnie najbardziej narażonych na uszkodzenia części składowych układów złożonych. Monitorowanie stanu odgrywa bardzo istotną rolę w utrzymaniu dostępności układów i zmniejszeniu kosztów ich obsługi. Metoda impulsów uderzeniowych (SPM) jest powszechnie stosowaną techniką służącą do pomiaru stanu pracy łożysk tocznych, który reprezentowany jest za pomocą kodu trzech kolorów, na przykład, zielonego, żółtego i czerwonego. W artykule zaproponowano model przeglądów oparty na trójfazowym procesie uszkodzenia, który ma na celu optymalizację częstotliwości przeglądów łożysk poprzez minimalizację oczekiwanych kosztów przypadających na jednostkę czasu. Pojęcie trójfazowego procesu uszkodzenia pozwala podzielić żywotność łożyska na trzy fazy przed wystąpieniem uszkodzenia: fazę dobrego stanu, fazę drobnych defektów i fazę poważnych defektów. Podział ten odpowiada kodowi trzech kolorów SPM. Biorąc pod uwagę konieczność smarowania łożysk po zdiagnozowaniu, podczas przeglądu w warunkach przemysłowych, wystąpienia fazy drobnych defektów, zakładamy, że konserwacja w czasie takiego przeglądu jest konserwacją niepełną. Koncepcja proporcjonalnego obniżenia wieku służy do modelowania wpływu niepełnej konserwacji na chwilowe wartości intensywności fazy drobnych defektów, fazy poważnych defektów oraz uszkodzeń. Gdy podczas przeglądu stwierdzi się, że łożysko jest w fazie poważnych defektów, przeprowadza się pełną konserwację. Uszkodzenie zostaje wykryte zaraz po jego wystąpieniu, i wtedy należy dokonać natychmiastowej wymiany łożyska. Pod koniec artykułu, przedstawiono przykład numeryczny, który ilustruje wydajność proponowanego modelu.

6

Repairable systems availability optimization under imperfect maintenance

Samet S., Chelbi A., Hmida F.B.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2009

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Vol. 57, nr 3

249-256

EN

This paper deals with the modeling of a preventive maintenance strategy applied to a single-unit system subject to random failures. According to this policy, the system is subjected to imperfect periodic preventive maintenance restoring it to 'as good as new1 with probability p and leaving it at state 'as bad as old' with probability q. Imperfect repairs are performed following failures occurring between consecutive preventive maintenance actions, i.e the times between failures follow a decreasing quasi-renewal process with parameter a. Considering the average durations of the preventive and corrective maintenance actions as well as their respective efficiency extents, a mathematical model is developed in order to study the evolution of the system stationary availability and determine the optimal PM period which maximizes it. The modeling of the imperfection of the corrective maintenance actions requires the knowledge of the quasi-renewal function. A new expression approximating this function is proposed for systems whose times to first failure follow a Gamma distribution. Numerical results arc obtained and discussed.

7

Particle Swarm Optimization Fuzzy Systems for the Age Reduction Imperfect Maintenance Model

Che-Hua Li Che-Hua

Eksploatacja i Niezawodność

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2008

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nr 4

28-34

EN

This research includes two topics: (1) the modeling of periodic preventive maintenance policies over an infi nite time span for repairable systems with the reduction of the degradation rate after performing an imperfect preventive maintenance (PM) activity; (2) the parameter estimation of failure distribution and the restoration effect of PM from the proposed PM policy for deteriorating systems. The concept of the improvement factor method is applied to measure the restoration effect on the degradation rate for a system after each PM. An improvement factor is presented as a function of the system's age and the cost of each PM. A periodic PM model is then developed. The optimal PM interval and the optimal replacement time for the proposed model can be obtained by minimizing the objective functions of the cost rate through the algorithms provided by this research. An example of using Weibull failure distribution is provided to investigate the proposed model. The method is proposed to estimate the parameters of the failure process and the improvement effect after each PM by analyzing maintenance and failure log data. In this method, a PSO-based method is proposed for automatically constructing a fuzzy system with an appropriate number of rules to approach the identifi ed system. In the PSO-based method, each individual in the population is constructed to determine the number of fuzzy rules and the premise part of the fuzzy system, and then the recursive least-squares method is used to determine the consequent part of the fuzzy system constructed by the corresponding individual. Consequently, an individual corresponds to a fuzzy system. Subsequently, a fi tness function is defi ned to guide the searching procedure to select an appropriate fuzzy system with the desired performance. Finally, two identifi cation problems of nonlinear systems are utilized to illustrate the effectiveness of the proposed method for fuzzy modeling.