Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR THE ALIGNMENT OF
VEHICLES PRIOR TO WIRELESS CHARGING
CROSS-REFERENCE TO RELATED APPLICATIONS
100011 This application claims the benefit of priority to U.S. Patent
Application Serial No. 16/723,750, filed December 20, 2019, the disclosures
of which are incorporated herein by reference in their entireties.
TECHNICAL FIELD
100021 This patent application describes a vehicle alignment system as
it pertains to wireless charging through use of magnetic resonant induction.
BACKGROUND
100031 Resonant induction wireless charging makes use of an air core
transformer consisting of two concentric coils displaced along a common
coil axis. Transformer coupling coefficient and wireless power transfer
efficiency is degraded if the primary and secondary coils are not axially
aligned. For vehicle wireless charging this means some provision must be
made so that the vehicle parking position is precise and repeatable in order
to
ensure coil axial alignment.
SUMMARY
100041 Various details for the embodiments of the inventive subject
matter are provided in the accompanying drawings and in the detailed
description text below.
100051 A vehicle alignment system aligns a vehicle with a wireless
power induction coil for wireless charging through use of magnetic resonant
induction. The system includes a transmission line leaking a signal having an
operating frequency and that is disposed in a parking slot containing the
wireless power induction coil. The transmission line guides the vehicle to
the wireless power induction coil for charging. At least two vehicle mounted
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antennas mounted on respective sides of, and typically symmetrically with
respect to, the transmission line when the vehicle is aligned in the parking
slot detect the signal that leaks from the transmission line. Signal
processing
circuitry detects a relative signal phase between the signals received by the
antennas on opposite sides of the transmission line. The relative phase
differences between the detected signals from the antennas are representative
of alignment of the vehicle left-right with respect to the transmission line.
[0006] In sample embodiments, a vehicle alignment system aligns a first
wireless power induction coil of a vehicle with a second wireless power
induction coil in a parking slot for wireless charging through use of magnetic
resonant induction. The system includes a ground assembly disposed in the
parking slot. The ground assembly may include a wireless charger comprising
one or more wireless charging coils and magnetic inductive resonance
communications transceivers and a beacon signal source that transmits a beacon
signal. The system further includes a transmission line connected to the
ground
assembly and disposed in the parking slot so as to leak a signal having an
operating frequency that is detected by the vehicle to guide the vehicle to
the
second wireless power induction coil for charging. In the sample embodiments,
the transmission line comprises a continuous wireline monopole antenna
disposed in a folded pattern relative to the ground assembly or a converging
wireline dipole antenna having first and second sections that extend away from
the ground assembly. In operation, the vehicle detects the signal having the
operating frequency that leaks from the transmission line using at least two
vehicle mounted antennas mounted on opposite sides of the transmission line
when the vehicle is aligned in the parking slot and processes respective
signals
detected by the at least two vehicle mounted antennas to determine a relative
signal phase between the respective signals that is representative of
alignment of
the vehicle left-right with respect to the transmission line. The transmission
line
may be disposed along a centerline of the parking slot or parallel to but
offset
from a center line of the parking slot. The transmission line also may be
curved
along a trajectory to guide the vehicle to the ground assembly in the parking
slot.
In sample embodiments, the operating frequency is 40.68 MHz or 13.56 MHz.
[0007] In further sample embodiments, a first end of the continuous
wireline monopole antenna is connected to the ground assembly and offset on a
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first side of a centerline of the ground assembly. A second end of the
continuous
wireline monopole antenna is adjacent to the ground assembly on a second side
of the centerline of the ground assembly. The continuous wireline monopole
antenna also includes first and second sections that extend substantially in
parallel on the first and second sides of the centerline of the ground
assembly.
[0008] In other sample embodiments, the first and second sections of
the converging wireline dipole antenna that extend away from the ground
assembly are parallel to each other and offset on respective sides of a
centerline
of the ground assembly and first ends of the first and second sections are
connected to the ground assembly.
[0009] In still other sample embodiments, a leaky transmission line is
connected to the ground assembly and extends away from the ground assembly
beyond an end of the transmission line that is remote from the ground
assembly.
In such embodiments, the beacon signal source of the ground assembly pulses a
beacon signal on the leaky transmission line and provides a continuous beacon
signal on the transmission line comprising the continuous wireline monopole
antenna or the converging wireline dipole antenna.
[0010] In still further sample embodiments, a transmitter is provided at
an end of the leaky transmission line that is remote from the ground assembly.
The transmitter receives data from the ground assembly via the leaky
transmission line and broadcasts at least a portion of the data received from
the
ground assembly. The data broadcast by the transmitter at the end of the leaky
transmission line may include power levels offered by the ground assembly,
power
types (AC/DC) available at the ground assembly, connector types supported by
the
ground assembly, payment forms accepted by the ground assembly, whether a
wireless
charger of the ground assembly is in use, and/or time left in a charging
session being
performed by the ground assembly.
