Foreign object detection for wireless power transfer system

Abstract

A two-level foreign matter detection system (Figure 2) is used to detect foreign matters (1004, 1104) that affect a ground transceiver component (GTA) (406) of a wireless power transfer (WPT) station (Figure 4). In a first stage, at least one camera device (201, 202) is positioned to observe a charging location of the GTA and an area around the charging location. In a second stage, an impedance measurement circuit (Fig. 12) measures an impedance of a wireless power transfer coil of the GTA. An imaging processor (204) analyzes the image from the at least one camera device to identify a change or feature indicative of introduction of foreign matter on the exposed surface of the GTA or in an area around the charging location. A foreign object detection (FOD) controller (205) triggers an impedance check of the GTA by the impedance measurement circuit and initiates a fail-safe operation upon detecting object movement to cross-border into or beyond the charging position.

Description

Technical Field

[0001] The present disclosure relates generally to wireless power transfer, and more particularly to devices, systems, and methods related to wireless power transfer to a remote system, such as a vehicle including a battery. More particularly, the present disclosure relates to the detection and classification of foreign objects that may affect the future operation of wireless power transfer equipment. Background Art

[0002] Wireless Power Transfer (WPT) technology is based on the scientific principles of electromagnetic induction as described by Lenz's law and Faraday's 1st law of induction. Early work on developing WPT was done by inventor Nikola Tesla in the early 1890s as taught in U.S. Patent No. 645,576, entitled "System of transmission of electrical energy," issued on March 20, 1900.

[0003] Detection of potentially hazardous foreign objects introduced into the air gap of WPT systems has been achieved using monitoring of electrical measurements during power transmission (i.e., efficiency drop, power loss, current reduction, changes in resistance, inductance, and capacitance) or using non-electrical measurements and additional sensors (weight, temperature, pressure). Foreign Object Detection (FOD) has also been accomplished electro-optically (e.g., imaging with visible light, imaging with infrared light, radar) and acoustically (ultrasound imaging).

[0004] A digital camera uses a solid-state sensor (e.g., a CCD (charge-coupled device) or a CMOS (complementary metal oxide semiconductor)) to capture light collected by a lens and convert the captured light into electronic image data. A digital image contains a certain number of pixels, each of which is mapped onto a planar grid. Each pixel has its own tone value, which determines the hue or color of the image. The image resolution is determined by the number of pixels per inch (ppi) of the sensor. The format of the digital image defines the bit depth, dynamic range, file size, file format, and compression (e.g., as in Recommendation ITU-R BT.2020-2). Video (image stream at a frame rate) imaging is also defined in this way (e.g., Digital Cinema System Specification (DCSS)).

[0005] As in U.S. Patent No. 510,758, entitled "AMETHOD OF PHOTOGRAMMETRY," patented on December 12, 1893, and U.S. Patent No. 2,358,777, entitled "Method and means for oblique aerialphotographic mapping," issued on September 26, 1944, the use of images for measurement and the mathematical techniques involved have become common due to aerial photography and mapping. More recently, image recognition techniques have been used to identify objects within images. Image recognition is the ability of a machine vision system or system to identify objects, people, places, and actions in an image. A machine vision system can use artificial intelligence and trained algorithms to recognize images through a camera system.

[0006] The impedance of a complex circuit can be measured directly. A direct measurement would involve measuring the voltage (V) supplied to the circuit divided by the current (I). Changes in the impedance of the circuit can be determined by multiple measurements of the current response to a set voltage signal.

[0007] A first current response measurement at a first AC voltage will set the nominal impedance (V / I), and subsequent measurements will then be monitored for changes in the (V / I) ratio, where any perturbations to the circuit will be detectable in both the magnitude and phase of the current response. Summary of the invention

[0008] Various examples are now described to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to be used to limit the scope of the claimed subject matter.

[0009] A two-stage foreign object detection system is used to detect foreign objects that affect the ground transceiver assembly (GTA) of a wireless power transfer (WPT) station. In the first stage, at least one camera is positioned to observe a charging location (i.e., a ground transceiver station (GTS)) having at least one GTA and the area around the charging location. In the second stage, an impedance measurement circuit measures the impedance of the wireless power transmission coil of the GTA. An imaging processor analyzes images from at least one camera to identify changes or features that indicate the introduction of foreign objects on the exposed surface of the GTA or in the area around the charging location. A foreign object detection (FOD) controller triggers an impedance check of the GTA through the impedance measurement circuit and initiates a fault protection operation when an object is detected to move out of bounds into the charging location or beyond the charging location.

[0010] In an example configuration, a method for detecting a foreign object that impacts a ground transceiver assembly (GTA) of a wireless power transfer (WPT) station includes: observing an area around a charging location of the GTA using at least one camera device; and analyzing images from the at least one camera device to identify changes or features that indicate the introduction of a foreign object on an exposed surface of the GTA or in an area around the GTA. When the image indicates the presence of a foreign object on an exposed surface of the GTA or in an area around the GTA, an impedance check of the GTA is triggered. When the presence of a foreign object on a surface of the GTA is confirmed by the impedance check, a failsafe operation is initiated.

[0011] In an example configuration, when a vehicle is approaching, present, or planned to be present at a charging location, observing the area around the charging location of the GTA using at least one camera is initiated. Observing the area around the charging location of the GTA using at least one camera may include: when the WPT station is not in use, monitoring the area around the charging location for people, animals, or vehicles that may interfere with charging of the WPT station, and when at least one of the people, animals, or vehicles is detected, triggering an impedance check to be performed before the WPT station can be used. In addition, observing the area around the charging location of the GTA using at least one camera may include: when the WPT station is in use, monitoring the area around the charging location for people, animals, or vehicles that may interfere with charging of the WPT station, and when at least one of the people, animals, or vehicles is detected, initiating a failsafe operation to perform at least one of the following: reducing or removing power from the WPT station, signaling a driver or occupant of the vehicle, or setting a visual alarm or audio alarm to alert at least one person, animal, or vehicle.

[0012] In an example configuration, analyzing images from at least one camera device may include: receiving image data based on a recent image or an edited image or a representative model of at least one of the charging position or the area around the charging position, and comparing the recent image or the edited image or the representative model with an image captured while observing the charging position or the area around the charging position to identify image differences indicative of foreign matter. Analyzing images from at least one camera device may also include: detecting at least one of the edges or corners of the GTA, and aligning the image captured by the at least one camera device with at least one of the detected edges or corners of the GTA. Analyzing images from at least one camera device may also include: averaging pixels from a series of multiple subsequent images.

[0013] In other configurations, analyzing images from at least one camera device may include: waiting until an image stream from at least one camera device is received; comparing the location, number, and spacing of GTAs in images in the image stream with a reference image; averaging multiple images in the image stream to filter out image errors; performing pixel subtraction to eliminate static portions of the averaged multiple images; comparing the resulting foreground image with a previous foreground image to determine a current position relative to the GTA; and when a foreign object is found within a preset safety margin around the GTA, approaching the GTA, or scheduled to cross the GTA, performing at least one of the following: providing an alarm or suspending at least one of charging or impedance checking.

[0014] In other configurations, analyzing images from at least one camera device may include: waiting until at least one complete image corresponding to a complete image of the GTA is received; centering the at least one complete image using at least one of the detected edges or corners of the complete image of the GTA; averaging multiple images of the GTA to filter out image errors; performing pixel subtraction to compare the complete image of the GTA with a previous image of the GTA showing that the GTA is free of foreign matter; comparing the result of the pixel subtraction to a detection threshold, and when the result of the pixel subtraction exceeds the detection threshold, at least one of providing an alarm or suspending the availability of the GTA until the impedance check is completed.

[0015] In other configurations, analyzing the images from the at least one camera may include analyzing the images to identify a person or animal approaching the vehicle during charging at the charging location, and pausing charging when a person or animal is detected in the area surrounding the charging location.

[0016] In an example configuration, an impedance check on the GTA is triggered when an object is detected on an exposed surface of the GTA for more than a set duration. The impedance check on the GTA may include: powering the WPT station at a level below the charging level, measuring the impedance of the GTA at an impedance reading or model equivalent to the past, and initiating a fault protection operation when an impedance increase indicating a conductive object on or near the GTA is detected. The impedance check on the GTA may also include: sending a test AC current to the coil assembly of the WPT station in the form of a sine wave, square wave, or pulse train at a test current level that powers the coil assembly of the WPT station at 5% to 50% of the nominal wireless power applied to the coil assembly of the WPT station during charging; measuring the current through the coil assembly and the differential voltage across the coil assembly of the WPT station; and determining the impedance of the WPT station based on the measured current and differential voltage.

[0017] In other configurations, the impedance check of the GTA may include: taking at least one baseline impedance measurement of the GTA and storing the impedance value for comparison with the impedance value during the impedance check triggered when the object movement is detected to cross into or beyond the charging position. Impedance changes due to temperature changes or changing environmental conditions may also be tracked; and the baseline impedance measurement of the GTA as a function of the temperature change or the changing environmental condition stored in the lookup table may be adjusted based on at least one of the measured temperature or environmental condition.

