SENSE COIL GEOMETRIES WITH IMPROVED SENSITIVITY FOR METALLIC OBJECT DETECTION IN A PREDETERMINED SPACE

• US 20160238731A1
• Filed: 08/04/2015
• Published: 08/18/2016
• Est. Priority Date: 02/17/2015
• Status: Active Grant

• Current Assignee: WiTricity Corporation
• Original Assignee: Qualcomm, Inc.
• Inventors: Chopra, Swagat, Percebon, Leandro Alberto, Werner, Michael
• Granted Patent: US 10,122,192 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60L 53/122 Circuits or methods for driving the primary coil, e.g. supplying electric power to the coil
• CPC Class Codes: B60L 53/124 Detection or removal of foreign bodies
• CPC Class Codes: 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
• CPC Class Codes: B60L 53/36 by positioning the vehicle
• CPC Class Codes: B60L 53/38 specially adapted for charging by inductive energy transfer
• CPC Class Codes: G01V 3/10 using induction coils
• CPC Class Codes: G01V 3/101 by measuring the impedance of the search coil; by measuring features of a resonant circuit comprising the search coil measuring impedance or characteristics derived therefrom G01R27/00, e.g. quality factor G01R27/26
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H02J 7/0042 characterised by the mechanical construction
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

This disclosure provides systems, methods and apparatus for detecting a presence of an object. In one aspect an apparatus for detecting a presence of an object is provided. The apparatus includes a sense coil formed from a conductor having a predetermined shape configured to attenuate currents induced in the conductor by an external time-varying magnetic field. The sense coil has an electrical characteristic that varies as a function of the presence of the object. The apparatus comprises a detection circuit coupled to the sense coil and configured to detect the presence of the object in response to detecting a difference between a measured value of the electrical characteristic and a reference value for the electrical characteristic. The reference value for the electrical characteristic is substantially the same as the measured value of the electrical characteristic in the absence of the object over at least a portion of the sense coil.

Claims

1. An apparatus for detecting a presence of an object, the apparatus comprising:

a sense coil having a plurality of sides defined by a conductor, wherein for each of the plurality of sides of the sense coil, the conductor bows toward a center of the sense coil as the conductor extends from an outer portion of the respective side of the sense coil toward a middle portion of the respective side of the sense coil, and wherein the sense coil has an electrical characteristic that varies as a function of the presence of the object; and

a detection circuit coupled to the sense coil and configured to detect the presence of the object in response to detecting a difference between a measured value of the electrical characteristic and a reference value for the electrical characteristic.

2. The apparatus of claim 1, wherein the reference value for the electrical characteristic is substantially the same as the measured value of the electrical characteristic in the absence of the object over at least a portion of the sense coil.

3. The apparatus of claim 1, wherein a shape of the sense coil decreases a difference between a maximum measurable value of the electrical characteristic when the object is located over at least a portion of the sense coil and the measured value of the electrical characteristic when the object is located substantially over a center of the sense coil as compared to a substantially rectangular sense coil.

4. The apparatus of claim 1, wherein at each corner of corresponding sides of the coil, the conductor is bent at an acute angle with respect to a direction of extension of each of the corresponding sides to form substantially rounded corners.

5. The apparatus of claim 4, wherein the acute angle is substantially 45°

.

6. The apparatus of claim 1, wherein at each corner of corresponding sides of the coil, the conductor is bent at a substantially 90 degree angle with respect to a direction of extension of each of the corresponding sides.

7. The apparatus of claim 1, wherein the conductor of the coil forms a plurality of windings and for at least one winding on one side of the plurality of sides of the coil, the conductor extends in a substantially straight line along the entire side.

8. The apparatus of claim 1, wherein the conductor of the coil forms a plurality of windings and wherein successive windings of the plurality of windings bow toward a center of the coil to an increasing extent from an outermost winding to an innermost winding.

9. The apparatus of claim 1, wherein the conductor of the coil forms a plurality of windings and wherein the conductor extends in a substantially straight line along an entirety of each of the plurality of sides for at least one of the plurality of windings.

10. The apparatus of claim 1, wherein the middle portion of opposite sides of the coil are closer to one another than the outer portion of the opposite sides of the coil are to one another.

12. The method of claim 1, wherein the reference value for the electrical characteristic is substantially the same as the measured value of the electrical characteristic in the absence of the object over at least a portion of the sense coil.

