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The application of automatic control and electronic computers to realize the automation of agricultural production and management is one of the important signs of agricultural modernization. In recent years, the rapid development of electronic technology and information technology has brought about a revolution in greenhouse control and increased agricultural production. The increase in quality has produced huge economic and social effects. With the rapid development of the national economy, modern agriculture has made considerable progress, and greenhouse engineering has become an important part of efficient agriculture. Since the advent of the computer-controlled intelligent greenhouse, it has become an important means and measure for the development of modern agriculture. Its function is to use advanced technology and modern facilities to artificially control the environmental conditions of crop growth, so that crop growth is not affected by the natural climate, so that it can be factoryized all the year round, and produce high efficiency, high output value and high benefit.
A complete greenhouse automatic control system includes the following parts:
1 On-site monitoring components: including temperature monitoring, humidity monitoring, CO2 concentration and other monitoring components. These devices are equivalent to the eyes of the entire control system, real-time monitoring of the conditions of the greenhouse, in order to implement control.
2 Execution structure: such as various pumps, heaters, CO2 generators, lighting control devices and other actuators. These devices are equivalent to the hands of the entire control system, and the instructions of the automatic control system are executed through these devices to achieve the control goal.
3 A/D and D/A conversion modules. Because the automatic control system cannot recognize various electrical signals, it must be converted into a standard digital signal to be recognized by the computer. Similarly, the computer sends out a standard digital signal. These devices are like the human nervous system, transmitting various signals to the brain, and transmitting control signals to various actuators.
4 Control system host: The host implements various control schemes, and implements different control schemes according to different environments, crops, and growth periods. It is the core of this control system, equivalent to the brain.
5 Human-computer interaction system: The staff can understand the working conditions of the system through the human-computer interaction system, and can issue manual instructions to the control system through the human-computer interaction system to set the working environment of the control host. The human-computer interaction system can realize the human-computer interaction of the system through the Zijinqiao configuration software.
The above classification is a typical control system. According to the complexity of the system, the configuration of the system will increase or decrease. If there is a small system, you can directly use the computer as the host of the control system, which is integrated with the human-computer interaction system.
Function description
The greenhouse environment includes a very wide range of content, but the commonly referred to as the greenhouse environment mainly refers to the temperature and humidity of the air and soil, light, and CO2 concentration. The computer receives information of various environmental factors through various sensors, and controls the operation of the corresponding greenhouse equipment through logical operations and judgments to adjust the greenhouse environment. Output and printing equipment can help growers perform comprehensive and detailed data analysis and save historical data. The system mainly has the following functions:
1. Comprehensive environmental control
The computer is used to realize the comparative analysis of environmental parameters, and the four-season continuous working condition control system. , Proportionally adjust the ambient temperature, humidity and ventilation. The CO2 generator adjusts the environmental CO2 concentration in proportion to the needs, and the outdoor roof sprays in summer. Under the premise of ensuring the indoor light intensity, the combined adjustment of the environmental temperature and ventilation can achieve the effect of forcibly lowering the environmental temperature. Through the computer, the electric actuators of the greenhouse are adjusted as a whole to automatically adjust the temperature, humidity, light, water, air and other conditions required for crop growth. In addition, the greenhouse is disinfected by the ozone disinfection purifier.
2. Fertilizer irrigation control
Use computer fertilizer and water irrigation management system. According to the needs of the crop area, the nutrient solution composition, PH and EC value of the hydroponic area are comprehensively regulated. For the basic cultivation and soil cultivation area, the water potential value of the substrate and soil is set according to the needs of crop production, and the irrigation time and frequency of drip irrigation and sprinkler irrigation systems are automatically adjusted.
3. Emergency handling
Using computer to measure environmental parameters and state limit value feedback alarm protection system. Set the limit value of the greenhouse environment and the limit value of the crop growth environment parameter alarm protection system according to the various parameters of the crop, which improves the safety of the entire system.
4. Information processing
Adopt computer distributed control information management system. Information processing is completed by the central control computer. The host computer is connected to the field controller through a local digital communication network to realize remote two-way control and centralized data processing of the whole system. Its functions include running real-time parameter executor to simulate the state significantly, historical data storage and retrieval, data average report, curve display and printing.
Below we take grape greenhouses and cucumber and tomato greenhouses as examples to introduce their growth parameters:
Grape greenhouse:
a. During the winter dormancy period, the temperature in the greenhouse should be kept at 5°C for about 90 days. After the dormant period, the temperature in the greenhouse should be controlled at 25-30℃ during the day and 15-18℃ at night.
b. The humidity should be maintained at 50-75% and not more than 95%.
c. The light intensity should be maintained at 45000-55000 Lux
d. The carbon dioxide concentration is maintained at about 1000 PPM from sunrise to about 10 o’clock in the morning.
e. The PH value is maintained at 7-7.5.
f. The total ion concentration of EC value is maintained at 1‰-2‰, and it can be adjusted at any time.
Cucumber and tomato greenhouse:
a. During the seedling stage, the temperature in the greenhouse should be kept at 13-15℃. After planting, it should be kept at 25-28℃ in the morning, 20-25℃ in the afternoon, and 15-18℃ at night.
b. Humidity: Cucumber is kept at 70-75% during the day and 85-90% at night; tomato is kept at 65-75% during the day and 75-85% at night.
c. The light intensity should be kept at about 50,000 lux for tomatoes and ensure 12 hours of light; for cucumbers should be kept around 40,000 lux, and 8-10 hours of light should be guaranteed.
d. The carbon dioxide concentration is maintained at about 1000 PPM from sunrise to about 10 o’clock in the morning.
e. The PH value is maintained at 6.5-7.5.
f. The total ion concentration of EC value is maintained at 1‰-2‰, and it can be adjusted at any time.
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