Research On Multi-direction Positioning Device For Wireless Power Transfer Of Electric Vehicle With Symmetrical Auxiliary Coil

With the proposal of the carbon peaking and carbon neutrality goals,wireless power transfer(WPT)has received extensive attention from more and more experts and scholars for its unique energy transmission form,green and environmental protection,safety,and adaptability.Hence,to strike a balance between economic development and green travel,electric vehicles with wireless charging have become one of the first choices for future transportation.An important study of electric vehicle wireless power transfer systems is detecting the secondary-side coil,which is vital evidence to determine whether the vehicle is in the effective charging area.However,most detection approaches based on the sensor will reconstruct the vehicle structure,which encounters the challenges such as being difficult to adapt to various vehicles,having limited applications based on the specific magnetic coupler,and affecting the operation of the primary-side coil.Driven by the mentioned problems,we design a novel triple-U auxiliary coil with an equilateral triangle structure.In addition to the advantage of unchanging the structure of the secondary-side coil,the designed triple-U auxiliary coil is able to fulfill the requirements of different positioning heights.Besides,the triple-U auxiliary interferes with the operation of the primary-side coil just to a limited extent since the magnetic coupling between these two coils is eliminated thanks to the specific structure of the triple-U auxiliary coil.Based on a WPT system with the proposed triple-U auxiliary coil,a tailored positioning and direction-guided approach are proposed.This approach is capable of reaching the high-precision detection of the secondary coil.Meanwhile,it manages to guide the secondary-side coil to the desired area that is perfectly aligned with the primary-side coil.First of all,after analyzing and comparing the magnetic field distribution characteristics of the common used coils,we pick the spiral coil with high longitudinal offset tolerance and satisfactory offset sensitivity as the auxiliary coil.Meanwhile,we innovatively designed a triple-U auxiliary coil with an equilateral triangle structure to improve its horizontal and vertical coverage of the magnetic field.By modeling the multi-degree positioning system with the triple-U auxiliary coil,we deduced the analytic relationship between mutual inductance,relative position and the load voltage.And we analyzed the influence of the auxiliary coil and its parameters on the system transmission performance and positioning results.Thus,the effectiveness of the auxiliary structure and its positioning approach is explained through theoretical analysis.Then,we introduce the proposed triple-U auxiliary coil into the magnetic coupler composed of the rectangular coil and the double-D coil,respectively,to illustrate the accurate and fuzzy identification area corresponding to the different secondary-side coils.Furthermore,combined with the mutual inductance trajectory under the different secondary-side coils,a secondary-side coil positioning and direction-guided approach are proposed to assist it to enter the effective charging area more conveniently.Eventually,we give the detailed design method of the hardware and software required by the device,and a prototype of the EV’s multi-direction wireless charging positioning system with the triple-U auxiliary coil is established to verify the feasibility of positioning and the accuracy of the direction-guided based on the proposed method.Experiment results indicate that the proposed triple-U auxiliary structure is suitable for a variety of typical magnetic coupler.And the maximum recognition range reaches 300mm×400mm and400mm×300mm,when the secondary-side coil is the rectangular and double-D coil,respectively.Moreover,in both situations,the maximum positioning height achieves250 mm.