基于PLC的植物水分和养分精确调节控制系统的设计【中文3800字】
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基于PLC的植物水分和养分精确调节控制系统的设计【中文3800字】,基于,plc,植物,水分,水份,以及,养分,营养,精确,调节,调理,控制系统,设计,中文
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Physics Procedia 33 ( 2012 ) 429 436 1875-3892 2012 Published by Elsevier B.V. Selection and/or peer review under responsibility of ICMPBE International Committee.doi: 10.1016/j.phpro.2012.05.085 2012 International Conference on Medical Physics and Biomedical Engineering Design on the Precise Regulating Control System for Moisture and Nutrient of Plants Based on PLC Liu xin ,Lu Guang,Yu Ming School of Northeast Forestry University Information and Computer Engineering College, Harbin 15040 Abstract The moisture and the concentration of K in the soil in plant ecological park was accurately controlled based on the SIMATIC S7-300 PLC controller. The hardware of control system based on PLC was set up, at the same time, the control algorithm used in the moisture and concentration of K was analyzed and the software design of control system was also completed. At last, the control system was proved to be practicality and superiority by comparing the quantity and quality of potatoes yield from the two plots, one is controlled by the designed controller and the other is in the natural growth. 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of name organizer Keyword PLC controller, accurately control, the moisture of soil, the concentration of K Water and nutrient is necessary condition to ensure normal growth and development of the plant. To control the water and fertilizer irrigation of plant accurately and to maintain optimum plant growth in demand, it not only helps reduce water and fertilizer application rate, but also helps plants produce the quantity and quality. The water-saving irrigation technology of modern agriculture has provided a condition for accurate irrigation of water and fertilizer, meanwhile, automation control technology in water-saving irrigation has provided a guarantee to achieve optimal control of water and fertilizer. Agriculture in developed countries like the United States, Israel, Netherlands, Canada, Australia has developed a series of versatile, powerful fertilizer irrigation controllers2-7, and our irrigation control system in the development of the trial is still in development stage, has a larger gap with developed countries. With the lack of water resource, developing a water-saving irrigation control system suitable for the Chinas soil properties ,with independent intellectual property rights can not only solve the water shortage situation, but also has great social and economic benefits8 .In view of this, this article developed a set of irrigation system controller with automatic Available online at 2012 Published by Elsevier B.V. Selection and/or peer review under responsibility of ICMPBE International Committee.Open access under CC BY-NC-ND license.Open access under CC BY-NC-ND license.430 Liu xin et al. / Physics Procedia 33 ( 2012 ) 429 436 yregulation on plant moisture, nutrients. Its controlling core of the system is S7-300 PLC which created by Siemens company. Measure the content of soil water and nitrogen (N), phosphorus (P ), potassium (K) and other nutrient through the soil moisture sensor and ion sensitive electrode and input into system, use PID proportional integral control algorithm to control the system, export digital control signal to directly control the water irrigation system in opening or closing electromagnetic valve, implement accuracy controlling for water and fertilizer, in order to ensure the plant growth in the best environment. 1. The hardware design of the control system PLC is a general-purpose automatic control device, which integrated the traditional relay control technology, computer technology and communication technology, with control capability, operational flexibility, high reliability, and suitable for continuous long-term working characteristics. It is very suitable for high efficient control requirements for plant ecological park. 9 The control system is designed mainly by soil moisture sensor, the concentration electrode of ion-sensitive, transmitter, PLC controller, PC, etc, shown in Figure 1.Taking PC as a host computer, according to plant growth on the demand for water and fertilizer, the system can achieve parameter setting, data communication, storage, real-time display. And take PLC as slave computer to achieve the site variable detection, data processing and judgments, the ratio and implementation of drip irrigation and nutrient solution curve (fertilizer) according to plant growth control curve, implementation of communication with the host computer. The lower machine, this paper selected SIMATIC S7-300 series PLC as controller core, the design of the modular structure, each independent module can be widely combined and extended. According to the control requirements, it can get the hardware structure of the control system (shown in Table 1). Because the factors that affect plant growth (such as temperature, humidity, nutrient