Sensor devices for structural health monitoring

• US 20020154029A1
• Filed: 04/03/2002
• Published: 10/24/2002
• Est. Priority Date: 02/26/1999
• Status: Active Grant

• Current Assignee: Yasumi Capital, LLC (Intellectual Ventures LLC)
• Original Assignee: SRI International, Inc.
• Inventors: Priyantha, Namal, Huestis, David L., Bahr, Alfred J., Watters, David G., Jayaweera, Palitha
• Granted Patent: US 7,034,660 B2
• Time in Patent Office: Days
• US Class Current: 340/870.07
• CPC Class Codes: E01D 22/00 Methods or apparatus for repairing or strengthening existing bridges electrochemical desalination or re-alkalisation C04B41/00; Methods or apparatus for dismantling bridges
• CPC Class Codes: G01D 21/00 Measuring or testing not otherwise provided for
• CPC Class Codes: G01D 5/48 using wave or particle radiation means G01D5/26 takes precedence
• CPC Class Codes: G01K 3/04 in respect of time
• CPC Class Codes: G01K 5/483 using materials with a configuration memory, e.g. Ni-Ti alloys
• CPC Class Codes: G01M 5/0008 of bridges
• CPC Class Codes: G01M 5/0041 by determining deflection or stress
• CPC Class Codes: G01M 5/0083 by measuring variation of impedance, e.g. resistance, capacitance, induction
• CPC Class Codes: G01M 5/0091 by using electromagnetic excitation or detection
• CPC Class Codes: G01N 27/4035 Combination of a single ion-sensing electrode and a single reference electrode G01N27/406 and G01N27/413 take precedence
• CPC Class Codes: G06K 19/0717 the sensor being capable of sensing environmental conditions such as temperature history or pressure
• CPC Class Codes: H04Q 2209/47 using RFID associated with sensors
• CPC Class Codes: H04Q 2209/823 where the data is sent when the measured values exceed a threshold, e.g. sending an alarm
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

Described herein are wireless interrogation systems and methods that rely on a complementary sensing device and interrogator. The sensing device is disposed to measure a parameter indicative of the health of a structure. A sensor reading from the sensor indicates the level of a parameter being monitored or whether one or more particular physical or chemical events have taken place. Using wireless techniques, the interrogator probes the device to determine its identity and its current sensor reading. This often includes transmission of a wireless signal through portions of the structure. When activated, the device responds with a wireless signal that identifies the device and contains information about the parameter being measured or a particular sensor state corresponding to the parameter. The identity of the device allows it to be distinguished from a number of similar devices. Thus this invention finds particular usefulness in the context of an array of devices that can be probed by a wireless interrogation unit. In one embodiment, the devices are passive and derive power from the interrogation signal.

Claims

1. A sensor device comprising:

a sensor that detects a parameter indicative of the health of a structure comprising a metal;

a transponder in electrical communication with the sensor and that transmits a wireless signal through a portion of the structure indicating the parameter status when triggered by a wireless interrogation signal; and

an identification source in electrical communication with the transponder that uniquely identifies the device.

2. The device of claim 1 wherein the device does not contain a power source.

4. The device of claim 1 wherein the device is embedded in the structure.

5. The device of claim 1 wherein the sensor detects the level of a chemical that is aggressive to the health of the structure.

6. The device of claim 5 wherein the sensor detects the level of an ion that facilitates corrosion of the metal.

7. The device of claim 1 further comprising temperature compensation circuitry that alters a sensor reading according to temperature of the device.

8. The device of claim 1 wherein the identification source comprises a microchip that stores a unique number for the sensor device.

9. The device of claim 8 wherein the microchip also stores a second unique number for the device that indicates when the sensor has detected a threshold level for the parameter being sensed.

10. The device of claim 9 wherein the threshold corresponds to a chloride ion concentration.

11. The device of claim 1 wherein the transponder comprises:

a ferrite; and

at least one wire wound around the ferrite.

12. The device of claim 1 wherein the device includes a microchip that rectifies a signal provided to the transponder.

13. The device of claim 1 wherein the sensor comprises an electrochemical cell.

14. The device of claim 1 wherein the sensor detects one of humidity, temperature, and pressure.

15. The device of claim 1 further comprising a memory component that allows for recording an event detected by the sensor.

