| The level of grain moisture content is an important factor to consider in the transportation,processing and storage of grain.At the same time,the realization of online detection and real-time monitoring of grain moisture content is of great significance to the process of agricultural mechanization,and also lays the groundwork for the mechanization and intellectualization of the domestic dryer industry.At present,foreign dryers have long been installed with online monitoring system of grain moisture content.The monitoring functions are complete and the accuracy of detection is relatively high.However,the current domestic dryers loaded with moisture content detection system have a single monitoring factor,low accuracy of detection and poor real-time transmission of collected information.This research through a lot of market research and enterprise’s visit,after carrying out a research into the dryer grain moisture content online detection system,design a high precision measuring a variety of factors The detection system of the wireless transmission of information in this study the major requirements for projects and enterprises based on mixed flow dryer design a grain moisture content on-line detection system and bench test validation.The main contents of this study include:(1)Combined with the working flow of 30 T mixed-flow dryer,the mechanical structure and size of parallel pole type dynamic moisture detection device are reasonably designed.Through finite element analysis software COMSOL,the influence of the size of parallel plate structure on the width of edge electric field line is obtained to obtain the optimal size range with the least influence of parallel plate.The thickness,spacing and relative area of the parallel plate were designed and tested by response surface method.Finally,the optimum size of the parallel plate was obtained by experimental analysis.The upper and lower sealing plates of the moisture detection device are controlled by the electromagnet to open and close,which can be used to collect and arrange grain round and round.The device is placed in the nose position of the bucket lift of the warehouse after drying,so that not only enough grain can enter the sampling device,but also the collected grain has random nature.(2)The hardware design of grain moisture content is based on the detection system with STM32 chip as the control core.Among them,there are mainly parallel pole type capacitor conversion circuit,temperature sensor circuit,weight acquisition circuit and wireless communication and some anti-interference circuit main components.It can monitor the detection information of grain in real time with the wireless data transmission of the upper computer.The software part of mainly includes the main program,temperature acquisition program,weight acquisition program and wireless communication program.(3)In order to improve the accuracy of water content detection,the NARX prediction model of rice water content was established,and the number of input delay nodes,output delay nodes and hidden layer nodes of the prediction model were analyzed and determined.Finally,the error range of the prediction model was obtained by analyzing the results of water content prediction model.(4)Test of parallel plate type water content on line detection system.The test of the detection device mainly includes the calibration test of the parallel plate detection device,the moisture content detection range test,the detection error test and the repeatability test.The bench test results show that the detection range of the parallel plate water content detection device is 12% ～ 28%,and the maximum relative error is 1.58%.For drying machine often encountered in the grain moisture content in 15% ～ 25% repeated test,the error of the standard deviation within 0.1;The measurement error of water content with parallel plate meets the requirements of the item(≦5%). |
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