Abstract:
Vehicle charging apparatuses and methods connect a vehicle to an external power source, the vehicle having a battery that is capable of being charged from the external power source and having a receptacle configured to receive a plug connected to the external power source. An alignment target receives at least one visual alignment beam from a vehicle, the position of the alignment beam providing visual indication to a vehicle operator that the vehicle is properly aligned relative to the charging station. A robotic arm is mounted to a structure and has a plug at a distal end thereof, the plug interconnected to the external power source and adapted to engage the vehicle receptacle to transfer power to or from the vehicle. A module may be provided for controlling the robotic arm such that said plug engages with the vehicle receptacle when the vehicle is properly aligned to receive the plug.

Description:
FIELD 
       [0001]    This disclosure relates to coupling of vehicles to a network and/or grid external to the vehicle, and more specifically to charging stations having positioning assistance and magnetic inductive couplings used for transferring energy to and from a vehicle battery. 
       BACKGROUND 
       [0002]    An abundant supply of fossil fuels has powered the industrial revolution of the past two hundred years. The supply of those fuels is being depleted, and consideration of alternative sources of energy has become more prevalent. In addition, the burning of the carbon in those fuels has contaminated the atmosphere, oceans, and soil with carbon dioxide and other pollutants. These fossil fuels are widely used in different forms to furnish electricity, heat homes, fuel vehicles, and power commerce in general, thus complicating the search for replacements. 
         [0003]    Various alternatives are known and are being considered in some form to help displace the amount of energy produced using fossil fuels. For example, nuclear energy is an alternative source of electrical energy but suffers from high cost, difficult waste disposal, safety issues, and energy efficiency issues. Biofuels are another alternative and have the advantage that burning of such fuels does not add new carbon dioxide to the environment. Unfortunately, it is not realistic to produce enough biofuel to replace the amount of petroleum currently used. The United States National Renewal Energy Laboratory (NREL) estimates we use about 100 million barrels of ethanol a year compared to nearly 7 billion barrels of oil. Hydrogen is being explored as another alternative to traditional fossil fuels, although various technical hurdles will prevent widespread use of such a fuel for many years, at a minimum. 
         [0004]    Electricity generation from solar and wind sources is a relatively developed technology, and possibly the best option for displacing fossil fuel as an energy source in the near term. Of the different sources of renewable energy, only wind and solar are sufficiently abundant to completely replace fossil fuels. However, neither can be easily converted into a liquid fuel, both are intermittent and are not available “on-demand,” and are thus often supplements to existing centralized power plants. Solar and wind are, however, available in enough abundance that they could replace all other sources of electrical energy generation if the fluctuations could be leveled with energy storage facilities. Furthermore, powering transportation with electricity could drastically reduce carbon emitting fossil energy sources. 
         [0005]    Transportation that is powered from electricity would require electric vehicles or, alternatively, hybrid vehicles that operate using both liquid fuel and stored electricity. Such hybrid vehicles are commonly referred to as “plug-in hybrids” in that the vehicle is “plugged in” to the existing power grid to charge on-board batteries that are used to drive an electric motor in the vehicle. In the event that the charge in the on-board battery of such a plug-in hybrid is depleted, a separate gasoline (or other liquid fuel) engine is engaged to either power the vehicle or provide power to the electric motor of the vehicle. 
         [0006]    Currently there are no mass produced plug-in hybrid automobiles. In the United States, most existing low volume and prototype plug-in electric vehicles use a variation of the standard extension cord, illustrated by  FIG. 1 . These low production US vehicles are generally charged by the universally available 60-Hertz, 120 Volt household power. These connections are limited to a maximum of 15 Amps of current. While conveniently available, this voltage source is not an ideal match to the high frequency, high voltage motor drive components. Sixty-Hertz, 120-Volt household power cannot be used directly in the vehicle and the 60-Hertz components for converting this voltage are heavy and expensive. Further, this arrangement is not inherently bi-directional. If the stored vehicle power is to be available externally, transfer relays are needed as well as a 60-Hertz power inverter. A 60-Hertz, 120-Volt inverter is unneeded elsewhere in the vehicle and is another undesired, expensive subsystem. 
         [0007]    Such connections also require metallic contacts of conductive connectors, which are subject to wear and corrosion. Films from oily vapors or other sources can contaminate the metallic contacts, adding a further disadvantage for such connections. The conductive connector injects the charging voltage into the vehicle without isolation, and additional isolation insulation must be provided within the vehicle, which can be difficult to do because of the amount of wiring. If the isolation breaks down, it poses a safety hazard, for example, standard 60-Hertz household voltages can fatally electrocute humans. 
         [0008]    The relatively low power available from 60-Hertz household receptacles is inadequate to rapidly charge the high capacity battery of a plug-in hybrid vehicle. Even if the 60-Hertz voltage is raised to speed charging, the connectors with metallic contacts must operate at a specified voltage if there is a universal standard. This imposed standard voltage may not be convenient in the future as the technology progresses, and this could force the vehicle designer to compromise the electrical design or make obsolete the existing base of battery chargers. 
