Method for tracking and detecting turns of maneuvering targets

• US 5,999,117 A
• Filed: 06/16/1998
• Issued: 12/07/1999
• Est. Priority Date: 06/16/1998
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Engel, Stephen Joseph
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US09/098,250
• Time in Patent Office: 539 Days
• Field of Search: 342/95, 342/96, 342/97, 342/105, 342/107, 342/110, 342/114, 342/115, 342/135, 342/136, 342/140, 342/195
• US Class Current: 342/95
• CPC Class Codes: G01S 13/66 Radar-tracking systems; Analogous systems

Abstract

A method for detecting and tracking turns of a maneuvering target comprises the steps of determining first and second radar information of the maneuvering target. The first and second radar information and a set of target speeds are used to determine a set of turn radii for the maneuvering target. The first and second radar information and a set of target arc speeds are used to determine a second set of turn radii for the maneuvering target. The set of turn radii and the set of target speeds define a speed-radius curve, and the second set of turn radii and the set of target arc speeds define an arc speed-radius curve. An intersection of the speed-radius and arc speed-radius curves is located, and the intersection is used to determine whether the maneuvering target has made a turn.

Claims

1. A method for processing radar returns to detect the presence of a maneuvering target, comprising the steps of:

a) receiving first radar information, which comprises a first range, a first range rate, and a first time;

b) receiving second radar information, which comprises a second range, a second range rate, and a second time;

c) providing a set of potential target speeds, wherein each of the set of target speeds is not less than the first range rate and not less than the second range rate;

d) determining a set of turn radii, wherein each of the set of turn radii is defined by one of the set of potential target speeds and the first and second radar information, and wherein the set of turn radii and the set of potential target speeds define a speed-radius curve;

e) providing a set of potential target arc speeds, wherein each of the set of potential target arc speeds is not less than the first range rate and not less than the second range rate;

f) determining a second set of turn radii, wherein each of the second set of turn radii is defined by one of the set of potential target arc speeds and the first and second radar information, and where the second set of turn radii and the set of potential target arc speeds define an arc speed-radius curve;

g) locating the point of minimal difference between the speed-radius curve and the arc speed-radius curve; and

h) comparing the minimal difference between the speed radius curve and the arc speed radius curve to a predetermined window of interest indicative of the presence of a maneuvering target.

2. The method as recited in claim 1 further comprising the step of repeating steps a-h with respect to additional radar information to derive additional speed radius curves and arc speed radius curves, until an intersection thereof is detected.

3. The method of claim 2 wherein each of the set of turn radii is determined by ##EQU2## where R₁ =the first range, R₁ =the first range rate, S=one of the set of target speeds,

R₂ =the second range, R₂ =the second range rate, and r=a turn radius.

4. The method of claim 3 wherein each of the second set of turn radii is determined by

5. The method of claim 1 further comprising the step of ignoring portions of the speed-radius and arc speed-radius curves that fall outside the predetermined window of interest, wherein the predetermined window of interest is defined by a predetermined set of speeds of interest and a predetermined set of turn radii of interest.

6. The method of claim 1 further comprising the step of ignoring portions of the speed-radius curve and the arc speed-radius curve where slopes of the curves are within a predetermined threshold around zero.

7. The method of claim 1 wherein the first and second position information further comprises a first azimuth and a second azimuth;

and further comprising the step of redetermining the first and second ranges using the first and second azimuths, wherein the redetermined ranges are distances from a virtual observation point to the target.

8. The method of claim 7 wherein each of the set of turn radii is determined by:

##EQU3## where R_1new =the redetermined first range, R₁ =the first range rate, S=one of the set of target speeds, R_2new =the redetermined second range, R₂ =the second range rate, and r=a turn radius.

9. The method of claim 7 wherein each of the second set of turn radii is determined by:

space="preserve" listing-type="equation">S(arc)=r[abs(a cos ((D.sup.2 +r.sup.2 -R.sub.1new.sup.2)/2Dr)±

a cos ((D.sup.2 +r.sup.2 -R.sub.2new.sup.2)/2Dr))]/Δ

t

where D=[r² +R_1new² -2rR_1new (±

(1-(R₁ /S)²)^1/2)]^1/2, S(arc)=one of the set of target arc speeds, and Δ

t=a difference between the first time and the second time.

10. A method for tracking and detecting a turn of a maneuvering target comprising the steps of:

a) determining a target radar report, including a known speed;

b) determining a plurality of second radar reports;

c) pairing the target radar report with each of the plurality of second radar reports to form report pairs;

d) providing a set of target speeds;

e) determining a set of turn radii for each report pair, wherein each of the set of turn radii is determined using one of the set of target speeds and one of the report pairs, wherein the set of turn radii for each report pair and the set of target speeds define a speed-radius curve for each report pair;

f) providing a set of target arc speeds;

g) determining a second set of turn radii for each report pair, wherein each of the second set of turn radii is determined using one of the set of target arc speeds and one of the report pairs, wherein the second set of turn radii for each report pair and the set of target arc speeds define an arc speed-radius curve for each report pair;

h) locating a solution report pair, the solution report pair being an intersection of at least one of the speed-radius curves and at least one of the arc speed-radius curves at the known speed; and

i) using the solution report pair to detect whether the target has made a turn.

11. The method of claim 10 wherein the target radar report further comprises a first range, a first range rate, and a first time;

and wherein each of the plurality of second radar reports comprises a second range, a second range rate, and a second time.

12. The method of claim 11 wherein each of the set of turn radii for each radar report is determined by ##EQU4## where R₁ =the first range, R₁ =the first range rate, S=one of the set of target speeds,

R₂ =the second range, R₂ =the second range rate, and r=a turn radius.

13. The method of claim 12 wherein each of the second set of turn radii for each radar report is determined by

14. The method of claim 10 further comprising the step of ignoring portions of the speed-radius and arc speed-radius curves that fall outside a predetermined window of interest, wherein the window of interest is defined by a predetermined set of target speeds of interest and a predetermined set of turn radii of interest.

15. The method of claim 10 further comprising the step of ignoring portions of the speed-radius curves and the arc speed-radius curves where slopes of the curves are within a predetermined threshold around zero.