A system for determining the origin and trajectory of a gunshot includes spaced sensor nodes and a base station. A method for determining the origin and trajectory of a gunshot includes the steps of, at the nodes, sensing acoustic signals, converting the acoustic signals into digital signals, separa
A system for determining the origin and trajectory of a gunshot includes spaced sensor nodes and a base station. A method for determining the origin and trajectory of a gunshot includes the steps of, at the nodes, sensing acoustic signals, converting the acoustic signals into digital signals, separating the digital signals into segments, calculating a time of arrival of each segment, and extracting features from each segment, and then at the base station identifying each time of arrival as a main shock wave or a main muzzle blast time of arrival from the features, and computing the trajectory from the main shock wave times of arrival. The computed trajectory includes velocity and acceleration. The method also includes computing, at the base station, the origin from the main muzzle blast times of arrival.
대표청구항▼
1. A method for finding the trajectory of a gunshot projectile from acoustic signals, comprising the steps of: providing a plurality of spaced, distributed sensor nodes and a base station in communication with said nodes,sensing said acoustic signals at said nodes,converting said acoustic signals in
1. A method for finding the trajectory of a gunshot projectile from acoustic signals, comprising the steps of: providing a plurality of spaced, distributed sensor nodes and a base station in communication with said nodes,sensing said acoustic signals at said nodes,converting said acoustic signals into digital signals at said nodes,separating, at said nodes, said digital signals into segments including at least one of a main shock wave segment, a main muzzle blast segment and other segments,calculating, at said nodes, a time of arrival of each said segment,extracting, at said nodes, features from each said segment,identifying, at said base station, each said time of arrival as one of a main shock wave and a main muzzle blast time of arrival from said features, andcomputing, at said base station, said trajectory from said main shock wave times of arrival, said trajectory including velocity and acceleration, including the substeps of selecting a reference node and calculation said trajectory from an observed time difference of arrival for said main shock wave segment for each node relative to said reference node, and said substep of calculating said trajectory including minimizing a cost function based on errors between said observed time differences of arrival for said nodes and theoretical time differences of arrival for said nodes generated from a model. 2. The method as set forth in claim 1 further comprising the step of computing, at said base station, an origin for said projectile from said main muzzle blast times of arrivals. 3. The method as set forth in claim 1 wherein said model provides that a theoretical main shock wave time of arrival is the sum of a time of said gunshot, a time for a projectile to travel from an origin of said projectile to a shock wave source point and a time for a shock wave to travel from said shock wave source point to said node, and said theoretical main shock wave time of arrival is a function of said origin of said projectile, the position of said node, a trajectory angle for said projectile, an initial velocity of said projectile and an acceleration of said projectile. 4. The method as set forth in claim 3 wherein said time for said projectile to travel from said origin of said projectile to said shock wave source point equals: -2v0+4v02+8αxd2α where v0 is said initial velocity of said projectile, xd is an assumed distance from said origin of said gunshot to said shock wave source point, and α is said acceleration of said projectile. 5. The method as set forth in claim 4 wherein xd is evaluated iteratively from xd=0, in a selected interval, relative to the intersection of said trajectory with a line that passes through said node and is normal to a shock wave cone. 6. The method as set forth in claim 1 further comprising the step of detecting, at said nodes, a gunshot in said digital acoustic signals. 7. The method as set forth in claim 6 wherein said step of detecting a gunshot includes the substeps of down-sampling said digital signals to produce down-sampled signals and then applying a Hidden Markov Model based detector to said down-sampled signals. 8. The method as set forth in claim 7 wherein said acoustic signals are down-sampled at 16 KHz in said substep of down-sampling. 9. The method as set forth in claim 1 wherein said acoustic signals are sampled at 1 MHz in said step of converting. 10. The method as set forth in claim 9 wherein said step of separating includes the substep of applying a Hidden Markov Model to said digital signals. 11. The method as set forth in claim 10 wherein said step of separating includes the substeps of applying a moving average filter to a gradient of a cumulative likelihood ratio of samples of said digital signal, selecting segments from said digital signal with a moving average greater than a selected threshold, sorting said selected segments in descending order, and choosing a first selected segment as said main shock wave segment and a second selected segment as said main muzzle blast segment. 12. The method as set forth in claim 1 wherein said step of extracting features includes the substep of constructing a feature vector from a Hidden Markov Model state propagation sequence for said segment. 