Template updated boost algorithm

• US 8,130,137 B1
• Filed: 10/08/2007
• Issued: 03/06/2012
• Est. Priority Date: 07/26/2005
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Boka, Jeffrey B., Mookerjee, Purusottam, Harcourt, Michael J., Luu, Thu-Van
• Primary Examiner(s): Gregory, Bernarr E
• Application Number:
  US11/868,554
• Time in Patent Office: 1,611 Days
• Field of Search: 89/11.1, 342/27, 342/28, 342/59, 342 61- 68, 342 73-103, 342104-115, 342165-175, 342/195, 342/118, 342/146, 342/147, 342/158, 701 3- 18, 703/6, 703/7, 703/8, 244 31- 33
• US Class Current: 342/62
• CPC Class Codes: F41G 7/007 Preparatory measures taken before the launching of the guided missiles
• CPC Class Codes: F41G 7/301 Details
• CPC Class Codes: F41G 7/303 Sighting or tracking devices especially provided for simultaneous observation of the target and of the missile
• CPC Class Codes: F42B 15/01 Arrangements thereon for guidance or control steering arrangements F42B10/60; aircraft flight control B64C; guidance systems other than those installed aboard F41G7/00, F41G9/00; locating by use of radio or other waves G01S; flight control in general G05D1/00; computer aspects G06]
• CPC Class Codes: G01S 13/723 by using numerical data

Abstract

A method and a system for sensing a boosting target missile, estimate position and velocity and boost acceleration parameters of the target missile, and control an interceptor missile to the target missile. A boost-phase missile target state estimator estimates at least acceleration, velocity, and position using an acceleration template for the target vehicle. The nominal template is incorporated into an extended Kalman filter which corrects the nominal template acceleration with the filter states to predict future thrust acceleration, velocity and position. The correction can compensate for motor burn variations and missile energy management (lofted/depressed trajectory).

Claims

1. A method for attacking a target missile in its boost state, said method comprising the steps of

sensing the target and generating signals representative of a target position,

from said signals representative of the target position, estimating states of the boosting target using nominal templates comprising profiles of (a) thrust acceleration, (b) altitude, (c) speed, and (d) angle-of-attack as a function of time after launch of said target, wherein all of said profiles are updated using states of a filter to correct for template indexing error, template boost acceleration variations, and template angle-of-attack variations,

wherein the estimated target states are unencumbered by motor burn boost variations and provide accurate determination of an end-of-boost of said target,

applying said target states to determine target acceleration, and

controlling firing and guidance of an interceptor missile in response to said estimated target states and said target acceleration.

2. The method of claim 1, wherein the step of controlling firing and guidance of an interceptor missile further comprises processing a location of an interceptor missile together with target state information to generating interceptor missile commands for application to the interceptor missile in flight.

3. The method of claim 1, wherein said filter is a Kalman filter.

4. A method for attacking a target missile in its boost state, said method comprising the steps of

sensing the target and generating signals representative of target position,

from said signals representative of the target position, estimating a state of said target, including position and velocity, and at least one of (a) variation in engine burn rate, (b) error in time after launch and (c) error in angle of attack,

said method comprising the further steps of:

providing a template representing nominal values of acceleration of said target due to engine thrust, speed, altitude, and angle-of-attack, as a function of time after target launch;

calculating target altitude from said target-position signals to generate a calculated target altitude;

reading from said template at least a nominal value of time after launch, acceleration, speed, and angle of attack corresponding to said calculated target altitude;

initializing the state estimate and associated covariances of a filter with said nominal value of time after launch, acceleration, speed, and angle of attack corresponding to said calculated target altitude;

propagating in time the state estimates and covariances of said filter to generate a time-updated vector of state estimates representing a predicted state of the target, using at least one of said template profile information updated by (a) variation in engine burn rate, (b) error in time after launch and (c) error in angle of attack;

updating said states using measurements to produce a vector of measurement updated state estimates and covariances of the target, including position and velocity, and at least one of (a) variation in engine burn rate, (b) error in time after launch and (c) error in angle of attack; and

applying said states to determine target acceleration, and

controlling firing and guidance of an interceptor missile in response to said estimated states and said target acceleration.

