A Study On Electromagnetic Wave Detection For Density Distribution Of Grain Pile Under Water Balance

Storing a certain amount of grain is an important measure to deal with food crisis forgovernment, and also a powerful support to maintain social stability and promote theeconomic development. At present, the information of grain amount gotten from nationalgrain depots is still obtained through manual test method, and we still lack the effecttechnological means for monitoring grain amount automatically. In China, there are largeamount of grain depots, the automatically monitor to grain amount has been becoming aproblem need to be resolved urgently.The traditional grain amount detection is in the form of sensor network, but thetechnology is still in the primary stage. The technology has many shortcomings which limitsits application. These problems include inferior precision, high costs and difficultMaintenance. In this paper, we proposed a method that using very high frequency(VHF)electromagnetic wave detects grain density, which can make up some shortages of sensor tosome extent. The detailed research content and results are as follow:(1) we studied the propagation characteristic of electromagnetic wave in grain pile, andproposed a technology route that using ground penetrating radar(GPR) detects grain pile, andprovided an implementation plan. We also studied the reflection and refraction feature aselectromagnetic wave in grain pile, and on this basis, proposed a forward model thatpropagating in grain for electromagnetic wave, and discussed the construction method of themodel.(2)We analyzed the relationship between density and moisture in grain pile underreaching water balance, and found the high consistency of density and moisture. Based on thehigh sensibility of dielectric constant to water, we proposed a method using electromagneticwave detects moisture and density of grain pile based on dielectric constant, and also give analgorithm called layer-by-layer reverse.(3) Based on analyzing dielectric properties of grain, we studied the detection method todielectric constant in laboratory using capacitance method. And use Least Squares and linearregression method to infer the dielectric–moisture and dielectric–density model for wheat.(4) Proposed a train of thought and scheme applying radar topographic imaging intooutside detection for granary. Studied the main method of ray tracing–wave front method,and do a correction for it by using travel time equation to verify refraction point. We also analysis the equation of trivial time topographic equation and attenuation topographicequation. And at last, in a test granary, we adopted LSQR method to reconstruct the image ofan abnormal area in the granary, which proved that the improved wave front method has thebetter effect for reconstructing image and the radar topographic imaging is useful and helpfulfor detecting abnormal area in granary.The method we proposed in this paper is an integration of many technologies such asradar technology, information processing technology and image processing technology. Andat the same time, we also have done many beneficial explorations in some theory problems. Inshort, the method in the paper can solve some shortcomings of sensor and displays a new pathfor detecting the grain amount automatically.