# US 11,077,762 B2 · Systems, methods, and apparatus for detection of metal objects in a predetermined space

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- Number: US 11,077,762 B2
- Document ID: US11077762B2
- Status: Granted
- Kind: B2
- Application number: 16/838,701
- Filed: 2020-04-02
- Published: 2020-07-23
- Granted: 2021-08-03
- Earliest claimed: 2012-07-13
- Assignees: WiTricity Corporation
- Applicants: WiTricity Corporation
- Inventors: Hanspeter Widmer; Markus Bittner; Lukas Sieber; Marcel Fischer
- Web page: https://patentgrep.com/patent/US11077762B2

## CPC

- B60L 53/124: Detection or removal of foreign bodies
- B60L 3/003: {relating to inverters}
- B60L 3/0038: {relating to sensors}
- B60L 3/0046: {relating to electric energy storage systems, e.g. batteries or capacitors}
- B60L 3/04: Cutting off the power supply under fault conditions (protective devices and circuit arrangements in general H01H; H02H)
- B60L 50/16: with provision for separate direct mechanical propulsion
- B60L 50/51: characterised by AC-motors
- B60L 50/66: {Arrangements of batteries}
- B60L 53/12: Inductive energy transfer
- B60L 53/122: Circuits or methods for driving the primary coil, e.g. supplying electric power to the coil
- B60L 53/126: Methods for pairing a vehicle and a charging station, e.g. establishing a one-to-one relation between a wireless power transmitter and a wireless power receiver
- B60L 53/30: Constructional details of charging stations
- B60L 53/305: {Communication interfaces}
- B60L 53/36: by positioning the vehicle
- B60L 53/37: using optical position determination, e.g. using cameras
- B60L 53/63: in response to network capacity
- B60L 53/65: involving identification of vehicles or their battery types
- B60L 53/68: Off-site monitoring or control, e.g. remote control
- B60L 55/00: Arrangements for supplying energy stored within a vehicle to a power network, i.e. vehicle-to-grid [V2G] arrangements
- B60L 58/10: for monitoring or controlling batteries
- G01D 5/2006: {by influencing the self-induction of one or more coils (G01D5/22 takes precedence)}
- G01N 27/725: {by using magneto-acoustical effects or the Barkhausen effect}
- H01F 38/14: Inductive couplings
- H02J 50/12: of the resonant type
- H02J 50/60: responsive to the presence of foreign objects, e.g. detection of living beings
- H04B 5/73: for taking measurements, e.g. using sensing coils
- B60L 2200/12: Bikes
- B60L 2200/22: Microcars, e.g. golf cars
- B60L 2210/30: AC to DC converters
- B60L 2210/40: DC to AC converters
- B60L 2240/36: Temperature of vehicle components or parts
- B60L 2240/525: Temperature of converter or components thereof
- B60L 2250/16: by display
- B60L 2270/147: electro magnetic [EMI]
- B60L 2270/32: of electricity
- B60L 2270/34: of parts
- G01V 3/10: using induction coils
- H04B 5/79: for data transfer in combination with power transfer
- Y02E 60/00: Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02T 10/70: Energy storage systems for electromobility, e.g. batteries
- Y02T 10/7072: Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
- Y02T 10/72: Electric energy management in electromobility
- Y02T 90/12: Electric charging stations
- Y02T 90/14: Plug-in electric vehicles
- Y02T 90/16: Information or communication technologies improving the operation of electric vehicles
- Y02T 90/167: Systems integrating technologies related to power network operation and communication or information technologies for supporting the interoperability of electric or hybrid vehicles, i.e. smartgrids as interface for battery charging of electric vehicles [EV] or hybrid vehicles [HEV]
- Y04S 10/126: the energy generation units being or involving electric vehicles [EV] or hybrid vehicles [HEV], i.e. power aggregation of EV or HEV, vehicle to grid arrangements [V2G]
- Y04S 30/12: Remote or cooperative charging
- Y04S 30/14: Details associated with the interoperability, e.g. vehicle recognition, authentication, identification or billing
- B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H04B: TRANSMISSION
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y04S: SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS

## Abstract

This disclosure provides systems, methods and apparatus for detecting foreign objects. In one aspect an apparatus for detecting a presence of an object is provided. The apparatus includes a resonant circuit having a resonant frequency. The resonant circuit includes a sense circuit including an electrically conductive structure. The apparatus further includes a coupling circuit coupled to the sense circuit. The apparatus further includes a detection circuit coupled to the sense circuit via the coupling circuit. The detection circuit is configured to detect the presence of the object in response to detecting a difference between a measured characteristic that depends on a frequency at which the resonant circuit is resonating and a corresponding characteristic that depends on the resonant frequency of the resonant circuit. The coupling circuit is configured to reduce a variation of the resonant frequency by the detection circuit in the absence of the object.

