Object detection apparatus for an inductive charging system

Abstract

In an inductive charging system, energy is transferred through a magnetic field. An object detection device for an inductive charging system includes: a transmitter for transmitting a signal; and a receiver having a field of view encompassing most of the magnetic field for receiving reflections of the signal within the field of view. A signal processor examines the characteristics of the received signal to identify hazardous conditions associated with the magnetic field. By converting the received signal into a frequency domain signal, hazardous conditions can be identified based on the form of the frequency domain signal. The object detection device is suitable for charging devices for electric vehicles.

Description

Technical Field

[0001] An object detection device for an inductive charging system. An inductive charging system including an object detection device. A method for detecting hazardous conditions in an object detection device. Background Technology

[0002] Wireless power transfer technology is increasingly being used to transfer power from electrical power sources to a wide range of devices, from small handheld consumer electronics requiring a few watts of power (such as mobile phones and tablets) to electric vehicles requiring several kilowatts. Besides the convenience of not needing to be plugged into a power source to power or recharge a battery, the absence of wires and cables makes desktops and parking spaces tidier, while reducing clutter, tripping hazards, and electric shock risks. Wireless power transfer can be achieved in several ways, including capacitive coupling and inductive coupling, both of which offer advantages over resistive (i.e., wired) coupling used to supply power to devices.

[0003] Wireless power delivery systems can be designed to deliver power ranging from fractions of a watt, several watts to kilowatts from a power source to a device or load across a gap. Typically, this gap is an air gap between magnetic coils, although other techniques include power delivery between the plates of a capacitor. Furthermore, wireless power delivery systems can be designed to operate at a fixed or variable frequency, which is useful for varying load conditions.

[0004] The energy delivered in this way can be used, for example, to power electronic circuits and devices; including consumer devices such as mobile phones or tables; and also to drive electric motors in electric vehicles and charge batteries in circuits or vehicles. Powering a mobile phone or charging its battery requires several watts of power, while powering a motor in an electric vehicle or charging its battery requires several kilowatts. The larger the battery circuit or motor, or the faster the battery needs to charge, the greater the power that must be transferred across the air gap.

[0005] Wireless power transfer technology has evolved across various technical fields, resulting in different terms used to describe essentially the same thing. Terms such as “magnetic coupling” / “magnetic induction”, “inductive power transfer”, “inductive charging”, and “resonant inductive power transfer” are common. While there may be minor differences, these terms are generally used broadly and interchangeably to refer to systems that transfer power from a power source across an air gap to a load via a magnetic field. In this paper, the term “inductive charging system” or ICS will be used to identify such a system.

[0006] Similarly, various terms are used to refer to different components of an inductive charging system (ICS). Essentially, an ICS includes equipment associated with a power supply unit and equipment associated with a device. The power supply equipment includes circuitry that converts energy from the power supply unit into a form suitable for driving coils. Likewise, the device equipment converts energy induced in a coil by a magnetic field into a form suitable for powering a device or charging a battery within the device.

[0007] Inductive charging systems can be used to charge batteries in electric vehicles. Drivers can park their cars above charging equipment on the ground, which magnetically couples with the charging equipment on the vehicle, thus transferring energy to the battery. Inductive charging systems for vehicles similarly have several different names, such as wireless electric vehicle charging (WEVC) systems and electric vehicle battery chargers. These names do not have any particular meaning and are merely differences in commercial choice.

[0008] In inductive charging systems (ICS) used with electric vehicles, the power supply equipment has various names, including ground pads and ground pad modules (GPMs) that can be connected to the main power supply unit. This equipment is also called a vehicle pad or car pad module (CPM) and can be installed in vehicles such as automobiles to provide energy to charge the vehicle's battery. In many cases, the naming depends on the language used by a given manufacturing company. Naturally, electric vehicle ICSs are capable of working with a wide variety of vehicles (including automobiles and heavier road vehicles such as trucks, buses, and trams) and are not limited to use with automobiles, whether they are on the road or otherwise. In this document, the terms "ground pad module" (GPM) and "car pad module" (CPM) will be used to identify the two main components of an ICS for electric vehicles.

[0009] Other terms used in different implementations of ICS include “magnetic coil,” “induction coil,” and “antenna.” These terms are also loosely and essentially interchangeably used to describe parts of an inductive charging system that transfer energy across an air gap. While these different terms should not be used, it is important to note, for accuracy, that these elements are actually coils rather than antennas. This is because at typical operating frequencies, the elements transfer energy in a near-field where only a magnetic field exists.

[0010] Antennas are designed with electromagnetic fields in mind. Once the radiated energy exceeds the near-field range and is transmitted to the far-field, an electromagnetic field is formed. The locations where the near-field ends and the far-field begins depend on the characteristics of the transmitting device (e.g., a coil or antenna). For wireless power transfer applications, precise definitions are generally not required because the size of the air gap and the frequency of system operation firmly place it in the near-field. However, the terms "magnetic coil," "induction coil," and "antenna" are similarly used interchangeably by those active in the field of wireless power transfer.

