POSITION SENSING BY ASYMMETRIC ELECTRIC COIL SENSOR

• US 20150369631A1
• Filed: 06/19/2015
• Published: 12/24/2015
• Est. Priority Date: 06/19/2014
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: CHEUNG, Charles Ho Yin, FOMIN, Evgeny, OBERHAUSER, Christopher Alan
• Granted Patent: US 10,573,453 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence
• CPC Class Codes: G01D 5/202 by movable a non-ferromagnetic conductive element G01D5/2033 takes precedence
• CPC Class Codes: H01F 27/2804 Printed windings

Abstract

A printed circuit board (PCB). The PCB comprises a non-conductive substrate and a plurality of conductive coil loops formed on the substrate, wherein the coil loops are asymmetric. The conductive coil loops are formed as a continuous metal trace on the substrate, the coil loops are symmetric with reference to a longitudinal axis of the PCB, the coil loops are asymmetric with reference to an axis transverse to the longitudinal axis of the PCB, wherein the distance between adjacent coil loops crossing the longitudinal axis on a first side of a center of an innermost coil loop are substantially equal, and the distance between adjacent coil loops crossing the longitudinal axis on a side of the center of the innermost coil loop opposite to the first side of the center of the innermost coil loop increase with each coil loop progressing outwards.

Claims

1. A printed circuit board (PCB), comprising:

a non-conductive substrate; and

a plurality of conductive coil loops formed on the substrate, wherein the coil loops form an asymmetric electric coil.

2. The printed circuit board of claim 1, wherein the coil loops form a substantially flat electric coil.

3. The printed circuit board of claim 2, wherein the coil loops of the asymmetric electric coil are asymmetric with reference to an axis transverse to a longitudinal axis of the asymmetric electric coil.

4. The printed circuit board of claim 3, wherein the distance between adjacent coil loops crossing the longitudinal axis on a first side of a center of an innermost coil loop is substantially equal and the distance between adjacent coil loops crossing the longitudinal axis on a side of the center of the innermost coil loop opposite to the first side of the center of the innermost coil loop increase with each coil loop progressing outwards.

5. The printed circuit board of claim 3, wherein a first distance between adjacent coil loops crossing the longitudinal axis on a first side of a center of an innermost coil loop is substantially equal and a second distance between adjacent coil loops crossing the longitudinal axis on a side of the center of the innermost coil loop opposite to the first side of the center of the innermost coil loop is substantially equal and wherein the second distance is at least two times as big as the first distance.

6. The printed circuit board of claim 1, wherein the coil loops are formed as a single continuous metal trace on the non-conductive substrate.

7. The printed circuit board of claim 1, wherein the coil loops have one of a triangular geometry, a rectangular geometry, or an oval geometry.

8. The printed circuit board of claim 1, wherein the coil loops are configured to generate a linear inductance versus target position response to a conductive target when the coil loops are stimulated with an excitation signal.

9. The printed circuit board of claim 1, wherein the coil loops are configured to generate a non-linear inductance versus target position response to a conductive target when the coil loops are stimulated with an excitation signal.

10. A position sensor, comprising:

an asymmetric electric coil comprising a plurality of conductive coil loops, wherein the coil loops are asymmetric with reference to an axis transverse to a longitudinal axis of the coil; and

a transducer coupled to the asymmetric coil, wherein the transducer is configured to provide an excitation signal to the asymmetric coil, to determine a response of the asymmetric coil to the excitation signal and to determine an output signal based on the response of the asymmetric coil to the excitation signal, wherein the output signal comprises an indication of position of an external target.

11. The position sensor of claim 10, further comprising a capacitor coupled to the transducer and coupled in parallel to the asymmetric coil, wherein the transducer is further configured to provide the excitation signal to the capacitor and wherein the transducer is configured to determine a response of the parallel circuit formed by the capacitor and the asymmetric coil, to determine an oscillation frequency of the parallel circuit formed by the capacitor and the asymmetric coil, and to determine the output signal based on the oscillation frequency of the parallel circuit formed by the capacitor and the asymmetric coil.

12. The position sensor of claim 10, wherein the asymmetric coil is configured to generate an asymmetric time-varying magnetic field in response to the excitation signal, wherein the asymmetric coil is configured to generate an asymmetric time-varying magnetic field in response to the excitation signal;

wherein the magnetic field is magnified by a relative permeability p in the external target thereby causing an increase of the inductance of the asymmetric coil that varies in magnitude based on a position of the external target relative to the asymmetric coil, and wherein the asymmetric coil is configured to present varying inductance in response to a time-varying magnetic field induced in the external target, and wherein the external target comprises a ferrous material.

13. The position sensor of claim 10, wherein the asymmetric coil is configured to generate an asymmetric time-varying magnetic field in response to the excitation signal, whereby eddy currents are induced in the external target that vary in magnitude based on a position of the target relative to the asymmetric coil, and wherein the asymmetric coil is configured to present varying inductance in response to a time-varying magnetic field generated by the varying eddy currents induced in the external target, and wherein the external target comprises a non-ferrous material.

14. The position sensor of claim 10, wherein the transducer is an inductance-to-digital converter (LDC).

15. A method of determining position of an object, comprising:

exciting an asymmetric electric coil with an alternating current signal;

generating a time-varying asymmetric magnetic field by the asymmetric electric coil;

inducing eddy currents in an electrically conductive target coupled to the object by action of the time-varying asymmetric magnetic field, wherein an amplitude of the eddy currents is determined by the position of the target relative to the asymmetric magnetic field;

determining an inductance of the asymmetric electric coil, wherein the inductance varies in part based on the eddy currents induced in the target; and

determining a position of the object based on the inductance of the asymmetric electric coil.

16. The method of claim 15, wherein determining the inductance of the asymmetric electric coil includes identifying a resonant frequency in a circuit comprising the asymmetric electric coil.

17. The method of claim 15, wherein the position of the object is one of position of a clutch, position of a headlamp, or position of a machine table.

18. The method of claim 15, wherein the inductance of the asymmetric electric coil increases as the electrically conductive target moves from an outer edge of the asymmetric electric coil towards a center of the asymmetric electric coil increases.

19. The method of claim 15, wherein the inductance of the asymmetric electric coil increases as the electrically conductive target moves from an outer edge of the asymmetric electric coil towards a center of the asymmetric electric coil decreases.

21. The printed circuit board of claim 18, wherein the coil loops have one of a triangular geometry, a rectangular geometry, or an oval geometry.

22. The printed circuit board of claim 18, wherein the coil loops are configured to generate one of a linear or a non-linear inductance versus target position response to a conductive target when the coil loops are stimulated with an excitation signal.

20. A printed circuit board (PCB), comprising:

a non-conductive substrate; and

a plurality of conductive coil loops formed as a continuous metal trace on the substrate, wherein the coil loops are asymmetric with reference to an axis transverse to a longitudinal axis of the printed circuit board, wherein a first distance between adjacent coil loops crossing the longitudinal axis on a first side of a center of an innermost coil loop are substantially equal, and a second distance between adjacent coil loops crossing the longitudinal axis on a side of the center of the innermost coil loop opposite to the first side of the center of the innermost coil loop are substantially equal and wherein the second distance is at least two times as big as the first distance.