RFID Tagged Item Trajectory And Location Estimation System And Method

• US 20080291041A1
• Filed: 03/25/2008
• Published: 11/27/2008
• Est. Priority Date: 03/30/2007
• Status: Active Grant

• Current Assignee: Novanta Corporation (Novanta Inc.)
• Original Assignee: SkyeTek, Inc. (RFID Holdings, Inc.)
• Inventors: Chakraborty, Sayan
• Granted Patent: US 7,859,411 B2
• Time in Patent Office: Days
• US Class Current: 340/670
• CPC Class Codes: G01S 5/0294 Trajectory determination or predictive filtering, e.g. target tracking or Kalman filtering
• CPC Class Codes: G06Q 10/087 Inventory or stock management, e.g. order filling, procurement or balancing against orders
• CPC Class Codes: G06Q 20/203 Inventory monitoring

Abstract

A system for predicting a trajectory of an item tagged with an RFID tag. The system includes a network of communicatively coupled RFID readers, each having tag cache memory, and a search engine communicatively coupled with the tag caches in each of the readers. When a tag is within operating range of one of the readers, the tag is interrogated for its data and path information comprising timestamps of reader-tag interactions and related event data, and updated path information is stored in the tag cache memory. The search engine performs a search the tag cache memory in one of one of the readers to locate information corresponding to search criteria including characteristics of the tagged item sought. When the information corresponding to the search criteria is found, the path information is retrieved, and the trajectory of the item is extrapolated using a transit time of the item and average velocity of the item, determined from the timestamps and known distances between locations of each of the reader-tag interactions, along an expected path of the item.

Claims

1. A system for predicting a trajectory of an item tagged with an RFID tag comprising:

a network of communicatively coupled RFID readers, each having tag cache memory; and

a search engine communicatively coupled with the tag caches in each of the readers;

wherein, when the tag is within operating range of one of the readers, the tag is interrogated for its data and path information comprising timestamps of reader-tag interactions and related event data, and updated path information is stored in the tag cache memory;

wherein the search engine, performs a search the tag cache memory in one of one of the readers to locate information corresponding to search criteria including characteristics of the tagged item sought;

wherein, when the information corresponding to the search criteria is found, the path information is retrieved, and the trajectory of the item is extrapolated using a transit time of the item and average velocity of the item, determined from the timestamps and known distances between locations of each of the reader-tag interactions, along an expected path of the item.

2. The system of claim 1, wherein the present location of the item is predicted by extrapolating the item'"'"'s distance from the recent reader most recently interrogating the tag, using the average velocity and time since the item was interrogated by the recent reader, along an expected path between the recent reader and the reader next expected to read the tag.

3. The system of claim 1, wherein the time of arrival of the item at the reader next expected to read the tag is predicted by adding a transit time to the arrival time at the previous reader.

4. The system of claim 1, wherein the search engine causes results of the search to be displayed.

5. The system of claim 1, wherein the results of the search are filtered to remove duplicate entries, poor quality matches, and entries outside a specific time window.

7. The system of claim 1, wherein the present location of the item is predicted by extrapolating the item'"'"'s distance from the recent reader most recently interrogating the tag, using the average velocity and time since the item was interrogated by the recent reader, along an expected path between the recent reader and the reader next expected to read the tag.

8. The system of claim 1, wherein the time of arrival of the item at the reader next expected to read the tag is predicted by adding a transit time to the arrival time at the previous reader.

9. The system of claim 1, wherein the search engine displays results of the search.

10. The system of claim 1, wherein the results of the search are filtered to remove duplicate entries, poor quality matches, and entries outside a specific time window.

11. The system of claim 10, including a results display comprising an ordered list of entries matching the search criteria in ascending/descending order of time and/or quality of search match.

12. The system of claim 11, wherein the results display comprises a map showing locations of one or more readers and the entries corresponding with those readers displayed as a path for the item.

13. The system of claim 10, wherein one or more of an item velocity, a predicted path, and projected arrival times at known locations are displayed on the results display.

6. A system for predicting a trajectory of an item tagged with an RFID tag comprising:

a plurality of communicatively coupled RFID readers having tag cache memory; and

a search engine, associated with each of the readers, on an external processor coupled to the tag cache memory;

wherein;

data stored in the tag is read by readers encountering the tag and stored in an associated tag cache memory;

a search in tag cache is performed for a unique entry;

if the unique entry is not in the present reader'"'"'s tag cache, then the next reader'"'"'s tag cache is read;

if the unique entry is found in the present reader'"'"'s tag cache, then the item'"'"'s present location and a timestamp of the current time are stored in the tag cache memory;

a prediction is then made of the time of arrival of the tagged item at the next expected reader location; and

an event notification is sent to the reader at the next expected reader location.

14. A method for predicting a trajectory of an item tagged with an RFID tag, in a system including a network of RFID readers, each having a tag cache associated therewith for storing data concerning tags the reader has read, the method comprising:

interrogating the tag cache for path information comprising timestamps of reader-tag interactions and related event data, and updated path information is stored in the tag cache, when the tag is within operating range of one of the readers; and

performing a search of the tag caches to locate information corresponding to search criteria including characteristics of the item sought;

wherein, when the information corresponding to the search criteria is found, the path information is retrieved, and the trajectory of the item is extrapolated using a transit time of the item and average velocity of the item, determined from the timestamps and known distances between locations of each of the reader-tag interactions, along an expected path of the item.

15. The method of claim 14, wherein the present location of the item is predicted by extrapolating the item'"'"'s distance from the recent reader most recently interrogating the tag, using the average velocity and time since the item was interrogated by the recent reader, along an expected path between the recent reader and the reader next expected to read the tag.

16. The method of claim 14, wherein the time of arrival of the item at the reader next expected to read the tag is predicted by adding a transit time to the arrival time at the previous reader.

17. The method of claim 14, wherein the results of the search are filtered to remove duplicate entries, poor quality matches, and entries outside a specific time window.

18. The method of claim 14, wherein an ordered list of entries matching the search criteria in ascending/descending order of time and/or quality of search match is displayed on a results display.

19. The method of claim 18, wherein a map showing locations of one or more readers and the entries corresponding with those readers is displayed as a path for the item

20. The system of claim 18, wherein one or more of an item velocity, a predicted path, and projected arrival times at known locations are displayed on the results display.