[0011] Inductive charging systems can use magnetic coils alone or in conjunction with other tuned or tunable elements. In electric vehicle power delivery applications, the ground mat module may contain coils integrated with associated drive electronics, or the ground mat module may contain coils while some or all of the associated electronics are provided in a separate housing. In either case, the coils in the ground mat module are used to transmit power via a magnetic field. Similarly, an automotive ground mat module may contain coils integrated with associated control electronics, or it may contain coils while some or all of the associated electronics are provided in a separate housing. In either case, the coils in the automotive ground mat module are used to receive power via a magnetic field.

[0012] A key area of ​​design for inductive charging systems is maintaining a safe environment. When the system is running, the magnetic field can transfer a significant amount of energy across the space between the grounding pad module and the vehicle's pad module. Even small household systems can generate magnetic fields capable of transferring 2kW to 3kW of energy between the pads. Foreign objects such as coins, paperclips, or even aluminum-capped yogurt containers will heat up in the magnetic field, posing a fire hazard. Living objects (i.e., humans and animals) exposed to such high-energy magnetic fields also risk injury.

[0013] With this in mind, efforts have been made to design inductive charging systems capable of detecting one or more objects in or entering a magnetic field. Inductive charging systems typically include an object detection device that identifies the object and shuts down the system until the object moves or is removed from the magnetic field.

[0014] WO 2016060748 appears to describe a device for liveness protection in which multiple radar modules are used to detect objects in a detection area. The radar modules are mounted on the side of a base pad facing away from the base pad to provide coverage on all sides of the base pad.

[0015] WO 2019086690 appears to describe a monitoring device for an inductive energy emitting unit. The monitoring system evaluates Doppler information and compensates for that information using stored Doppler features stored in the monitoring device. Summary of the Invention

[0016] In an inductive charging system, energy is transferred through a magnetic field. An object detection device for an inductive charging system includes: a transmitter for transmitting a signal; and a receiver having a field of view encompassing most of the magnetic field for receiving reflections of the signal within the field of view. A signal processor examines the characteristics of the received signal to identify hazardous conditions associated with the magnetic field. By converting the received signal into a frequency domain signal, hazardous conditions can be identified based on the form of the frequency domain signal. The object detection device is suitable for charging devices for electric vehicles.

[0017] As defined in the claims, the present invention provides an object detection device for an inductive charging system, an inductive charging system including the object detection device, and a method for detecting dangerous conditions in the object detection device.

[0018] The invention and its features are particularly set forth in the claims, and the invention, its features, and its advantages will become clearer to those skilled in the art from the following detailed description, which is given by way of example with reference to the accompanying drawings. Attached Figure Description

[0019] In the attached diagram:

[0020] Figure 1 This is a schematic diagram showing the components of an inductive charging system for electric vehicles;

[0021] Figure 2 This is a schematic diagram showing the components of an object detection device;

[0022] Figure 3 This is a schematic cross-section of an automotive gasket module;

[0023] Figure 4 This is a schematic cross-section of another automotive bushing module;

[0024] Figure 5 The components of the charging system are shown;

[0025] Figure 6 The diagram shows components that share a common antenna via a filter;

[0026] Figure 7 The diagram shows components that share a common antenna via a multiplexer;

[0027] Figure 8 This is a schematic diagram showing other components of the object detection device;

[0028] Figure 9 shows a graphical representation of a frequency domain signal with (a) approximate symmetry, (b) right-handedness, and (c) left-handedness;

[0029] Figure 10 The diagram shows time-domain signals and their corresponding signals in the frequency domain.

[0030] Figure 11 The frequency domain signal with amplitude and distance components is shown;

[0031] Figure 12 The frequency domain signal corresponding to the danger is shown. Detailed Implementation

[0032] like Figure 1 As shown, the inductive charging system (ICS) 10 includes a ground mat module (GPM) 12, which contains a coil 14 and a drive circuit 16 coupled to an electrical power supply unit 18. The drive circuit 16 regulates the power signals from the supply unit 18, thereby applying these power signals to the coil 14 in a suitable form. The coil 12 is driven by applying the aforementioned power signals (represented as current I and voltage V) to generate a magnetic field 20.

[0033] The power supply unit 18 can be, for example, a household voltage supply unit at 110V or 220V. Such a household installation would be limited to 2kW to 3kW, meaning that battery charging would typically take several hours. Larger power supplies (such as multiphase supplies at 415V or higher) allow for faster charging. In commercial or industrial implementations, greater power (and therefore faster charging) can be provided.