11. A method for detecting a presence of an object, the method comprising:

determining a measured value of an electrical characteristic of a sense coil that varies as a function of the presence of the object, the sense coil having a plurality of sides defined by a conductor, wherein for each of the plurality of sides of the sense coil, the conductor bows toward a center of the sense coil as the conductor extends from an outer portion of the respective side of the sense coil toward a middle portion of the respective side of the sense coil, and

detecting the presence of the object in response to detecting a difference between the measured value of the electrical characteristic and a reference value for the electrical characteristic.

13. The method of claim 11, wherein a shape of the sense coil decreases a difference between a maximum measurable value of the electrical characteristic when the object is located over at least a portion of the sense coil and the measured value of the electrical characteristic when the object is located substantially over a center of the sense coil as compared to a substantially rectangular sense coil.

14. The method of claim 11, wherein at each corner of corresponding sides of the coil, the conductor is bent at an acute angle with respect to a direction of extension of each of the corresponding sides to form substantially rounded corners.

15. The method of claim 14, wherein the acute angel is substantially 45°

.

16. The method of claim 11, wherein at each corner of corresponding sides of the coil, the conductor is bent at a substantially 90 degree angle with respect to a direction of extension of each of the corresponding sides.

17. The method of claim 11, wherein the conductor of the coil forms a plurality of windings and for at least one winding on one side of the plurality of sides of the coil, the conductor extends in a substantially straight line along the entire side.

18. The method of claim 11, wherein the conductor of the coil forms a plurality of windings and wherein successive windings of the plurality of windings bow toward a center of the coil to an increasing extent from an outermost winding to an innermost winding.

19. The method of claim 11, wherein the conductor of the coil forms a plurality of windings and wherein the conductor extends in a substantially straight line along an entirety of each of the plurality of sides for at least one of the plurality of windings.

20. The method of claim 11, wherein the middle portion of opposite sides of the coil are closer to one another than the outer portion of the opposite sides of the coil are to one another.

21. An apparatus for detecting a presence of an object, the apparatus comprising:

a sense coil having an outer loop and an inner loop defined by a conductor that crosses itself at a transition between the outer loop and the inner loop and wherein the sense coil has an electrical characteristic that varies as a function of the presence of the object; and

a detection circuit coupled to the sense coil and configured to detect the presence of the object in response to detecting a difference between a measured value of the electrical characteristic and a reference value for the electrical characteristic.

22. The apparatus of claim 21, wherein the reference value for the electrical characteristic is substantially the same as the measured value of the electrical characteristic in the absence of the object over at least a portion of the sense coil.

23. The apparatus of claim 21, wherein a shape of the sense coil decreases a difference between a maximum measurable value of the electrical characteristic when the object is located over at least a portion of the sense coil and the measured value of the electrical characteristic when the object is located substantially over a center of the sense coil as compared to a substantially rectangular sense coil.

24. The apparatus of claim 21, wherein a current flowing in the outer loop flows in a same clockwise or counter-clockwise direction as in the inner loop.

25. The apparatus of claim 21, wherein a shape of the sense coil provides increased sensitivity for detecting the presence of the object located at least partially over one or both of the outer loop and the inner loop as compared to a rectangular sense coil having substantially a same outer dimension as the outer loop.

26. A method for detecting a presence of an object, the method comprising:

determining a measured value of an electrical characteristic of a sense coil that varies as a function of the presence of the object, the sense coil having an outer loop and an inner loop defined by a conductor that crosses itself at a transition between the outer loop and the inner loop, and

detecting the presence of the object in response to detecting a difference between the measured value of the electrical characteristic and a reference value for the electrical characteristic.

27. The method of claim 26, wherein the reference value for the electrical characteristic is substantially the same as the measured value of the electrical characteristic in the absence of the object over at least a portion of the sense coil.

28. The method of claim 26, wherein a shape of the sense coil decreases a difference between a maximum measurable value of the electrical characteristic when the object is located over at least a portion of the sense coil and the measured value of the electrical characteristic when the object is located substantially over a center of the sense coil as compared to a substantially rectangular sense coil.

29. The method of claim 26, wherein a current flowing in the outer loop flows in a same clockwise or counter-clockwise direction as in the inner loop.

30. The method of claim 26, wherein a shape of the sense coil provides increased sensitivity for detecting the presence of the object located at least partially over one or both of the outer loop and the inner loop as compared to a rectangular sense coil having substantially a same outer dimension as the outer loop.