Device alignment in inductive power transfer systems

1. A wireless power receiver comprising:

a first inductive element configured to receive wireless charging power from a transmitter;

a second inductive element, laterally separated from the first, configured to receive wireless charging power from the transmitter;

a switch configured to, intermittently, electrically couple a first node, common to both the first and second inductive elements, with a second node, common to both a first sensor and a second sensor;

the first sensor configured to measure a characteristic between one end of the first inductive element, opposite the first node, and the second node;

the second sensor configured to measure a characteristic between one end of the second inductive element, opposite the first node, and the second node; and

a position detector configured to determine a lateral position of the receiver relative to the transmitter based on the measured characteristics, and to provide at least one output for alignment of a vehicle comprising the wireless power receiver based on the determined lateral position.

2. The wireless power receiver of claim 1 , wherein at least one characteristic comprises an induced voltage at the first and second inductive elements.

3. The wireless power receiver of claim 1 , wherein the first and second inductive elements are electrically connected in series in a “double D” configuration.

4. The wireless power receiver of claim 3 , wherein the switch is configured to electrically partition the first and second inductive elements.

5. The wireless power receiver of claim 1 , further comprising a quadrature coil substantially between the first and second inductive elements.

6. The wireless power receiver of claim 1 , wherein the position detector is further configured to determine a longitudinal position of the receiver relative to the transmitter based on a gradient of a scalar alignment parameter.

7. The wireless power receiver of claim 1 , wherein the vehicle comprises an automatic alignment system configured to align the vehicle with respect to the transmitter based on the determined lateral position.

8. A method of detecting alignment at a wireless power receiver, comprising:

receiving wireless power at a first inductive element from a transmitter;

receiving wireless power at a second inductive element from the transmitter;

intermittently, electrically coupling a first node, common to both the first and second inductive elements, with a second node, common to both a first sensor and a second sensor;

measuring, at the first sensor, a characteristic between one end of the first inductive element, opposite the first node, and the second node;

measuring, at the second sensor, a characteristic between one end of the second inductive element, opposite the first node, and the second node; and

determining a lateral position of the receiver relative to the transmitter based on the measured characteristics; and providing at least one output for alignment of a vehicle comprising the wireless power receiver based on the determined lateral position.

9. The method of claim 8 , wherein at least one characteristic comprises an induced voltage at the first and second inductive elements.

10. The method of claim 8 , wherein the first and second inductive elements are electrically connected in series in a “double D” configuration.

11. The method of claim 10 , further comprising electrically partitioning the first and second inductive elements.

12. The method of claim 8 , further comprising receiving wireless power at a quadrature coil substantially between the first and second inductive elements.

13. The method of claim 8 , further comprising determining a longitudinal position of the receiver relative to the transmitter based on a gradient of a scalar alignment parameter.

14. The method of claim 8 , further comprising aligning the vehicle with respect to the transmitter based on the determined lateral position.

15. An apparatus for detecting alignment at a wireless power receiver, comprising:

a first inductive element configured to receive wireless charging power from a transmitter;

a second inductive element configured to receive wireless charging power from a transmitter;

means for, intermittently, electrically coupling a first node, common to both the first and second inductive elements, with a second node, common to both a first means for measuring and a second means for measuring;

the first means for measuring a characteristic between one end of the first inductive element, opposite the first node, and a second node;

the second means for measuring a characteristic between one end of the second inductive element, opposite the first node, and a second node; and

means for determining a lateral position of the receiver relative to the transmitter based on the measured characteristics; and means for providing at least one output for alignment of a vehicle comprising the wireless power receiver based on the determined lateral position.

16. The apparatus of claim 15 , wherein at least one characteristic comprises an induced voltage at the first and second inductive elements.

17. The apparatus of claim 15 , wherein the first and second inductive elements are electrically connected in series in a “double D” configuration.

18. The apparatus of claim 17 , further comprising means for electrically partitioning the first and second inductive elements.

19. The apparatus of claim 15 , further comprising a quadrature coil substantially between the first and second inductive elements.

20. The apparatus of claim 15 , further comprising means for determining a longitudinal position of the receiver relative to the transmitter based on a gradient of a scalar alignment parameter.

21. The apparatus of claim 15 , further comprising means for aligning the vehicle with respect to the transmitter based on the determined lateral position.

22. A non-transitory computer-readable medium comprising code that, when executed, causes a wireless charging apparatus to:

receive wireless power at a first inductive element from a transmitter;

receive wireless power at a second inductive element from the transmitter;

intermittently, electrically couple a node common to both the first and second inductive elements, with a second node, common to both a first sensor and a second sensor;

measure, at the first sensor, a characteristic between one end of the first inductive element, opposite the first node, and the second node;

measure, at the second sensor, a characteristic between one end of the second inductive element, opposite the first node, and the second node; and

determine a lateral position of the receiver relative to the transmitter based on the measured characteristics; and provide at least one output for alignment of a vehicle comprising the wireless charging apparatus based on the determined lateral position.

23. The medium of claim 22 , wherein at least one characteristic comprises an induced voltage at the first and second inductive elements.

24. The medium of claim 22 , wherein the first and second inductive elements are electrically connected in series in a “double D” configuration.

25. The medium of claim 24 , further comprising code that, when executed, causes the apparatus to electrically partition the first and second inductive elements.

26. The medium of claim 22 , further comprising code that, when executed, causes the apparatus to receive wireless power at a quadrature coil substantially between the first and second inductive elements.

27. The medium of claim 22 , further comprising code that, when executed, causes the apparatus to determine a longitudinal position of the receiver relative to the transmitter based on a gradient of a scalar alignment parameter.

28. The medium of claim 22 , further comprising code that, when executed, causes the apparatus to align the vehicle with respect to the transmitter based on the determined lateral position.