Position sensor having compact arrangement of coils

• US 6,522,128 B1
• Filed: 06/08/2000
• Issued: 02/18/2003
• Est. Priority Date: 10/15/1997
• Status: Expired due to Term

• Current Assignee: Synaptics (UK) Ltd. (Synaptics Incorporated)
• Original Assignee: Synaptics (UK) Ltd. (Synaptics Incorporated)
• Inventors: Ely, David T. F., Dames, Andrew N.
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US09/529,387
• Time in Patent Office: 985 Days
• Field of Search: 324/207.17, 324/207.12, 324/207.24, 324/207.25, 324/207.16, 324/207.15, 336/45, 336/200, 336/79, 340/870.32
• US Class Current: 324/207.17
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01D 5/204 by influencing the mutual induction between two or more coils G01D5/22 takes precedence
• CPC Class Codes: H05K 1/165 incorporating printed inductors

Abstract

A transducer is provided for use in a position sensor which senses the position of two relatively movable members. In one form, the transducer has a plurality of sensor windings having a number of loops arranged in succession and connected in series so that signals induced in adjacent loops by a common electromagnetic field oppose each other and an excitation winding having at least one loop super-imposed on but electrically isolated from the loops of the sensor windings.

Claims

1. An apparatus for use in a position encoder comprising:

a first plurality of conductor tracks arranged along a measurement path;

a second plurality of conductor tracks arranged along said measurement path;

wherein the first and second pluralities of conductor tracks are superimposed on each other to define (i) a first circuit having at least two series connected loops arranged along the measurement path; and

(ii) a second circuit having at least one loop which extends along said measurement path;

characterised in that the conductor tracks of said first plurality of conductor tracks which form part of said first circuit are arranged in first and second groups which are transversely spaced relative to said measurement path;

the conductor tracks of said second plurality of conductor tracks which form part of said first circuit are arranged for connecting conductor tracks in the first group with conductor tracks in the second group; and

the conductor track or tracks of said first plurality of conductor tracks which form said at least one loop of said second circuit are located between and electrically separate from said first and second groups of conductor tracks.

2. An apparatus according to claim 1, wherein said first and second plurality of conductor tracks are carried on a respective side of a substantially planar insulator.

3. An apparatus according to claim 1, wherein said first and second plurality of conductor tracks are formed on a respective side of a printed circuit board.

4. An apparatus according to claim 1, wherein said loops of said first circuit have a generally hexagonal shape.

5. An apparatus according to claim 1, wherein said first and second plurality of conductor tracks define a plurality of said first circuits which are electrically separate from each other and are located one on the other, and wherein the at least two loops of the respective first circuits are spatially separated along said measurement path.

6. An apparatus according to claim 1, wherein said first circuit comprises an even number of said loops which are arranged in succession along said measurement path.

7. An apparatus according to claim 1, wherein said first and second circuits are arranged so that there is substantially no net electromagnetic coupling therebetween.

8. An apparatus according to claim 1, wherein said at least two loops are wound to have opposite sense and wherein a coupling area between one or more loops of one sense of said first circuit and said at least one loop of said second circuit is varied to oppose the effect of a variation in coupling between the at least one loop of said second circuit and a loop of the other sense of the first circuit caused by an arrangement of conductor tracks to said at least one loop of said second circuit.

9. An apparatus according to claim 1, wherein said second circuit comprises a plurality of turns of a spiral wound conductor track.

10. An apparatus according to claim 1, wherein said second circuit comprises a plurality of concentric spiral windings wound in the same sense and connected in series.

11. An apparatus according to claim 1, wherein said second circuit comprises at least one outer loop and at least one inner loop, and wherein said inner and outer loops are wound in the opposition direction to each other.

12. An apparatus according to claim 1, wherein said measurement path is linear.

13. An apparatus according to claim 1, wherein said measurement path is circular.

14. An apparatus according to claim 1, wherein said first and second pluralities of conductor tracks are arranged so that each loop of said first circuit is formed by a plurality of turns of conductor, and wherein the turns of conductor are spatially separated in the measurement direction so as to reduce spatial harmonic distortions.

15. An apparatus according to claim 1, wherein a pair of electrically separated connection tracks are provided to said first circuit and wherein one of said connection tracks is superimposed on the other connection track when viewed in a direction perpendicular to said measurement path.

16. An apparatus according to claim 1, wherein the area enclosed by each of the loops of said first circuit are substantially the same.

17. A position sensor comprising:

first and second members which are relatively moveable along a measurement path;

said first member comprising an apparatus according to claim 1; and

said second member comprising means for interacting with said circuits on said apparatus such that in response to an input driving signal applied to one of said circuits, there is induced in the other said circuit an output signal which varies as a function of the relative position between said first and second members along said measurement path.

