PASSIVE ACOUSTIC UNDERWATER INTRUDER DETECTION SYSTEM

• US 20110144930A1
• Filed: 11/03/2010
• Published: 06/16/2011
• Est. Priority Date: 11/03/2009
• Status: Active Grant

• Current Assignee: The Trustees of The Stevens Institute of Technology (Stevens Institute Of Technology)
• Original Assignee: The Trustees of The Stevens Institute of Technology (Stevens Institute Of Technology)
• Inventors: Bruno, Michael, Sutin, Alexander, Tsionskiy, Mikhail, Goheen, Howard, Bunin, Barry, Kahn, Malcolm, Fillinger, Laurent, Sedunov, Alexander, Sedunov, Nikolay, Turner, Jeremy
• Granted Patent: US 8,195,409 B2
• Time in Patent Office: Days
• US Class Current: 702/56
• CPC Class Codes: G01S 3/801 Details G01S3/82, G01S3/84, G01S3/86 take precedence
• CPC Class Codes: G01S 3/808 using transducers spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems
• CPC Class Codes: G01S 3/84 with indication presented on cathode-ray tubes
• CPC Class Codes: G01V 1/001 Acoustic presence detection

Abstract

A portable threat detection apparatus and method is disclosed which may comprise a plurality of acoustic emission sensors arranged in a cluster, forming a polygon defining at least two axes of alignment between respective pairs of acoustic emission sensors; a computing device in cooperation with a non-transitory computer readable storage medium comprising computer readable instructions for performing: receiving a first signal produced by a first acoustic emission sensor within a respective pair of acoustic emission sensors, in response to the first acoustic emission sensor detecting an acoustic emission from a source, and receiving a second signal produced by a second acoustic emission sensor within the respective pair of acoustic emission sensors, in response to the second acoustic emission sensor detecting the acoustic emission; determining a cross-correlation factor between the first signal and the second signal; and, determining a bearing to the source based on the cross correlation factor.

Claims

1. A portable threat detection apparatus, comprising:

a plurality of acoustic emission sensors arranged in a cluster, the cluster forming a polygon defining at least two axes of alignment between respective pairs of acoustic emission sensors within the cluster;

a computing device in cooperation with a non-transitory computer readable storage medium comprising computer readable instructions for performing via the computing device a method comprising;

receiving a first signal produced by a first acoustic emission sensor within a respective pair of acoustic emission sensors, in response to the first acoustic emission sensor detecting an acoustic emission from a source, and receiving a second signal produced by a second acoustic emission sensor within the respective pair of acoustic emission sensors, in response to the second acoustic emission sensor detecting the acoustic emission from the source;

determining a cross-correlation factor between the first signal and the second signal; and

,

determining a bearing to the source based on the cross correlation factor.

2. The portable threat detection apparatus of claim 1, further comprising:

the method further comprising;

analyzing one of the first signal produced by the first acoustic emission sensor and the second signal produced by the second acoustic emission sensor, together with at least one other signal representative of the detecting of at least one other acoustic emission from the source, to determine if each of the one of the first signal and the second signal and the at least one other signal conform to a threat-type template.

3. The portable threat detection apparatus of claim 2, further comprising:

the method further comprising;

determining whether the compliance of the each of the one of the first signal and the second signal and the at least one other signal to the threat-type template persists as to subsequent ones of a first signal and a second signal and at least one subsequent other signal, for some threshold period of time.

4. The portable threat detection apparatus of claim 1, further comprising:

the apparatus being deployed on the bottom of a body of water.

5. The portable threat detection apparatus of claim 4, further comprising:

the plurality of acoustic emission sensors each comprising a hydrophone.

6. The portable threat detection apparatus of claim 1, further comprising:

the plurality of acoustic emission devices each comprising a hydrophone, wherein the hydrophones forming the cluster are tethered to each other.

7. The portable threat detection apparatus of claim 6, further comprising:

the hydrophones forming the cluster are tethered to each other through a center pod.

8. The portable threat detection apparatus of claim 7, further comprising:

the center pod comprising;

a buoyancy mechanism; and

,

a bottom mooring mechanism; and

,

a mechanism for releasing the center pod from the bottom mooring mechanism, whereby the center pod and the hydrophones are recoverable at a surface of a body of water on the bottom of which the center pod and hydrophones had been deployed.

21. The threat detection apparatus of claim 1, further comprising:

determining a range to the source based on the cross correlation factor.

