Device and method for guiding electric vehicle

Abstract

To provide a pad module for guiding an electric vehicle to a position where energy can be transmitted between a ground coil and a vehicle coil, and a guide power transmission system, device, and a method.SOLUTION: Position signal devices 32 to 34 are attachable to a ground coil 14 and a vehicle coil 24. At least one position signal device is associated with one of the coils and two or more position signal devices are associated with the other coil. Each position signal device transmits and / or receives a signal for or from other position signal devices. The signal is processed in order to obtain time-related information from the position signal. The information is obtained using at least two positioning protocols from a set of protocols including time of flight, two-way ranging, time difference of arrival, and phase difference of arrival. This determines distance between the signal devices and thus a relative position of the ground coil and the vehicle coil.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] An apparatus for guiding an electric vehicle to a position where a magnetic coil on the vehicle is disposed with respect to a supply magnetic coil at a charging location so that energy can be transferred between the vehicle coil and the supply coil; a pad module for use with other pad modules to transfer power by magnetic force in an electric vehicle charging system; and a method for guiding an electric vehicle at a charging location to a position where a vehicle magnetic coil is disposed with respect to a ground magnetic coil so that energy can be transferred between the vehicle coil and the ground coil.

Background Art

[0002] Wireless power supply technology is increasingly being used to supply power from a power source to various devices, from small portable electronic devices such as mobile phones and tablet terminals that require several watts of power to electric vehicles that require several kilowatts of power. In addition to the convenience of not having to connect the device for power supply or charging, since there are no wires or cables, the desktop and parking space are kept tidy, and at the same time, the risk of tripping and impact is reduced. Methods of wirelessly transmitting power include capacitive coupling and inductive coupling, both of which have advantages over resistive (i.e., wired) coupling for the purpose of supplying power to a device.

[0003] A wireless power supply system can be designed to supply any power from a fraction of a watt, several watts to several kilowatts from a power source across a gap to a device or load. Generally, the gap is an air gap between magnetic coils, but there are also other methods such as supplying power between capacitor plates. It can also be designed to operate at a fixed or variable frequency, which is effective when the state of the load changes.

[0004] The energy supplied in this way can be used, for example, to supply power to an electronic circuit or to supply power to a device. This includes supplying power to consumer devices such as mobile phones and tables. It also includes driving the electric motor of an electric vehicle or charging the battery in a circuit or vehicle. Several watts of power are required to charge the power supply or battery of a mobile phone, and several kilowatts of power are required to power the motor or charge the battery of an electric vehicle. The larger the battery, circuit, or motor, and the faster the battery charging speed, the greater the power that must be transmitted across the air gap.

[0005] Since wireless power supply technology has developed in various technical fields, different terms are used to express essentially the same thing. Terms such as "magnetic coupling", "magnetic induction", "inductive power transfer", "inductive charging", "resonant inductive power transfer" are common. Although there are minor differences, these terms are generally used broadly and interchangeably to refer to a system that transfers power from a power source to a load across an air gap by a magnetic field. Here, the term "guided charging system" or ICS is used to identify this type of system.

[0006] Similarly, there are words that refer to the various elements that make up a guided charging system (ICS). An ICS basically consists of devices related to the power source and devices related to the apparatus. The power supply device is composed of a circuit that converts the energy from the power source into a form suitable for driving the coil. Similarly, the apparatus device converts the energy guided to the coil by the magnetic field into a form suitable for supplying power to the apparatus or charging the battery in the apparatus.

[0007] The guided charging system can be used for charging the battery of an electric vehicle. The driver parks the vehicle on a charging device installed on the ground, and the charging device can magnetically couple with the on-vehicle charging device to transfer energy to the battery. In the case of a self-driving vehicle, by performing guided charging, after the vehicle travels to the charging location, there is no need to manually connect to the power source. If necessary, power can be supplied from the vehicle's battery to a power source (such as the power network of a smart home or the power grid of an electric power company).

[0008] In a guided charging system (ICS) used for electric vehicles, power supply devices with various names are used, such as a ground assembly that can be connected to the main power supply, a ground pad, and a ground pad module (GPM). The device is variously known as a vehicle assembly, a vehicle pad, or a car pad module (CPM), can be mounted on a vehicle such as an automobile, and provides energy for charging the vehicle's battery. In many cases, the naming depends on which language a certain manufacturing company adopts. Of course, the ICS for electric vehicles can be applicable to a variety of vehicles including large vehicles such as automobiles, trucks, buses, and trams, and is not limited to road-going automobiles. Here, in order to identify two parts of the ICS for electric vehicles, the terms GPM (Ground Pad Module) and CPM (Car Pad Module) will be used.

[0009] Other terms that vary depending on the implementation of the ICS include "magnetic coil", "inductive coil", "antenna", etc. These terms are also used loosely and essentially interchangeably to describe the part of the guided charging system that transfers energy through an air gap. However, for the sake of accuracy, it should be pointed out that this element is a coil rather than an antenna. This is because at typical operating frequencies, the element transfers energy in the near field where only a magnetic field exists.