[0018] In other configurations, adjusting the baseline impedance measurement of the GTA may include monitoring the impedance from one impedance measurement to the next impedance measurement, and when a change in impedance below a first threshold is detected, updating the baseline impedance to a new baseline impedance. On the other hand, when the impedance change is greater than the first threshold but less than a second threshold, the baseline impedance is not updated and an object detection event is not triggered. Furthermore, when the impedance change exceeds the second threshold, the baseline impedance is not updated and an object detection event is triggered.

[0019] In other configurations, an impedance check on the GTA is triggered when the charging location is unoccupied and stationary for charging. An impedance check on the GTA may also be triggered when the GTA is unoccupied and analysis of images from at least one camera device shows at least one of: a change indicating the presence of a persistent object on the GTA, an object crossing a boundary at a predetermined distance from the GTA, or a pedestrian or non-charging vehicle crossing the GTA. An impedance check on the GTA may also be triggered when the GTA is occupied by a vehicle for charging and analysis of images from at least one camera device shows a person, animal, or object breaching a preset safety boundary around the GTA. In addition, an impedance check on the GTA may be triggered when an electric vehicle is detected approaching for charging at a charging location through a WPT station, or when an electric vehicle is detected leaving a charging location.

[0020] In an example configuration, initiating a failsafe operation may include taking the GTA out of service when the charging location is not occupied by a vehicle for charging. On the other hand, when the charging location is occupied by a vehicle for charging, a failsafe operation may be initiated when a foreign object is detected moving into or beyond the charging location. When an object is detected moving toward the charging location during an impedance check or during vehicle charging, an alarm may be sounded or a failsafe operation may be initiated.

[0021] In other configurations, a failsafe operation may be initiated when an impedance check of the GTA reveals that a change in measured impedance relative to a measured baseline impedance exceeds a detection threshold range in at least one of magnitude or phase.

[0022] In an example configuration, a first camera is deployed for close-range viewing of the charging location, and a second camera is deployed for wide-area viewing of the area surrounding the charging location. Additionally, a series of cameras may be deployed, with each camera covering one or more GTAs from an elevated position. Multiple boundaries may be set for each camera to present a hierarchical prioritization of camera outputs for processing and alerting.

[0023] In an example configuration, when foreign objects are detected on an exposed surface of the GTA or in the area surrounding the charging location, a robotic cleaning device or mobile personnel may be dispatched to remove the detected foreign objects from the exposed surface of the GTA.

[0024] In addition to the method of detecting foreign objects, a system for detecting foreign objects that affect a ground transceiver assembly (GTA) of a wireless power transfer (WPT) station is described. The system includes: at least one camera device positioned to observe an area around a charging location of the GTA; an impedance measurement circuit that measures the impedance of a wireless power transfer coil of the GTA; an imaging processor that analyzes images from at least one camera device to identify changes or features that indicate the introduction of foreign objects on an exposed surface of the GTA or in an area around the GTA; and a foreign object detection (FOD) controller. When the image indicates the presence of foreign objects on an exposed surface of the GTA or in an area around the GTA, the FOD controller triggers an impedance check of the GTA through the impedance measurement circuit, and when the presence of foreign objects on the surface of the GTA is confirmed by the impedance check, the FOD controller initiates a fault protection operation.

[0025] In an example configuration, at least one camera includes: a first camera positioned for close-up viewing of the charging location; and a second camera positioned for wide-area viewing of the area surrounding the charging location. The at least one camera may include a series of cameras, each camera covering above one or more GTAs from an elevated position. Multiple boundaries may be set for each camera to present a hierarchical priority of camera outputs for processing and alarming. Detection of a foreign object by the first camera or detection of a person or animal in the area surrounding the charging location by the second camera may trigger impedance measurement by the impedance measurement circuit.

[0026] In an example configuration, the FOD controller can enable and set detection thresholds and perimeters around the GTA, schedule image processing by an image processor, and send alarms and warnings to local and remote networked entities used to control the operation of the WPT station. The networked entity may include a station controller that manages charging scheduling, power distribution, and at least one of wired or wireless communications associated with the WPT station. The system may also include a reservation system. The station controller may perform at least one of the following: disabling the GTA in response to an alarm from the FOD controller; resetting the local directional signal to the GTA; notifying the reservation system that the GTA is offline when a foreign object is confirmed to be detected on the GTA; and calling a local maintenance personnel or a remote maintenance personnel of the GTA.

[0027] In an example configuration, the FOD controller may also include a processor programmed to: collect local and remote data, settings, and software, and use the collected data to verify the communication link and apply security settings to the WPT station. The FOD controller may also query at least one camera device, imaging processor, and each GTA in the WPT station to collect data captured while observing the area around the charging location.

[0028] In other example configurations, the system also includes a robotic cleaning device that is dispatched to remove the detected foreign matter from the exposed surface of the GTA when foreign matter is detected on the exposed surface of the GTA or in the area around the charging location. The robotic cleaning device can be guided to the GTA wirelessly or using guidance wiring. The robotic cleaning device can include at least one of a fiber broom, a rotary broom, an electromagnet, an anti-Hall effect eddy current generator, a vacuum cleaner, or a suction device suitable for removing foreign matter. The robotic cleaning device may also include an electric vehicle that is charged by a WPT station. The robotic cleaning device may also communicate with the WPT station using at least one of a secure wireless local area data network or an inductive communication network.

[0029] The present invention part is provided to introduce the various aspects of the present invention theme in a simplified form, and the present invention theme is further described in the text of the specific embodiment later. The specific combination and order of the elements listed in the present invention part are not intended to provide restrictions to the elements of the claimed theme. On the contrary, it will be understood that this part provides some generalized examples in the embodiments described in the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The foregoing and other beneficial features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0031] Figure 1is a flow chart diagrammatically depicting a process for identifying and classifying foreign objects that impact a Ground Transceiver Assembly (GTA) of an unoccupied Wireless Power Transfer (WPT) station in an example configuration.

[0032] Figure 2 is a system diagram depicting the high-level functional components and interconnections of a multi-stage foreign object detection (FOD) system in an example configuration.

[0033] Figure 3 is depicted in the example configuration Figure 2 Flowchart of the operational flow of the FOD controller.

[0034] Figure 4 is a diagram showing an electric vehicle charging station using WPT in an example configuration.

[0035] Figure 5A is a diagram showing the visible arrangement of edges for a single GTA in an example configuration.

[0036] Figure 5B is a diagram showing the visible arrangement of corners for a single GTA in an example configuration.

[0037] Figure 6 is a diagram showing the observable arrangement of edges, corners, and gaps of a ground transceiver station (GTS) built with multiple GTAs in an example configuration.

[0038] Figure 7 is a diagram showing the use of a camera to observe the GTS from a certain height in an example configuration.

[0039] Figure 8 is a diagram showing the area surrounding the GTS viewed from different heights using one or more cameras in an example configuration.

[0040] Fig. 9A is a diagram showing pixel allocation using a commercial video camera to cover a wide area with multiple GTSs in an example configuration.

[0041] Fig. 9B is a diagram showing pixel allocation for close range monitoring of a single GTA using a commercial video camera in an example configuration.

[0042] Fig.10 is a diagram showing optical imaging overlay of a single GTA and a foreign object in an example configuration.

[0043] Fig.11 is a diagram showing optical imaging overlay of a GTS with multiple GTAs and foreign matter in an example configuration.

[0044] Fig.12 is a circuit diagram schematically illustrating an exemplary circuit for impedance measurement between WPT charging links in an example configuration.

[0045] Fig.13 is a flow chart illustrating a process for obtaining and analyzing impedance measurements to detect conductive foreign objects in an example configuration.

[0046] Fig.14 is a diagram of an exemplary vehicle for automatically removing foreign objects from a GTA of a WPT system in an example configuration.

[0047] Fig.15 is a flow chart that diagrammatically illustrates a process for imaging from a close-range observation system camera in an example configuration.

[0048] Fig.16 is a flow chart diagrammatically illustrating a process for imaging from a wide area observation system camera in an example configuration. DETAILED DESCRIPTION

[0049] Now refer to Figures 1 to 16 Detailed Description of the Illustrative Embodiments While this description provides detailed descriptions of possible implementations, it should be noted that these details are intended to be exemplary and in no way limit the scope of the inventive subject matter.

[0050] The term "battery" is used herein to describe a general chemical energy storage system and may be replaced, supplemented, or hybridized with other portable energy storage systems (e.g., solid-state batteries, reversible fuel cells, supercapacitors). In addition, while many of the examples used are wireless power transfer (WPT) systems for powering onboard systems and charging batteries for stationary electric vehicles (EVs), such uses are by no means the only uses contemplated.

[0051] The term “electric vehicle (EV)” as used herein includes all battery-powered electric vehicles (BEVs) as well as all hybrid EVs (HEVs) and dual-charge BEVs (DBEVs) having both plug-in charging capability and wireless charging capability.

