联合收获机电容式稻谷含水率在线检测装置设计与试验

针对联合收获机稻谷含水率实时检测过程中因样本含杂率高而导致精度和稳定性差的问题,搭建了兼具二次筛分除杂功能的稻谷实时采样台架,基于采样台架采用电容法设计了联合收获机稻谷含水率在线检测系统。设计了检测系统硬件电路,开发了上位机监控界面,实现了上位机和下位机之间的通信。分析了温度和含杂率变化对电容差值的影响规律,进行了采样台架性能试验,建立了电容差值、温度和稻谷含水率输出的关系模型,其二阶模型决定系数为0.986 6,并对模型进行了验证。结果表明:采样台架筛分后的稻谷含杂率均小于1.2%;室内试验时,检测系统最大误差为0.42%,平均误差为0.22%,检测装置平均相对误差不大于1.25%;田间试验时,检测装置相对误差小于3%,有效提高了在线检测精度。本研究可为稻谷含水率的在线获取提供参考。

Design and Experiment of On-line Detection Device for Capacitive Paddy Rice Moisture Content of Combine Harvester

In order to solve the poor accuracy and low stability problems of the real-time measurement system of paddy rice moisture content in combine harvester, a real-time sampling platform for paddy rice was set up, based on which the real-time measurement system of paddy rice moisture content in combine harvester was designed by capacitance method. The hardware circuit of the detection system was designed and the monitor interface of the master computer was developed to realize the communication between the master computer and the slave computer. The master computer can display and store monitoring information in real time. The influence of temperature and impurity rate on capacitance difference was analyzed and the performance of the sampling platform was verified. The relation models of capacitance difference, temperature and paddy rice moisture content output were established. The coefficient of determination was 0.9866, and the model was verified. The results showed that the impurity ratio of paddy rice was less than 1.2% after sieving by sampling platform. The maximum error of the detection system in laboratory testing was 0.42%, the average error was 0.22%, the average relative error of the detection device was no more than 1.25%. In the field validation test, the relative error of the detection device was less than 3%, which effectively improved the accuracy of on-line detection. The research result can provide a reference for on-line access of paddy rice moisture content.