[0010] Antennas are designed considering the electromagnetic fields formed when the radiated energy passes from the near field to the far field. The location where the near field ends and the far field begins varies depending on the characteristics of the transmitting device (such as coils and antennas). In wireless power transfer applications, due to the size of the air gap and the frequency at which the system operates, it is usually not necessary to have an exact definition as it is firmly placed in the near field. However, the aforementioned "magnetic coils", "inductive coils", and "antennas" are used interchangeably by those involved in the design of wireless power transfer devices and systems.

[0011] The guide charging system can use magnetic coils alone or in combination with other tuned or tunable elements. In the power transfer application of an electric vehicle, the ground pad module can include a coil in combination with the associated drive electronics, or it can include a coil where some or all of the associated electronics are provided in a separate housing. In any case, the coil of the ground pad module is used to transfer power through the magnetic field. Similarly, the car pad module can include a coil in combination with the associated control electronics, or it can include a coil where some or all of the associated electronics are provided in a separate housing. In any case, the coil in the car pad module is used to receive power through the magnetic field.

[0012] What is noted in the design of a wireless charging system is the accurate alignment of the ground coil and the vehicle coil. Poor alignment results in poor energy transfer efficiency. When the system operates, a large amount of energy is transferred by the magnetic field through the space between the ground pad module and the vehicle pad module. Even in a small household system in use, a magnetic field capable of transferring 2-3 kW of energy between the pads is generated. Other systems operate at even higher power levels. An inefficient link between the ground and the vehicle pad causes stray currents in the conductive elements of the system. The energy obtained from this is converted into heat. That is, not only is energy lost, but it also causes heating, which is clearly undesirable.

[0013] Against this background, efforts have been made in the design of a wireless charging system to assist an operator (e.g., the driver of a vehicle) in placing the vehicle coil over the ground coil in order to optimize power transfer and minimize losses and associated problems. SUMMARY OF THE INVENTION

[0014] As defined in the claims, the present invention provides an apparatus for guiding an electric vehicle to a position where a magnetic coil on the vehicle is disposed relative to a supply magnetic coil at a charging location so that energy can be transferred between the vehicle coil and the supply coil; a pad module for use with other pad modules to transfer power magnetically in an electric vehicle charging system; and a method for guiding an electric vehicle at a charging location to a position where the vehicle magnetic coil is disposed relative to the ground magnetic coil so that energy can be transferred between the vehicle coil and the ground coil.

[0015] By an apparatus and method for determining the relative position of a ground coil and a vehicle coil, an electric vehicle can be guided to a position where energy can be transferred between the ground coil and the vehicle coil. The position signal device can be attached to the ground coil and the vehicle coil. At least one signal device is associated with one of the coils, and two or more signal devices are associated with the other coil. Each signal device can transmit, receive, or transmit and receive signals for or from other signal devices. The signals are processed to obtain time-related information from the position signals. Information is acquired using at least two positioning protocols from a group of protocols including time of flight, two-way ranging, time difference of arrival, and phase difference of arrival. Thereby, the distance between the signal devices, and thus the relative positional relationship between the ground coil and the vehicle coil, can be grasped.

[0016] The present invention and its features are specifically described in the claims and will become apparent to those with appropriate technology from consideration of the following detailed description, given by way of example with reference to the accompanying drawings, together with its advantages.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

DETAILED DESCRIPTION OF THE INVENTION

[0018] Referring now to FIG. 1 of the accompanying drawings, there is shown a guided charging system (ICS) 10 for use in charging the battery of an electric vehicle. The ICS 10 is composed of a ground pad module (GPM) 12 including a ground or supply coil 14 and a drive circuit 16 coupled to a power supply 18. The power signal from the supply 18 is adjusted by the drive circuit 16 and made into a form suitable for application to the supply coil 14. The coil 14 is driven by the application of this power signal (represented as current I and voltage V) to generate a magnetic field 20.

[0019] The supply 18 may be, for example, a household voltage supply of 110V or 220V. Such household equipment has a limit of 2 - 3kW and usually takes several hours to charge the battery. A large power supply such as a polyphase (multiple) power supply of 415 volts or more can complete the charging more quickly. In commercial and industrial applications, a larger power supply, that is, faster charging, is possible.

[0020] The size and form of the ground pad module 12 depend on the technical requirements of the system. The supply coil 14 is depicted as circular in FIG. 1, but can be any polygon or ellipse. The coil 14 may be configured as a solenoid, arranged in a double D configuration, or any of the widely available coil topologies. The exact form is determined by the technical requirements of the system and everyday design choices. As an image of the size, the ground pad module 12 is typically about 600 mm wide. The height of the GPM 12 is desirably made as low as possible to avoid the risk of the GPM catching or tripping on the underside of the vehicle.