[0052] In a wireless power transfer (WPT) system, a dedicated open-core transformer is assembled to allow magnetic induction to transfer energy between pairs of (primary and secondary) coils for the duration of a charging session. In a modular WPT system, multiple individual primary coils are paired with geometrically corresponding secondary coils for greater energy transfer. Since pairs of primary and secondary coils can support reverse energy transfer, the terms Ground Transceiver Assembly (GTA) and Vehicle Transceiver Assembly (VTA) are used. In a standard EV charging scenario (grid to vehicle), the GTA acts as the primary assembly and the VTA acts as the secondary assembly.

[0053] By manufacturing standard GTAs and standard VTAs, economies of scale can be achieved because GTAs are combined into larger ground transceiver stations (GTSs) to serve vehicle transceiver stations (VTSs) consisting of VTAs configured and installed on electric vehicles. The GTSs can be expanded according to the power requirements of EVs equipped with the VTSs.

[0054] The term optical sensor is used herein to refer to a digital electro-optical video camera. Electro-optical equipment used for digital video photography typically includes a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor) image sensor to capture images. Semiconductor-based sensors capture light via the photoelectric effect and convert the light into electrons, which are collected into electronic signals. The acquired image is then digitized for storage, transmission, and analysis. In the FOD applications described herein, color images are assumed, but black and white images can also be obtained. For applications such as edge detection and corner detection, color images can be reduced to grayscale with minimal information loss.

[0055] The impedance detection system used in this article is based on the measurement technology used in eddy current non-destructive testing (NDT). NDT relies on the concept described in Faraday's law of induction, in which a time-varying (alternating) magnetic field induces eddy currents in coupled conductive objects. Using a source coil with multiple windings as a magnetic field source increases (proportional to the number of windings) the induced eddy currents generated in the coupled conductive objects. The induced eddy currents produce an opposite electromagnetic field that cancels out the magnetic field that induced them. The magnitude of these induced currents is proportional to the magnetic permeability and electrical conductivity of the object, and their effect manifests itself as a change in the nominal impedance of the source coil, allowing the presence of one or more coupled conductive objects to be detected. Impedance inspection tests can be performed at a single frequency or at multiple frequencies to potentially identify and / or classify objects.

[0056] Figure 1

[0057] Figure 1 The present invention is a flowchart that diagrammatically depicts a process for identification and classification of foreign objects (ICFO) that impact a ground transceiver assembly (GTA) of an unoccupied wireless power transfer (WPT) station in an example configuration. The ICFO technology described herein supports both inductively coupled power transfer (ICPT) technology and capacitively coupled power transfer (CCPT) technology.

[0058] like Figure 1 As shown in , the ICFO system starts from step 100, and performs data upload and camera calibration. Since 1 to n cameras are deployed to overlook and monitor the charging position, automatic calibration is designed to save manual calibration after the camera is installed, and physical parameters (height above the ground, pitch angle) are verified after restart. Image data based on the latest image or edited image (or representative model) of the charging position and surrounding area is uploaded for use in the later stage.

[0059] One or more digital video cameras are deployed to focus on the physical charging location (visible physical footprint for the coils of an ICPT system or the panels in a CCPT system). If a single camera is deployed, it is necessary to use optical zoom and potentially movement (through the use of panning or a pan and angle motorized mount) to provide both a close up view of the charging location and a close up view of the area surrounding the charging location.

[0060] The initiation step 100 may occur at any time (e.g., at system startup, or after a triggering event has been cleared), but may only move to near area observation at step 101 when the charging location is not in use. Once initiated, the ICFO system may choose to begin observation at either or both of the charging location and the area surrounding the charging location. While the wide area observation at step 102 is preferably continuous, it may be initiated when a vehicle is approaching, present, or scheduled to be present at the charging location. The near area observation at step 101 cannot be initiated when a vehicle is present (and the GTA is obscured by the EV chassis), but once initiated may be continuous or periodic.

[0061] In a near area observation at step 101, a video camera observes the charging location focused on the upper surface of the GTA coil assembly. The charging location can be modular in nature, with a single GTA or multiple GTAs. The images from the camera are analyzed to determine if there are changes or features that indicate the introduction of foreign objects on or near the exposed surfaces of the GTAs. The presence of a persistent object (as opposed to a transient object such as a windblown leaf or trash) that remains on any GTA for more than a set duration will trigger a secondary inspection at step 103.

[0062] In wide area observation at step 102, video observation using one or more cameras monitors the area around the charging location for people, animals, or moving objects. Any approach to an unoccupied charging location on the set perimeter may trigger a secondary check at step 103. Movement into or across a charging location will also trigger a secondary check at step 103.

[0063] During a charging session, when the charging position is occupied by a vehicle and the GTA's view is obscured by the camera's view, wide area viewing at step 102 will also function. In this operation, detection of a nearby or approaching object may cause a failsafe phase at step 104 .

[0064] The check at step 103 is only initiated in the case of an unoccupied stationary charging position. Using the low energy setting, the GTA that has issued the trigger is powered on and the impedance of the power system (inductive coil or capacitive plates) is checked against past impedance readings or models. The temperature of the GTA coil assembly can be reported to improve detection sensitivity.

[0065] In the case where the wide area observation at step 102 provides assurance that there are no people, vehicles or animals within the predefined security perimeter, the inspection at step 103 may also be activated periodically. The wide area observation at step 102 may also alert when an object moves toward or crosses the security perimeter.

[0066] During the check at step 103, the impedance detector can confirm or deny the presence of hazardous (i.e., conductive) objects within the charging location and on or near the surface of the GTA. If not confirmed, operation will revert to the previous stage (near area observation at step 101 or wide area observation at step 102). If confirmed, the check at step 103 will trigger the failsafe step 104.

[0067] The failsafe step 104 includes both automatic offline of the charging location (upon confirmed detection of a conductive object residing on or near the GTA) and a reporting mechanism to alert maintenance personnel that the charging location needs to be cleared of the object before resuming charging operations.

[0068] Figure 2

[0069] Figure 2 2 is a system diagram depicting the high-level functional components and interconnections of a multi-stage foreign object detection (FOD) system in an example configuration. In this configuration, a camera system 200 includes a first video camera 201 for close-range viewing and a second video camera 202 for wide-area viewing. The video cameras of the camera system 200 are mounted to provide a low oblique viewing angle. A digital communication network 203 (DCN) (e.g., a network using TCP / IP for simplex and duplex communications) provides interconnections between system elements. For security, the DCN 203 can support end-to-end tunnel encryption.

[0070] In this example, the image processing system 204 is processed at a different computing platform, but the necessary digital memory, programming, and processor may be bundled into other system elements such as the camera system 200 or the foreign object detection (FOD) controller 205. The FOD controller 205, station controller 206, and reservation system 208 may be implemented as programming running on a general purpose processing platform running a near real-time operating system on a general purpose computer processor with digital memory.

[0071] The FOD controller 205 programs the detection thresholds, perimeters and schedules (e.g., when the switch to artificial lighting occurs) for image processing, and is the OAMPT (operation, management, maintenance, provisioning and troubleshooting) node for input uploads, upgrades and communication security keys. The FOD controller 205 is also responsible for sending alarms and alerts to local and remote networked entities such as the station controller 206, the reservation system 208 and the remote maintenance system 210.

[0072] The station controller 206 manages local charging scheduling and power distribution. The station controller 206 can also interface to a remote reservation system 208. The station controller 206 is a hub for wired and wireless communications (not shown) associated with the charging station. The station controller 206 can disable the charger in response to the FOD alarm, reset local directional signals 207 (e.g., lights, signs, and radio broadcasts), notify the reservation system 208 that a particular charging station is offline, and call a local maintenance personnel 209 (if available) or a remote maintenance personnel 210. The remote maintenance personnel 210 are expected to work on a dispatch office basis and are only called when personnel are needed to repair or clean the charging station, resulting in an extended downtime of the charging station.

[0073] The reservation system 208 is an optional remote entity. When a confirmed foreign object detection occurs for a particular charging station, the FOD controller 205 can send an out-of-service alert to the station controller 206, allowing charging scheduling and rescheduling to be managed remotely via the station controller 206 interface with the reservation system 208.

[0074] In an example configuration, an environmental sensor 211 is also provided, which may include sensors for a clock for time of day, sun angle detection, ambient light level measurement, air temperature, rain detection, snow detection, and individual GTA internal temperatures (e.g., GTA coil assembly temperature). The environmental sensor 211 may measure temperature changes or changing environmental conditions that may cause GTA impedance changes. The measured values ​​may be used to adjust the baseline impedance measurement of the GTA to reflect the impedance changes.

[0075] Figure 3

[0076] Figure 3 is depicted in the example configuration Figure 2 The FOD controller 205 is a flowchart of the operation flow of the FOD controller. Figure 2 The OAMPT (operation, administration, maintenance, provisioning and troubleshooting) center of the FOD system.

[0077] During a startup step 301, the FOD controller 205 collects local and remote data, settings and software stored in a database 302. During the startup step 301, using the uploaded data, the communication link is verified and security settings (e.g., encryption, access control) are applied.

