Research And Application Of CNC System Software Reliability And Evaluation Method

CNC machine tool is the most important basic machinery for equipment manufacturing industry.Its overall performance is largely detemined by the performance level of CNC system.In recent years,with the rapid development of machine tool industry of China,the performance of domestic CNC system has also been greatly improved,especially in terms of functionality and accuracy.It has been gradually approaching the international advanced level.However,relevant statistics show that most of our high-end CNC systems still rely on imports.The reason is mainly due to the wide gap between domestic system and abroad in reliability.Therefore,improving the reliability of domestic CNC system has become the key to the rapid development of equipment manufacturing industry of China.As continuous development and improvement in hardware technology,hardware platform has been very mature,and its reliability is relatively high.Software failure has become a main cause of fault of the entire system.Since the machining precision and speed and other technical indicators continue to increase,CNC system software is developing large scale and complex.As a result,the probability of the occurrence of software failure multiplied.Therefore,the study of CNC system software reliability theory and related technology becomes very important.This paper combines work in National Science and Technology Major Project “the industrialization of standard CNC system and the research and development of the special gear machine tool CNC system”,and Anhui Province's Special Funds Project for independent innovation “high-performance intelligent CNC system development”.CNC software reliability has been studied comprehensively and systematically.The main reaserch work as follows:(1)A CNC system software architecture model is established.The model is mainly divided into function layer,program layer and component layer.A CNC system software reliability allocation model is established based on AHP and complexity of components.Under the constraints of minimum component reliability and highest R&D expenses,the reliability allocation model is established to maximize usability of the entire system and assign reliability to each program.And finally assign reliability to each component with the reliability of the program as a general indicator and the complexity as a factor.The experimental results show that the model can assign the CNC system software reliability to each component reasonably and provide the guidance for the development of individual components.(2)A comprehensive software failure modes and effects analysis(FMEA)to the GSK-HFUT gear hobbing CNC system is conducted.The purpose is to find the reliability weak point of the software system,and take the improvement procedures to reduce the probability of the occurrence of the failure.System-level software FMEA and detailed-level software FMEA are used in the gear hobbing CNC system.The results can give guidance for the improving of software reliability of the system and the development of new type system.(3)The method of CNC system software defects self-localization is studied,and the model of code defect is established.The method may help researchers locate defects after software failure occurred quickly and accurately.An extensive layer is added into the CNC system software architecture to keep track of software execution information.Control flow graph is created.A similar path set is generated according to the control flow graph.A CNC system software code defect suspicion degree classifier is established to calculate suspicion degree of directed edges in failure path.The experimental results show that the method is feasible.It can effectively improve troubleshooting efficiency and reduce mean time to restoration(MTTR)of CNC system,thereby increasing the availability of CNC system.(4)A software reliability evaluation system and a cardinal multi-attribute decision making model are established.A comprehensive quantitative evaluation is performed based on 6 evaluation indexes,include the fitting ability and the predictive capacity.Combined with multi-objective decision making method,the evaluation and selection of software reliability models are conducted.Three kinds of solving methods of decision making model are discussed.The experimental results show that the method of using multi-attribute decision model to select the best software reliability model is feasible.(5)A software reliablity evaluation and prediction model of CNC system is established.The accuracy of model predictions is improved by a weighted combination modeling method.A dynamic weight adjustment algorithm is proposed,and a dynamic weighted combination model is established.The comparison experiments show that the model has lower fitting error than existing model.The model is successfully applied to the GSK-HFUT gear hobbing CNC system.The experimental results show that this modeling method is effective,feasible and universal.It has a very high practical value.The prediction results have very important significance for managers to make correct decision.