National CNC System Engineering Technology Research Center and Huazhong CNC Co., Ltd. have been committed to the R&D, production and promotion of open CNC system software and hardware architecture for many years. With the support of relevant national projects, it successfully developed and produced in 2003. A new generation of open, networked CNC system & 151; HNC-21 / 22 century star CNC system.
Research Status of Open and Networked CNC System
The concept of "Open Architecture Controller" first appeared around 1988. In 1989, the US Department of Defense began the "next generation workstation / machine tool controller NGC" program. In 1990, the OASYS project was launched as a follow-up project to the NGC program. Since then, many research projects on open system structures have been launched around the world. Among them, the United States' Ford, GM, and Chryler companies jointly proposed the OMAC development plan under the guidance of the NGC program, and the OSACA program jointly launched by Germany's German, French, and Italian countries in 1995 and Japan's Toyota. The OSEC plan jointly proposed by 14 companies such as Mitsubishi has entered the industrial trial stage and gradually embarked on the road of joint monopoly. In 2000, the domestic Huazhong CNC, aviation numerical control and other units, with the support of the State Economic and Trade Commission, proposed the open CNC system (ONC) technical specifications, formulated the ONC system technical standards, and developed a basic conformity on the Linux system platform. The technical specification of the open CNC system verification prototype has certain open features such as interoperability, displaceability, scalability and compatibility.
Since the start of the above research project, the CNC system architecture has been turned from closed to open, accelerating the development of numerical control technology, improving the performance of numerical control devices, and emerging a number of high-precision, high-efficiency open CNC systems.
The open architecture of the CNC system provides conditions for its network, and the network of the CNC system is a powerful manifestation of its openness.
Networking includes two aspects: an internal network (fieldbus network) and an external network.
The so-called internal network is the unit of CNC unit and servo drive and I/O logic control in the index control system. It is connected by fieldbus network: for CNC system hardware, the openness mainly refers to its computer, network, servo system and I/O logic. Units such as control should have uniform interconnection standards for interchangeability. In order to make the CNC system hardware interchangeable, European CNC manufacturers are currently using SERCOS (Serial Real-time Communication System, a network interface protocol suitable for high-speed servo control, which became the IEC1491 international standard in 1995). . As an interface to the digital drive unit, the fieldbus uses a fieldbus such as Profibus as an interface to the I/O logic control unit.
The so-called external network refers to the network system and other control systems outside the system or external host computer network connection: With the development of modern communication technology and IT industry, some famous CNC system companies in the world have launched networks with succession. Integrated control and a certain level of intelligent control system, through the network to achieve remote control and unmanned operation of equipment, remote processing procedures (especially large-capacity program) transmission, remote diagnosis and remote maintenance services and other technical services, and improve the machine tool productivity. For example, "IT plaza" (Information Technology Plaza, "IT Plaza") of Okuma Machine Tool Co., Ltd., "Cyber ​​Production Center" (CPC) of Japan Mazak Company, GE Fanuc "Open Factory CNC" (open factory CNC) and Siemens "Open Manufacturing Environment" (open manufacturing environment).
The characteristics of open and networked CNC systems
The main features of the open, networked CNC system are shown in the functional module can be used for the displaceability of different control systems; functional similar modules can be replaced with each other, and the scalability of software and hardware can be updated with the advancement of technology; Plug-and-play functionality, scalable for easy and efficient reconfiguration based on requirements; easy interoperability with other automation devices using standard I/O and networking capabilities.
Comparison between traditional special numerical control system and open numerical control system
| Comparison item | Traditional special CNC system | Open CNC system |
| System structure and scalability | Hardware-specific software is not easy to expand and contract | Hardware based PC Software based on a common operating system system can be scaled as needed |
| System maintainability | With the advancement of technology, it is necessary to develop and produce special hardware, which is difficult to adapt to the increasingly fierce demands of competition. | Keep up with PC technology development and easy to upgrade |
| Software development difficulty | The software is exclusive to CNC manufacturers, and it is difficult for machine tool factories and users to carry out secondary development to introduce original parts. | Using an open software platform, machine tool builders and users can develop their own software as needed. |
| Special purpose system development | It is not easy to develop special and special systems, it takes a lot of time | Easy to develop using open software platforms and high-level languages ​​such as C++ |
| Networking | Dedicated hardware and proprietary communication technology (method), high networking costs | Same as PC networking technology, high networking costs |
| PLC software | Must use the manufacturer-specific language, difficult to transplant, difficult to maintain | Use standard-compliant PLC, portability and easy development |
| interface | With a dedicated interface, only specific manufacturer products can be used | Easy to work with various servo, stepper motor drives and spindle motors using standardized interfaces |
| Program capacity | Dedicated RAM, usually only 128KB, High expansion costs, for large mold programs, Need to use DNC | General purpose RAM, memory above 4M, Can be expanded to 64MB, and can be configured with a hard disk, one-time transfer to a huge program |
HNC-21/22 open, networked CNC system implementation
The technical route of the HNC-21/22nd Century Star CNC system platform is:
It is open to the ONC technical specifications.
Based on the PC architecture, it is hard to soft, simplify hardware, and is easy to produce, use, and repair.
Make full use of the existing research results of the Huazhong I-type CNC system.
General hardware, software cross-platform. Developed hardware platform - PC embedded + FPGA hardware platform, can be applied to three different software platforms based on DOS software platform 1, LINUX-based software platform 2, based on WINDOWS software platform 3.
Introduction to the ONC system
Drawing on IEEE's definition of open systems and OSACA's definition of open control systems, the ONC system defines its own open CNC system: the open CNC system is designed according to open technical specifications to realize structural objects in the CNC system. Interoperability between functional modules (software modules), application software through the ONC system application programming interface (ONCAPI) to achieve independence from the operating platform, and the human-machine interface and the interconnection system with other systems to achieve consistency of the CNC system .
Figure 1 Hierarchical model diagram of the ONC system reference architecture
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According to the above definition, according to the current development status of numerical control technology, ONC adopts hierarchical structure technology while adopting component technology and object-oriented analysis, design and programming technology to form the basic architecture of ONC system based on PC. As shown in Figure 1.
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