Array of RFID tags with sensing capability

• US 9,317,795 B2
• Filed: 11/02/2011
• Issued: 04/19/2016
• Est. Priority Date: 11/02/2011
• Status: Active Grant

• Current Assignee: Avery Dennison Retail Information Services LLC (Avery Dennison Corporation)
• Original Assignee: Avery Dennison Corporation
• Inventors: Forster, Ian James
• Primary Examiner(s): Bee, Andrew
• Assistant Examiner(s): Mahase, Pameshanand
• Application Number:
  US13/287,235
• Publication Number:
  US 20130106578A1
• Time in Patent Office: 1,630 Days
• Field of Search: 340/10.4
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/066 in a matrix array
• CPC Class Codes: A61B 5/447 specially adapted for aiding the prevention of ulcer or pressure sore development, i.e. before the ulcer or sore has developed
• CPC Class Codes: A61B 5/6891 Furniture
• CPC Class Codes: G06K 19/0717 the sensor being capable of sensing environmental conditions such as temperature history or pressure

Abstract

An RFID sensing system and method. An array of sensing elements is disposed on a surface of a mat, wherein each sensing element includes an RFID microchip, an antenna operatively coupled to the microchip, and a pressure-sensitive material disposed on at least the antenna. An RFID reader is provided for interrogating the array of sensing elements. An antenna operatively coupled to the reader communicates with each sensing element disposed on the mat. Each sensing element in the array, in response to an interrogation signal, transmits a signal to the reader via the coupled antenna when a subject placed on the mat compresses the section of pressure-sensitive material for the sensing element.

Claims

1. An RFID sensing system comprising:

an array of sensing elements disposed on a surface of a mat, wherein each sensing element includes an RFID microchip, an antenna operatively coupled to the microchip, and a pressure-sensitive material disposed on at least the antenna;

an RFID reader for interrogating the array of sensing elements;

an antenna operatively coupled to the reader for communicating with each sensing element disposed on the mat;

wherein each sensing element in the array, in response to an interrogation signal, transmits a signal to the reader via the coupled antenna when a subject placed on the mat compresses the pressure-sensitive material for the sensing element,

wherein the transmitted signal corresponds to the change in pressure attributable to the placement of the subject on the mat,

wherein the reader determines the change in pressure by altering the output power and determining the power level at which an identifier ID associated with a sensing element starts to read.

2. The RFID sensing system of claim 1, wherein the pressure-sensitive material comprises a conductive foam.

3. The RFID sensing system of claim 2, further comprising a pressure-sensitive overlaminate material separating the sensing element antenna from the conductive foam.

4. The RFID sensing system of claim 1, wherein the pressure-sensitive material comprises a quantum tunneling composite.

5. The RFID sensing system of claim 1, wherein the antenna operatively coupled to the reader comprises a near field antenna.

6. The RFID sensing system of claim 1, wherein the antenna operatively coupled to the reader comprises a far field antenna.

7. The RFID sensing system of claim 2, wherein the resistance of the conductive foam decreases as the foam is compressed.

8. The RFID sensing system of claim 2, wherein the conductive foam is coated with a plurality of conductive particles.

9. The RFID sensing system of claim 2, wherein the conductive foam is coated with carbon.

10. The RFID sensing system of claim 1, wherein the antenna operatively coupled to the microchip comprises a structure operating at an ultra high frequency (UHF).

11. The RFID sensing system of claim 1, wherein the signal transmitted by each sensing element represents a change in sensitivity for the sensing element resulting from absorption of energy at an operating frequency of the sensing element caused by compression of the pressure-sensitive material.

12. An RFID sensing system comprising:

an array of sensing elements disposed on a surface of a mat, wherein each sensing element includes an RFID microchip, an antenna operatively coupled to the microchip, and a pressure-sensitive material disposed on at least the antenna;

an RFID reader for interrogating the array of sensing elements;

a transmission line coupled to a port of the reader and to each element in the array of sensing elements;

wherein each sensing element in the array, in response to an interrogation signal, transmits a signal to the reader via the coupled transmission line when a subject placed on the mat compresses the pressure-sensitive material for the sensing element,

wherein the transmitted signal corresponds to the change in pressure attributable to the placement of the subject on the mat,

wherein the reader determines the change in pressure by altering, the output power and determining the power level at which an identifier ID associated with a sensing element starts to read.

