POSITIONING SYSTEM

• US 20170131383A1
• Filed: 01/26/2017
• Published: 05/11/2017
• Est. Priority Date: 03/03/2014
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Bartov, Avishai, Zlotnick, Yossi
• Granted Patent: US 10,942,250 B2
• Time in Patent Office: Days
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01S 11/16 using difference in transit time between electrical and acoustic signals
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• 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 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0226 Transmitters
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 56/001 Synchronization between nodes

Abstract

An ultrawide band two-way ranging based positioning system includes a number of active tags each having a position, and a number of beacons configured for location of a position of a tag of the plurality of active tags. The active tags and the beacons are synchronized continuously to a common time base.

Claims

1. An ultrawide band two-way ranging based positioning system, comprising:

a plurality of active tags each having a position; and

a plurality of beacons configured for location of a position of a tag of the plurality of active tags;

wherein the plurality of active tags and the plurality of beacons are synchronized continuously to a common time base.

2. The positioning system of claim 1, wherein each active tag in the system has a globally designated window for two-way ranging polls between it and at least one of the plurality of beacons.

3. The positioning system of claim 1, wherein each beacon of the plurality of beacons listens for a two-way ranging poll from a tag of the plurality of active tags in a predefined window.

4. The positioning system of claim 1, wherein the plurality of active tags has a global reporting time slot.

5. The positioning system of claim 1, wherein each tag of the plurality of active tags is configured to determine its position based on two-way ranging between it and at least one beacon of the plurality of beacons.

6. The positioning system of claim 5, wherein each tag of the plurality of tags is configured to determine its position based on two-way ranging between it and at least three beacons.

7. The positioning system of claim 5, and further comprising:

a processing unit coupled via a data network to the plurality of beacons, the beacons configured to receive tag positions from the plurality of active tags, and the processing unit configured to receive position information of the plurality of active tags from the plurality of beacons.

8. The positioning system of claim 7, wherein the processing unit is further configured to update positions of the plurality of tags at a rate dependent upon determined conditions of the tags.

9. A method of determining a position of an active tag using a system comprising an application server and a plurality of fixed location beacons, comprising:

providing a common time base for the plurality of fixed location beacons;

providing a synchronization message from each of the plurality of fixed location beacons;

registering the active tag to the common time base based on the synchronization message;

ranging the active tag to at least a portion of the plurality of beacons; and

reporting a position of the active tag to at least a beacon of the plurality of beacons.

10. The method of claim 9, and further comprising drift compensating the plurality of beacons and the active tag, using an internal clock count B_cⁿ of a beacon synchronization message and an internal clock count T_cⁿ of the active tag for a current update cycle n of the system.

11. The method of claim 10, wherein drift compensating comprises:

determining a correction factor D to correct for clock drift versus the common time base.

12. The method of claim 11, wherein determining a correction factor is performed using the formula

13. The method of claim 12, wherein time of flight between a beacon and the active tag is T_f, wherein a response delay between a beacon and an active tag is T_d, and wherein the correction factor is applied to a two-way ranging round trip flight time as T_RT=2T_f+T_d*D.

14. The method of claim 9, wherein registering the active tag comprises:

listening by the active tag for synchronization messages from the plurality of beacons;

sending a registration message upon receipt of a synchronization message from a beacon of the plurality of beacons;

receiving a confirmation message from the beacon of the plurality of beacons at the tag; and

initiating listening for a tag position report in a tag position report time slot.

15. The method of claim 9, wherein providing a synchronization message comprises providing the synchronization message within a range of predetermined beacon time synchronization time slots in an update cycle for the system.

16. The method of claim 9, wherein registering the active tag comprises registering the active tag within a range of predetermined tag registration time slots in an update cycle for the system.

17. The method of claim 16, wherein ranging the active tag comprises ranging the active tag within a range of time slots in the update cycle after the tag registration time slots.

18. The method of claim 9, wherein ranging the active tag comprises:

issuing from the active tag a two-way ranging signal;

receiving at the active tag return signals from at least three beacons of the plurality of beacons; and

calculating a position of the active tag at the active tag using the common time base and the received return signals.

19. The method of claim 18, wherein issuing a two-way ranging signal comprises issuing to a determined one of the plurality of beacons.

20. The method of claim 19, wherein ranging comprises ranging to more than one beacon of the plurality of beacons within an update cycle of the system.

21. The method of claim 18, wherein issuing two-way ranging signals is performed within a globally designated window in an update cycle of the system.

22. The method of claim 9, and further comprising:

connecting the plurality of beacons and the application server with a wireless communication network; and

transferring mobile tag information from the plurality of beacons to the application server.

23. The method of claim 9, wherein the system monitors a plurality of tags, and further comprising updating at least one tag of the plurality of tags at a rate slower than other tags, depending upon determined conditions of the at least one tag.

24. A positioning system, comprising:

a plurality of active tags;

a plurality of fixed position beacons in communication with the plurality of active tags over an ultrawide band two-way ranging based network;

wherein each active tag of the plurality of active tags in the system has a globally designated window for two-way ranging polls between it and at least one of the plurality of beacons, wherein the plurality of beacons accepts two-way ranging polls within the globally designated window, and wherein the plurality of active tags report positions within a global reporting time slot.