| Numerical control technique is basis for advanced manufacturing technology, which covers mechanical manufacture, computer, automatic control, and sensor detection. Nowadays, the CNC system is moving toward hi-speed, hi-precise, intelligence, network, and composite. The more powerful in the CNC function, the larger computational complexity as well as the increasing software scale make the software reliability more and more important. The traditional software development process of CNC system involves in three stages. Firstly, the software is segmented into file, module and class. Then, all source code is compiled and linked. Finally, the massive application program can be obtained. Under the circumstances, CNC system was difficult to adapt oneself to the external environmental changes.During the working of CNC system, the input value of function module together with their running state may lead to the software failure, which is hard to detect and locate. Currently, the traditional method of fault detection is to set the threshold value in function module. If the parameter in function module is not to fall within the threshold value, it will indicate the occurrence of software failure. Dumping memory information and checking intermediate result are usually the methods of choice to locate software fault, which largely depends on intuition and experience of programmer. Therefore, it fails to achieve the rapid and automatic fault location. Moreover, the traditional method of repairing CNC system involves in the following stages. Firstly, the function module is modified or afresh by the maintainer. Then the application program can be obtained through all compiling and linking the source code. Finally the new application program can be deployed in the CNC system. This CNC system repairing method is static, closed and rather time-consuming.The aim of this study is to improve the software reliability of CNC system. Based on the research status of software diagnosis and CNC system, we carried out the study of component assembly, software fault detection, software fault location and software self-healing. The main research contents, methods and conclusions are shown as follows.(1) Open CNC system based on component: the architecture of open CNC system and COM component were established. The real-time of CNC system based on"windows + RTX"platform was analyzed, and tests of interrupt were done on PC computer, whose main frequency is 2.4 GHz and main memory is 512 M. The interrupt response time of RTX subsystem was delayed from 4μs to 15μs, which indicated that the"Windows + RTX"platform could meet the real-time request. The multi-object optimal module of component assembly was constructed, and the optimal assembly scheme was generated by genetic algorithm. In addition, the assembly experiment of interpolation components was carried out. The experiment result show that genetic algorithm have a capability of global searching, which enable to construct a high performance open CNC system simply and quickly.(2) On-line fault detection of CNC software: software fault prejudgment and pretreatment of CNC system was proposed. The experiment of interpolation based on ANN and fuzzy math was carried out on virtual axis machine tool, and interpolation performance was analyzed. The experiment result show that the interpolation based on ANN and fuzzy math can realize the fault prejudgment and pretreatment, which provide a new way for on-line fault detection of CNC software. The fault module of CNC system was built based on the support vector machine (SVM), which was compared with the conventional fault module of CNC system based on least square method. We find that the fault module of CNC system based on SVM have higher precision, and its consistency and correlation is better than that based on least square method, which can lay the foundation for objectively evaluating the reliability of CNC system.(3) Fault location of CNC software: the monitor of CNC system was constructed, and the fault location based on similar path set and BP ANN was proposed. During the CNC system working, the monitor can monitor and save the executive information of function module, such as input, output, running track, etc. If the software of CNC system fails, the process of fault location will execute the following steps: firstly, the control flow graph was generated according to the source code of software module, and the failed path was generated through analyzing the fault information recorded by monitor; then the similar path set was obtained by similar path algorithm, and the BP ANN was trained by learning sample that composed of similar paths and failed path; After that, the fault suspicious of directed edge was predicted by inputting virtual path into the BP ANN; finally, directed edges were arranged in order of fault suspicious, and the directed edge with largest fault suspicious was fault edge. The experiment on fault location of NURBS interpolation was carried out, and the obtained experiment result show that the proposed method enable to locate fault code quickly and accurately, which can avoid the rely on the experience of programmer and provide a new way to locate software fault automatically.(4) Software self-healing of CNC system: the repair of component was studied, and the component hot-swapping was proposed. We solved the technical problems in the process of component hot-swapping, such as transparent citation of object, state transition, request redirection, et al. The experiment about component hot-swapping of NURBS interpolation was carried out on Java2 platform. The experiment result show that the proposed method enables to replace components diametrically under the premise of normal working of CNC system, and it also provide a new theoretical basis for CNC system in adapting environmental changes and prolonging service life.
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