## Claims

### Claim 1

An apparatus for detecting a presence of an object in a predetermined area of a wireless charging system, the apparatus comprising:
a first electrically conductive structure configured to wirelessly transfer power via generating a first alternating magnetic field at a first frequency and at a level sufficient to power or charge a load;
a second electrically conductive structure and a third electrically conductive structure positioned within the first alternating magnetic field generated by the first electrically conductive structure; and
a detection circuit configured to generate a second alternating magnetic field operating at a second frequency different from the first frequency by driving a sense current in the respective second electrically conductive structure at the second frequency;
wherein the detection circuit is further configured to measure at least one electrical characteristic at least in part based on a voltage induced into the third electrically conductive structure by the second alternating magnetic field, and configured to detect the presence of the object in the predetermined area based on the measured at least one electrical characteristic.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein each of the second and the third electrically conductive structures forms an electrically conductive loop of at least one turn.

### Claim 3 (depends on 1)

The apparatus of claim 1, wherein the second electrically conductive structure is configured to generate the second alternating magnetic field substantially in at least a portion of the predetermined area where the object may be present.

### Claim 4 (depends on 1)

The apparatus of claim 1, further comprising a multi-dimensional array including a plurality of the third electrically conductive structures configured for detecting presence of the object in the predetermined area, each third electrically conductive structure positioned within the first alternating magnetic field, wherein the detection circuit is further configured to measure the at least one electrical characteristic at least in part based on the voltage induced into each third electrically conductive structure by the second alternating magnetic field.

### Claim 5 (depends on 4)

The apparatus of claim 4, wherein the multi-dimensional array is substantially planar and disposed in a layer between the first electrically conductive structure and a surface of an enclosure of the wireless charging system.

### Claim 6 (depends on 4)

The apparatus of claim 4, wherein the multi-dimensional array includes a plurality of the second electrically conductive structures, wherein the detection circuit is configured to drive a respective sense current in each of the second electrically conductive structures at the second frequency.

### Claim 7 (depends on 1)

The apparatus of claim 1, wherein the third electrically conductive structure is configured and positioned such that, in absence of the object, flux of the alternating magnetic field generated by the second electrically conductive structure passing through the third electrically conductive structure substantially cancels out resulting in substantially zero coupling between the second and the third electrically conductive structure.

### Claim 8 (depends on 1)

The apparatus of claim 1, wherein the third electrically conductive structure comprises an orthogonal arrangement of loops substantially in perpendicular planes to sense different components of the magnetic flux as generated by the second electrically conductive structure.

### Claim 9 (depends on 1)

The apparatus of claim 1, wherein the third electrically conductive structure comprises a pair of loops configured to be part of an induction balance that is maintained balanced and that gets temporarily unbalanced by the presence of the object.

### Claim 10 (depends on 1)

The apparatus of claim 1, wherein at least one of the second and third electrically conductive structure comprises a pair of co-planar loops configured as a figure-eight loop such that, when driven with a current, the current in the first loop circulates in a direction opposite to the current in the second loop.

### Claim 11 (depends on 1)

The apparatus of claim 1, wherein the at least one electrical characteristic comprises at least one of a voltage, a current, a power, a mutual impedance, a mutual inductance, a coupling, a level of magnetic field, an amplitude and phase.

### Claim 12 (depends on 1)

The apparatus of claim 1, wherein the detection circuit is configured to generate a sense current signal that is one of a swept frequency signal, an impulse, and a pseudo random noise.

### Claim 13 (depends on 1)

The apparatus of claim 1, wherein the detection circuit is configured to generate a sense current signal at a frequency different from the fundamental or harmonics of the first alternating magnetic field to reduce an interference.

### Claim 14 (depends on 1)

The apparatus of claim 1, wherein the detection circuit is configured to apply a sense current signal in time intervals between switching transients associated with the wireless power transfer to reduce a noise.

