Fault Tree Analysis Of The CNC System On Machine Tool And FTA Software Development

The fault tree analysis (FTA) of the machine tool numerical control system serves as an important part of the reliability research of the system. In order to find the reasons of the machine tool numerical control system in its actual generation, thus to maintain, improve and enhance its reliability, a systematic and profound FTA for machine tool NC system is a necessity.In order to more conveniently and easily popularize FTA method in the reliability analysis of machine tool NC system and improve the reliability level of our country’s machine tool NC system, this thesis develops a piece of software which can be applied to the FTA of machine tool NC system. This software can meet the demands of different users, who have various purposes and different professional knowledge through reducing the professional requirement for partial users. By adopting the machine tool NC system data of the data base storage, the author builds the cause-and-effect model for each level or for the components of the system in the interface of the software according to the structure and levels of the system. The mini fault tree will be formed by invoking the model, and the fault tree of the object system will be finally established after adding this mini fault trees into the systematic fault tree from top to bottom.This thesis also expounds the fundamental principles of the fault tree computer-aided analysis, and gets the cut set and the mini cut set of the machine tool NC system fault tree by adopting descending method and prime method. Due to the compatibility the events among the fault tree, the calculation will increase exponentially with the expansion of the fault tree scale in the quantitative analysis; therefore, the end-stage disjoint analysis is used in the mini cut sets, in which the State-space concept is introduced and defined the concept of cube. By applying recursive sharp method, the end-stage disjoint calculation is realized, and finally the unreliability of the machine tool NC system is achieved by using the disjoint results and the data in the data base.