Research on the latest generation of open networke

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Research on a new generation of open and networked numerical control system

open and networked numerical control system is the guarantee of realizing high-level digital equipment. Its core is open, that is, the independence of each module of the system and the operation platform, the interoperability between each module in the system, and the unity of man-machine interface and communication interface. The open architecture makes the CNC system have better versatility, flexibility, adaptability and expansibility, and develop towards intelligence and networking

the national numerical control system engineering technology research center and Huazhong Numerical Control Co., Ltd. have been committed to the research, development, production, promotion and application of the software and hardware architecture of the open numerical control system for many years. With the support of relevant national projects, the new generation of open and networked numerical control system HNC-21/22nd century star numerical control system was successfully developed and produced in 2003

research status of open and networked CNC system

the concept of "open architecture controller" first appeared around 1988. In 1989, the U.S. Department of defense began the "next generation workstation/machine tool controller NGC" program. In 1990, OASYS project was launched as a follow-up project of NGC plan. Since then, many research projects on open system architecture have been launched all over the world. Among them, the OMAC development plan jointly proposed by Ford, GM, chryler and other companies in the United States under the guidance of the NGC plan, the OSACA plan jointly launched by Germany, France, Italy and other countries in Europe in 1995, and the osec plan jointly proposed by 14 enterprises such as Toyota and Mitsubishi in Japan have entered the industrial trial stage and gradually embarked on the road of joint monopoly. In 2000, with the support of the State Economic and Trade Commission, domestic central China CNC, aviation CNC and other units put forward the technical specification of open numerical control system (ONC), formulated the technical standard of ONC system, and developed an open numerical control system verification prototype that basically conforms to the technical specification on the Linux system platform, which has certain open characteristics such as interoperability, simple shape, scalability and compatibility of removable samples

since the above research plan was launched, the architecture of CNC system has changed from closed to open, which has accelerated the development of CNC technology, improved the performance of CNC devices, and a number of open CNC systems with high precision and efficiency have emerged

the open architecture of CNC system provides conditions for its networking, and the networking of CNC system is a powerful embodiment of its openness

networking includes two aspects: internal network (Fieldbus Network) and external network

the so-called internal network refers to the field bus network connection between CNC Units and servo drive and i/o logic control units in the numerical control system: for the hardware of the numerical control system, openness mainly refers to that the computer, network, servo system and i/o logic control units should have unified interconnection standards to achieve interchangeability. In order to make the hardware of numerical control system interchangeable, at present, European CNC manufacturers widely use SERCOS (serial real-time communication system, a network interface protocol suitable for high-speed servo control, which became iec1491 international standard in 1995). As the interface with digital drive unit, fieldbus such as PROFIBUS is used as the interface with i/o logic control unit

the so-called external network refers to the network connection between the numerical control system and other control systems outside the system or external upper computers: with the development of modern communication technology and it industry, some famous numerical control system companies in the world have successively launched control systems with network integration ability and a certain level of intelligence, through which remote control and unmanned operation of equipment, transmission of remote processing programs (especially large-capacity programs) can be realized Technical services such as remote diagnosis and remote maintenance services, and improve the productivity of machine tools. For example, "it Plaza" of Okuma machine tool company in Japan, "cyber production center" of Mazak company in Japan, "open factory CNC" of GE Fanuc company and "open manufacturing environment" of Siemens company

characteristics of open and networked CNC systems

the main characteristics of open and networked CNC systems are shown in the portability of functional modules that can be used in different control systems; Modules with similar functions can be replaced with each other, and the scalability of software and hardware can be updated with technological progress; It has plug and play function, which can be easily and effectively reconfigured according to the demand change; Using standard i/o and network functions, it is easy to realize interoperability with other automation equipment interconnection

Table 1 lists the comparison between traditional special CNC system and open CNC system

Table 1 Comparison between traditional special CNC system and open CNC system

implementation scheme of hnc-21/22 open and networked CNC system

the technical route of hnc-21/22 Century Star CNC system platform is:

- it conforms to onc technical specifications and is open

- based on PC architecture, software replaces hardware, simplifies hardware, and is easy to produce, use, and maintain

- make full use of the existing research results of central China type I CNC system

- common hardware and cross platform software. The developed hardware platform PC embedded + FPGA hardware platform can be applied to three different software platforms: Dos based software platform 1, Linux based software platform 2, and windows based software platform 3

onc system introduction

referring to the definition of open system in IEEE and the definition of open control system in OSACA, ONC system defines its own open CNC system: the open CNC system is designed according to the open technical specifications to realize the interoperability between structural objects (software modules that realize functional units) in the CNC system, The application software realizes the independence from the running platform through ONC system application programming interface (oncapi), and the consistency of the human-machine interface and the interconnection interface with other systems

according to the above definition, according to the current development status of numerical control technology, onc adopts component technology and object-oriented analysis, design and programming technology, and adopts hierarchical structure technology to form the basic architecture of ONC system based on PC. As shown in Figure 1

