Extensible object location system and method using multiple references

• US 8,149,169 B1
• Filed: 04/28/2010
• Issued: 04/03/2012
• Est. Priority Date: 05/10/2005
• Status: Active Grant

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Multispectral Solutions Incorporated (Zebra Technologies Corporation)
• Inventors: Ameti, Aitan, Chen, Keming, Fontana, Robert J., Richley, Edward A., Turner, Belinda
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): Nguyen, Nga X
• Application Number:
  US12/769,105
• Time in Patent Office: 706 Days
• Field of Search: 342459-465
• US Class Current: 342/464
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/02213 Receivers arranged in a network for determining the position of a transmitter
• 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: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

An ultra wideband (UWB) or short-pulse RF system is disclosed that can be used to precisely locate or track objects (such as personnel, equipment, assets, etc.) in real-time in an arbitrarily large, physically connected or disconnected, multipath and/or noisy environment. A system implementation includes multiple zones or groups of receivers that receives RF signals transmitted by one or more timing reference tags and one or more objects having associated object tags. Each zone or group may share a common receiver. By combining a multiple reference tag system with a virtual group of receivers, i.e., a zoning technique or system, a cost-effective system can be provided that offers scalability and flexibility to monitor a significantly expanded coverage area.

Claims

1. An extensible zone-based object location system to determine a position of an object in any one of multiple zones of a region, the object having at least one associated object tag configured to transmit a RF signal, the system comprising:

respective groups of receivers that define respective zones, wherein at least two zones share a receiver and wherein each receiver includes a timer to measure an arrival time of RF signals;

a reference tag associated with each zone, wherein each reference tag is configured to transmit a RF signal from a known location within the zone; and

a processing hub configured to obtain time-of-arrival information indicative of arrival times of RF signals transmitted by the object tag and at least one reference tag and configured to determine the position of the object within one of the multiple zones.

2. An extensible zone-based object location system of claim 1, wherein the processing hub is configured to obtain time of arrival information indicative of arrival times of RF signals transmitted by the object tag and two reference tags.

3. An extensible zone-based object location system of claim 2, wherein the respective zones of the two reference tags overlap.

4. An extensible zone-based object location system of claim 3, wherein the position of the object is within an overlapping portion of the respective zones of the two reference tags.

5. An extensible zone-based object location system of claim 2, wherein the respective zones of the two reference tags are adjacent.

6. An extensible zone-based object location system of claim 2, wherein the respective zones of the two reference tags are separated by a distance.

7. An extensible zone-based object location system of claim 2, wherein the multiple zones of a region comprise at least two rooms and wherein the respective zones of the two reference tags correspond to the two rooms to be monitored for object tag positions.

8. An extensible zone-based object location system of claim 2, wherein the position of the object is within the zone of one of the two reference tags and outside of the zone of the other of the two reference tags.

9. An extensible zone-based object location system of claim 1, wherein at least one zone is further defined by a virtual boundary.

10. An extensible zone-based object location system of claim 1, wherein each zone is defined by a RF signal transmission range.

11. An extensible zone-based object location system of claim 10, wherein the receivers of one zone are segmented into at least two virtual zones each defined by a virtual boundary, thereby defining virtual groups of receivers assigned to respective virtual zones.

12. An extensible zone-based object location system of claim 1, wherein the multiple zones of a region comprise at least one virtual zone defined by a virtual boundary, thereby defining a virtual group of receivers assigned to the virtual zone.

13. An extensible object location method to determine a position of an object having an associated object tag configured to transmit a RF signal, the method comprising:

defining zones with respective groups of receivers in a monitored region in which to detect the object, wherein at least two of the groups of receivers share a common receiver;

receiving a RF signal transmitted from a reference tag transmitter from a known location within a first one of the zones at two or more receivers of the group of receivers defining the first zone to determine timing offsets for the two or more receivers of the first zone;

receiving a RF signal transmitted from an object tag of an object at the two or more receivers of the first zone to determine differences in time of arrival for the two or more receivers of the first zone; and

determining the position of the object based on the timing offsets among the two or more receivers of the first zone and the differences in time of arrival of the object tag signal at the two or more receivers of the first zone.

14. An extensible object location method of claim 13, wherein the object tag is configured to transmit an ultra wideband signal.

15. An extensible object location method of claim 13, further comprising:

receiving a RF signal transmitted from a reference tag transmitter from a known location within a second one of the zones at two or more receivers of the group of receivers defining the second zone to determine timing offsets for the two or more receivers of the second zone;

receiving the RF signal transmitted from the object tag of the object at the two or more receivers of the second zone to determine differences in time of arrival for the two or more receivers of the second zone; and

determining the position of the object based on the timing offsets among the two or more receivers of the second zone and the differences in time of arrival of the object tag signal at the two or more receivers of the second zone.

16. An extensible object location method of claim 15, wherein at least one receiver of the first zone is shared as a receiver of the second zone.

17. An extensible object location method of claim 15, further comprising discarding the determined position of the object based on the timing offsets among the two or more receivers of the second zone and the differences in time of arrival of the object tag signal at the two or more receivers of the second zone if the position of the object is determined to be outside the second zone.

18. An extensible object location method of claim 13, wherein defining zones with respective groups of receivers comprises defining at least one zone as a virtual zone defined by a virtual boundary.

19. An extensible object location method of claim 13, wherein defining zones with respective groups of receivers comprises defining at least two zones as virtual zones defined by virtual boundaries on opposing sides of a barrier, wherein the virtual boundaries are configured so that each receiver of each respective virtual zone has a direct line-of-sight throughout each respective virtual zone and to the reference tag transmitter for the virtual zone.

20. An extensible object location method to determine a position of an object having an associated object tag configured to transmit a RF signal, the method comprising:

providing successive receivers to at least partially encircle a monitored region in which to detect the object and configured to receive RF signals;

providing a reference tag transmitter substantially between each of the receivers and configured to transmit a RF reference signal from a known location;

receiving the RF reference signal at two or more of the receivers thereby to determine timing offsets for the two or more receivers;

determining a timing offset for at least one of the receivers based on timing offsets of the at least two other receivers;

transmitting a RF object tag signal from the monitored region;

receiving the RF object tag signal at the two or more receivers; and

determining the position of the object based on the timing offsets and differences in time of arrival of the RF object tag signal at the two or more receivers.

21. The method of claim 20, wherein the RF signals comprises ultra wideband signals.