Reliablity Analysis Of Hydraulic System Based On Convex Set T-S Dynamic Fault Tree

Hydraulic system is widely applied to various fields of national economy,and it is the core part of control and power transmission of mechanical products.Hydraulic system continuously to the development of large-scale,high-tech and complicated,it is difficult to obtain the accurate distribution of the failure probability of the hydraulic components,the failure probability of components and the failure relationship of component change with time which will lead to the problems of uncertainty and dynamic sequence of the hydraulic system failure.In order to solve these two problems,the interval convex set model and multi-ellipsoid convex set model and T-S dynamic fault tree analysis method are combined,reliability analysis method based on T-S dynamic fault tree analysis method and importance degree and sensitivity algorithm of convex set is proposed which is applied in the lifting hydraulic system of tower crane and provides a theoretical basis for improving its reliability.Firstly,aiming at the problems of uncertainty and dynamic sequence of hydraulic system,reliability analysis method based on T-S dynamic fault tree analysis method of convex set is proposed.The First is the interval convex T-S dynamic fault tree analysis method to describe the failure probability of hydraulic components with interval variables,and interval variables is obtained under the condition of the extreme value that is relatively conservative.The second is the multi ellipsoid convex set T-S dynamic fault tree analysis method to describe the failure probability of the hydraulic components with the ellipsoid variables,and ellipsoid variables effectively constraint interval variables,describing the failure probability of component failure probability objectively.Then,the T-S dynamic fault tree analysis method is used to obtain the failure probability of convex set in each time period and the mission time,which provide basis for reliability analysis of the system.Through the example analysis,the feasibility of the T-S dynamic fault tree analysis method of two convex set is verified,and the result that the T-S dynamic fault tree analysis method of multi-ellipsoid convex model is is closer to the engineering practice.Secondly,as an important quantitative of fault tree analysis method,importance algorithm reflects the importance of the basic events or cut sets of the system.Based on the T-S dynamic fault tree analysis method of two convex set,importance degree and sensitivity algorithm of T-S dynamic fault tree of two convex set is proposed.The calculation method of the probability importance degree of convex set,the critical importance degree of convex set,the sensitivity of convex set of the basic event are given,and the solving method of T-S dynamic bayesian network is given.Through comparative analysis of example,the effectiveness of the importance degree and sensitivity algorithm of T-S dynamic fault tree of two convex set is verified.Finally,luffing tower crane is a high-risk outdoor specialized facility,the reliability of lifting hydraulic system has a direct impact on the safety of tower crane,reliability analysis is conducted on the lifting hydraulic system of tower crane by utilizing the method above which obtains the probability of convex set of hydraulic system failure,the probability importance degree of convex set,the critical importance degree interval of convex set and the sensitivity of convex set of the basic event,which provide the basis for discovery the vulnerable points of system,enhancing reliability,fault diagnosis and reliability maintenance.Considering the results of the analysis of the two methods,the correctness of the T-S dynamic fault tree analysis method and importance degree and sensitivity algorithm of multi-ellipsoid convex set is verified.