Figure 1 hierarchical model diagram of ONC system reference architecture

the open level of onc open CNC system is reflected in:

Layer 1: configurable function, open human-machine interface, communication interface and protocol

layer 2: the control device allows the replacement and addition of specific modules in the NC core under a clear and fixed topology to meet the special requirements of users

the third layer: a "fully open" control device with completely variable topology. (not defined in the current standard)

hnc open The design idea of networked CNC system hardware platform

hnc-21/22 CNC system platform is:

- support the requirements of the first and second layers of onc

- retain the support for the third layer in the future

- the system is scalable and reduced from economical to high-end

- various applications can be developed through application interface to form different products

- connect various CNC components through device driver

- PC architecture can run PC The application software

hnc-21/22 CNC system hardware platform is based on PC architecture, as shown in Figure 2. The system uses standard interfaces of digital quantity, pulse quantity and analog quantity or field bus to connect all functional components. The system adopts networking connection mode with the outside, which can be integrated with cad/cam, fmc/fms and enterprise intranet to realize the networking of CNC system

Figure 2 hardware platform of hnc-21/22 open and networked CNC device

hnc-21/22 numerical control system makes full use of the powerful interface features of industrial PC, adopts 10.4/9.4 inch true color TF, the competitiveness of American parts manufacturers is weakened, t LCD screen, 8MB flash ROM (expandable to 72mb) program power-off storage, 16MB RAM (expandable to 64MB) processing buffer, equipped with hard disk and floppy disk, which can load and store a large number of processing programs, With huge program processing capacity, it can directly process G code programs up to 100MB without DNC, and easily realize machine tool connection by using Ethernet, RS232 and other interfaces

The switching value interface circuit of hnc-21/22, MCP and MDI keyboard interface circuit, feed shaft interface circuit and spindle interface circuit are all integrated on a "Century Star" motherboard. Its core device is Actel's FPGA chip. In order to meet the openness requirements of CNC devices, "Century Star" motherboard adopts dual FPGA design. An FPGA chip is responsible for controlling the switching value interface circuit, MCP, MDI keyboard interface circuit, spindle interface circuit, serial port servo driver interface circuit; Another FPGA chip is responsible for controlling the interface circuit of pulse servo drive device or stepping motor drive device, and the interface circuit of analog servo drive device. Two FPGA chips are controlled by Advantech industrial PC through PC104 bus. Using the flexibility of FPGA chip, without changing the hardware circuit, by changing the firmware of FPGA chip and the flexible combination of two FPGA chips, the following hnc-21/22 "Century Star" series CNC devices are constructed, so as to minimize the cost and improve the performance

- hnc-21/22a: it can be equipped with 4 analog servo drives

- hnc-21/22c: it can be equipped with 4 serial port servo drives

- hnc-21/22d: it can be equipped with 4 pulse servo drives or stepper motor drives

- hnc-21/22f: it can be equipped with 4 pulse servo drives or stepper motor drives, 4 analog servo drives or 4 serial port servo drives

hnc open and networked CNC system software platform

hnc-21/22 CNC device software structure is shown in Figure 3

Figure 3 software platform of hnc-21/22 CNC device

the part below the dotted line in the figure is called the underlying software, which is the software platform of hnc-21/22 CNC device. RTM module is a self-developed real-time multi task management module, which is responsible for the task management and scheduling of CNC device. Ncbios module is the basic input/output system of CNC device, which manages all external control objects of CNC device, including device driver management, position control, PLC control, interpolation calculation, internal monitoring, etc. Ncbios forms the common parts of NC into the NC kernel, provides standard interface functions, is open to users, adapts to users' personalized requirements, and is conducive to variety derivation and secondary development

The part above the dotted line is called application layer software (process layer software), which includes program, parameter setting, decoding program, PLC management, MDI, fault display and other functional modules related to user operation. For different numerical control devices, the difference of their functions is in this layer, or the increase and decrease of functions are carried out in this layer. All functional modules can exchange information with the bottom layer through ncbios, so that the functional modules of this layer are independent of the hardware of the system

when different control objects (such as machining center, milling machine, lathe, grinder, etc.) or different servo drives are used for the same control object, the hardware configuration of CNC device may be different. At this time, it is only necessary to select the corresponding driver to drive these hardware modules, without changing the underlying software and application software, reflecting good openness

when configuring the system, all boards used should be in g of ncbios (similar

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