[0011] In accordance with other aspects, a method is provided for
aligning a first wireless power induction coil of a vehicle with a second
wireless
power induction coil in a parking slot for wireless charging through use of
magnetic resonant induction. The method includes a ground assembly disposed
in the parking slot providing a beacon signal to a transmission line disposed
in
the parking slot so as to guide the vehicle to the second wireless power
induction
coil for charging; the transmission line leaking the beacon signal at an
operating
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frequency, the transmission line comprising one of a continuous wireline
monopole antenna disposed in a folded pattern relative to the ground assembly
and a converging wireline dipole antenna having first and second sections that
extend away from the ground assembly; aligning the vehicle left-right in the
parking slot relative to the transmission line for charging by the second
wireless
power induction coil, the aligning comprising at least two vehicle mounted
antennas mounted on opposite sides of the transmission line when the vehicle
is
aligned in the parking slot detecting the beacon signal at the operating
frequency
that leaks from the transmission line; and adjusting alignment of the vehicle
relative to the second wireless power induction coil based on a relative
signal
phase between the respective signals that is representative of alignment of
the
vehicle left-right with respect to the transmission line.
[0012] In sample embodiments, the method further includes connecting
a first end of the continuous wireline monopole antenna to the ground assembly
and offsetting the first end on a first side of a centerline of the ground
assembly,
extending first and second sections of the continuous wireline monopole
antenna
substantially in parallel on the first side and on a second side of the
centerline of
the ground assembly, and placing a second end of the continuous wireline
monopole antenna adjacent to the ground assembly on the second side of the
centerline of the ground assembly.
[0013] In other sample embodiments, the method further includes
placing the first and second sections converging wireline dipole antenna
parallel
to each other so as to be offset on respective sides of a centerline of the
ground
assembly and connecting first ends of the first and second sections to the
ground
assembly.
[0014] In still other sample embodiments, the method includes
connecting a leaky transmission line to the ground assembly such that the
leaky
transmission line extends away from the ground assembly beyond an end of the
transmission line that is remote from the ground assembly. In such
embodiments, the ground assembly pulses a beacon signal on the leaky
transmission line and provides a continuous beacon signal on the transmission
line comprising the continuous wireline monopole antenna or the converging
wireline dipole.
[0015] In yet other sample embodiments, the method includes providing
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a transmitter at an end of the leaky transmission line that is remote from the
ground assembly, the transmitter receiving data from the ground assembly via
the leaky transmission line, and the transmitter broadcasting at least a
portion of
the data received from the ground assembly. In sample embodiments, the
transmitter broadcasts data including power levels offered by the ground
assembly, power types (AC/DC) available at the ground assembly, connector
types supported by the ground assembly, payment forms accepted by the ground
assembly, whether a wireless charger of the ground assembly is in use, and/or
time left in a charging session being performed by the ground assembly.
100161 As discussed herein, the logic, commands, or instructions that
implement aspects of the methods described herein may be provided in a
computing system including a processor, a memory, and a wired
communications subsystem. Another embodiment discussed herein includes the
incorporation of the techniques discussed herein into other forms, including
into
other forms of programmed logic, hardware configurations, or specialized
components or modules, including an apparatus with respective means to
perform the functions of such techniques. The respective algorithms used to
implement the functions of such techniques may include a sequence of some or
all of the electronic operations described herein, or other aspects depicted
in the
accompanying drawings and detailed description below. Such systems and
computer-readable media including instructions for implementing the methods
described herein also constitute sample embodiments.
[0017] This summary section is provided to introduce aspects of the
inventive subject matter in a simplified form, with further explanation of the
inventive subject matter following in the text of the detailed description.
This
summary section is not intended to identify essential or required features of
the
claimed subject matter, and the particular combination and order of elements
listed this summary section is not intended to provide limitation to the
elements
of the claimed subject matter. Rather, it will be understood that the
following
section provides summarized examples of some of the embodiments described in
the Detailed Description below.
BRIEF DESCRIPTION OF THE DRAWINGS
100181 The foregoing and other beneficial features and advantages of
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the systems and methods described herein will become apparent from the
following detailed description in connection with the attached figures, of
which:
100191 Figure la shows a representation of a vehicle parking slot with
an induction wireless power sending coil and an alignment system including
a transmission line coincident with the parking slot center line.
100201 Figure lb shows a representation of a vehicle parking lot with
angled parking slots, induction wireless power sending coils, and an
alignment system that includes curved transmission lines that assist in
guiding a vehicle to the proper location within the parking slot for charging.
100211 Figure lc shows a representation of a bus approaching an
inductive charging location after a turn whereby a long curved transmission
line
of the alignment system ensures proper trajectory to get into alignment at the
charging coil.
100221 Figure 2a shows a conceptual representation of the apparatus
for vehicle parking alignment in accordance with a sample embodiment.
100231 Figure 2b shows a representative relationship between vehicle
antenna phase difference and vehicle alignment.
100241 Figure 3a shows an embodiment of the parking slot radio
frequency source and transmission line implemented as a 300 Ohm balanced
transmission line.
100251 Figure 3b shows an alternate embodiment of the parking slot
radio frequency source and transmission line implemented as a terminated 50
or 75 Ohm coaxial cable with specially designed slots in the outer conductor
or shield.
100261 Figure 4 shows an embodiment of the antenna commutation
switch and associated circuitry.
100271 Figure 5 shows an embodiment of the post FM receiver signal
processing circuitry.
100281 Figure 6 shows an alternative embodiment of an alignment
system for the approach to a magnetic induction resonant wireless charger in a
typical pull-in parking stall.
100291 Figure 7 shows another alternative embodiment of an alignment
system for the approach to a magnetic induction resonant wireless charger in a
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typical pull-in parking stall.
100301 Figure 8a shows a folded wireline dipole antenna having at one
end thereof a ground assembly hosting a beacon signal source.