### Claim 15 (depends on 4)

The apparatus of claim 4, wherein the detection circuit comprises a multiplexer configured to selectively measure the at least one electrical characteristic associated with a selected one of the plurality of third electrically conductive structures.

### Claim 16 (depends on 4)

The apparatus of claim 4, wherein the detection circuit is configured to map values indicative of the at least one electrical characteristics measured onto an array of values based on position of each third electrically conductive structure, wherein the detection circuit is further configured to detect the presence of the object based in part on the array of values.

### Claim 17 (depends on 16)

The apparatus of claim 16, wherein the detection circuit is configured to determine a pattern within the array of values, the pattern indicative of one or more residual effects of at least one of a vehicle pad, a vehicle underbody structure, a vehicle position, an alignment offset, an air gap condition, a temperature, water, snow, ice, foliage, aging or a combination thereof.

### Claim 18 (depends on 16)

The apparatus of claim 16, wherein the detection circuit is configured to detect the presence of the object based on differences in one or more of the at least one electrical characteristic measured as compared to a pattern identified from the array of values.

### Claim 19 (depends on 16)

The apparatus of claim 16, wherein a decision threshold based on a change in one or more of the at least one electrical characteristic measured is determined or adjusted based on a pattern identified from the array of values.

### Claim 20 (depends on 19)

The apparatus of claim 19, wherein the decision threshold is adjusted such that detection sensitivity is increased for detecting objects that produce sudden or abrupt and local changes in patterns identified from the arrays of values.

### Claim 21 (depends on 20)

The apparatus of claim 20, wherein the local change in the patterns identified from sequentially acquired patterns corresponds to a change in measured characteristics associated with a portion of the plurality of third electrically conductive structures as compared to the measured characteristics associated with a larger portion of the plurality of third electrically conductive structures.

### Claim 22 (depends on 16)

The apparatus of claim 16, wherein a pattern identified within the array of values is one of a plurality of sequential patterns corresponding to sequentially acquired arrays of values, and wherein the detection circuit is configured to detect the presence of the object based at least in part on the plurality of sequential patterns.

### Claim 23 (depends on 22)

The apparatus of claim 22, wherein the sequential patterns are indicative of temperature drift characteristics.

### Claim 24

An apparatus for detecting a presence of an object in an inductive charging system, the apparatus comprising:
a first electrically conductive structure configured to wirelessly transfer power via generating an alternating magnetic field at a level sufficient to power or charge a load, the magnetic field operating at a frequency;
a plurality of resonant sense circuits, each comprising a respective second electrically conductive structure different from the first electrically conductive structure, a respective first capacitor electrically connected in parallel to the respective second electrically conductive structure, and a respective second capacitor electrically connected in series to the parallel connection of the respective second electrically conductive structure capacitor and the respective first capacitor, each of the plurality of resonant sense circuits having a respective resonant frequency different than the frequency of the alternating magnetic field,
wherein each of the respective second electrically conductive structures forms a portion of a multi-dimensional array of second electrically conductive structures positioned within the alternating magnetic field generated by the first electrically conductive structure; and
a detection circuit configured to generate a sense current in the respective second electrically conductive structure of at least one of the plurality of resonant sense circuits and configured to measure at least one electrical characteristic of the at least one of the plurality of resonant sense circuits and detect the presence of the object based on the measured at least one electrical characteristic,
wherein the detection circuit comprises a multiplexer configured to selectively apply the sense current to any one of the plurality of resonant sense circuits.

### Claim 25 (depends on 24)

The apparatus of claim 24, wherein each of the respective second capacitors is configured to attenuate a voltage induced at the respective second electrically conductive structure by the alternating magnetic field.

### Claim 26 (depends on 24)

The apparatus of claim 24, wherein at least a portion of the capacitance of the respective first capacitors is inherent to the respective second electrically conductive structure.

### Claim 27 (depends on 24)

The apparatus of claim 24, the electrical characteristic comprises at least one of a voltage, a current, an impedance, a resonant frequency, a Q-factor, a dampening factor, an inductance, a resistance, an amplitude and a phase, a frequency response, a pulse response.

### Claim 28 (depends on 24)

The apparatus of claim 24, wherein the detection circuit measures the at least one electrical characteristic at one or more frequencies.