[0078] In a provisioning step 303, a secure communications link is used to query an apparatus under the control of the FOD controller 205, including the camera 200 and the image processing data processor 204 (if separate from the FOD controller 205), and each GTA (not shown) for each GTS under management. Once provided, the FOD system operates to keep each GTA and the area surrounding each GTS under observation during a monitoring step 304. During the monitoring step 304, foreign object detection by the close-up observation camera 201 may occur, and subsequent inspections (using impedance measurements) may also occur. In addition, during the monitoring step 304, the wide-area observation camera 202 can detect intrusion events. During the monitoring step 304, periodic inspections or triggered inspections (using impedance tests) can flag foreign object detections.

[0079] If a FOD event occurs, the FOD controller 205 moves to an alarm step 305 (while continuing to monitor at step 304) and sends an alarm message to the station controller 206. The alarm step 305 will be maintained until the affected equipment (GTS, GTA) is cleared.

[0080] The station controller 206 may also command the FOD controller 205 to perform certain tasks during the monitoring step 304 at step 306. These tasks may include raising or lowering a detection threshold or triggering a check of the GTS before or after a charging session.

[0081] The FOD controller 205 may also be used to test the FOD system at step 307 during the monitoring step 304. Testing via impedance measurement is particularly useful when collecting baseline data to be included in the detection model due to the installation, addition, or reconfiguration of the wireless charging system GTS, or when environmental conditions as measured by the environmental sensor 211 require re-baselining of the optical detection threshold (e.g., due to seasonality, artificial lighting, or re-paving).

[0082] Figure 4

[0083] Figure 4 is a diagram showing an electric vehicle charging station using WPT in an example configuration. Figure 4 In the example, the WPT system is in charging action. As shown, the EV 401 is stationary above the ground charger 402. The ground charger (ground transceiver station (GTS)) 402 is shown here as protruding above the road surface 403, but other GTS 402 installations (e.g., flush with the road surface, embedded under the road surface) are also conceivable. In this example, the vehicle transceiver station (VTS) 404 is fixed to the underside of the EV 401.

[0084] The GTS 402 includes one or more coil assemblies 406 having auxiliary devices and structural members for mechanical support, cooling, eddy current shielding, and inductive communication links (collectively referred to as ground transceiver assemblies (GTA)). Similarly, the VTS 404 includes one or more vehicle transceiver assemblies (VTAs), each VTA having a coil assembly 405 and auxiliary devices and structural members for mechanical support, cooling, eddy current shielding, and inductive communication links. The GTA coil assembly 406 and the VTA vehicle coil assembly 405 are generally of the same size in the XY plane, but can be made with different numbers of turns. The coil-to-coil gap 407 in the Z plane is a function of the type of ground charger 402, the EV 401 build, and the load of the EV 401. In addition to the coil-to-coil gap 407, the orientation of the GTA to the VTA may experience center offsets and deviations from parallel coil matching in roll, pitch, and yaw. Positioning deviations can be unique for each charging link and are unknown before measurement. Each positioning deviation and coil-to-coil gap 407 affects the value of the coupling constant (k), resulting in an individualized resonant frequency for each GTA to VTA pair for each charging session. Curb 408 is a visual (and sometimes tactile) indicator of GTS positioning for the driver, driver assistance system, or autonomous driving system.

[0085] Although in Figure 4 In FIG. 4 , both the GTS 402 and the VTS 404 are shown as a single coil assembly (in FIG. Figure 4 In the example of the present invention, the GTS 402 has a single GTA and the VTS 404 has a single VTA), but multiple coil assembly pairs (wireless couplers) can be used for higher power transfer. The advantages of the modular approach to wireless power systems also come into play. By manufacturing a single GTA and a single standard VTA, economies of scale can be achieved because the GTA is combined into a larger ground transceiver station (GTS) 402 to serve the VTS 404 and one or more VTAs of the EV installation.

[0086] The modular GTS 402 and VTS 404 allow for charging stations in which flexible, dynamically allocable, dynamically configurable GTS 402 configurations can be built (e.g., 1 GTA per GTS 402, 2 side-by-side (2x1) GTAs per GTS 402, 2 in-line (1x2) GTAs per GTS 402, 3 in-line (1x3) GTAs per GTS 402, 4 GTAs per GTS 402 (2x2), 6 GTAs per GTS 402 (2x3), or any GTA configuration that supports a maximum number of vehicle VTSs 404 with a corresponding set of VTAs to be served).

[0087] In addition, the GTS 402 and the VTS 404 can be part of a bidirectional WPT system, where the primary and secondary coils are switchable, and the EV 401 provides energy to a grid (not shown). Since the GTS 402 and the paired VTS 404 can operate in a bidirectional mode, wireless energy transmission can be from the grid (via the GTS 402) to the vehicle (via the VTS 404), or in the reverse direction with power from the EV's energy storage device (e.g., a battery pack) being transmitted by the VTS 404 to the GTS 402 for powering a DC or AC load (e.g., a house or a construction site).

[0088] Figure 5A

[0089] Figure 5A is a diagram showing the visible arrangement of edges for a single GTA in an example configuration. In particular, Figure 5A Edge detection for aligning close-range images taken over time is shown. Since the close-range camera device 201 can move over time (e.g., due to mounting slippage, mounting pole dimensional compression (cold shrinkage), or due to wind gusts), a method is needed to align and realign images taken at different times or to utilize stored models. Although visible light is used in the example FOD system, near infrared light can also be used as an alternative or for supplemental image acquisition (e.g., at night under near IR lighting, so it is not visible to the human eye).

[0090] exist Figure 5A In the example, the GTS 402 consisting of a single GTA can be seen as a square shape installed on or embedded in the road surface. The GTS 402 includes a front edge 501, a rear edge 502, a right edge 503 and a left edge 504.

[0091] To aid edge detection, the road surface and the GTS 402 overlay can have different colors. Edge detection algorithms (e.g., Canny edge detection, Sobel edge detection) are well suited for edge determination. In the imaging process, mathematical checks of the length and parallelism of the detected edges can be used to verify successful edge detection before moving the captured image.

[0092] Figure 5B

[0093] Figure 5B is a diagram showing the visible arrangement of corners for a single GTA in an example configuration. In particular, Figure 5BCorner detection for alignment of close-range images taken over time is shown. The GTS 402, which in this example consists of a single GTA, can be seen as a square shape mounted on or embedded in the road surface. To assist in corner detection, the road surface and the GTS 402 overlay can have different colors. Corner detection algorithms (e.g., Harris corner detector) are well suited for corner determination.

[0094] Figure 5B The GTS 402 in the example installation of has four corners that can be detected: right front corner 506, left front corner 507, right rear corner 508 and left rear corner 509.

[0095] The geometrical check of detected corners and associated detected corners can be used to verify the successful acquisition of images of one or more components GTA of the GTS. Edge detection and corner detection can be combined at the expense of additional image processing time or capacity. In the case that an expected edge cannot be resolved resulting in a corner detection, a fallback method is also possible, which will reduce the image processing load.

[0096] In addition to calibration of the close range observation system camera 201, the wide area system may use edge detection or corner detection to locate the GTS 402 in images taken of the observation area during system setup when new cameras are installed or periodically to ensure continuous image coverage.

[0097] Figure 6

[0098] Figure 6 is a diagram showing the observable arrangement of edges, corners and gaps of a ground transceiver station (GTS) constructed with multiple GTAs in an example configuration. Figure 6 In the example, GTS 601 is a single flush mounted GTS 601 having 4 modular GTAs 602, 603, 604 and 605, each modular GTA being presented as a road level, 500 mm coloured (e.g. having a uniform blue (nominal PANATONE 300C, "Momentum Blue" coating)) quad. GTA 602, 603, 604 and 605 are placed in a 2x2 quad grid with 2 cm wide gaps 606 and 607, and the entire GTS 601 is framed by a standard contrast (light grey) cast concrete perimeter. Due to the use of local materials, the surrounding concrete and inter-GTS grouting may have had colourants added to adjust the hue and hence contrast.

[0099] like Figure 5A and Figure 5BAs shown in , a collection of edges and corners can be used for detection for alignment of images of GTA602, GTA603, GTA604 and GTA605 (and a single GTS 601). A GTS 601 having multiple modular GTAs 602, 603, GTA604 and GTA605 can present additional image features for image alignment. For example, in addition to the corners and edges of GTA602, GTA603, GTA604 and GTA605, GTS 601 also has optical features such as meridian gap 606, lateral gap 607, and central intersection 608 of meridian gap 606 and lateral gap 607. Each of gaps 606 and 607 presents 2 parallel edges separated by high contrast concrete or grout fill of known distance, while the central intersection 608 (high contrast area fill) is surrounded by 4 corners.

[0100] Figure 7

[0101] Figure 7 is a diagram showing a GTS viewed from a certain height using a camera in an example configuration. In particular, Figure 7 A close up view of the GTS 702 and nearby perimeter using a single camera is shown.