100311 Figure 8b shows a graphical representation of the signal error
function of the folded wireline dipole antenna illustrated in Figure 8a.
100321 Figure 9a shows a converging wireline dipole antenna having at
one end thereof a ground assembly hosting a beacon signal source.
100331 Figure 9b shows a graphical representation of the signal error
function of the converging wireline dipole antenna illustrated in Figure 9a.
100341 Figure 10a shows a vehicle alignment system for wireless power
transfer positioning using both a leaky transmission line to provide initial
guidance and a 1/2 wave 'converging antenna' for alignment and ranging from
the
antenna end to a wireless charging pad of a ground assembly.
100351 Figure 10b shows a graphical representation of the signal error
function of the vehicle alignment system illustrated in Figure 10a.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
100361 The inventive systems and methods may be understood more
readily by reference to the following detailed description taken in connection
with the accompanying figures and examples, which form a part of this
disclosure. It is to be understood that systems and methods are not limited to
the specific products, methods, conditions or parameters described and/or
shown herein, and that the terminology used herein is for the purpose of
describing particular embodiments by way of example only and is not intended
to be limiting. Similarly, any description as to a possible mechanism or mode
of
action or reason for improvement is meant to be illustrative only, and the
systems and methods described herein are not to be constrained by the
correctness or incorrectness of any such suggested mechanism or mode of action
or reason for improvement. Throughout this text, it is recognized that the
descriptions refer both to methods and software for implementing such methods.
[0037] A detailed description of illustrative embodiments will now be
described with reference to Figures 1-10. Although this description provides a
detailed example of possible implementations of the systems and methods
described herein, it should be noted that these details are intended to be by
way
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of example only and in no way delimit the scope of the claimed subject matter.
[0038] The functions described herein may be implemented, at least
partially, in software in one or more embodiments. The software may consist of
computer executable instructions stored on computer readable media or
computer readable storage device such as one or more non-transitory memories
or other type of hardware-based storage devices, either local or networked.
Further, such functions correspond to modules, which may be software,
hardware, firmware, or any combination thereof Multiple functions may be
performed in one or more modules as desired, and the embodiments described
are merely examples. The software may be executed on a digital signal
processor, ASIC, microprocessor, or other type of processor operating on a
computer system, such as a personal computer, server, or other computer
system,
turning such computer system into a specifically programmed machine.
[0039] Figure la is a schematic representation of an automotive parking
slot 10. The wireless power transfer primary coil 12 is shown near the head of
the parking slot 10, although the wireless power transfer primary coil 12
could
also be located at the foot of the parking slot 10 or elsewhere within the
parking
slot boundaries. No matter what the primary coil location, the vehicle must be
parked within the indicated boundaries of the parking slot 10. A buried or
surface mounted transmission line 14 extends along the parking slot
centerline.
This transmission line 14, connected to a low power continuous wave radio
frequency source 20 (Figure 2), creates a localized radio frequency field used
by
the vehicle mounted electronics to determine vehicle alignment within the
perimeter of the parking slot 10. The transmission line 14 can vary in length
and
orientation from the short and straight embodiment shown in Figure la or
longer
and curved as shown in Figures lb and lc.
[0040] Figure lb is a representation of a series of angled parking slots 10.
The wireless power transfer primary coil 12 is shown in each of the angled
parking slots 10 near the head-end. A buried or surface mount transmission
line
14 runs within the parking slot along the centerline and extends out of the
parking slot, curving into the lane of vehicle travel along a trajectory to
guide the
vehicle to the wireless power induction coil 12 in the parking slot 10. A
vehicle
15 travels in a direction from right to left and receives the alignment signal
from
the transmission line and a low power continuous wave radio frequency source
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20 (Figure 2) for the appropriate slot where a charging primary coil 12 is
available. The vehicle 15 uses the alignment signal from the transmission line
14 in conjunction with receive antennas on the vehicle 15 as described below
with respect to Figure 2.
[0041] Figure lc is a representation of a bus 16 approaching a wireless
inductive charging station including wireless power induction coil 12 after
completing a turn. It is important that the bus 16 be properly aligned at the
wireless power induction coil 12, and proper turning radius and location is
critical in achieving the correct trajectory. In this example, transmission
line 14
has a length many tens of feet long and embedded in the roadway 17 with the
proper orientation to consistently guide the bus 16 along the correct path for
proper alignment at the charging coil 12.
[0042] Figure 2a is a block diagram representation of the alignment
electronics. On the ground, there is a radio frequency source 20 and a length
of transmission line 14. On the vehicle, there are two small antennas 22, 24
mounted equal distant to the left and the right of the vehicle centerline.
Those
skilled in the art will appreciate that the antenna 22, 24 could also be
offset
(not equidistant) provided the offset is accounted for in the detected phase
offset. The antennas 22, 24 are connected by coaxial cable 26 to an antenna
switch 28. The antenna switch 28 is controlled by the antenna commutation
clock 30 to alternately connect one then the other antenna 22, 24 to a
conventional frequency modulation radio receiver 32. In a sample
embodiment, the commutation signal is a 50% duty cycle square wave.
[0043] When the two receiving antennas 22, 24 are placed equal distant
from the transmission line 14 as is the case when the vehicle is symmetrically
aligned within the parking slot 10 perimeter, the commutating action of the
antenna switch 28 has no effect upon the receiver signal. The amplitude and
the phase of the two antenna input signals 31 are identical and there is no
response from the receiver 32. However, if the vehicle is mis-aligned within
the parking slot 10, the vehicle antennas 22, 24 are no longer symmetrical
with respect to the transmission line 14. The antenna switching action then
introduces signal amplitude and phase perturbations at the commutation rate.
