Abstract: The greenhouse environment system is a nonlinear, time-varying and lagging complex large-scale system, so it is difficult to establish the mathematical model of the system, and it is difficult to obtain satisfactory static and dynamic performance by using conventional control methods.
State performance. According to the characteristics of greenhouse environment control, an intelligent greenhouse control system based on PLC is designed.
Key: PLC；; Intelligent control: greenhouse control
Intelligent greenhouse system is a resource-saving system developed in recent years.
Effective facility agriculture technology. This paper absorbs the high-tech greenhouse production technology of developed countries.
On this basis, the environmental factors such as temperature, humidity, CO, concentration and illumination in the greenhouse are controlled.
The control technology is studied and an intelligent greenhouse control system based on PLC is designed.
1 research on intelligent greenhouse control algorithm
1. 1 Main characteristics of greenhouse environment
The greenhouse environment system is a complex large-scale system, and it is necessary to establish an accurate control model.
Type a is difficult to do. Because crops have no special requirements for environmental and climatic factors.
Accurate, but the interval is vague, such as the temperature requirements of crops, as long as the temperature
In a certain period of time, in a certain interval, crops can grow well because
Therefore, there is no need to accurately control various parameters. Greenhouse climate and environmental work
As the control object of computer control system, it has the following characteristics: nonlinear system and subsystem.
Distributed parameter system, time-varying system, time-delay system, multivariable coupling system.
1.2 Differential equation of intelligent greenhouse control object
The temperature differential equation of intelligent greenhouse is:
Where, is the amplification factor of the intelligent greenhouse; Is the time constant of intelligent greenhouse;
Convert the interference heat inside and outside the smart greenhouse into the change of air supply temperature; Wei Zhi
The indoor temperature of the greenhouse can be kept constant.
2 system overall structure and hardware design
2. 1 overall system structure
2. 1. 1 control system design objective
Greenhouse control system is based on indoor and outdoor temperature sensors, humidity transmission.
Collected or observed by sensors, light sensors, carbon monoxide sensors, outdoor weather stations, etc.
Indoor and outdoor temperature, humidity, light intensity, CO, concentration and other environmental parameters in the greenhouse.
Information, through the control equipment for greenhouse insulation quilt, ventilation window, sunshade net, spray drip irrigation.
Drive/actuator control, such as greenhouse environment climate and irrigation fertilization.
Regulation to meet the needs of cultivated crop growth and development, for crop growth and development
Provide the most suitable ecological environment and greatly improve the yield and quality of crops.
2. 1.2 control mode
Variable temperature management based on time. According to the time of day.
Variable temperature management, according to the growth needs of crops, divides L days into four time periods and four hours.
Control the greenhouse according to different temperature control requirements in the interval. 1 4 times a day
The user can flexibly change the segmentation mode and the temperature of four time periods.
Users can also modify the set value.
Different seasons have different control methods, but the automatic control system is started.
The joint mechanism is different, but the control purpose in different seasons is the same, that is, environmental reference.
The number is adjusted to the vicinity of the set parameters. With the change of seasons and the growth of crops
With the long-term change, the temperature required for each time period also changes, so it can be used at this time.
Adjust the temperature control target of greenhouse by modifying the set temperature value.
2. 1-3 control scheme
This system adopts automatic and manual switching control methods to realize the control of
Automatic control of greenhouse improves the reliability of equipment operation. At run time, you can use the.
Button to switch between two control modes. Manual control is simple and reliable.
Electrical appliances, contactors, buttons, limit switches and other electrical components. automation
This mode is automatically controlled by the computer. Environmental factors are monitored by sensors,
And set the upper and lower limits. When a certain value is detected to exceed the set value, it will be sent.
The signal automatically turns on and off the driving equipment, thus causing the greenhouse environment to be affected.
The child controls are within the set range. Its operating cost is low, which can greatly save labor.
Force, reduce the labor intensity of workers.
2.2 Hardware composition of the system
In order to realize the environmental monitoring of intelligent greenhouse, the greenhouse environment is established in this design.
Computer automatic control system with long-time online control parameters. Realize that in the greenhouse
Long-term monitoring of temperature, humidity, CO, concentration, light intensity and other parameters. And can be based on
Requirements of intelligent greenhouse on temperature and humidity, skylight, side window, cooling wet fan, fan, wet
Automatic control of curtains, internal and external sunshade nets and other equipment. The computer is used as the upper computer for installation.
There is a monitoring software configured as t6.02, which can summarize, display, record and automatically form data.
