The GPRS remote wireless measurement and control method solves many problems such as high line laying costs and inconvenient large-area agricultural possibility management, and technically provides the realization of precision agriculture. There are currently relatively few mature applications for water- and fertilizer-saving precision agricultural control systems for agricultural irrigation and fertilization according to crop needs. At the same time, the problem of unreasonable irrigation and fertilization is still prominent, which not only leads to low water and fertilizer utilization efficiency, but also aggravates the waste of resources and environmental pollution. This article builds an overall framework system based on the Internet and a highly integrated and intelligent agricultural irrigation and fertilization intelligent control system. During the agricultural irrigation process, through real-time collection and fuzzy evaluation of crop environmental information and nutrient information, the system can then be used according to the set crop needs. Water regimes and fertilization recipes guide fertigation. As our country is facing a severe shortage of water resources and the serious harm caused by excessive fertilization, it is of great economic significance to realize intelligent control and management of water transfer with fertilizers, water promotion with fertilizers, precise irrigation, and precise fertilization. and social benefits.
1. System composition
The system is mainly composed of management room control level, remote web page monitoring level, irrigation area on-site control level, mobile phone text message control, etc. The on-site control level of the irrigation area sends the crop environment and soil nutrients information of the irrigation area to the management-level configuration software through the DTU module. The monitoring configuration software participates in decision-making to determine whether to open the irrigation valve and fertilization valve, thereby achieving water demand according to the crops. Fertilization requires irrigation and fertilization. At the same time, it can also automatically measure pipeline flow, making it convenient for water conservancy workers to perform relevant calculations and analyses. The water pump room management level can also start and stop the water pump according to the water level of the high-level pool in the irrigation area, and automatically adjust the pipe network pressure through the frequency converter. The system can also flexibly configure different valve groups, different times, different irrigation amounts, and different fertilization formulas. To adapt to irrigation and fertilization of various crops. Figure 1 is a block diagram of the system.
2. Selection and configuration of main parts
2.1 System programming software Online debugging. The main way for the measurement and control center software to establish communication with XLT is through the RS485 to RS232 conversion module. XLT can also communicate through USB port, Ethernet, CAN bus, modem and other methods. It can be configured as digital input, high-number counter input, analog input, digital output, pulse width pulse modulation output, analog output and other methods, which greatly facilitates users’ secondary development. The communication between the measurement and control center software and the configuration software is carried out through the serial port. If the measurement and control center software and the configuration software are installed on the same computer, the computer must have two hardware serial ports (or two virtual serial ports) so that the measurement and control center software and the configuration software each occupy one serial port for communication. . To implement two virtual serial ports on the same computer, this article uses virtual serial port software (such as Virtual SerialPort Driver 6.O) to add a pair of virtual serial ports COM2 and COM 3 that can communicate with each other.
2.2 Selection of controller This article uses HORNER company’s touch OCSXLT102, which has built-in I/O including switch value, analog value and high-speed I/O. For machine control, high-speed I/O can provide counting, frequency measurement , PWM generation and pulse output. It can be easily applied to the process control of high-precision input of thermocouple, RTD, 4~2OmA, /~100mV and 0H10V signals. XLT integrates two standard RS-232/RS-485 serial ports and CAN network interfaces. It can be equipped with built-in 57.6k telephone modem card, wireless communication card and GPRS/GSM communication card. The working voltage is 12V. It has the following advantages: ① High-quality graphic LCD or touch screen display, which better displays the production process and the process status of the equipment; ② Complex graphic display functions, including trend charts, bar graphs, instrument displays and animation functions; ③ Powerful control Ability to support floating point operations, advanced mathematical operations, multi -loop PID auto-tuning, string operations, etc.; ④ Large-capacity removable storage function, up to 2G, which can store programs, historical data records, screenshots; ⑤ CsCAN communication port (Optional) Remote I/O can be easily expanded, or connected to other controllers and PCs; ⑥ Built-in 2 serial ports to facilitate communication with frequency converters and other PLCs or peripheral serial devices;
In addition to the built-in Vo, XLT102 can also connect to SmartStixI/O and SmartModI/O modules. SmartStixI/0 is a high-speed remote module that can give full play to the advantages of distributed control through CsCAN; while SmartModI/ O is connected to XL through RTU/Modbus, this type of module has fewer points and is cost-effective.
3. Communication between measurement and control center software and GPRSRTU
3.1 Introduction to communication protocol GPRS has the advantages of fast communication speed, low communication cost, and flexible networking. GPRSDTU has TCP/IP protocol conversion function and does not require users to provide TCP/IP support. It is applicable to all terminal devices with serial ports, realizes wireless and transparent transmission of data information through the GPRS network platform, and provides GPRS communication capabilities for terminal devices that do not have TCP/IP protocol processing. GPRSRTU sends data packets to the matching measurement and control center software on the remote computer through the GPRS wireless network. The measurement and control center software organizes the data packets into the Modbus-RTU protocol format and sends them to the configuration software (or other application software) through the serial port (or virtual serial port) on the computer for use.