The signal from the antenna closer to the transmission line 14 will have
larger amplitude and leading phase with respect to the more distant antenna.
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The frequency modulation receiver 32 ignores the amplitude perturbations
but detects the phase perturbations, frequency being the time rate of change
of phase, thereby replicating the antenna switch commutation signal in the
receiver audio output 34. The receiver audio commutation signal replica is
altered
by the limited receiver bandwidth. If the commutating signal frequency is
above the
receiver recovered audio pass band, there is no recovered commutation signal.
If the
commutating signal frequency is just above the lower receiver audio pass band
frequency, the recovered commutation signal will approximate the original
commutation square wave albeit low pass filtered by the receiver upper audio
pass
band limit. A commutation signal frequency in the upper half of the receiver
audio
pass band leads to a largely sinusoidal recovered audio signal.
100441 As further illustrated in Figure 2a, the audio output 34 is
provided to synchronous detector 36 to detect the phase differences between
the respective antenna signals, and output signals representative of any mis-
alignments are provided to a voltage comparator 38 to determine alignment
error polarity based on which signal has a leading phase or lagging phase and
to an absolute value detector 40 that determines the alignment error
magnitude. In sample embodiments, the alignment error polarity and
alignment error magnitude signals are provided to a display device and other
audiovisual means to provide feedback to the driver for adjusting the vehicle
in the parking slot 10 with respect to the wireless power induction coil 12.
100451 Figure 2b depicts an example representation of phase differences
between the respective alignment antennas as a function of the alignment error
or displacement from centerline.
100461 The system maximum operating frequency provided by radio
frequency source 20 is set by the separation between the two vehicle
mounted antennas 22, 24 which must be less than the width of the vehicle.
In the United States, the average parking slot width is about nine feet.
Automobiles are typically no more than 8 feet wide. In order to avoid phase
ambiguity, the two sensing antennas 22, 24 must be spaced no more than k/2
apart at the operating frequency. For two sensing antennas separated by eight
feet, the maximum system operating frequency is about 61.5 MHz. Higher
frequencies and narrower antenna spacing is possible if the vehicle driver
can be assumed to enter the parking slot with an initial alignment error less
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than 1/2 of the parking slot width. Higher operating frequencies are also
possible with the use of more than two vehicle mounted antennas with the
additional antenna or antennas used to resolve phase ambiguity. Those
skilled in the art will appreciate that there is no lower limit on the system
operating frequency except the signal to noise ratio of alignment error
becomes progressively worse as the operating frequency is lowered.
100471 The apparatus described herein provides for vehicle alignment
left-right with respect to the parking slot centerline. Vehicle left-right mis-
alignment is indicated to the driver by visible, audible or tactile means. A
visual indication may be an illuminated indicator, a graphical display or
software generated graphical overlay imposed upon a video camera image.
An audible indication may be a continuous or pulsating sound or a software
generated speech synthesizer. Tactile indication may be provided by the
vehicle steering wheel or steering mechanism, gear shift lever, the driver's
seat or through the vehicle floor or through floor mounted vehicle control
pedals. Driver visual cues or technical means described, for example, in U.S.
Provisional Patent Application No. 61/862,572, filed August 6, 2013, may
be used to indicate and control where the aligned vehicle should stop for
axial coil alignment in the front-back directions for assurance that the
driver
pulls far enough into the parking slot 10 to align the magnetic coils for
charging.
100481 Figures 3a and 3b illustrate sample embodiments of the
transmission line 14. In particular, Figure 3a shows the radio frequency
source 20 and a buried or surface mounted transmission line 14 that leaks a
signal at the operating frequency. In this embodiment, a 40.68 MHz, fifty-
ohm impedance continuous wave radio frequency source 20 provides radio
frequency excitation. A power level of about 1 mW is used. A mini-circuits
RF transformer 42, model number ADT 4-6T is used as an impedance
matching balun. The transmission line 14 is implemented with a length of
ordinary 300-ohm characteristic impedance balance transmission line. While
this transmission line is not designed to be leaky, there is sufficient
leakage
to be picked up by antennas 22, 24 in sample embodiments. A 300-ohm
resistor 44 terminates the end of the balance line in order to eliminate
reflections and standing waves. The transmission line does not have to be
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balanced; a leaky un-balanced coaxial line would be equally suitable.
Alternatively, other transmission line impedances such as 50 or 75-ohm
coaxial cable with slots in the outer shielding could equally be used. Figure
3b depicts an unbalanced 50 or 75 Ohm coaxial cable transmission line 14'
with specially designed slots 43 and termination resistor 45 that is matched
to the coaxial cable's characteristic impedance.
100491 Figure 4 shows the circuitry associated with the antennas 22,
24, antenna commutating switch 28, and commutation clock 30 of Figure 2.
In sample embodiments, the antennas 22, 24 include rectangular spirals
fabricated on a printed circuit board to ensure antenna-to-antenna
consistency. The number of turns for the rectangular spirals depends on the
desired value of inductance for the antenna that will be resonated with
capacitance to achieve the desired response at the operating frequency. In a
sample configuration, ten turn rectangular spirals were used for antennas 22,
24. The antennas 22, 24 are electrically small and are not resonant at the
operating frequency without the employment of an additional capacitance.