         [0009]    Another method for charging batteries is through inductive coupling, which can provide an improvement over metallic contacts. This is not a new concept, and was used, for example, on General Motor&#39;s electric vehicle, the EV-1. The battery charger and inductive connection for the EV-1 was called the Magnecharger, illustrated as  FIG. 2 . The coupling was in the form of a paddle connected to a standalone battery charger by a two-meter long cord. The EV-1 was project was ultimately abandoned with all of the vehicles withdrawn from the market and crushed. 
         [0010]    A fundamental problem with the EV-1 was the requirement for a person to manually remove the paddle from the charger and insert the plug into a slot at the front of the vehicle. The car had to be parked far enough away from the charger to allow room to walk between the vehicle and the charger, wasting space in the garage or parking space. The Magnecharger included no aid to judge the vehicle position. This means that if parked improperly, the cord would not reach the charging slot, or the operator would rub clothing against the car, or, if parked too far away from the charger, would not be able to close the garage door. 
         [0011]    A further disadvantage of the Magnecharger was the need for 230-Volt, 60-Hertz service at 20 Amps. The 230-Volt service is usually not conveniently available and often requires the services of an electrician. The Magnecharger itself was expensive; it was over several thousand dollars because it contained a costly, high power switching inverter. The maximum power available from 230-V, 20-Amp service is 4,600 Watts. At this power level it takes several hours to fully charge a battery powered vehicle capable of a 40 mile or greater range. If the vehicle is parked for the night this is plenty of time for charging. If, however, the vehicle is parked for a lunch stop on a long trip, a faster charge time is desirable. The Lithium-Ion batteries slated for advanced hybrids are capable of very fast charge times, in the order of minutes. The charge time is considerably reduced if the connection is capable of higher power levels. A further disadvantage of the paddle configuration is the narrow tolerance between the sides of the paddle and the mating vehicle magnetic structure. If heating causes parts of the structure to expand, the gap could widen, drastically reducing efficiency and power transfer capability. If the gap narrows from heating, or if debris drops into the slot, the paddle could jam in the charging slot. The gap must be narrow to maintain the full magnetic flux density. 
       SUMMARY 
       [0012]    Various aspects of the disclosure provide charging plugs for a vehicle battery using magnetic induction in lieu of metallic contacts. Embodiments described herein provide inherent advantages of an inductive coupler, such as no exposed contacts that could provide a safety hazard; no exposed metal to corrode, wear, or become contaminated; low or no force to mate, simplifying plugging-in; inherent isolation the vehicle electronics from the charger. 
         [0013]    Embodiments described here are designed to operate with high frequency AC, reducing or eliminating disadvantages of 60-Hertz components. Inductive coupling provided herein has no exposed contacts, reducing the shock hazard associated with charging as compared to a charger that has exposed metal contacts. Another advantage is that the coupling of various embodiments is specified in terms of magnetic flux, not a voltage level. By adjusting the turns-ratio of the plug winding, the supply voltage can be provided at any convenient level. The windings may be selected to develop the specified magnetic flux density at the mating surface. Likewise, the vehicle is not constrained to any particular internal voltage, and any charger can inherently work with any vehicle, despite the internal voltage differences that may be present between vehicles. 
         [0014]    Embodiments provide a plug coupler that is cylindrical with a spherical mating surface, assuring a solid connection even if the plug is slightly misaligned. The cylindrical profile of the plug housing allows the plug to be rotated with respect to the vehicle mating socket. This feature simplifies coupling if the vehicle parking surface is tilted. Also, the mating receptacle entrance may be tapered to prevent jamming. 
         [0015]    The high-frequency power signal provided to the plug does not provide a source that may electrocute or shock a user, unlike 60-Hertz power. Magnetic components scale inversely as a function of frequency making a high-frequency magnetic coupling much smaller than the 60-Hertz equivalent. The high frequency of operation allows a small, inexpensive inductively coupled plug to handle high power levels to rapidly charge a vehicle battery. A standard household extension cord is limited to 1,800 Watts, and the previously discussed Magnecharger, operating from a dedicated 230-Volt connection can supply 4,600 Watts, that is less during operation due to losses in the charging circuitry. In several embodiments described herein, a charger is provided that can operate at high frequency with standard wiring and can supply 12,000 Watts without excessive currents or dangerous voltages. The 12,000-Watt coupling capability allows vehicle batteries to be charged in minutes instead of hours. Furthermore, in some embodiments a solar collector is provided, and by connecting the vehicle directly to the solar collector&#39;s inverter, the high frequency inverter output does not have to be converted to 60-Hertz, thereby reducing the cost and complexity of such a component. 
