Design And Experiment Of On-line Detection Device For Capacitive Paddy Rice Moisture Content Of Combine Harvester

Intelligent Agriculture is our country’s agricultural development thinking.Precision Agriculture is the core component of agricultural machinery intelligence.An important manifestation of harvesting machinery is the use of a variety of reliable signal detection systems to obtain real-time crop moisture content information,impurity rate information,and loss rate information under the working conditions of the combine harvester to provide a data basis for agricultural intelligent systems.Among its,the paddy rice moisture content is an important indicator that affects the harvest quality and storage and processing of paddy rice.Too high moisture content can easily lead to rot and deterioration of paddy rice.Realize on-line detection of moisture content during harvesting,which can provide data reference for output calculation,transaction price and storage and processing methods in subsequent paddy rice production.Therefore,it is necessary to detect the moisture content of the harvested paddy rice in real time during the harvesting operation of the combine harvester.While satisfying the harvesting operation of the combine harvester,it is extremely important to realize the on-line detection of the paddy rice moisture content of the combine harvester.Based on the review and analysis of the development status of online paddy rice moisture content detection technology at home and abroad,this research applies modern sensor detection technology to detect the paddy rice moisture content of the combine harvester in real time,because there are many impurities in the tested samples.As well as the insufficient accuracy and sensitivity of the detection sensor,the detection device has poor accuracy and low stability.This research has developed an on-line detection device for rice moisture content installed on the combine harvester.Research work is carried out through theoretical analysis,structural design,simulation optimization,circuit design,capacitance influence test,sampling and impurity removal platform performance test,calibration and verification test and field verification test.The main research contents are as follows:(1)Total design of on-line detection device for paddy rice moisture contentAccording to the sampling and impurity removal platform,the functions of sampling and secondary screening and impurity removal are realized,through theoretical calculation and discrete element software EDEM simulation analysis,the key components of the sampling and impurity removal platform are designed,and the torque requirements of the screw conveyor and the grain discharge wheel of the sampling and impurity removal platform are analyzed to determine the models of the sampling motor and the abandoning motor were completed,and the total design of the sampling and impurity removal platform was completed.Taking advantage of the different dielectric properties of paddy rice and moisture,the detection principle design of the on-line detection system for paddy rice moisture content is completed by using the capacitance method.According to the working principle of the sampling and impurity removal platform and the detection principle of the paddy rice moisture content online detection system,the total structure of the detection device and the realization principle design are completed,which lays the preliminary foundation for the hardware circuit design and software program design of the later on-line detection device,and improves the detection device the accuracy and stability.(2)Hardware and circuit design of on-line detection system for paddy rice moisture contentThe hardware and circuit design scheme of the detection system is proposed,and the double circular parallel plate structure capacitive sensor entity is modeled by Ansoft Macwell software.Through simulation optimization experiments,the structure size of the double circular parallel plate structure capacitive sensor is determined.At the same time,the hardware selection and configuration design of the seven modules of the single-chip main control,step-down voltage stabilized power supply,capacitance sensor,temperature sensor,quality sensor,stepping motor and host computer communication are carried out.According to the preliminary goals of each module of the detection system,the working circuit of each module is designed with a modular idea.Based on the seven module circuits,the overall circuit design of the detection system is completed,which provides hardware guarantee for the detection device to realize the online detection of rice moisture content.(3)Software design of on-line measuring system for paddy rice moisture contentCombining the hardware and circuit design of the paddy rice moisture content on-line detection system,the software and program design plan of the on-line detection system is proposed,and the main program of the detection system,the system initialization subprogram,the capacitance detection subprogram,the temperature detection subprogram,the quality detection subprogram,computer communication subroutine,stepper motor subroutine,master computer display subroutine and moisture content detection subroutine.A modular programming method is adopted.The program code of the slave computer is written and burned in C language on the Keil＿u Vision5 software to realize the initial setting of the system modules,registers and serial ports,as well as the sensor data acquisition and preprocessing.The master computer is developed in C# language in the Visual Studio2017 software,which realizes the monitoring,control,and recording and storage of the working status of each module of the upper computer,which effectively guarantees the real-time,accuracy and reliability of the detection system.(4)Experimental research on on-line detecting device of paddy rice moisture contentCarried out the experimental research on the on-line detection device of paddy rice moisture content.Through the capacitance influence test,it is obtained that when the impurity content increases,the capacitance difference decreases monotonously,and when the impurity content exceeds 1.5%,the capacitance difference of the paddy rice changes more significantly.When the temperature rises,the capacitance difference monotonously increases,And the capacitance difference changes more significantly with increasing temperature.Through the performance test of the sampling and cleaning bench,it is found that the impurity content of the rice after the sampling and cleaning bench is not more than 1.2%,which meets the requirements of the sensor for detecting samples.The coefficient of determination of the fitting model of paddy moisture content,capacitance difference,and temperature established through calibration and verification experiments is 0.9866.It is verified that the model can describe the relationship between paddy rice moisture content,capacitance difference and temperature,and the verification experiment shows that the detection system is the largest the error is 0.42%,the average error is 0.22%,and the average relative error of the detection device is not more than 1.25%.Through field verification,the relative error of the detection device is less than 3%.