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    Machine tools, especially CNC machine tools, are well-known for their role in various industries. In the design and manufacture of machine tools, designers have been striving to improve the performance and product appearance of machine tools. Compulsory course, a problem that troubles machine tool designers is the wiring of machine tools
    No matter how carefully the designer designs the appearance of the machine, once the pipeline is connected, everyone will find that the machine in front of him is like a "heavy patient" filled with tubes and wires. Another problem is the anti-interference and loose connection between the point-to-point control lines, power lines and signal lines. This
    It is also a headache for on-site electrical engineers. The emergence of fieldbus technology provides a good news for effectively solving these problems.
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<p> Main features of fieldbus </ p>
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    1. Openness of the system
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    The traditional control system is a self-enclosed system, which can only communicate externally through the serial port or parallel port of the workstation. In fieldbus technology, users can form products of different sizes into systems of random sizes according to their own needs and objects.
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    2. Maneuverability and reliability
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    When the same communication protocol is selected for the fieldbus, as long as the appropriate bus network card, socket and adapter are selected, information transmission and communication between interconnected devices and systems can be achieved, greatly reducing the workload of wiring and checking, and effectively improving control Reliability.
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<p> 3. Intelligent and functional autonomy of field devices </ p>
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    The signal transmission of the traditional CNC machine tool is the one-way transmission of the analog signal. The error generated by the signal in the transmission process is large, and the system is difficult to quickly determine the fault and operate with the fault. The field bus uses two-way digital communication to decentralize the functions of sensor measurement, compensation calculation, engineering quantity processing and control to the field equipment.
    The operating status of the device can be diagnosed at any time.
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<p> 4. Adaptability to the site environment </ p>
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    The field bus is designed to work in the field environment and can support twisted pair, coaxial cable, optical cable, radio frequency, infrared and power lines, etc. It has strong anti-interference ability and can use two-wire system to realize power transmission and communication , And can meet safety and explosion-proof requirements.
    Fieldbus makes the system more flexible
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    In short, in CNC machine tools, various controllers, actuators and sensors are connected by fieldbus, less cables, easy to lay, low cost, and more flexible system design, high signal transmission reliability and strong anti-interference ability . The control system of CNC machine tools based on fieldbus will gradually replace the original control system.
    The complex wiring harness will be replaced by the fieldbus. According to information, at present, China has successfully developed a bus-type CNC system applied to high-end CNC machine tools, with support for 32-axis 6-channel, 768IN / 512OUT switch control, and support users' secondary development.
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    The field bus system is a fully digitized, bidirectional, multi-station communication system between the field instruments and the input and output of the digital control system. It puts the dedicated microprocessor into the traditional measurement and control instruments, so that each of them has digital computing and digital communication capabilities. It uses twisted pairs that can be easily connected as a bus, which takes many
    A measurement and control instrument is connected into a network system, and according to an open and standardized communication protocol, data transmission and information exchange are realized among multiple computerized measurement and control equipment located on the site and between the field instrument and the remote monitoring computer, forming various An automatic control system adapted to actual needs.
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<p> 1.2 Advantages of fieldbus technology </ p>
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    Compared with the traditional DCS system, the field bus system from the design, installation, commissioning to normal production operation and maintenance, has demonstrated considerable superiority.
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    (1) Reduce the number of hardware and investment: smart devices scattered on the site can directly perform a variety of sensing, measurement, control, alarm and calculation functions, which can reduce the number of transmitters, no longer need a separate regulator, calculation Units, etc., no longer need some signal conditioning, conversion and other functional units.
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<p> (2) Saving installation costs: a pair of twisted pairs or a cable can usually be connected with multiple devices, so the amount of cables, terminals, slot boxes, and bridges is greatly reduced, and the workload of connection design and joint calibration Also greatly reduced. </ p>
<p> (3) Save maintenance costs: Fieldbus devices have the capability of self-diagnosis and simple fault handling; related diagnostic and maintenance information is sent to the control room through digital communication, and users can query the operation, diagnostic and maintenance information of all devices in order to Analyze the cause of the failure early and eliminate it quickly. </ p>
<p> (4) Users have a high degree of system integration initiative: users can freely choose equipment provided by different manufacturers to integrate the system. </ p>
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    (5) Improve the accuracy and reliability of the system: Compared with analog signals, it fundamentally improves the accuracy of measurement and control, reduces transmission errors, and improves the system's working reliability. This experimental system selects the temperature, pressure, flow and liquid level that are common in the thermal production process as the control object
    Profibus field bus control system. The structure and software configuration of the system are introduced below.
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<p> 2.1 System structure </ p>
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    It mainly includes fieldbus control network, liquid level console, flow console, pressure console, temperature console, host computer system and PLC, which is a typical fieldbus control system (FCS). A significant feature of fieldbus technology is its openness. It will be closed
    3. The dedicated system becomes an open, standard system. This allows products from different manufacturers to be interconnected, and also allows third-party software to be easily applied on different hardware platforms, which simplifies user development of the system. The following is a brief introduction.
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    2.2 Software configuration
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    The software design requires that it can intuitively display various states and parameters in process control, and establish appropriate alarm mechanisms for some parameters. The main screens of software design include process control, alarm monitoring, and trend screens.
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<p> 3.1 Application status of fieldbus </ p>
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    With the establishment of a large number of fieldbus demonstration projects and demonstration factories, fieldbus technology has passed the stage of enlightenment and publicity and entered the period of promotion and application. The conditions for enterprises to choose fieldbus control systems have gradually matured.
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    First, the competition between different fieldbus standards and manufacturers provides the conditions for users to choose system integration; secondly, some fieldbuses, such as FOUNDATION fieldbus, PROFIBUS, etc., have achieved good application performance and are widely recognized in specific fields.
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    3.2 Problems with fieldbus
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    First, multiple standards coexist, and no one standard can cover all application areas; second, the lack of interoperability between field buses of different standards; again, the current application is mainly small and medium-sized systems, the price advantage fails to reflect, it seems The traditional system overhead is still large; Finally, there is a security problem. When the bus is cut off, the system can
    Can produce unpredictable consequences. From the above introduction and the operation of the experimental system, it can be seen that the fieldbus has superior performance in system control and management. Therefore, it is foreseeable that the fieldbus control system will become the mainstream of industrial automation in the near future. Among them, thermal process control can start
    Play a good role in demonstration.
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