Self-compensating position sensor

• US 6,807,875 B2
• Filed: 12/01/2000
• Issued: 10/26/2004
• Est. Priority Date: 12/01/2000
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Lebrun, Ivan P., Ohnesorge, David H.
• Primary Examiner(s): Noland, Thomas P.
• Application Number:
  US09/727,737
• Publication Number:
  US 20020066312A1
• Time in Patent Office: 1,425 Days
• Field of Search: 738/659, 731/68, 738/661, 137/553-554, 137/556, 116/277, 324/706
• US Class Current: 73/865.9
• CPC Class Codes: F15B 13/0402 for linearly sliding valves, e.g. spool valves
• CPC Class Codes: F15B 2013/0409 Position sensing or feedback of the valve member
• CPC Class Codes: F16K 37/0041 for measuring valve parameters F16K37/0033 takes precedence
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01B 7/16 for measuring the deformation in a solid, e.g. by resistance strain gauge
• CPC Class Codes: G01D 3/036 on measuring arrangements themselves
• CPC Class Codes: Y10T 137/8242 Electrical

Abstract

A position sensor and a method for sensing a position of a moveable member includes at least first and second deflectable members arranged so as to allow the moveable member to pass therebetween and cause the at least first and second moveable members to deflect in proportion to the position of the moveable member relative to the first and second deflectable members. In one example of the present invention, the deflectable members are cantilever-mounted members extending in generally the same direction. The amount of resultant deflection is measured by any suitable means. For example, each deflectable member may have a Wheatstone bridge provided thereon acting as a strain gauge in a known manner, such that the strain detected is proportional to the amount of deflection. In a particular example of the present invention, some of the elements of a first Wheatstone bridge are provided on the first deflectable member and some are provided on the second deflectable member. Likewise, some of the elements of a second Wheatstone bridge are provide on the first deflectable member and some are provided on the second. This desirably provides matched redundancy as well as compensation for spurious lateral movement of the moveable member.

Claims

1. A sensor for sensing the position a movable member, comprising:

first and second spaced apart and deflectable members, the movable member being movable between said first and second deflectable members so that said first and second deflectable members are laterally deflectable by the movable member in correspondence with a movement of the movable member, such that said first and second deflectable members deflect in opposite lateral directions and an amount of lateral deflection by both deflectable members increases the further the movable member is moved in between the first and second deflectable members, said first and second deflectable members each being arranged to create a deflection-dependent effect based on movement of the movable member; and

a deflection determining device constructed and arranged to generate a signal based on the deflection-dependent effects created by deflection of said first and second deflectable members, said signal being proportional to a position of the movable member, such that a combination of the deflection-dependent effect created by deflection of said first deflectable member and the deflection-dependent effect created by deflection of said second deflectable member indicates position of said movable member.

2. The sensor according to claim 1, wherein said deflection determining device comprises first and second piezo-resistive Wheatstone bridges, said first and second Wheatstone bridges each including electrically resistive elements, some of said resistive elements of said first Wheatstone bridge and some of said resistive elements of said second Wheatstone bridge being provided on said first deflectable member, and some of said resistive elements of said first Wheatstone bridge and some of said resistive elements of said second Wheatstone bridge being provided on said second deflectable member.

3. The sensor according to claim 2, wherein said first and second Wheatstone bridges each include first, second, third, and fourth resistive elements, wherein:

said first and second resistive elements of said first Wheatstone bridge are provided on a side of said first deflectable member facing the movable member;

said third and fourth resistive elements of said first Wheatstone bridge are provided on a side of said second deflectable member facing away from the movable member;

said first and second resistive elements of said second Wheatstone bridge are provided on a side of said first deflectable member facing away from the movable member; and

said third and fourth resistive elements of said second Wheatstone bridge are provide on a side of said second deflectable member facing the movable member.

4. The sensor according to claim 3, wherein said first and second Wheatstone bridges each include:

a voltage input electrically between said first and fourth resistive elements;

a ground electrically between said second and third resistive elements;

a first output electrically between said first and third resistive elements; and

a second output electrically between said second and fourth resistive elements.

5. The sensor according to claim 4, said deflection determining device comprising temperature-sensitive fifth resistive elements connected to said voltage input of said first Wheatstone bridge and to said voltage input of said second Wheatstone bridge, respectively.

6. The sensor according to claim 4, wherein at least one of said first, second, third, and fourth resistive elements of said first and second Wheatstone bridges has a resistance of 8 k ohms.