         [0016]    In one aspect, a vehicle is pulled to a charging station that provides an automatic connection of an inductive charger between the charging station and the vehicle. Some embodiments include a visual indicator that a vehicle operator may use to properly align the vehicle to the charging station. Such a visual indicator may include optical beams to visually position the vehicle for automatic connection of the charger plug. Such automatic, autonomous charger connection will be attractive to many vehicle operators, encouraging electrical vehicle usage by decreasing the manual tasks otherwise required. The light beam used for vehicle alignment, in some embodiments, is digitally encoded with additional information such as the user&#39;s desire to buy or sell battery energy and the height of the charger receptacle of the vehicle. At the vehicle operator&#39;s option, the beam can also pass credit card, or other payment, information to the operators of public parking spaces, relieving the vehicle operator from manually inserting cash or coins into marking meters, pay stations, etc. Other embodiments provide a bi-directional communication link in the charger coupling that allows, for example, a user to call their vehicle on their cell phone to start the air-conditioning as they prepare to leave a location. Conversely, a vehicle alarm system could notify the driver by cell phone if there was an indication of tampering. 
         [0017]    Embodiments described herein provide a number of advantages, such as decades of household electrical energy for most, if not all, of the vehicle&#39;s fuel. Embodiments also provide that many drivers will seldom need to stop at a filling station. In addition, solar collectors and the vehicle battery could be used to provide emergency power should the power grid fail. If, for instance, natural disaster victims have plug-in vehicles with a bi-directional plug, they may be able to use their vehicle to supply emergency power for refrigerators, cell phones, radios, lights, etc. The inductive plug of various embodiments would continue to work even if covered by floodwaters. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is an illustration of a plug of a US standard extension cord. 
           [0019]      FIG. 2  is an illustration of the General Motors Magnecharger for charging the battery of the discontinued EV-1 electric vehicle. 
           [0020]      FIG. 3  is a side view illustration of a plug-in vehicle in an owner&#39;s garage about to receive the inductive coupling of an embodiment. 
           [0021]      FIG. 4  is a side view of a vehicle in a public parking space with an overhead solar collector of another embodiment. 
           [0022]      FIG. 5A  is a view as seen by the driver of the alignment target with a visual alignment aid positioned off to the right indicating the vehicle is not aligned to receive the charger coupling in an embodiment. 
           [0023]      FIG. 5B  is a plan view of the misaligned vehicle corresponding to  FIG. 5A . 
           [0024]      FIG. 6A  is a view of the visual alignment target before the vehicle is close enough for the charger coupling to connect for an embodiment. 
           [0025]      FIG. 6B  is a plan view of an aligned vehicle corresponding to  FIG. 6A . 
           [0026]      FIG. 7A  is a view showing a visual alignment aid with both the alignment beam and the proximity beam centered on the alignment target for an embodiment. 
           [0027]      FIG. 7B  is a plan view of a properly positioned vehicle ready to receive the charger coupling for an embodiment. 
           [0028]      FIG. 8A  is a view of the alignment target with more detail for an embodiment. 
           [0029]      FIG. 8B  is a view of the alignment target of  FIG. 8A  indicating the alignment beam has been detected. 
           [0030]      FIG. 8C  is a view of the alignment target of  FIG. 8A  indicating a properly positioned and connected vehicle. 
           [0031]      FIG. 8D  is a view of a public parking space target rejecting a non-handicapped vehicle for parking in a handicapped space for an embodiment. 
           [0032]      FIG. 9  is a cross-sectional view of the battery charger plug of an embodiment. 
           [0033]      FIG. 10  is a cross-sectional view of the vehicle mounted charger receptacle of an embodiment. 
           [0034]      FIG. 11  is a schematic view of the plug robotic guidance circuitry for an embodiment. 
           [0035]      FIG. 12  illustrates a rectifier combining solar and grid power for an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    The present disclosure recognizes that the current utility company power delivery model is based on centralized power plants with transmission and distribution lines to the power consumers. However, absent a significant, costly, and time-consuming upgrade, the existing transmission and distribution facilities cannot support the added load of an electrically powered transportation system, because of the additional demands that would be placed on the system. An alternate utility model is numerous individual producers that may be coupled with centralized power plants. According to this concept, rooftop photovoltaic (PV) collectors move the energy collection to where the energy is actually used, saving at least some of the expense of upgrading the utility grid. As is well known, wind and solar power is subject to uneven supply, and one economical way to store the energy to offset the uneven supply of wind or solar power is the batteries of plug-in electric, or plug-in hybrid vehicles. 
         [0037]    The embodiments described herein provide charging plugs for a vehicle battery using magnetic induction in lieu of metallic contacts. Such embodiments provide a number of advantages such as listed above relative to inductive couplers, such as that the inductive coupler has no exposed contacts that could provide a safety hazard; there is no exposed metal to corrode, wear, or become contaminated; low or no force required to mate, simplifying plugging-in; and isolation of the vehicle electronics from the charger. 