5. A method according to claim 4, wherein said step of providing a template representing nominal values of acceleration of said target comprises the step of providing a template representing nominal values of boost acceleration.

6. The method of claim 4, further comprising, subsequent to said step of calculating target altitude, establishing a time index by entering said template at said calculated target altitude.

14. The method of claim 4, wherein said filter is an extended Kalman filter.

7. A method for attacking a target missile in its boost state, said method comprising the steps of:

sensing the target and generating target-position information representative of the target position;

from said target-position information representative of the target position, estimating a state of a boosting target by the steps of;

providing a template representing nominal values of acceleration of said target as a function of time after target launch;

calculating target altitude from said target-position information to generate calculated target altitude;

reading from said template nominal value of at least one of (a) time after launch, (b) acceleration, (c) speed, and (d) angle of attack corresponding to said calculated target altitude;

initializing the state estimate and associated covariances of filter with said nominal value corresponding to said calculated target altitude, to thereby generate state estimates and covariances of said filter;

propagating in time the state estimates and covariances of said filter to generate a time-updated vector of state estimates representing said predicted state of the target, to thereby generate propagated target states; and

updating said propagated target states using measurements, to produce a vector of measurement updated state estimates and covariances of the target;

said method for attacking a target missile further comprising the steps of;

applying said updated state estimates and covariances to determine target acceleration, and controlling the firing and guidance of an interceptor missile in response to said updated state estimates and said target acceleration.

8. A method according to claim 7, wherein said step of providing a template representing nominal values of acceleration of said target includes the step of providing a template representing nominal values of acceleration of said target due to engine thrust, speed, altitude, and angle-of-attack, all as a function of time after target launch.

9. A method according to claim 7, wherein said step of reading from said template nominal value includes the step of reading from said template at least that nominal value of time after launch, acceleration, speed, and angle of attack corresponding to said calculated target altitude, to thereby produce read nominal values.

10. A method according to claim 9, wherein said step of initializing both the state estimate and the associated covariances of a filter with said read nominal values includes the step of initializing both the state estimate and the associated covariances of the filter with said nominal value of time after launch, acceleration, speed, and angle of attack corresponding to said calculated target altitude.

11. A method according to claim 7, wherein said step of propagating in time the state estimates and covariances of said filter to generate a time-updated vector of state estimates representing said predicted state of the target includes the step of propagating in time the state estimates and covariances of said filter to generate a time-updated vector of state estimates representing said predicted state of the target, using at least one of said template profile information updated by (a) variation in engine burn rate, (b) error in time after launch and (c) error in angle of attack.

12. A method according to claim 7, wherein:

said step of sensing at least the position of said target further comprises the step, of;

making measurements of the position of said target; and

said step of updating said propagated target states includes the step of updating said target states using the measurements to produce a vector of measurement updated state estimates and covariances of the target, including position and velocity, and at least one of (a) variation in engine burn rate, (b) error in time after launch and (c) error in angle of attack.

13. The method of claim 7, further comprising, subsequent to said step of calculating target altitude, establishing a time index by entering said template at said calculated target altitude.

15. The method of claim 7, wherein said filter is an extended Kalman filter.

16. A ballistic missile detection and defense system, comprising:

a missile detection system for estimating at least a time after launch of a ballistic missile;

a missile tracking system for receiving said time after launch from said missile detection system, and for estimating a state of said missile in flight, said missile tracking system comprising at least one nominal profile template of missile (a) altitude, (b) speed, and (c) angle-of-attack as a function of said time after launch; and

a comparator for comparing said state of said missile in flight with said at least one nominal profile template, and, if a match is found, identifying that missile on which said matching nominal profile is based.

17. The system of claim 16, further comprising an updated boost state estimator for estimating states of the target.

18. The system of claim 17, wherein the state of the target include at least one of target position, target velocity, error in angle of attack, error in time index into the template, and scalar motor variation factor.

19. The system of claim 16, further comprising a weapon control system for receiving information regarding the state of said missile and generating launch commands based on said information.

20. The system of claim 19, further comprising an interceptor launcher for receiving said launch commands from said weapon control system and launching an interceptor missile.