[0102] exist Figure 7 In the configuration of FIG. 704 , the road surface 701 includes a single GTS 702 surrounded by an invisible perimeter boundary 703. In some deployments, the perimeter boundary 703 will include both the GTS 702 and a contrasting color band (e.g., colored concrete) of the road surface 701 that provides a separation distance from the GTS 702 to enhance detection of nearby foreign objects. At a height 704, a video camera 705 is fixed to a mast, lamp post, or other supporting structure to overlook the charging GTS 702 and the adjacent area within the perimeter boundary 703. The camera 705 has a lens 706 and an image sensor 707. In this example, the focal length 708 between the lens 706 and the image sensor 707 is set to maximize the resolution of the single GTS 702 and the adjacent area being viewed.

[0103] The geometry of the field of view (FOV) of the camera 705 is determined by the height (height above road level) 704, the tilt angle 709, and the optical properties of the lens 706, which in this configuration includes only the adjacent area within the charge GTS 702 and the perimeter boundary 703. The field of view for a single geometric axis is depicted here using a lower bound 710 and an upper bound 711. The center of the camera target is shown by the center line 712.

[0104] Due to the short distances and angles used in the nominal close viewing system, perspective distortion can be ignored as the distance between the leading and trailing edges is too short (< 1 meter) to seriously degrade resolution. The binary approach (yes / no) of foreign object detection per GTA713 also helps as any discernible object on the GTA 702 is assumed to be a foreign object and the close viewing system does not attempt to identify it.

[0105] Figure 8

[0106] Figure 8 is a diagram showing observation of the area surrounding the GTS from different heights using one or more cameras in an example configuration.

[0107] exist Figure 8 , a wide area observation system is shown using a single overhead camera 802 configuration mounted on an exemplary lamp post 801, where the camera field of view 803 is preset to monitor the road surface around the GTS 804. In this example, an 8K camera (with a 7680×4320 pixel sensor) is used, where a 16:9 pixel ratio is used to divide the coverage area and volume into 144 quad cells, each with 230,400 pixels (480×480 pixels).

[0108] Wide area observation system detection relies on a camera (or collection of cameras) overlooking a wider area of ​​interest. The wider area of ​​interest may include one or more GTS (charging stations). The wide area observation system is based in part on existing object detection technology as available from commercial systems such as the IBM "Maximo" visual inspection system (e.g., U.S. Patent No. 6,731,799 entitled "Object segmentation with background extraction and moving boundary technique"). The wide area observation system monitors the wider area of ​​interest for people, animals, or vehicles that may interfere with the charging station when the charging station is in use and when the charging station is not in use. This explicitly includes vandalism and sabotage.

[0109] When the GTS 804 (wireless charging station) is not in use, the wide area observation system monitors the wider area for intruding people, animals or vehicles. If such an intruder approaches (within a set range) an unused charging station or crosses the charging station GTA, a check 103 ( Figure 1 ). In this way, objects such as lost cargo, trash, previously attached EV components, or other items that may have been accidentally or intentionally discarded can be detected before the charging station is used.

[0110] For unoccupied, unused charging stations, the wide-area observation system and the close-range observation system are complementary in that they can trigger the operation of the other, and both can trigger the secondary inspection system.

[0111] While the charging station is in use, i.e., when the EV is in position to be charged, the wide area observation system monitors the area surrounding the GTS 804 for intruding entities (e.g., people, animals, vehicles). If such an intruder approaches (within a preset safety margin), attempts to enter the charging vehicle, or attempts to go under the charging vehicle, the wide area observation system can signal the charge controller to reduce or remove power from the charger, signal the driver or occupant of the EV, and set a visual alarm or audio alarm to dissuade the intruding entity.

[0112] exist Figure 8 In the example of , the wide area observation system consists of a series of cameras 802, 805 and 806, each of which covers one or more GTS from an elevated position on a lamp post or mast 801, 807 and 808. The first camera 802 has a field of view 803 that observes an area 809 on a road surface 810. Within the observed area 809, an invisible boundary 811 has been set around the GTS 804. Although only one boundary 811 is set in this example, multiple boundaries can be created to present a hierarchical priority of the camera outputs for processing and alarming. The closer to the boundary, the higher the priority.

[0113] Fig. 9A

[0114] Fig. 9A is a diagram showing pixel allocation for covering a wide area with multiple GTSs using a commercial video camera in an example configuration. The wide area viewing system may include coverage over a single or multiple charging stations, where each charging station includes a GTS with 1 or more GTAs. Fig. 9A 9, using an aspect ratio of 9 to 16 provided by a single video camera (e.g., using the 4K standard, the 8K standard, or the 16K standard), the region of interest is defined by an X-axis 901 and a Y-axis 902, with three charging stations 903, 904, and 905, each with an associated GTS 906, GTS 907, and GTS 908 within the region of interest. In the example configuration, the camera of the wide area viewing system views the region of interest from the direction indicated by arrow 909. Although 4K, 8K, and 16K video standard cameras are used in these examples, other digital video camera standards with different pixel maps, frame rates, and aspect ratios are also contemplated.

[0115] Fig. 9B

[0116] Fig. 9B is a diagram showing pixel allocation for close range monitoring of a single GTA using commercial video camera equipment in an example configuration. The close range observation system may include an overlay over a single or multiple charging stations, preferably focusing on a single charging station to obtain maximum resolution of objects resting on a 1-to-n ground transceiver assembly (GTA).

[0117] Fig. 9B A single fixed camera field of view of a charging station is shown in . The camera coverage area is defined by an X-axis 912 and a Y-axis 913. In this example configuration, a single GTA 910 includes a GTS 906, GTS 907, or GTS 908 being observed. Fig. 9B The camera coverage area in is covered by a 16:9 grid cell. Only the pixels of those cells 911 that include the coverage target GTS 906, GTS 907 or GTS 908 need to be scanned for foreign objects, thereby reducing the processing load. In this exemplary figure, an aspect ratio of 16:9 is selected to illustrate the pixel allocation across the target area. In the example configuration, the camera observes the camera coverage area from the direction indicated by arrow 914.

[0118] exist Fig. 9B In the system, using the 8K camera device standard, GTS 906, GTS 907 or GTS 908 (composed of a single GTA) is covered by 49 units, each consisting of 230,400 pixels. Using the 500 square millimeter GTA910, this means that each pixel observes 1.05 square millimeters.

[0119] Fig.10

[0120] Fig.10 is a diagram showing a single GTA and optical imaging overlay of a foreign object in an example configuration. The GTS 1001 is shown with no vehicles present, and an imaging detection grid 1002 is overlaid over the area of ​​interest for the close range imaging system shown by the perimeter 1003 around the GTS 1001. The close range imaging system has detected a foreign object 1004 in the surface of the GTS 1001. If only the close range imaging system is used for foreign object detection, then the GTS 1001 and the charging station can be disabled before the next charging session begins.

[0121] Optical systems rely on a very small number of pixels (down to a single pixel) for foreign object detection. At this granularity, noise can affect the optical system, resulting in false positive detections. There are two types of video noise: shot noise and digital noise. While shot noise is caused by random photons in the captured scene (background photon flux), digital noise is caused by the camera sensor and imaging (photon noise, dark noise, read noise). Although they come from different sources, shot noise and digital noise are almost indistinguishable.

[0122] Using an average of pixels from a series of images reduces the effects of such noise. Using multiple pixel clusters (e.g., 3×3) while reducing resolution can also reduce the effects of such random single pixel noise. Since resolution is important, since the GTA coils are not powered during close-up viewing (and therefore no direct possibility of thermal damage), and since the goal of the close-up viewing system is continuous foreign object detection, multiple subsequent images are used that will be averaged to reduce the effects of noise. At 120 frames per second, a subset of images (e.g., the first 30 frames) can be accumulated and averaged, with unused frames discarded to reduce processing load.

[0123] An inspection 103 of the GTS 1001 that has been identified as having foreign matter 1004 is then performed using an impedance test ( Figure 1 ), where a wide-area viewing system implements electromagnetic exposure safety to eliminate false positive results from optical systems.

[0124] Fig.11

[0125] Fig.11 is a diagram showing optical imaging coverage of a GTS with multiple GTAs and foreign objects in an example configuration. In this example of a GTS with multiple GTAs, a bipolar plate (GTS with two GTAs) wireless charging station is shown with no vehicle present. The observation area 1101 of the close range imaging system covers both the first GTA 1102 and the second GTA 1103. A foreign object 1104 has been detected on the surface of the second GTA 1103 using the close range imaging system (the object 1104 covers multiple grid cells). If the close range imaging system is used only for foreign object detection, the second GTA 1103 can be disabled before the next charging session begins.

[0126] By examining the detection of false positive alarms from the imaging system, it may be confirmed that object 1104 is a conductive material with the potential for eddy current heating, thereby potentially causing thermal damage.

[0127] Fig.12

[0128] A good way to confirm detection of metallic or conductive foreign objects in a WPT system is to perform detection of the object (or objects) prior to coupling to the vehicle, which can be done at low power levels and re-use elements of the existing system for its detection. It is therefore attractive to use the existing main power coils in the ground transceiver assembly (GTA) as sensing elements. This would make the system a "single-sided" metal FOD system. In deployments where the GTS consists of multiple GTAs, each coil in the GTA can be used for FOD detection (or confirmation when initial detection is performed by the optical system). Pre-identification of an object on the GTA will trigger an inspection of that particular GTA, limiting power usage and downtime.

