Research On Reliability Analysis Of The Hydraulic System Of A Heavy Cnc Machine Tool

Hydraulic systems are widely used in aviation, aerospace, metallurgical machinery, engineering machinery, etc. In this paper, the hydraulic system of a CNC machine is taken as the research object. After analyzing the structure and principles of the hydraulic system, T-S fuzzy fault tree and Bayesian network are applied to study the system reliability.Firstly, the structure and working principle of hydraulic system of a CNC machine are researched thoroughly. After statistical analysis of the existing maintenance records, the hydraulic circle with high failure frequency is determined and is selected as the research object. The common failure modes failure causes and maintenance measures of the components and hydraulic system are analyzed. After analyzing the logical relationships among components of the system, the reliability block diagrams for five hydraulic circuits, i.e. precision compensation circuit, static pressure circuit, clamping circuit, lubrication circuit and scavenge oil circuit are established.Secondly, the T-S fuzzy fault tree analysis is conducted and is compared with the existing traditional fault tree analysis method. Based on the thorough analysis of the hydraulic system, this paper focuses on precision compensation circuit, and uses T-S fuzzy fault tree to analyze the hydraulic system in-depth. The fault tree modeling, qualitative analysis and quantitative analysis of hydraulic system are also carried out in this paper. And then the fault search strategy based on T-S importance, search cost and the value of heuristic information is studied.Finally, based on T-S fuzzy fault tree, reliability analysis of two-state and multi-state system for Bayesian network, a method to deal with T-S fuzzy fault tree by using Bayesian networks is put forward. To solve Bayesian network construction problems, this paper studies the transformation method for T-S fuzzy fault tree to Bayesian networks. Then the algorithms of comparing Bayesian network with T-S fuzzy fault tree and Bayesian condition probability and T-S importance are finished. It is proved that the proposed method is available. Bayesian network is used to research reliability of precision compensation circuit.Through research and analysis, this paper points out the importance of each component in precision compensation circuit. And then the search order for each component which can be used as a reference to improve the reliability of the precision compensation circuit.