[0034] The size and form of the ground liner module 12 depend on the system's technical requirements. Coil 14 is... Figure 1 The coil 14 is depicted as a circle, but it can be any polygonal or elliptical shape. The coil 14 can be configured as a solenoid, arranged in a double-D configuration, or any other widely available coil topology. The specific form is determined by the system's technical requirements and conventional design choices. In terms of size, the ground pad module 12 is typically around 600 mm in width. The height of the GPM 12 should be as low as possible to avoid the GPM posing a hazard of snagging or tripping over the underside of the vehicle.

[0035] The inductive charging system 10 also includes a Car Mount Module (CPM) 22. In use, the CPM 22 is placed on a vehicle (not shown) at a location determined by design considerations, such as under the chassis or floor. When the vehicle travels over the GPM 12 and the CPM 22 positioned thereon, energy can be transferred from the GPM to the CPM. The magnetic field 20 is converted into a power signal (represented as current I and voltage V) by a coil 24, which is regulated by a drive circuit 26 to be in a form suitable for delivering energy to and thereby charging the battery 28.

[0036] Like the Ground Pad Module (GPM) 12, the size and form of the CPM 22 are governed by the technical requirements and design choices made when designing the inductive charging system 10. The Automotive Pad Module (CPM) 22 is similarly housed within the package. Likewise, the exact form of the coil 24, and therefore the shape and size of the CPM 22, are largely determined by technical requirements and design choices. The coil 24 need not be circular as depicted, and in fact, it need not even have the same form or topology as the coil 14 in the Ground Pad Module 12. Space in the vehicle is limited. The objective is generally to make the CPM 22 as small as possible, for example, around 300 mm in width.

[0037] One advantage of the ICS 10 is that the vehicle's battery 28 can be easily charged by parking the vehicle above the ground mat 12 with the vehicle mat module 22 and the ground mat module 12 aligned. Vehicle guidance and alignment equipment (not shown) can be provided to help the driver correctly position the vehicle relative to the ground mat module 12, and thus correctly position the vehicle mat module 22.

[0038] The inductive charging system 10 includes an object detection device 30, which is shown in the attached figure. Figure 2 As shown in the diagram. The object detection device 30 can be included in... Figure 1 The object detection device 30 is located in or beside the ICS system 10. It includes a transmitter 32 for transmitting signals via antenna 34 and an antenna 36 coupled to a receiver 38. Antennas 34 and 36 are pointed toward the volume between coils 14 and 24 of the GPM 12 and CPM 22. The receiving antenna 36 is used to receive reflections of signals from the transmitting antenna 34. Therefore, object detection uses a form of radar to detect objects in the magnetic field 20 within the volume between the vehicle cushion module (CPM) 22 and the ground cushion module (GPM) 12.

[0039] The characteristics of the emitted signal can be used as a reference. At least, a change in the signal received by receiver 38 indicates a change in operating conditions. Generally, the presence of reflection indicates the presence of an object. And a change in frequency indicates the motion of the object, i.e., the Doppler effect. Therefore, object detection device 30 can be configured to detect, for example, movement of the vehicle caused by a passenger entering or leaving the vehicle or by a cat or other animal jumping onto the vehicle.

[0040] This change can indicate an unexpected or unwanted object in the magnetic field 20. The signal from the receiver 38 is transmitted to the signal processor 40, which processes the characteristics of the received signal to determine what caused the change. The processor outputs a corresponding signal δ, in response to which the ICS 10 shuts off the magnetic field 20 (or reduces it to a safe level) until the danger has passed.

[0041] Like all antennas, antennas 34 and 36 have a radiation pattern that includes the beamwidth, which is considered the antenna's field of view. For any given antenna, both signal transmission and reception can be achieved using the radiation pattern. The object detection device 30 is placed in or near the vehicle cushion module (CPM) 22 or the ground cushion module (GPM) 12.

[0042] The exact relationship between magnetic field 20 and the antenna's field of view (i.e., beamwidth) will depend on the specific design of ICS 10. The ground and vehicle liner 12, 22 are designed such that magnetic field 20 is contained as much as possible within the space volume between GPM and CPM. The field of view of object detection antennas 34, 36 should be selected and the antennas positioned such that any object in the magnetic field will be "seen" by the antennas.

[0043] In practice, field leakage will exist outside the volume between the GPM and CPM. The field of view of antennas 34 and 36 should also include areas where the magnetic field 20 exceeds a specified safety level outside this volume. Typically, antennas 34 and 36 are placed side-by-side or configured as a single antenna shared between transmitter 32 and receiver 38.

[0044] Radar equipment is readily available as a standalone unit. Therefore, although shown as separate components, antennas 34 and 36, transmitter 32 and receiver 38, and processor 40, or various sub-combinations thereof, can be configured as a single, readily available unit. The two antennas 34 and 36 can be combined in a single antenna or a single unit. The reflected signal from antenna 34 is received by antenna 36 and receiver 38. The received signal is analyzed by signal processor 40 to detect the presence of an object in magnetic field 20.

