Sensor devices for structural health monitoring

• US 20060170535A1
• Filed: 01/04/2006
• Published: 08/03/2006
• 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 7,986,218 B2
• Time in Patent Office: Days
• US Class Current: 340/10.410
• 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 device comprising:

an electrochemical cell that a) measures the potential difference between a reference electrode and an ion selective electrode and b) includes an electrolyte that provides a medium for movement of ions and maintains electrical connection between the reference electrode and the 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.

2. The device of claim 1 further including a permeable cementitious membrane that permits passage of an ion from outside the device to the electrolyte.

3. The device of claim 1 wherein the ion selective electrode is selective to an ion that facilitates corrosion of a metal.

4. The device of claim 1 wherein the electrolyte maintains a substantially constant pH.

5. The device of claim 1 wherein the transponder transmits a wireless signal through a portion of a structure that the device is embedded in.

6. The device of claim 5 wherein the structure comprises concrete and the electrochemical cell detects chloride ion concentration in the concrete.

7. The device of claim 1 wherein the sensor and transponder are passive.

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

9. 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.

10. The device of claim 1 wherein the microchip also stores a second unique number for the device that indicates when the electrochemical cell has detected a threshold potential level.

11. The device of claim 1 wherein the device is embedded in a structure and the electrochemical cell detects a parameter indicative of the health of the structure.

12. A system for reporting the health of a structure comprising concrete and a metal, the system comprising:

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

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 concrete indicating the parameter status when triggered by a wireless interrogation signal,

an encapsulation that seals internal components of the sensor from the surrounding structure,

a port that permits passage of an ion from outside the device to the sensor, and

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.

13. The system of claim 12 wherein each device does not contain a power source.

14. The system of claim 13 wherein the interrogator powers the device using the wireless interrogation signal.

15. The system of claim 12 wherein interrogator is in digital communication with a database that includes device identifications for each of the devices in the array.

16. The system of claim 15 wherein database comprises records that identify the locations of each device in the array.

17. The system of claim 12 wherein the sensor detects a level or state of a chemical species that is aggressive to the health of the structure.

18. The system of claim 12 wherein the interrogator is carried by a moving vehicle.

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

embedding a sensor device in the concrete before the concrete finishes curing, 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.

20. The method of claim 19 wherein the structure is a bridge or a portion of a bridge.

21. The method of claim 20 wherein the sensor is embedded in the concrete using a back filled core.

22. The method of claim 21 wherein the back filled core comprises a low porosity concrete.

23. The method of claim 19 wherein the interrogator is carried by a moving vehicle while probing the device.

24. The method of claim 19 wherein the interrogator is carried by a person while probing the device.

25. The method of claim 19 further comprising saving the parameter status for the device in a database.

26. The method of claim 19 further comprising compensating the sensed parameter status according to the temperature of the device.

27. The method of claim 19 wherein probing the device comprises powering the device.

28. The method of claim 19 wherein the wireless signal also indicates an identification for the device.