Peak strain detection linear displacement sensor system for smart structures

• US 6,588,282 B2
• Filed: 03/01/1999
• Issued: 07/08/2003
• Est. Priority Date: 03/04/1998
• Status: Expired due to Term

• Current Assignee: Lord Corporation (Parker-Hannifin Corporation)
• Original Assignee: MicroStrain, Inc. (Spectris PLC)
• Inventors: Arms, Steven W.
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): Davis, Octavia
• Application Number:
  US09/259,615
• Publication Number:
  US 20010054317A1
• Time in Patent Office: 1,590 Days
• Field of Search: 737/86, 737/68, 737/84, 738/19, 738/51
• US Class Current: 73/786
• CPC Class Codes: G01B 7/24 using change in magnetic properties

Abstract

The novel peak strain detection linear displacement sensor system for smart structures is designed to provide monitoring of the strain in structures and reporting their strain histories. The system comprises the use of micro miniature, high resolution, passive peak strain detector. A displacement sensor, such as a differential variable reluctance transducer, is used and the sliding core of the unit is constrained so that it shows the maximum movement in one direction. Once positioned and attached, mechanical movement of the core will always occur in response to structural deformation. The system comprises attachment devices and a body clamp and core extender and compressor, a housing, a spring loaded collar, a sensor core and a measuring unit.

Claims

1. A measuring device for measuring peak-displacement comprising a first component, a second component separate from said first component, a sensor sensitive to relative position of said first component with respect to said second component, and a constraint, wherein said constraint holds said first and said second components at position of peak relative displacement of said first component with respect to said second component.

2. The device as recited in claim 1, wherein power is not required for holding said first and paid second components at position of peak relative displacement of said first component with respect to said second component.

3. The device as recited in claim 1, wherein said constraint comprises an entrapment collar.

4. The device as recited in claim 3, wherein said constraint comprises a spring loaded entrapment collar.

5. The device as recited in claim 3, wherein said entrapment collar envelops said core and applies circumferential load to said core to constrain said core from sliding after force is removed.

6. The device as recited in claim 1, wherein said constraint is connected to said second component for holding peak deflection of said first component with respect to said second component.

7. The device as recited in claim 1, wherein said sensor comprises an inductive sensor or a capacitive sensor.

8. The device as recited in claim 7, wherein said sensor comprises a variable reluctance transducer.

9. The device as recited in claim 1, wherein said device can be reset for further peak measurement.

10. The device as recited in claim 1, wherein output of said sensor is used to provide a measurement of displacement or strain.

11. The device as recited in claim 10, wherein said measurement is for determining movement of the structure or damage to the structure being monitored.

12. The device as recited in claim 10, wherein the structure being measured is a building, a bridge, an aircraft, a landing gear, or a composite structure.

13. The device as recited in claim 1, wherein said displacement is a vibration.

14. The device as recited in claim 13, wherein said displacement sensor tracks peak amplitude of said vibration and keeps said peak amplitude while said structure continues to vibrate.

15. The device as recited in claim 1, further comprising:

a first attachment unit for connecting said first component to a structure at a first location,

a second attachment unit for connecting said second component to the structure at a second location, said second location displaced from said first location.

16. The device as recited in claim 15, wherein said sensor provides a measurement of peak relative displacement between said first attachment unit and said second attachment unit.

17. The device as recited in claim 15, wherein said first component can move with respect to said first attachment unit.

18. The device as recited in claim 17, wherein said first component comprises a member that is slidable with respect to said first attachment unit and with respect to said second component.

19. The device as recited in claim 18, wherein said member comprises a core that is slidable into or out of said second component.

20. The device as recited in claim 19, wherein said core has a core position within said second component, wherein said second component comprises a sensor sensitive to said core position within said second component.

21. The device as recited in claim 19, wherein said core is superelastic.

22. The device as recited in claim 19, wherein said core comprises a bumper for providing movement of said core in response to movement of said first attachment unit.

23. The device as recited in claim 22, wherein said first attachment unit further comprises a tube for providing movement of said first attachment unit to said bumper.

24. The device as recited in claim 15, wherein said constraint allows said first component to be forded out of or into said second component.

25. The device as recited in claim 24, wherein said force is provided by either an increase in spacing or a decrease in spacing between said first and said second attachment units.

26. The device as recited in claim 15, wherein said second component is connected to said second attachment unit, wherein said second component cannot move with respect to said second attachment unit.

27. The device as recited in claim 15, wherein said relative displacement is provided by either an increase in spacing or a decrease in spacing between said first and said second attachment units.

28. The device as recited in claim 15, wherein said first attachment unit and said second attachment unit are connected to said structure with fasteners.

29. The device as recited in claim 28, wherein said fasteners comprise screws or adhesive.

30. A method of measuring a displacement comprising the steps of:

a) attaching a first attachment unit to a structure at a first location;

b) attaching a second attachment unit to the structure at a second location, said second location displaced from said first location;

c) providing a passive peak-displacement sensor, said peak-displacement sensor comprising a first component and a second component separate from said first component, a sensor sensitive to relative position of said first component with respect to said second component, and a constraint, wherein said constraint holds said first and said second components at position of peak relative displacement of said first component with respect to said second component;

d) providing a relative displacement of said first attachment unit with respect to said second attachment unit; and

e) measuring peak displacement with said passive peak-displacement sensor.