RFID system and method for localizing and tracking a moving object with an RFID tag

• US 20070285245A1
• Filed: 05/01/2007
• Published: 12/13/2007
• Est. Priority Date: 05/01/2006
• Status: Active Grant

• Current Assignee: Akshay Athalve, Petar Djuric
• Original Assignee: Akshay Athalve, Petar Djuric
• Inventors: Athalve, Akshay, Djuric, Petar
• Granted Patent: US 7,812,719 B2
• Time in Patent Office: Days
• US Class Current: 340/572.100
• CPC Class Codes: G08B 13/1427 with transmitter-receiver for distance detection
• CPC Class Codes: G08B 21/0275 Electronic Article Surveillance [EAS] tag technology used for parent or child unit, e.g. same transmission technology, magnetic tag, RF tag, RFID

Abstract

A radio frequency identification (RFID) system and method for tracking and locating an RFID tag is disclosed. The system includes a reader, an identification tag, at least one sensor-tag and a data processing element. The reader is used to initiate a query for an object with an RFID tag. The identification tag is attached to the object. The RFID tag responds to the query. At least one sensor-tag is positioned near the RFID tag. The at least one sensor-tag functions to receive the response of the RFID tag. The sensor-tag determines whether the identification tag is within a predetermined sensor-tag range. Based upon this determination, the at least one sensor-tag communicates a response signal to the reader when the at least one sensor-tag receives a predetermined request signal from the reader. Based on the responses of the sensor-tags, the location of the object with the responding RFID tag can be calculated.

Claims

1. A radio frequency identification (RFID) system for object location and tracking comprising:

An RFID reader for initiating a query for an RFID tag attached to an object

an RFID tag attached to said object for responding to said query;

at least one sensor-tag for receiving said response from said RFID tag, and determining whether said RFID tag is within a predetermined range,

the said at least one sensor-tag communicates a response signal to said reader, based upon the determination, when said at least one sensor-tag receives a request signal from said reader; and

a data processing element for processing said response signals received from said at least one sensor-tag to determine the location of said RFID tag using a predefined calculation.

9. The radio frequency location determination system of claim 1, wherein said data processing element is a fusion element remotely located from said reader.

10. The radio frequency position detection system of claim 1, wherein said data processing element is embedded in said reader.

11. The radio frequency position detection system of claim 1, wherein said identification tag, and at least one sensor-tag are passive elements powered by the radiation received by the said reader.

12. The radio frequency position detection system of claim 1, wherein said at least one sensor-tag and/or said identification tag are semi-passive.

2. A location determination method comprising:

(a) initiating a query for identification using a radio frequency identification (RFID) reader;

(b) responding to said query by a radio frequency identification (RFID) tag;

(c) receiving said response signal by at least one sensor-tag;

(d) determining if said radio frequency identification (RFID) tag that responded to the query is within a predetermined range of said at least one sensor-tag;

(e) communicating a signal based upon said determination when said at least one sensor-tag receives a request signal; and

(f) determining the location of said RFID tag based upon said signal from said at least one sensor-tag using a predetermined method.

3. The location determination method of claim 2, further comprising the step of:

accounting for any interference at said at least one sensor-tag between said tag response signal and the signal received from a reader by variably controlling amplitude and/or phase of said response signal from said RFID tag.

4. The location determination method of claim 2, further comprising the step of:

initializing said predetermined sensing range for each of said at least one sensor-tags by setting a threshold value for a minimum power value for said response signal required for detection by said each of said at least one sensor-tags.

5. The position determination method of claim 4, wherein said predetermined sensor-tag range is determined based upon a number of said at least one sensor-tags within an area.

6. The position determination method of claim 2, further comprising the step of:

deploying said at least one sensor-tag in a known location to create a predefined sensor-tag grid.

7. The position determination method of claim 2, wherein step (h) includes determining a location of said RFID tag and tracking movement of said RFID tag.

8. The position determination method of claim 4, wherein predetermined sensing range is determined based upon signal strength of said query from said reader.

13. The position determination method of claim 2, wherein step (d) includes the sub-steps of:

(a) decoding the said received response from said RFID tag to determine if said tag is within said predefined sensing range

(b) modifying the contents of a tag location register on said sensor-tag based on said determination and conveying this information to said reader along with predefined response.

14. The location determination method of claim 13, wherein said predefined response includes sensor-tag identification number.

15. The location determination method of claim 2, wherein determining a location of said RFID tag includes estimating the position of said RFID tag by calculating an overlapping area determined by an intersection of all of the ranges of said at lest one sensor-tag that communicated said position signal, said overlapping area contains the location of said RFID tag.

16. The position determination method of claim 7, wherein tracking movement of said RFID tag includes estimating a change in a position of said RFID tag over time by repeatedly calculating an overlapping area determined by an intersection of all of the ranges of said at lest one sensor-tag that communicated said position signal, a change in the overlapping area, over time is the movement of said RFID tag.

17. The position determination method of claim 2, further comprising the step of deploying said at least one sensor-tag in a random location, wherein the step of determining the locations of said randomly deployed sensor-tags includes the sub-steps of:

(a) transmitting a request signal from a reader at a known location and with known power;

(b) sending a reply signal from each of said at least one sensor-tags including each sensor-tag'"'"'s identification, if said sensor-tag receives said request signal;

(c) relocating said reader within a predefined area and varying the said known power;

(d) repeating sub-steps (a)-(c) until all of said at known locations are passed and known powers are used;

(e) estimating each sensor-tag'"'"'s position based upon said received sensor-tag IDs, said known locations, and said known powers.