Displacement Measurement System and Method using Magnetic Encodings

• US 20110193552A1
• Filed: 02/10/2011
• Published: 08/11/2011
• Est. Priority Date: 02/11/2010
• Status: Active Grant

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Fulkerson, Kurt D., Sechi, Paolo G., Arns, Donald C. JR.
• Granted Patent: US 8,970,208 B2
• Time in Patent Office: Days
• 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 one or more 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;

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 from the signals a measurement associated with a performance of the rotating member.

2. The measurement system of claim 1, wherein the one or more bands includes a pair of spatially separated bands, 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.

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

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

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 member.

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 1, wherein the magnetizable material of each band is a magnetically hard layer integrally formed at the surface of the member.

10. The measurement system of claim 1, wherein the magnetizable material of each band comprises a magnetizable alloy strip attached to the surface of the member.

11. The measurement system of claim 1, wherein the processing electronics measures a rotational speed of the rotating member 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 member.

12. A measurement system, comprising:

a shaft rotating about an axis, the shaft 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;

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 and to compute therefrom torsion experienced by the shaft.

13. 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 generated signals while the shaft rotates and to measure, in response to the signals, vibration occurring in the rotating shaft.

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

providing one or more 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 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, a measurement associated with the performance of the rotating member.

15. The method of claim 14, wherein the one or more bands includes a pair of spatially separated bands, and wherein the dynamically computing, in response to the generated signals, a measurement associated with the performance of the member includes measuring an angular displacement of one of the spatially separated bands relative to the other of the spatially separated bands.

16. The method of claim 15, 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.

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

18. The method of claim 15, 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.

19. The method of claim 15, further comprising calibrating an initial relative displacement between the spatially separated bands while a predetermined torque is being applied to the member.

20. The method of claim 19, wherein the predetermined torque is zero load.

21. The method of claim 14, wherein the transitions have approximately a 1 mm spacing, and wherein a resolution for computing the angular displacement is at a sub-micron level.

22. The method of claim 14, 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.

23. The method of claim 14, 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.

24. The method of claim 14, 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.