13. The RFID sensing system of claim 12, wherein the pressure-sensitive material comprises a conductive foam.

14. The RFID sensing system of claim 13, further comprising a pressure-sensitive over laminate material separating the sensing element from the conductive foam.

15. The RFID sensing system of claim 12, wherein the pressure-sensitive material comprises a quantum tunneling composite.

16. The RFID sensing system of claim 12, wherein the signal transmitted by each sensing element represents a change in sensitivity for the sensing element resulting from absorption of energy at an operating frequency of the sensing element caused by compression of the pressure-sensitive material.

17. The RFID sensing system of claim 12, wherein the transmission line comprises any one of a microstrip, a twin wire line, and a stripline.

19. The RFID sensing system of claim 12, wherein the signal transmitted by each sensing element represents a change in sensitivity for the sensing element resulting from absorption of energy at an operating frequency of the sensing element caused by compression of the pressure-sensitive material.

20. The RFID sensing system of claim 12, wherein each transmission line comprises any one of a microstrip, a twin wire line, and a stripline.

18. An RFID sensing system comprising:

an array of sensing elements disposed on a surface of a mat, wherein each sensing element includes an RFID microchip, an antenna operatively coupled to the microchip, and a pressure-sensitive material disposed on at least the antenna;

a multi-port RFID reader for interrogating the array of sensing elements;

a plurality of transmission lines each coupled to a separate port of the reader and to an associated plurality of sensing elements in the array of sensing elements;

wherein each sensing element in the array, in response to an interrogation signal, transmits a signal to a reader port via the associated transmission line when a subject placed on the mat compresses the pressure-sensitive material for the sensing element,

wherein the transmitted signal corresponds to the change in pressure attributable to the placement of the subject on the mat,

wherein the reader determines the change in pressure by altering the output power and determining the power level at which an identifier ID associated with a sensing element starts to read.

21. An RFID sensing system comprising:

an array of sensing elements disposed on a surface of a mat, wherein each sensing element includes an RFID microchip, an antenna operatively coupled to the microchip, and a pressure-sensitive material disposed on at least the antenna;

an RFID reader for interrogating the array of sensing elements;

a fixed near field coupler disposed in proximity to the mat for linking the array of sensing elements with the reader via a transmission line disposed on the mat;

wherein each sensing element in the array, in response to an interrogation signal, transmits a signal to the reader via the transmission line and near field coupler when a subject placed on the mat compresses the pressure-sensitive material for the sensing element,

wherein the transmitted signal corresponds to the change in pressure attributable to the placement of the subject on the mat˜

wherein the reader determines the change in pressure by altering the output power and determining the power level at which an identifier ID associated with a sensing element starts to read.

22. The RFID sensing system of claim 21, wherein the pressure-sensitive material comprises a conductive foam.

23. The RFID sensing system of claim 22, further comprising a pressure-sensitive overlaminate material separating the sensing element antenna from the conductive foam.

24. The RFID sensing system of claim 21, wherein the pressure-sensitive material comprises a quantum tunneling composite.

25. The RFID sensing system of claim 21, wherein the signal transmitted by each sensing element represents a change in sensitivity for the sensing element resulting from absorption of energy at an operating frequency of the sensing element caused by compression of the pressure-sensitive material.

26. The RFID sensing system of claim 21, wherein the transmission line comprises any one of a microstrip, a twin wire line, and a stripline.