         [0038]    Various embodiments described herein are designed to operate with high frequency AC, eliminating the disadvantage of 60-Hertz components. Provide the advantage that the coupling is specified in terms of magnetic flux, not a voltage level, which provides that ability to adjust the turns-ratio of the plug winding to provide a supply voltage at any convenient level. The windings are selected to develop the specified magnetic flux density at the mating surface. Likewise, the vehicle of such embodiments is not constrained to any particular internal voltage, so any charger can inherently work with any vehicle, despite the internal voltage differences between vehicles. The high-frequency power signal of the inductive coupler provided in embodiments cannot electrocute or even shock, unlike 60-Hertz power. Magnetic components scale inversely as a function of frequency making a magnetic coupling much smaller than the 60-Hertz equivalent, and thus high frequency of operation allows a relatively small, inexpensive inductively coupled plug to handle high power levels to rapidly charge a vehicle battery. In some embodiments, the charger can operate at high frequency to allow standard wiring to supply 12,000 Watts without excessive currents or dangerous voltages, and can use standard household wiring. Such 12,000-Watt coupling capability allows vehicle batteries to be charged in minutes instead of hours. 
         [0039]    Some embodiments provide for the use of rooftop photovoltaic (PV) solar collectors to supply household electricity, to charge the battery of a plug-in vehicle, and to sell the excess energy to the utility grid for other users. Even with modestly efficient solar cells, there is commonly enough roof area of even a small residence to supply power for all of these uses. If the connection to the hybrid vehicle is bi-directional, the excess capacity of the vehicle battery can supply external power when no power is available from wind or solar radiation sources. 
         [0040]    With reference now to the drawings,  FIG. 1  shows a standard plug commonly used to charge electric vehicles in the United States as prior art.  FIG. 2  is an illustration of the General Motors Magnecharger as prior art.  FIG. 3  is an illustration of one embodiment of the present disclosure sited in a vehicle owner&#39;s garage, for example. Here, a vehicle  20  faces a back wall  23  of the garage. Mounted on the back wall  23  is a laser target assembly  24  containing a Fresnel lens  25  and behind the Fresnel lens  25  is a photodetector and demodulator  26 . Positioned at a convenient place on the vehicle  20  is an access door  31  covering a receptacle for a standard extension cord. An alignment beam  21  and a proximity beam  22  emanate from the front of the vehicle  20 , toward the laser target assembly  24 . Mounted at the extreme front of the vehicle  20  is an outer door assembly  30  and an inner door  29 , aligned near an inductive coupling plug assembly  28 . The plug assembly  28  is shown extended from a below-grade robotic arm compartment  27 . 
         [0041]      FIG. 4  illustrates another embodiment shown here as a public parking facility, although similar configurations may be used in private or residential applications. In this embodiment, the vehicle  20  has an alignment beam  21 , access door  31 , outer door assembly  30  and an inner door  29 , as described previously with respect to  FIG. 3 . In this embodiment the vehicle  20  is parked below a carport roof  34  held over the parking space by a support structure  32 . On the carport roof  34  is a bank of photovoltaic solar cells  33 . Also mounted on the support structure  32  is the laser target assembly  24  and a mirror  35  visible to the vehicle driver, providing a view of a proximity alignment target  36 . In such a manner, a vehicle operator may view the alignment target  36  in the mirror  35 , and pull the vehicle  20  up to the appropriate alignment such that the plug assembly  28  couples with the vehicle  20  recharging port. A crash protection pylon  38  prevents damage to the support structure  32  if the vehicle  20  fails to stop when parking. In this embodiment, the plug assembly  28  is mounted in an above-grade robotic arm compartment  37 . In other embodiments, a portable assembly of target assembly  24 , actuator compartment  37 , and robotic plug assembly may be used for situations where no garage or suitable structure is available. 
         [0042]    As discussed above, in some embodiments the vehicle  20  produces two optical beams that are used as aids to properly position the vehicle  20  in the parking spot and relative to the charger and plug assembly  28 .  FIGS. 5A ,  6 A, and  7 A are views from a driver&#39;s position of such embodiments as the vehicle  20  is maneuvered into position for coupling with the plug assembly  28 . In this embodiment, a Fresnel lens  25  is used as a target, and is visible on the target assembly  24 . The vehicle  20  produces two optical outputs, an alignment bean  21 , and a proximity beam  22 .  FIG. 5A  has an alignment spot  39  from the alignment beam  21 , which in one embodiment is a modulated laser beam, visible to the right of the target  24 . The front of the vehicle  20  is some distance away from the horizontal proximity target  36 .  FIG. 5B , a plan view of the approaching vehicle  20 , shows the alignment spot  39  to be striking the wall  23  and not centered on the target  24  because of the misalignment of the vehicle  20 . In  FIG. 6A , the alignment spot  39  from beam  21  is centered on the lens  25  because the vehicle is properly aligned as directly facing the target  24 . However, the second visible spot, proximity spot  40 , from proximity beam  22  is to the right of the target  24 , indicating that the vehicle  20  needs to be pulled closer to the wall  23 . Plan view  FIG. 6B  again shows the alignment spot  39  centered on the target  24  and the proximity spot  40  to the right of center because the vehicle  20  is not fully in position but is closer to the horizontal proximity target  36 .  FIG. 7A  shows both the alignment spot  39  and the proximity spot  40  converged on the center of the target  24 .  FIG. 7B  is consistent with  FIG. 7A  with both alignment beam  21  and the proximity beam  22  converged on the center of the target  24 . The front of the vehicle  20  partially covers proximity target  36  when the vehicle  20  is fully in position. 