[0045] The current idea in the design of inductive charging systems is to place the object detection device within or on ground equipment. To ensure that the object detection device can "see" objects in potentially hazardous locations, multiple sensors (e.g., radar modules) are placed around the perimeter of the base pad. See, for example, WO 2016060748 mentioned above.

[0046] In ICS 10, the object detection device 30 is preferably, but not necessarily, placed within the Car Mat Module (CPM) 22. In fact, it is generally simpler to place the radar module within or beside the CPM 22. In this location, the antenna can "look down" at the ground mat 12 during use and "see" the volume occupied by the magnetic field and the area beyond. Centering the antenna within the CPM 22 is generally the optimal approach.

[0047] Using a single unit (e.g., a radar module) is preferred, but it is not mandatory; it is simply more cost-effective. Careful selection of the signal antenna or transmit-receive antenna pair during the design phase enables a comprehensive field of view (including the space containing the magnetic field between the ground pad module and the vehicle pad module, as well as other areas outside that volume where the magnetic field may be at risk) without adding significant weight or volume to the vehicle pad module.

[0048] Turn now Figure 3 A schematic cross-section of the automotive cushion module 22, CPM 22, is shown. The CPM 22 includes a printed circuit board (PCB) 42 or other support. The coil drive circuit 26 and other electrical and electronic components associated with the operation of the cushion 22 are mounted to this support. This includes an object detection device 30 and its antennas 34, 36. The object detection device 30 is mounted in a space 44 defined by the turns 46 and 48 of the coil 24. Here, the cross and dots represent only the cross-section of the coil turns, where the current in use conceptually flows in the direction of entering (cross) or leaving (dot) the page.

[0049] The fields of view of antennas 34 and 36 are away from PCB 42 in the direction indicated by arrow 50. When the automotive cushion module (CPM) 22 is installed under the car, the direction of arrow 50 corresponds to being away from the car and towards the GPM ( Figure 3 (Not shown in the image). Placing antennas 34 and 36 within CPM 22 and selecting an antenna with a suitable radiation pattern enables the object detection device to "see," i.e., detect objects in the magnetic field 20 between GPM 12 and CPM 22.

[0050] like Figure 4 As shown, in another vehicle mat module 22, the circuitry associated with the object detection device 30 is placed above the printed circuit board (PCB 42) (i.e., placed on the vehicle side in use). Antennas 34 and 36 are on the underside of the PCB (as shown and in use), again “looking” downwards toward the ground mat (not shown) in the direction of arrow 50.

[0051] Considering Figure 3 and Figure 4Based on the preceding description, it is understandable that the placement of the detection device circuitry and antenna is a design choice driven by technical requirements.

[0052] Currently, inductive charging systems are supplied to customers as complete systems (ground charging module and vehicle charging module together). This may change as inductive charging systems mature further. Automakers may decide they only want the vehicle charging module supplied for their vehicles; the ground charging module will be supplied by a separate company. Automakers may specify that the vehicle charging module should be as lightweight and inexpensive as possible. This will drive the shift of IC components from the vehicle charging module to the ground charging module.

[0053] At least for these design-driven reasons, it may be necessary to place the object detection device 30 at or within the ground pad 12 in some inductive charging systems. In this case, antennas 34, 36 will typically be centrally positioned below the upper surface of the ground pad 12. The antennas will "look" upwards at the vehicle pad 22 through the ground pad 12. Being able to see objects on the surface of the ground pad 12 is desirable and may even be necessary. This will require a substantially omnidirectional antenna radiation pattern, at least within the hemisphere above the surface of the ground pad.

[0054] Similarly, while desirable from a weight and space perspective, it may be necessary in some systems to use more than one antenna to transmit or receive, or transmit and receive object detection signals. A given vehicle layout may contain "blind spots," which are areas or spaces beneath the vehicle that are obscured from the single location where the object detection antenna is best positioned. In such cases, a second antenna for transmission and / or reception may be a suitable solution.

[0055] The inductive charging system includes a control unit that enables data transfer between the ground liner module 12 and the vehicle liner module 22 to control the operation of the system 10. The control unit includes a wireless link that typically conforms to existing standards or combinations of standards, such as Wi-Fi or Bluetooth. Figure 3 and Figure 4 Both show a Wi-Fi unit 60 placed in space 44 and an object detection device 30. The Wi-Fi unit 60 has its own antennas 62, 63 for transmitting signals or receiving signals from similar Wi-Fi units in the ground pad (not shown).

[0056] There are several ways to mount Wi-Fi and object detection devices within the padding of an ICS. Figure 5One method is illustrated in which the object detection device 30 and the Wi-Fi unit 60 are considered as completely separate elements, each with its own antennas 36, 62. Although the object detection device 30 operates in one frequency band and the wireless control link (Wi-Fi) 60 operates in a different frequency band, it may be necessary to add bandpass filters 66, 68 to each of the object detection device 30 and the Wi-Fi 60 to avoid interference from harmonics or other sources.

