Abstract:
A common problem in wireless charging systems in automotive applications is alignment of the wireless power transfer transmitter and receiver units. Poor alignment leads to poor power transfer capacity and a longer charging time. Costly optical sensors and electromechanical systems may be employed to align the transmitter and receiver units. A solution to this problem is to employ a freely moveable wireless power transmitter in at least one direction that is magnetically attracted to the wireless power receiver unit in the vehicle that does not require electrically powered sensors or mechanical alignment systems.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of Patent Cooperation Treaty (PCT) application No. PCT/CA2015/050596, filed 25 Jun. 2015 and entitled METHODS AND APPARATUS FOR AUTOMATIC ALIGNMENT OF WIRELESS POWER TRANSFER SYSTEMS which in turn claims the filing date benefit of U.S. application Ser. No. 62/017,077, filed on 25 Jun. 2014. PCT application No. PCT/CA2015/050596 and U.S. application No. 62/017,077 are hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention pertains to wireless power transfer systems which transfer power wirelessly from a wireless power transmitter to a wireless power receiver. Particular embodiments provide methods and apparatus for automatic alignment of the transmitter and receiver in such wireless power transfer systems. 
       BACKGROUND 
       [0003]    Power can be wirelessly conveyed from one place to another using the Faraday effect, whereby a changing magnetic field causes an electrical current to flow in an electrically isolated secondary circuit. A form of wireless power transfer (WPT) currently in use involves magnetic inductive charging. One form of magnetic inductive charging is shown in WPT system  10  of  FIG. 1 . The  FIG. 1  WPT system  10  comprises two coils  12 ,  14  in close proximity but separated by an air gap  16 . One coil  12  of WPT system  10  acts as a wireless power transmitter and the other coil  14  acts as the receiver of wireless power. A time-varying current flows in transmitter coil  12 , which produces a time-varying magnetic field (shown as flux lines in  FIG. 1 ). This time-varying magnetic field induces current in the nearby receiver coil  14  (Faraday&#39;s law), which can then be used to charge various devices (not shown) which may be electrically connected to receiver coil  14 . 
         [0004]    In PCT application No. PCT/CA2010/000252 (published under WO/2010/096917), a magnetic-coupling technology has been described to provide a number of viable WPT systems that can be used to charge, by way of non-limiting example, batteries generally, electric (e.g. battery operated) vehicles, auxiliary batteries, electric (e.g. battery operated) buses, golf carts, delivery vehicles, boats, drones, trucks and/or the like.  FIG. 2  schematically depicts a WPT system  20  incorporating a magnetic-coupling technology of the type described in PCT/CA2010/000252. WPT system  20  comprises a wireless magnetic power transmitter  22  and a wireless magnetic power receiver  24  separated by an air gap  26 . The power transfer in WPT system  20  is via rotational magnetic coupling rather than via direct magnetic induction. In the  FIG. 2  WPT system  20 , transmitter  22  comprises a permanent magnet  22 A and receiver  24  comprises a permanent magnet  24 A. Transmitter magnet  22 A is rotated (and/or pivoted) about axis  28 . The magnetically coupled permanent magnets  22 A,  24 A interact with one another (magnetic poles represented by an arrow with notations of “N” for north and “S” for south in  FIG. 2 ), such that movement of transmitter magnet  22 A about axis causes corresponding movement (e.g. rotation and/or pivotal movement) of receiver magnet  24 A about axis  27 . The time-varying magnetic fields generated by rotating/pivoting magnets  22 A,  24 A of WPT system  20  typically has a lower frequency compared to WPT systems based on magnetic induction. The  FIG. 2  WPT system  20  transfers power most effectively when there is strong coupling between rotating/pivoting magnets  22 A,  24 A. 
         [0005]    A challenge faced by WPT systems is the alignment of the WPT transmitter and WPT receiver. When the WPT transmitter and WPT receiver are misaligned, the power transfer process loses efficiency—i.e. it takes longer to transfer a given amount of power/charge. In some cases, where misalignment is extreme, power transfer may be ineffective—i.e. no measurable power/charge transfer occurs. Alignment of the WPT transmitter and WPT receiver can be difficult, for example, in automotive applications (e.g. for charging a vehicle battery). In such applications, the WPT receiver is typically located on the underside of a vehicle (e.g. out of view of the driver of the vehicle) and a WPT transmitter is located on the ground. In such circumstances, alignment of the WPT transmitter and WPT receiver can be difficult and can reduce power transfer efficiency and/or efficacy. A number of factors can exacerbate the challenges associated with alignment of the WPT transmitters and WPT receivers. For example, such exacerbating factors may include the relatively small size of the WPT transmitters/receivers, vehicle to vehicle dimensional variations and limited capacity for the vehicle driver to see the WPT receiver and/or the WPT transmitter. 