[0129] Placing a foreign object sensing element in the GTA enables the FOD system to operate in the absence of a vehicle. This means that foreign metal objects can be detected before any vehicle approaches, and therefore, the GTS can be rendered inoperable before any coupling and engagement of high power transfer fields. Knowing about the FOD issue before the next electric vehicle approaches also allows the next EV to be diverted to a compatible functional charging station (see U.S. Patent Application No. 17 / 646,844 entitled "METHOD AND APPARATUS FOR THE SELECTIVE GUIDANCE OF VEHICLES TO AWIRELESS CHARGER"). Checking for conductive foreign objects immediately after departure will also enable charging station operators to alert customers of poorly maintained vehicles or improper cargo handling.

[0130] Since a GTS can charge many electric vehicles, there are economic advantages to deploying the FOD system on the ground side. In addition, gravity is suitable for foreign object detection using a GTS because foreign objects will generally rest on the flat ground surface provided by the GTA. This not only ensures operational safety, but also saves the time spent when the electric vehicle approaches, aligns and engages the WPT charger, which is only disabled when the vehicle-based FOD system then detects a conductive foreign object. In addition, from the perspective of the driver (or passenger in an autonomous electric vehicle), FOD detection is preferably completed automatically before the vehicle charging session is initiated so as not to increase the total time associated with the charging session.

[0131] The single-sided FOD detection system described herein can wake up periodically at some given time interval to "scan" the charging coil for any metal objects. Because the purpose is not to transfer power, the power levels required for FOD are significantly lower (e.g., 1 to 5 amps compared to the 50 to 125 amps currently used for high-power charging). Therefore, scans can be performed at any time without worrying about generating any potentially harmful electromagnetic radiation. Use of a wide area imaging system will ensure that the nearby area is clear before the coil is energized. The wide area observation system will also trigger an immediate power down of the GTA if a person, animal, or vehicle is in proximity to the GTS being inspected.

[0132] In one operational scenario, if the presence of a conductive object is confirmed, an event can be raised to notify site management to clean the debris from the pad. The pad will then be disabled until the object is no longer detected (or the system is overridden by site management).

[0133] Fig.12 is a circuit diagram schematically illustrating an exemplary circuit for impedance measurement between WPT charging links in an example configuration. The circuit reuses parts of the GTA. Operating only in low power mode, the dedicated detection circuit system will be isolated from the charging system during GTA high power charging operation. The detection circuit components can also be shielded from the magnetic flux generated during high power wireless power transmission.

[0134] like Fig.12 As shown in , power supply 1201 is used to send alternating current (AC) to wireless power transmission coil assembly 1202. Assembly 1202 includes induction coil 1203, resonant capacitors 1204 and 1205, and magnetic redirection plate 1206 (nominal ferrite or other high magnetic permeability material). Since the impedance measurement operation occurs when the wireless power transmission coil assembly 1202 is not used for wireless power transmission, the AC power supply 1201 can generate a test current in the form of a sine wave, square wave, or pulse train as needed or desired. The test current level can also vary around a maximum of 10% of the nominal power transmission current (for example, below 10 amps for a 100 amp WPT system).

[0135] The current sensor 1207 is used to measure the current through the wireless power transmission circuit. As shown in U.S. Patent Application Publication No. 2021 / 0293855, entitled “CURRENT SENSING IN AWIRELESS POWER TRANSFER SYSTEM” published on September 23, 2021, the current sensor 1207 can be implemented as a shunt resistor 1208 with a differential voltage sensor 1209, the output of which is digitized by an analog-to-digital (A / D) circuit 1210. As an alternative to the shunt resistor-based current sensor 1207 example shown, the current sensor implementation can be based on indirect means using a Hall effect sensor, a Rogowski coil, or a current transformer (CT), as long as sufficient shielding of the inductive transmission coil 1203 can be achieved.

[0136] A second voltage sensor 1211 can be used to determine a differential voltage across the induction coil 1203 only, which is digitized by an A / D circuit 1212. A FOD controller 1214 can use a common clock digital signal 1213 from the A / D circuits 1210 and 1212 to determine impedance. Differential voltage sensors 1209 and 1211 are also used to amplify the acquired voltage signal. The FOD controller 1214 is also set to the voltage and current delivered by the power supply 1201 during impedance measurement using a digital data link 1215.

[0137] In the example configuration, Fig.12 The system described in 12 detects a conductive foreign object 1216 before the WPT session begins.

[0138] Fig.13

[0139] Fig.13 1300 is a flow chart illustrating a process for acquiring and analyzing impedance measurements to detect conductive foreign objects in an example configuration. As shown, first, initialization 1301 occurs at some time when a baseline impedance measurement is taken. Since there is no guarantee that this initial measurement will be taken without a metal object on the pad, there will be a nominal coil impedance measured at the factory that is stored in the processor or associated memory (e.g., EEPROM) for the system to use as a starting reference. At installation, when the wireless charging point is first installed, a first test measurement can be made under nominal conditions, and the resulting reference impedance and GTA coil temperature stored in a database 1304 at that time. A series of pre-installation impedance measurements made at different GTA operating temperatures will provide a reference model for the nominal impedance at different temperatures, improving the overall detection sensitivity compared to a single reference impedance.

[0140] Those skilled in the art will appreciate that the nominal impedance of the sensing coil will be affected by the ambient temperature. Therefore, an impedance tracking algorithm is included to characterize the impedance versus temperature (temperature is the temperature inside the GTA affected by solar heating, ambient air temperature, and heat not yet dissipated from the last wireless charging session). The impedance tracking algorithm monitors the change in impedance from one impedance measurement to the next. If an impedance change is detected, but the impedance change is below a certain threshold, then Z nom =Z 新 If the impedance change is greater than this threshold but less than the second threshold, the nominal impedance is not updated and no object detection event is raised. In this case, Z nom =Z nom , and no object is detected (e.g., ObjFlag=0). However, if the impedance change exceeds the second threshold, an object is indeed detected. The nominal impedance is not modified, and an object detection event is triggered. In this case, Z nom =Z nom (it is not updated) and an object is detected (e.g., ObjFlag=1).

[0141] To manage the nominal impedance changes due to significant changes in ambient temperature (as opposed to metallic objects), Z nom can be characterized as a function of temperature. nom can be stored in a lookup table, given the ambient temperature at the time of measurement (determined by the temperature sensor 211 in the GTA), the measured impedance can then be compared to the lookup table. Then, as previously described, Z can be determined nom Whether it has been updated or whether an object has been detected.

[0142] During setup 1302, a baseline impedance of the GTA to be inspected is loaded into the FOD system. Any condition or other near real-time sensor readings (e.g., coil temperature, air temperature) 1303 are recorded and may be used to adjust the baseline or restore a cached baseline from a database 1304. Threshold detection levels may also be uploaded or calculated based on or in response to discovered environmental conditions.

[0143] Once the baseline impedance of each GTA to be examined is determined, an impedance measurement can be performed 1305. Fig.12Such measurements using the circuit shown in or an equivalent circuit require that the wireless power transfer coil (e.g., primary coil) be powered to a small fraction (e.g., 5% to 50%) of the nominal wireless power. This lower power level reduces energy usage, minimizes stress on the GTA electronics, and prevents thermal damage from conductive foreign objects while also providing detection sensitivity. It should be noted that the nominal power applied during impedance measurements can be dynamic based on the observed size of the object resting on the GTA surface as detected by the close range imaging system.

[0144] Inspection of the GTA pad (or pads) is typically under the control of the FOD controller 1214. Measurement 1305 can be activated in four ways.

[0145] First, the close observation system ( Figure 7 ) would be one of the activation sources. In one example, the activation trigger would be the detection of an unoccupied pad under observation of a close-up camera that shows a change in the image indicating the presence of a persistent object on one or more of the GTA pads comprising the GTS.

[0146] Second, the wide-area observation system ( Figure 8 ) will be another activation source. For unoccupied charging spots where a GTS with one or more GTAs is installed, a proximity alert can be set as a triggering event. Proximity can be set as a threshold range from the GTS, exceeding which will trigger a check. The check can be postponed until the safe area around the GTS is clear of pedestrians or large obstructions (e.g., carts, bicycles, skateboards, etc.).

[0147] Third, for unoccupied charging spots, a crossing alert can be set as a trigger event. In this trigger event, a pedestrian or non-charging vehicle crosses the GTS, which triggers a check for foreign objects. The actual measurement 1305 can be postponed until the safe area around the GTS is clear of pedestrians or large obstructions.

[0148] Fourth, for occupied charging spots, in the presence of a charging electric vehicle, the wide area system can trigger a future (when the charging spot is unoccupied and the safe area is confirmed clear) inspection in response to a proximity event (using a set threshold range from the GTS and observing a boundary crossing).

[0149] The wide area observation system may also be used to detect people, animals or moving objects during the survey 1305. If the preset safety limits around the GTS are breached, the survey 1305 phase will be aborted and rescheduled to be performed later once the specified area has been cleared.

