Reverse RFID location system

• US 20110043373A1
• Filed: 08/20/2009
• Published: 02/24/2011
• Est. Priority Date: 08/20/2009
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Sanders, Jeffrey D., Ansell, Andrew, Byard, Gwen, Jervis, James W., Best, Gregory C.
• Granted Patent: US 8,797,141 B2
• Time in Patent Office: Days
• US Class Current: 340/8.1
• CPC Class Codes: G01S 1/68 Marker, boundary, call-sign, or like beacons transmitting signals not carrying directional information
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236
• CPC Class Codes: G06K 7/10049 binary tree
• CPC Class Codes: G06K 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions

Abstract

A reverse RFID location system is based on set of RFID tags in which each tag stores data representing its position.

Claims

1. A system comprising:

a set of radio frequency identification tags, each tag storing data representing its position; and

,

a radio frequency identification tag reader that estimates its position based on the positions of tags in the set as reported by the tags to the reader.

2. The system of claim 1 wherein data representing the position of a tag along two or more axes is interleaved.

3. The system of claim 1 wherein one or more tags store data representing the direction to a location.

4. The system of claim 1 wherein one or more tags store data representing the distance to a location.

5. The system of claim 1 wherein one or more tags store data representing information supplied by a sensor associated with a tag.

6. The system of claim 1 wherein one or more tags store data representing a map.

7. The system of claim 1 wherein one or more tags store data representing a hazard.

8. The system of claim 7 wherein the data represents information in the National Fire Protection Agency Hazard Identification format.

9. The system of claim 1 wherein one or more tags are attached to objects chosen from the list consisting of:

ceiling tiles, carpets, sprinkler heads, embedded in construction materials, switch plates.

10. The system of claim 1 wherein the reader writes data to one or more tags.

11. The system of claim 10 wherein the data comprises the reader'"'"'s position.

12. The system of claim 1 wherein the reader comprises a user interface.

13. The system of claim 12 wherein the interface comprises an audio input device.

14. The system of claim 12 wherein the interface comprises an audio output device.

15. The system of claim 12 wherein the interface comprises a display.

16. The system of claim 12 wherein the reader indicates its position.

17. The system of claim 12 wherein the reader indicates the direction to a location.

18. The system of claim 12 wherein the reader indicates the distance to a location.

19. The system of claim 12 wherein the interface comprises a tactile device.

20. The system of claim 1 wherein the reader estimates its position by assuming that the reader is at a position reported by a radio frequency identification tag.

21. The system of claim 1 wherein the reader estimates its position by assuming that the reader is at a position reported by the radio frequency identification tag having the greatest return signal strength of all such tags detected by the reader.

22. The system of claim 1 wherein the reader estimates its position by aggregating positions reported by two or more radio frequency identification tags.

23. The system of claim 22 wherein the reader estimates its position by averaging positions reported by two or more radio frequency identification tags.

24. The system of claim 22 wherein the reader estimates its position by performing a weighted average of positions reported by two or more radio frequency identification tags.

25. The system of claim 24 wherein the average is weighted by a function of signal strength returned by each tag in the average.

26. The system of claim 22 wherein the reader estimates its position based on the median of positions of tags reported by the tags to the reader.

27. The system of claim 1 wherein the reader estimates its position based on the positions of tags reported by the tags to the reader more recently than a set time threshold ago.

28. The system of claim 27 wherein the time threshold is one second.

29. A method of estimating the position of a radio frequency identification tag reader comprising assuming the reader is at a position reported by a radio frequency identification tag.

30. A method of estimating the position of a radio frequency identification tag reader comprising assuming the reader is at a position reported by the radio frequency identification tag having the greatest return signal strength of all such tags detected by the reader.

31. A method of estimating the position of a radio frequency identification tag reader comprising averaging the reported positions of two or more radio frequency identification tags.

32. The method of claim 31 wherein the average is weighted by the signal strength returned to the reader by each tag.

33. The method of claim 31 wherein the average is weighted by a function of the signal strength returned to the reader by each tag.

34. The method of claim 31 further comprising:

estimating the speed of the reader from two or more position estimates.

35. The method of claim 31 further comprising:

estimating the direction of travel of the reader from two or more position estimates.

36. A method of estimating the position of a radio frequency identification tag reader comprising assuming the reader is at the median of positions reported by radio frequency identification tags.

37. A radio frequency identification tag reader that estimates its position based on the position of one or more radio frequency identification tags as reported by the tags directly to the reader.