Method and apparatus for locating mobile tags

• US 6,456,239 B1
• Filed: 08/24/2000
• Issued: 09/24/2002
• Est. Priority Date: 08/25/1999
• Status: Expired due to Term

• Current Assignee: RF Technologies, Inc. (Microwave Techniques LLC)
• Original Assignee: RF Technologies, Inc. (Microwave Techniques LLC)
• Inventors: Levy, Samuel, Stein, Peter, Swiderek, Melanie, Martinian, Emin, Werb, Jay
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Mull, Fred H.
• Application Number:
  US09/645,280
• Time in Patent Office: 761 Days
• Field of Search: 342/450, 342/451, 342/452, 342/457, 342/458, 342/463, 342/465, 342/453, 235/385, 705/28, 706/24, 706/18, 455/456
• US Class Current: 342/463
• CPC Class Codes: G01S 11/16 using difference in transit time between electrical and acoustic signals
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/0269 Inferred or constrained positioning, e.g. employing knowledge of the physical or electromagnetic environment, state of motion or other contextual information to infer or constrain a position
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• 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
• CPC Class Codes: G06Q 10/087 Inventory or stock management, e.g. order filling, procurement or balancing against orders

Abstract

A method and apparatus for determining tag location is disclosed. Tag reference data may be stored, e.g., in the form of a lookup table, as a trained neural network, and so on, and used to determine the location of tags. Readings used to determine tag location and/or preliminary tag locations may be filtered to produce reliable tag location indications. Packages of user configurable parameters can be provided and used for the filtering of the preliminary tag locations. Confidence levels may also be generated for determined tag locations and used, for example, to indicate how well an asset location system can distinguish between different tag locations.

Claims

1. A system for determining a location of a tag, comprising:

at least one receiver that receives a signal from the tag;

a controller that communicates with the at least one receiver; and

a memory that stores information regarding previous communication between at least one receiver and a reference tag while the reference tag was in at least two different locations;

wherein the controller determines a location of the tag based on information stored in the memory regarding the previous communication with the reference tag; and

wherein the controller provides a plurality of configuration setting packages that can be selected by a user.

2. The system of claim 1, wherein the information stored in the memory regarding communications with the reference tag is based on at least one of a time of arrival of a signal from the reference tag at a receiver, a round trip time of flight of a signal between a receiver and the reference tag, a time difference of arrival of signals received at two or more receivers, a strength of a signal received at a receiver, variable receiver sensitivity to a signal sent from the reference tag, and an ultrasonic signal sent from the reference tag.

3. The system of claim 1, wherein the information stored in the memory is indicative of a distance between at least one receiver and the tag.

4. The system of claim 1, wherein the information stored in the memory includes a quality metric to determine a quality of a signal received from a tag.

5. The system of claim 1, wherein the controller displays information representing previously detected signals from the reference tag.

6. The system of claim 5, wherein the displayed information includes an indication of a distance between the reference tag and a receiver while the reference tag was located within a zone.

7. The system of claim 1, wherein the controller stores a set of rules used to determine a tag location using communications between at least one receiver and the tag, the rules being generated based on the previous communications with the reference tag.

8. The system of claim 1, wherein the controller uses the information regarding previous communication with the reference tag to train a neural network.

9. The system of claim 8, wherein the neural network is a feed-forward network that is used to determine tag location.

10. The system of claim 1, wherein the controller uses the information regarding previous communication with the reference tag to populate a lookup table.

11. The system of claim 10, wherein the lookup table is a hash table used to determine tag location.

12. The system of claim 1, wherein an individual zone may be selected as a particular type of zone by a user and a corresponding configuration package is used to control how the controller determines tag location for the selected zone.

13. The system of claim 1, wherein the controller provides user configurable settings for at least one of sequential filtering of tag tracking data, average filtering of tag tracking data, time filtering of tag tracking data, and a tag location publication delay.

14. The system of claim 1, wherein the controller determines a confidence level for the location determined for the tag.

15. The system of claim 14, wherein the confidence levels are determined based on one of prior probability information regarding the tag, and a transitional probability for the tag.

16. The system of claim 14, wherein the controller uses the confidence level to determine whether to indicate that the tag has moved from one location to another.

17. The system of claim 16, wherein the controller uses a variable threshold to determine whether to indicate that the tag has moved from one location to another, the variable threshold being variable depending upon a zone in which the tag is located.

18. The system of claim 16, wherein the controller uses a variable threshold to determine whether to indicate that the tag has moved from one location to another, the variable threshold being variable depending upon whether the tag location is to be used for real-time tracking or archival purposes.

19. The system of claim 14, wherein the controller uses the confidence level to identify zones in which tags are seldom located.

20. The system of claim 14, wherein the controller uses the confidence level to trigger an alarm based on the tag location.