[0021] The guided charging system 10 also includes a car pad module (CPM) 22. In use, the CPM 22 is placed on an automobile (not shown), such as under the chassis or the floor pan, at a location determined by design considerations. When the automobile travels over the GPM 12 and the CPM 22 placed thereon, energy can be transferred from the GPM to the CPM. The magnetic field 20 is converted into an electrical signal (represented as current I and voltage V) by the vehicle or vehicle coil 24, and the electrical signal is adjusted by the drive circuit 26 to deliver energy to the battery 28 and thus be in a form suitable for charging the battery 28.

[0022] Similar to the ground pad module (GPM) 12, the size and form of the CPM 22 are governed by the technical requirements and choices made when designing the guided charging system 10. The car pad module (CPM) 22 is also provided in a package. Again, the exact form of the vehicle coil 24, and thus the shape and size of the CPM 22, are largely determined by technical requirements and design choices. The coil 24 does not have to be circular as depicted, and in fact does not even have to have the same form or topology as the coil 14 in the ground device 12. The space inside the vehicle is limited. Typically, the goal is to make the CPM 22 as small as possible, for example about 300 mm wide.

[0023] The controller 30 serves to control the operations of the GPM 12 and the CPM 22. Although shown as a single unit in FIG. 1, the controller 30 may be entirely provided in the GPM 12 or the CPM 22, or elements may be arranged in the GPM 12 and the CPM 22. In particular, the controller 30 provides a way for the two parts 12, 22 of the system 10 to communicate with each other, as represented by the dashed lines 31a and 31b in the drawing. The communication medium may be any one of widely available wireless protocols including Wi-Fi and Bluetooth.

[0024] In use, information is transmitted between the GPM 12 and the CPM 22, for example, to control operations, such as controlling the generation of the magnetic field 20 to optimize power transfer and minimize losses. A safety function (not shown) that sends a signal to the controller 30 indicating when power transfer may be started or ended, or when power transfer must be interrupted, may be included in the system 10 due to dangerous situations such as foreign objects or living things entering the magnetic field 20.

[0025] One convenience of the ICS 10 is that the vehicle battery 28 can be charged simply by parking the vehicle on the ground pad 12 at a position where the car pad module 22 and the ground pad module 12 are aligned. A vehicle guide and alignment device is provided to assist the driver in correctly positioning the vehicle, and thus the car pad module 22, with respect to the ground pad module 12.

[0026] The guide charging system 10 includes a positioning device 40 or a subsystem shown in FIG. 2 of the accompanying drawings. The positioning device 40 is provided with a number of position signal devices 32, 33, and 34 that transmit or receive or transmit and receive signals that enable determination of the relative position between the GPM 12 and the CPM 22. In FIG. 2, two signal devices 32, 33 are shown on the ground pad module 12 and one is shown on the car pad module 22, but it will be understood that the signal devices can be arranged in reverse, that is, one on the GPM 12 and two on the CPM 22.

[0027] The operation of the signal devices 32, 33, 34 is controlled by the positioning device 40. Note that the positioning device 40 is shown separately from the guide charging system (ICS) 10 for convenience of explanation. Similar to the ICS controller 30 shown in FIG. 1, the positioning device 40 may be included in the ICS system 10 or may be arranged parallel to the ICS system 10. Also, it may be arranged on the ground pad module GPM 12 or the car pad module CPM 22, or may be distributed between the GPM and the CPM. In fact, the function of the positioning device 40 may be partially or wholly integrated into the ICS controller 30.

[0028] In the initial stage of the popularization of wireless vehicle charging, it is expected that automobile manufacturers will provide customers with the entire charging system including, for example, both the GPM and the CPM. With the development of the market, in order to aim for the reliability, weight reduction, and cost reduction of the CPM, the supply of the GPM may be entrusted to a third party. Therefore, in the future, a larger proportion of the system control including the positioning device 40 in FIG. 2 may be arranged on the GPM. Naturally, a part of the positioning device will remain on the CPM or the vehicle, or both. Exactly how much is a matter of selection according to the constraints and practicality in the design specifications.

[0029] The positioning device 40 consists of a process controller 42 that provides two main tasks, represented at a high level by a signal processor 44 and a positioning controller 46. At a high level, the signal processor 44 processes the transmitted and received signals 47, 48 associated with each of the signal devices 32, 33, 34 and extracts time-related information therefrom, and thus distance data. And again at a high level, the positioning controller 46 uses the information and data from the signal processor 44 to determine the position relative to a coordinate system or reference system.

[0030] These tasks can also be provided separately. However, in practice, the operations are interrelated, so it would usually make engineering and commercial sense to provide them as a unit as shown in the figure. In fact, the processing and positioning functions of the process controller 42 may be shared between the GPM12 and the CPM22, or replicated in both the GPM and the CPM.

[0031] The process controller 42 communicates with the signal devices 32, 33, 34 associated with the GPM coil 14 and the CPM coil 24 via communication channels 41a, 41b. The channels 41a, 41b serve to transfer data between the various parts of the positioning device 40. This is similar to the way the controller 30 of the system 10 in FIG. 1 controls the coupling of the GPM12 and the CPM22. It can be seen that the channels 41a, 41b can be included in or be part of the channels 31a, 31b associated with the controller 30. In fact, some or all of the functions of the process controller 42 can be included in or provided by the ICS controller 30. The distribution of the various elements of the positioning device 40 is a matter of design choice governed by the requirements and practicality of a given implementation.

