Design of Automatic Control System for Intelligent Micro Drip Irrigation Based o

Abstract. This paper analyzes the control requirements of drip irrigation system， designed automatic drip irrigation control system with IPC and PLC as control core， using WinCC as the man-machine communication window， combined with frequency， field bus and sensor technology. This paper focuses on the system hardware design， system control software and system monitoring software design. Through the field bus， the central management computer decide reasonable irrigation decision according to the soil moisture information， crop water requirement characteristics and predetermined irrigation scheme， and then issued a directive to the solenoid valve scattered， automatic carry out proper， required precision irrigation control. The practical application shows that： the system has stable working performance， friendly interface， improve labor productivity. The system can be expanded easily in terms of structure and function， can satisfy the application of different scale， demand， cost， have certain application prospect.

Key words： Drip irrigation； PLC； WinCC； inverter

0 Introductions

China is a large agricultural country； agricultural water in total water consumption will be in the proportion of about 70%， saving water agriculture is an important part of water conservancy. Agricultural production dependence on irrigation is extremely strong， serious waste of water in the first performance in irrigation water utilization rate is low， nationally， only 30%-40%， while developed countries this proportion is 70-90% [1]. Therefore， implementing water-saving irrigation， improve the utilization rate of irrigation water； saving water resources is a necessary requirement to achieve the sustainable development of agriculture in china.

The application of the water-saving irrigation method， irrigation water saving effect is the best [4]. Water and nutrient to the smaller flow is direct delivery to the irrigation method of crop roots near the soil layer through the low pressure pipeline system and emitters （drip， micro sprinkler etc.） in Micro irrigation [5]. Compared with flooding irrigation， micro irrigation can save water by using 40-70%， benefit is significant10-40%. Micro irrigation is characterized in the root of the crop irrigation， irrigation flow is small， need low work pressure， irrigation time lasting for a long time， can accurately control the amount of irrigation， which is easy to realize automatic control. The automatic control system can effectively realize water saving irrigation， improving irrigation water use efficiency； ease the contradiction of water resources become increasingly tense. Now use the irrigation systems are based on experience to determine how much irrigation frequency and irrigation amount， some use automatic timing control， all belong to the open loop control， automation degree is not high， these systems cannot implement precise irrigation based on soil Abstract feeling， do not meet the crop water requirement rules， it is difficult to realize the purpose of saving water. Therefore， this paper research and design a set of industrial control computer and PLC as the core of the drip irrigation automatic control system， can automatically monitor the large area crop growth and soil moisture， temperature and so on， so as to achieve on-demand accurate crop irrigation， saving water resources.

Micro drip irrigation system： Drip irrigation system incorporates a number of components， the main water source， the first hub， pipeline net and irrigation device tail device and pressure， flow measurement display instrument， as shown in figure 1.

1.1 Analysis of the working principle

Drip Irrigation is a new water-saving irrigation mode， it is the water uniformly， slowly into the crop root zone soil near the by installed in the capillary drop head， orifice or drip irrigation belt emitter. Because the flow of small water droplets slowly into soil moisture， mainly through the action of capillary tension infiltration and diffusion. Thus， in addition to soil moisture below near emitter saturation， the other in the soil water is in unsaturated state. Almost all the soil moist irrigation in different from traditional ground irrigation， it can save irrigation water， fertilizer application with water and can save fertilizer， promote crop growth， so the drip irrigation is a very promising local irrigation technology.

（1） Source water

Rivers， lakes， ponds， reservoirs， canals， wells， springs and other water quality conforms to the drip irrigation requirements can be used as water， long hair ecological science and Technology Park from the park in the reservoir water.

（2） Hub

The hub is composed of motor， filtration equipment， fertilizer， irrigation， valve， pressure gauge， flow meter， and its role is to water， pressure and water filtration treatment （or with fertilizer mix）.

（3） Water distribution network

The first hub treated water main pipe， branch pipe and capillary three stage pipeline. Pipeline network， in accordance with the requirements of conveying， assigned to each unit and irrigation emitters.

（4） Tail device

Tail device is a key component of the micro irrigation system， including capillary and connected with the emitter of drip irrigation system， the pressure of water upstream to into droplets， mist irrigation to the crop root or leaf.