18. A sensor according to claim 17, wherein said interacting means comprises an electromagnetic field generator.

19. A sensor according to claim 17, wherein said interacting means comprises at least one of:

an electromagnetic resonant device, a short circuit coil, a conductive screen or a ferrite pole piece.

20. A sensor according to claim 17, wherein said interacting means and said at least two loops of said first circuit are arranged so that said output signal continuously varies as a function of the relative position of said first and second members along said measurement path.

21. A sensor according to claim 20, wherein said output signal varies periodically as a function of the relative position between said interacting means and said at least two loops.

22. A sensor according to claim 21, wherein said periodic variation is substantially sinusoidal.

23. A sensor according to any of claims 17, further comprising drive means for applying said input driving signal to one of said first and second circuits and processing means for processing the signal generated in said other circuit and for providing an indication therefrom of the relative position of said first and second members.

24. A sensor according to claim 23, wherein said processing means comprises a demodulator which is matched to the phase of the signal generated in said other circuit by said interacting means.

25. A sensor according to claim 24, wherein said demodulator is operable to demodulate said signal using a 90°

phase shifted version of the excitation signal.

26. A sensor according to claims 23, wherein said apparatus comprises two or more of said first circuits, wherein the loops of the respective first circuits are spatially separated along said measurement path and wherein said processing circuit is operable to perform a trigonometric ratio calculation of the signals generated in said two or more first circuits.

27. A sensor according to any of claims 23, wherein said output signal generated in said other circuit varies sinusoidally as a function of the position along said path of said interacting means relative to said at least two loops, and wherein one period of said sinusoidal variation corresponds to a relative movement along the measurement path of the extent of two of said series connected loops.

28. A sensor according to any of claims 23, wherein said first and second circuits are mounted on a circuit board, and wherein said drive means and/or said processing means is mounted on said circuit board.

29. A sensor according to any of claims 17, wherein said first and second circuits are formed on substantially planar surfaces.

30. A sensor according to claim 29, wherein said interacting means comprises a coil and wherein the axis of the coil is generally perpendicular to said planar surface.

31. A sensor according to claim 30, wherein the first and second circuits lie in substantially the same plane, and wherein said coil is movable relative to said first and second circuits in a plane which is substantially parallel to the plane in which said first and second circuits lie.

32. A sensor according to any of claims 17, wherein said first member is fixed and wherein said second member is movable with respect to said first member.

33. A method of detecting the position of first and second members which are relatively moveable along a measurement path, the method comprising the steps of:

providing a position sensor according to claim 17;

applying a drive signal to one of the circuits on said apparatus; and

detecting the signal generated in said other circuit and deriving therefrom the relative position of said first and second members.

34. A method according to claim 33, wherein said driving signal comprises an alternating signal having a frequency in the range of 10 KHz to 10 MHz.

35. An apparatus for use in a position encoder comprising:

an insulator base defining first and second surfaces which extend along a measurement path;

a first plurality of conductor tracks arranged on said first surface along said measurement path;

a second plurality of conductor tracks arranged on said second surface along said measurement path;

wherein the insulator base comprises a plurality of via holes for connecting the conductor tracks on the first surface to the conductor tracks on the second surface to define (i) a first circuit having at least two series connected loops arranged along the measurement path; and

(ii) a second circuit having at least one loop which extends along said measurement path;

characterised in that the first and second plurality of conductor tracks and said via holes are arranged so that the at least one loop of said second circuit extends across the at least two loops of said first circuit.

36. An apparatus for use in a position encoder comprising:

an insulator base defining first and second surfaces which extend along a measurement path;

a first plurality of conductor tracks arranged on said first surface along said measurement path;

a second plurality of conductor tracks arranged on said second surface along said measurement path;

wherein the insulator base comprises a plurality of via holes for connecting the conductor tracks on the first surface to the conductor tracks on the second surface to define (i) a first circuit having at least two series connected loops arranged along the measurement path; and

(ii) a second circuit having at least one loop which extends along said measurement path;

characterised in that;

the conductor tracks on said first surface which form part of said first circuit are arranged in first and second groups which are transversely spaced relative to said measurement path;

the conductor tracks on said second surface which form part of said first circuit are arranged for connecting conductor tracks in the first group with conductor tracks in the second group; and

the conductor track or tracks which form said at least one loop of said second circuit are carried by said first surface between said first and second groups.

37. An apparatus for use in a position sensor, comprising:

two layers of conductor tracks insulated, at least at any crossovers, by an insulator, the conductor tracks being arranged so as to define (i) a first circuit having at least two loops of opposite sense which extend along a measurement path, said loops being connected in series and being arranged so that signals generated in said at least two loops by a common electromagnetic field oppose each other; and

(ii) a second circuit having at least one loop which extends along said measurement path and which is superimposed on but electrically isolated from said at least two loops of said first circuit;

wherein an electromagnetic coupling area between the at least one loop of said second circuit and one or more loops of one sense of said first circuit is varied to oppose the effect of a variation in coupling between the at least one loop of said second circuit and a loop of the other sense of said first circuit caused by an arrangement of connector tracks to said second circuit.