[0150] The analysis 1306 of the measured impedance is compared to a baseline, where there is one baseline for each GTA examined. For each measurement, the newly measured impedance measurement will be stored in the database 1304.

[0151] A change in the measured impedance relative to the baseline impedance that exceeds the detection threshold range will result in a report 1307 to the FOD controller 1214. This change can be in amplitude, phase, or both. After the impact alert 1307, a measurement 1305 of each GTA of the GTS should be completed before reactivation of the GTS charging point. Measurement 1305 can be triggered for other reasons (for immediate action or pre-scheduled action). Other reasons include events triggered by an EV approaching the GTS or an EV leaving the GTS. The measurement 1305 taken immediately before the EV arrives will not only provide confirmation of the lack of FOD, but also provide an updated record of the GTA impedance of the pre-charging link. The measurement 1305 taken immediately after the charging link and the EV leaves allows detection of dropped FOD from a known source. The EV driver or owner can then be notified of dropped cargo or debris.

[0152] The wide area observation system may trigger periodic measurements 1305 at a predetermined time to ensure that the vicinity is clear and issue warnings when approaching the vicinity.

[0153] Fig.14

[0154] Charging stations for wireless power transfer systems are designed to be unmanned with little or no local personnel as attendants or technicians. Therefore, there is a need for an automated system for removing detected foreign objects from the surface of the GTA to limit the need to dispatch remote or mobile personnel to clean the GTA. Robotic sweeper systems currently exist (e.g., see U.S. Patent No. 11,278,173, entitled "Autonomous floor-cleaning robot", issued on March 22, 2022 for carpet and floor cleaning).

[0155] Fig.14 is a diagram of an exemplary vehicle for automatically removing foreign objects from a GTA of a WPT system in an example configuration. Fig.14The cleaning robot vehicle 1401 shown in the figure uses wheels 1402 for movement, but it is expected that a tracked vehicle will be used in snowy environments. Because the robotic vehicle 1401 may be mixed with pedestrians and electric vehicles, visual indicators (flags 1403 and flashing lights 1404 mounted on vertical masts) are provided to increase the detectable presence of the cleaning robot 1401. The cleaning robot 1401 can be guided to the GTA that needs service using a wide area optical viewing system or in combination with guidance wiring as described in the following patents: U.S. Patent No. 10,040,360, entitled "Method and apparatus for the alignment of vehicles prior to wireless charging including a transmission line that leaks a signal for alignment," issued on August 7, 2018; U.S. Patent No. 10,814,729, entitled "Method and apparatus for the alignment of a vehicle and charging coil priorto wireless charging," issued on October 27, 2020; and U.S. Patent No. 11,241,970, entitled "Method and apparatus for the alignment of vehicles prior to wireless charging," issued on February 8, 2022. The guidance wiring leads to the GTA and can be selectively activated to assist the cleaning robot in navigating to the correct GTA.

[0156] When the wide area viewing system is offline, optional on-board sensors (optical, ultrasonic) 1405 can be used for obstacle avoidance.

[0157] The cleaning device 1406 can be a fiber broom, a rotating broom, an electromagnet, an anti-Hall effect eddy current generator, or a combination thereof. Another option is to use a vacuum cleaner or suction equipment in conjunction with other cleaning devices.

[0158] The cleaning robot 1401 can be an electric vehicle that uses WPT for charging. Using VTS charging allows not only charging from a WPT GTS charging station, but also charging from a dedicated GTS in the robot's weatherproof housing (not shown).

[0159] Communication with the cleaning robot 1401 can use a secure wireless local area data network (e.g., IEEE 802.11) or use inductive communication provided by an inductive communication system equipped with a vehicle transceiver station (VTS) 1407 mounted to the underside of the chassis of the cleaning robot 1401. The VTS and inductive communication system that can be used are described in U.S. Patent No. 11,121,740, entitled "Near field, full duplex datalink for resonant induction wireless charging" issued on September 14, 2021.

[0160] Fig.15

[0161] Fig.15 is a flow chart that diagrammatically illustrates a process for imaging from a close-range observation system camera in an example configuration.

[0162] The close range observation system implements a process that includes: waiting at step 1501 until at least one complete image (corresponding to a complete image of the target GTA) has arrived. Operation of the close range camera system can be continuous, periodic / pre-scheduled, or triggered by an external source (e.g., if an EV arrives for charging, the FOD controller 1214 can activate the close range observation system). Image processing can be performed using the processor and memory of the FOD controller 1214, or it can be performed on currently available dedicated image processing hardware such as a graphics processing unit (GPU) or a field programmable gate array (FPGA).

[0163] At step 1503, the incoming digital image 1502 may be centered. The centering at step 1503 uses an algorithm to detect the edges and / or corners of the imaged GTA to detect off-center cameras or distorted images. Off-center or distorted images may be correctable, discarded, or an alarm may be issued to the FOD system operator. Information from database 1504 may be used in the centering step 1503 to compare the incoming image with a previously known good image (i.e., no foreign matter).

[0164] The close range image processing process can also rely on averaging multiple images of the same GTA using an averaging step 1505 to filter out image errors such as speckle. The multiple images are averaged on a pixel (or pixel block) basis. Since areas outside the GTA are not relevant to close range operations, such areas will be filtered out before processing, thereby reducing the processing load. The information in the database 1504 can be used to determine the region of interest based on the previously identified pixels of interest.

[0165] Pixel subtraction at step 1506 may be used to compare the image, now composed of two or more combined images, to a previous image (also composed of several averaged images) showing the observed area without foreign matter.

[0166] In the analysis step 1507, the subtracted image pixel map is compared to the detection threshold. Other data (time of day, artificial lighting characteristics, ambient light sensing) can be used to set the detection threshold and select the previous image to retain. For the subtraction step 1506, using the previous foreign body-free image is preferred, where a false positive detection activates the secondary check 103 ( Figure 1 ). This use of the last retained image and fallback to secondary inspection simplifies image processing issues caused by rain and / or snow conditions obscuring the GTA surface from the camera. A successful secondary inspection also clears the current image for use in subsequent close range imaging foreign object detection.

[0167] If the analysis step 1507 of the subtracted image pixel map detects that a change in the image exceeds a threshold, an alarm can be issued at step 1508 and the FOD controller 1214 can suspend charging availability until a secondary check is completed.

[0168] Fig.16

[0169] Fig.16 is a flow chart diagrammatically illustrating a process for imaging from a wide area observation system camera in an example configuration.

[0170] At step 1601, Fig.16 The line-domain image processing process waits until the image stream from the wide-area viewing system becomes available. Incoming images are collected 1602 for subsequent processing.

[0171] To ensure that imaging is of the intended area, landmarking is used at step 1603, which nominally involves comparing the location, number and spacing of the GTAs, including the GTS, observed in the image with a reference image. The data may be obtained from calibration or previously retained images from a database 1604. Line, angle or color subtraction may be used to align straight GTA surfaces or find contrasting features of the GTA cover to the surrounding concrete, allowing the image to be overlaid.

[0172] At step 1605, random noise errors are removed using averaging of the incoming images.

[0173] At step 1606, background subtraction uses pixel subtraction to eliminate all static portions of the averaged incoming image. A reference background image is extracted from database 1604. The resulting foreground image can be stored in database 1604 for future use in analysis step 1607.

[0174] At step 1607, analysis of the resulting foreground image includes comparison with previous foreground images to determine the current position in the wide-area field of view, the direction and rate of travel of the object within the wide-area inspection area. Other data (boundaries or perimeters, time of day, artificial lighting characteristics, ambient light sensing) may be used to determine the location of the object or its shadow relative to the observed GTS.

[0175] If an object is found to be too close to the GTA, approaching the GTA, or planning to cross the GTA, an alert can be sent to the FOD controller 1214 at step 1608 to suspend charging and secondary inspection.

[0176] Additional image analysis can also be triggered for advanced recognition of images and actions, such as human identification and advanced recognition of actions such as kneeling next to the vehicle while charging, crawling under the vehicle while charging, throwing or dropping objects, etc. Image analysis can also be used to identify animals (dogs, cats, etc.) approaching the vehicle during charging so that charging can be paused until the area is cleared.

[0177] In another configuration, when a vehicle is not present and the GTA is inactive, the GTA power applied during impedance measurements is maintained below a threshold (the threshold varies based on individual coil assembly size, ferrite placement, number of windings) to prevent the generation of excessive magnetic flux above a specified amount. At the surface of the GTA, the magnetic flux should be maintained below international regulations (e.g., International Commission on Non-Ionizing Radiation Protection (ICNIRP) 2010)) or maintained below 27μT. Then, after the charging session has been completed, the GTA can be checked (using single or multiple impedance measurements) at a scheduled or set time without the need for observation by a camera system, albeit at a lower detection threshold. Using this technique, impedance checks can detect foreign objects residing on the surface of the GTA, and can be used to establish or re-establish an impedance baseline for the GTA at various coil temperatures.

[0178] in conclusion

[0179] Although various implementations have been described above, it should be understood that they are presented by way of example only and not limitation. For example, any element associated with the systems and methods described above may employ any desired functionality set forth above. Therefore, the breadth and scope of the preferred implementations should not be limited by any of the above example implementations.

