Navigation system using radio frequency tags

• US 7,339,523 B2
• Filed: 12/05/2005
• Issued: 03/04/2008
• Est. Priority Date: 12/05/2005
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Bye, Charles T.
• Primary Examiner(s): Tarcza; Thomas H.
• Assistant Examiner(s): Nguyen; Nga X
• Application Number:
  US11/294,582
• Publication Number:
  US 20070126634A1
• Time in Patent Office: 820 Days
• Field of Search: 342/451, 342463-465
• US Class Current: 342/451
• CPC Class Codes: G01S 1/68 Marker, boundary, call-sign, or like beacons transmitting signals not carrying directional information
• CPC Class Codes: G01S 5/02521 using a radio-map

Abstract

A method of determining a location is provided. The method comprises placing a plurality of radio frequency (RF) tags within an area, mapping the placement of the plurality of RF tags within the area, detecting one or more of the plurality of RF tags in the area, and determining a location based in part on the mapping and on probability distributions associated with each of the one or more detected RF tags.

Claims

1. A method of determining a location, the method comprising:

placing a plurality of radio frequency (RF) tags within an area;

mapping the placement of the plurality of RF tags within the area;

detecting one or more of the plurality of RF tags in the area; and

determining a location based in part on the mapping and on probability distributions associated with each of the one or more detected RF tags, wherein each probability distribution represents the probability of detecting its associated RF tag from each of a plurality of locations.

2. The method of claim 1, wherein determining a location further comprises:

determining a location based on the location of RF tags not detected.

3. The method of claim 1, further comprising:

calculating a probability distribution for each RF tag within the area; and

storing the calculated probability distributions in a database with location data for each associated RF tag.

4. The method of claim 1, wherein detecting one or more RF tags further comprises:

calculating a probability distribution for each RF tag when each RF tag is detected.

5. The method of claim 4, wherein calculating a probability distribution for each RF tag further comprises calculating a probability distribution for each RF tag based on the signal strength of a signal from each detected RF tag.

6. The method of claim 4, wherein calculating a probability distribution further comprises calculating a unique probability distribution for each RF tag.

7. The method of claim 1, wherein determining a location based on probability distributions further comprises:

combining each probability distribution associated with the one or more detected RF tags to obtain a combined probability distribution, wherein the location is determined based on coordinates in the combined probability distribution corresponding to the highest probability.

8. The method of claim 7, wherein combining each probability distribution includes weighting each probability distribution based on the signal strength of the corresponding detected RF tag.

9. The method of claim 1, further comprising:

receiving navigational data from one or more additional sensors, wherein the navigational data is combined with the probability distributions associated with the one or more detected RF tags to determine a location.

10. The method of claim 9, wherein receiving navigational data from one or more additional sensors includes one of:

combining the navigational data substantially instantaneously with the probability distributions associated with the one or more detected RF tags; and

combining the navigational data with the probability distributions associated with the one or more RF tags using a history of probability distributions and recorded position estimates.

11. A radio frequency (RF) tag navigation system comprising:

a plurality of RF tags positioned within a selected area;

an RF tag reader adapted to move with a user, the RF tag reader further being adapted to receive signals from one or more of the plurality of RF tags that are in range of the RF tag reader, such that the one or more RF tags from which signals are received varies according to changes in the user'"'"'s location; and

a processing unit for receiving RF tag data from the RF tag reader, the processing unit being adapted to determine the user'"'"'s location based on probability distributions for receiving a signal associated with each of the one or more RF tags from which a signal is received, wherein each probability distribution represents the probability of detecting its associated RF tag from each of a plurality of locations.

12. The RF tag navigation system of claim 11, further comprising:

an RF tag database, the RF tag database being adapted to store location data and probability distribution data for each of the plurality of RF tags.

13. The RF tag navigation system of claim 11, wherein the plurality of RF tags includes

at least one of a passive RF tag and an active RF tag.

14. The RF tag navigation system of claim 11, farther comprising navigational sensors for providing navigation data to the processing unit, the processing unit being adapted to determine the user'"'"'s location based on the probability distributions and data from the navigational sensors.

15. The RF tag navigation system of claim 11, wherein the processing unit calculates a probability distribution for each RF tag when a signal is received, the probability distribution being based on the signal strength of the RF tag signal received.

16. The RF tag navigation system of claim 15, wherein the processing unit calculates a unique probability distribution for each RF tag when a signal is received.

17. The RF tag navigation system of claim 11, wherein the processing unit combines the probability distribution for each of the one or more of the plurality of RF tags, from which a signal is received, into one probability distribution for receiving a signal from all of the one or more of the plurality of RF tags, the user'"'"'s location being determined to be a set of coordinates corresponding to the highest probability in the combined probability distribution.

18. The RF tag navigation system of claim 17, wherein, when combining the probability distributions, the processing unit is adapted to weight each of the probability distributions based on the signal strength of the signal received from each of the one or more RF tags.

19. A computer readable medium having computer-executable instructions for performing a method of determining a user'"'"'s location within an area being mapped using radio frequency (RF) tags, the method comprising:

receiving signal data for one or more RF tags;

processing a probability distribution for receiving a signal for each of the one or more RF tags; and

determining a user'"'"'s location based on a combination of the probability distributions for the one or more RF tags for which signal data is received.

20. The computer readable medium of claim 19, further comprising:

receiving data from navigation sensors the navigation data being used in conjunction with the combination of probability distributions in determining a user'"'"'s location.

21. The computer readable medium of claim 19, wherein determining a user'"'"'s location based on a combination of the probability distributions includes determining a user'"'"'s location based on a weighted combination of the probability distributions, wherein the probability distributions are weighted according to the strength of the signal received for each of the one or more RF tags.

22. The computer readable medium of claim 19, wherein processing a probability distribution further comprises receiving a probability distribution from an RF tag database based on the signal data received.

23. The computer readable medium of claim 19, wherein processing a probability distribution further comprises calculating a probability distribution for each of the one or more RF tags in real-time as the signal data is received.

24. The computer readable medium of claim 23, wherein calculating a probability distribution further comprises calculating a probability distribution for each of the one or more RF tags based on the strength of the signal received for each of the one or more RF tags.

25. The computer readable medium of claim 23, wherein calculating a probability distribution further comprises calculating a unique probability distribution for each of the one or more RF tags.

26. A radio frequency (RF) tag navigation system comprising:

a means for receiving signals from one or more of a plurality of RF tags positioned within an area, wherein signals are received from varying RF tags as a user'"'"'s location changes; and

a means for calculating a user'"'"'s location based on probability distribution of receiving a signal for each of the one or more RF tags, wherein each probability distribution represents the probability of detecting its associated RF tag from each of a plurality of locations.

27. The radio frequency (RF) tag navigation system of claim 26 further comprising:

a means for obtaining additional navigational data; and

a means for combining the navigational data with the probability distribution of receiving a signal for each of the one or more RF tags.