[0057] In this Figure 5 The deployment requires additional antennas to establish the wireless link, which further increases the weight and cost of the ICS 10. Figure 6 and Figure 7 The layout in the document solves this problem.

[0058] like Figure 6 As shown, a single antenna 70 can be shared between the object detection device 30 and the Wi-Fi element 60. Each of the object detection (OD) device 30 and the Wi-Fi element 60 has an associated filter 66, 68 coupled to the antenna. Filter 66 allows object detection signals to be transmitted between the antenna 70 and the object detection device while blocking signals from the control equipment 60. Filter 68 allows control signals to be transmitted between the antenna 70 and the control equipment 60 while blocking object detection signals.

[0059] Alternatively, such as Figure 7 As shown, the multiplexer (M) 72 can be placed between a single antenna 70, the OD device 30, and the Wi-Fi element 60, thereby enabling switching access to the antenna 70 at different times.

[0060] Ideally, the difference between the signal transmitted from antenna 34 and the signal received by antenna 36 in the object detection device would clearly indicate the presence of an object in the magnetic field. In reality, many different situations can lead to differences in the signal due to external influences. If excessive focus is placed on safety, the resulting system will frequently enter a safety operating mode, in which the magnetic field is either shut off or reduced to a safe level. False alarms can render the ICS unreliable during battery charging for reasonably expected periods.

[0061] Clearly, the desired outcome is to be able to distinguish between the actual presence of an object in a magnetic field and a false positive. One way to do this is to preserve definitions of signal differences that correspond to, or may correspond to, known false positives.

[0062] like Figure 2As shown, in the object detection device 30, the characteristics of the transmitted signal are used as a reference fed into the signal processor 40. This enables the object detection device 30 to detect movement within its field of view, i.e., to monitor the intrusion of an object, including changes in the object's position. The transmitter 32 provides the signal processor 40 with the transmitted signal itself or digital data representing the characteristics of the transmitted signal. Similarly, the receiver 38 feeds the signal or the characteristics of the received signal to the signal processor 40. In the event of a difference in frequency and / or phase between the transmitted and received signals, the processor 40 represents any such difference as an output δ.

[0063] Figure 2 The detection device 30 includes a reference storage device 74 for storing data representing operational characteristics associated with these external events. The operational characteristics can represent waveforms associated with changes caused by external events.

[0064] The relevant parts of the detection device are also Figure 8 As shown in the diagram. Reference storage device 74 stores data representing a database of characteristics of a reference signal or waveform 76. The characteristics of each reference signal (which may be in the time domain or frequency domain) correspond to the properties of a signal received under known operating conditions.

[0065] Therefore, the reference storage device 74 can store data representing different waveforms for different events. A person entering a car might generate a relatively low-frequency, high-amplitude waveform, while a cat jumping onto a car might generate a short pulse waveform. The reference storage device 74 stores enough data to enable the processor 40 to represent multiple different external events.

[0066] When a short-term change occurs due to an external event, processor 40 compares the data representing signal 58 from receiver 38 with the data in reference storage device 74. Signals 58 and 74 may not be identical, but they will be similar. The processor compares the characteristics of the received signal 58 waveform with the characteristics of the reference waveform 76. When there is a basic equivalence between the received waveform and the reference waveform, processor 40 outputs an indication increment (δ) indicating no difference or a very small difference (e.g., δ = 0). In the case of a difference between the two waveforms, processor 40 indicates the difference by outputting a value δ ≠ 0.

[0067] It should be understood that in practice, there will naturally be some differences between the signal from the receiver and the signal represented by the data in the reference storage device 40. These differences can be attributed to different operating conditions and ambient noise. Therefore, the value of δ cannot be truly zero. However, the value will be close enough to zero that it is possible to determine that the received signal and the represented signal are substantially equal.

[0068] For the sake of brevity, this article will use the output value of δ = 0, which can be understood as meaning close enough to zero to indicate that the two signals are essentially the same. Similarly, the equation δ ≠ 0 does not mean any value that is not zero. It refers to a value of increment (δ) that is substantially greater than zero, in terms of the degree to which the characteristics of the received signal waveform are not equal to those of the reference waveform 76.

[0069] An output of δ = 0 indicates that the change may be caused by a known activity (e.g., a foreign object or living body entering the magnetic field). Therefore, this value is an indicator of an event, in other words, a true positive caused by a foreign object or living body entering the magnetic field. Thus, ICS 10 needs to shut down the magnetic field 20, for example, by cutting off or significantly reducing the voltage and current delivered to coil 14 in the ground pad 12. An output of δ ≠ 0 means that the change is not a known activity and may be a false positive. No action is required from ICS 10.

