【作者】 韩静；

【导师】 王熙；

【作者基本信息】 黑龙江八一农垦大学 ， 农业机械化工程， 2020， 博士

【摘要】 本文根据农业生产中对颗粒肥料的施播量测量的需求,以微波多普勒效应为基本原理,设计了颗粒肥料流量检测系统。通过研究微波多普勒信号的频率、浓度与颗粒肥料质量流量的关系,对多普勒信号进行滤波去噪、频带细化、阈值谱峰搜寻等算法分析,优化系统,实现微波多普勒法在农业施肥中的应用。通过施肥作业中颗粒肥料流量的实时监测,为精量施肥提供理论与数据支持,对促进精量施肥机械化自动化发展具有重要意义。本文从理论分析、算法研究、模型改进及试验处理等方面,对颗粒肥料质量流量测量进行了深入的研究。1.对三种颗粒肥料进行物理力学特性分析以磷酸二铵、尿素和氮钾复合肥为研究对象,通过实验测得肥料颗粒的物理特性和力学特性。三种颗粒肥料球形度均为80%以上,出厂时颗粒肥含水率最高不超过2.35%,颗粒密度最高为1.53g/cm~3,容积密度最高为1.67g/cm~3,休止角最大为38.5°。颗粒肥料的含水率与刚度系数和破碎力成反比。2.构建多普勒回波信号与颗粒肥料的下落速度、排肥管道颗粒浓度的关系根据多普勒回波信号中所包含的频率及能量信息特征,得到频率与颗粒肥料下落速度、功率与排肥管道颗粒浓度的关系,确定颗粒肥料质量流量模型。通过微波多普勒信号频谱算法对比分析,采用Zoom-FFT复调制细化算法及周期图法(直接法)得到肥料颗粒的浓度参数。3.颗粒肥料流量测量装置结构设计及微波多普勒回波信号的滤波去噪通过颗粒肥料流量检测装置的台架试验,采集微波多普勒回波信号,选择EMD分解并保留模态混叠分量的小波阈值去噪方法保留有效回波信号特征的平滑曲线。得到滤波去噪信号的互相关系数R为8.693、信噪比为0.962、相对能量比为0.049。4.微波多普勒信号阈值谱峰搜寻及台架试验针对排肥量频谱信号中存在的频谱混叠、栅栏现象和谱线泄漏等现象,在Zoom-FFT复调制细化的过程中,选择旁瓣效果性能良好的Nuttall(4项3阶)窗函数,减少频谱分析的误差。采用阈值谱峰搜寻得到颗粒肥料的平均下落速度,通过功率谱密度计算,得到排肥管道中不同测量高度下颗粒肥料下落速度与浓度的反比关系。5.单通道及多通道排肥台架试验通过2F-12型变量施颗粒化肥试验台完成单一品种及混合品种颗粒肥料排肥试验。通过修正经验模型参数将颗粒肥料质量测量值与实际值之间的相对误差减小到0.20%-2.80%之间。各行排肥量一致性变异系数在0.30%-0.67%之间,播种施肥电子监视仪能够正确判断出异常工作状态的肥管序号及空堵等异常情况。6.颗粒肥料质量流量测量系统田间性能试验设计了颗粒肥料质量流量测量系统。通过秋施肥田间试验验证,排肥管的测量排肥量与实际排肥量的变化趋势一致,平均误差为8.58%,各排肥管道测量值的变异系数为0.91%,2条垄施肥量的变异系数为0.25%,空堵试验报警准确率为98.75%。更多还原

【Abstract】 According to the requirement of fertilizer application quantity measurement in agricultural production,a particle fertilizer flow detection system was designed based on Microwave Doppler effect.By studying the relation of Microwave Doppler signal between the frequency,concentration and the mass flow rate of particle fertilizer,the paper analyzes the algorithm of filter and denoising,frequency band refinement,threshold spectrum peak searching and so on,and optimizes the system to realize the application of Microwave Doppler method in agricultural fertilization.The real-time monitoring of granular fertilizer flow in fertilization operation provides theoretical and data support for precision fertilization,which is of great significance for promoting the development of mechanization and automation of precision fertilization.In this paper,theoretical analysis,algorithm research,model improvement and experimental treatment are used to study the particle fertilizer mass flow measurement.1.Analyze the physical and mechanical properties of the three granular fertilizersTaking diammonium phosphate,urea and nitro-potassium compound fertilizer as the research object,physical and mechanical properties of fertilizer particles were measured by experiments.The sphericity of the three kinds of granular fertilizers is more than 80%,the maximum moisture content of the granular fertilizers is not more than 2.35%,the maximum particle density is 1.532g/cm3,the maximum volume density is 1.679g/cm3,and the maximum resting Angle is 38.488°.The moisture content of granular fertilizer is inversely proportional to the stiffness coefficient and crushing force.2.Construct the relationship between the Doppler echo signal and the falling speed of the granular fertilizer and the particle concentration of the fertilizer discharge pipeAccording to the frequency and energy information characteristics contained in the Doppler echo signal,the relationship between the frequency and the falling speed of granular fertilizer,the power and the particle concentration of the fertilizer discharge pipe is obtained,and the mass flow model of granular fertilizer is determined.Through the comparative analysis of the microwave Doppler signal spectrum algorithm,the Zoom-FFT complex modulation refinement algorithm and the periodic graph method(direct method)are used to obtain the concentration parameters of the fertilizer particles.3.Structure design of granular fertilizer flow measurement device and filtering and noise removal of microwave Doppler echo signalThrough the bench test of the granular fertilizer flow detection device,the microwave Doppler echo signal is collected,and the wavelet threshold denoising method that selects EMD decomposition and retains the modal aliasing component is retained to retain the smooth curve of the effective echo signal characteristics.The correlation coefficient R of the filtered denoising signal is 8.693,the signal-to-noise ratio is 0.962,and the relative energy ratio is 0.049.4.Microwave Doppler signal threshold spectrum peak search and bench testAiming at the phenomenon of spectrum aliasing,fence phenomenon and spectral line leakage existing in the spectrum signal of fertilizer quantity,in the process of Zoom-FFT complex modulation refinement,the Nuttall(4 items,3rd order)window function with good side lobe effect performance is selected To reduce the error of spectrum analysis.Threshold spectrum peak search is used to obtain the average falling speed of granular fertilizer,and the power spectrum density is used to calculate the inverse relationship between the falling speed and concentration of granular fertilizer at different measuring heights in the fertilizer discharge pipe.5.Single-channel and multi-channel fertilizer row bench testThrough the 2F-12 type variable granular fertilizer test bench,the single and mixed varieties of granular fertilizer discharge experiments were completed.By modifying the empirical model parameters,the relative error between the measured value and actual value of granular fertilizer quality is reduced to between 0.20% and 2.80%.The coefficient of variation of the consistency of fertilizer discharge in each row is between 0.30% and 0.67%,and the electronic monitor for sowing and fertilization can correctly determine the abnormal conditions of the fertilizer pipe number and empty blockage in abnormal working conditions.6.Field performance test of granular fertilizer mass flow measurement systemA mass flow measurement system for granular fertilizers is designed.Through the field experiment of autumn fertilization,the measured fertilizer discharge rate of the fertilizer discharge tube is consistent with the actual fertilizer discharge rate,the average error is 8.58%,the coefficient of variation of the measured value of each fertilizer discharge tube is 0.91%,The coefficient of variation is 0.25%,and the alarm accuracy of the empty block test is 98.75%.更多还原