Discrete-time T-S Dynamic Fault Tree Analysis Method And Application In Hydraulic System

The existing static fault trees can only describe the static logic relationship and can not describe the dynamic logic relationship between the events,such as time sequence,correlation and redundancy.Although the existing dynamic fault trees can describe the dynamic logic relationship,the fault-tree models base on Dugan dynamic gates,which is incapable of describing fuzzy dynamic logic relationships in the case of discrete task time and unable to model the two-state and multi-state systems with fuzzy logic relations.Aiming at the shortcomings of the existing fault tree analysis method,a discrete-time T-S dynamic fault tree analysis method is proposed.Firstly,based on the T-S model,the T-S dynamic gate can be constructed and the discrete-time T-S dynamic fault tree analysis method is proposed for the problem that the Dugan dynamic fault tree can not model the fuzzy logic relation.Transform existing static and dynamic fault tree logic gates into T-S gates,and the feasibility of the proposed fault tree is verified by comparing with the Dugan dynamic fault tree.Combined with pump and motor hydraulic system,the T-S dynamic gate calculation method can be used to calculate the dynamic fault tree which replaces Markov chain system by comparing the T-S dynamic gate calculation method with the Markov chain calculation method.Furthermore,a multi-state discrete-time T-S dynamic fault tree analysis method is proposed to solve the reliability problem of multi-state systems in engineering practice.Based on the analysis of unrepairable and repairable multi-state systems,T-S dynamic fault tree analysis method for unrepairable and repairable multi-state systems with different failure data definitions is established respectively.The multi-state discrete-time T-S dynamic fault tree is carried out for the hydraulic circuit of the crane and compared with the results of the two-state model analysis of the Dugan dynamic fault tree,the superiority of the proposed method in analyzing applicability and polymorphic modeling is verified.Then,a discrete-time T-S dynamic fault tree importance algorithm is proposed to measure the importance of basic events in the proposed method.Based on the importance degree algorithm of two-state fault tree and multi-state fault tree,considering the influence of time interval,the segmentation and overall probability importance,segmentation and overall critical importance.Finally,the reliability of the multi-state hydraulic system failure of the loader is analyzed,and the reliability analysis is carried out by using the discrete-time T-S dynamic fault tree analysis method and the importance degree algorithm.The probability of the failure state of the top event in each time period and the segmentation and overall probability importance and segmentation and overall critical importance are obtained,which is provides the theoretical method and basis for the reliability design,maintenance and troubleshooting of the hydraulic system of the loader.