Research On The Design Method For STEP-Compliant Open CNC Platform

Computer Numerical Control (CNC) technology plays a very important role in the development of manufacturing industry. Its development level is a very essential point in the manufacturing industry of a country. With the development of manufacturing, the drawbacks of traditional CNC system make it gradually unable to fulfill the demands. It can be clarified to three problems: open ability of software, open machining data model and open hardware platform. The open ability of software has two aspects: open software structure which can support secondary development and friendly software design method. The open machining data model is to use STEP-NC data model instead of ISO6983. Then the design and manufacturing information of upstream CAD/CAM units can be used to support intelligent autonomous functions. The open hardware platform means flexible reconfigurabilty of hardware platform. It ensures the flexibility and secondary development ability of the whole system at the hardware level. These three problems can be summarized to the problems of STEP-Compliant open CNC platform design method. In this dissertation, a deep research on the realization method of STEP-Compliant open CNC platform is put forward through the three problems above.First is the research on the CNC software structure and design method. In this dissertation, according to the reactive characteristic of the CNC system, an open CNC software design method, Function Separated Design (FSD) method and its structure was proposed based on Statecharts modeling theory. The implementing strategy is also given. With FSD method, CNC software is divided to Machining Interface, Function Description Data (FDD), Non-reactive Function Library and Event processor. Machining Interface provides an interface between software level and hardware level. It generates driving signal and reflects control data to the hardware level. FDD is a description of event processing rules. Non-reactive function library is the collection of complex calculation and data processing functions, which have non-reactive characteristics. They can be called according to the rules described in FDD. Event processor is driven by the events sent from Machine interface. It processes the events according to the rules described in FDD, and then sends the control data to Machine Interface.With this structure, CNC Functions are separated from the complex systems as the FDD and Non-reactive Function Library. After graphical Statecharts modeling and simulation of CNC functions, it can be converted to FDD automatically via FDD Generator, which is developed in this dissertation. This structure ensures the open ability of the software, and its friendly graphical design and simulation method is very convenient. The design burden can be eased and the user-level secondary development ability can be guaranteed.Second is the research on the open machining data model. In this dissertation, a research on the implementing method of STEP-NC under the framework of open software design method is put forward. First the working mode of intelligent STEP-Compliant CNC system is analyzed. Under the framework of Function Separated Design method, the STEP-Compliant intelligent CNC system structure is proposed and its working procedure is given. With this design, the test and upgrading of the STEP-NC related module can be done easily. A rapid development platform can be provided to fulfill the further development demands of STEP-Compliant CNC system.Third is the research on the hardware implementing platform. Recent years, because of the good consistency with upstream design and management unit, industrial Ethernet becomes a mainstream in fieldbus development. In this dissertation, EtherMC, which was developed by our research group, was improved and built as the hardware implementing platform. The topology and synchronization method of EtherMC was given. A tree-shape topology is adopted. Under this topology, the design specification of both Master and Slave node was given. Based on the design specifications, the implementation of high speed autonomous sub-system was given to solve the ultra-short period control problems in the fieldbus system. The configuration method based on the design specification was illustrated to ensure the flexibility and reconfigurability of the hardware platform. The flexibility and reconfigurability of the whole system was guaranteed at the hardware level.In order to verify the methods proposed above, a prototype is developed in this dissertation. In the realization of manual operation functions, the feasibility and validity of Function Separated Design method and hardware platform was proven. The open ability and shop-floor level secondary design ability of the system was proven by the secondary development of the previously designed manual operation functions (adding the fourth and fifth axis function). The implementation method of STEP-Compliant intelligent machine controller under the framework of Function Separated Design method was showed through an implementing demo of STEP-NC supported intelligent decision making module.The successful implementation of this research gives a solution to the problems existed in the CNC software, machining data model and hardware implementing platform. It provides an effective way to the STEP-Compliant open CNC platform implementation.