The Research Of An Electromagnetic Wave Detection Theory And Method To Moisture Of Grain Pile

Foodstuffs storage security is an important part of the foodstuffs security. For along time, the monitoring to foodstuffs storage situation has been an importantproblem worried to be solved. The monitoring to humidity is an important contentfor foodstuffs security, and is one of important quality index. To know moisturecontent well may prevent foodstuffs from mildewing because of high humidity. Dueto long storage time and abundant storage foodstuffs, and if there is no advanced andquick method to detecting moisture, we can not master the circumstance of humiditydistribution and changement, which will cause the heavy losses.As far as monitoring to foodstuffs humidity to be concerned, the formerresearches have done much study works, which meet to some extent the requirementto humidity detecting. However, it is not adpte to the moisture detection of hugegrain pile, we proposed a new monitoring method using Ground PenetratingRadar(GPR) based on very high frequency(VHF) electromagnetic wave theory inthis paper. This method can meet some requirements to detecting moisture whichtriditional method can not meet. The detailed study content and inovation efforts areas follow:(1) The study on the propagation characteristic of electromagnetic wave in grainpile. From the basic theory of GPR, we studied the feasibility applied GPR todetecting to humidity to grain pile, and considering the real situation of granary,studied the its parameters setup problems. Aimming at propagation characteristic ingrain pile, mainly studied the reflection and refraction characteristic in foodstuffsmedium, and based on it, proposed a forward model and building method for thepropagation of electromagnetic wave in grain pile. In order to be propitious to DataInterpretation, studied the filter to radar clutter wave in wavelet domain, andproposed a new filter method based fuse treshold algorithm.(2) Based on the principle of refraction and reflection, we proposed a newinverting method named dielectric constant layer-by-layer method inclucingmodifying factors, to realize the detection to grain dielectric constant in a large sapcerange. Compared to triditional method, this method improved the measurementaccuracy, simplified the detecting method, enlarged the detecting range andimproved messurement effeorts. The measurement results are in normal error range.(3) An intensive study on grains dielectric property. Taking wheat for an example,we analyzed the various factors impacting wheat dielectric property, and do adetailed comparation and analysis from three sides such as temperature, frequencyand moisture content. As to the relationship between dielectric constant and moisturecontent, we proposed two models named dielectric-moisture nonlinearity model andchange Q value model based on an amount of experiments, and mainly studied thechange Q value model and its construction based system identification. At last, weevaluated the two model by experiment reults.(4) Based on the basic theory of tomography, we studied the two forward models of velocity and attenuation tomography. To inverting method of tomography, mainlystudied the method based on ray tracing theory. We also discussed many ray tracingtheories, and specially discussed the improvement to wavefront method whichadopts refraciton point verificaiton to improve tracing precision. Aimming at thedifferent circumstance when applied ray tracing to ground objects, using FDTDemulation, we analyzed the extraction of first-motion wave, and setup joint inversionmodel using velocity and attenuation tomography. We adpted LSQR algorithm toconstruct image in which the improved wavefront method is applied to improveimage quality. For large grain pile, the huge data and calculated amount of LSQRalgorithm can be overcomed by using parallel computing.In this paper, we proposed the new method including radar technology, Signaland information processing technology, Image Processing Technology and otherefforts in moisture detecting, maybe resolve the key problems related to foodstuffsmoisture detecting, and can also provide an uniform and simple platform of moisturemonitoring to large granary,which are great helpful to chinese Food storageinformation.