Distinguishing RFID tags using motion data

• US 9,489,655 B1
• Filed: 08/25/2014
• Issued: 11/08/2016
• Est. Priority Date: 08/25/2014
• Status: Active Grant

• Current Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Original Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Inventors: Lecky, Ned
• Primary Examiner(s): Le, Thien M
• Assistant Examiner(s): Taylor, April
• Application Number:
  US14/467,760
• Time in Patent Office: 806 Days
• Field of Search: 235/385
• US Class Current: 1/1
• CPC Class Codes: G06K 7/10128 the step consisting of detection of the presence of one or more record carriers in the vicinity of the interrogation device
• CPC Class Codes: G06K 7/10366 the interrogation device being adapted for miscellaneous applications
• CPC Class Codes: G06Q 10/087 Inventory or stock management, e.g. order filling, procurement or balancing against orders
• CPC Class Codes: G06Q 10/0875 Itemisation or classification of parts, supplies or services, e.g. bill of materials

Abstract

Disclosed are various embodiments for verifying that items have been correctly retrieved to fulfill orders or shipments. A plurality of radio frequency identification (RFID) tags may be energized with an electromagnetic field emitted from an RFID reader, wherein individual ones of the plurality of RFID tags comprise a unique identifier. A signal strength reader may detect a change in a signal strength corresponding to the RFID tag. The RFID reader may then identify the unique identifier of the RFID tag in response to detecting the change in the signal strength corresponding to the RFID tag.

Claims

1. A system, comprising:

a plurality of radio frequency identification (RFID) tags each comprising a unique identifier, a radio receiver, and a radio transmitter, each of the plurality of RFID tags associated with a corresponding item;

an RFID tag identification device mounted to a robotic picker, wherein the RFID tag identification device comprises an RFID reader and a signal strength meter; and

at least one computing device configured to at least;

identify an item associated with a unique identifier in response to the RFID reader receiving the unique identifier transmitted from an RFID tag, wherein the at least one computing device selects the RFID tag based at least in part on a change in a signal strength of a transmission containing the unique identifier transmitted from the RFID tag measured by the signal strength meter;

determine whether the item is included in a pick list associated with the robotic picker located near the RFID tag;

send an electronic message to the robotic picker in response to a determination that the item is not included in the pick list; and

record that the item has been picked in response to a determination that the item is included in the pick list.

2. The system of claim 1, wherein the at least one computing device is further configured to determine the change in the signal strength of the transmission containing the unique identifier transmitted from the RFID tag based at least in part on a series of measurements taken by the signal strength meter over a period of time.

3. The system of claim 1, wherein the at least one computing device, in order to determine the change in the signal strength of the transmission containing the unique identifier transmitted from the RFID tag, is further configured to:

generate a trend line representing a series of measurements taken by the signal strength meter;

calculate a slope of the trend line; and

determine the change in the signal strength based the slope of the trend line.

4. The system of claim 1, wherein the at least one computing device is further configured to at least filter a response of the RFID tag based at least in part on a magnitude of the change in the signal strength of the response measured by the signal strength meter.

5. The system of claim 1, wherein the signal strength meter is configured to disregard the change in the signal strength of the response transmitted from the RFID tag in response to a determination that a magnitude of the change in the signal strength is below a threshold value.

6. The system of claim 1, wherein the RFID tag identification device is mounted to the robotic picker to minimize interference of the robotic picker with respect to the signal strength of the unique identifier transmitted from the RFID tag.

7. A system, comprising:

a radio frequency identification (RFID) reader configured to energize an RFID tag;

a signal strength meter mounted to a robotic picker, wherein the signal strength meter is configured to measure a signal strength of a response transmitted from the RFID tag;

at least one computing device configured to at least;

assign a pick list to the robotic picker, the pick list comprising at least one pick item and a unique identifier of an RFID tag corresponding to the at least one pick item;

determine whether the RFID tag energized by the RFID reader is moving based at least in part on a change in the signal strength of the response transmitted from the RFID tag measured by the signal strength meter during an event;

compare the change in the signal strength of the response of the moving RFID tag with an expected change in the signal strength during the event;

select a unique identifier of the moving RFID tag based at least in part on a comparison of the change in the signal strength of the response with the expected change in the signal strength;

determine whether an item retrieved by the robotic picker corresponds to the at least one pick item in the pick list based at least in part on a comparison of the unique identifier of the selected moving RFID tag with the unique identifier of the RFID tag corresponding to the at least one pick item in the pick list; and

send a message to an electronic device located in proximity to the robotic picker in response to a determination that the item does not correspond to the at least one pick item in the pick list.

8. The system of claim 7, wherein the change in the signal strength of the response is based at least in part on a series of measurements of the signal strength by the signal strength meter over a period of time.

9. The system of claim 7, wherein the RFID reader is configured to disregard a response transmitted from the RFID tag that is below a threshold signal strength.

10. The system of claim 7, wherein the signal strength meter is configured to disregard the change in the signal strength of the response transmitted from the RFID tag in response to a determination that a magnitude of the change in the signal strength is below a threshold value.

11. The system of claim 7, wherein the message further comprises a description of the at least one pick item in the pick list.

12. The system of claim 11, wherein the description of the at least one pick item in the pick list comprises an image of the at least one pick item in the pick list.

13. A method, comprising:

energizing a radio frequency identification (RFID) tag with an electromagnetic field emitted from an RFID reader, wherein the RFID tag comprises a unique identifier and transmits the unique identifier in response to being energized;

retrieving, via a robotic picker, an item from an item storage location, wherein the RFID tag is attached to the item;

detecting, via a signal strength meter attached to the robotic picker, a change in a signal strength of a transmission containing the unique identifier transmitted from the RFID tag during an event;

determining, via a computing device, whether the detected change in the signal strength of the transmission containing the unique identifier transmitted from the RFID tag matches an expected change in the signal strength during the event;

identifying, via a computing device, the unique identifier of the RFID tag in response to the detected change in the signal strength of the transmission containing the unique identifier transmitted from the RFID tag matching the expected change in the signal strength;

determining, via the computing device, whether the transmission containing the unique identifier transmitted from the RFID tag attached to the item corresponds to a pick item included in a pick list assigned to the robotic picker; and

marking, via the computing device, the pick item as picked in response to determining that the unique identifier corresponds to the pick item included in the pick list assigned to the robotic picker.

14. The method of claim 13, further comprising determining, via the computing device, a trajectory of the RFID tag based at least in part on the change in the signal strength of the transmission containing the unique identifier transmitted from the RFID tag.

15. The method of claim 14, wherein:

the RFID tag comprises a sensor that measures at least one of an acceleration or a velocity of the RFID tag;

the RFID tag is further configured to transmit at least one of the acceleration or the velocity; and

the trajectory of the RFID tag is further based at least in part on at least one of the acceleration or the velocity.

16. The method of claim 14, wherein identifying, via the computing device, the unique identifier transmitted from the RFID tag is further performed in response to determining that the RFID tag has a trajectory.

17. The method of claim 13, further comprising filtering, via the computing device, a response of the RFID tag based at least in part on a magnitude of the change in the signal strength of the response measured by the signal strength meter.

18. The method of claim 13, further comprising disregarding, via the computing device, the RFID tag based at least in part on a transmission signal strength of a response of the RFID tag.

19. The method of claim 13, wherein the signal strength meter and the RFID reader are components of the computing device and the computing device is attached to the robotic picker.

20. The method of claim 13, wherein the signal strength meter is attached to the robotic picker to minimize interference of the robotic picker with respect to the signal strength of the unique identifier transmitted from the RFID tag.