Extensible object location system and method using multiple references

Patent metadata

Field	Value
Publication number	US-9360547-B2
Application number	US-201213436029-A
Country	US
Kind code	B2
Filing date	Mar 30, 2012
Priority date	May 10, 2005
Publication date	Jun 7, 2016
Grant date	Jun 7, 2016

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.

First claim

We claim:

1. A location system comprising:
an object tag associated with an object and configured to transmit a radio frequency signal within a monitored region;
a plurality of reference tags each associated with a respective zone of a plurality of zones within the monitored region, each reference tag configured to transmit a reference signal and wherein each reference tag is positioned at a known reference location within the monitored region;
a plurality of receivers positioned in or around the monitored area at known receiver locations, wherein the plurality of receivers are configured to receive the object tag radio frequency signal and the reference signal, wherein each receiver comprises a free running digital counter configured to detect an object time of arrival of the object tag radio frequency signal and a reference time of arrival of the reference signal; and
a processing hub comprising a common source clock, disposed in wired communication with the free running digital counters through daisy chained cables, wherein the common source clock is configured to synchronize the free running digital counters in frequency and lock the free running digital counters in a relative phase relationship, wherein the processing hub is configured to receive the object time of arrival data of the object tag radio frequency signal and the reference tag signal and determine an object location based on the object time of arrival and phase offsets associated with the respective receivers of the plurality of receivers, wherein the phase offsets are determined based on the reference time of arrival at the respective receivers, the known receiver locations, and the known reference location, wherein the processing hub is further configured to define the respective zones among the plurality of zones, prior to determining the object location, wherein the respective zones comprise a group of receivers and the respective reference tag, wherein at least one receiver of the group of receivers is common to at least two of the plurality of zones, wherein the determination of the object location is within one of the respective zones.

2. The location system of claim 1 , wherein the defining a respective zone is based on a transmission range of the reference tag.

3. The location system of claim 1 , wherein the detecting an object time of arrival of the object tag radio frequency signal and a reference time of arrival of the reference signal comprises latching or recording count values of the free running digital counter.

4. The location system of claim 1 , wherein the determining the object location comprises a gradient search to minimize an error function.

5. The location system of claim 1 , wherein the phase offsets are determined prior to the determining the object location.

6. The location system of claim 1 , wherein the object tag comprises an ultra-wide band transmitter, wherein the radio frequency signal is ultra-wide band.

7. The location system of claim 1 , wherein the radio frequency signal or the reference signal comprises a tag identification.

8. A method comprising:
transmitting a radio frequency signal, from an object tag associated with an object, within a monitored region;
transmitting a reference signal, from one of a plurality of reference tags, wherein each of the plurality of references tag is associated with a zone within the monitored region and is positioned at a known reference location within the monitored region;
receiving the object tag radio frequency signal and the reference signal, at a plurality of receivers positioned in or around the monitored area at known receiver locations, wherein each receiver comprises a free running digital counter configured to detect an object time of arrival of the object tag radio frequency signal and a reference time of arrival of the reference signal;
synchronizing, by a common clock source of a processing hub, the free running digital counters in frequency and locking the free running digital counters in a relative phase relationship, wherein the common clock source is disposed in wired communication with the free running digital counters through daisy chained cables;
receiving, by the processing hub, the object time of arrival data of the object tag radio frequency signal and the reference tag signal;
determining an object location based on the object time of arrival and phase offsets associated with the respective receivers of the plurality of receivers, wherein the phase offsets are determined based on the reference time of arrival at the respective receivers, the known receiver locations, and the known reference location; and
defining respective zones among the plurality of zones, prior to determining the object location, wherein the respective zones comprise a group of receivers and a respective reference tag, wherein at least one receiver of the group or receivers is common to at least two of the plurality of zones, wherein the determination of the object location is within one of the respective zones.

9. The method of claim 8 , wherein the defining a respective zone is based on a transmission range of the reference tag.

10. The method of claim 8 , wherein the detecting an object time of arrival of the object tag radio frequency signal and a reference time of arrival of the reference signal comprises latching or recording count values of the free running digital counter.

11. The method of claim 8 , wherein the determining the object location comprises a gradient search to minimize an effort function.

12. The method of claim 8 , wherein the phase offsets are determined prior to the determining the object location.

13. The method of claim 8 , wherein the object tag comprises a ultra-wide band transmitter, wherein the radio frequency signal is ultra-wide band.

14. The method of claim 8 , wherein the radio frequency signal or the reference signal comprises at least a tag identification.

Assignees

• Ameti Aitan
• Chen Keming
• Fontana Robert J
• Richley Edward A
• Turner Belinda
• Zih Corp

Inventors

• Ameti Aitan
• Chen Keming
• Fontana Robert J
• Richley Edward A
• Turner Belinda

Classifications

• G01S5/10 Primary

  Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements {, e.g. omega or decca systems}(G01S5/12 takes precedence {; beacons and receivers cooperating therewith G01S1/306, G01S1/308}) · CPC title

• G01S5/021 Primary

  Calibration, monitoring or correction (G01S5/0252 takes precedence) · CPC title

• G01S5/06 Primary

  Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements (G01S5/12 takes precedence) · CPC title

• G01S5/02213

  Receivers arranged in a network for determining the position of a transmitter · CPC title

• G01S5/0221

  Receivers · CPC title