         [0006]    The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the description and a study of the drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]    Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive. 
           [0008]      FIG. 1  is a schematic illustration of a prior art magnetic induction based WPT system comprising a WPT transmitter coil and a WPT receiver coil in close proximity. 
           [0009]      FIG. 2  is a schematic illustration of two magnetically-coupled rotating/pivoting magnets in a prior art magnetically-coupled WPT system. 
           [0010]      FIG. 3  schematically depicts an apparatus for automatic alignment of a WPT system according to a particular embodiment. 
           [0011]      FIG. 4  schematically depicts the  FIG. 3  apparatus for automatic alignment of a WPT system used as a vehicle charging system according to a particular embodiment. 
           [0012]      FIG. 5  depicts a close-up view of a moveable WPT transmitter installed on a parking curb according to one embodiment. 
           [0013]      FIG. 6  depicts a close-up view of a moveable WPT transmitter installed on a parking curb according to another embodiment. 
       
    
    
     DESCRIPTION 
       [0014]    Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense. 
         [0015]    One aspect of the invention provides an automatically aligning wireless power transfer (WPT) system. In some embodiments, a moveably mounted wireless power transmitter (also referred to as a WPT transmitter, a wireless power transmitting unit and/or a wireless power transmitting device) comprises a transmitter magnetic system for creating a transmitter magnetic field. The WPT transmitter may be moveably mounted (e.g. mounted to a suitable support by an adjustable mounting mechanism which permits movement of the WPT transmitter relative to the support). In some embodiments, the WPT transmitter is free to move linearly (e.g. linear translational movement). In some embodiments, the WPT transmitter is free to move translationally within a plane. In some embodiments, the WPT transmitter is free to move translationally in a plane and out of the plane. In some embodiments, the WPT transmitter is additionally or alternatively free to move pivotally about one or more pivot axes. The transmitter magnetic system may comprise one or more permanent magnets and/or one or more magnetic field generating coils. The WPT system may also comprise a wireless power receiver (also referred to as a WPT receiver, a wireless power receiving unit, and/or a wireless power receiving device) which may comprise a receiver magnetic system for interacting (e.g. magnetically interacting) with the transmitter magnetic field. The receiver magnet system may comprise one or more permanent magnets and/or one or more magnetic field generating coils. Examples of such transmitter magnetic systems, receiver magnetic systems and interactions therebetween are described in PCT application No. PCT/CA2010/000252 and PCT application No. PCT/CA2015/050327, both of which are hereby incorporated herein by reference. The interaction between the transmitter magnetic field and the receiver magnetic system may cause wireless power transfer from the moveably mounted WPT transmitter to the WPT receiver and may cause movement (e.g. translational and/or pivotal movement) of the moveably mounted WPT transmitter from a first position to a second position. When the WPT transmitter is in the second position, the temporal rate of energy transfer from the WPT transmitter to the WPT receiver may be greater than the temporal rate of energy transfer from the WPT transmitter to the WPT receiver when the WPT transmitter is at the first position. 
         [0016]    Another aspect of the invention provides a method for automatically aligning a wireless power transfer (WPT) system. The method comprises providing a moveably mounted WPT transmitter comprising a transmitter magnetic system for creating a transmitter magnetic field. The method comprises receiving a WPT receiver in a vicinity of the moveably mounted WPT transmitter, the WPT receiver comprising a receiver magnetic system for interacting with the transmitter magnetic field. The method also comprises transferring power from the moveably mounted WPT transmitter to the WPT receiver via the interaction between the receiver magnetic system and the transmitter magnetic field; and causing movement (e.g. translational and/or pivotal movement) of the moveably mounted WPT transmitter from a first position to a second position via the interaction between the receiver magnetic system and the transmitter magnetic field. When the WPT transmitter is in the second position, the temporal rate of energy transfer from the WPT transmitter to the WPT receiver may be greater than the temporal rate of energy transfer from the WPT transmitter to the WPT receiver when the WPT transmitter is at the first position. 
