Use of range-rate measurements in a fusion tracking system via projections

Patent metadata

Field	Value
Publication number	US-10175348-B2
Application number	US-201514878558-A
Country	US
Kind code	B2
Filing date	Oct 8, 2015
Priority date	Oct 8, 2014
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

A target is located and a track is associated with the target in the fusion coordinate system. An estimate/prediction of the target's velocity is developed within the tracker, as well as , a vector representing the distance from the fusion center to the target as estimated by the tracker, and , a vector representing the known distance from the fusion center to the sensor. The sensor's range vector, (the distance from the sensor to the target as predicted by the tracker) is transformed to fusion coordinates. Using the sensor's range vector, normalized to unit length, in fusion coordinates and the estimated target's velocity, an estimate of the target's speed projected in the direction of is derived. The estimated range-rate is compared per update to the sensor's measured range-rate in the form of an error measurement. The error is then used to correct the track's velocity prediction.

First claim

What is claimed is:

1. A method comprising the steps of:
providing a system comprising a plurality of radars each configured to obtain sensor data for at least one target, and a processor in communication with the plurality of radars, wherein the processor comprises a tracking filter;
obtaining, with the plurality of radars, sensor data regarding the target, wherein the sensor data comprises a range-rate measurement;
transmitting the obtained sensor data to the processor;
generating, by the processor utilizing a pulse-repetition interval of the system, a range hypothesis and a range-rate hypothesis for the target;
converting, by the processor, at least some of the obtained sensor data from the plurality of radars to a common coordinate system having an origin;
predicting, by the tracking filter using the obtained sensor data, a first track state for the target, wherein said prediction comprises an estimate of a position of the target and an estimate of a velocity of the target;
determining a a range vector to the target from each radar of the plurality of radars to obtain a first estimated position with respect to each radar of the plurality of radars, wherein the range vector is described in terms of the common coordinate system and is determined based on a vector from the origin to a respective radar of each of the plurality of radars and on a vector from the origin to the estimated position of the target;
determining in the common coordinate system, using the determined range vector, an estimate of a velocity of the target in the direction of each radar of the plurality of radars by projecting the estimated velocity of the target onto the range vector for each range vector respectively associated with a radar of the plurality of radars;
determining an error measurement by comparing the estimated velocity in the direction of each radar of the plurality of radars to the range-rate hypothesis for the target; and
updating the predicted first track state with the determined error measurement to generate a second track state for the target.

2. The method of claim 1 , wherein the plurality of radars are in wireless communication with the processor.

3. The method of claim 1 , wherein the obtained sensor data comprises one or more of the following: range of the target, range-rate of the target, azimuth angle of the target, and an elevation angle of the target.

4. The method of claim 1 , wherein the common coordinate system is a Cartesian coordinate system.

5. The method of claim 1 , wherein the step of determining a distance of each radar of the plurality of radars to the target comprises the formula
= −

where is the distance from each radar to the target, is a predicted distance from the processor to the target, and is the distance from the processor to the radar.

6. The method of claim 1 , wherein the estimate of a velocity of the target in the direction of each radar of the plurality of radars is determined using the formula

R
.

=

V
_

·

R
_



R
_



=

V
_

·

(

T
_

-

S
_

)



T
_

-

S
_



where is the distance from each radar to the target, is a predicted distance from the processor to the target, and is the distance from the processor to a radar.

7. The method of claim 1 , wherein said processor comprises a Kalman filter.

8. A system comprising:
a processor; and
a plurality of radars each configured to obtain sensor data for at least one target, wherein the sensor data comprises a range-rate measurement, and further wherein the plurality of radars are configured to transmit obtained sensor data to the processor;
wherein the processor is configured to: (i) generate a range hypothesis and a range-rate hypothesis for the target utilizing obtained sensor data; (ii) convert at least some of the obtained sensor data from the plurality of radars to a common coordinate system having an origin; (iii) predict a first track state for the target, wherein said prediction comprises an estimate of a position of the target and an estimate of a velocity of the target; (iv) determine a range vector from each of the plurality of radars to the target to obtain a first estimated position with respect to each radar of the plurality of radars, wherein the range vector is described in terms of the common coordinate system and is determined based on a vector from the origin to a respective radar of each of the plurality of radars and on a vector from the origin to the estimated position of the target; (v) determine in the common coordinate system an estimate of a velocity of the target in the direction of each of the plurality of radars, by projecting the estimated velocity of the target onto the range vector for each range vector respectively associated with a radar of the plurality of radars; (vi) determine an error measurement by comparing the estimated velocity to the range-rate hypothesis for the target; and (vii) update the predicted first track state with the determined error measurement to generate a second track state for the target.

9. The system of claim 8 , further comprising a communications network between the processor and one or more of the plurality of radars.

10. The system of claim 8 , wherein the obtained sensor data comprises one or more of the following: range of the target, range-rate of the target, azimuth angle of the target, and an elevation angle of the target.

11. The system of claim 8 , wherein the common coordinate system is a Cartesian coordinate system.

12. The system of claim 8 , wherein the processor is configured to determine a distance to the target using the formula
= −

where is the distance from the radar to the target, is a predicted distance from the processor to the target, and is the distance from the processor to the radar.

13. The system of claim 8 , wherein the processor is configured to estimate the velocity of the target in the direction of the radar using the formula

R
.

=

Assignees

• Src Inc

Inventors

• Clark Barry L
• Keckler Andrew D
• Houman Thomas A

Classifications

• G01S13/58

  Velocity or trajectory determination systems; Sense-of-movement determination systems · CPC title

• G01S13/87

  Combinations of radar systems, e.g. primary radar and secondary radar · CPC title

• G01S13/42 Primary

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S13/46) · CPC title

• G01S13/723

  by using numerical data · CPC title