16. The device of claim 15 wherein the event is a threshold for the parameter.

17. The device of claim 1 further comprising an amplifier for increasing the strength of a received incident signal, a modulator for modifying the incident signal with information provided by the sensor, and an antenna or antennas for receiving and transmitting the incident signal.

18. The device of claim 1 wherein the device communicates information related to the parameter being detected using a bit stream inversion.

20. The device of claim 19 wherein the transponder transmits the wireless signal when triggered by a wireless interrogation signal provided by an interrogator.

21. The device of claim 19 wherein the structure comprises a metal.

22. The device of claim 21 wherein the sensor detects a parameter indicative of the health of the structure.

23. The device of claim 22 wherein the sensor detects a parameter indicative of the health of the metal.

24. The device of claim 23 wherein the sensor detects the presence of an ion that facilitates corrosion of the metal.

25. The device of claim 24 wherein the structure comprises concrete and the sensor detects chloride ion concentration in the concrete.

26. The device of claim 19 wherein the structure is included in a bridge.

27. The device of claim 19 wherein the sensor and transponder are passive.

28. The device of claim 19 wherein the sensor detects one of:

resistance of a metal element included in the structure, concentration of an ion found in the structure, pH in the structure, conductivity of a metal element included in the structure, and corrosion of a surrogate.

29. The device of claim 19 further comprising temperature compensation circuitry that alters a sensor reading according to temperature of the device.

30. The device of claim 19 wherein the identification source comprises a microchip that stores a unique number for the device.

31. The device of claim 30 wherein the microchip also stores a second unique number for the device that indicates when the sensor has detected a threshold level for the parameter being sensed.

32. The device of claim 31 wherein the threshold corresponds to a level of chloride ion concentration in the concrete.

33. The device of claim 1 wherein the transponder comprises:

a ferrite; and

a wire wound around the ferrite.

34. The device of claim 19 wherein the device includes a microchip that rectifies a signal provided to the transponder.

35. The device of claim 19 wherein the sensor comprises an electrochemical cell.

37. The device of claim 36 wherein the device includes a microchip that rectifies a wireless signal provided to the transponder.

38. The device of claim 36 further including a permeable cementitious membrane that permits passage of an ion from outside the device to the ion selective electrode.

39. The device of claim 36 wherein the ion is a halide.

40. The device of claim 39 wherein the halide is chloride.

41. The device of claim 36 wherein the ion selective electrode is selective to an ion that facilitates corrosion of a metal.

42. The device of claim 36 wherein the ion selective electrode is an AgCl electrode.

43. The device of claim 36 wherein the electrochemical cell measures the voltage difference between the ion selective electrode and a copper electrode.

44. The device of claim 36 wherein the transponder transmits a wireless signal through a portion of a structure that the device is embedded in.

45. The device of claim 44 wherein the structure comprises concrete and the electrochemical cell detects chloride ion concentration in the concrete.

46. The device of claim 36 wherein the sensor and transponder are passive.

47. The device of claim 36 further comprising temperature compensation circuitry that alters a sensor reading according to temperature of the device.

48. The device of claim 1 wherein the identification source comprises a microchip that stores a unique number for the device relative to other similar devices.

49. The device of claim 48 wherein the microchip also stores a second unique number for the device that indicates when the electrochemical cell has detected a threshold potential level.

50. The device of claim 49 wherein the threshold level corresponds to a level of chloride ion concentration.

51. The device of claim 36 wherein the transponder comprises:

a ferrite; and

a wire wound around the ferrite.

53. The device of claim 36 wherein the device is embedded in a structure and the electrochemical cell detects a parameter indicative of the health of the structure.

3. The device of claim I wherein the sensor detects one of:

the resistance of a metal element included in the structure, concentration of an ion found in the structure, pH in the structure, conductivity of a metal element included in the structure, and corrosion of a surrogate.

19. A device embedded in a structure comprising concrete, the device comprising:

a sensor embedded in the concrete that detects a parameter;

a transponder in electrical communication with the sensor and that transmits a wireless signal through a portion of the concrete indicating the parameter status; and

an identification source in electrical communication with the transponder that uniquely identifies the device.

