T-S Dynamic Fault Tree Analysis Method And Its Applications In Hydraulic System

The failure behavior of the hydraulic system is complex and varied,and fault tree analysis is one of method in reliability analysis of hydraulic system,fault tree is a causality logic diagram that like inverted tree,which can be used to describe failure behaviors of system.Dugan dynamic fault tree is composed of static subtree and dynamic subtree.The static subtree is traditional fault tree,which use traditional logic gates such as AND,OR gate and so on to describe static failure behaviors.The dynamic subtree uses dynamic logic gates such as the priority AND gate,the functional dependency gate,the sequence enforcing gate,the spare gate and so on to describe dynamic failure behaviors.However,to quantify the Dugan dynamic fault tree,we often resort to Markov chains,Monte Carlo method and so on.Compared with traditional fault tree,T-S fault tree can describe any combinational and multi-state static failure behaviors,but it still can not describe the system consisting of dynamic failure behaviors.To improve the ability to describe combination of any static and dynamic failure behaviors,T-S dynamic fault tree analysis method is proposed.First of all,T-S dynamic gate that describe static and dynamic logic relationship is defined and construction method of T-S dynamic gate rule including time state rule and event occurrence rule is proposed and T-S dynamic fault tree analysis and calculation method based on T-S dynamic gate input and output rules algorithm is proposed.The T-S dynamic fault tree considers the applicability of different description methods,such as event uncertainty,fault degree of muti-state system,and so on.Moreover,T-S dynamic gate rule can describe any combinational and multi-state static or dynamic failure behaviors,which infinitely approximate the failure behaviors of the real system.The feasibility of the proposed method is verified by comparing with Markov chains and Monte Carlo Methods solving Dugan dynamic fault tree.Secondly,to analysis the reliability of muti-state system,the muti-state T-S dynamic fault tree method is proposed.Using the T-S dynamic gate time state rule describe the relationship of muti-state system,and based on T-S dynamic gate input and output rules algorithm,we can get the probability of superior event.Comparing with the mesthod that analysis reliability problem of the muti-state system,such as T-S fault tree method and Bayesian network,and the feasibility the proposed method is verified.Moreover,on the basis of the above T-S dynamic fault tree,T-S dynamic fault tree importance algorithm is proposed,including probability importance,critical importance,risk performance value and risk reduction value in each time period and mission time.It provides basis for identifying system weakness and guiding system improvement.The importance lgorithm is compared with the traditional importance algorithm,which shows that the importance algorithm of the traditional fault tree is the special case of the T-S dynamic fault tree importance algorithm in the mission time.Finally,the reliability of the hydraulic system in the friction welding machine is analysised by using the T-S dynamic fault tree and importance analysis method.We can get the system's failure probability and importance of each time and mission time,which provides basis for identifying system weakness and guiding system improvement.