7. The sensor according to claim 4, the deflection determining device comprising a resistive temperature detector.

8. The sensor according to claim 1, wherein said deflection determining device comprises a converting mechanism constructed and arranged to convert said signal proportional to a position of the movable member into a position value.

9. The sensor according to claim 1, wherein said first and second deflectable members extend on either side of an axis, the movable member being movable along the same axis.

10. The sensor according to claim 1, wherein said deflection determining device comprises a single piezo-resistive Wheatstone bridge comprising resistive elements, some of which are provided on said first deflectable member and some of which are provided on said second deflectable member.

11. The sensor according to claim 1, wherein said deflection determining device comprises first and second piezo-resistive Wheatstone bridges each including first and second pluralities of resistive elements, respectively, wherein said first plurality of resistive elements is provided on said first deflectable member and second plurality of resistive elements is provided on said second deflectable member.

12. A sensor for sensing the position of a movable member, comprising:

first and second spaced apart and deflectable members, the movable member being movable between said first and second deflectable members so that said first and second deflectable members are deflectable by the movable member in correspondence with a movement of the movable member, said first and second deflectable members each being arranged to create a deflection-dependent effect based on movement of the movable member; and

a deflection determining device constructed and arranged to generate a signal based on the deflection-dependent effects created by deflection of said first and second deflectable members, said signal being proportional to a position of the movable member, such that a combination of the deflection-dependent effect created by deflection of said first deflectable member and the deflection-dependent effect created by deflection of said second deflectable member indicates position of said movable member,

wherein said first and second deflectable members are cantilever-mounted members, each having a fixed proximal end and a free distal end.

13. The sensor according to claim 12, wherein at least one of said first and second deflectable members has a first width at said proximal end, a second width narrower than said first width at said distal end, and an intermediate region having a width concavely decreasing from said first width to said second width located between said proximal end and said distal end.

14. The sensor according to claim 13, wherein said intermediate width has a continuously decreasing width.

15. The sensor according to claim 13, wherein said intermediate region has a stepwise decreasing width.

16. The sensor according to claim 13, wherein said first and second deflectable members each have a first width at said proximal end, a second width narrower than said first width at said distal end, and an intermediate region having a width decreasing from said first width to said second width located between said proximal end and said distal end.

17. The sensor according to claim 16, wherein said intermediate width has a continuously decreasing width.

18. The sensor according to claim 16, wherein said intermediate region has a stepwise decreasing width.

19. The sensor according to claim 13, wherein at least one of said first and second deflectable members comprises a metal substrate having a ceramic coating.

20. The sensor according to claim 13, wherein said deflection determining device comprises first and second piezo-resistive Wheatstone bridges each including first, second, third, and fourth resistive elements, wherein:

said first and second resistive elements of said first Wheatstone bridge are provided on a side of said first deflectable member facing the movable member in said intermediate region;

said third and fourth resistive elements of said first Wheatstone bridge are provided on a side of said second deflectable member facing away from the movable member in said intermediate region;

said first and second resistive elements of said second Wheatstone bridge are provided on a side of said first deflectable member facing away from the movable member in said intermediate region; and

said third and fourth resistive elements of said second Wheatstone bridge are provide on a side of said second deflectable member facing the movable member in said intermediate region.

21. A sensor for sensing the position of a movable member, comprising:

first and second spaced apart and deflectable members, the movable member being movable between said first and second deflectable members so that said first and second deflectable members are deflectable by the movable member in correspondence with a movement of the movable member, said first and second deflectable members each being arranged to create a deflection-dependent effect based on movement of the movable member; and

a deflection determining device constructed and arranged to generate a signal based on the deflection-dependent effects created by deflection of said first and second deflectable members, said signal being proportional to a position of the movable member, such that a combination of the deflection-dependent effect created by deflection of said first deflectable member and the deflection-dependent effect created by deflection of said second deflectable member indicates position of said movable member,

wherein the movable member is connected to a valve, such that a position of the movable member corresponds to a position of the valve.

22. A valve position sensor comprising:

a linearly movable member associated with a valve spool;

first and second deflectable members mounted offset from a line along which said movable member moves, said movable member being movable between said first and second deflectable members so that said first and second deflectable members are laterally deflected in opposite lateral directions in correspondence with a movement of said movable member, such that an amount of lateral deflection by both deflectable members increases the further the movable member is moved in between said first and second deflectable members;

a deflection determining device constructed and arranged to output a signal based on a deflection of said first and second deflectable members, said signal being proportional to a position of the movable member and said valve spool.