         [0017]    Another aspect of the invention provides an automatically aligning wireless power transfer (WPT) system. The WPT system comprises: a wireless power transmitter (also referred to as a WPT transmitter, a wireless power transmitting unit and/or a wireless power transmitting device) moveably mounted to a support by an adjustable mounting mechanism which permits movement of the WPT transmitter (e.g. relative to the support); and a wireless power receiver (also referred to as a WPT receiver, a wireless power receiving unit, and/or a wireless power receiving device). The WPT transmitter is magnetically attracted to the WPT receiver, thereby forcing the WPT transmitter to move (e.g. translationally and/or pivotally) from a first position to a second position. In some embodiments, the WPT receiver is supported by the adjustable mounting mechanism for linear movement along a first axis. In some embodiments, the magnetic attraction of the WPT transmitter to the WPT receiver forces the WPT transmitter from the first position to the second position along the first axis. In some embodiments, the WPT receiver is supported by the adjustable mounting mechanism for linear movement along a first axis and a second axis. In some embodiments, the magnetic attraction of the WPT transmitter to the WPT receiver forces the WPT transmitter from the first position to the second position along the first and second axes. When the WPT transmitter is in the second position, the temporal rate of energy transfer from the WPT transmitter to the WPT receiver may be greater than the temporal rate of energy transfer from the WPT transmitter to the WPT receiver when the WPT transmitter is at the first position. 
         [0018]    Another aspect of the invention provides a method for automatically aligning a wireless power transfer system. The method comprises providing a WPT transmitter supported for movement within a parking region. The method comprises receiving a WPT receiver within the parking region. The method also comprises magnetically coupling the WPT receiver to the WPT transmitter. The method also comprises forcing the WPT transmitter, by the magnetic coupling of the WPT receiver to the WPT transmitter, to move (e.g. translationally and/or pivotally) from a first position to a second position. In some embodiments, the WPT receiver is supported for linear movement along a first axis. In some embodiments, the magnetic coupling of the WPT transmitter to the WPT receiver forces the WPT transmitter from the first position to the second position along the first axis. In some embodiments, the WPT receiver is supported for linear movement along a first axis and a second axis. In some embodiments, the magnetic coupling of the WPT transmitter to the WPT receiver forces the WPT transmitter from the first position to the second position along the first and second axes. When the WPT transmitter is in the second position, the temporal rate of energy transfer from the WPT transmitter to the WPT receiver may be greater than the temporal rate of energy transfer from the WPT transmitter to the WPT receiver when the WPT transmitter is at the first position. 
         [0019]    In some embodiments, a WPT transmitter is moveably mounted to a support (e.g. by an adjustable mounting mechanism) to permit movement of the WPT transmitter (e.g. relative to the support). A WPT receiver may be moved into the vicinity of the WPT transmitter and the WPT transmitter may be magnetically attracted to (or may otherwise interact with) the WPT receiver such that the WPT transmitter is forced to move (e.g. by translationally and/or pivotally adjusting the adjustable mounting mechanism) from a first position to a second position. In some embodiments, this force may be generated by the interaction between a transmitter magnetic field (generated by a transmitter magnetic system of the WPT transmitter) and a receiver magnetic system of the WPT receiver. When the WPT transmitter is in the second position, the temporal rate of energy transfer from the WPT transmitter to the WPT receiver may be greater than the temporal rate of energy transfer from the WPT transmitter to the WPT receiver when the WPT transmitter is at the first position. 