[0070] Additional measures can be taken to reduce false positives. These measures can be used individually or in combination, and in conjunction with the aforementioned monitoring of energy transfer (operation) parameters. To identify false positives, the signal can be characterized as movement or vibration / noise. Movement corresponds to an object in the field of view of the object detection device 30. When movement is detected, the magnetic field 20 should be shut off or at least reduced to a safe level.

[0071] The Fast Fourier Transform (FFT) converts a signal in the time domain into its corresponding signal in the frequency domain. The FFT of a signal produces a frequency domain signal that includes a positive frequency component (+f) and a negative frequency component (-f), where f = frequency. The positive and negative frequency components are the result of the FFT using complex numbers, which include real and imaginary parts. Typically, the negative frequency contains the same information as the positive frequency and can be ignored.

[0072] The FFT transformation of a simple sine wave produces a frequency domain signal that includes a single positive frequency component at +f and a single negative frequency component at -f. In comparison, a note played on a musical instrument is more complex because it includes the note itself and its harmonics. In addition to the frequency of the note itself, the FFT will generate several other components at the frequencies of the harmonics. The note in the frequency domain will have equal +f and -f elements on both sides of f=0.

[0073] Figure 9(a) shows a graph 90 representing the frequency domain signal of the substantially symmetrical -f element 91 and +f element 92 on both sides of the vertical line 94 when f = 0. The graph in Figure 9(a) is presented for illustrative purposes only and does not correspond to any specific signal or event. However, it is the kind of graph one would expect to see when a signal is received by the receiver 38 of the object detection device 30. This contains information about the signal from the transmitter 32 being reflected by something in the field of view of the detection device 30. Processing this signal can reveal more information about the object, such as whether it is moving or stationary.

[0074] In some systems (such as communications and radar), information is transmitted in the time domain using complex signals. The complex components of these signals are called in-phase (I) and quadrature (Q) components. They can be used separately to transmit different information. Radar transceivers capable of representing the received signal in complex form are available. The complex form can be represented using rectangular notation with real and imaginary parts, as discussed herein. Alternatively, complex signals can be represented using polar coordinate notation with amplitude and phase components.

[0075] The importance of this is that complex representations include more information about the received signal, and therefore more information about the object, which can be used to distinguish between false positives and true events. This additional information can be extracted by, for example, converting the received complex signal in the time domain into an equivalent signal in the frequency domain using FFT.

[0076] When signals represented by complex numbers are converted to the frequency domain, they produce results containing information about the position or movement of the detected object. Positive frequencies can be considered to be related to objects moving towards the detector (i.e., towards the magnetic field), while negative frequencies mean that the object is moving away from the space between the GPM and CPM (i.e., away from the magnetic field). Therefore, when the movement of an object is detected, the positive and negative frequency components on one side and the other side of the line f=0 will be different. In other words, the signal in the frequency domain will exhibit (left or right) handedness or sidedness.

[0077] The curve 90 in Figure 9(a) discussed earlier does not exhibit directional or lateral behavior. The curves on each side of the vertical line (f=0) 94 are essentially similar, if not identical. The reflected signal originates from a moving object. And if the signal is not new, this indicates that the reflection originates from something static, and is likely a false positive.

[0078] Conversely, Figures 9(b) and 9(c) show curves 96 and 98 in the frequency domain exhibiting right-handed and left-handed rotation, respectively. The terms "left" and "right" are arbitrary here, with "right" chosen because the peak of the curve in graph (b) is to the right of the vertical line 94, and "left" chosen because the peak of the curve in graph (c) is to the left of line 94.

[0079] Figures 9(b) and 9(c) illustrate one form of signal caused by, for example, an object moving toward and away from device 30 (b). Figure 9(b) could represent a signal caused by a person walking toward the car, while Figure 9(c) represents a signal caused by the person continuing to walk past the car and moving away from it. Therefore, the object could be a living person or animal, which could be exposed to the magnetic field if it gets too close to the car. This is potentially dangerous, and it is necessary to identify the signal as an event associated with a dangerous or potentially dangerous situation.

[0080] exist Figure 9(a) , 9(b) In each of the graphs in 9(c), any given point on the straight line or curve is related to the energy in the signal received by receiver 38 at a specific frequency. Therefore, the area under each curve is related to power. Thus, the area under the curve is related to energetic things (e.g., movement or noise). Object detection involves sensing moving objects (true positives) and ignoring other energy sources at antenna 36 and receiver 38 (false positives) (see [reference]). Figure 2 ).

[0081] In the frequency domain of Figure 9, shifts tend to generate curves with low heights and thus cover a smaller area, while false positives tend to generate curves with larger amplitudes that cover a larger area.

[0082] Noise is random and tends to dissipate over time. If the energy (represented by the area under the curve) is below a predetermined threshold, no detection is made. If the area under the curve is above the predetermined threshold, the detected activity is either identified as a true detection of movement or as a false positive, i.e., unrelated to the movement of a living or inanimate object in the field of view of the object detection device.