[0032] The process controller 42 determines the position of the coils with respect to the coordinate system (x, y) 49. The position of the coordinate system (x, y) 49 is arbitrary and can be defined at any position. In practice, it is convenient for the coordinate system to be centered on one of the coils 14, 24 and the position of the other coil to be defined relative thereto. Usually, the coordinate system 49 will be defined with reference to the stationary coil within the GPM. For example, the origin (0, 0) of the coordinate system can be conveniently located at the center of the CPM 22 with the X-axis aligned with the traveling direction of the vehicle (not shown).

[0033] The signal devices 32, 33, 34 are shown as being arranged at arbitrary positions on the coils 14, 24. In practice, the positions of the supply and vehicle coils 14, 24 relative to each other are calculated at known positions on each coil, for example their centers. However, in a given system, it may not be possible to accurately position the signal devices 32, 33, 34 at the centers of the coils 14, 24. Other devices may be preferentially arranged there.

[0034] In fact, there is no reason why the signal devices must be arranged within or on the ground pad module 12 or the car pad module 22. They can be arranged at the edge of the parking space or at any position of the vehicle. As long as the offsets from the centers of the coils to each of the signal devices 32, 33, 34 are known, accurate position data can be calculated.

[0035] Signal devices associated with fixed elements or positions are sometimes called anchors, and devices associated with moving elements or positions are sometimes called tags. Anchors and tags essentially do the same thing, namely, send, receive, or send and receive signals in a way that enables the position of the tag to be determined relative to the position of the anchor. "Anchor" and "tag" are convenient labels for identifying whether a signal unit is associated with a fixed position (e.g., GPM 12) or a movable or moving position (e.g., CPM 22).

[0036] In the ICS10 of FIG. 1 and the positioning device 40 of FIG. 2, the signal devices 32, 33 are positioned on the GPM12 with respect to the coil 14. Similarly, the signal device 34 is arranged on the CPM22 with respect to the coil 24. Since the GPM12 is deployed on the ground, it is easy to consider that the signal devices 32, 33 are related to a fixed position. Similarly, since the CPM22 is deployed on the vehicle, it is easier to consider that the signal device 34 is associated with a moving position. However, mathematics functions similarly for the signal device 34 related to the ground or the GPM12 and the signal devices 32, 33 on the vehicle or the CPM22.

[0037] Generally, the signals transmitted between the signal devices of the positioning system are ultra-wideband (UWB) signals. When processing UWB signals, very narrow pulses are obtained, so the time resolution is high, and the accuracy of tag position calculation is improved. Also, since UWB has narrow delay pulses, the pulses do not overlap and do not cancel each other out. Therefore, the robustness against multipath is also high. Signal devices using UWB signals are available.

[0038] There are several ranging techniques that can process the signals transmitted between the signal devices 32, 33, 34 to determine the relative positions of the devices 32, 33 in the GPM12 and the device 34 in the CPM22. These are generally known as positioning protocols.

[0039] As one of the positioning methods, time of flight (ToF) or time of arrival (ToA) is known. Time of arrival is the simplest and most common ranging technique and is most commonly used in the Global Positioning System (GPS). This method is based on knowing the exact time when the signal is transmitted from the transmitting signal device, the exact time when the signal arrives at the receiving signal device, and the moving speed of the signal (basically the speed of light of the radio signal).

[0040] The arrival times applicable to the positioning device 40 are shown in FIG. 3. A signal is transmitted from device 34 and received by devices 32 and 33. The operations of the devices are synchronized by the process controller 42. By knowing the time when the signal is transmitted from device 34 and arrives at device 32 and the time when it arrives at device 33, the path lengths between device 34 and 32 and between device 34 and 33 can be determined. And it provides sufficient information to calculate the relative positions.

[0041] FIG. 4 shows the coordinates (x0, y0) and (x, y) associated with the transmitting device 32 and the receiving device 34 separated by a distance d. Also shown are the times t s and t a associated with the synchronized transmission (propagation) and arrival (reception) of the signal between devices 32 and 34. Note that in FIG. 4, the direction of signal propagation is opposite to that in FIG. 3. This is to point out that the decision to make device 34 the transmitter and devices 32 and 33 the receivers, or vice versa, is simply a design choice. Similarly, the relative position may be expressed as the relative position with respect to the ground pad module (GPM) 12 in FIG. 1, or it may be expressed as the relative position with respect to the car pad module (CPM) 22.

[0042] Referring to FIG. 4, the distance d from the signal device 32 at the reference position (x0, y0) to the position of the target signal device 34 at the position (x, y) can be calculated using a simple formula.

[0043]

Equation

[0044] Here, t s is the time when the signal is sent, t a is the arrival time of the signal, and c is the speed of the wireless signal, i.e., the speed of light.