38. An apparatus according to claim 37, wherein said two layers of conductor tracks are each carried on a respective side of a substantially planar insulator.

39. An apparatus according to claim 37, wherein said conductor tracks are formed by patterned conductor films formed on a substrate, and wherein an insulator film is provided at least at the crossover points between the conductive films forming said first and second circuits.

40. An apparatus according to claim 37, wherein said second circuit comprises a plurality of series connected concentric spiral windings, ends of which are connected to said connector tracks.

41. An apparatus according to claim 40, wherein the coupling area between the at least one loop of said second circuit and one or more loops of one sense of said first circuit is varied in the vicinity of the ends of the spiral windings.

42. An apparatus for use in a position encoder comprising:

an insulator base defining first and second surfaces which extend along a measurement path;

a first plurality of conductor tracks arranged on said first surface along said measurement path;

a second plurality of conductor tracks arranged on said second surface along said measurement path;

wherein the insulator base comprises a plurality of via holes for connecting the conductor tracks on the first surface to the conductor tracks on the second surface to define (i) a first circuit having at least two loops along the measurement path, said loops being connected in series and being arranged so that signals generated in said at least two loops by a common electromagnetic field oppose each other; and

(ii) a second circuit having at least one loop which extends along said measurement path and which is superimposed on but electrically isolated from said at least two loops of said first circuit;

wherein an electromagnetic coupling area between the at least one loop of said second circuit and one or more loops of one sense of said first circuit is varied to oppose the effect of a variation in coupling between the at least one loop of said second circuit and a loop of the other sense of said first circuit caused by an arrangement of connector tracks to said second circuit.

43. An apparatus for use in a position sensor comprising:

a first plurality of conductor tracks arranged in a first layer along a measurement path;

a second plurality of conductor tracks arranged in a second layer along said measurement path;

wherein the first and second pluralities of conductor tracks are superimposed on each other and connected together to define first and second circuits;

wherein the conductor tracks in said first layer which form part of said first circuit are arranged in first and second groups which are transversely spaced relative to said measurement path;

wherein the conductor tracks in said second layer which form part of said first circuit are arranged for connecting conductor tracks in the first group with conductor tracks in the second group; and

wherein the conductor track or tracks which form said second circuit are arranged in said first layer between said first and second groups of conductor tracks.

44. An apparatus according to claim 43, wherein said first and second layers of conductor tracks are carried on a respective side of a substantially planar insulator (15).

45. An apparatus according to claim 43, wherein said first and second layers of conductor tracks are formed on a respective side of a printed circuit board (15).

46. An apparatus according to claim 43, wherein said second circuit (131) comprises at least one outer loop and at least one inner loop, and wherein said inner and outer loops are wound in the opposite direction to each other.

47. An apparatus for use in a position sensor comprising:

an insulator base defining first and second surfaces which extend along a measurement path;

a first plurality of conductor tracks arranged on said first surface along said measurement path;

a second plurality of conductor tracks arranged on said second surface along said measurement path;

wherein the insulator base comprises a plurality of via holes for connecting the conductor tracks on the first surface to the conductor tracks on the second surface, the conductor tracks on said first surface and the conductor tracks on said second surface being arranged so that when connected together through said vias, they define first and second circuits;

wherein the conductor tracks on said first surface which form part of said first circuit are arranged in first and second groups which are transversely spaced relative to said measurement path;

wherein the conductor tracks on said second surface which form part of said first circuit are arranged for connecting conductor tracks in the first group with conductor tracks in the second group; and

wherein the conductor track or tracks which form said second circuit are carried by said first surface between said first and second groups.

48. An apparatus for use in a position encoder comprising:

a first plurality of conductor tracks arranged in a first layer along a measurement path;

a second plurality of conductor tracks arranged in a second layer along said measurement path;

wherein the first and second pluralities of conductor tracks are superimposed on each other to define first and second circuits;

wherein the conductor tracks in said first layer which form part of said first circuit are arranged in first and second groups which are transversely spaced relative to said measurement path;

the conductor tracks in said second layer which form part of said first circuit are arranged for connecting conductor tracks in the first group with conductor tracks in the second group; and

the conductor track or tracks which form said second circuit are arranged in said first layer between said first and second groups of conductor tracks.

49. An apparatus according to claim 48, wherein said first and second plurality of conductor tracks define a plurality of said first circuits, each having one or more loop portions extending along said measurement path, with the conductor tracks of each first circuit being separate from each other along the measurement path.

50. An apparatus according to claim 49, wherein each first circuit comprises at least two loops arranged along said measurement path, said loops being connected in series and being arranged so that signals generated in said at least two loops by a common electro-magnetic field oppose each other.