STEP-NC Intelligent CNC System Workflow Autonomous Collaboration is a type that has both autonomy and collaboration capabilities. It also has no choice for processing tasks, but can negotiate with the outside world through a collaborative mechanism, including physical layer collaboration, information sharing, and negotiation of processing tasks or scenarios. Fully intelligent is a type proposed for network manufacturing environments. As an autonomous agent in the network manufacturing environment, it can choose the processing method, and can also evaluate, negotiate and decide whether to accept the task. This article focuses on the fully intelligent STEP-NC CNC system. The main process flow of the fully intelligent STEP-NC numerical control system is as follows. The steps are as follows: Read the STEP-NC file based on the workflow of the STEP-NC intelligent CNC system (1). After the CNC system reads the STEP-NC file, it translates it into the internal format of the controller, such as C, C, Java, etc. (specifically determined by the system programming language, this article uses C). This process is called the interpretation of the STEP-NC program, and the corresponding functional module is called the interpreter.
(2) Information extraction. Extract the information of the file header and data segment (manufacturing information mainly includes feature information, process information, work plan, and geometric information).
(3) Process planning. After the information is extracted, the process planning is performed.
The process planning in the NC programming phase is usually offline planning or external planning. For the intelligent STEP-NC controller, only this basic site planning capability is not enough to realize dynamic planning, intelligent control and data backtracking. This paper proposes a three-level planning CNC machining mode for off-line planning, online planning and real-time planning.
STEP-NC Intelligent CNC System Architecture The modules of the STEP-NC CNC system are independent of each other and related to each other. They need to exchange information frequently and need to cooperate closely with each other. Multi-agent technology provides a good implementation strategy. A multi-agent system (MAS) is a collection of multiple computable agents, each of which is a physical or abstract entity that acts on itself and the environment, and with other agents. Communication. MAS emphasizes the ability of each Agent member to solve problems in cooperation, including task allocation and management, ways and methods of collaboration, conflict detection and resolution, resource allocation and management. In the multi-agent system theory, the coordination and cooperation between the agents is the key to solve the problem. The agents must exchange information through communication, including the target, intention, result and status. MAS is autonomous, distributed, and coordinated, and has self-organization, learning, and reasoning skills. Using MAS to solve practical application problems, it has strong robustness and reliability, and has high problem solving efficiency. MAS uses the communication, cooperation, coordination, scheduling, management and control between agents to express the structure, function and behavior characteristics of the actual system, providing a unified framework for various practical problems <6>.
Each functional module of the STEP-NC control system can form a separate agent. When they work together to accomplish the same target, they have the characteristics of multi-agent. While completing a single task, a single agent can work with multiple agents to achieve the overall goal. In addition, as a new generation machine tool controller, the architecture of STEP-NC intelligent controller must also consider the development trend of CNC technology. The system should meet the requirements of open CNC, adopt modular, software and open structure, guarantee its openness and reconfigurability from the architecture, so that developers or users can reconfigure it so that it does not need to be large. The changes can be adapted to a particular processing task or new control requirements. Compared with the special CNC hardware platform, the PC platform has the characteristics of reliable hardware, high integration, rich software resources, good development and debugging environment, fast software and hardware upgrade, short development cycle, convenient maintenance and expansion, high performance and price ratio. The CNC system laid the foundation. The STEP-NC intelligent CNC system should be based on the PC hardware and software environment. All functional modules should be implemented in software running on the PC platform and the most common operating system environments. The STEP-NC intelligent numerical control system should not only be regarded as an extension of the function of the traditional numerical control system. The decision-making and control tasks should be treated as a unified whole. From the operational mechanism and the basic algorithm, the system and the STEP-NC data model are guaranteed. Coordination. Combined with the above requirements, this paper proposes an architecture based on the multi-agent intelligent STEP-NC numerical control system, as shown. The entire system consists of 12 Agents with different functions.
The architecture of the multi-agent STEP-NC intelligent numerical control system (1) explains the Agent. The read STEP-NC file is converted into the internal format of the controller and stored in the database.
(2) Process Planning Agent. Realize feature conversion, resource selection and process conditions determination; determine the optimal plan and specific parameters according to the specific conditions of the controlled machine tool (process planning or optimization of each step, continuous process step) , step sorting and optimization of the overall plan, etc.).
(3) Tool path planning Agent. Generate tool path trajectory for each work step based on information such as machining characteristics, operation, and machining strategy.
(4) Simulation Agent. Using the geometric information and process information extracted from the STEP-NC machining program for system modeling and machining simulation; using feature-based modeling technology to build the system model, and implementing the dynamics of the machining process according to the work step simulation.
Implementation of the typical module The development of the above 12 functional Agent modules is the basis and key to realize the intelligent STEP-NC numerical control system. This paper only explains the Agent and Process Planning Agent as an example to illustrate the specific principles and methods of its implementation.
Explain that the AgentSTEP-NC NC program is a text file written according to ISO10303-21, which mainly includes the file header and data segment. The header of the file is a description of the management information, programming standards, etc. of the file. The data segment uses the project statement as the entry point to describe the specific geometric information and process information according to the ISO14649 standard. In order to facilitate the realization of the data processing function, the CNC system usually needs to translate it into an internal data format when reading the NC program. The process flow of the STEP-NC program interpretation (translation) based on the ROSEC early linkage method is as shown.
