Displacement measurement system and method using magnetic encodings

• US 8,970,208 B2
• Filed: 02/10/2011
• Issued: 03/03/2015
• Est. Priority Date: 02/11/2010
• Status: Active Grant

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Fulkerson, Kurt D., Arns, Donald C. Jr., Sechi, Paolo G.
• Primary Examiner(s): LEDYNH, BOT L
• Application Number:
  US13/024,778
• Publication Number:
  US 20110193552A1
• Time in Patent Office: 1,482 Days
• Field of Search: 324/207.25
• US Class Current: 324/207.25
• CPC Class Codes: G01D 2205/80 Manufacturing details of magnetic targets for magnetic encoders
• CPC Class Codes: G01L 3/104 involving permanent magnets
• CPC Class Codes: G01L 3/109 involving measuring phase difference of two signals or pulse trains
• CPC Class Codes: G01P 3/487 delivered by rotating magnets

Abstract

A measurement system includes a rotating member configured to transfer mechanical energy to a point of use. The member has at a surface thereof one or more circumferentially oriented bands of magnetizable material. Each band has a magnetic pattern comprised of a plurality of transitions magnetically recorded in the magnetizable material of that band. A magnetic-field sensor is disposed sufficiently near each band of magnetizable material to sense a magnetic pattern recorded in that band as the member rotates. Each magnetic-field sensor generates signals in response to the magnetic pattern sensed by that magnetic-field sensor. Processing electronics is in communication with each magnetic-field sensor to receive the signals generated by that magnetic-field sensor while the member rotates and to dynamically compute from the signals a measurement associated with a performance of the rotating member.

Claims

1. A measurement system, comprising:

a rotating member configured to transfer mechanical energy to a point of use, the member having at a surface thereof a pair of spatially separated, circumferentially oriented bands of magnetizable material, each band having a magnetic pattern comprised of a plurality of transitions magnetically recorded in the magnetizable material of that band, the transitions having approximately a 1 mm spacing;

a magnetic-field sensor being disposed sufficiently near each band of magnetizable material to sense the magnetic pattern recorded in that band as the member rotates, each magnetic-field sensor generating signals in response to the magnetic pattern sensed by that magnetic-field sensor; and

processing electronics in communication with each magnetic-field sensor to receive the signals generated by that magnetic-field sensor while the member rotates and to dynamically compute, in response to the signals generated by the magnetic-field sensors sensing the magnetic patterns recorded in the spatially separated bands, an angular displacement of one of the spatially separated bands relative to the other of the spatially separated bands,

wherein a resolution for computing the angular displacement is at a sub-micron level.

2. A measurement system, comprising:

a shaft rotating about an axis, the shaft having a surface and a pair of spatially separated circumferentially oriented bands of magnetizable material directly on the surface of the shaft, each band having a magnetic pattern comprised of a plurality of transitions magnetically recorded in the magnetizable material of that band;

a magnetic-field sensor being disposed sufficiently near each band of magnetizable material to sense the magnetic pattern recorded in that band as the shaft rotates, each magnetic-field sensor generating signals in response to the magnetic pattern sensed by that magnetic-field sensor; and

processing electronics in communication with each magnetic-field sensor to receive the signals generated by that magnetic-field sensor while the shaft rotates, the processing electronics measuring, in response to the signals generated by the magnetic-field sensors, an angular displacement of one of the spatially separated bands relative to the other of the spatially separated bands, and computing torsion experienced by the shaft from the measured angular displacement.

3. The measurement system of claim 2, wherein the processing electronics dynamically computes, while the shaft rotates, a torque measurement in response to the measured angular displacement and other parameters associated with the rotating shaft.

4. The measurement system of claim 2, wherein the processing electronics computes multiple torque measurements during each complete revolution of the shaft.

5. The measurement system of claim 2, wherein the processing electronics measures the angular displacement between the spatially separated bands by computing an inverse sum of the square of difference between the different signals generated by sensing the spatially separated bands.

6. The measurement system of claim 2, further comprising a calibration system determining an initial relative displacement between the spatially separated bands with a predetermined torque applied to the shaft.

7. The measurement system of claim 6, wherein the predetermined torque is zero load.

8. The measurement system of claim 2, wherein the transitions have approximately a 1 mm spacing, and wherein a resolution for computing the angular displacement is at a sub-micron level.

9. The measurement system of claim 2, wherein the magnetizable material of each band is a magnetically hard layer integrally formed at the surface of the shaft.

10. The measurement system of claim 2, wherein the magnetizable material of each band comprises a magnetizable alloy strip attached to the surface of the shaft.