Each antenna 22, 24 is connected to a length of ordinary 50-ohm
characteristic impedance coaxial cable 26. The two cables 26 are equal in
length when the antennas are symmetrically spaced with respect to the
centerline of the vehicle and each has a ferrite sleeve 46 including several
ferrite beads slipped over the cable 26 at the ends connected to the antennas
22, 24 to serve as baluns and to suppress RF currents that would otherwise
be induced on the cable outer conductors. Induced RF currents introduce
significant system errors and must be suppressed. An operation frequency of
40.68 MHz is used in a sample embodiment. This frequency is near optimum
for this application and is allocated nationally and internationally for ISM
(Industrial, Scientific and Medical) uses which include RF heating, Doppler
based frequency or phase sensitive motion and intrusion alarms, diathermy,
cauterization and other non-communications uses. ISM frequencies are set
aside for non-communications uses, but they can also be used for
communications if the users are willing to accept the possibility of radio
interference from the primary ISM applications. The advantage for doing so
is significantly reduced equipment certification and spectrum allocation
regulatory burdens. As the maximum range of the vehicle alignment system
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described herein is a few feet at most, the probability of radio interference
from other 40.68 MHz ISM frequency users is quite remote.
[0050] An RC oscillator 30 comprised of two logic inverters 48,
resistors R6 and R7 along with capacitor C6 generates a rectangular wave
signal at twice the desired antenna commutation frequency which is then
divided by 2 by a D flip-flop 50, thereby generating a commutation clock at
the desired frequency with 50-50 duty cycle. Components R1, R3, R4, D1,
D2, and Li comprise a diode RF switch 28 controlled by the Q and not Q
flip-flop outputs. R2, R5, C4, and C5 slow the leading and trailing edges of
the switch control waveform thereby limiting switching transients. R8, C8
and associated logic inverters 52 delay the antenna commutation clock
control signal to compensate for the receiver delay. Cl, C2, and C3 are AC
(Alternating Current) coupling capacitors that block DC (Direct Current)
signals but pass the RF (Radio Frequency) signal. C7 is a bypass capacitor
that filters RF noise from the voltage source of D flip-flop 50.
[0051] Figure 5 shows the post receiver signal processing circuitry.
The output of the antenna commutation switch 28 goes to the antenna input
of a conventional narrowband FM receiver 32. The circuit includes a
consumer grade pocket sized scanning receiver, a Uniden BC72XLY
compact scanner, but any narrowband VI-1F FM receiver implementation,
analog or digital, hardware or software is acceptable. Vehicle alignment
error appears in the receiver audio output as a bandwidth limited square
wave at the antenna commutation clock frequency. Square wave magnitude
indicates alignment error magnitude; square wave polarity indicates
alignment error direction, left or right. Synchronous detection then produces
a DC voltage with amplitude proportional to alignment error and with
polarity indicating alignment error direction.
[0052] The two op-amps 54 amplify the audio signal from the FM
receiver by gains of one and minus one. Integrated circuit 56 contains three
single-pole double throw (SPDT) CMOS FET switches one of which is used as a
synchronous rectifier driven by the delayed antenna commutation switch control
signal. A low pass filter 58 comprised of resistor R16 and capacitor Cl I
follows
the SPDT switch 56 and removes all commutation frequency ripples leaving a
direct current signal with amplitude proportional to vehicle misalignment and
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polarity determined by the direction of the vehicle alignment error, left or
right
of the parking slot centerline. An absolute magnitude circuit 40 recovers the
magnitude of the vehicle displacement error while a voltage comparator 38
determines the error polarity.
[0053] The two op-amps 60, 62 are used as a post RC low pass filter
buffer amplifier and as a zero-reference voltage comparator, respectively. The
components associated with transistor 64 keep the op-amp section out of
voltage
saturation thereby avoiding the subtle problems sometimes experienced when
using op-amps in an open-loop connection as voltage comparators. The voltage
comparator 38, implemented by op-amp 62, provides a logic level signal that
indicates the polarity of the alignment error, left or right. Op-amps 66 and
associated components comprise an absolute value detector 40 providing a
unipolar representation of the alignment error magnitude independent of the
polarity of the post synchronous detector signal.
[0054] In the implementation described above, the vehicle dual sense
antennas 22, 24 and the transmission line 14 are mounted along the vehicle
centerline and parking slot center line, respectively. Offset locations as
might be
required to avoid vehicle underbody and parking slot obstacles can be
accommodated by including the appropriate offset correction in the post
synchronous detector hardware or software. In the latter situation, the
required
offset correction is provided by the ground to vehicle communications link.
Alternative Embodiments
[0055] As alternative embodiments, more complex antenna shapes and
additional antennas embedded in the pavement or affixed to the pavement
surface may be implemented to add functionality to the vehicle alignment
system. This added functionality includes the ability to determine an
approximate distance, speed, and rate of deceleration to the Ground Assembly
(GA) charging pad as the vehicle approaches using the same vehicle mounted
receiver and antenna. The distance, speed, and rate of deceleration may be
provided to a vehicle controller or the vehicle controller may calculate these
values from provided measurements. In such embodiments, the radio frequency
source (co-located or incorporated within the GA) may produce a continuous
wave beacon signal or a pulsed or otherwise modulated output on the antennas.
