Measurement System Of Mass Flow Rate Of Granular Fertilizer Based On Microwave Doppler Effect

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%.