[0045] Using this distance d, the position of the target signal device 34 can be determined. In two dimensions, a circle of the following equation is obtained.

[0046]

Number

[0047] A single signal between two signal devices 32, 34 provides only enough information to determine that device 34 is on the circumference of a circle of distance d from the coordinates (x0, y0), i.e., the position of device 32. Another signal device 33 provides similar information related to the position of its second signal device 33.

[0048] As shown in Figure 5, by processing the signal between signal device 32 and signal device 34, the system can determine that signal device 34 is located somewhere on the circumference of circle 36 centered on signal device 32. Similarly, by processing the signal between signal device 33 and signal device 34, the system can determine that signal device 34 is located somewhere on the circumference of circle 37 centered on signal device 33. Device 34 is located at the intersection of these lines 36, 37.

[0049] Therefore, one of the drawbacks of using a combination of one plus two signal devices as shown in Figures 3, 5, and 6 is positional ambiguity. The calculation involves the above quadratic equation, which gives two possible solutions for the position of device 34. As shown in Figure 5, device 34 may be in the position represented by box 34' or in the position represented by box 34". Only one of the solutions 34' or 34" is correct.

[0050] It may also become apparent that a certain solution is infeasible due to the surrounding environment. For example, position 34' may be in an area that does not correspond to a parking space or may be behind a wall, for example. However, in other situations, such as in a public parking facility, there may not be enough information to determine whether the vehicle is on the left or right side of devices 32, 33 and thus whether it is on the ground pad module 12. The left and right mentioned here are relative expressions. Depending on the orientation of the ground pad module and the vehicle, it can be either in front or behind.

[0051] In such a situation, the system 40 may be designed to eliminate inaccurate calculation positions. If that is not possible, additional information is required to ensure an accurate determination of the relative position.

[0052] In FIG. 6, a third signal device 38 is added to the ground pad module 12 (GPM - not shown in FIG. 6) to provide additional distance information regarding the signal device 34 on the car pad module 22 (CPM - not shown in FIG. 6). As can be seen from the figure, the additional signal device 38, being located on the circumference of a circle 39 centered on the device 38, enables the calculation of the position of the device 34. The point where the circumferences of three circles coincide uniquely indicates the position where the signal device 34 is located.

[0053] To increase the positioning accuracy, additional signal devices may be further included in the system. Combinations of 4 plus 1 or 4 plus 2 are more accurate than systems based on combinations of 3 plus 1 or 3 plus 2 signal devices. However, the cost and weight of the system increase. In fact, depending on the protocol, more devices may be required to obtain sufficient data for position calculation. Of course, this trade - off means that more elements increase the cost and the weight of the GPM or CPM. Therefore, the number of signal devices and their positions on the GPM or CPM become design choices governed by engineering constraints such as cost, weight, and accuracy.

[0054] Another positioning protocol known as two - way ranging (TWR) is shown in FIG. 7. A signal is transmitted by the device 34. This signal is received by the devices 32, 33 which send the signal back to the device 34. The time it takes for the signal to travel to the devices 32, 33 and back to the device 34 is proportional to the distances between the device 34, 32 and the device 34, 33. This method is effective when clock synchronization is not possible.

[0055] With this two-way transmission approach, the difference in clocks between the transmitting device and the receiving devices 32, 33, 34 can be compensated. Naturally, the internal delay of the devices, for example, the delay between the time the device receives a signal and then transmits a signal in response, is also taken into account when determining the time and thus calculating the distance. Once the distance is determined, it is easy to calculate the relative position.

[0056] The time difference of arrival (TDoA) is similar to the time of arrival (ToA) in that it depends on the arrival time of the signal. The time difference of arrival (TDoA) is more versatile than ToA in that it does not require the time when the signal was transmitted from the target signal device 34 (see FIG. 4). TDoA only requires knowledge of the signal's propagation speed (such as the speed of light of radio waves) and the times when the signal devices 32, 33 received the signal.

[0057] The process controller 42 synchronizes the operations of the signal devices 32, 33 in time so as to be able to determine the time difference of arrival. The difference in arrival times is used to calculate the difference in distances between the target signal device 34 (i.e., the device whose position is to be determined) and the two reference signal devices 32, 33 (i.e., the devices whose positions are known).

[0058] This distance difference Δd is calculated by the following formula.

[0059]

Equation

[0060] Here, Δt is the difference in arrival times at the other two signal devices 32, 33. From this, Equation 4 is derived, where (x1, y1) and (x2, y2) are the known positions of the signal devices 32, 33, and (x, y) is the position of the signal device 34.

[0061]

Equation

[0062] Other ranging protocols suitable for use in calculating the relative positions of the ground pad module (GPM) 12 and the car pad module (CPM) 22 of FIG. 1 include the received phase difference of arrival (PDoA). In a PDoA system, two receiving signal devices are placed in close proximity within half a wavelength of the transmitted signal to avoid the ambiguity associated with a phase shift of 180 degrees (±π / 2). PDoA processing by the process controller 42 yields data representing an angle. Data from multiple receivers can be used in triangulation calculations to determine position.