The error function, using both received signal strength and received phase, as
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previously described, may be used for alignment when a leaky line is
implemented.
[0056] It is noted that in the following figures the right and left
designations are from the viewpoint of the approaching vehicle and are for
purposes of illustration only and may be reversed in application. For
instance,
left and right are reversed when a vehicle is backing into a parking stall.
The X
and Y axes are as defined as in ISO 4130. All examples use the `pull-in' or
'pull-
forward' perspective for consistency. When using a 'reverse-in' parking method
(where the vehicle backs into the parking stall), the left-and-right
directions will
be reversed. [0057] Figure 6 shows an embodiment of one such improved
alignment mechanism for the approach to a magnetic induction resonant wireless
charger in a typical (e.g., 90 ) pull-in parking stall. The same mechanism may
be
deployed in other parking arrangements such as 45 parking stalls or a pull-up
(parallel parking) curbside spot(s). A "folded" or "semi-elliptical antenna"
provides alignment service to vehicles entering the parking spot from all
directions (straight-on, from the right, or from the left).
[0057] The parking stall 601 is an area defined by pavement striping,
poles, curbs or other indicia. The Ground Assembly (GA) 602 (a wireless
charger including one or more wireless charging coils and ancillary magnetic
inductive resonance communications transceiver(s)) is placed to be accessible
to
the incoming vehicle (note that in various countries, the placement of the GA
within the parking stall may be affected by local regulation, types of
vehicle(s)
to be served, and local parking customs). The folded, continuous wireline
monopole transmission antenna 603 is comprised of a left section 604 and a
right
section 605. The transmission antenna 603 is laid (either affixed to the
surface or
embedded in the pavement) to form a folded or semi-elliptical pattern, the
signal
and antenna originating at a position near the centerline 606 of the GA 602
facing the incoming direction 607 and ending adjacent to the GA 602 on the
opposite side of the centerline 606. Depending on the length of the parking
stall
601 and the frequency used, the monopole antenna 603 may extend a full or
fractional wavelength. For instance, using the ISM frequency of 13.56 MHz, a
full-wave antenna of 22.11 meters would allow a folded deployment of under 11
meters in overall length 608. The spacing of the parallel sections of the
transmission antenna 609 is such that the vehicle-mounted receiver antennas
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24 are inside the transmission antenna sections 609 after a vehicle has turned
into the parking stall 601 from a direction of travel 610.
[0058] Figure 7 shows another embodiment of an improved alignment
mechanism for the approach to a magnetic induction resonant wireless charger
in
a typical (e.g. 90 ) pull-in parking stall. The same mechanism can be deployed
in
other parking arrangements such as 45 parking stalls or a pull-up (parallel
parking) curbside spot(s). The "converging antenna" design shown in Figure 7
provides alignment service to vehicles entering the parking spot from any of
the
right, left or straight on directions.
[0059] The parking stall 701 is an area defined by pavement striping,
poles, curbs or other indicia. The Ground Assembly (GA) 702 (a wireless
charger including one or more wireless charging coils and ancillary magnetic
inductive resonance communications transceiver(s)) is placed to be accessible
to
the incoming vehicle (in various countries, the placement of the GA may be
affected by local regulation, types of vehicle(s) to be served, and local
parking
customs) for pull-in, back-in, or parking stall type (45 , 90 , parallel or
curbside)
parking. The converging leaky line transmission antenna vehicle alignment
system of Figure 7 allows for approach from either direction of travel 710 or
straight in 707. Not shown but supported is use of the converging leaky line
transmission antenna vehicle alignment system for parallel or curbside usage.
[0060] The converging wireline dipole antenna 703 includes a left section
704 and a right section 705. The leaky line-based transmission antenna 703 is
laid (either affixed to the surface or embedded in the pavement) to form a
parallel pattern, where the signal and antenna both originate from a
transmitter
either co-located or incorporated into the GA 702 located at the centerline
706 of
the GA 702. Depending on the length of the parking stall 701 and the frequency
used, the monopole antenna 703 may extend a full or fractional wavelength. For
instance, using the ISM frequency of 13.56 MHz, a full-wave antenna 703 of
22.11 meters would allow a deployment of just over 11 meters, resulting in an
overall length 708 of 5.5 meters. The physical antenna split 709 occurs next
to
the GA 702 and the apparent distance in Figure 7 is exaggerated for purposes
of
illustration.
[0061] Non-symmetric (around the centerline 706) placement of the
transmission antenna 703 is also contemplated if the offset(s) is known for
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compensation of received signal characteristics (e.g. received signal strength
and
signal phase).
[0062] Figure 8a shows a folded wireline dipole antenna 802. At one end
of the folded dipole antenna 802 is the GA 801, which hosts a beacon signal
source. The centerline 804 of the GA 801 shows the y-axis point where the
vehicle's VA (vehicle assembly) resonant inductive coil center should be
positioned for maximum wireless power transfer efficiency. The antenna 802
extends in a direction opposite the direction of approach to the limit of 1/2
the
wavelength (or 1/4th the wavelength if implemented as a half-wave antenna).
The
curved end 803 of the folded antenna 802 serves as the signal acquisition
threshold 806 where both receiver antennas 22, 24 can reliably detect the
beacon
signal regardless of the vehicle angle of approach indicating the beginning of
the
antenna 802. The GA-to-Antenna threshold 805 is the point where the signal
transmitted by the wireline dipole antenna 802 indicates the end of the
antenna
802.
