| As a powerful tool for energy conservation,emission reduction and new energy consumption,electric vehicles have become the focus of attention of the current society.Electric vehicle wireless charging technology has also won the favor of users and enterprises because of its flexibility,reliability and convenience in recent years.In the process of wireless charging of electric vehicles,the alignment between transmitting and receiving coupling mechanism(coils)will seriously affect the performance indexes such as charging power and efficiency.How to realize coil alignment has become one of the technical bottlenecks in the development of electric vehicle wireless charging technology.In order to solve this problem,the positioning technology of electric vehicle wireless charging coil came into being.It detects the relative position between the coils by certain means,prompting the driver or automatic driving system to adjust the attitude of the vehicle.It is of great significance to the development and application of electric vehicle wireless charging technology.This thesis focuses on the research on the positioning technology of wireless charging coil of electric vehicle,focusing on exploring the mechanism of coil positioning technology based on magnetic field analysis,improving the accuracy of coil positioning system and expanding the dimension of coil positioning system.The main work is as follows:The positioning theory and model of electric vehicle wireless charging coil are studied,and the circuit characteristics of electric vehicle wireless charging system and the magnetic field characteristics of unipolar coil are analyzed.The basic working principle of electric vehicle wireless charging coil positioning system based on magnetic field detection is studied.On this basis,the basic positioning equation of coil positioning system composed of four detection coils is proposed,which theoretically proves the feasibility of coil positioning by detecting space magnetic field.Aiming at the problem that the accuracy of the existing coil positioning system is limited,a two degree of freedom positioning method of electric vehicle wireless charging coil based on four detection coils is proposed.The mesh-based positioning algorithm based on the magnetic field coupling function is constructed,and the mapping function from the induced voltage of the detection coil to the two-dimensional position(x,y)of the receiving coil is deduced.The effectiveness of the proposed positioning algorithm is proved by simulation,and the precise positioning of two degrees of freedom at the centimeter level of the wireless charging coil of electric vehicle is realized.Aiming at the influence of angle offset between coils on coil positioning algorithm,a three degree of freedom positioning method of electric vehicle wireless charging coil based on Kriging magnetic field reconstruction is studied.The reason why the traditional two degree of freedom positioning algorithm fails when the receiving coil deflects is analyzed,and the gyroscope is introduced into the four detection coils positioning system.The coil positioning equation with three degrees of freedom is established,and a method to solve the complex nonlinear coil positioning equation by discretizing the magnetic field distribution function is proposed.The high-precision magnetic field is reconstructed by Kriging interpolation to improve the accuracy of the solution of the discrete positioning equation.And the influence of interpolation sampling points on the effect of magnetic field reconstruction is studiedFinally,the hardware circuit and software architecture of the electric vehicle wireless charging coil positioning prototype are designed and manufactured.And the experimental platform of the electric vehicle wireless charging coil positioning prototype is built.The theory and simulation results are verified by experiments. |
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