         [0043]      FIG. 8A  is one of four larger illustrations of the alignment target  24  of an embodiment. The Fresnel lens  25  of this embodiment is centered vertically, surrounded by a reflective background  41 . Fiducial marks  44  radiate out from around the lens  25  to assist in centering the alignment beams  39 ,  40 . A beam detection indicator  42  and a connection status indicator  43  are shown as blank in this figure.  FIG. 8B  shows the alignment spot  39  striking the lens  25 . Here, the indicator  42  indicates that the beam  39  has been sensed by the detector  26  by displaying the word “DETECTED.” In  FIG. 8C , both of the beams  39 ,  40  have converged indicating that the vehicle  20  is properly aligned and positioned properly, with indicator  42  showing that the alignment beam  39  was detected and that the coupling was successfully completed as indicated by the displayed message, “CONNECTED,” on the indicator  43 .  FIG. 8D  shows an example of the alignment target used in a public handicapped parking space of an embodiment. This target  24  also has a handicapped symbol  45  indicating that the space is reserved for those registered as handicapped. In this embodiment, information modulated on the alignment beam  39  is received by the alignment target  24 , such information including information relating to the particular vehicle&#39;s eligibility to park in a space that is reserved for handicapped. In the example of  FIG. 8D , the vehicle does not have proper credentials, and the indicator  43  has the message “REJECTED.” Information communicated to/from a vehicle through alignment beam  39 , or other types of communications, will be described in more detail below. 
         [0044]    Referring now to  FIG. 9 , a cross-sectional view of a plug assembly  28  is illustrated for an embodiment. In this embodiment, robotic arm struts  59  elevate the plug assembly  28  into position to mate with the vehicle  20 . The struts  59  remain parallel to each other as they elevate into position because of the arrangement a pair of pivotally attached bushings  60  that are journaled on a bracket  56 . In turn, bracket  56  is pivotally attached vertically to a universal-joint spider member  54  journaled by a set of bushings  57  to the bracket  56 . Likewise, the spider member  54  is pivotally attached to a pair of bushings  55  horizontally journaled to allow vertical rotation of a bracket  53 . The bracket  53 , in this embodiment, is attached to a plug housing  46  via four strain gauges,  52 T,  52 F,  52 R, and  52 B. The uppermost strain gauge  52 T is located at the very top on the periphery of the bracket  53  and of the housing  46 . Likewise, the other strain gauges  52 F,  52 R, and  52 B are located peripherically around the bracket  53  and connected similarly at the front, rear, and bottom of the housing  46 . Within the housing  46  are the magnetic components: a ferrite core  47 , and an associated winding  48  and a bobbin  49  holding the winding  48 . To simplify the drawing, provisions for cooling the magnetic components are not shown as such components will be readily known to one of skill in the art. 
         [0045]    Having described the basic components associated with various embodiments, several exemplary embodiments of the operation of a charging station of the present disclosure are now described. With reference again to  FIG. 3 , the hybrid-electric or electric vehicle  20  is illustrated as parked in a garage or other parking space. In this view, the vehicle  20  is parked and is midway through the charger connection process. An exemplary hook-up sequence is as follows for a vehicle being parked in a private residence garage. First, while approaching the garage, the driver activates a standard garage door opener. The garage door opens in response to the garage door opener command, and in an embodiment the alignment beam  21  and proximity beam  22  are activated from optical sources located on the vehicle, and opens a cover that is associated with a charging receptacle located in the vehicle. In another embodiment, as the door opens, the driver presses another button to activate both the alignment beam  21  and the proximity beam  22 . The alignment spot  39  from the alignment beam  21  shines on the garage back wall  23 , illustrated in  FIG. 5A . The alignment spot  39  provides a visual target for the driver to align the vehicle  20  with the charger plug  28 . The driver simply steers to center of the alignment spot  39  on the bulls-eye appearing Frensel lens  25 , which is part of the target assembly  24 , and once aligned, the driver sees the alignment spot  39  centered on the Frensel lens  25  as illustrated in  FIG. 6A . The alignment beam  20 , in some embodiments, also transmits relevant digital information to a charger controller  92  (illustrated in  FIG. 11 ) associated with plug assembly  28 . The alignment spot  39 , in this embodiment, does not have to be centered on the lens  25  and as long as the spot  39  is anywhere on the lens  25 , information can be transmitted successfully. Similarly, the beam  21  does not have to be exactly perpendicular to the target  24  for satisfactory operation. The alignment beam  21  is focused by the Frensel lens  25  on to the photodetector  26 . The acceptance angle of the lens  25  and detector assembly  26  matches the angular misalignment acceptable to the plug assembly  28  so that if the detector senses the digital information transmitted by the alignment beam  21 , then the plug  28  is mechanically aligned well enough to mate with the vehicle  20 . At this point the proximity beam  22  also casts a spot on the back wall  23 . As the vehicle approaches the ideal distance into the garage, the proximity spot  40  moves closer to the Frensel lens  25  as indicated in  FIG. 6A  and  FIG. 6B . When the vehicle  20  is close enough to connect to the charger plug,  28 , the proximity spot  40  is also shining on the Frensel lens  25 .  FIG. 7A  illustrates the superimposed alignment spot  39  and proximity spot  40  on Frensel lens  25 .  FIG. 7B  shows the vehicle  20  ideally aligned for the charger plug  28  connection. Fiducial marks  44  help guide the driver to the proper vehicle location as seen in  FIG. 8A . The alignment beam  21  in this embodiment is affixed horizontally to be aligned with the vehicle  20  centerline. The alignment beam  21  can be manually adjusted vertically by the driver to compensate for variations in the vehicle  20  height due to load variations, tire inflation, etc. It will be readily understood by one skilled in the art that various different alignment beams and alignment methods may be used to assist with the proper alignment of a vehicle as pulled into a parking space. 