[0063] Figure 8b shows a graphical representation of the signal error
function of the folded wireline dipole antenna illustrated in Figure 8a. The X-
axis 809 shows the range while the Y-Axis 808 shows the relative beacon signal
phase difference 807 between the receiver antennas 22, 24. As the vehicle
moves
over the end 803 of the folded wireline antenna 802, both receiver antennas
22,
24 begin to receive the beacon signal. At this first signal acquisition
detection
threshold 806, the received beacon amplitude and phase are nearly identical,
minimizing the error function. After the right 24 and left 22 antennas pass
the
initial ambiguous region around the end 803 of the antenna 802 (moving toward
the GA 801), the phase of the signal received by the right 24 and left 22 VA
receiver antennas begin to diverge.
[0064] As the vehicle continues to proceed toward the GA 801, the
system uses the signal strength at the right 24 and left 22 receiver antennas
to
provide a vehicle Y-axis alignment indication while the divergence in the
signal
phase at the right 24 and left 22 receiver antennas is used to provide a
vehicle X-
axis indication. The vehicle X and Y axis indications (and potentially the
computed speed and deceleration) are passed periodically to the driver, driver-
assist, or fully automated driving system to be used to control steering and
braking.
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[0065] As the vehicle continues to proceed toward the GA 801, the
vehicle alignment system continues to use the received signal strength at the
right 24 and left 22 receiver antennas to provide a Y axis alignment
indication
while the divergence in the received signal phase at the right 24 and left 22
receiver antennas approaches 180 at the antenna origin 805. At the antenna
threshold position 805, where phase equals 180 , the relative signal strength
is
expected to be reduced to zero between both receiver antennas 22, 24 giving a
secondary indication of the antenna threshold 805 having been reached, thus
providing a clear indication that the edge of the GA 801 has been reached and
that a final precise positioning system may be activated to cover the distance
from 805 to 804 or the vehicle velocity at the antenna threshold 805 may be
used
in estimating when the vehicle must be at zero velocity to be positioned over
the
GA centerline 804. Final positioning in the distance 810 from the GA edge 805
to the GA centerline 804 may be a coil alignment method (e.g. as described in
"METHOD OF AND APPARATUS FOR DETECTING COIL ALIGNMENT
ERROR IN WIRELESS INDUCTIVE POWER TRANSMISSION", Serial No.
14/910,071, Filed 2/4/2016) or using a predictive model based on velocity,
deceleration, and vehicle stopping characteristics (e.g. braking rate, vehicle
weight).
[0066] Figure 9a shows a converging wireline dipole antenna 902 having
at one end thereof a GA 901 that hosts a beacon signal source. The centerline
904 of the GA 901 shows the y-axis point where the vehicle's VA (vehicle
assembly) resonant inductive coil center should be positioned for maximum
wireless power transfer efficiency. The antenna 902 extends opposite the
direction of approach to the limit of 1/2 the wavelength (or 1/4th the
wavelength
if implemented as a half-wave antenna). The separated end 903 of the parallel
right antenna element 907 and left antenna element 908 serves as the signal
acquisition threshold 906 where both vehicle-based receiver antennas 22, 24
can
reliably detect the transmitted beacon signal regardless of the vehicle angle
of
approach. The GA-to-Antenna threshold 905 is the point where the signal
transmitted by the wireline dipole antenna 902 indicates the end of the
antenna
902.
[0067] When using the converging wireline dipole antenna 902 for
vehicle alignment, the vehicle, whether human-driven or automated, enters the
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charger-equipped parking stall, moving toward the GA 901. The vehicle-
mounted receiver antennas 22, 24 will detect the transmitted signal from the
converging wireline dipole antenna 902 at the signal acquisition threshold
906.
The transmitted signal will be received at the right 24 and left 22 receiver
antennas.
[0068] Figure 9b shows a graphical representation of the signal error
function of the converging wireline dipole antenna 902 illustrated in Figure
9a.
The X-axis 911 shows the range while the Y-Axis 912 shows the relative beacon
signal phase difference 913 between the receiver antennas 22, 24. As the
vehicle
moves over the end 903 of the wireline antenna 902, both receiver antennas 22,
24 begin to receive the beacon signal. At first, signal acquisition,
detection,
amplitude relative amplitude will indicate error in Y positioning (a zero in
relative signal strength indicates correct Y positioning) while the received
phase
will be 180 out-of-phase at initial signal acquisition at the right 24 and
left 22
receiver antennas (note that if a 1/4 wave antenna is used, the phase
difference
will be 90 ). As the vehicle moves forward, after the right 24 and left 22
antennas pass the end 903 of the antenna 902 (moving toward the GA 901), the
phase difference 913 of the signal received by the right 24 and left 22
receiver
antennas begin to diminish as the vehicle approaches the GA 901. The amplitude
relative value of the signal received at the right 24 and left 22 receiver
antennas
is used to determine Y-axis (side-to-side) axis tracking. The X and Y axis
indications are passed periodically to the driver, driver-assist, or fully
automated
driving system to be used to control steering and braking.