This protocol follows the Modbus-RTU protocol standard. The configuration software acts as a client (master station) to send read/write command frames, and the measurement and control center software acts as a server (slave station) to send response frames. Since the software of the measurement and control center can connect to multiple GPRSRTU terminals, and the RS485 interface of each GPRSRTU terminal can also connect to multiple external devices, the measurement and control center has a one-to-many relationship with the GPRSRTU terminal, and the GPRSRTU terminal and the external device are also a pair. Many relationships. By segmenting the address code (1-247), it is determined whether the GPRSRTU terminal or the device connected to the terminal is operated. This protocol uses the address code of (1-200) as the address code of the terminal, and the address code of (201-247) As the address code of the external device of the terminal RS485 port. When issuing read and write instructions to an external device, you must first specify which GPRS RTU terminal external device you want to operate. This is done by first sending a GPRSRTU terminal operation command (address code between 1-200) to determine which terminal is currently being operated. , and then send the operation command of the external device (address code in 201-247).
Depending on the model, the GPRSRTU terminal contains different numbers of analog inputs, switch inputs, relay outputs and expansion modules (such as a temperature sensor). The measurement and control center software can be connected to multiple terminals at the same time. The basic communication byte data format is: 1 start bit, 8 bits of data, low bit first, no parity bit, 1 stop bit. The default serial port settings are: baud rate 9 600bps, 1 start bit, 8 data bits, no parity, 1 stop bit. That is: 9600, N, 8, 1. If you want to use other serial port parameters, you can set them in the supporting measurement and control center software.
3.2 Port mapping DTU modules can only communicate with each other between data center servers on the public network IP. However, the data center server where the user is located is usually connected to the public network IP through a router. It is in the LAN and cannot communicate with the public network server. Direct communication between DTU modules must be achieved using port mapping technology.
This article mainly implements port mapping through routers. The public IP obtained by the router is 60.212.57.124. The LAN IP of the data monitoring center server is: 192.168.3.11. Under the forwarding rules of the router, a virtual server is used for port mapping. When the port mapping is done on the router, the mapping relationship between the WAN server port and the LAN network server is defined. All access to the WAN service port will be is redirected to the LAN web server specified by IP address. Then all data sent to port 8080 on the GPRS network will be forwarded to the data monitoring center server 192.168.3.11. In the same way, the data monitoring center server 192.168.3.11 can also send data to the public network computer 60.212.57.124.
3.3 Application of dynamic domain name and peanut shell software In general applications, users rarely have fixed or dedicated lines to access the GPRS network. When the data center server uses ADSL to directly dial up the Internet, it obtains the dynamic IP of the public network ; GPRS network A fixed IP must be used to transmit data. Therefore, under these conditions, to realize the interconnection between GPRS and the data center server, dynamic domain name resolution technology must be used. At present, most of the dynamic IP addresses on the public network are fixed by using “Peanut Shell” software. It is a completely free dynamic domain name resolution service client software. The Peanut Shell dynamic domain name resolution system is the dynamic domain name service system with the largest number of users in the world . Oray distinguishes the dynamic domain name service system according to the service user group and application scope, and provides a variety of value-added services for users of different levels: specify the source of logging in to the Peanut Shell server Port (SourcePort), supports multi-network card users to specify network cards to access the INTERNET, supports multiple different operator service line selections, dynamic resolution service monitoring and IP maintenance. When the user downloads and successfully installs the dynamic domain name client, and then successfully logs in with your registered Oray passport, all domain names under the passport that activate the peanut shell service will be bound to the machine’s public IP. You can use the peanut shell dynamic domain name to establish a remote access application for the host, so that Internet users can find the network address of your machine through the domain name anytime and anywhere.
4. PC configuration software development
4.1 Development of system software The system host computer is mainly composed of PCs with good network conditions. The PCs need to run the measurement and control center software, KingView 6.55, and SQLSERVER database. KingView 6.55 is the mainstream monitoring and configuration software in China and is a special software for data acquisition and process control. It has rich human-machine interface, visual operation interface, rich picture gallery, simple and practical, powerful network communication capability, screen refresh capability and script execution performance. At the same time, it also has configuration interfaces for real-time data, historical data, alarm data, security users, variable objects, device objects, user objects, etc. Has good maintainability and customizability. Can support simultaneous access by more than 200 clients. A large number of graphic elements and gallery elves are provided, and users can create their own gallery elves according to their needs. Functions such as historical curves, reports and Web publishing functions have been further improved, making the software more stable.
The main functions of the system include: ① Using manual or automatic methods to carry out quantitative and timed irrigation and fertilization, and at the same time, it can realize unattended adaptive irrigation and fertilization; ② It can realize real-time display of crop environmental parameters, soil moisture and nutrient parameters, and operating status. , alarms, statistical inquiries and security protection; ③ trend graphs and historical records; ④ system parameter settings and user rights management; ⑤ crop irrigation related pre-value settings and fertilization formula management.
Valve management needs to be achieved through grouping, and a single valve group controls 5 valves. The valve group number can be compiled arbitrarily from 1 to 34 non-repeating numbers. A single valve cannot appear in multiple valve groups to achieve one-to- one accurate control of the valves. The fertilization formula system is preset to groups 1 to 13, and the system defaults to group 1, which means only irrigation is performed without fertilization. The system can set the conversion formula of the sensor. For example, the soil moisture sensor output is a voltage signal of O~2.5V, and its conversion formula is a cubic polynomial.