9. A method for threat detection comprising:

receiving, via a computing device, a first signal produced by a first acoustic emission sensor in response to the first acoustic emission sensor detecting an acoustic emission from a source and a second signal produced by a second acoustic emission sensor in response to the second acoustic emission sensor detecting the acoustic emission from the source;

determining, via a computing device, a cross-correlation factor between the first signal and the second signal;

determining, via a computing device, a bearing to the source based on the cross correlation factor.

10. The method of claim 9, further comprising:

analyzing, via a computing device, one of the first signal produced by the first acoustic emission sensor and the second signal produced by the second acoustic emission sensor, together with at least one other signal representative of the detecting of at least one other acoustic emission from the source, to determine if the one of the first signal and the second signal and the at least one other signal conform to a threat-type template.

11. The method of claim 10, further comprising:

determining whether the compliance of the one of the first signal and the second signal and the at least one other signal to the threat-type template persists as to subsequent one of a first signal and a second signal and at least one other subsequent signal for some threshold period of time.

22. The method of claim 9, further comprising:

determining a range to the source based on the cross correlation factor.

12. A non-transitory computer readable storage medium comprising instructions for performing a method of threat detection, the computer readable storage medium comprising instructions for execution by a computing device to perform the method, the method comprising:

receiving a first signal produced by a first acoustic emission sensor in response to the first acoustic emission sensor detecting an acoustic emission from a source and a second signal produced by a second acoustic emission sensor in response to the second acoustic emission sensor detecting the acoustic emission from the source;

determining a cross-correlation factor between the first signal and the second signal;

determining a bearing to the source based on the cross correlation factor.

13. The computer readable storage medium of claim 12, wherein the method further comprises:

analyzing one of the first signal produced by the first acoustic sensor and the second signal produced by the second acoustic emission sensor, together with at least one other signal representative of the detecting of at least one other acoustic emission from the source, to determine if the one of the first signal and the second signal and the at least one other signal conform to a threat-type template.

14. The computer readable storage medium of claim 12, wherein the method further comprises:

determining whether the compliance of the one of the first signal and the second signal and the at least one other signal to the threat-type template persists as to subsequent one of the first signal and the second signal and subsequent at least one other signal for some threshold period of time.

23. The computer readable medium of claim 12, further comprising:

determining a range to the source based on the cross correlation factor.

15. A method for determining the positioning of a plurality of acoustic emission sensors of which a portable threat detection system is comprised and which are arranged in a polygon shaped cluster forming a threat detection apparatus, comprising:

stimulating the acoustic emission sensors within the cluster with acoustic emissions from an acoustic emission source moveable with respect to the cluster and having a known geographic location with time;

detecting, via a computing device, a maximum cross correlation signal for a respective pair of acoustic emission sensors consisting of a first acoustic emission sensor and a second acoustic emission sensor, aligned along an axis of alignment for the respective pair of acoustic emission sensors, the maximum cross-correlation signal occurring at a known time;

determining, based on the geographic location of the source at the known time of the occurrence of the maximum, the bearing of the first acoustic emission sensor to the second acoustic emission sensor.

16. The method of claim 15, further comprising:

determining, based on a value of the maximum cross correlation signal the separation of the first acoustic emission sensor from the second acoustic emission sensor.

17. A method of determining the positioning of acoustic emission sensors of which a portable threat detection system is comprised and which are arranged in a cluster formed about a center pod, at least two of the acoustic emission sensors having a known position with relation to each other in the cluster, comprising:

detecting, via a computing device, a signal from each of the at least two of the acoustic emission sensors in response to an acoustic emission generated at the center pod;

measuring, via a computing device, the time difference between the emission of the acoustic emission at the center pod and the detection of the acoustic emission by each respective acoustic emission sensor in the at least two of the acoustic emission sensors;

determining, via a computing device, a distance between each of the at least two acoustic emission sensors and the center pod based on the time difference for each respective acoustic emission sensor.

18. A method of determining a measure of effectiveness of a respective one of a plurality of acoustic emission sensors of which a portable threat detection system is comprised and which are arranged in a cluster formed about a center pod having a known separation from the respective one of the acoustic emissions detectors, comprising:

detecting, via a computing device, a signal from the respective one of the acoustic emissions sensors responsive to an acoustic emission from the center pod of a known strength;

comparing, via a computing device, a detected level of the signal from the respective one of the acoustic emissions sensors to a baseline level.

19. The method of claim 18, further comprising:

the baseline level being set by a prior level of the signal from the respective one of the acoustic emissions sensors to a prior similar acoustic emission from the center pod.

20. The method of claim 18 further comprising:

at least one of the detected level of the signal and the baseline level being adjusted for any change in separation of the respective one of the acoustic emission sensors and the center pod.