Compact shooter localization system and method
View Patent ↗Systems and methods for locating the shooter of supersonic projectiles are described. Muzzle blast signals are neither sought nor required. The system uses at least two sensors, with each sensor having a 3-axis accelerometer. The sensors are spaced apart at least 1 meter and have each a diameter of about one centimeter. The three accelerometer signals of each sensor represent pressure gradients and are processed to find the shockwave arrival angle unit vector, the shockwave arrival time instant and peak pressure. Noise signals seldom cause false detections with this sensing method because the sensors have maximum sensitivity at the high frequency characteristics of shockwaves, while their sensitivity to the low frequency characteristics of ambient noise is relatively low.
1. A sensor for determining a pressure gradient generated by a shockwave, comprising:
a support structure;
a substantially spherical body made of aluminum and elastically supported by the support structure for movement in at least two directions;
an accelerometer enclosed in the body and generating an output signal in response to a force applied to the body;
wherein the force is produced by the pressure gradient and the output signal indicates a magnitude and direction of the pressure gradient.
2. The sensor of claim 1 , wherein the sensor has a sensitivity peak in a frequency range that matches a maximum signal energy range of the shockwave.
3. The sensor of claim 1 , wherein the sensor has a sensitivity peak in a frequency range above about 6 kHz.
4. The sensor of claim 1 , wherein the sensor has a sensitivity peak at a frequency of about 12 kHz.
5. The sensor of claim 1 , wherein the sensor has a sensitivity peak in a frequency range having frequencies greater than a frequency of signal energy produced by ambient noise.
6. A system for determining the trajectory of a supersonic projectile comprising:
at least two spaced-apart sensors, the sensors supported by a support structure at known coordinate positions and encountering a shockwave generated by said supersonic projectile, each sensor comprising;
a substantially spherical body elastically supported by the support structure for movement in at least two directions;
an accelerometer enclosed in the body and generating an output signal in response to a force applied to the body, wherein the force is produced by a pressure gradient of said shockwave and the output signal indicates a magnitude and direction of the pressure gradient and an arrival time of the shockwave at the sensor; and
a processor processing the output signals and the arrival times from the at least two sensors and unambiguously determining said trajectory of said supersonic projectile.
7. The system of claim 6 , wherein the accelerometer is a three-axes accelerometer producing output signals representative of an acceleration in three mutually independent directions.
8. The system of claim 6 , wherein the substantially spherical body is made of a lightweight metal or a plastic material.
9. The system of claim 8 , wherein the plastic material comprises a plastic foam with a waterproof surface.
10. The system of claim 8 , wherein the lightweight metal comprises aluminum.
11. The system of claim 6 , wherein the support structure comprises a frame.
12. The system of claim 11 , wherein the frame is constructed to have a characteristic oscillation frequency of less than 1 kHz.
13. The system of claim 11 , wherein the body is supported in the frame by wire, thread or tape.
14. The system of claim 13 , wherein the body is supported by the support structure, with the support structure having a characteristic oscillation frequency of less than 1 kHz.
15. The system of claim 13 , wherein the body is supported by the support structure, with the support structure having a characteristic oscillation frequency of less than 100 Hz.
16. The system of claim 13 , wherein the support structure comprises an elastic member.
17. The system of claim 16 , wherein the elastic member comprises a spring.
18. The system of claim 6 , wherein information for determining said trajectory is selected from the group consisting of shooter direction azimuth, shooter direction elevation, trajectory direction azimuth, trajectory direction elevation, muzzle velocity, and bullet drag coefficient.
19. The system of claim 6 , wherein the at least one sensor has a sensitivity peak in a frequency range that matches a maximum signal energy range of the shockwave.
20. The system of claim 6 , wherein the at least one sensor has a sensitivity peak in a frequency range above about 6 kHz.
21. The system of claim 6 , wherein the at least one sensor has a sensitivity peak at a frequency of about 12 kHz.
22. The system of claim 6 , wherein the at least one sensor has a sensitivity peak in a frequency range having frequencies greater than a frequency of signal energy produced by ambient noise.
23. The system of claim 6 , wherein the processor is configured to determine the trajectory of the supersonic projectile for detecting a shooter location.
24. The system of claim 6 , wherein the processor is further configured to detect the location of a shooter of the supersonic projectile.