23. The sensor according to claim 22, wherein said deflection determining device comprises first and second piezo-resistive Wheatstone bridges, said first and second Wheatstone bridges each including electrically resistive elements, some of said resistive elements of said first Wheatstone bridge and some of said resistive elements of said second Wheatstone bridge being provided on said first deflectable member, and some of said resistive elements of said first Wheatstone bridge and some of said resistive elements of said second Wheatstone bridge being provided on said second deflectable member.

24. The sensor according to claim 23, wherein said first and second Wheatstone bridges each include first, second, third, and fourth resistive elements, wherein:

said first and second resistive elements of said first Wheatstone bridge are provided on a side of said first deflectable member facing the movable member;

said third and fourth resistive elements of said first Wheatstone bridge are provided on a side of said second deflectable member facing away from the movable member;

said first and second resistive elements of said second Wheatstone bridge are provided on a side of said first deflectable member facing away from the movable member; and

said third and fourth resistive elements of said second Wheatstone bridge are provide on a side of said second deflectable member facing the movable member.

25. The sensor according to claim 23, wherein said first and second Wheatstone bridges each include:

a voltage input electrically between said first and fourth resistive elements;

a ground electrically between said second and third resistive elements;

a first output electrically between said first and third resistive elements; and

a second output electrically between said second and fourth resistive elements.

26. The sensor according to claim 25, said deflection determining device comprising temperature-sensitive fifth resistive elements connected to said voltage input of said first Wheatstone bridge and to said voltage input of said second Wheatstone bridge, respectively.

27. The sensor according to claim 25, wherein at least one of said first, second, third, and fourth resistive elements of said first and second Wheatstone bridges has a resistance of 8 k ohms.

28. The sensor according to claim 25, the deflection determining device comprising a resistive temperature detector.

29. The sensor according to claim 22, wherein said deflection determining device comprises a converting mechanism constructed and arranged to convert said signal proportional to a position of the movable member into a position value.

30. The sensor according to claim 22, wherein the movable member is connected to a valve, such that a position of the movable member corresponds to a position of the valve.

31. The sensor according to claim 22, wherein said first and second deflectable members extend on either side of an axis, the movable member being movable along the same axis.

32. The sensor according to claim 22, wherein said movable member is part of the valve spool.

33. The sensor according to claim 22, wherein said movable member is tapered.

34. The sensor according to claim 33, wherein said movable member is conical.

35. The sensor according to claim 22, wherein said deflection determining device comprises a single piezo-resistive Wheatstone bridge comprising resistive elements, some of which are provided on said first deflectable member and some of which are provided on said second deflectable member.

36. The sensor according to claim 22, wherein said deflection determining device comprises first and second piezo-resistive Wheatstone bridges each including first and second pluralities of resistive elements, respectively, wherein said first plurality of resistive elements is provided on said first deflectable member and second plurality of resistive elements is provided on said second deflectable member.

37. A valve position sensor comprising:

a linearly movable member associated with a valve spool;

first and second deflectable members mounted offset from a line along which said movable member moves, said movable member being movable between said first and second deflectable members so as to be deflected in correspondence with a movement of said movable member;

a deflection determining device constructed and arranged to output a signal based on a deflection of said first and second deflectable members, said signal being proportional to a position of the movable member and said valve spool,

wherein said first and second deflectable members are cantilever-mounted members, each having a fixed proximal end and a free distal end.

38. The sensor according to claim 37, wherein at least one of said first and second deflectable members has a first width at said proximal end, a second width narrower than said first width at said distal end, and an intermediate region having a width decreasing from said first width to said second width located between said proximal end and said distal end.

39. The sensor according to claim 38, wherein said intermediate width has a continuously decreasing width.

40. The sensor according to claim 38, wherein said intermediate region has a stepwise decreasing width.

41. The sensor according to claim 38, wherein said first and second deflectable members each have a first width at said proximal end, a second width narrower than said first width at said distal end, and an intermediate region having a width decreasing from said first width to said second width located between said proximal end and said distal end.