[0069] As the vehicle continues to proceed toward the GA 901, the
system uses the signal strength at the right 24 and left 22 receiver antennas
to
continue to produce a Y axis alignment indication while the dwindling
difference in the signal phase as received at the right 24 and left 22
receiver
provides the X-axis range-to-GA indication. At the position where phase
difference equals 0 , the right-to-left difference signal strength is expected
to be
reduced to zero. This event gives a clear indication that the edge of the GA
901
has been reached and that final coil positioning (e.g. as described in "METHOD
OF AND APPARATUS FOR DETECTING COIL ALIGNMENT ERROR IN
WIRELESS INDUCTIVE POWER TRANSMISSION", Serial No. 14/910,071,
Filed 2/4/2016).can be activated to cover the distance 910 from the GA edge
905
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to the GA centerline 904 or the vehicle velocity and deceleration rate at the
antenna threshold 905 may be used in estimating when the vehicle must be at
zero velocity to be positioned over the GA centerline 904 taking into account
vehicle characteristics such as braking rate and vehicle weight.
[0070] Figure 10a shows a vehicle alignment system for wireless power
transfer positioning using both a long (the long antenna may be shorter or
longer
than a full wavelength dependent on the deployment) leaky transmission line
1007 to provide initial guidance and a 1/2 wave 'converging antenna' 1004,
1005
(note that the folded antenna system described in Figure 6 could be used to
provide equivalent service) for alignment and ranging from the antenna end
1006 to a wireless charging pad of the GA 1003. All three antenna elements
1004, 1005, and 1007 originate at the GA 1003.
[0071] In the example of Figure 10a, the beacon signal is pulsed on the
long leaky line 1007 and is continuously transmitted on the sections of the
converging antenna 1004, 1005 to allow differentiation since all antenna lines
1004, 1005, and 1007 are transmitting in the same ISM spectrum (e.g.one of
13.56 MHz, 27.12 MHz, 40.68 MHz). The beacon signal used in the long leaky
line antenna 1007 and converging antenna segments 1004, 1005 may be either
in-phase or out of phase since the differentiation between the two antennas is
based on signal modulation (e.g. ASK, pulsing).
[0072] Figure 10b shows a graphical representation of the signal error
function of the vehicle alignment system illustrated in Figure 10a. The X-axis
1011 shows the range while the Y-Axis 1012 shows the relative beacon signal
phase difference 1009 between the receiver antennas 22, 24. As the vehicle
moves over the end of the wireline antenna 1007, both receiver antennas 22, 24
begin to receive the beacon signal at the end of the range 1016.
[0073] As the vehicle approaches the long leaky line 1007, signal
detection via either or both of the receiver antennas 22, 24 allows for
initial
guidance using the amplitude and phase difference to provide Y-axis (side-to-
side) error indication 1010. When the vehicle assembly mounted antennas 22, 24
detect the continuous beacon signal from the converging antenna structure
1004,
1005, indicating that the receiver antennas 22, 24 have passed the converging
antenna structure threshold 1006, a cutover from using the leaky line 1007 to
the
converging antennas 1004, 1005 will be performed. As shown in Figure 10b, this
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cutover results in an abrupt change (after the region 1017 where the three
transmitted signals co-channel interference creates an ambiguous area where
signal differentiation is impeded) in received phase 1008 as the received
beacon
signal changes and the relative received signal phase difference 1009 goes to
180 out-of-phase. Once the signal source changeover is accomplished, the
vehicle alignment and ranging proceeds as detailed in Figure 9b (or as in
Figure
8b if a folded antenna is used).
[0074] Once the vehicle receiver antennas have approached the zero-
phase difference threshold 1002, the vehicle assembly-based transmitter can
initiate communications with the ground assembly receiver(s). A final
positioning method (or predictive model based on the velocity determined by
the
ranging provided by use of the converged antenna system) can be used for the
distance 1014 between the zero relative phase difference threshold 1002 and
the
midline 1001 of the GA 1003.
[0075] This multi-antenna approach may also serve as a 'soft-fail' system
where failure of either antenna structure or transmission facility will not
preclude operation of the other.
[0076] An optional short-range transmitter unit 1013 (e.g., radio-
frequency transmitter) may be included at the end of any leaky line
installation.
The radio-frequency transmitter unit 1013 may include a transmitter, a
processor, and a memory as well as a wired communications subsystem for
receiving data from or via the GA 1003 via the leaky line cable 1007. This
transmitter unit 1013 may broadcast its GPS location and the capabilities of
the
charging station (e.g. power levels offered, power types (AC/DC) available,
connector types supported, payment forms available (e.g. virtual wallets
support,
online account(s) supported, memberships supported, swipe card, credit, debit,
club cards)). The transmitter unit 1013 is also powered via the leaky line
1012
using a DC offset to the leaky line beacon signal(s).
[0077] During a charging session (i.e. once a vehicle is positioned over
the GA 1003), the transmitter unit 1013 may be turned off or may broadcast
information to other passing vehicles (e.g. the charger is in use, time left
in
charging session). Information may be updated from the GA 1003 via the leaky
line 1007 using signal modulation (e.g. pulsed, amplitude modulated).
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[0078] In any of the described installations, a failed pre-charging session
alignment may be reset by moving off the GA and restarting the alignment
process when a range measurement above threshold (e.g. when sufficient range
is obtained for correction of any Y-Axis (side-to-side) error) can be
obtained.
[0079] While various implementations have been described above, it
should be understood that they have been presented by way of example only, and
not limitation. For example, any of the elements associated with the systems
and
methods described above may employ any of the desired functionality set forth
hereinabove. Thus, the breadth and scope of a preferred implementation should
not be limited by any of the above-described sample implementations.
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