         [0020]    In some embodiments, the interaction between the transmitter magnetic field and the receiver magnetic system which causes wireless power transfer from the moveably mounted WPT transmitter to the WPT receiver is stronger (e.g. relatively strong magnetic coupling generating relatively strong forces) when the WPT transmitter is in the second position as compared to when the WPT transmitter is in the first position. Accordingly, when the WPT transmitter is in the second position, the forces associated with the interaction of the transmitter magnetic field and the receiver magnetic system which cause the wireless power transfer may be greater than the forces associated with the interaction of the transmitter magnetic field and the receiver magnetic system which cause the wireless power transfer when the WPT transmitter is at the first position. When the WPT transmitter is in the second position, the WPT transmitter may be said to be closer to, or relatively more aligned with, the WPT receiver than when the WPT transmitter is in the first position. In this respect, the expressions closer, relatively more aligned with and similar terms may be understood to correspond to one or more of: a greater temporal rate of energy transfer when the WPT transmitter is in the second position relative to when the WPT transmitter is in the first position; greater magnetic coupling in the interaction between the transmitter magnetic field and the receiver magnetic system which causes wireless power transfer from the moveably mounted WPT transmitter to the WPT receiver when the WPT transmitter is in the second position as compared to when the WPT transmitter is in the first position; and greater forces in the interaction between the transmitter magnetic field and the receiver magnetic system which causes wireless power transfer from the moveably mounted WPT transmitter to the WPT receiver when the WPT transmitter is in the second position as compared to when the WPT transmitter is in the first position; and greater forces. 
         [0021]    The moveably mounted WPT transmitter may be mounted to a support by an adjustable mounting mechanism. The adjustable mounting mechanism may comprise a linearly adjustable mounting mechanism which permits corresponding linear movement of the WPT transmitter (e.g. in one or more directions along a first linear axis) relative to the support. In some embodiments, the adjustable mounting mechanism may comprise a two-dimensionally adjustable mounting mechanism which permits corresponding two-dimensional movement of the WPT transmitter (e.g. along first and second non-parallel axes) relative to the support. The first and second non-parallel axes may be generally (e.g. within engineering tolerances) orthogonal. In some embodiments, the adjustable mounting mechanism may comprise a three-dimensionally adjustable mounting mechanism which permits corresponding three-dimensional movement of the WPT transmitter (e.g. along first, second and third generally orthogonal axes). In some embodiments, the adjustable mounting mechanism may additionally or alternative comprise a pivotally adjustable mounting mechanism which permits corresponding pivotal movement of the WPT transmitter about one or more axes (e.g. about first, second and third generally orthogonal axes). In general, the adjustable mounting mechanism may permit movement of the WPT transmitter with as many as six degrees of freedom (e.g. three translational degrees of freedom and three rotational/pivotal degrees of freedom) and any sub-combination thereof. 
         [0022]    Another aspect of the invention provides an automatically aligning, magnetically-coupling wireless power transfer (WPT) system. The WPT system comprises: a power control device mounted in a wireless charging station for providing electrical power to a wireless power transmitting device; at least one wireless power transmitting device connected to the power control device and mounted in a parking region; a wireless power receiver mounted in a mobile platform (e.g. in a vehicle); and a mechanical structure/system (e.g. an adjustable mounting mechanism) onto which the wireless power transmitter device is further mounted such that the wireless power transmitter can move (e.g. by adjustment of the mechanical structure/system) freely (e.g. with minimal friction) in the absence of electrical power in at least one direction to align (e.g. become relatively more aligned with) with the wireless power receiver mounted in the mobile platform. 
         [0023]      FIG. 3  schematically depicts an automatically aligning wireless power transfer (WPT) system  100  according to a particular embodiment. WPT system  100  comprises a moveably mounted WPT transmitter  130  for wirelessly transferring power from a power source  140  to a WPT receiver  150  (schematically shown in  FIG. 3  using dashed lines). Movably mounted WPT transmitter  130  may be moveably mounted to a support  112  by an adjustable mounting mechanism  114  which permits movement of WPT transmitter  130  in a movement region  118  (e.g. in a parking region such as a parking space). In the illustrated embodiment, support  112  comprises the ground  112 A together with one or more (e.g. two) rails  110  oriented along an x-axis. In cases where movement region  118  comprises a parking region or parking space, the x-axis direction in which rails  110  are extended may comprise the short axis of the parking space which may be generally parallel to the axles of a car parked in the parking region. In general, support  112  may comprise any suitable structure (including the ground, a table, a platform, scaffolding and/or the like) relative to which adjustable mounting mechanism  114  may move. 
