Key Technology Of Open CNC System Based On PC-SERCOS

Based on the "China manufacturing 2025",intelligent manufacturing is the main direction of China positioning manufacturing. The development of intelligent manufacturing cannot be realized without related intelligent algorithms and numerical control system. The traditional CNC system greatly restricted the development of intelligent manufacturing field because of the relatively closed structure which is not conducive to the user to change or upgrade the system according to the need of its own structure or processing.Therefore, the open CNC system plays a crucial role in intelligent manufacturing progress. At the same time, The open CNC system development of China's independent property rights is the effective way to shorten our manufacturing level with the advanced level in the world. According to this issue ,The key technology of the open CNC system is studied in this paper.For the open CNC system with high real-time and high performance requirements, the motion control interface which is the core interface should have the characteristics of high real-time and high precision synchronization.By analyzing the software and hardware structure of open CNC system, this paper selects the SERCOS interface as the motion control interface and the PC machine,universal Windows operating system and RTX real-time extension system as the software and hardware platform. At the same time, in accordance with the requirements of the SERCOS agreement, the presented system which abandons the other commercial software establishes the SERCOS service channel and and command channel under the SERCOS standard, thereby, the user can carry out data stream extraction in accordance with the own needs and the openness of the whole system can be improved.In view of the traditional NURBS algorithm in high speed and high precision machining along the single curve interpolation direction , there is no exact analytical relation between curve arc length and curvature constraint parameters. Furthermore, the feed speed is always subject to nonlinear change which makes the real-time calculation of the length of the curve and forecast of the deceleration point very difficult. The large calculating load may lead to the phenomenon of data hungry, which will affect the real-time performance of the whole system. To solve the above problems, this paper proposes a real-time interpolation algorithm with retrieved method. The algorithm does not depend on the accurate calculation of the length of the curve, using the method of forward and reverse synchronous interpolation. First of all, the algorithm take the reverse interpolation to the check point and other related information in the look-ahead module. Then, in the real-time module, the algorithm achieves the optimal interpolation which fit for the speed constraints by checking the speed of check point to determine whether to call reverse interpolation data or to continue forward interpolation. The algorithm does not need high equation and can guarantee to pass through the curvature extreme point and curve end point in a determined speed. Furthermore, the algorithm can also ensure the real-time. The presented experiment proved that the algorithm is simple, efficient, adaptable and real-time, which can meet the requirements of high speed and high precision in CNC machining.Post-processor is an important interface that transforms cutter location (CL)data into Numerical Control (NC) data. The data compensation in a five-axis machine is quite complex, because of a variety of the machine centers and the computerized numerical control (CNC) system. Since most work on the five-axis post-processor method has dealt primarily with the generation of NC code, this study breaks with tradition and introduces a post-processor with optimization tool radius compensation and a general machine configuration. Furthermore, a practical method for optimizing the NC code is presented that is based on further study of tool compensation and tool wear. The proposed post-processor is validated for various five-axis machine centers using a generalized kinematic model and various cutting tool models. The results of the verification tests showed that proposed post-processor approach can be used to accurately convert the cutter location into NC codes and the optimized NC code generated by the optimization tool radius compensation method demonstrates that the practical value of the proposed approach for improving processing quality and reducing the total machining time and cost.Using object-oriented technology and modularization, this paper develop the data processing module which is used for data storage and intelligent algorithm module which is used for intelligent analysis of the data. Taking the requirement of adjusting the experiment of application dynamic into consideration, this paper select the IDB file to develop the communication between HMI module and data processing module, which can greatly reduce the development cycle to facilitate data check and modify.For soft PLC with compilation principle of translation type, it will reduce the openness and flexibility of the CNC system. Based on compilation principle of interpretation type, progressive scanning method and keyword matching, this paper develop an interpretation running system which can pick the instruction list program line by line and loop execution. Through the experimental verification,the reliability of interpretation soft PLC function is proved and the the logic instruction function of open CNC system is achieved.