[0083] Of course, in the absence of a reflection received by the object detection unit, the receiver will output a blank signal, which will result in a corresponding blank in the frequency domain. The blank may not be zero; there may be elements of noise, i.e., a noise floor.

[0084] Briefly back Figure 2The processor 40 processes the signal to determine the area in the frequency domain, thereby distinguishing between detected events and false positives. Identification of the directional signal will cause the processor to output a signal (δ) corresponding to the hazardous situation. The ICS 10 is arranged to respond to the object detection device 30 by stopping the generation of the magnetic field or at least reducing the magnetic field to a safe level until the hazard is eliminated.

[0085] As shown in the graph in Figure 9(a), when there is a substantially equal balance between the left and right sides, the indication suggests that the signal may not be caused by an object and could be a false positive. When a false positive condition is detected, the processor 40 will output a signal indicating that there is no object hazard. Obviously, in the absence of hazard, the ICS 10 will not take any hazard-related action and will continue to generate the magnetic field 20 to transfer power and thus charge the battery 28 in the vehicle.

[0086] Processor 40 will Figure 10 The two time-domain signals 100 and 102 shown are converted into equivalent signals 104 and 106 in the frequency domain. This can be done using any of the known techniques for converting from the time domain to the frequency domain (e.g., Fast Fourier Transform (FFT)). In both cases, the frequency-domain signals have elements on both sides of zero (f = 0), as shown in Figure 9(c). This is an indication of a false positive.

[0087] This method of viewing the received signal in the frequency domain also makes it possible to detect multiple objects. This is obviously advantageous because it's possible for multiple objects to move into the receiver's field of view substantially simultaneously. Moreover, in many cases, the movement of multiple objects may be related to the movement of parts of a vehicle or the ground on which the vehicle is parked, in the form of vibrations. The ability to detect vibrations reduces the possibility of false positives, thereby increasing the reliability of the accuracy of the object detection device.

[0088] Automobiles (and other vehicles) are essentially monolithic structures. Except in limited situations such as when they vibrate, the parts of a car cannot move independently. Vibrations are caused by external stimuli, such as a heavy vehicle driving past a car that is being charged, or something hitting the main body of the car. Therefore, the detection of vibrations by the object detection device 30 is a false positive.

[0089] Movement associated with vibration can be detected because objects in motion are configured in this way to each have their own characteristic frequencies, and therefore, vibrations typically exhibit a broad spectrum. If different parts of a car are seen moving, the resulting signal is more likely to indicate activity associated with vibration than activity associated with the object entering a power-transferring magnetic field.

[0090] exist Figure 11In this context, signal 110 represents both the magnitude and distance of the movement. This signal 110 is obtained by processing the received signal using processor 40 via FFT or other known techniques to generate a frequency-domain equivalent signal. Figure 11 This is an example of the object detection device 30 detecting different parts under a vehicle, which are detected as moving at different speeds and in different directions, represented by positive and negative position values. Therefore, this combination of frequency domain signals indicates a false positive. There is no safety risk, and the WEVC system does not need to stop transferring energy through the magnetic field.

[0091] like Figure 12 As shown, another result of FFT can be the generation of spikes 116 corresponding to a single frequency or narrow band and a single distance or narrow distance range. Figure 12 This indicates a situation where an object moving at a given speed at a clearly defined distance from the vehicle's liner module can be identified, and therefore indicates a potential hazard of the object in the magnetic field. The charging system 10 should be arranged to respond by shutting off or at least reducing the magnetic field 20 to a safe level.

[0092] When an inductive charging system is activated, there is an initial phase in which operating parameters change relatively rapidly as current flows through the coil, a magnetic field is formed, and energy is delivered to the battery. After this initial transition, the inductive charging system (ICS) enters a generally stable state. This is essentially because the operating conditions change as the battery charges. In short, the more charge in the battery, the greater the voltage and current required to place additional charge into the battery.

[0093] These operational changes are gradual and occur over minutes or hours. In contrast, dangerous events (such as a person placing their foot or hand under a car and entering a magnetic field, or a coin falling onto a floor mat) occur suddenly. Vibration, on the other hand, is likely to be a false positive that does not cause problems. Vibration does not indicate a dangerous situation, and charging can begin or continue uninterrupted.

[0094] When passengers enter or exit the vehicle, there is a sudden change in the position of the vehicle liner relative to the ground liner, and therefore the ground. When these external events occur, there are sudden operational changes that may last only a few seconds. This change in the relative position between the two liners directly affects the operating characteristics of the inductive charging system. Specifically, voltage and current rise or fall, and the transfer efficiency η changes. This change in operating characteristics is measurable.