2 Design of control system scheme

According to the design principle， the paper designs the overall structure of the computer control system， as shown in figure 2. The system is a closed loop automatic control system， its working principle sample the soil moisture through soil humidity sensor installation on site， through the field bus， data of the sensor output upload to the computer， industrial machine processing， display the data， PLC irrigation decision， issued the command to the field irrigation， control actuator solenoid valve， so as to realize the automatic irrigation control.

The whole system consists of three layers of communication networks： wireless sensor network top， middle and bottom Industrial Ethernet network， namely the management level， control level and the field level.

Management： Industrial Ethernet realize and manage communication between the host IPC and the garden and the Department of PC machine.IPC connected up production management， obtain the park production management information， drip irrigation plan， remote monitoring and control instructions， WinAC controller collect all kinds of data and soil humidity， flow， pressure and other information field equipment， and through the WinCC filing and reporting， data report can be printed at any moment， can automatically print and save in the hard disk. These data， on the one hand for crop production management plan， provide the basis of drip irrigation system irrigation scheduling： You can browse the long-term monitoring data （such as 1 days or 1 months） trend， automatic recording， display， storage of the irrigation run time station， water flow， instant cumulative record， save and print flow； On the other hand， that can provide the running status of equipment maintenance equipment， automatic monitoring， recording， warning the water pipe rupture caused by Water Leakage and electromagnetic valve fault and abnormal situation.

Control system： this system uses the industrial computer and WinAC software PLC as the control core of drip irrigation， with the STEP7 software and the industrial configuration software WinCC to realize control management， control， processing， display， human-computer interaction， communications and other functions into one PC. The WinAC controller to field device status， drip irrigation data information is sent to the WinCC control layer， also received from the monitoring layer of drip irrigation plan information， parameter setting and other control command， down control all the field devices， complete the specific task of drip irrigation. CP5611 is a PROFIBUS-DP communication card， PROFIBUS is the world's most widely used field bus， the central controller and field devices through the PROFIBUS-DP network to communicate with each other.

Field： according to diversity， region is vast， remote distribution characteristics of agricultural objects， the field install 10 wireless DP station， through the wireless sensor network， collect soil humidity， temperature， light intensity and other information， transfer from the control center opening / instruction closed solenoid valve； in order to maximize the use of network water conveyance capacity， regulating water through the operation of the frequency converter， in water treatment area used Siemens ET200S distributed I/O system as a control from the station.

3 The design of PLC control system

3.1 hardware structure of PLC control system

The soft PLC system hardware structure is as shown in figure 3. ET200S is selected as the control slave station in the water treatment area， and in each irrigation field， because the area size， crop varieties， production environment， variety， quantity， distribution density sensor and solenoid valve are different， so in every field we set a wireless DP slave station as autonomy control unit. The wireless DP station can be selected from the Department of independent research and development of products. CP5611 is DP master， a PROFIBUS special cable to complete data acquisition and transmission between master station and slave station， thus constituting a typical control structure of IPC+ field bus， distributed I/O. Field bus to replace a large number of distributed and independent connecting cable， can significantly save wiring， save time and cost. Therefore， this control system has high integration， data transmission and efficient， quick， convenient installation and maintenance.

3.2 Program structure and process

According to the requirements of the control system and we gives reasonable decomposition of the control part based on the detailed analysis and research on the drip irrigation system. The module design method， structured programming is controlled by program development， We will place the main control module in the 0B1 main circulation organization block， The high real time requirement and a certain frequency required to execute the program in the 0B35 timing cycle interrupt organization blocks， the initialization block be placed in OB100.Tissue blocks 0B1 determines the execution order block and under what circumstances an invocation block， function of FC and the function block FB （i.e. subroutine） used to accomplish a variety of tasks. According to these principles and control function， design the overall structure of the control program， as shown in figure 4.

4 Conclusions

The paper design of drip irrigation automatic control system based on IPC， soft PLC as control core， using WinCC as the man-machine communication window， combined with frequency， field bus， wireless sensor technology. Innovation is the soft PLC technology is applied to the agricultural integration of management and control， the design idea is to control， data processing， man-machine interface， communication network and other functions integrated in an PC， saving the hardware and installation costs. The system can be expanded easily in terms of structure and function， can satisfy the application of different scale， demand， cost and have certain application prospect.

Reference

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