11. The measurement system of claim 2, wherein the processing electronics measures a rotational speed of the rotating shaft from signals produced by sensing the magnetic pattern of one band of the one or more bands and, in response to the rotational speed, computes frequency and phase information of any vibration being impressed upon the rotating shaft.

12. A measurement system, comprising:

a shaft rotating about an axis, the shaft having at a surface thereof a circumferentially oriented band of magnetizable material, the band having a magnetic pattern comprised of a plurality of transitions magnetically recorded in the magnetizable material;

a magnetic-field sensor being disposed sufficiently near the band of magnetizable material to sense the magnetic pattern as the shaft rotates, the magnetic-field sensor generating signals in response to the magnetic pattern; and

processing electronics in communication with the magnetic-field sensor to receive the signals generated by the magnetic-field sensor while the shaft rotates, the processing electronics measuring vibration occurring in the rotating shaft from the received signals generated by the magnetic-field sensor.

22. The measurement system of claim 12, wherein the band is a first band, and the shaft has, at the surface of the shaft, a second, circumferentially oriented band of magnetizable material spatially separated from the first band, and further comprising a second magnetic-field sensor being disposed sufficiently near the second band of magnetizable material to sense the magnetic pattern as the shaft rotates, and

wherein the processing electronics measures, in response to the signals generated by the magnetic-field sensors sensing the magnetic patterns recorded in the spatially separated bands, an angular displacement of one of the spatially separated bands relative to the other of the spatially separated bands.

23. The measurement system of claim 22, wherein the processing electronics dynamically computes, while the shaft rotates, a torque measurement in response to the measured angular displacement and other parameters associated with the rotating shaft.

24. The measurement system of claim 22, wherein the processing electronics computes multiple torque measurements during each complete revolution of the shaft.

25. The measurement system of claim 22, wherein the processing electronics measures the angular displacement between the spatially separated bands by computing an inverse sum of the square of difference between the different signals generated by sensing the spatially separated bands.

26. The measurement system of claim 22, further comprising a calibration system determining an initial relative displacement between the spatially separated bands with a predetermined torque applied to the shaft.

27. The measurement system of claim 26, wherein the predetermined torque is zero load.

28. The measurement system of claim 22, wherein the transitions have approximately a 1 mm spacing, and wherein a resolution for computing the angular displacement is at a sub-micron level.

29. The measurement system of claim 12, wherein the magnetizable material of the band is a magnetically hard layer integrally formed at the surface of the shaft.

30. The measurement system of claim 12, wherein the magnetizable material of the band comprises a magnetizable alloy strip attached to the surface of the shaft.

31. The measurement system of claim 12, wherein the processing electronics measures a rotational speed of the rotating shaft from signals produced by sensing the magnetic pattern of the band and, in response to the rotational speed, computes frequency and phase information of the vibration in the rotating shaft.

13. A method for measuring performance of a rotating member, comprising:

providing a pair of spatially separated bands of magnetizable material at a surface of a rotatable member, each of the one or more bands having a magnetic pattern comprised of a plurality of transitions with approximately a 1 mm spacing magnetically recorded in the magnetizable material of that band;

rotating the member to transfer mechanical energy to a point of use;

sensing the magnetic pattern recorded in each of the one or more bands of magnetizable material as the member rotates;

generating signals in response to each sensed magnetic pattern;

dynamically computing, in response to the generated signals, an angular displacement of one of the spatially separated bands relative to the other of the spatially separated bands at a sub-micron level resolution.

14. The method of claim 13, further comprising dynamically computing, while the member rotates, a torque measurement in response to the measured angular displacement and other parameters associated with the rotating member.

15. The method of claim 13, further comprising dynamically computing, while the member rotates, multiple torque measurements during each complete revolution of the member.

16. The method of claim 13, wherein measuring the angular displacement between the spatially separated bands includes computing an inverse sum of the square of difference between the signals generated from each of the bands.

17. The method of claim 13, further comprising calibrating an initial relative displacement between the spatially separated bands while a predetermined torque is being applied to the member.

18. The method of claim 17, wherein the predetermined torque is zero load.

19. The method of claim 13, wherein providing the one or more bands of magnetizable material at a surface of a rotatable member includes integrally forming a magnetically hard layer at the surface of the member and magnetically recording a magnetic pattern in each band in the magnetically hard layer.

20. The method of claim 13, wherein providing the one or more bands of magnetizable material at a surface of a rotatable member includes magnetically recording a magnetic pattern into one or more alloy strips and attaching each magnetizable alloy strip to the surface of the member.

21. The method of claim 13, further comprising computing frequency and phase information of any vibration being impressed upon the rotating member from signals produced by sensing the magnetic pattern of one band of the one or more bands.