[0095] Moreover, the way the transmission efficiency η changes is repeatable. If the efficiency were represented as a line on a graph, the shape of the line would be similar whenever, for example, a person enters the vehicle or an animal jumps onto it. Comparing the detected changes with known changes in operational characteristics helps reduce false positives, i.e., events that do not correspond to dangerous situations. Therefore, the processor 40 (alone or in combination with other control circuitry (not shown) in the ICS 10) can mitigate object detection based on changes corresponding to events such as changes in the vehicle's height relative to the ground (false positives) and changes in the height relative to objects in or near the magnetic field (true positives / events).

[0096] The invention has been described by reference to an object detection device for an inductive charging system and by reference to an inductive charging system including an object detection device. It should be understood that the invention has been described by way of example only, and modifications and variations, such as those conceived by a person of appropriate knowledge and skill, may be made without departing from the spirit and scope of the invention as set forth in the appended claims and their equivalents.

Claims

1. An inductive charging system, comprising: A ground pad module having a coil and a drive circuit, the drive circuit being able to couple to an electrical power supply to generate a magnetic field; An automotive liner module, the automotive liner module comprising a coil for receiving energy from the magnetic field and a drive circuit capable of coupling to deliver power to a battery in a vehicle; as well as An object detection device, wherein the object detection device includes: Transmitter, the transmitter being used to transmit signals; A receiver having a field of view comprising a majority of the magnetic field for receiving reflections of emitted signals within the field of view; and A signal processor, configured to examine the characteristics of the received, reflected signal to identify hazardous conditions associated with the magnetic field; and The inductive charging system shown also includes a wireless data link between the ground pad module and the vehicle pad module for transmitting data related to their operation between the ground pad module and the vehicle pad module. The wireless data link includes an antenna associated with the ground pad module and an antenna associated with the vehicle pad module. The object detection device is coupled to one or the other of the antenna associated with the ground mat module or the antenna associated with the vehicle mat module; The object detection device is capable of operating at a first frequency; The wireless data link is capable of operating at different second frequencies; and The object detection device and the wireless data link are coupled to the antenna via corresponding filters associated with the first frequency and the second frequency, respectively.

2. The inductive charging system according to claim 1, wherein, The signal processor is operable to convert the received signal into an equivalent frequency domain signal and examine the frequency domain signal to identify dangerous situations.

3. The inductive charging system according to claim 2, wherein, The signal processor is operable to determine the directionality in the frequency domain signal in order to identify dangerous situations.

4. The inductive charging system according to claim 2 or 3, wherein, The signal processor is operable to determine the position and / or direction of movement of an object in the magnetic field based on the rotational property of the frequency domain signal.

5. The inductive charging system according to claim 4, further comprising a reference storage device for storing data representing the characteristics of a reference waveform, wherein, The received signal includes a waveform; and The signal processor is capable of operating to compare data representing the characteristics of the received signal waveform with the characteristics of the reference waveform, and to identify dangerous conditions based on the equivalence between the received waveform and the reference waveform.

6. The inductive charging system according to claim 5, wherein, The characteristics of the reference waveform include those of the transmitted signal.

7. The inductive charging system according to claim 5, wherein, The characteristics of the reference waveform include the corresponding frequencies and / or phases of the transmitted and received signals.

8. The inductive charging system according to claim 7, wherein, The characteristics of the reference waveform are related to the operational characteristics associated with magnetic field energy transfer.

9. The inductive charging system according to claim 8, wherein, The characteristics of the reference waveform are related to the energy transfer efficiency.

10. The inductive charging system according to claim 8, wherein, The characteristics of the reference waveform are determined by voltage and / or current signals associated with the energy transfer of the magnetic field.

11. The inductive charging system according to claim 1, wherein, The signal processor is operable to mitigate object detection by adjusting the changes in the vehicle's height relative to the ground.

12. The inductive charging system according to claim 1, wherein, The object detection device and the wireless data link are coupled to the antenna via a multiplexer, which is operable to switch access to the antenna between the object detection device and the wireless data link.

13. The inductive charging system according to any one of claims 1 to 3, wherein, The object detection device is coupled to an antenna in the vehicle liner module; and The antenna has a field of view that includes the spatial volume between the ground pad module and the vehicle pad module.

14. A method for detecting a hazardous condition in an object detection device for an inductive charging system according to any one of claims 1-13, wherein energy is transferred via a magnetic field in the inductive charging system, the method comprising: Transmit signal; Receive the reflection of the emitted signal from within the magnetic field; as well as Examine the characteristics of the received reflected signal to identify hazardous conditions associated with the magnetic field.

15. The method of claim 14, further comprising: The received signal is converted into an equivalent frequency domain signal; as well as Examine the frequency domain signal to identify dangerous situations.

16. The method of claim 15, further comprising determining the rotational nature of the frequency domain signal to identify dangerous conditions.

17. The method according to claim 15 or 16, further comprising determining the position and / or direction of movement of the object in the magnetic field based on the rotational property of the frequency domain signal.

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