System for tracking object locations using self-tracking tags

• US 20050116823A1
• Filed: 06/15/2004
• Published: 06/02/2005
• Est. Priority Date: 12/03/2003
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens Technology-To-Business Center LLC (Siemens AG)
• Inventors: Meyer, Heinrich, Arman, Farshid, Paulsen, Torsten
• Granted Patent: US 7,119,687 B2
• Time in Patent Office: Days
• US Class Current: 340/539.130
• CPC Class Codes: G01S 2205/002 for traffic control, mobile tracking, guidance, surveillance or anti-collision
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G08B 13/2454 Checking of authorisation of a person accessing tagged items in an EAS system
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00

Abstract

An object tracking system includes a plurality of tags. Each tag includes a mechanism for transmitting a triangulation signal and a position signal that is indicative of a change of position of the respective tag in a time period since a respective reset event. A plurality of triangulation stations receive the triangulation signals from the tags. At least one antenna receives the position signals from the tags. A computer is coupled to the triangulation stations and to the antenna. The computer is programmed to switch between (a) a first tag location algorithm to determine a current location of one of the tags using a differential time of arrival procedure based on the triangulation signal, and (b) a second tag location algorithm to determine a current location of the tag based on the position signal transmitted by the tag and a previous known location of the tag.

Claims

1. A system comprising:

a plurality of tags, each tag including means for transmitting a triangulation signal and a position signal, the position signal indicative of a change of position of the respective tag in a time period since a respective reset event;

a plurality of triangulation stations for receiving the triangulation signals from the tags;

at least one antenna for receiving the position signals from the tags; and

a computer coupled to the triangulation stations and to the at least one antenna, the computer programmed to switch between;

(a) a first tag location algorithm in which the computer determines a current location of one of the tags using a differential time of arrival procedure based on the triangulation signal transmitted by said one of the tags and received by at least some of the triangulation stations; and

(b) a second tag location algorithm in which the computer determines a current location of said one of the tags based on the position signal transmitted by said one of the tags and a previous known position of said one of the tags.

2. A system according to claim 1, wherein the computer is a server computer installed at a fixed location.

3. A system according to claim 1, further comprising:

at least one client computer coupled to the server computer to allow a user of the client computer to query the server computer as to a current location of at least one of the tags.

4. A system according to claim 1, wherein each of the tags includes:

at least one sensor including at least one acceleration sensor; and

generating means for generating said position signal based on information from said at least one sensor.

5. A system according to claim 4, further comprising:

reset means for indicating to said generating means occurrence of said respective reset event.

6. A system according to claim 4, wherein the at least one sensor includes a gyroscope.

7. A system according to claim 1, further comprising:

at least one interrogation gate coupled to the computer.

8. A method comprising:

(a) selectively employing a differential time of arrival procedure to determine a current location of a tag based on a triangulation signal transmitted by the tag; and

(b) determining a current location of the tag based on a position signal transmitted by the tag and a previous known location of the tag.

9. A method according to claim 8, further comprising:

receiving from the tag an identification code that uniquely identifies the tag.

10. A method according to claim 8, wherein said position signal is indicative of a change of position of said tag in a time period since a reset event.

11. A method according to claim 8, wherein said position signal includes data calculated based at least in part on input signals from at least one acceleration sensor in the tag.

12. A tag comprising:

a housing;

first transmitting means in said housing for transmitting a triangulation signal;

at least one sensor in the housing, said at least one sensor including at least one acceleration sensor;

calculating means in said housing for receiving sensor information from said at least one sensor and for calculating position data for the tag based on the sensor information; and

second transmitting means in said housing for selectively transmitting said position data calculated by said calculating means.

13. A tag according to claim 12, wherein the first transmitting means transmits as part of the triangulation signal an identification code that uniquely identifies the tag.

14. A tag according to claim 13, further comprising:

response means in said housing for receiving an interrogation signal from an interrogation gate and for transmitting said identification code in response to receipt of said interrogation signal.

15. A tag according to claim 14, further comprising:

reset means coupled to said calculating means for receiving a reset signal;

and wherein said calculating means calculates said position data to indicate movement of the tag from a time when the reset means received the reset signal.

16. A tag according to claim 15, wherein said interrogation signal is said reset signal.

17. A tag according to claim 12, further comprising:

reset means coupled to said calculating means for receiving a reset signal;

and wherein said calculating means calculates said position data to indicate movement of the tag from a time when the reset means received the reset signal.

18. A tag according to claim 12, wherein:

said calculating means calculates a current direction of motion of the tag based on the sensor information; and

said second transmitting means transmits to an interrogation gate data indicative of the current direction of motion calculated by said calculating means.

19. A tag according to claim 12, wherein said second transmitting means includes a radio frequency transmitter.

20. A tag comprising:

a housing;

response means in said housing for receiving an interrogation signal from an interrogation gate and for transmitting, in response to receipt of said interrogation signal, an identification code that uniquely identifies the tag;

at least one sensor in the housing, said at least one sensor including at least one acceleration sensor; and

calculating means in said housing for receiving sensor information from said at least one sensor and for calculating a current direction of motion of the tag based on the sensor information;

wherein said response means transmits to the interrogation gate data indicative of the current direction of motion calculated by said calculating means.

21. A method comprising:

determining a current location of a tag based on a signal from an interrogation gate when the tag is in proximity to the interrogation gate; and

when the tag is not in proximity to any interrogation gate, determining a current location of the tag based on a position signal transmitted by the tag and a previous known location of the tag.

22. A method according to claim 21, further comprising:

receiving from the tag an identification code that uniquely identifies the tag.

23. A method according to claim 21, wherein said position signal is indicative of a change of position of said tag in a time period since a reset event.

24. A method according to claim 21, wherein said position signal includes data calculated based at least in part on input signals from at least one acceleration sensor in the tag.

25. A method according to claim 21, further comprising:

selectively employing a differential time of arrival procedure to determine a current location of the tag based on a triangulation signal transmitted by the tag.

26. A system comprising:

a plurality of tags, each tag including means for transmitting a response signal and a position signal, the position signal indicative of a change of position of the respective tag in a time period since a respective reset event;

a plurality of interrogation gates;

at least one antenna for receiving the position signals from the tags; and

a computer coupled to the interrogation gates and to the at least one antenna, the computer programmed to;

determine a current location of one of said tags based on a signal from one of the interrogation gates at a time when said one of the tags is in proximity to said one of the interrogation gates; and

determine, at a time when said one of the tags is not in proximity to any of the interrogation gates, a current location of said one of the tags based on the respective position signal transmitted by said one of the tags and a previous known location of said one of the tags.

27. A system according to claim 26, wherein the respective reset event is interrogation of the respective tag by one of the interrogation gates.

28. A system according to claim 26, wherein the computer is a server computer installed at a fixed location.

29. A system according to claim 28, further comprising:

at least one client computer coupled to the server computer to allow a user of the client computer to query the server computer as to a current location of at least one of the tags.

30. A system according to claim 26, wherein each of the tags includes:

at least one sensor including at least one acceleration sensor; and

means for generating said position signal based on information from said at least one sensor.

31. A system according to claim 26, wherein:

each of said plurality of tags includes means for transmitting a triangulation signal;

the system further comprises a plurality of triangulation stations for receiving the triangulation signals from the tag signal; and

said computer is further programmed to determine a current location of said one of the tags using a differential time of arrival procedure based on the triangulation signal transmitted by said one of the tags and received by at least some of the triangulation stations.

32. A system according to claim 31, wherein said position signal transmitted by said one of the tags is indicative of a change of position of said one of the tags in a time period since a respective reset event.