There exist some problems that the water content of the test object cannot be reflected in real time. The detection time is too long, and the heating measurement method destroys the seed tissue for the traditional measurement of the water content of the seed. In this paper, a structure of single excitation coil to double receiving coils is proposed to measure the water content of the seed via electromagnetic induction. The relative permittivity of the seed can be obtained by the relationship between the amplitude ratio and the water content of the seed. First of all, according to the electromagnetic field theory, the functional relationship between the amplitude ratio of the electromotive force amplitude signals of the two receiving coils and the water content of the seed is established. Secondly, fifty sets of theoretical values of the mentioned model can be obtained through simulation analysis. Finally, comparative tests are carried out by using soybean seeds. The experimental results preliminarily verify the feasibility of the electromagnetic measurement method of the water content of the seed. The advantage of the proposed method is that the measurement of the water content of the seed is non-contacting.
Abstract-Magnetic resonant wireless power transfer (WPT) is an emerging technology that may create new applications for wireless power charging. However, low efficiency resulting from the change of the transfer distance is a main obstructing factor for promoting this technology. In this paper, a method of fast tracking optimum efficiency is proposed. The input impedance value is obtained by measuring the input current. Then the transfer distance is estimated by the input impedance value. The optimum load resistor is obtained under a given transfer distance. In addition, the extended Lmatching network is proposed in order to automatically adjust the load resistor. The key parameters of the matching network are also given. The optimum efficiency can be fast tracked by the proposed method as the transfer distance varies. The WPT system and the extended L-matching network are designed. Simulated and experimental results validating the proposed method are given.
In the installation of a dynamic wireless power transmission system of rail transit, the distance change among coils causes large power loss under high power conditions. Due to the limitation of detection surface and Doppler effect as well as other deficiencies, the traditional ranging methods cannot be adapted to fast, continuous, and large-area dynamic ranging in the wireless power transmission of rail transit. Therefore, the paper proposes a single coil dynamic wireless power efficiency optimization method based on electromagnetic induction for the first time. The distance between the transmitter and receiver is taken as the intermediate quantity, and the relationship between the detection coil amplitude and the wireless power transmission efficiency is constructed. Firstly, based on electromagnetic field theory, a quantitative relationship among the detection coil amplitude, wireless power transmission efficiency, and coil distance is established. Then detection experimental platform is designed. Finally, relevant experiments are accomplished through the established experimental platform. The experimental results show that for the area with low power transmission efficiency on the whole dynamic wireless power transmission line, relevant ranging data can be obtained by detecting the amplitude.
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