         [0046]    As briefly mentioned above, some embodiments, illustrated in  FIG. 4 , for example, provide a different type of indicator, such as a mirror, that can be used by a driver to determine the vehicle&#39;s position. In cases where the vehicle&#39;s  20  position is determined by an overhead mirror  35 , the driver will observe the mirror and the proximity alignment target  36  located on the parking surface will be partially obscured by the front of the vehicle  20  when the vehicle  20  is moved into position for charging. This situation is illustrated in  FIG. 4 , where the vehicle is parked in a commercial parking space, for example. If the parking space is shaded as is illustrated in the example of  FIG. 4 , the overhead roof  34  may have a bank of photovoltaic solar cells  33  that can directly collect solar energy for use in charging vehicles. This arrangement saves the additional cost of transmission and distribution grid upgrades and also minimizes power losses. Such an arrangement, in appropriate situations, allows a driver to power his or her vehicle, at least partially, with energy from the sun. In  FIG. 4 , the charger plug assembly  28  is mounted vertically in an above-grade robotic arm compartment  37 . The arm compartment  37  is protected from accidental parking damage by the robust pylon  38 . 
         [0047]    With reference now to the exemplary embodiment of  FIGS. 8A ,  8 B,  8 C, and  8 D, the target  24  has a beam detection indicator  42  and a connection status indicator  43 . The function of beam detection indicator  42  is to indicate to the driver that the vehicle  20  is aligned well enough to be sensed by the detector  26 . The connection status indicator  43  indicates that the connection has been made only after the vehicle  20  is parked and the plug assembly  28  has fully mated with the vehicle  20 , as illustrated in  FIG. 8C . 
         [0048]    As also mentioned above, the symbol  25  could be dynamically configured to adapt to varying handicapped space, or other authorized parking space, needs. Should a driver improperly park in a space, the indicator  43  would display a “REJECTED” message even if the vehicle  20  were properly aligned because the status or credentials of the vehicle  20  is encoded on the alignment beam  21 . Such a situation is illustrated in  FIG. 8D . Since credit information, in the form of a credit card number or other means, could, at the driver&#39;s choice, be transmitted to the detector  26 , the space could be conveniently credited to a commercial parking lot without requiring a parking attendant or payment kiosks. If there was not sufficient credit in the driver&#39;s account, the indicator  43  could also display a “REJECTED” message. 
         [0049]    In one embodiment, until the driver has properly positioned the vehicle  20  and it is placed in park or otherwise properly positioned in the spot, all communication is one-directional from the vehicle to the detector  26 . The driver placing the vehicle  20  in park causes an indication of that status to be encoded onto the alignment beam  21 . Other information can be encoded as well, including the height of the vehicle receptacle  83 , illustrated in  FIG. 10 . After sensing that the vehicle  20  is parked, the charger controller  92  activates the charger plug assembly to rise from its stowed position, such as a below-grade robotic arm compartment  27  or from an above-grade robotic arm compartment  37 , for example.  FIG. 3  and  FIG. 4  show the plug assembly rising from the stowed position. The design of such robotic arms is well known in the art. If the vehicle needs to be charged in a location without this automated robotic plug assembly  28 , a standard extension cord  FIG. 1 , could plug into the vehicle  20  under the charger plug door  31 . 
         [0050]    After the charger plug assembly  28  rises to the height of the vehicle receptacle  83 , the plug assembly  28  translates horizontally in the direction of the vehicle  20  until contact is made with the vehicle receptacle. 