[0180] As discussed herein, logic, commands, or instructions implementing various aspects of the methods described herein may be provided in a computing system including any number of form factors for computing systems such as desktop or notebook personal computers, mobile devices such as tablet computers, netbooks and smart phones, client terminals, and server-hosted machine instances. Another embodiment discussed herein includes incorporating the technology into other forms, including into other forms of programmed logic, hardware configurations, or dedicated components or modules, including devices having corresponding means for performing the functions of such technology. The corresponding algorithms for implementing the functions of such technology may include some or all of the sequences of electronic operations described herein, or other aspects depicted in the accompanying drawings and detailed description below. Such systems and computer-readable media including instructions for implementing the methods described herein also constitute example embodiments.

[0181] In one embodiment, the present invention refers to Figures 1 to 16 The functions described can be implemented with software. Software may include computer executable instructions stored on a local or networked computer-readable medium or computer-readable storage device (e.g., one or more non-transitory memories or other types of hardware-based storage devices). In addition, such functions correspond to modules, and modules may be software, hardware, firmware, or any combination thereof. Multiple functions may be performed in one or more modules as needed, and the described embodiments are only examples. Software may be executed on a digital signal processor, an ASIC, a microprocessor, or other types of processors operating on a computer system such as a personal computer, a server, or other computer system, thereby turning such a computer system into a specially programmed machine.

[0182] As described herein, examples may include a processor, logic or multiple components, modules or mechanisms (hereinafter "modules"), or examples may operate on a processor, logic or multiple components, modules or mechanisms. A module is a tangible entity (e.g., hardware) that can perform a specified operation and may be configured or arranged in some manner. In an example, a circuit may be arranged as a module in a specified manner (e.g., internally or relative to an external entity such as other circuits). In an example, all or part of one or more computer systems (e.g., stand-alone, client or server computer systems) or one or more hardware processors may be configured by firmware or software (e.g., instructions, application parts or applications) to operate as a module that performs a specified operation. In an example, the software may reside on a machine-readable medium. The software causes the hardware to perform a specified operation when executed by the underlying hardware of the module.

[0183] Thus, the term "module" should be understood to include tangible hardware and / or software entities, i.e., entities that are physically constructed, specifically configured (e.g., hardwired), or temporarily (e.g., temporarily) configured (e.g., programmed) to operate in a specified manner or to perform part or all of any operations described herein. Considering an example in which a module is temporarily configured, each of the modules need not be instantiated at any time. For example, where a module includes a general-purpose hardware processor configured using software, the general-purpose hardware processor can be configured as various different modules at different times. Thus, software can configure a hardware processor to, for example, constitute a particular module at one instance of time, and to constitute different modules at different instances of time.

[0184] It will be appreciated by those skilled in the art that while the disclosure contained herein is about providing power to a vehicle, it should be understood that this is only one of many possible applications, and other implementations including non-vehicle applications are possible. Therefore, all such applications are included within the scope of the appended claims.

Claims

1. A method for detecting a foreign object that impacts a ground transceiver assembly (GTA) of a wireless power transfer (WPT) station, comprising: observing an area surrounding a charging location of the GTA using at least one camera device; analyzing images from the at least one camera device to identify changes or features indicative of the introduction of foreign matter on an exposed surface of the GTA or in an area surrounding the GTA; triggering an impedance check of the GTA when the image indicates the presence of foreign matter on an exposed surface of the GTA or in an area surrounding the GTA; as well as When the presence of foreign matter on the surface of the GTA is confirmed by the impedance check, a failsafe operation is initiated.

2. The method according to claim 1, wherein: Using the at least one camera device to observe the area around the charging location of the GTA includes: when the WPT station is not in use, monitoring the area around the charging location for people, animals or vehicles that may interfere with charging of the WPT station, and when at least one of the people, animals or vehicles is detected, triggering an impedance check to be performed before the WPT station can be used.

3. The method according to claim 1, wherein: Analyzing images from the at least one camera device includes: receiving image data based on at least one of a recent image or an edited image or a representative model of the charging position or the area around the charging position, and comparing the recent image or the edited image or the representative model with an image captured while observing the charging position or the area around the charging position to identify image differences indicating foreign matter.

4. The method according to claim 1, wherein: Analyzing images from the at least one camera device includes: waiting until at least one complete image corresponding to a complete image of the GTA is received; centering the at least one complete image using at least one of the detected edges or corners of the complete image of the GTA; averaging multiple images of the GTA to filter out image errors; performing pixel subtraction to compare the complete image of the GTA with a previous image of the GTA showing that the GTA is free of foreign matter; comparing the result of the pixel subtraction to a detection threshold; and when the result of the pixel subtraction exceeds the detection threshold, at least one of providing an alarm or suspending the availability of the GTA until the impedance check is completed.

5. The method according to claim 1, wherein: Analyzing images from the at least one camera includes analyzing images from the at least one camera to identify a person or animal approaching the vehicle during charging at the charging location, and pausing charging when a person or animal is detected in the area around the charging location.

6. The method according to claim 1, wherein: When an object is detected on the exposed surface of the GTA for more than a set duration, an impedance check of the GTA is triggered.

7. The method according to claim 1, wherein: The impedance check of the GTA includes powering up the WPT station at a level below a charge level to measure the impedance of the GTA relative to past impedance readings or models, and initiating a fault protection operation upon detecting an impedance increase indicative of a conductive object on or near the GTA.

8. The method according to claim 1, wherein: The impedance check of the GTA includes: sending a test AC current to the coil assembly of the WPT station in the form of a sine wave, a square wave, or a pulse train at a test current level, wherein the test current level powers the coil assembly of the WPT station at 5% to 50% of the nominal wireless power applied to the coil assembly of the WPT station during charging; measuring the current through the coil assembly and the differential voltage across the coil assembly of the WPT station; and determining the impedance of the WPT station based on the measured current and differential voltage.

9. The method according to claim 1, wherein: The impedance check of the GTA also includes taking at least one baseline impedance measurement of the GTA and storing the impedance value for comparison with the impedance value during an impedance check triggered when an object movement is detected to cross into or beyond the charging location.

10. The method according to claim 9, further comprising: Track impedance changes due to temperature changes or changing environmental conditions; updating a baseline impedance measurement of the GTA in a lookup table according to the temperature change or the changing environmental condition; and adjusting the impedance measurement of the GTA based on at least one of the measured temperature or environmental condition to reflect the baseline impedance measurement stored in the lookup table.

11. The method according to claim 1, wherein: An impedance check of the GTA is triggered when the GTA is unoccupied and analysis of images from the at least one camera device shows at least one of: a change indicating the presence of a persistent object on the GTA, an object crossing a boundary at a predetermined distance from the GTA, or a pedestrian or non-charging vehicle crossing the GTA.

12. The method according to claim 1, wherein: Upon detecting an electric vehicle approaching to be charged by the WPT station at the charging location, or upon detecting an electric vehicle leaving the charging location, an impedance check of the GTA is triggered.

13. The method according to claim 1, wherein: Initiating the failsafe operation includes taking the GTA out of service when the charging location is not occupied by a vehicle for charging.

14. The method according to claim 1, further comprising: At least one of sounding an alarm or initiating the failsafe operation is performed when an object is detected moving toward the charging location during the impedance check or during vehicle charging.

15. The method according to claim 1, further comprising: A first camera device is deployed for close-range observation of the charging position, and a second camera device is deployed for wide-area observation of an area surrounding the charging position.

16. A system for detecting foreign objects that impact a ground transceiver assembly (GTA) of a wireless power transfer (WPT) station, comprising: at least one camera device positioned to view an area surrounding a charging location of the GTA; an impedance measurement circuit, the impedance measurement circuit measuring the impedance of the wireless power transmission coil of the GTA; an imaging processor that analyzes images from the at least one camera to identify changes or features indicative of the introduction of foreign matter on an exposed surface of the GTA or in an area surrounding the GTA; as well as A foreign object detection (FOD) controller, when the image indicates the presence of foreign objects on the exposed surface of the GTA or in the area around the GTA, the foreign object detection (FOD) controller triggers an impedance check of the GTA through the impedance measurement circuit, and when the presence of foreign objects on the surface of the GTA is confirmed by the impedance check, the FOD controller initiates a fault protection operation.

17. The system of claim 16, wherein: The at least one camera includes a first camera positioned for a close-up view of the charging location and a second camera positioned for a wide-area view of an area surrounding the charging location.

18. The system of claim 16, wherein: The FOD controller enables and sets detection thresholds and perimeters around the GTA, schedules image processing by the image processor, and sends alarms and warnings to local and remote networked entities used to control the operation of the WPT station.

19. The system of claim 16, wherein: The FOD controller includes a processor programmed to collect local and remote data, settings and software, and use the collected data to verify the communication link and apply security settings to the WPT station.

20. The system of claim 19, wherein: The FOD controller also queries the at least one camera, the imaging processor, and each GTA of the WPT station to collect data captured while observing the area surrounding the charging location.

Images