42. The sensor according to claim 41, wherein said intermediate width has a continuously decreasing width.

43. The sensor according to claim 41, wherein said intermediate region has a stepwise decreasing width.

44. The sensor according to claim 41, wherein said deflection determining device comprises first and second piezo-resistive Wheatstone bridges each including first, second, third, and fourth resistive elements, wherein:

said first and second resistive elements of said first Wheatstone bridge are provided on a side of said first deflectable member facing the movable member in said intermediate region;

said third and fourth resistive elements of said first Wheatstone bridge are provided on a side of said second deflectable member facing away from the movable member in said intermediate region;

said first and second resistive elements of said second Wheatstone bridge are provided on a side of said first deflectable member facing away from the movable member in said intermediate region; and

said third and fourth resistive elements of said second Wheatstone bridge are provide on a side of said second deflectable member facing the movable member in said intermediate region.

45. The sensor according to claim 38, wherein at least one of said first and second deflectable members comprises a metal substrate having a ceramic coating.

46. A method for detecting a position of a movable member, comprising:

passing the movable member between first and second deflectable members so as to laterally deflect the first and second deflectable members, such that said first and second deflection members deflect in opposite lateral directions and an amount of lateral deflection by both the first and second deflectable members increases the further the movable member passes in between the deflectable members, thereby creating a deflection-dependent effect for each of the first and second deflectable members; and

determining a position of the movable member according to a combination of the deflection-dependent effect for the first deflectable member and the deflection-dependent effect for the second deflectable member.

47. The method according to claim 46, wherein determining a position of the movable member comprises:

providing first and second resistive elements of a first Wheatstone bridge on a side of the first deflectable member facing the movable member;

providing third and fourth resistive elements of the first Wheatstone bridge on a side of the second deflectable member facing away from the movable member;

providing first and second resistive elements of a second Wheatstone bridge on a side of the first deflectable member facing away from the movable member;

providing third and fourth resistive elements of the second Wheatstone bridge are provide on a side of the second deflectable member facing the movable member; and

determining a deflection of the first and second deflectable members using signals generated by the first and second Wheatstone bridges; and

determining a position of the movable member based on the detected deflection of the first and second deflectable members.

48. The method according to claim 46, wherein the first and second deflectable members comprise a metal substrate having a ceramic coating.

49. A method for detecting a position of a movable member, comprising:

passing the movable member between first and second deflectable members so as to deflect the first and second deflectable members, thereby creating a deflection-dependent effect for each of the first and second deflectable members; and

determining a position of the movable member according to a combination of the deflection-dependent effect for the first deflectable member and the deflection-dependent effect for the second deflectable member,

wherein the first and second deflectable members are cantilever-mounted members, each having a fixed proximal end and a free distal end.

50. The method according to claim 49, wherein each of the first and second deflectable members has a first width at the proximal end, a second width narrower than the first width at the distal end, and an intermediate region having a width decreasing from the first width to the second width located between the proximal end and the distal end.

51. The method according to claim 50, wherein the intermediate width has a continuously decreasing width.

52. The method according to claim 50, wherein the intermediate region has a stepwise decreasing width.

53. The method according to claim 50, wherein the first and second deflectable members each have a first width at the proximal end, a second width narrower than the first width at the distal end, and an intermediate region having a width decreasing from the first width to the second width located between the proximal end and the distal end.

54. The method according to claim 50, wherein determining a position of the movable member comprises:

providing first and second resistive elements of a first Wheatstone bridge on a side of the first deflectable member facing the movable member in the intermediate region;

providing third and fourth resistive elements of the first Wheatstone bridge on a side of the second deflectable member facing away from the movable member in the intermediate region;

providing first and second resistive elements of a second Wheatstone bridge on a side of the first deflectable member facing away from the movable member in the intermediate region;

providing third and fourth resistive elements of the second Wheatstone bridge are provide on a side of the second deflectable member facing the movable member in the intermediate region; and

determining a deflection of the first and second deflectable members using signals generated by the first and second Wheatstone bridges; and

determining a position of the movable member based on the detected deflection of the first and second deflectable members.

55. A position sensor comprising:

a movable assembly including first and second spaced apart and deflectable members;

a fixed member disposed between said first and second deflectable members, said first and second deflectable members being deflectable by the fixed member in correspondence with a movement of the movable assembly relative to the fixed member, said first and second deflectable members each being arranged to create a deflection-dependent effect based on movement of the movable assembly relative to the fixed member; and

a deflection determining device constructed and arranged to output a signal based on a deflection of said first and second deflectable members, said signal being proportional to a position of the movable assembly such that a combination of the deflection-dependent effect created by deflection of said first deflectable member and the deflection-dependent effect created by deflection of said second deflectable member indicates position of the movable assembly relative to the fixed member,

wherein said first and second deflectable members are cantilever-mounted members, each having a fixed proximal end and a free distal end.