         [0051]      FIG. 9  is a cross-sectional view of the plug assembly  28 . Robotic arm struts  59  elevate the plug assembly  28  into position to mate with the vehicle  20 . The struts  59  remain parallel to each other as they elevate into position because of the arrangement a pair of pivotally attached bushings  60  that are journaled on the bracket  56 . This arrangement keeps the plug assembly  28  oriented parallel to the floor. In turn, bracket  56  is pivotally attached vertically to the universal joint spider member  54  journaled by the bushings  57  to the bracket  56 . Likewise, the spider member  54  is pivotally attached to the bushings  55  and horizontally journaled to allow vertical rotation of the bracket  53 . This universal-joint arrangement allows the plug assembly  28  to adjust angularly if the vehicle  20  is slightly misaligned when parked. 
         [0052]    The bracket  53  is attached to a plug housing  46  via four strain gauges,  52 T,  52 F,  52 R, and  52 B. These strain gauges sense pressure if the plug assembly  28  is slightly off-center with respect to plug receptacle  83  and contacts the sides of the bell shape opening of the plug receptacle  83  of  FIG. 10 . If this happens, the robotic controller  93  drives the arms  59  into align. Prior to any contact, spring  58  keeps the plug assembly  28  straight. 
         [0053]    Within the housing  46  are the magnetic components: the ferrite core  47 , with associated winding  48  and bobbin  49 . These magnetic components follow conventional design practices for ferrite core transformers. These three components, the ferrite core  47 , associated winding  48 , and bobbin  49  form the primary side of power transformer. When plug assembly  28  is mated with the plug receptacle  83 , the two components comprise a ferrite core transformer. A silicon carbide wear plate  51  and silicon carbide wear ring  50  protect the ferrite core  47  from damage. The convex surface formed by ferrite core  47 , plate  51 , and ring  50  matches the concave mating surface of the receptacle  83 . 
         [0054]    With continuing reference to  FIG. 9 , a cavity within the housing  46  forms the electronics compartment  65 . This compartment  65  contains strain gauge amplifiers and various connectors for power and signal leads (not shown). Also, in this embodiment, within this compartment  65  are LED  63 , photo diode  64  and beam splitter  62  which allow bi-directional communication through lightpipe  61  so that digital information can be exchanged between the charger plug  28  and corresponding components within the receptacle  83 . 
         [0055]      FIG. 10  details the structure of receptacle  83  for an exemplary embodiment. The magnetic components, ferrite core  67 , bobbin  49 , winding  68 , wear ring  71 , and wear plate  72  function as the corresponding components in charger plug  28 . The convex outer surface of those components allows a very slight misalignment between the charger plug  28  and the receptacle  83 . The tapered entrance of the housing  83  guides the charger plug  28  into a constricted opening as the two components mate. The diameter of the opening, even near the constricted end, is slightly larger than the plug  28  diameter, so the plug is unlikely to bind in the receptacle if diameters vary with temperature or other causes. This loose fit does not assure absolute angular alignment of the plug  28 , and the curved faces accommodate slight misalignment. 
         [0056]    The spring-loaded flexible joint of the charger plug  28  accommodates larger angular misalignments between the charger plug  28  and the vehicle  20 . The receptacle housing  66  has a cavity for the receptacle electronics compartment  69 . The electronics compartment  69  contains strain gauge amplifiers and various connectors for power and signal leads (not shown) as well as LED  63 , photo diode  64 , and beam splitter  62  which allow bi-directional communication through lightpipe  70  in the same manner as the corresponding components in the charger plug assembly  28 . Information transmitted over this optical link may include the state of the vehicle  20  battery charge, whether the operator wants to sell energy within the battery, or conversely, to charge the battery. 
         [0057]    The magnetic components in the charger plug  28  and the receptacle  83  are sized to handle substantially identical amounts of power. However, the number of turns in the charger plug winding  48  and the number of turns in the receptacle winding  68  do not have to match. This means the operating voltage of the charger plug assembly  28  and the vehicle voltage can be independently optimized and still be consistent with a single universal standard. 
         [0058]    In the exemplary embodiment of  FIG. 10 , the end of receptacle housing  66  opposite the magnetic components is covered by two rectangular doors  29 ,  73  when the vehicle is not being charged. The doors  29 ,  73  are approximately the same dimensions as an US license plate. Outer door  73  is pivotally attached to activating shaft  76 , journaled in bushing  77 . Similarly, inner door  29  is pivotally attached to shaft  79 , journaled in bushing  79 . Both door shafts  76 ,  78  are operated by motor activators (not shown) similar to the well known automotive activators used to open headlight doors, etc. The door opening sequence begins when the vehicle operator activates the alignment beam  21 . This would typically occur well before the vehicle  20  is parked. The outer door  73  opens as indicated by position  74 . This position  74 , allows the door  73  to act both as a guide for the plug  28  and a mount for the vehicle license plate  80 . After the outer door  73  is opened, inner door  29  opens to the position  75  shown in  FIG. 10 . With both doors  29 ,  73  open, there is a capture area of approximately 12″ horizontally by 14″ vertically. The horn shaped opening of the housing  66  transitions from the rectangular shape of the license plate  80  to the round cross-section of the ferrite core  67  to guide the ferrite core  47  of the plug  28  to align with the ferrite core  67  of the receptacle  83 . 