solution concentration, etc.) are mostly a multi-input, multiple output, nonlinear control variables of large time delay 10.Two kinds of impacts on plant growth are chosen in the experiment as the biggest factor (moisture and fertilizer ) for regulation, control variables are soil humidity and K + concentration, the two signal input to the PLC A / D module through the corresponding humidity sensor (Beijing LianChuang SiYuan Science and technology company FDS100 type) and ion concentration electrode (U.S. Van London-pHoenix company K001508 type, number of domestic delivery is L2850595). Soil humidity sensor output 4 20 mA of current, direct access to the PLC analog input module SM331, output signal of K + sensitivity selection electrode is weak, it can access to the SM331 module only after the signal conversion of transmitter. Digital quantity control signals which output from control system directly drive irrigation electromagnetic valve action, without intermediate links. Tab. 1 the hardware controller of S7-300PLC PLCModule NAME ORDER Power supply Module PS307/5A 6ES7 307-1EA00-0AA0 CPU Module CPU 314 SM331 6ES7 314- 1AG13-0AB0/v2.6 Analog Input Module AI812Bit 6ES7 331- 7KF02-0AB0 Liu xin et al. / Physics Procedia 33 ( 2012 ) 429 436 431Digitaloutput Module SM322 DO1624 6ES7 322- 1BH01-0AA0 Fig. 1 the structure frame of plant entironment control system based on S7-300PLC 2. The software design of the control system 2.1 control algorithm research (1) Integral separation control As the control variable has the particularity in this paper, it is difficult for the typical PID control algorithm to achieve better control effect, therefore, this paper uses the separated integral (P-PI) control algorithm, supplemented by way of humidity PWM automatic control and K concentration. The main purpose of separation control of Integral is to avoid a large deviation in a short period of time as the object start, end or significantly change the initial value, also a large overshoot as well in resulting of the accumulation of integral. In view of this, to set the two threshold values 1, 2 0, when the absolute value of deviation is 1 2, cancel integral part, thus it can achieve separation of integral control . Algorithm is shown in Equation 1. 0() () ()()(1)kpiIDpTuk K ek TeiTTKekekT(1) Among u(k) t=k Control amount T T/TIIntegral time 432 Liu xin et al. / Physics Procedia 33 ( 2012 ) 429 436 TD/TDifferential time 21210()()1()ekbekekUse separation integral control has a smaller overshoot to achieve a shorter settling time. Because the conventional PID control in the early control, integral accumulated role is too much to lead to large overshoot and long process of elimination of residual, however, the integral role of the integral separation is fully applied to eliminate residual characteristics. The design of choice has the following properties of the function to replace the original fixed one, its advantages are as below: 1 the continuous,2 the function is simple, and contains adjustable parameter with clear meaning, simple setting , a large margin adjustment .This can make the structure of PID is fully used, and the changes from P to PI structural is sliding continuous 11 .This paper choice”, “as the setting value. (2) PWM control In the designed system of this paper, the output control acts on the electromagnetic valve of spray water through the solid state relay, the control part adopts PWM power (pressure) or PWM, which control the power through controlling alternating current wave of a period of time. This system realize the PWM function by controlling on connected time of solid state relay in a control cycle, DC control side input PWM control pulse wave directly, exchange control output end connect with the AC power, PWM wave control AC circuit switching, PWM control mode output is shown in Figure 2. By adjusting the electrifying time, it can adjust system power of a control cycle. (2)uk ()uk(1)ukFig. 2 the PWM illustration of humidity control 2.2 Control system software components and control flow According to the above control algorithms, use Step7 software to write and debug the control procedures, Step7 software provides users with a structured program design, a user program is composed by the startup program, the main program and interrupt response procedure for a variety of different modules, the operating system has set up the framework of these modules, What the user need do is to control the system according the specific requirements of the control tasks, to hierarchical divide the control tasks ,and to program each modular program, then call these modules in user main program. Modular way of programming functions make the system easier to manage, and more convenient for function expansion. Based on the division of system function, the control task is divided into various functional module. Module is be called through the running state of the system and the control instructions. Considering the plants have certain effect on soil and air humidity of the surrounding during Liu xin et al. / Physics Procedia 33 ( 2012 ) 429 436 433the growth process 12-14. According the modular software design idea, the main program module of this control system software mainly includes signal collection filtering module, the true value calculation on on-site signal module, sensor calibration module, automated control module, system output module. According to the control algorithm, the control system software flow diagram of soil moisture of plant ecological park can be shown in figure 3. () 0uk()uuk0() () ()kpjITuk K ek ekTFig. 