Inductive coupling gap compensation

Abstract

A first inductive element including a plurality of first subcoils, each first subcoil characterized at least in part by a geometry that comprises a winding direction and a physical size is provided. The plurality of first subcoils are in electrical communication with each other, and the geometry of each first subcoil is selected to reduce a variation in an inductive coupling between the first inductive element and a second inductive element when a gap between the first inductive element and the second inductive element varies. A method of vehicle wireless power charging using the above system is also provided.

1 . A vehicle wireless power charging system, comprising:
 a controller configured to execute instructions on a non-transitory computer-readable data storage medium;   a transfer coil apparatus, wherein the transfer coil apparatus has minimal coupling variation over a wide variation of a gap due to a combination of the coupling of a plurality of subcoils without adjusting current settings in an electric inverter supplying AC power;   wherein the transfer coil apparatus comprises:   two inductive elements magnetically coupled together, the two inductive elements comprising (i) a first inductive element that is a wireless power transmitter, and (ii) a second inductive element that is a wireless power receiver;   wherein the first inductive element is comprised of a plurality of first subcoils in electrical communication with each other, each first subcoil characterized at least in part by a geometry comprising a winding direction, a number of turns, and a physical size;   wherein at least one first subcoil is wound in a first direction (clockwise), at least one first subcoil is wound in a second direction that is opposite to the first direction (counter-clockwise), the locations of the plurality of first subcoils are fixed relative to each other, the physical size of the plurality of first subcoils are fixed, the physical size of the plurality of first subcoils are substantially different;   wherein the second inductive element is comprised of a plurality of second subcoils in electrical communication with each other, each second subcoil characterized at least in part by a geometry comprising a winding direction, a number of turns, and a physical size;   wherein the geometries of the first subcoils of the first inductive element are selected to reduce the variation in coupling between the first inductive element and the second inductive element as a function of a gap between each of the first subcoils and the second inductive element, the coupling defined as k(G,φ)=C a k a (G,φ)+C b k b (G,φ); where C a  and C b  are constants whose values depend on intrinsic properties of each subcoil when planes on which the first and second inductive elements lie are substantially parallel; and   the centers of the first and second inductive elements in X and Y directions are at a fixed distance smaller than the largest physical size of either inductive element; and a Z direction gap between the first and second inductive elements varies over a large distance; and   wherein the controller is in communication with first inductive element and with second inductive element.   
     
     
         2 . A vehicle wireless power charging method, comprising the steps of:
 executing instructions, by a controller, on a non-transitory computer-readable data storage medium;   statically optimizing inductive coupling between two inductive elements over a wide range of gaps in a wireless power transfer system without adjusting a current settings in an electric inverter supplying AC power;   forming a plurality of first subcoils, each first subcoil characterized at least in part by an original geometry that comprises a winding direction, number of turns, and a physical size;   providing a second inductive element;   determining the couplings between each of the first sub coils individually and the second inductive element as a function of a gap between each of the first subcoils and the second inductive element; the coupling defined as k(G,φ)=C a k a (G,φ)+C b k b (G,φ); where C a  and C b  are constants whose values depend on intrinsic properties of each subcoil;   adjusting the geometry of at least one of the first subcoils to a modified geometry, based on the coupling functions;   electrically interconnecting the plurality of first subcoils to form a first inductive element, wherein the winding directions of at least two of the plurality of first subcoils are opposite;   communicating, by the controller, with the first inductive element and with the second inductive element and;   achieving a reduced variation in coupling between the first inductive element and the second inductive element when the gap varies, by using the first subcoil modified geometry in place of the original geometry through the entire range of gaps.   
     
     
         3 . A vehicle wireless inductive power charging system, comprising:
 a controller configured to execute instructions on a non-transitory computer-readable data storage medium;   two inductive elements magnetically coupled together, the two inductive elements comprising (i) a first inductive element that is a wireless power transmitter, and (ii) a second inductive element that is a wireless power receiver;   wherein the first inductive element is comprised of a plurality of first subcoils in electrical communication with each other, each first subcoil characterized at least in part by a geometry comprising a winding direction, a number of turns, and a physical size;   wherein at least one first subcoil is wound in a first direction (clockwise), at least one first subcoil is wound in a second direction that is opposite to the first direction (counter-clockwise), the locations of the plurality of first subcoils are fixed relative to each other; the physical size of the plurality of first subcoils are fixed; the physical size of the plurality of first subcoils are substantially different;   wherein the second inductive element is comprised of a plurality of second subcoils in electrical communication with each other, each second subcoil characterized at least in part by a geometry comprising a winding direction, a number of turns, and a physical size;   wherein the controller is in communication with first inductive element and with second inductive element;   wherein the geometries of the first subcoils of the first inductive element are selected to reduce the variation in coupling between the first inductive element and the second inductive element when the planes on which the first and second inductive elements lie are substantially parallel and the centers of the first and second inductive element in X and Y directions are at a fixed distance smaller than the largest physical size of either inductive element, and a Z direction gap between the first and second inductive elements varies over a large distance; and   wherein a power source is connected to the input of an electric inverter, the wireless power transmitter is connected to the output of the electric inverter, the wireless power receiver is connected to the input of a rectifier; a load is connected to the output of the rectifier; and power from the source is transferred through the inverter, magnetic coupling, and rectifier, to the load, and current settings of the electric inverter are not adjusted.