Torque and load monitoring using magnetic sensor arrays

• US 20090001974A1
• Filed: 06/12/2008
• Published: 01/01/2009
• Est. Priority Date: 06/12/2007
• Status: Active Grant

• Current Assignee: Jentek Sensors, Inc.
• Original Assignee: Jentek Sensors, Inc.
• Inventors: Denenberg, Scott A., Dunford, Todd M., Goldfine, Neil J., Grundy, David C., Schlicker, Darrell E., Washabaugh, Andrew P., Sheiretov, Yanko K., Walrath, Karen E.
• Granted Patent: US 8,222,897 B2
• Time in Patent Office: Days
• US Class Current: 324/209
• CPC Class Codes: G01L 1/125 by using magnetostrictive means magnetostrictive sensors H10N35/101
• CPC Class Codes: G01L 1/127 by using inductive means G01L1/122, G01L1/125 take precedence
• CPC Class Codes: G01L 3/102 involving magnetostrictive means magnetostrictive sensors H10N35/101
• CPC Class Codes: G01L 3/105 involving inductive means G01L3/102, G01L3/104 take precedence
• CPC Class Codes: G01L 5/164 using variations in inductance

Abstract

An apparatus for the nondestructive measurement of materials that includes at least two layers of electrical conductors. Within each layer, a meandering primary winding is used to create a magnetic field for interrogating a test material while sense elements or conducting loops within each meander provide a directional measurement of the test material condition. In successive layers extended portions of the meanders are rotated so that the sense elements provide material condition in different orientations without requiring movement of the test circuit or apparatus. In a bidirectional implementation the angle is 90° while in a quadridirectional implementation the relative angles are −45, 0, 45, and 90°. Multidirectional permeability measurements are used to assess the stress or torque on a component. These measurements are combined in a manner that removes temperature effects and hysteresis on the property measurements. This can be accomplished through a correction factor that accounts for the temperature dependence. After the corrections, the permeability measurement is then used to assess the local stresses and strains in the material of interest.

Claims

1. A test circuit comprising:

at least two primary windings, each primary winding in a respective layer and configured to impose magnetic flux in a test material when driven by an electric current, each primary winding having conducting segments with linear parallel extended portions, the extended portions in each layer positioned at an angle with respect to the extended portions in another layer; and

at least one sense element associated with each primary winding having conducting segments aligned parallel to extended portions of the associated primary winding to link magnetic flux, the at least one sense element having at least one feature selected to minimize the net linked magnetic flux from each non-associated primary winding.

2. The test circuit as claimed in claim 1 wherein the feature is position of a sense element center and the position is over a conducting segment of a non-associated primary winding.

3. The test circuit as claimed in claim 1 wherein the feature is sense element length and the length is an integral multiple of twice the distance between extended portions of the associated primary winding divided by the sine of the angle between extended portions in different layers.

4. The test circuit as claimed in claim 1 wherein the at least one sense element is centered between adjacent extended portions of the associated primary winding.

5. The test circuit as claimed in claim 1 wherein the sense elements are located in a same layer as the associated primary winding.

6. The test circuit as claimed in claim 1 wherein the angle between extended portions in two primary windings is 90°

.

7. The test circuit as claimed in claim 6 wherein the two primary windings are driven in series and the net dipole moment is zero.

8. The test circuit as claimed in claim 1 wherein a primary winding is in each of four layers.

9. The test circuit as claimed in claim 8 wherein the angles between extended portions in one layer to the other three layers is −

45°

, 45°

, and 90°

.

10. The test circuit as claimed in claim 1 further comprising:

inter-layer conductors at an end of segments in each layer.

49. The test circuit as claimed in claim 1 wherein the each primary winding has meandering conducting segments.

11. A test circuit comprising:

a primary winding in each of four layers to impose magnetic flux in a test material when driven by an electric current, each primary winding having conducting segments with linear parallel extended portions, the extended portions in each layer positioned at a first angle with respect to the extended portions in another layer, a first pair of primary windings being formed by orthogonal extended portions in two layers and a second pair of primary windings being formed by orthogonal extended portions in two other layers, the extended portions between pairs positioned at a second angle; and

at least one sense element associated with each primary winding having conducting segments aligned parallel to extended portions of the associated primary winding to link magnetic flux, the at least one sense element having at least one feature selected to minimize the net linked magnetic flux from each non-associated primary winding.

12. The test circuit as claimed in claim 11 wherein the feature is position of a sense element center and the position is over a conducting segment of a non-associated primary winding.

13. The test circuit as claimed in claim 11 wherein the feature is sense element length.

14. The test circuit as claimed in claim 13 wherein the length is an integral multiple of the distance between extended portions of the primary winding multiplied by 2√

2.

15. The test circuit as claimed in claim 11 wherein the second angle is 45°

.

16. The test circuit as claimed in claim 11 wherein the at least one sense element is centered between the adjacent extended portions of the associated primary winding.

17. The test circuit as claimed in claim 11 wherein the at least one sense element is located in a same layer as the associated primary winding.

18. A method for stress assessment comprising:

disposing a sensor proximate to a test material, the sensor having at least two drive windings and at least two sense elements, the drive windings connected in series for exciting a spatially periodic magnetic field of at least two periods when driven by an electric current, with the drive windings oriented in at least two different directions, positioned in at least two separate planes, and covering an overlapping area of the test material, the sense elements sensing a response to the test material, with each sense element positioned to measure a test material response primarily associated with one of the drive windings and not with the other drive windings;

converting the response of each sense element into a property estimate for the test material in at least two directions, the property estimate exhibiting hysteresis as an applied load varies the stress of the test material; and

correlating a property estimate to the stress of the test material in a first direction, with a property estimate in at least one second direction used to remove hysteresis effects on the property estimate in the first direction, the hysteresis effect determined by loading the test material to a known level and computing at least one correction factor that removes the hysteresis from the first direction.

19. The method as claimed in claim 18 further comprising:

the test material being a rotating cylinder;

the sensor having two pairs of orthogonal drive windings and sense elements, stationary, not in contact with the test material; and

the stress providing a measured load on the rotating cylinder.

20. The method as claimed in claim 19 wherein the measured load is the torque on the rotating cylinder.

21. The method as claimed in claim 19 wherein the measured load is an axial load on the rotating cylinder.

22. The method as claimed in claim 19 wherein the measured load is a bending load on the rotating cylinder.

23. The method as claimed in claim 18 wherein the stress in at least two directions is determined from at least three drive windings and at least three sense elements.

24. The method as claimed in claim 18 wherein the stress provides a measure of torque, bending and axial load on a spinning shaft in a drive system.

25. The method as claimed in claim 18 wherein the stress is measured in at least two directions on a ferrous metal structural member or a structural member coated with a ferrous metal, and the property is a magnetic permeability.

26. The method as claimed in claim 18 wherein sensing element measurements are made simultaneously.

27-48. -48. (canceled)