Systems and methods for determining shooter locations with weak muzzle detection

• US 20080159078A1
• Filed: 03/07/2008
• Published: 07/03/2008
• Est. Priority Date: 08/23/2005
• Status: Active Grant

• Current Assignee: Raytheon BBN Technologies Corp. (Rtx Corporation)
• Original Assignee: BBN Technologies Corporation (Rtx Corporation)
• Inventors: Milligan, Stephen D., Brinn, Marshall Seth, Barger, James E., Mullen, Richard J.
• Granted Patent: US 7,710,828 B2
• Time in Patent Office: Days
• US Class Current: 367/127
• CPC Class Codes: G01S 5/22 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/28 takes precedence
• CPC Class Codes: Y10S 367/906 Airborne shock-wave detection

Abstract

Systems and methods for locating the shooter of supersonic projectiles are described. The system uses at least five, preferably seven, spaced acoustic sensors. Sensor signals are detected for shockwaves and muzzle blast, wherein muzzle blast detection can be either incomplete coming from less than 4 sensor channels, or inconclusive due to lack of signal strength. Shooter range can be determined by an iterative computation and/or a genetic algorithm by minimizing a cost function that includes timing information from both shockwave and muzzle signal channels. Disambiguation is significantly improved over shockwave-only measurements.

Claims

1. A method for disambiguating a projectile trajectory from shockwave signals and a limited number of muzzle blast signals, comprising:

measuring shockwave-only signals at five or more spaced acoustic sensors forming an antenna;

measuring muzzle blast signals on at most four of the sensors;

determining from the shockwave signals Time-Differences-Of-Arrival (TDOA) information for sensor pairs; and

computing the disambiguated projectile trajectory from the TDOA information, shockwave signals, and muzzle blast signals.

2. The method of claim 1, wherein muzzle blast signals are measured on exactly three of the sensors.

3. The method of claim 2, wherein the disambiguated projectile trajectory is computed using a genetic algorithm.

4. The method of claim 3, wherein performing the genetic algorithm comprises using a predefined number of generations with an initial population that includes a predetermined number of individuals, wherein each individual represented by a 4-tupel which includes shooter azimuth, shooter elevation, missed azimuth and missed elevation.

5. The method of claim 4, wherein residuals are computed for the individuals in each generation, said residuals including a least-square fit of a combination of TDOA shockwave and muzzle blast signals.

6. The method of claim 5, wherein if a ratio of the solution having the smallest residual and its ambiguous alternate solution is greater than a predefined value, designating the solution having the smallest computed residual as the disambiguated projectile trajectory.

7. The method of claim 6, wherein performing the genetic algorithm comprises applying crossover and mutation operators to the initial population in a generation.

8. The method of claim 7, wherein applying the crossover operator includes exchanging at least one of missed azimuth and missed elevation between two individuals from the population in a generation.

9. The method of claim 7, wherein applying the crossover operator includes exchanging at least one of shooter azimuth and trajectory azimuth between two individuals from the population in a generation.

10. The method of claim 7, wherein the mutation operator comprises field-mutation, incremental mutation, flip-mutation and no mutation.

11. The method of claim 10, wherein the field-mutation operator replaces a value of the 4-tupel with a randomly selected value.

12. The method of claim 10, wherein the incremental mutation operator induces a small mutation in all fields of the 4-tupel.

13. The method of claim 10, wherein the flip-mutation operator changes the solution in a generation to its ambiguous alternate solution in the generation.

14. The method of claim 10, wherein the no-mutation operator leaves the individuals in a generation unaltered.