| In reliability engineering, series-parallel compound system is a common type of thecompound systems. It consists of several parallel subsystems connected in series orconsists of several series subsystems connected in parallel, that is, series-parallel systemand parallel-series system. Repairable series-parallel compound system has been appliedto a variety of engineering domains, including power transmission systems, coal supplymechanical systems, sewage systems, heating systems, production systems, and computernetwork transmission systems, etc.The reliability theory of irreparable series-parallel compound systems has beenrelatively mature. By contrast, the reliability modeling and analysis for the repairableseries-parallel compound systems are more complicated. In recent years, the reliability ofthe repairable series-parallel compound system in theory research and engineeringapplications has made certain progress, but there are some imperfect theory and criticalissues. Based on the diversity of improve methods for availability, different units, variousstates, complex dependency and scarce data in engineering practice, this dissertationcarries on three aspects of research, including system availability analysis, design andapplication. Availability analysis methods and design scheme are proposed.Firstly, availability improvement and equivalence design of repairable series-parallelcompound systems with two states and multi-state are discussed under failureindependence assumption. The availability of the improved systems according to factorimprovement method and standby redundancy method is calculated respectively. Theavailability equivalence factor is introduced to compare different designs, and two types ofavailability equivalence factors are obtained. Based on availability equivalence factors, theavailability equivalence problem of the improved systems according to the factorimprovement method and the standby redundancy method is solved.Secondly, availability of repairable series-parallel compound systems with failuredependencies and limited repair facilities is analyzed. To quantify the redundantdependency, a dependence function and an improved dependence function are introduced. Based on Markov process theory and matrix analytic method, the steady-state probabilityof each subsystem are analyzed in detail, system availability is obtained. Effect of failuredependency on the system availability is discussed, and the availability equivalence designis analyzed.Then, fuzzy state probabilities and fuzzy availability for repairable series-parallelcompound multi-state systems are analyzed. According to the fuzzy mathematical theoryand traditional Markov model, a fuzzy Markov model of the repairable multi-statecomponent is proposed. Using the cut set method of fuzzy number, parameterprogramming technology and fuzzy universal generation function, the fuzzy performancelevels, the fuzzy state probabilities and the fuzzy availability of the system are assessed. Asimple method is proposed to evaluate the availability of the repairable series-parallelcompound multi-state systems, and it is compared with the existing method throughnumerical example.Finally, based on the availability of the repairable series-parallel compound systems,the optimization design and related application are studied. The optimization designscheme of the availability improvement methods is proposed according to factorimprovement method and standby redundancy method. An optimal allocation model withredundant failure dependency is provided, the effect of redundant failure dependency onthe system cost is analyzed. Further, a series-parallel production system illustrates theresearch results of availability improvement and equivalence design. The originalavailability and improved availability of the cylinder cover production line are analyzed.The equivalence design of the production line is studied by the availability equivalencefactors. |
PDF Full Text Request