Method and apparatus to detect event signatures

• US 7,535,355 B2
• Filed: 08/26/2005
• Issued: 05/19/2009
• Est. Priority Date: 08/27/2004
• Status: Expired due to Fees

• Current Assignee: L-3 Communications Security & Detection Systems, Inc. (Leidos Holdings, Inc.)
• Original Assignee: L-3 Communications Security and Detection Systems Incorporated
• Inventors: Barone, Gerard A.
• Primary Examiner(s): Bugg; George A
• Assistant Examiner(s): Labbees; Edny
• Application Number:
  US11/212,859
• Publication Number:
  US 20070290842A1
• Time in Patent Office: 1,362 Days
• Field of Search: 340/565, 340/566, 340/567, 340/573.1, 340/573.4, 340/539.26
• US Class Current: 340/566
• CPC Class Codes: G07C 3/00 Registering or indicating the condition or the working of machines or other apparatus, other than vehicles
• CPC Class Codes: G08B 13/1654 using passive vibration detection systems

Abstract

A security system for use in connection with cargo containers and other enclosed spaces. The system monitors vibrations associated with a container and detects signals representative events indicating that an unauthorized access has been made to the container. The system may be programmed with a library of event signatures, allowing different types of events to be detected. The system may be provided with a library of signatures representing a heart beating with a beat pattern and the system may be used to detect a human or other animal within the container. Alternatively, the system may be provided with a library of signatures representing piercing the container. The system may be used to monitor containers in transit. Indications of events may be stored while the container is in transit and then communicated at a security check point.

Claims

1. A container, comprising:

a) a vibration sensor;

b) a processor, coupled to receive a signal from the vibration sensor and adapted to process the signal to detect a pattern of vibration characteristic of an unauthorized opening of the container,

the processor comprising computer storage media storing a library comprising a plurality of event signatures, each event signature representing a frequency spectrum of an event signal generated by an event as detected at the vibration sensor, the plurality of event signatures including an event signature representing the unauthorized opening; and

the processor being adapted to;

form a plurality of frequency domain representations of the signal, each formed from a portion of the signal;

compare each of the plurality of frequency domain representations of the signal to the plurality of event signatures; and

detect the unauthorized opening of the container based on the result of the comparisons; and

c) an interface, coupled to the processor and adapted to communicate an indication of whether the pattern was detected.

2. The container of claim 1, wherein the interface comprises a wireless interface.

3. The container of claim 2, wherein the interface is adapted to communicate the indication in response to an interrogation signal.

4. The container of claim 1, wherein the indication is encrypted when communicated.

5. The container of claim 1, wherein the processor comprises computer-readable media comprising a plurality of computer-executable instructions for comparing at least a portion of the signal to each of a plurality of event signatures and identifying the pattern characteristic of an event based on similarity of the signal to an event signature of the plurality of event signatures, whereby the computer-executable instructions adapt the processor to detect the unauthorized opening of the container.

6. The container of claim 1, additionally comprising computer memory and wherein the processor is adapted to store at a first time data signifying that the pattern was detected and to communicate at a second time the data through the interface as the indication.

7. The container of claim 1, additionally comprising a low pass filter and wherein the processor is coupled to the sensor through the low pass filter.

8. The container of claim 1, additionally comprising a second sensor coupled to the processor.

9. The container of claim 1, additionally comprising a second sensor, a second processor coupled to the second sensor and a second interface coupled to the second processor.

10. A method of operating a security system for a container, comprising the acts:

a) monitoring vibrations of the container to detect a vibration signal having a characteristic representative of an undesired access to the container while the container is en route to a destination, the detecting comprising;

forming a plurality of frequency domain representations of the vibrations, each frequency domain representation formed from a portion of the vibrations;

comparing each of the plurality of frequency domain representations of the signal to a library comprising a plurality of event signatures;

detecting the unauthorized opening of the container based on the result of the comparing;

b) storing an indication when the vibration signal characteristic is detected; and

c) at the destination, retrieving the stored indication and taking a security action in response to the stored indication.

11. The method of claim 10, wherein the act a) comprises monitoring vibrations to detect a vibration signal having a characteristic representative of a container wall being cut.

12. The method of claim 10, wherein the act a) comprises monitoring vibrations to detect a vibration signal having a characteristic representative of a person inside the container.

13. The method of claim 10, wherein the destination is a security checkpoint.

14. The method of claim 13, additionally comprising:

d) transferring the stored indication to a processor outside the container at the security checkpoint.

15. The method of claim 14, wherein transferring the stored indication comprises transmitting data representative of the indication through an interface on the container.

16. The method of claim 13, additionally comprising the act:

d) clearing the container when no indication is stored.

17. The method of claim 10, wherein the act a) comprises monitoring vibrations with a plurality of sensors and detecting a vibration signal comprises comparing vibration signals detected with each of the plurality of sensors.

18. A method of detecting an event in relation to a container, comprising:

a) providing a library comprising a plurality of event signatures, each event signature representing the frequency spectrum of an event signal generated by an event and passing through the container, the providing accomplished by;

i) generating a plurality of event signals, each representative of an event; and

ii) computing a plurality of estimated signals by applying to each of the plurality of event signals a transfer function characterizing a signal path including the cargo container;

b) obtaining a vibration signal representative of vibrations of the container;

c) forming a plurality of frequency domain representations of the vibration signal, each formed from a portion of the vibration signal;

d) comparing each of the plurality of frequency domain representations of the vibration signal to the plurality of event signatures; and

e) detecting an event based on the result of the comparisons of act d).

19. The method of claim 18 wherein the act c) comprises performing a discrete transform on each of a plurality of successive and overlapping windows of the vibration signal.

20. The method of claim 18 wherein the act a) further comprises:

iii) generating the plurality of event signatures by performing a frequency domain transform on each of the plurality of estimated signals.

22. The method of claim 18, additionally comprising:

e) obtaining a second vibration signal, correlated in time with the first signal, and

f) performing the acts c) and d) on the second vibration signal,

wherein the act e) comprises detecting an event based on the result of the comparison performed in the act d) on the vibration signal and the comparison performed in the act d) on the second vibration signal.

23. The method of claim 18, wherein:

the plurality of event signatures represent event signals with a periodicity;

the act d) comprises selecting a plurality of portions of the vibration signal that match one of the plurality of event signals, the selected plurality of portions having a periodicity; and

the act e) comprises detecting the event when there is a harmonic relationship between the periodicity of the one of the plurality of event signals and the periodicity of the selected portions.

21. A method of detecting an event in relation to a container, comprising:

a) providing a plurality of event signatures, each representing the frequency spectrum of an event signal generated by an event and passing through the container;

b) obtaining a vibration signal representative of vibrations of the container;

c) forming a plurality of frequency domain representations of the vibration signal, each formed from a portion of the vibration signal;

d) comparing each of the plurality of frequency domain representations of the vibration signal to the plurality of event signatures, the comparing comprising;

i) normalizing each of the plurality of frequency domain representations of the vibration signal and,

ii) wherein each of the frequency domain representations comprises a plurality of frequency values and the act d) further comprises mapping each frequency value to one of a plurality of bins; and

e) detecting an event based on the result of the comparisons of act d).