3 the flowchart of humidity control in soil In this paper, the control humidity of automatic control program is slightly lower than that of the set point, i.e., when the deviation is less than 0.05, the controller is not active, only call control function block as it is more than 0.05. By calculating the deviation, call control algorithm program of integral separation, calculate the energized time in a control cycle of the solid state relay, control opening and closing of nozzle valve. The PWM control can be achieved. According to the aforementioned control algorithm of K concentration, K + concentration use TP-PID control output as switch quantity, system has the advantages of simple structure, high reliability, easier debugging. as long as chose a correct clock pulse ,it is earlier to able to achieve satisfactory control performance, and so long as transfer the algorithm results into output pulse width, then allow to drop the potash salt, set the dropping cycle and the amount of each dropping ,the control flow graph is shown in figure 4. 434 Liu xin et al. / Physics Procedia 33 ( 2012 ) 429 436 3. Plant water, nutrient regulation system performance test As the control system hardware and software design has been completed, calibrated the sensor in the room, and then transferred the whole system into trials, in the experiment, planting the potatoes as an example for testing moisture, nutrient regulation system performance. Two area plots are both 100 m2, 230 potato plants, give 1 plot a sprinkler under natural conditions, keep 2 plot irrigating in the designed control system ,After 100 days of growth, then harvest all potatoes in two areas, do a statistical analysis, the results are shown in Table 2, 3 . Table 2 represents potato consumption comparison of water and fertilizer in a lifetime of two plots, this can be seen from the table, Under the control growth, the consumption of water and fertilizer for same amount potatoes are less than the natural growth condition, therefore the design of the plant regulation system for water, nutrient has proved its energy saving function. From Figure 3, although potato plants consume less water and fertilizer under the regulation of growth, but the potato yield and quality have increased, further demonstrate that the designed control system has practicability. 4. Conclusion In this paper, Author put SIMATIC S7-300 PLC as the core controller, design the automatic control system of plant water and nutrient, apply the separation integral (P-PI ) control algorithm to automatic control the moisture and nutrient needed for plant growth, complete the system hardware and software design, set up the whole control platform, and work for a comparison experiment on the regulation of potato growth ,prove that the designed control system has the effect on reducing the water consumption and improving the production and quality of potato. The successful completion of this system has laid the foundation for automatic irrigation system research of water and fertilizer which is suitable for the development of Chinas agricultural conditions. Tab. 2 the contrast of water fertilizer dosage between different growth conditions No. plots Water (kg) Nitrogen fertilizer (kg) NH4HCO3Potash consumption (kg) KCl The amount of phosphate (kg) Ca(H2PO4)21- Natural growth 2365 14.1 3.5 15.6 2- Regulation of growth 1897 10.5 2.7 11.5 Tab. 3 the contrast of output between different growth conditions NO. Production (kg) Yield per plant (kg) The average size (mm) Average number of ( ) Starch production plant (g) Natural growth 65.8 0.31 30 2.6 15.7 Regulation of growth 97.5 0.45 43 3.5 19.1 Liu xin et al. / Physics Procedia 33 ( 2012 ) 429 436 4351Cone10Cone2Cone20ConeFig. 4 the flowchart of K+ concentration control in soil References 1 Xueliang Ma, Qiheng Zhao, Hehong Tian etc., The Status Quo and Development of Global Equipment and Technology for Water-saving Irrigation J water-saving irrigation, 1999 2 4-7 2 Bing Zhang, Shouqi Yuan, Li Cheng, The Status Quo and Expectation of Global Automation Equipment for Water-saving Irrigation J irrigation machinery, 2003 (2) 37-41 3 C.C. Van Donkelaar, R. Huiskes. The PTHrPIhh feedback loop in the embryonic growth plate allows PTHrP to control hypertrophy and Ihh to regulate proliferationJ. Biomechan Model Mechanobiol, 2007, 6: 55-62 4 Bambang Marhaenanto and Gajendra Singh. Development of a Computer- Based Greenhouse Environment Controller. March, 2002,13,136-146 5 J.M.Aaslyng, J.B.Lund, N.Ehl
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