Database, which realizes the automatic setting and remote monitoring of greenhouse control equipment. for
In order to ensure the reliability of the system, the greenhouse equipment adopts manual/automatic switching control.
Type, that is, in some special cases, the system can be switched to manual and flexible.
Shit.
3 software design of the system
3. 1 PLC software design of greenhouse control system
According to the basic requirements and technical requirements, the following points are listed: (1) Prevent contact errors.
Function: it can be solved by self-locking circuit; (2) System self-diagnosis function: pig.
The body has this function; (3) Fan control: The greenhouse is equipped with a set of fans which can be started at the same time.
Start and stop, when the temperature in the greenhouse exceeds the predetermined value, it is first controlled by PLC.
The four side windows open automatically, the fan is started after a delay of 5 seconds, and then the wet curtain water pump is delayed for 5 seconds.
Start, thus reducing the temperature of the greenhouse; (4) Side window control: there are 4 in the greenhouse.
The side window is controlled by the motor, and the side window row is controlled by the setting of the motor limit.
Cheng. The solution is similar to the previous point, but it can be matched considering the refinement of the program.
PGI's interrupt function command solution; (5) Automatic/manual control of the system: available.
The switch value is used as the input signal of PLC to realize the conversion of control program;
(6) Wet curtain pump control; (7) Control of sunshade net; (8)CO and qi (control; (9) Control of fill light; (1O) Scalability: Leave some memory in the PLC.
Both storage space and ports can be solved.
3.2 Software design of control system
Used for fans, skylights, side windows, circulating fans, sunshade and wet curtain pumps in the system.
Control is to send switch instructions through PLC and control related machines through AC contactor.
The beginning and end of the structure. Because the PLC detection system has high sensitivity, it can control the temperature.
The indoor disturbance is quickly reflected, and it is difficult to persist because of the large transmission lag in the greenhouse.
The traveling mechanism moves frequently, which affects the service life. To do this, add sometimes in the program.
Adjustable delay module, which can adjust the delay according to the specific situation when using, so as to control
It works best.
3.3 Design of system configuration monitoring software
Configuration software can be set through programmable controller and various data acquisition cards.
Collect data in real time, and then issue control commands to monitor whether the system is running normally.
A general software package. Its main functions are as follows:
(1) Remote monitoring function. It can remotely monitor the temperature of multiple seats through communication lines.
The current status of the room includes outdoor temperature, light intensity, wind speed, wind direction, rain and snow information.
Quantity, indoor temperature, indoor humidity, controller temperature and the position of three groups of independent ventilation window.
As well as the position and switch state of the internal and external sunshade curtains, as well as primary air and secondary air.
Fan, wet curtain, mist, heater, circulating fan, fill light, C0, air filling valve, water heating.
The state of the three-way valve and various forms of alarm monitoring can also monitor the irrigation valve.
Light intensity, wind speed, indoor temperature, indoor humidity, CO, concentration, water heating temperature, etc.
Maximum value, minimum value and average value of month, whole week, whole day and current period.
(3) Operation record function of greenhouse equipment. It can record greenhouse equipment online.
Time of state change, current state and position, current target temperature, indoor temperature.
Temperature, target humidity and indoor humidity, and can be printed.
(4) Remote setting function. The programmable controller can be modified remotely through the communication line.
All setting parameters of the controller.
(5) The function of generating graphs. It can be the same as a plan view or a three-dimensional view.
Draw outdoor temperature, light intensity, wind speed, target temperature and indoor temperature at any time.
Temperature, target humidity, indoor humidity, CO, concentration, water heating temperature, etc.
Monthly, weekly and daily curves and print them out.
4 conclusion
This paper analyzes the influence of the corresponding actions of greenhouse actuators on environmental factors.
Loop, programmable control technology, frequency conversion technology, configuration monitoring technology and sensor technology.
This technology is applied to the design of greenhouse control system, and an intelligent greenhouse based on PLC is developed.
Control system. besiege
situation
(2) Data statistics function. It can count outdoor temperature and light at any time [2]
Outdoor temperature and light can be counted at any time.
14O
[References]
Deng, Zhang Kanyu, Gong. Application of Intelligent Control Technology in Agricultural Engineering
Use. Modern agriculture, 2003 (12): 1 ~ 3
Shen Maoxiang, et al. Investigation on Facility Agriculture in Netherlands and Thinking on the Construction of factory farming in China
Testing. Journal of Agricultural Engineering, 2000, 16 (5)