The upper dashed box shows the conversion process from EXPRESS mode to C class and data dictionary. Among them, Integrated_CNC_schema.exp is the AP-238 model (AIM), and the compiler creates a data dictionary in ROSE format and the definition of the corresponding C class. The lower dotted box indicates the development environment and tools. The middle dotted line box gives the basic flow of data translation. The STEP-NC file is read into the memory through the input and output module, and then the data extraction and conversion module extracts the information according to the SDAI method (not the standard SDAI) as needed. Memory files exist in the form of ROSE worksheets, which typically include headers, data segments, and system segments. The first two segments correspond to the header and data segments of the physical file respectively; the system segment is unique to the ROSE work order file, and mainly records the ROSE name index and related database information (obtained by the RoseDesign::system_section method). Therefore, the input and output in the field must meet the ROSE requirements.
Process Planning Agent In essence, replacing ISO6983 with STEP-NC will not affect the process of CNC machining. However, the differences in the data model determine that the implementation of the CNC machining process will make a big difference. The process problems in the traditional mode are basically realized through offline process planning; while the STEP-NC mode leaves the process planning problems related to the specific machine tool to be solved on site, so that the process planning problem runs through the entire CNC machining process. According to the specific characteristics of the intelligent STEP-NC numerical control system, this paper proposes the strategy of offline planning, online planning and real-time planning three-level process planning. The planning capability inside the STEP-NC CNC system is defined as on-site planning, and the process planning in the NC programming phase is offline planning or external planning. For the intelligent STEP-NC numerical control system, only this basic site planning capability is not enough for dynamic planning, intelligent control and data backtracking. To this end, this paper divides the site planning into online planning and real-time planning. The hierarchical planning model of STEP-NC intelligent CNC system is demonstrated.
STEP-NC intelligent CNC system hierarchical rule model offline planning includes the process from process analysis to generating STEP-NC data files. The main tasks can be summarized into three aspects: feature conversion, resource selection and process condition determination. Feature conversion refers to the conversion of design features to STEP-NC manufacturing features (including geometric features, process requirements, etc.); resource selection mainly refers to the selection of machine model and tool model; the determination of process conditions mainly refers to the basic process flow and basic technical requirements ( Determination of cutting method, cutting fluid, etc.). The final result of the offline planning is the STEP-NC NC program. The basic task of online planning is to refine the STEP-NC data and optimize it according to the specific conditions of the controlled machine. The final result of online planning is the optimal solution and specific parameters under current conditions. Generally, it can be understood as the planning of static tasks in the on-site planning. It is the responsibility of the planning agent in the intelligent STEP-NC controller, including the process planning or optimization of each step, the continuation of the steps, and the stepping of the steps. And optimization of the overall program. The main tasks of real-time planning include two aspects: First, the tool path and corresponding control commands (motion command, tool change command, cutting fluid switch command, etc.) are generated in real time before each step is executed; second, according to the operation status of the machine tool Adjust process parameters within a certain range. The former is generally solved by the control module (or processing agent); the latter is generally realized by the cooperation of the control module and the planning module, but can also be solved separately by the control module. The reason why the planning problem of STEP-NC controller is divided into online planning and real-time planning and the generated tool path is placed in the real-time planning stage, the main reason is: CNC machining has real-time requirements, so general planning problems should be started. Before the NC machining cycle; there are many unforeseen problems in CNC machining. The data cannot be decomposed into control codes prematurely. Otherwise, the dynamic programming, intelligent control and data backtracking of the CNC system will not be realized.
The realization of the prototype system is based on the architecture of the multi-agent STEP-NC intelligent CNC system. The research group is developing a prototype system based on STEP-NC intelligent CNC system. The whole system is developed under the integrated environment of VC and ST-Developer. PC platform. Some functional modules have been implemented, basically implementing the interpretation translation and field editing functions of the STEP-NC program, and providing a support platform for on-site process planning and simulation. Shows the editing environment of the NC program. In this environment, you can open, edit and save STEP-NC files, and you can write new STEP-NC programs directly in this environment, but the system does not yet provide complete on-site programming assistance. When the file is opened, the system can automatically check the legality from the file format and syntax. If legal, the system can display the geometry of the workpiece (implemented by ST-Viewer's automation technology).
NC program editing and graphical display interface 5 Conclusion Through the analysis of the process flow based on STEP-NC intelligent numerical control system, it is pointed out that the modules of STEP-NC numerical control system are independent and related to each other, and need to exchange information frequently. There is a need for close collaboration between each other in order to fulfill the functional requirements of the STEP-NC intelligent CNC system. Multi-agent technology provides a well-implemented strategy. In this paper, the architecture of multi-agent STEP-NC intelligent numerical control system is established. The whole system consists of 12 agents with different functions such as Agent, Process Planning Agent, Monitoring Agent and Decision Agent. Each agent cooperates with each other to realize various functions of the STEP-NC intelligent controller. Taking two typical modules in the system to explain Agent and process planning agent as an example, the specific methods of its implementation are expounded. According to the specific characteristics of the intelligent STEP-NC numerical control system, this paper proposes the strategy of offline planning, online planning and real-time planning three-level process planning. At present, the research based on STEP-NC intelligent numerical control system is still in its infancy in the international arena. Many problems have not yet been determined. This paper proposes a strategy and method for constructing intelligent STEP-NC numerical control system, which is only based on STEP-NC intelligent numerical control system. The research has made a preliminary exploration. Many issues have yet to be deepened.
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