Key words: Pneumatic valve; Control; Fieldbus 1 Traditional Pneumatic Valve Control Means and Control System Pneumatic valve traditional switch control mainly adopts on-site control and remote control. In the case of low automation requirements, the local control method is mainly adopted. When the local control is performed, the technicians operate the relevant control keys to realize the on-off of the solenoid valve coil and the solenoid valve to change direction so that the cylinder starts to move, The final realization of the valve on or off. Technical staff to determine the valve switch state mainly depends on the switch button to determine the indicator light. With the continuous improvement of the automation level, the pneumatic valve control requires higher and higher automation to Chengdu, and the application of distant control means is gradually being widely used. In the early remote control, the technician mainly in the remote control room, or use some remote control equipment such as programmable controllers to control the transmission cable in the media, the remote control room valve switching control signal issued by Transmission cable can be worn to the remote pneumatic valve position, to achieve the valve switch control, technicians to determine the valve switch state and local operation consistent, but also rely on the switch button to determine the indicator light.
Traditional valve control system almost all one-on-one connection, point-to-point physical connection, the need to lay a large number of transmission cables and connecting equipment, and if the valve is very large, requires a lot of interface equipment, resulting in the cost of the entire valve system Costs rise sharply. In addition, the control signals are transmitted as standard analog signals, remote control for long-distance transmission, in the event of signal interference sources, it will lead to misleading or out of control valve, resulting in the stability and reliability of the control system greatly reduced. In addition, the control accuracy of the traditional control system is not high, information sharing is difficult to achieve, can not achieve long distance information transfer and so on. Although the subsequent DCS control system using layered structure to solve some of the shortcomings of one-to-one control, to achieve digital signal and analog signal mixing, but still can not completely solve the problems caused by the analog signal itself, still can cause the valve control exists Hidden trouble, and each manufacturer's products have their own characteristics, can not be achieved.
2 Fieldbus technology control system features Fieldbus technology is the rapid development of the last decade a new type of automation control technology, set of computers, communications technology, control technology as a whole, a direct result of the FCS (Field Control System) control system appear. Fieldbus technology to break the traditional one-on-one, point-to-point physical connection, is an industrial field level device communications digital revolution. The application of fieldbus technology makes the connection between valve control system and valve equipment control more simple and convenient. Compared with the traditional control signal system of on-site control and remote control, fieldbus-based valve control system has a very significant Features:
2.1 Simple structure, low development cost Fieldbus control system can achieve a little more control points, you can ensure that a bunch of lines connected to multiple devices, two-way transmission of digital signals. This connection breaks through the traditional point-to-point connection means, analog signal output problems, thereby saving a lot of wiring and space, reducing the wiring point, reducing interference factors, making the installation and maintenance is very convenient. Can only use two cables and four lines, can achieve more than one device interoperability.
2.2 has a very good stability using fieldbus technology for pneumatic valve control, the output signal transmitted are digital signals. Can effectively reduce the signal loss in the transformation process, greatly enhance the anti-interference ability, and because of the characteristics of the digital signal itself, the quality of the signal bed stability is also very high. At the same time, it also reduces the use of many auxiliary equipment, can effectively reduce the probability of human-controlled pneumatic valve failure.
2.3 simple operation, easy maintenance Fieldbus technology that uses a two-way communication, two-way signal transmission function, technicians not only in the control room on the pneumatic valve control valve site on the corresponding serial number calibration, parameter settings and functional configuration , But also real-time observed the working status of the site valve to facilitate the maintenance of equipment. At the same time you can also remote programming control and diagnostics, real-time detection of the valve status, in case of any problems, can self-diagnosis, remote control consultation through remote programming, troubleshooting.
3 Fieldbus-based pneumatic valve control case analysis Fieldbus technology is generally used for group-scale valve control, each group of valve called a valve. The following describes a research institute for material handling, the use of fieldbus technology to control the pneumatic valve example, the system diagram shown in Figure 1.
Figure 1 Fieldbus technology control system diagram shown in Figure 1, the main components of the control system structure including the PC total control machine, PLC and field bus technology, the PC total control machine using industrial control computer, PLC using Siemens S7-300 series, the communication link between the PC and PLC through the Ethernet, the media for the ultra-Category 5 UTP. Fieldbus technology is the use of PROFIBUS-DP protocol to connect PLC and local control equipment, the output rate of up to 12Mbps peak. On-site valve control relies on an intelligent valve island based on the FESTO CPV10 with a fieldbus interface and a feedback information module with local operating buttons, indicators and valve positions.
Combined with the effect of the system to control the pneumatic valve and the actual operation of the whole project, it can be found that the use of field bus technology has very significant advantages, which greatly reduces the number of transmission cables. In addition, other erection materials such as steel pipes, beam frames and profiles Also use the same amount of decline. The reduction in the use of engineering materials and equipment has led to shorter lead times and reduced overall manufacturing costs. At the same time debugging process is also very simple, as long as the open field bus communication, you can achieve pneumatic valve debugging. The control system in the control of signal transmission stability, anti-interference ability, there is no accidental control or pneumatic control valve out of control. Further strengthen the control instructions and functions, you can facilitate the commissioning and maintenance of process systems.
4 Conclusion Fieldbus technology used in pneumatic valve control, not all occasions are applicable to the general Fieldbus valve used in group control, can effectively reduce the number of wires to ensure the reliability of system operation, but for some small and scattered valves The occasion does not apply, because the cost of field bus interface much higher than ordinary cable. Therefore, the use of fieldbus control valve when the door needs to distinguish the occasion, choose the most economical control.
【references】
Wang Zhicheng, Yu Dong, Zhang Xiaohui, et al.Research on reliable communication mechanism of fieldbus in NC system [J] .Journal of Mechanical Engineering, 2011,47 (3): 152-158,165.
[2] Xiang Meigen, Xiang Xiaoming, Dai Xuexiang, etc .. Fieldbus and wireless control valve electric device design [J]. Fluid Machinery, 2013,41 (1): 53-54,72.
[3] Lin Xiaoyi. Field Controller in the field bus technology research and application [D]. Shanghai Jiao Tong University, 2007.
Zhao Mingnan, Yang Jintang, Xia Zhongyu, et al.Research on control method of intelligent valve positioner [J]. Machine Tool & Hydraulics, 2015, (2): 141-144.
[Editor: Julina]
High Voltage Generator,60Hz Generator,540kw Generator
Belten Mechanical & Electrical Manufacture Co., Ltd , http://www.tz-generator.com
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