| Vineyard vegetables are the main varieties cultivated in greenhouses in China,accounting for a large proportion.Due to the special closed environment in greenhouses,the vegetables cultivated in greenhouses are prone to diseases and insect pests.In daily greenhouse production and management,pesticide spraying is indispensable.The degree of automation of existing greenhouse plant protection machinery in China is low,and the effective utilization rate of pesticides needs to be improved urgently.In order to reduce the amount of pesticides and reduce environmental pollution,it is necessary to carry out the research on target variable precision spraying equipment suitable for greenhouse environment.In this study,the greenhouse vine cultivation vegetables were taken as the research object.According to its growth mode and planting characteristics,the control system of target variable spray device in greenhouse was designed.The target distance information of vine cultivation vegetables was obtained by infrared ranging sensors at different heights.A specific target detection algorithm was designed by using 32 bit single chip microcomputer as the control center.By setting the spray distance interval and the spray flow decision value interval of a single nozzle,the selftuning fuzzy PID control algorithm was developed.By controlling the electromagnetic valve and the electric proportional control valve,the precise target variable spray of vine cultivation vegetables in greenhouse was realized.The spray control system was experimentally verified in the greenhouse ridge sprayer.This design mainly carried out the following research:1.Overall design of control system for target variable spray device in greenhouse.Based on the comparative analysis of the existing target information acquisition methods and variable spray flow regulation methods,the overall scheme of the control system of the target variable spray device in greenhouse was determined.With 32 bit single chip microcomputer as the control center,by setting different height infrared distance sensor to detect the distance,according to the control algorithm decision control solenoid valve and electric proportional control valve for target variable spray operation.The main parameters of spray rod sprayer suitable for greenhouse ridge operation were determined.According to the actual test site,the spray distance setting interval [10-60cm]and the single nozzle spray flow decision value interval [4.4-7.6m L/s] were determined,and the spray flow value was divided into five grades according to the maximum diameter range of crops,which was used for accurate target variable spray decision control.2.The hardware and software module design of target variable spray control system in greenhouse.According to the operating characteristics and design requirements of greenhouse environment,the main components of the control system are analyzed and selected,and the hardware connection circuit and software module processing program are designed.The STM32F103 series ZET6 CPU is selected as the main control chip,and the corresponding sensor information detection module,target variable spray execution module,communication module,mode selection module and reminder module are further designed.In MDK5.14 development environment based on C language,the main program of single chip microcomputer,sensor information detection subroutine,target variable spray control subroutine,mode selection subroutine and reminder subroutine are designed.3.Research on precise spray control model of target variables for vine cultivation vegetables.In order to ensure the excellent spray effect and control accuracy,the accurate spray control model and algorithm design for target variables were carried out.The target variable spray algorithm is the core algorithm of the control system.The single chip microcomputer detects the distance signal according to the infrared ranging sensor set at different heights.Through algorithm operation,the opening and closing of different solenoid valves and the opening of the electric proportional control valve are controlled to realize real-time spray control.In order to solve the problem of frequent opening and closing of the electromagnetic valve in the system during spray operation,a continuous multi-target detection algorithm was designed.In order to solve the problem of tip leakage of vine cultivation vegetables,an enhanced variable height spray algorithm was proposed and implemented.Aiming at the problem of hysteresis and nonlinearity of electric proportional control valve,a fuzzy PID algorithm is designed and developed.The mathematical model of conventional PID algorithm and fuzzy PID algorithm is established in MATLAB software.The unit step response signal is simulated and compared.The results show that the maximum overshoot of the latter is reduced by 15%,the stability time is shortened by 1.4s,and the lag time is shortened by 0.75 s,which can meet the design requirements of the system.4.Experimental analysis of target variable spray control system in greenhouse.In the process of target variable spray in greenhouse,there is a lag phenomenon caused by the delay time of spray response.In this design,the infrared ranging sensor is installed with forward angle relative to the spray nozzle to realize early spray detection and improve the spray effect.The measurement results of spray delay time showed that the average spray opening delay time was 0.40 s,the average spray closing delay time was 0.51 s,and the spray delay time selected in this design was 0.46 s.The rod sprayer works at a speed of 0.5m/s,and the average distance between the spray nozzle and the target crop is 45 cm.It is calculated that when the nozzle is installed horizontally,the design scheme of tilting the infrared ranging sensor forward by about 27° relative to the horizontal nozzle is adopted.The offset angle measurement experiment of the infrared ranging sensor solved the spray lag phenomenon caused by the delay time of the spray response,and ensured that the sprayer could carry out the spray operation timely and accurately when entering the tomato line.The target identification and leakage rate test were carried out with the tomato plant as the test object and the spray nozzle opened due to the enhanced variable height spray algorithm.The test results show that the spray control accuracy of the spray system is 100%,and the full cover spray on tomato height can be realized.5.Experimental study on the performance of target variable spray control system between greenhouse ridges.The overall performance test of the control system includes the drug saving rate test and droplet deposition test.Taking greenhouse tomato as the research object,the results of pesticide saving rate test showed that the control mode of target variable spray in greenhouse saved31.3% of liquid on average compared with conventional continuous spray.Under the same experimental conditions,the invariant target spray system saved 27.9% of liquid on average compared with conventional continuous spray.The droplet deposition test was carried out using the international standard water sensitive paper card(76*26mm).The results showed that the average droplet deposition number of the target variable spray system in the upper positive,upper negative,lower positive and lower negative positions of tomato leaves in the greenhouse was 1635,912,1344,783.Compared with the conventional continuous spray method in the greenhouse,the number of droplet deposition in the corresponding detection positions decreased by 341,574,310,241.The average droplet coating rate was 24.36%,9.46%,35.31% and 13.34% in the upper positive,upper negative,lower positive and lower negative positions,respectively.Compared with the conventional continuous spraying method in greenhouse,the droplet coating rate decreased by 4.33%,9.3%,6% and 7.34% in the corresponding four positions,respectively.The variation trend of droplet deposition number was similar to that of droplet coating rate in different positions of tomato,and the national standard for spraying quality evaluation met the operation requirements. |
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