Analysis of PLC automatic control system and communication technology

PLC is an important part of automatic control system, and its operation effect will have a direct impact on the stability of production equipment and system. In the field of field control, if the relevant automatic control structure fails, it is easy to cause the operation of pump body and roller body to be affected, or even cannot be used normally, and it is difficult to meet the specific production and operation requirements, This makes the fault more serious. In general, in the PLC control system, the relevant programming should be used in accordance with the specific standards and characteristics, the maintenance and design personnel are required to participate in it, and the corresponding design activities should be carried out in combination with the parameters and location of the system.

In the relevant control system, communication technology is the core part, and reasonable selection of relevant technology helps to improve the effect and level of automation control. For example, during the actual use of the control system, the application of automation technology belongs to the main technology in the production line, in which the CPU structure can carry out point-to-point and multi-point interface processing, and can also be used for fieldbus Provide good technical support, in this process, the application of related technology, need the reasonable application of free port protocol communication technology, in the specific production line communication scheme, also need to apply the advanced PPI protocol communication technology, can enhance the work effect of all aspects. Therefore, in the field of PLC automatic control, the application of communication technology is more important, we should pay enough attention to use communication technology in the correct way to improve the operation level of automatic control system.

Application of communication technology in PLC automatic control system

2.1 communication network system

With the development of computer network technology, the distribution distance, topology and composition structure of the network can be strictly divided into wide area type, local area type and interconnection type according to the specific network distribution characteristics and computer system. Combined with the topology structure, it can also be divided into star type, ring type and bus type, and attribute concentration It can be divided into simple types and multi-level complex types.

(1) The simple network usually takes the individual computer equipment as the main carrier, and takes one or many PLC with the same model as the main part in the station field. In the work of creating a simple type of distributed control system, the difficulty of operation is very low. The individual computer can become the system operation station, with display function, programming function, supervision and management function, etc. at the same time, in the field of PLC automatic control, it can also better complete the relevant control work. At this stage, a PLC equipment can be used as the master station system, while the rest of the models The same equipment belongs to the slave system, which can form a master-slave network.

(2) Multi level complex network system. At present, in the field of large-scale industrial production, this kind of network system is widely used. The use of relevant automation equipment during industrial production helps to promote its sustainable development and progress. Due to the differences of PLC system in industrial production, the application of different types of systems will form different network layers and functions. However, at present, many manufacturing enterprises will describe the relevant products in combination with the pyramid structure during the production period, and take the bottom structure as the main carrier to realize the control purpose of industrial production, while the middle type level is the main carrier, It can form the purpose of production management and optimization, and the upper structure is used to implement various measures of production management. Usually, during the actual operation of PLC automatic control system and related equipment, the three-level subnet and four level subnet are used to construct the composite type structure and system. In the development work, the interconnection is taken as the main reference basis, and the number of layers is usually seven. There are differences in the communication protocols used in different levels. In order to meet the different needs, we should correctly divide the network of each level and carry out targeted management and control activities.

2.2 communication protocol system

In order to ensure that each subject of PLC automatic control can communicate and exchange reasonably, advanced network communication protocol should be used reasonably in the design process, so as to avoid the information interaction problems in the communication process and improve the smoothness of data transmission and circulation. For the communication protocol, it can be used as the specific content of the relevant network communication during the actual application. In short, it is to put forward the specific agreement of combination. In the case of improving the communication function and information transfer function, it can correctly identify the information, make the acquisition and interaction of various data meet the requirements of synchronization, and real-time detect whether there is error information in the system In order to improve the timeliness and accuracy of all kinds of information. In general, in PLC automatic control, the use of related communication protocols mainly includes common types and special types of related enterprises.

In the operation of the network between the middle layer and the bottom layer, the communication protocols used by enterprises are usually used. Among them, the bottom layer network needs to bear the specific control commands and data commands during the information exchange period. Although the amount of information is small, it has high requirements for real-time. For enterprise specific protocols, usually the application type, link type and physical type are the main layers, and the number of layers is small. Therefore, the transmission efficiency of information and data is high. At the same time, for enterprise specific protocols, USS and other point-to-point interfaces are more important. At present, the main communication protocol used in PLC network is the high-level type of subnet structure, which can carry out reasonable connection processing for various networks, and achieve the purpose of mutual management with other tasks. There is a certain difference between PLC network and commercial network.

2.3 information error detection and correction

During the operation of the relevant information system, it has a high error checking and correction performance, so it will involve a lot of error control performance factors during the use, which also belongs to the standard part of the relevant communication system that needs to be focused on during the application period. In the link of data information transmission, the detection and correction of information errors requires the automation of the system Error recognition, and then targeted correction, remove the part of the error, to achieve a good purpose of error correction. In general, in the field of traditional communication control, parity check technology and square array code technology are mainly used for error detection. In the advanced type of communication control work, advanced CRC technology can be used to achieve the purpose of error checking. The application of this method can highlight all the automation performance, improve the system operation efficiency and accuracy in the process of error detection, and achieve good management and coordination goals.

2.4 PROFIBUS communication technology

For the communication system, its openness is very obvious. Therefore, in some fields, it has high application value. Among them, fieldbus is an important part, which can achieve the centralized processing goal during the application period. At the same time, in terms of automation related features, the improvement effect is more obvious, which has high use value.

The importance of communication technology in PLC automation

3.1 it is helpful to deal with the switching value correctly

For PLC, the speed is very fast during the actual operation, the wiring mode is very simple, the maintenance work is convenient, the soft contact is more complex, and the reliability is also very good. It can not only improve the quality of production control work, but also save human resources and time resources, and prevent the problems of circuit complexity and not easy to modify during the operation of the system. However, in the actual operation period, there are often problems of information interaction, which can not better obtain the operation data information of the relevant system, seriously affecting the reasonable implementation and strict implementation of all aspects of work. In which the application of communication technology can form an advanced communication mode, enhance the interaction effect of various data information, form a good operation and support role of various equipment and systems, and ensure that the use of various working methods and technical methods meet the requirements.

3.2 realize the control purpose of analog quantity

3.3 contribute to centralized control

For PLC, it belongs to the automatic control system, the application of communication technology can better achieve the purpose of centralized management. For example: with the help of communication technology, we can fully understand whether there is logic detection error in the system, and each equipment can complete the synchronous cycle task of machine tool equipment within the standard time. In the detection process, we start the timer, input various data information into it, and obtain the information of automatic shutdown or start alarm combined with the specific situation . During this period, the start time of the timer is a little late. During various signal input periods, once the equipment has a fault problem, the logic of the signal will be destroyed. The communication technology can be used for rectification and improvement, so as to improve the application level of PLC automatic technology and ensure the real-time and effective acquisition of data information.

Editor in charge: yyx

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