         [0024]    In the illustrated embodiment, adjustable mounting mechanism  114  comprises one or more (e.g. two) rails  120  oriented along the y-axis which support WPT transmitter  130 . In cases where movement region  118  comprises a parking region or parking space, the y-axis direction may comprise the long axis of the parking region which may be generally parallel to the long axis of a car parked in the parking region. The y-axis may be non-parallel to the x-axis. In some embodiments, the y-axis may be generally (within engineering tolerances (e.g. +/−2%)) orthogonal to the x-axis. Adjustable mounting mechanism  114  permits y-oriented rails  120  to move linearly along x-oriented rails  110  (e.g. y-oriented rails  120  are capable of moving linearly back and forth in directions oriented along the x-axis relative to x-oriented rails  110 ). Since y-oriented rails  120  support WPT transmitter  130 , adjustment of y-oriented rails  120  along the x-axis causes corresponding adjustment of the position of WPT transmitter  130  in directions aligned with the x-axis relative to x-oriented rails  110 . In the illustrated embodiment, adjustable mounting mechanism  114  permits WPT transmitter  130  to move linearly along y-oriented rails  120  (e.g. WPT transmitter  130  is capable of moving linearly back and forth in directions oriented along the y-axis relative to y-oriented rails  120 ). Together, the adjustable position of y-oriented rails (in x-axis directions relative to x-oriented rails  110 ) and the adjustable position of WPT transmitter  130  (in y-axis directions relative to y-oriented rails  120 ) permit movement of WPT transmitter  130  in two-dimensions relative to support  112  within movement region  118 . 
         [0025]    In some embodiments, rails  110 ,  120 , the under-carriage of WPT transmitter  130  or any other part of adjustable mounting mechanism  114  may additionally or alternatively comprise tracks, guides, any other type of sliding mechanism, any other type of rolling mechanism and/or the like which permits adjustable movement of WPT transmitter  130  relative to support  112 . Adjustable mounting mechanism  114  may comprise cables, guides, wheels, pulleys, gears, pistons, bearings (such as, for example, slider bearing, ball bearings, linear bearings and/or the like) and/or the like (not expressly shown in the schematic  FIG. 3  illustration) to facilitate relative movement between rails  120  and rails  110 . Adjustable mounting mechanism  114  may comprise any combination of such components. In some embodiments, adjustable mounting mechanism  114  may be modified to provide suitable mechanisms for providing additional degrees of freedom to the moveability of WPT transmitter  130 . For example, such additional degrees of freedom may include translation in the z-axis direction and/or pivotal movement about any of the x, y and z-axes. 
         [0026]    WPT system  100  comprises a power source  140  (also referred to as an external power control device) to provide electrical power from to WPT transmitter  130 . WPT transmitter  130  may comprise a transmitter magnetic system (not expressly shown) which creates a corresponding transmitter magnetic field. For example, the transmitter magnetic system may comprise one or more permanent magnets which move with power from source  140  to create a corresponding transmitter magnetic field and/or the transmitter magnetic system may comprise one or more coils which receive current from power source  140  to generate a corresponding transmitter magnetic field. WPT receiver  150  comprises a receiver magnetic system (not expressly shown) which may comprise one or more permanent magnets and/or one or more magnetic field generating coils. The receiver magnetic system interacts (e.g. magnetically interacts) with the transmitter magnetic field. The interaction between the transmitter magnetic field and the receiver magnetic system may cause wireless power transfer from WPT transmitter  130  to WPT receiver  150 . The interaction between the transmitter magnetic field and the receiver magnetic system may also cause movement of WPT transmitter  130  (via corresponding adjustment of adjustable mounting mechanism  114 ). In particular, magnetic interaction forces may force WPT transmitter to move from a first position to a second position. 
         [0027]    When WPT transmitter  130  is in the second position, WPT transmitter  130  may be closer to WPT receiver  150  than when WPT transmitter  130  is in the first position. For example, in the case of the  FIG. 3  schematic illustration WPT transmitter  130  may move in the negative x-direction and/or in the negative y-direction so that WPT transmitter  130  is closer to WPT receiver  150 . When WPT transmitter  130  is in the second position, WPT transmitter  130  may be more aligned to WPT receiver  150  than when WPT transmitter  130  is in the first position. The temporal rate of energy transfer from the WPT transmitter to the WPT receiver may be greater when the WPT transmitter is at the second position than the temporal rate of energy transfer from the WPT transmitter to the WPT receiver when the WPT transmitter is at the first position. 