[0063] In addition to what has been described with reference to FIGS. 4, 5, and 6, other ranging protocols and mathematical approaches can be used to calculate position from time information. The orthogonal (x, y) coordinates (see FIG. 2 - 49) can be replaced with polar (r, Φ) coordinates. The mathematical approach selected depends to varying degrees on the ranging protocol used. The mathematics are documented elsewhere and are not described in detail herein for the sake of brevity.

[0064] A unique signal device is available that uses a two - way ranging approach called "asymmetric two - sided bi - directional ranging" that uses various techniques to cancel out errors and other inaccuracies. Devices using this asymmetric approach are suitable for use in system 40.

[0065] FIG. 8 shows cars 51, 52, 53 with respect to parking spaces 54, 55, 56. The ground pad module GPM12 is arranged in parking space 54 in a convenient position for car 51 to park with its car pad module CPM22 arranged such that the coil (not shown) within CPM22 and GPM12 are aligned. Four position signal devices 58a - 58d are provided in the vicinity of parking space 54, for example, around the parking space, and signals are transmitted between those signal devices 58a - 58d and the signal devices 34a, 34b of CPM22 on the automobile 51.

[0066] Obviously, signal devices 58a - 58d are not arranged on GPM12. However, the positions of GPM12 and the signal devices are static, and thus their spatial relationship is known. Therefore, the positions of signal devices 58a - 58d can be defined, for example, by offsets I, J, K, L with respect to the center of the coil in CPM12. The position of GPM12 can be easily determined from the spatial relationship and is thus also known.

[0067] When vehicle 51 approaches parking space 54, position signals are transmitted between devices 58a - 58d associated with parking space 54 and devices 34a, 34b associated with CPM22 on vehicle 51. The positions of devices 34a, 34b, and thus the position of CPM22 and the position of vehicle 51, are calculated by processing the signals in the manner described above. The position is repeatedly calculated to provide guidance information to the vehicle moving towards the parking space.

[0068] The ground pad module 12 of parking space 55 includes signal devices 32, 33 that cooperate with similar devices on the car pad module 22 of vehicle 52 when the vehicle enters the parking space. This arrangement operates in the same manner as already described with reference to FIGS. 1 and 2.

[0069] Vehicle 53 already parked in space 56 has position signal devices 31a - 31d arranged at different positions on its vehicle body. Each of devices 31a - 31d is offset from CPM22 by offset vectors i, j, k, l. Therefore, the position of CPM22 is known and is considered when guiding vehicle 53 into space 56.

[0070] The positioning system as described in this specification provides very accurate position information up to a few centimeters when stationary signal devices 32, 33 (also known as anchors) surround a region (e.g., region 59 in FIG. 8) and a moving signal device 34 (also known as a tag) is within the defined region.

[0071] The positional accuracy may decrease when the signal devices are in close proximity. This can be a problem when the signal devices are placed in close proximity on the ground pad module 12 and / or on the car pad module 22, as in the case of the parking space 55 and the car 52 in FIG. 8. In this situation, the GPM signal devices (anchors) will typically be at intervals of less than 600 mm (the typical width of the GPM), and the CPM signal devices (tags) will be at intervals of less than 300 mm (the typical width of the CPM).

[0072] If possible, placing the anchors 58a - 58d around the parking space 54 (see FIG. 8) would help mitigate this problem. Similarly, placing the tags 31a - 31d around the car 56 in FIG. 8 would help improve the accuracy compared to using signal devices integrated on the CPM. Such arrangements, of course, depend on the constraints of a particular implementation.

[0073] Also, when the signal device or tag on the vehicle is outside the defined area 59, the positional accuracy can drop rapidly with distance. This is shown in FIGS. 9 and 10, where the graphs show several lines representing different levels of accuracy or tolerance. These graphs were generated during simulation and are close to the experimental results obtained subsequently. For each graph 70, 74, the horizontal axis represents the distance (D) in meters between the ground pad module 12 and the car pad module 22 (see FIG. 1). The vertical axis represents the accuracy (A) of the calculated distance in meters.

[0074] In FIG. 9, the line 72 represents, for the sake of explanation, the positioning to any level of accuracy considered acceptable for a given designed system. When the vehicle is outside the parking space (e.g., the car 51 in FIG. 8), a tolerance or accuracy of about 8 - 10% would be quite acceptable. As the vehicle approaches and enters the parking space, higher accuracy is required as the car pad unit moves to align with the ground pad unit, as in the case of the car 52 in FIG. 8.

[0075] The same line 72 is shown on a larger scale in graph 74 in FIG. 10. Merely to distinguish graph 74 from graph 70, this line has been given the designation 72’. The line is the same in both. In FIG. 10, graph 74 is shown over a smaller distance from zero to 1 m as compared to the scale from zero to 14 m of graph 70 in FIG. 9. Here for purposes of explanation, the positioning system is required to have a tolerance of 2 - 3 cm, i.e., the calculated position is within 2 - 3 cm of the actual position when the distance between the GPM and CPM is less than 0.5 m.

