With the development of 4G and 5G wireless networks, wireless network communication is stable and transmission speed is fast, which can fully meet the application requirements of industrial control for safe and reliable communication. Wireless network coverage is wide, easy to use, and traffic charges are also greatly reduced. As labor wages grow, the need for unattended and centralized monitoring increases significantly. Therefore, industrial equipment has realized the development of remote control through network data, and its stability and reliability can fully meet the traditional use requirements. PLC is a programmable logic controller that can be used in an industrial environment. Based on the reliability and stability of PLC equipment, it is relatively easy to upload and download programming, and has been widely used in the industrial control industry. This article introduces how the mainstream PLC realizes remote control through 4G network.
4G wireless remote communication method for mainstream PLC equipment
1、DTU
DTU is a communication method similar to 485 communication modbus protocol, and PLC realizes remote communication through GPRS wireless network. The configuration of DTU generally only supports 485 communication. The protocol is basically MODBUS and does not support the own protocols of PLCs of various brands. DTU basically belongs to communication. It uses the host computer system protocol to analyze the received data, and the data is sent during network transmission without handshake protocol. Vulnerable to packet loss due to network interference. DTU generally requires upper-layer software technicians to understand the modbus transmission protocol before it can be used. People who do the underlying hardware also need to convert the PLC protocol to the modbus protocol. Early DTU modules also need to configure network nodes. The requirements for technicians who use DTU are relatively high. In addition, there is also a transparent transmission protocol, which adopts polling communication method, so the transmission data cannot be too much, and the network delay is relatively large. Generally, the transmission cycle needs to be about 10S. Most of the DTUs are GPRS communications. With the large-scale commercialization of 4G\5G, the GPRS network is in danger of withdrawing from the network. However, DTU is cheap and requires high real-time and stability of data.
2. Industrial router (PLC remote control gateway)
Now the PLC remote control module adopts the PLC protocol network + cloud mode. The PLC remote control module is a hardware module with built-in PLC protocols of various brands. Like the touch screen, through the upper software configuration, select the industrial communication protocol, establish the mapping of variables and registers, and then download the configured program to the industrial gateway. The PLC remote control module is generally a system based on ARM. The PLC remote control module ZP4000 has integrated various commonly used industrial protocols. The communication setting method is the same as that of the touch screen and configuration software. It is very easy to use, and the general industrial control technicians are familiar with it. Protocol gateways generally have multiple communication ports such as RS485/232 and network ports, and are compatible with all mainstream brands of PLC devices on the market. After the PLC remote control module establishes communication with the PLC, it will process the variable data inside the processor and form a network communication protocol, and then use the 4G network to send to the cloud server or receive commands from the cloud server, and restore it to the PLC protocol in the internal processor .
The intelligent gateway with powerful functions in data processing will pack, compress and encrypt the data, adopt the security mode of non-transparent transmission, reduce the traffic consumption during data transmission, and implement the network handshake protocol and data retransmission mechanism, so as to ensure data security and reliable. Compression and packaging technology can send more data, and can speed up the data transmission, generally can achieve a transmission cycle within 1S. Due to its simple configuration and powerful functions, the PLC remote control module has been widely used in industrial control projects with relatively high data requirements.