13. A method for finding the trajectory of a gunshot projectile from acoustic signals, comprising the steps of: providing a plurality of spaced, distributed sensor nodes and a base station in communication with said nodes,sensing said acoustic signals at said nodes,converting said acoustic signals into digital signals at said nodes, said acoustic signals being sampled at 1 MHz,detecting, at said nodes, a gunshot in said digital acoustic signals, said step of detecting a gunshot including the substeps of down-sampling said digital signals at 16 KHz to produce down-sampled signals and then applying a Hidden Markov Model based detector to said down-sampled signals,separating, at said nodes, said digital signals into segments including at least one of a main shock wave segment, a main muzzle blast segment and other segments, said step of separating including the substeps of applying a moving average filter to a gradient of a cumulative likelihood ratio of samples of said digital signal, selecting segments from said digital signal with a moving average greater than a selected threshold, sorting said selected segments in descending order, and choosing a first selected segment as said main shock wave segment and a second selected segment as said main muzzle blast segment,calculating, at said nodes, a time of arrival of each said segment,extracting, at said nodes, features from each said segment, said step of extracting features including the substep of constructing a feature vector from a Hidden Markov Model state propagation sequence for said segment,identifying, at said base station, each said time of arrival as one of a main shock wave and a main muzzle blast time of arrival from said features, andcomputing, at said base station, said trajectory from said main shock wave times of arrival, said trajectory including velocity and acceleration, said step of computing said trajectory including the substeps of selecting a reference node and calculating said trajectory from an observed time difference of arrival for said main shock wave segment for each node relative to said reference node, wherein said substep of calculating said trajectory includes minimizing a cost function based on errors between said observed time differences of arrival for said nodes and theoretical time differences of arrival for said nodes generated from a model, and wherein said model provides that a theoretical main shock wave time of arrival is the sum of a time of said gunshot, a time for a projectile to travel from an origin of said projectile to a shock wave source point and a time for a shock wave to travel from said shock wave source point to said node, and said theoretical main shock wave time of arrival is a function of said origin of said projectile, the position of said node, a trajectory angle for said projectile, an initial velocity of said projectile and an acceleration of said projectile, andcomputing, at said base station, an origin for said projectile from said main muzzle blast times of arrivals. 14. A system for finding the trajectory of a gunshot projectile from acoustic signals, comprising: a plurality of spaced, distributed sensor nodes, each said sensor node including:an acoustic sensor for sensing said acoustic signals,means for separating said acoustic signals into segments including at least one of a main shock wave segment, a main muzzle blast segment and other segments,means for calculating a time of arrival of each said segment, andmeans for extracting features from each said segment, anda base station in communication with said nodes, including:means for identifying each said time of arrival as one of a main shock wave and a main muzzle blast time of arrival from said features,a processor, andmeans for computing said trajectory from said main shock wave times of arrival, said trajectory including velocity and acceleration, including instructions in said processor for selecting a reference node and calculating said trajectory from an observed time difference of arrival for said main shock wave segment for each node relative to said reference node, wherein said instructions for calculating said trajectory include instructions for minimizing a cost function based on errors between said observed time differences of arrival for said nodes and theoretical time differences of arrival for said nodes generated from a model. 15. The system as set forth in claim 14 wherein said base station includes means for computing said origin from said times of arrival for said main muzzle blast segments. 16. The system as set forth in claim 14 wherein: said means for identifying includes said processor and instructions in said processor for identifying each said time of arrival as one of a main shock wave and a main muzzle blast time of arrival from said features, andsaid means for computing includes said processor and instructions in said processor for computing said trajectory from said main shock wave times of arrival. 17. The system as set forth in claim 14 wherein said model provides that a theoretical main shock wave time of arrival is the sum of a time of said gunshot, a time for a projectile to travel from said origin of said gunshot to a shock wave source point and a time for a shock wave to travel from said shock wave source point to said node, and said theoretical main shock wave time of arrival is a function of said origin of said gunshot, the position of said node, a trajectory angle for said projectile, an initial velocity of said projectile and an acceleration of said projectile. 18. The system as set forth in claim 17 wherein said time for said projectile to travel from said origin of said gunshot to said shock wave source point equals: -2v0+4v02+8αxd2α where v0 is said initial velocity of said projectile, xd is the distance from said origin of said gunshot to said shock wave source point, and α is said acceleration of said projectile. 19. The system as set forth in claim 16 wherein each said node includes means for detecting a gunshot in said acoustic signals. 20. The system as set forth in claim 14 wherein: each said node includes a processor,said means for separating includes said processor and instructions in said processor for separating said acoustic signals into segments,said means for calculating includes said processor and instructions in said processor for calculating said time of arrival of each said segment, andsaid means for extracting features includes said processor and instructions in said processor for extracting features from each said segment.
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이 특허에 인용된 특허 (7)
Duckworth Gregory L. ; Barger James E. ; Gilbert Douglas C., Acoustic counter-sniper system.
Barger,James E.; Milligan,Stephen D.; Brinn,Marshall Seth; Mullen,Richard J., Systems and methods for determining shooter locations with weak muzzle detection.
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