[0076] In addition to lines 72, 72’ representing the desired tolerance or accuracy, both graphs 70 and 74 show two lines 76, 76’ and 77, 77’ representing the accuracy of a system in which the time difference of arrival (TDoA) is developed as a positioning protocol. Here, the signal device is wireless and has antennas with slightly different axial and diagonal characteristics. Lines 76, 76’ show the accuracy along the axis and lines 77, 77’ show the accuracy along the diagonal. Both of lines 76’ and 77’ are close to and below the desired tolerance line 72’ in a narrow range of ~0.4 m or less and are within the tolerance range. The sharp change of line segment 72’ from diagonal to horizontal at 0.5 m is due to the way this tolerance line 72’ is defined. Line 76’ is slightly above the sharp change of line 72’. This is due to an abrupt definition and there is actually little difference.

[0077] As can be seen from both FIGS. 9 and 10, the TDoA lines 76, 76’ and 77, 77’ rapidly exceed the required tolerance lines 72, 72’ at distances over 0.5 m. This means that the TDoA can provide acceptable accuracy when the vehicle reaches the parking space and the tag is inside, but cannot provide the desired tolerance range at greater distances outside the parking space.

[0078] However, TDoA also has the advantage of being able to provide angle information. This angle information is valid even outside the parking space. The angle information can still be used in position calculations. Of course, the angle information is also valid when aligning vehicles 51, 52, and 53 in parking spaces 54, 55, and 56 (see Figure 8).

[0079] Although not shown in Figure 9 or Figure 10, it should be noted that the Phase Difference of Arrival (PDoA) protocol also provides good angle information that is useful for both the distance of the vehicle within the space and the final alignment. Therefore, PDoA may be used in the same way as TDoA or instead of TDoA.

[0080] The graphs in Figures 9 and 10 also show lines 78, 78' representing the accuracy of the Two-Way Ranging (TWR) or Time of Flight (ToF) arrangements. As seen in Figure 10, the accuracy of this ToF positioning protocol is the same as that of the TDoA protocol at distances of ~0.5 m or less. However, it is significantly better at distances greater than ~0.5 m and well within the desired tolerance range. Therefore, ToF is suitable for guiding automobiles and other vehicles over several meters towards a parking space.

[0081] One way to implement the two approaches is, for example, as shown for vehicle 52 and space 55, to use TWR or ToF outside the parking space and switch to TDoA or PDoA when the vehicle enters the space to guide the vehicle. However, by combining and using the two positioning protocols both outside and inside the parking space, higher accuracy can be obtained than using only one. Briefly, TWR is excellent for distance and TDoA is excellent for angle. In particular, outside the parking space, it is more accurate than using either alone. There is no need to add hardware to implement the two different protocols. The same signal device can be used for both.

[0082] As described above, it is assumed that the signal operations performed by the positioning system are carried out using wireless signals transmitted, received, or both transmitted and received by signal devices 32, 33, and 34. Although the use of wireless signals is common, it is not the only way.

[0083] Other suitable signal devices include ultrasonic time-of-flight sensors that transmit ultrasonic pulses and listen for echoes returning from targets within the sensor's field of view. By calculating the distance based on the time of flight (ToF) and the speed of sound, the sensor can determine the distance of an object relative to the device.

[0084] Another method is to use a beacon as the transmission signal unit and transmit signals to a plurality of receivers arranged to measure its power. By comparing the power of the received signals at different receivers, the receiver that "heard" the beacon with the highest power level is considered to be the closest to the beacon.

[0085] Modern vehicles are increasingly designed to include more signal devices, sensors, and monitoring subsystems to control many of the daily operations related to the vehicle's driving and operation. For cost reduction, and depending on the equipment installed in a particular vehicle model, it may be possible to assist in the alignment operation by using some of the other equipment. Appropriate existing sensors provided in other subsystems can be deployed for the above-described distance determination. For example, data from an accelerometer or inertial sensor provided in the vehicle can be supplied to the process controller 42 (Figure 2) to provide supplementary angular information.

[0086] Modern vehicles typically include a user interface, i.e., a monitor within the dashboard that displays vehicle information useful while stationary and in motion. A positioning device may be configured to output position data to the user interface to display position information that assists a driver when parking the vehicle so that the coils of a charging system are aligned. Data from a coil positioning system may be displayed to provide a visual aid for parking. Alternatively, the data may be provided to a self-parking system to include coil alignment in its functionality. In the case of a motor vehicle that includes a self-parking function, the output data of the positioning device is supplied to the self-parking device, which can assist the device in guiding the motor vehicle to the correct charging position, e.g., in a garage or parking space.