         [0028]    Depending on the size of the magnets (and/or coils) in transmitter magnetic system of WPT transmitter  130 , x-axes rails  110  may be made with x-axis lengths that are up to 2.5 times the length of the magnets and/or the axial dimensions of the coils and down to the size of the enclosure housing WPT transmitter  130 . Similarly, y-oriented rails  120  may be made with y-axis lengths that are up to 4 times the width of the magnets and/or diameters of the coils and down to the size of the enclosure housing WPT transmitter  130 . System  100  may be enclosed in an optional plastic or rubberized-like protective cover or hood (not shown) to protect from rain, snow, dirt or other debris or other potential means of damage to the structure. 
         [0029]    As discussed above, in some embodiments, adjustable mounting mechanism  114  may permit WPT transmitter  130  to be moveable in directions along the z-axis (which may be orthogonal to y-axis rails  120  and x-axis rails  110  (i.e. out of the page in  FIG. 3 ). In some embodiments, movement along the z-axis is free (e.g. with minimal friction), similar to movement along rails  110 ,  120 , while in other embodiments, movement along the z-axis comprises manual or mechanical actuation such as by way of a motorized lift. In some embodiments, a proximity sensor is used to determine if WPT transmitter  130  is sufficiently close to WPT receiver  150  in the z-axis direction. If WPT transmitter  130  is not sufficiently close to WPT receiver  150  in the z-axis direction, then WPT transmitter  130  may be raised automatically or manually. In some embodiments, the entire illustrated system  100  is raised while in other embodiments, only WPT transmitter unit  130  is raised. 
         [0030]      FIG. 4  depicts the  FIG. 3  automatically aligning wireless power transfer (WPT) system  100  in use as a vehicle charging system  200  in a parking region  118 A (e.g. a parking spot) according to a particular embodiment. WPT system  100  may be the same as WPT system  100  described above in connection with  FIG. 3 , where support  112  comprises the surface  112 A under parking region  118 A and x-oriented rails  110  are rigidly mounted to surface  112 A of parking region  118 A. In the  FIG. 4  embodiment, where WPT system  100  is used as a vehicle charging system  200 , vehicle charging system  200  comprises stationary tire-stoppers  210  for stopping a vehicle in an approximately desired position in parking region  118 A. By way of non-limiting example, tire stoppers  210  may comprise parking curbs and/or the like. In some embodiments, charging system  200  may comprise other components, systems or devices for stopping a vehicle in an approximately desired position in parking region  118 A. By way of non-limiting example, such vehicle positioning systems may comprise proximity sensors, cameras, laser range finders, audible guides and/or the like. In the schematic illustration of  FIG. 4 , a vehicle  160  in parking region  118 A is schematically shown in dashed lines. The tires  180  of vehicle  160  are also shown in dashed lines in the  FIG. 4  illustration. In  FIG. 4 , vehicle  160  is shown in an idealized parking position, where the front tires  180  of vehicle  160  are immediately adjacent to tire stoppers  210 . 
         [0031]    The  FIG. 4  vehicle charging system  200  functions as follows. In the absence of a vehicle  160  equipped with a WPT receiver  150 , WPT transmitter unit  130  remains at rest and no charge is transferred. As a vehicle  160  equipped with a WPT receiver  150  (e.g. on its underside) approaches parking region  118 A (e.g. in a vicinity of WPT transmitter  130 ), the transmitter magnetic system of WPT transmitter  130  creates a transmitter magnetic field which interacts (e.g. magnetically interacts) with the receiver magnetic system of WPT receiver  150 . The interaction between the transmitter magnetic field and the receiver magnetic system may cause forces which cause the magnets of the transmitter magnetic system and the receiver magnetic system to rotate and align their magnetic fields such that their respective magnetic systems attract one another. Since WPT transmitter  130  can freely (e.g. with minimal friction) move in the x-axis and y-axis direction without using any additional electrical power, WPT transmitter  130  moves (e.g. by corresponding adjustment of adjustable mounting mechanism  114 ) from a first position to a second position. When WPT transmitter  130  is in the second position, WPT transmitter  130  may be closer to WPT receiver  150  than when WPT transmitter  130  is in the first position. When WPT transmitter  130  is in the second position, WPT transmitter  130  may be more aligned to WPT receiver  150  than when WPT transmitter  130  is in the first position. The temporal rate of energy transfer from WPT transmitter  130  to WPT receiver  150  may be greater when WPT transmitter  130  is at the second position than the temporal rate of energy transfer from WPT transmitter  130  to WPT receiver  150  when WPT transmitter  130  is at the first position. 
