Fault Tree Analysis Of CNC Machine Electrical Control And Drive System

Computer numerical control(CNC) machine, which is a highly integrated product,is constructed by Mechanics, Electronics, Hydraulics, and many other disciplines and serves as a “machine tool” in the equipment manufacturing industry. The electrical control and drive system is a key system of CNC machine, and it always plays an important role in implementing its function. This system is mainly used to control the operation of each component of CNC machine and coordinate to complete processing tasks. There is no doubt that it should be given a higher priority before CNC machine industry has made its technical breakthrough. Therefore, conducting reliability analysis for this system is a prerequisite to improve product quality, enhance the competitiveness of enterprises and accelerate the development of CNC machine industry from home and abroad.In terms of large systems, fault tree analysis(FTA) technology is an effective method for reliability and safety analysis. With the continued expansion of its application areas, dynamic fault tree(DFT), T-S fuzzy fault tree(T-S FFT) and other fault trees which are all major trends in the development of the fault tree analysis method have been proposed. This thesis bases on the research status of domestic and foreign machine tool’s reliability. By taking the important units of certain CNC machine electrical control and drive system as the research objects, FTA technology and Bayesian network(BN) are both used to carry out reliability analysis. The core content of this thesis mainly includes:(a) FT Modeling. By taking complexity, multiple states, fuzziness, dynamic and any other characteristics of the system into consideration, we choose the key units of certain CNC machine electric control and drive system which named “main drive control system” and “feed control system” as the research objects and combine their functional block diagram(FBD) with reliability block diagram(RBD) to select the appropriate top event to build fault tree, which consists of the static fault tree(ordinary static fault tree, fault tree with common cause failure and T-S fuzzy fault tree) and the dynamic fault tree.(b) FT Qualitative and Quantitative Analysis. By making a brief qualitative analysis for different kinds of fault tree of each unit, the key factors leading to failure of each unit could be found. Then combine the standard Bayesian network, the multi-state Bayesian network and the discrete-time Bayesian network, all kinds of fault trees can be converted to their corresponding Bayesian networks. Finally, quantitative analysis, which devotes to calculate the probability of top event and evaluate the importance of each basic event, can be conducted by using MATLAB Bayesian network toolbox(BNT).This thesis completed the reliability analysis of processing control part of CNC machine electrical control and drive system. By analyzing, the probability of this part and its key units in each state, as well as their main failure modes and causes were obtained. These all lay the foundation for the implementation of follow-up research on reliability.