[0087] With reference to the accompanying drawings, a device for guiding an electric vehicle to a position where a magnetic coil on the vehicle is disposed relative to a supply magnetic coil at a charging location so that energy can be transferred between the vehicle coil and the supply coil; a pad module for use with other pad modules to transfer power by magnetic force in an electric vehicle charging system; and a method for guiding an electric vehicle at a charging location to a position where the vehicle magnetic coil is disposed relative to a ground magnetic coil so that energy can be transferred between the vehicle coil and the ground coil have been described, but these are described by way of example only, and modifications and variations that will occur to those having appropriate knowledge and skills can be made without departing from the spirit and scope of the invention as defined in the appended claims and their equivalents.

Claims

1. 1. A pad module for use with other pad modules to magnetically transfer power in an electric vehicle charging system, said pad module comprising: at least one signaling device for transmitting or receiving positioning signals to or from two or more signaling devices associated with said other pad modules, or two or more signaling devices for transmitting and / or receiving positioning signals to or from at least one signaling device associated with said other pad modules, and a process controller coupled to one or more of the signal devices, Controlling the transmission and / or reception of location signals by said signalling device; processing the position signals to obtain time related information relating to differences between transmission and reception of signals and between a plurality of received signals; and A process controller is provided from which the distance between the signal device associated with the pad module and the signal device associated with the other pad module is determined.

2. 2. The pad module of claim 1, wherein the process controller is operable to obtain time-related information from the position signal using at least two positioning protocols from a set of protocols including time-of-flight, two-way ranging, time difference of arrival, and phase difference of arrival.

3. 3. The pad module of claim 2, wherein the process controller is operable to use at least two of the positioning protocols in combination to determine position information over a longer range and to use at least one of the two protocols to determine position information over a shorter range.

4. A pad module as described in any one of claims 1 to 3, further comprising a magnetic coil for transmitting power, one or more of the signal devices being positioned on the pad module at one or more known positions relative to the coil, and the process controller being operable to process the position signal to determine the position of the other pad module relative to the coil.

5. A pad module as described in any one of claims 1 to 3, further comprising a magnetic coil for transmitting power, the pad module being suitable for installation at a location, one or more of the signal devices being suitable for placement at a location remote from the pad module at one or more known positions relative to the coil, and the process controller being operable to process the position signal to determine the position of the other pad module relative to the coil.

6. 6. The pad module of claim 5, wherein the pad module is suitable for installation in a vehicle as a car pad module, and the signaling device or devices are suitable for placement at locations on the vehicle.

7. 6. The pad module of claim 5, wherein the pad module is suitable for installation in a parking space as a ground pad module, and the one or more signaling devices are suitable for placement in a location near the parking space.

8. A guided power transfer system comprising the car pad module according to claim 6 and the ground pad module according to claim 7.

9. 9. The guided power transfer system of claim 8, wherein the car pad module includes at least one signaling device and the ground pad module includes two or more signaling devices.

10. 1. An apparatus for use in guiding an electric vehicle to a position at a charging site where a magnetic coil on the vehicle is positioned relative to a supply magnetic coil so that energy can be transferred between the vehicle coil and a supply coil, the apparatus comprising: at least one signalling device is associated with either the vehicle coil or the supply coil, and at least two signalling devices are associated with the other of the vehicle coil and the supply coil, each signalling device comprising a signalling device attachable to the supply coil and the vehicle coil, capable of transmitting or receiving or transmitting and receiving signals for or from the other signalling device; a process controller coupled to the signal device, Controlling the transmission and / or reception of location signals by said signalling device; processing the received signals to obtain time related information relating to differences between transmission and reception of the signals and between the plurality of received signals; and From there, a process controller is provided which determines the distance between the signalling devices, i.e. the relative positions of the supply coil and the vehicle coil.

11. 11. The apparatus of claim 10, wherein the process controller is operable to obtain time related information from the position signal using at least two positioning protocols from a set of protocols including time of flight, two-way ranging, time difference of arrival, and phase difference of arrival.

12. 12. The apparatus of claim 11, wherein the process controller is operable to use at least two of the positioning protocols in combination to determine position information over a longer range and to use at least one of the two protocols to determine position information over a shorter range.

13. 1. A method of guiding an electric vehicle to a position at a charging location where a vehicle magnetic coil is positioned relative to a ground magnetic coil such that energy may be transferred between the vehicle coil and the ground coil, comprising: Transmitting a location signal from at least one or more signaling devices; receiving a location signal from at least one signaling device to two or more signaling devices, or from two or more signaling devices to one signaling device; - processing the received signals to obtain time-related information relating to differences between transmission and reception of signals and between a plurality of received signals; and From there, the determination of the distance between the signalling devices and thus the relative positions of the supply coil and said vehicle coil; How to do it.

14. 14. The method of claim 13, further comprising obtaining time-related information from the location signal using at least two positioning protocols from a set of protocols including time-of-flight, two-way ranging, time difference of arrival, and phase difference of arrival.

15. 15. The method of claim 14, further comprising signal processing using at least two of the positioning protocols in combination to determine longer range position information and using at least one of the two positioning protocols to determine shorter range position information.

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