         [0032]    The transmitter magnetic system may be driven with an alternating current supplied by power source  140  to create a first time-varying magnetic field that interacts with the receiver magnetic system (e.g. by inducing rotation in a magnet of the receiver magnetic system of WPT receiver  150  located in vehicle  160  across a gap) to produce a second time-varying magnetic field. This interaction between WPT transmitter  130  and the WPT receiver  150  allows power to be transferred from WPT transmitter  130  to WPT receiver  150 . The transfer of power across the gap is through magnetic coupling. The second time varying magnetic field induces electrical current in coils proximate to the receiver magnetic system to provide electrical power to vehicle  160  (e.g. to the battery of vehicle  160 ). 
         [0033]      FIG. 5  depicts an automatically aligning wireless power transfer (WPT) system  300  in use as a vehicle charging system  302  adjacent to a parking curb  310  or other tire stopper  310  according to a particular embodiment. The embodiments of  FIGS. 3 and 4  comprise an automatically aligning WPT system  100  where WPT transmitter  130  is moveable freely in two-dimensions to align with WPT receiver unit  150  which may be located, for example, in the underside of an approaching vehicle. In the  FIG. 5  embodiment, WPT transmitter  130  is enclosed or located in proximity to a parking curb  310  or other type of tire stopper  310  which may provide part of the support  112 . WPT transmitter  130  of system  300  is moveably mounted (via a adjustable mounting mechanism) to one or more stationary rails  320  extending in directions generally parallel to x-axis along parking curb  310 . In the  FIG. 5  embodiment, the x-axis is generally parallel to the axles of a vehicle (not shown) parked against curb  310  and the x-axis is generally perpendicular to the long axis of a vehicle parked against curb  310 . Rail  320  may have any of the features discussed above in connection with rails  110 ,  120 . A power source  140  is further connected to WPT transmitter  130  to provide electrical power to WPT transmitter  130 . Parking curb  310  or other type of tire stopper  310  may be fabricated from concrete or other sturdy material such as plastic, rubber or other non-metallic material to protect system  300  from rain, snow, dirt or other debris or other potential means of damage to system  300 . The functionality of system  300  may be similar to that described above in connection with systems  100 ,  200 , except that system  300 , of the illustrated embodiment, provides only one degree of freedom for movement of WPT transmitter  130 . 
         [0034]      FIG. 6  depicts the  FIG. 5  automatically aligning wireless power transfer (WPT) system  300  in use as a vehicle charging system  400  in a parking region  118 A (e.g. a parking spot) according to a particular embodiment. WPT system  300  may be the same as WPT system  300  described above in connection with  FIG. 5 . In the  FIG. 6  embodiment, where WPT system  300  is used as a vehicle charging system  400 , vehicle charging system  400  comprises one or more stationary parking curbs  310  or other tire-stoppers  310  for stopping a vehicle in an approximately desired position in parking region  118 A. Tire stopping device  310  of the  FIG. 6  embodiment houses WPT system  300  and may provide part of support  112 . In some embodiments, charging system  400  may comprise other components, systems or devices for stopping a vehicle in an approximately desired position in parking region  118 A. By way of non-limiting example, such vehicle positioning systems may comprise proximity sensors, cameras, laser range finders, audible guides and/or the like. In the schematic illustration of  FIG. 6 , a vehicle  160  in parking region  118 A is schematically shown in dashed lines. The tires  180  of vehicle  160  are also shown in dashed lines in the  FIG. 6  illustration. In  FIG. 6 , vehicle  160  is shown in an idealized parking position, where the front tires  180  of vehicle  160  are immediately adjacent to curb  310 . 