27. A method for sensing a parameter associated with an RFID sensing system comprising the steps of:

disposing an array of sensing elements on a surface of a mat, wherein each sensing element includes an RFID microchip, an antenna operatively coupled to the microchip, and a pressure-sensitive material disposed on at least the antenna;

interrogating the array of sensing elements using an RFID reader when a subject is placed on the mat compressing the pressure-sensitive material for the sensing element;

communicating with each sensing element disposed on the mat via an antenna operatively coupled to the reader; and

receiving a signal transmitted from each sensing element in the array via the antenna coupled to the reader in response to an interrogation signal,

wherein the transmitted signal corresponds to the change in pressure attributable to the placement of the subject on the mat,

wherein the reader determines the change in pressure by altering the output power and determining the power level at which an identifier ID associated with a sensing element starts to read.

28. The method for sensing a parameter of claim 27, wherein the pressure-sensitive material comprises a conductive foam.

29. The method for sensing a parameter of claim 28, further comprising the step of applying a pressure-sensitive overlaminate to separate the pressure-sensitive material from the conductive foam.

30. The method for sensing a parameter of claim 28, further comprising the step of coating the conductive foam with a plurality of conductive particles.

31. The method for sensing a parameter of claim 27, wherein the pressure-sensitive material comprises a quantum tunneling composite.

32. The method for sensing a parameter of claim 28, wherein the signal transmitted from each sensing element provides a change in sensitivity for the sensing element resulting from absorption of energy at an operating frequency of the sensing element caused by compression of the pressure-sensitive material.

33. The method for sensing a parameter of claim 32, wherein the operating frequency of the sensing element is an ultra high frequency (UHF).

34. The method for sensing a parameter of claim 32, further comprising the step of determining a power level at which an identification associated with the sensing element is read by the RFID reader.

35. The method for sensing a parameter of claim 32, further comprising determining a pressure at a point on the surface of the mat at which the sensing element is located using the change in sensitivity of the sensing element.

36. The method for sensing a parameter of claim 27, further comprising calibrating the sensitivity at each sensing element with no pressure placed on the mat surface.

37. The method for sensing a parameter of claim 27, wherein the step of communicating with each sensing element disposed on the mat comprises illuminating the sensing element by a near field antenna and enabling the reader to measure a plurality of sensor data at the sensing element.

38. The method for sensing a parameter of claim 27, wherein the step of communicating with each sensing element disposed on the mat comprises illuminating the sensing element by a far field antenna and enabling the reader to measure a plurality of sensor data at the sensing element.

39. The method for sensing a parameter of claim 27, further comprising communicating a series of data messages from the reader to the sensing element via an amplitude modulation of a continuous wave signal.

40. The method for sensing a parameter of claim 39, further comprising receiving an identification at the reader in a backscatter modulation of RF energy from each sensing element.

41. The method for sensing a parameter of claim 40, further comprising communicating the identification received from each sensing element from the reader to the sensing element via a frequency modulation of a continuous wave signal.

42. The method for sensing a parameter of claim 41, further comprising passively detecting the identification of each sensing element during the frequency modulation by a remote computer system.

43. A method for sensing a parameter associated with an RFID sensing system comprising the steps of:

disposing an array of sensing elements on a surface of a mat, wherein each sensing element includes an RFID microchip, an antenna operatively coupled to the microchip, and a pressure-sensitive material disposed on at least the antenna;

interrogating the array of sensing elements using an RFID reader when a subject is placed on the mat compressing the pressure-sensitive material for the sensing element;

communicating with each sensing element disposed on the mat via a transmission line operatively coupled to the reader and to at least a plurality of elements in the array of sensing elements; and

receiving a signal transmitted from each sensing element in the array via the transmission line in response to an interrogation signal,

wherein the transmitted signal corresponds to the change in pressure attributable to the placement of the subject on the mat,

wherein the reader determines the change in pressure by altering the output power and determining the power level at which an identifier ID associated with a sensing element starts to read.

44. The method for sensing a parameter of claim 43, further comprising the step of coupling a plurality of transmission lines to separate ports of a multi-port RFID reader, with each transmission line operatively coupled to an associated plurality of sensing elements in the array of sensing elements.