21. A method for locating a tag, comprising:

receiving a signal from a reference tag;

storing information regarding the signal received from the reference tag, the signal being received from the reference tag while the reference tag is in at least two locations;

determining a location of the tag based on the stored information regarding the signal received from the reference tag; and

providing a plurality of configuration setting packages that can be selected by a user.

22. An article of manufacture comprising instructions to control a data processing apparatus, the instructions operative to cause the data processing apparatus to perform the method of claim 21.

23. The method of claim 21, wherein the step of storing information comprises storing information that is based on at least one of a time of arrival of a signal from the reference tag at a receiver, a round trip time of flight of a signal between a receiver and the reference tag, a time difference of arrival of signals received at two or more receivers, a strength of a signal received at a receiver, variable receiver sensitivity to a signal sent from the reference tag, and an ultrasonic signal sent from the reference tag.

24. The method of claim 21, wherein the step of storing information comprises storing information that is indicative of a distance between at least one receiver and the reference tag.

25. The method of claim 21, further comprising storing a quality metric to determine a quality of a signal received from a tag.

26. The method of claim 21, further comprising displaying information representing previously detected signals from the reference tag.

27. The method of claim 26, wherein the step of displaying information comprises providing an indication of a number of antenna readings indicating a tag-antenna distance while the reference tag was located within a zone.

28. The method of claim 21, wherein the step of determining a location comprises using a set of rules used to determine the tracking tag location using communications between a receiver and the tracking tag, the rules being generated based on the stored information regarding previous communications with the reference tag.

29. The method of claim 21, further comprising using the stored information regarding previous communication with the reference tag to train a neural network.

30. The method of claim 29, wherein the step of using the stored information comprises using the stored information to train a feed-forward network that is used to determine tag location.

31. The method of claim 21, further comprising populating a lookup table that is used to determine a location of the tracking tag using the stored information regarding previous communication with the reference tag.

32. The method of claim 31, wherein the step of populating comprises populating a hash table used to determine tag location.

33. The method of claim 21, wherein the step of providing comprises

providing zones that can be selected as a particular type of zone by a user, and the method further comprising:

using configuration packages that correspond to the selected zones to control how the controller determines tag location for the selected zones.

34. The method of claim 21, further comprising providing user configurable settings for at least one of sequential filtering of tag tracking data, average filtering of tag tracking data, time filtering of tag tracking data, and a tag location publication delay.

35. The method of claim 21, further comprising determining a confidence level for the location determined for the tracking tag.

36. The method of claim 35, wherein the step of determining a confidence level comprises determining confidence levels based on one of prior probability information regarding the tracking tag, and a transitional probability for the tracking tag.

37. The method of claim 35, further comprising using the confidence level to determine whether to indicate that the tag has moved from one location to another.

38. The method of claim 35, further comprising using a variable confidence level threshold to determine whether to indicate that the tag has moved from one location to another, the variable threshold being variable depending upon a zone in which the tag is located.

39. The method of claim 35, further comprising using a variable confidence level threshold to determine whether to indicate that the tag has moved from one location to another, the variable threshold being variable depending upon whether the tag location is to be used for real-time tracking or archival purposes.

40. The method of claim 35, further comprising using the confidence level to identify zones in which tags are seldom located.

41. The method of claim 35, further comprising using the confidence level to trigger an alarm based on the tag location.

42. A method of setting up a system for determining a location of a tag within a facility, comprising the acts of:

providing a template of at least one tag locating system comprising at least one zone layout including a receiver locations layout and corresponding rules;

selecting a zone layout;

placing receivers at receiver locations defined by the receiver locations layout; and

using the corresponding rules to set up the system.

43. The method of claim 42, wherein the act of providing the template comprises:

providing tag location rules that are used to determine a location of a tracking tag based on at least one signal received by a receiver; and

wherein the step of placing receivers at receiver locations comprises establishing a physical size of at least one zone in the zone layout.

44. A method of determining a location of a tag, comprising:

providing at least one device to communicate with the tag;

receiving a signal representing communication with the tag;

determining a preliminary location for the tag based on the signal;

filtering the preliminary location for the tag using one of sticky rule filtering, sequential filtering, average filtering, time filtering and a tag location publication delay, before using the preliminary location to determine the tag location;

receiving user input configuration parameters that are used to adjust the filtering of the preliminary location; and

providing packages of user configurable parameters that can be selected and used for filtering preliminary location data from a specific zone.

45. The method of claim 44, wherein the step of receiving user input comprises:

receiving different sets of user input configuration parameters for different zones.

46. The method of claim 44, further comprising:

determining a first location for the tag, the first location intended for use with real-time tracking of the tag; and

determining a second location for the tag, the second location intended for use storage in a tag movement archive.