         [0035]    The  FIG. 6  vehicle charging system  400  functions as follows. In the absence of a vehicle  160  equipped with a WPT receiver  150 , WPT transmitter unit  130  remains at rest and no charge is transferred. As a vehicle  160  equipped with a WPT receiver  150  (e.g. on its underside) approaches parking region  118 A (e.g. in a vicinity of WPT transmitter  130 ), the transmitter magnetic system of WPT transmitter  130  creates a transmitter magnetic field which interacts (e.g. magnetically interacts) with the receiver magnetic system of WPT receiver  150 . The interaction between the transmitter magnetic field and the receiver magnetic system may cause forces which cause the magnets of the transmitter magnetic system and the receiver magnetic system to rotate and align their magnetic fields such that their respective magnetic systems attract one another. Since WPT transmitter  130  can freely (e.g. with minimal friction) move in the x-axis direction without using any additional electrical power, WPT transmitter  130  moves (e.g. by corresponding adjustment of adjustable mounting mechanism  114 ) from a first position to a second position. When WPT transmitter  130  is in the second position, WPT transmitter  130  may be closer to WPT receiver  150  than when WPT transmitter  130  is in the first position. When WPT transmitter  130  is in the second position, WPT transmitter  130  may be more aligned to WPT receiver  150  than when WPT transmitter  130  is in the first position. The temporal rate of energy transfer from WPT transmitter  130  to WPT receiver  150  may be greater when WPT transmitter  130  is at the second position than the temporal rate of energy transfer from WPT transmitter  130  to WPT receiver  150  when WPT transmitter  130  is at the first position. 
         [0036]    The transmitter magnetic system may be driven with an alternating current supplied by power source  140  to create a first time-varying magnetic field that interacts with the receiver magnetic system (e.g. by inducing rotation in a magnet of the receiver magnetic system of WPT receiver  150  located in vehicle  160  across a gap) to produce a second time-varying magnetic field. This interaction between WPT transmitter  130  and the WPT receiver  150  allows power to be transferred from WPT transmitter  130  to WPT receiver  150 . The transfer of power across the gap is through magnetic coupling. The second time varying magnetic field induces electrical current in coils proximate to the receiver magnetic system to provide electrical power to vehicle  160  (e.g. to the battery of vehicle  160 ). 
         [0037]    Embodiments of the invention described herein may be used in any magnetically-coupled wireless charging systems for, but not limited to, electric powered automobiles, transit buses, delivery vehicles, trucks, drones, boats, golf carts or other consumer devices. Particular embodiments allow for low cost and low maintenance automatic wireless charging stations of simple construction and assembly and further encourage adoption of electric vehicle technology. 
         [0038]    As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. For example:
       Various embodiments (e.g. systems  100 ,  200 ,  300 ,  400  etc.) described herein may each include a variety of features. It should be understood that this description and the accompanying claims include additional embodiments that comprise combinations of any of the features of any of the embodiments herein.   In some instances, this description and the accompanying claims use terms generally to describe directions, orientations, shapes, relationships (e.g. equalities) and/or the like. For example, transmitter magnetic system may have a first magnetization direction that is orthogonal to a transmitter magnetization-variation direction. Such directions, orientations, shapes, relationships and/or the like should be considered to accommodate the specified directions, orientations, shapes, relationships and/or the like and/or relatively small deviations (from an operational or engineering perspective) from the specified directions, orientations, shapes, relationships and/or the like.   In some instances, this description and the accompanying claims refer to receiver magnetic systems. Where the receiver magnetic systems comprise coils, the reference to receiver magnetic system is a matter of nomenclature and doesn&#39;t necessarily mean that the receiver magnetic system driven to generate corresponding magnetic fields. In practice, the receiver magnetic system may instead have currents induced therein, which induced currents may in turn create corresponding magnetic fields.   In this description and the accompanying claims, elements (such as, by way of non-limiting example, WPT transmitters and WPT receivers) are said to overlap or align with one another in a direction or along a direction. For example, a WTP receiver may overlap or be aligned with a WPT receiver along a particular direction. When it is described that two or more objects overlap or are aligned in or along a particular direction, this usage should be understood to mean that line oriented in that particular direction could be drawn to intersect the two or more objects.   In this description, various vehicles having four wheels are described and/or depicted, however it should be understood that the invention described herein could be applied to any vehicle having any number of wheels (e.g. 1, 2, 3, 4, 5, 6 etc.) and including non-wheeled vehicles (e.g. hovercrafts, boats, planes, trains, etc.)       
 
         [0044]    While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended aspects or claims and aspects or claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations.