METHOD AND DEVICE FOR DETECTING A FIRE SHOT EVENT IN A WEAPON

• US 20110252683A1
• Filed: 07/08/2008
• Published: 10/20/2011
• Est. Priority Date: 08/16/2007
• Status: Active Grant

• Current Assignee: Saab AB
• Original Assignee: Saab AB
• Inventors: Isaksson, Anders, Chedid, Michel, Emricson, Ingemar, Dahlqvist, Stefan, Forselius, Mats
• Granted Patent: US 8,616,882 B2
• Time in Patent Office: Days
• US Class Current: 42/1.03
• CPC Class Codes: F41G 3/2655 in which the light beam is sent from the weapon to the target

Abstract

A method including measuring a physical quantity having a magnitude that changes in time as a result of a fire shot event so as to obtain a measurement signal, and comparing the measurement signal with a predetermined time-domain fingerprint for said quantity, which fingerprint is characteristic of the way the quantity varies in time upon a fire shot event, in order to confirm the occurrence of a fire shot event in case the measurement signal and the fingerprint match.

Claims

1. A method for detecting a fire shot event in a weapon comprising the step of

measuring a physical quantity whose magnitude changes in time as a result of a fire shot event so as to obtain a measurement signal,

characterized by further comprising the step of:

comparing the measurement signal with a predetermined time-domain fingerprint for said quantity, which fingerprint is characteristic of the way said quantity varies in time upon a fire shot event, in order to confirm the occurrence of a fire shot event in case said measurement signal and said fingerprint match.

2. Method according to claim 1, further comprising the step of generating a laser beam emulating a fire shot from said weapon in case the occurrence of a fire shot event is confirmed.

3. Method according to any of the claim 1 or 2, wherein the measurement signal and the predetermined fingerprint signal are represented by vectors, and the comparison is based on the difference between said vectors.

4. Method according to any of the claims 1 to 3, wherein the step of comparing the measurement signal with the predetermined fingerprint comprises the steps of:

forming an error estimation E as a weighted sum of absolute differences according to E=W^T|U−

s|,

where W is a weight vector, U is a vector representation of the predetermined fingerprint and s is a vector representation of the measurement signal; and

computing E continuously with an online algorithm where the computation is made on a moving window of the same length as the fingerprint vector U in order to confirm the occurrence of a fire shot event in case E drops below a predetermined threshold value T.

5. Method according to claim 3 or 4, wherein the predetermined fingerprint vector U is determined as the mean of a plurality of fingerprint measurements according to

6. Method according to claim 3 or 4, wherein the weight vector W is approximated as

7. Method according to any of the preceding claims, wherein the physical quantity measured is the shock or vibration of the weapon caused by the explosion of a cartridge in said weapon.

8. Method according to any of the claims 1 to 6, wherein the physical quantity measured is the pressure wave in air caused by the explosion of a cartridge in said weapon.

9. Method according to any of the claims 1 to 6, wherein the physical quantity measured is the electromagnetic wave or pulse caused by the explosion of a cartridge in said weapon.

10. Method according to any of the claims 1 to 6, wherein the physical quantity measured is the radiance or light intensity of the flash caused by the explosion of a flame-generating cartridge in said weapon.

11. A shot detection device (3) for detecting a fire shot event in a weapon, said shot detection device comprises measuring means (7) for measuring a physical quantity whose magnitude changes in time as a result of a fire shot event in said weapon, characterized in that it further comprises comparison means (9) arranged to compare the measurement signal measured by the measuring means (7) to a predetermined time-domain fingerprint for said quantity, which fingerprint is characteristic of the way said quantity varies in time upon a fire shot event, and arranged to confirm the occurrence of a fire shot event in case said measurement signal and said fingerprint match.

12. A shot detection device (3) according to claim 11, said shot detection device further comprising means (10) arranged to generate a laser beam emulating a fire shot from said weapon in case said comparison means (9) has confirmed the occurrence of a fire shot event.

13. A shot detection device (3) according to claim 11 or 12, said shot detection device (3) being an integral part of a firearm (1), or an imitation or bully firearm.

14. A shot detection device (3) according to claim 11 or 12, said shot detection device (3) being a separate unit which is arranged to be detachably connected to a firearm (1).

15. A shot detection device (3) according to claim 14, said shot detection device (3) further comprising identification means arranged to identify the type of firearm to which it is connected, said shot detection device (3) further being arranged to store a plurality of fingerprints associated with different firearm types and to chose a fingerprint based on the type of firearm identified, and to compare the measurement signal to said chosen fingerprint.

16. A shot detection device (3) according to any of the claims 11 to 15, said shot detection device further comprising means (11) for transmitting information relating to the comparison procedure to an information collection device carried by the user of said weapon.

17. A computer program product for detecting a fire shot event in a weapon (1), characterized in that said computer program, when executed by a processor in a shot detection device according to any of the claims 11 to 16, is arranged to take a measurement signal of a physical quantity as input, and compare said measurement signal to a predetermined fingerprint, which fingerprint is characteristic of the way said quantity varies in time upon a fire shot event, and generate an output being indicative of whether said measurement signal and said fingerprint match.