36. A device comprising:

an electrochemical cell that measures the potential difference between a reference electrode and an ion selective electrode;

an identification source that uniquely identifies the device; and

a transponder in electrical communication with the electrochemical cell and in electrical communication with the identification source that transmits a wireless signal indicating the potential difference and information from the identification source.

54. A device for monitoring the health of a bridge comprising concrete and a metal, the device comprising:

a sensor, at least partially exposed to the concrete, that detects chloride ion presence in the concrete;

a transponder in electrical communication with the sensor and that transmits a wireless signal through the concrete indicating the chloride ion level when triggered by a wireless interrogation signal;

an identification source in electrical communication with the transponder that uniquely identifies the device; and

wherein the device is passive.

55. The device of claim 54 wherein the sensor comprises a passive electrochemical cell.

56. The device of claim 54 wherein the transponder comprises:

a ferrite; and

a wire wound around the ferrite.

57. The device of claim 54 wherein the device includes a microchip that rectifies a signal provided to the transponder.

58. The device of claim 54 further comprising an encapsulation layer comprising concrete that encapsulates at least the transponder and the identification source.

60. The device of claim 59 wherein each device does not contain a power source.

61. The system of claim 60 wherein the interrogator powers the device using the wireless interrogation signal.

62. The system of claim 61 wherein the device includes a microchip that rectifies a signal provided to the transponder.

63. The device of claim 59 wherein the sensor detects chloride ion concentration in the concrete.

64. The system of claim 59 wherein interrogator is in digital communication with a database that includes device identifications for each of the devices in the array.

65. The system of claim 64 wherein database further comprises records identifying the locations of each device in the array.

66. The device of claim 59 wherein the sensor detects a level or state of a chemical species that is aggressive to the health of the structure.

67. The device of claim 66 wherein the chemical species is aggressive to the metal.

68. The device of claim 67 wherein the threshold corresponds to a level of chloride in the concrete.

69. The method of claim 59 wherein the interrogator is carried by a moving vehicle.

70. The device of claim 59 wherein the sensor detects a level of humidity in the concrete.

71. The device of claim 59 wherein the sensor detects the level of humidity in the concrete during curing of the concrete.

59. A system for reporting the health of a bridge comprising concrete and a metal, the system comprising:

(a) an array of devices, each device embedded in the bridge and having;

a sensor that detects a parameter indicative of the health of the bridge,

a transponder in electrical communication with the sensor and that transmits a wireless signal through a portion of the concrete indicating the parameter status when triggered by a wireless interrogation signal,

an identification source in electrical communication with the transponder that uniquely identifies each device from the other devices, and

(b) an interrogator for externally probing a device in the array to determine the parameter status, wherein the interrogator is designed or configured to read the parameter status by (i) providing the wireless interrogation signal to the transponder and (ii) receiving a wireless response from the device.

72. A method for monitoring the health of a structure comprising concrete and a metal, the method comprising:

embedding a sensor device in the concrete, the sensor device comprising a sensor that detects a parameter indicative of the health of the structure, an identification source that can distinguish the device from the other similar devices, and a transponder;

detecting a level of the parameter using the sensor;

probing the device with an interrogator that produces a wireless signal that transmits through a portion of the concrete; and

returning a wireless signal from the device through a portion of the concrete, wherein the return wireless signal indicates the parameter status.

73. The method of claim 72 wherein the structure is a bridge or a portion of a bridge.

74. The method of claim 73 wherein the structure is a bridge deck.

75. The method of claim 72 wherein the wireless signal also indicates an identification for the device.

76. The method of claim 72 wherein the interrogator is carried by a moving vehicle while probing the device.

77. The method of claim 72 wherein the interrogator is carried by a person while probing the device.

78. The method of claim 72 further comprising saving the parameter status for the device in memory.

79. The method of claim 78 further comprising saving the parameter status for the device in a database.

80. The method of claim 72 further comprising compensating the sensed parameter status according to the temperature of the device.

81. The method of claim 72 wherein probing the device comprises powering the device.

82. The method of claim 72 wherein probing the device with the interrogator comprises transmitting a wireless probe signal to the device and receiving a wireless device signal from the device.

83. The method of claim 72 wherein the device is embedded before the concrete finishes curing.