         [0059]    Once the alignment beam  21  transmits the code to the detector  26  that the vehicle is parked, the robotic arm controller  92  causes the robotic arms  59  to raise the plug assembly  28  to the height of the receptacle  83 . Once the plug is at the desired height, a servo mechanism within the robotic arm controller  92  drives the plug  28  toward the vehicle receptacle  83  until the plug  28  contacts the receptacle  83 . The strain gauge sensors  52  detect contact with the receptacle  83  walls and drive the servo mechanism to correct the plug path until the plug  28  is fully mated in the receptacle  83 . The fully mated position is detected by pressure being sensed by all of the strain gauge sensors  52  which, in this embodiment, activates the optical communications channel between the plug  28  and receptacle  83 . After the plug  28  is fully mated, the optical interface is activated to establish transferring charge/discharge, and/or other information, between the charger and vehicle. 
         [0060]      FIG. 11  illustrates controller  92  and associated circuitry for an exemplary embodiment. The elevate signal line  89  from the controller  92  feeds into the elevation amplifier  85 . At this stage of the connection process, the elevation switch  94  from the elevation amplifier  85  is commanded closed by the controller  92 . Thus the elevation signal from elevation switch  94  is connected to the elevation amplifier drive signal  97  and the robotic arm  59  rises to the height of the receptacle  83 . Once at the correct height, signal  89  from the controller  92  becomes inactive to halt the arm  59  elevation. During the interval while the arm  59  is rising, yaw switch  93  is also commanded closed by the controller  92 , but no drive signal is on the yaw drive line  96  because there is no output from yaw amplifier  84 . Likewise, the translation switch  95  is closed and, similarly, no signal is applied to translation drive line  98  because there is no output from the translation amplifier  88 . Once the plug  28  has been elevated to the mating height, the controller  92  applies a translation signal to the translation amplifier  88  through controller output  91 . This signal from the translation amplifier  88  through closed switch  95  to the translation drive line  98 , causes the plug assembly  28  to move toward receptacle  83 . If the plug  28  makes contact with the sidewalls of the housing  66  before fully mated, strain gauges  52 F and  52 R provide differential signals into the yaw amplifier  84  to drive the servo arm  59  to center the plug  28  horizontally. Likewise, if the plug  28  makes contact with the open upper door  74 , open lower door  75 , or the top or bottom of the housing  66 , strain gauges  52 T and  52 B provide differential signals to elevation amplifier  85  to center the plug  28  vertically. Once the plug is fully seated, the building pressure is sensed by the four strain gauges  52 T,  52 R,  52 R, and  52 B equally. Those outputs are summed with the plug seated amplifier  86 . When the output of the amplifier  86  reaches the predetermined threshold corresponding to the desired seating pressure, that level causes the threshold detector  87  to signal that the plug is seated via the plug seated signal line  90 . Once the controller  92  senses the active signal on the line  90 , the controller  92  commands switches  93 ,  94 , and  95  to open, thus stopping all drive to the robotic arms  59 . 
         [0061]    With reference now to  FIG. 12 , an exemplary embodiment is described in which a power arrangement avoids having to convert DC voltage from a solar panel  33  to 60-Hertz AC, and thus avoid a major expense associated with an inverter. In this example, 60-Hertz AC from the grid is rectified by diodes D 2 , D 3 , D 4 , and D 5  to directly power the high frequency inverter  99  when the solar panel  33  is inactive. When sunlight strikes the solar panel  33 , that current is applied to the high frequency inverter  99  through diode D 1 , overriding the grid connection. 
         [0062]    While the above descriptions contain many specificities, these should not be construed as limitations on the scope of the invention. Other variations are possible. For instance, other methods of aligning the vehicle  20  could be used as long as the vehicle  20  was positioned accurately to receive the plug assembly  28 . Methods other than modulating a light beam could be used to exchange information between the vehicle  20  and the charging facility. For example, information could be transmitted via RF, inductive coupling, ultrasonic waves, modulation of the charging waveform, and infrared light. The information transmitted is not limited to the descriptions of the described embodiments. Other types of covering for the vehicle receptacle are possible including using a single door or no door at all, are within the scope of the invention. Other locations for the vehicle receptacle, for instance under the vehicle, will work if the coupling can be completed. Likewise, other methods of guiding the plug assembly  28  can be used within the scope of the present invention. Some embodiments described herein use a robotic drive to translate the plug assembly  28  to mate with the vehicle. However, the forward motion of the vehicle could be used to couple the stationary plug assembly  28  into the vehicle receptacle. 
         [0063]    The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention and the currently known best mode. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.