Wireless localisation system

• US 10,338,194 B2
• Filed: 09/01/2016
• Issued: 07/02/2019
• Est. Priority Date: 07/04/2008
• Status: Active Grant

• Current Assignee: Commonwealth Scientific & Industrial Research Organisation (Commonwealth Of Australia As Represented By Department Of Industry, Innovation, Climate Change, Science, Research And Tertiary Education)
• Original Assignee: Commonwealth Scientific & Industrial Research Organisation (Commonwealth Of Australia As Represented By Department Of Industry, Innovation, Climate Change, Science, Research And Tertiary Education)
• Inventors: Hedley, Mark, Humphrey, David Eric
• Primary Examiner(s): McGue, Frank J
• Application Number:
  US15/255,011
• Publication Number:
  US 20160370455A1
• Time in Patent Office: 1,034 Days
• Field of Search: 342387
• CPC Class Codes: G01S 13/876 Combination of several spaced transponders or reflectors of known location for determining the position of a receiver G01S13/874 takes precedence
• 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 5/017 Detecting state or type of motion
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0226 Transmitters
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

Disclosed is method of computing a round trip delay between a pair of nodes, the method comprising transmitting at least one beacon at a known transmit time from each of the nodes; measuring the times-of-arrival of the beacons at other of the nodes; and estimating a round trip delay between the nodes from the measured times-of-arrival and the transmit times; and correcting the round trip delay for either or both of a frequency offset between the nodes and relative motion between the nodes.

Claims

1. A method of estimating the location of a mobile object using a plurality of anchor nodes, the method comprising:

synchronising said plurality of anchor nodes;

measuring a plurality of times-of-arrival of beacons transmitted from said object to respective said anchor nodes; and

estimating the location of said object relative to said anchor nodes using said measured times-of-arrival, corrected for a propagation delay at each said anchor node,

wherein the step of estimating the location of said object relative to said anchor nodes comprises the sub-steps of;

subtracting respective propagation delays from each of said plurality of measured times-of-arrival to obtain respective pseudo-ranges forming a set of obtained pseudo-ranges;

estimating locations of said object and corresponding errors in respective said location estimates, wherein each estimated location is determined from a subset of the obtained pseudo-ranges, and wherein each subset of the obtained pseudo-ranges excludes one pseudo-range from the set of obtained pseudo-ranges; and

discarding each of the obtained pseudo-ranges whose exclusion gave an error estimate that is less than a threshold; and

estimating the location of said object from undiscarded pseudo-ranges, the undiscarded pseudo-ranges being those of the obtained pseudo-ranges that have not been discarded.

2. The method according to claim 1, wherein the step of synchronising said plurality of anchor nodes comprises the sub-steps of:

measuring a plurality of trip delays of beacons transmitted between said anchor nodes;

correcting said trip delays for propagation delays at said anchor nodes and frequency offsets between local clocks at respective said anchor nodes; and

determining a time offset of each said local clock from said corrected trip delays.

3. The method according to claim 1, wherein said threshold is an error estimate of a location estimate determined from all of the obtained pseudo-ranges.

4. The method according to claim 1, wherein said estimating sub-step comprises minimising a weighted sum over said anchor nodes of a squared difference between each pseudo-range and a distance between a candidate location and the location of a corresponding anchor node.

5. The method according to claim 1, wherein each of said error estimates in the estimated locations comprises an estimate of a pseudo-range error and a term relating the pseudo-range error to said error in the estimated location.

6. The method according to claim 1, wherein the discarding of the pseudo-ranges is performed until the number of the undiscarded pseudo-ranges reaches a minimum number.

7. The method of claim 1, wherein the step of estimating the location of said object relative to said anchor nodes further comprises the sub-step of estimating an offset common to all said obtained pseudo-ranges.