Design Of Grain Yield Measurement And Calibration System Of Combine Harvester Based On Quantitative Screw Conveyor Technology

With the large-scale planting of land and the rise of agricultural machinery cooperatives,the development of high-level agricultural technologies such as precision agriculture and smart agricultural machinery have provided new ways for real-time monitoring of grain yields,thereby obtaining more accurate yield prescription maps.Precision agriculture and smart agricultural machinery integrate 5G technology,Internet of Things technology,intelligent control and detection technology in the production and application of agricultural machinery,and the acquisition of combine harvester output information is an important part of it.By mounting the production measurement system on the combine harvester,it can not only obtain the yield information of farmland plots,but also can be used to analyze the spatial variation of crop yields to provide support for smart agricultural machinery and smart agriculture.In order to raise the precision of the domestic combine harvester production measurement system,this research is based on the first generation photoelectric production measurement system,combined with quantitative screw conveying technology,and developed a combine harvester grain yield and calibration system which based on quantitative spiral conveyor,realized the grain yield of accurate measurement of system error and dynamic calibration.The main work includes:(1)Development on Hardware of grain yield measurement and calibration system of combine harvester based on quantitative screw conveying technology.The hardware of the system includes sensor module,data acquisition and processing module,data transmission module,display terminal and mounting bracket.Sensors include grain volume sensor,unloading grain speed sensor,granary grain level sensor;Data acquisition and processing module includes STM32F103C8T6 microcontroller,various peripheral circuit support.(2)Software design and development of grain production and calibration system for combine harvesters based on quantitative screw conveying technology.The system software development includes the embedded software development of the lower computer and the software development of the upper computer display interface.The lower computer software realizes the cooperative work of various hardware modules,completes the collection of sensor data,acquisition of output information,data transmission,and output model coefficient correction functions.The host computer realizes the functions of unloading original received data display,unloading information display,system calibration and historical report.(3)Study on unloading model of quantitative screw conveyor and design of system self-calibration method.After kinematic analysis of the grains in the combine harvester unloading screw conveyor using the single-mass point method,a three-stage grain unloading model of the combine harvester quantitative screw conveyor was established,and based on this,proposed the system self-calibration method and quantitative Calibration method of screw conveyor unloading model.(4)Performance verification of combine harvester grain production measurement and calibration system based on quantitative screw conveyor technology.The indoor bench test and the field dynamic test were carried out respectively.The laboratory bench test was divided into the performance test of the speed sensor for unloading grain and the model verification test for unloading grain.The performance test results of the unloading speed sensor showed that the error was less than 2%,and the maximum standard deviation at different speeds was less than 2.5r/min,which had good accuracy and stability.The system unloading model verification test showed that the maximum error of the quantitative spiral conveying model was less than 2.5%under different unloading speed,and the unloading speed showed a linear relationship with the instantaneous flow rate of quantitative spiral conveying,R~2 reaching 0.993.In the field dynamic experiment,the maximum error monitored by the unloading speed sensor was 2%,and the maximum standard deviation at each speed level was 3.2r/min.The dispersion degree was small,and it has good stability.The error of the system unloading feedback model was less than3.1%,and the system feedback model has good accuracy.The field measurement test showed that the error range was-2.95%-3.13%,and the overall error range was less than 3.5%.Compared with the first generation of photoelectric production measurement system,the system not only has better accuracy and stability,but also can automatically feedback and calibrate the system,reduce the error fluctuation of the system and reduce the system error.