CROSS-REFERENCE TO RELATED APPLICATIONS

[0001 ] This Application claims rights under 35 USC §119(e) from U.S. Application 62/033,906 filed on August 6, 2014, the contents of which are incorporated herein by reference.

STATEMENT OF GOVERNMENT INTEREST

[0002] This invention was made with United States Government support under Contract No. H94003-04-D-0002-0079 awarded by UNITED STATES AIR FORCE. The United States Government has certain rights in this invention.

BACKGROUND OF THE INVENTION Field of the Invention

[0003] The present invention relates to determining gunfire detections, and more specifically, utilizing sensors for determining miss distance and bullet speed of a burst of bullets.

Brief Description of Related Art

[0004] During high tension gunfights, sensors may be used in a platform, such as a stationary structure or a vehicle (e.g., aircraft) to determine the origin and trajectory of fired rounds/bullets. Example bullet may be any projectile such as a bullet, artillery shell, missile, bombs, or other object that exhibit the characteristics consistent with a bullet in flight. The bullet may be propelled from a firearm. Some existing methods may use electro-optic (EO) sensors to detect the gunfire, while some other methods may use acoustical sensors. Further, some existing methods may attempt to combine utilizing both EO and acoustical sensors, however, this may require an increased correlative element and certainty that data points collected from the EO sensors match the associated data points collected by the acoustical sensors. Failure to do so may result in irrelevant correlations of data points with respect to bullets from multiple gunmen interfering.

[0005] Typically, the EO and acoustic sensor detections may be fused "round to round", i.e., attempting to correlate between a single EO detection and a single acoustic detection. In the single round approach, one sensor may detect a round while the other fails to detect the round. For example, the EO sensors can only detect some of rounds whereas acoustic sensors can potentially detect all the rounds. Further, in case where both sensors detect a round, the EO round detection may be paired with an incorrect acoustically detected round.

SUMMARY OF THE INVENTION

[0006] A method and system for determining miss distance and bullet speed of a burst of bullets. According to one aspect of the present subject matter, shock wave (SW) vectors emanating from bullets are estimated using a first sensor. Further, firing point (FP) vectors and closest-point-of-approach (CPA) vectors emanating from the bullets are estimated using a second sensor. The first sensor and the second sensor are disposed on a

2 platform. For example, the first sensor is an acoustic sensor and the second sensor is an electro-optic sensor. The SW vectors, the FP vectors and the CPA vectors are determined as emanating from the burst of bullets. The miss distance and bullet speed of the burst of bullets are determined using the FP vectors, the SW vectors, and the CPA vectors that are emanating from the burst of bullets.

[0007] According to another aspect of the present subject matter, a system includes a first sensor to detect SW vectors, a second sensor to detect FP vectors and CPA vectors, and a computational unit communicatively coupled to the first sensor and the second sensor, the computational unit is configured to perform the method described above.

[0008] According to another aspect of the present subject matter, a non-transitory computer-readable storage medium including instructions that are executed by a computational unit to perform the method described above.

[0009] The system and method disclosed herein may be implemented in any means for achieving various aspects. Other features will be apparent from the accompanying drawings and from the detailed description that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

[00010] The advantages and features of the present disclosure will become better understood with reference to the following detailed description and claims taken in conjunction with the accompanying drawings, wherein like elements are identified with like symbols, and in which:

3 [00011] FIG. 1 illustrates an example system for determining miss distance and bullet speed of a burst of bullets;

[00012] FIG. 2 illustrates an example system depicting an actual firing point, an actual CPA vector and an actual SW vector of the burst of bullets;

[00013] FIG. 3 illustrates an example flowchart for determining a miss distance and bullet speed of a burst of bullets; and

[00014] FIG. 4 illustrates a block diagram of an example computing system for determining a miss distance and bullet speed of a burst of bullets.

DETAILED DESCRIPTION OF THE INVENTION

[00015] The examples described herein in detail for illustrative purposes are subject to many variations in structure and design. Several sensors may be disposed on a platform, such as a stationary structure or a vehicle (e.g., aircraft) to track fired bullets or rounds. Example sensors may be electro-optic (EO) sensors, acoustic sensors, and the like. Some systems may use the acoustic sensors to track the bullets, whereas the other systems may use the EO sensors to track the bullets. EO sensors may detect bullets as they fly by a moving vehicle. Existing methods may track a single round. Further, the existing methods may give two pieces of information, i.e., the direction of the CPA of the round (i.e. CPA vector), and the direction of the firing point (i.e., FP vector). Acoustic sensors may detect the Shockwave (SW) that is generated by a supersonic bullet. Detected SW may be reported with the direction of the SW. The angle between the shock direction

4 vector and the CPA vector may yield miss distance and bullet speed which aids hostile intent determination.

[00016] Typically, the EO and acoustic sensor detections may be fused "round to round", i.e., attempting to calculate a CPA-shock angle between a single EO detection and a single acoustic detection. In the single round approach, one sensor may detect a round while the other may fail to detect the round.

[00017] Examples described herein provide an enhanced system, technique and a method for determining miss distance and bullet speed of bullets in a burst mode. In firearms, a burst mode or burst fire may refer to a firing mode enabling a shooter to fire a predetermined number of rounds, for example two or three rounds on hand held weapons and over 100 on anti-aircraft weapons, with a single pull of the trigger. Example firearms can include submachine guns, assault rifles, carbines, machine pistols (e.g., the Beretta 93R) and so on. Example bullet may be any projectile such as a bullet, artillery shell, missile, bombs, or other object that exhibit the characteristics consistent with a bullet in flight.

[00018] In burst mode, a tracked estimate of CPA vector (e.g., CPA direction) and SW vector (i.e., shock direction) from multiple rounds is used instead of attempting to correlate between single round detections. In other words, the correlation occurs at the "burst level" rather than the "round level". Thereby, CPA vectors and SW vectors can be correlated even when the acoustic and EO sensors do not detect the same round. By using the predicted location estimate of both the CPA vector and the SW vector rather than the raw measurements from single round, changes in the gunfire path over time can be

5 accounted. In this case, the SW vectors, the FP vectors and the CPA vectors are determined as emanating from the burst of bullets when the computed CPA-shock angle is within a predetermined range. Further, additional correlation criteria can be employed by incorporating the tracked FP estimate, i.e., a coplanar check that checks the CPA vectors, SW vectors and FP vectors are substantially coplanar, and a check that ensures the SW vector is between the FP vector and CPA vector. These additional checks may reduce any false correlation, which can be useful when reflected shocks or multiple gunners are present.

[00019] In one example, the CPA vector and FP vector may be tracked in multi-round bursts or bursts of ammunition. The SW vector is tracked in a multi-round acoustic burst. The shock angle direction may be predicted or estimated based on the CPA and SW vector from other respective bursts. Bursts are paired when the predicted/estimated FP vector, CPA vector, and SW vector are all significantly coplanar, and the shock angle between the CPA vector and the SW vector is within an expected range based on possible bullet speeds, and a round from each burst is substantially recently detected.

[00020] Further, the terms "correlation angle" and "shock angle" are used interchangeably throughout the document.

[00021] Referring now to Figure 1, the system 100 includes a target vehicle 102 (e.g., aircraft). The target vehicle 102 includes a first sensor 104, a second sensor 106 and a computational unit 108. Example first sensor 104 can include an acoustic sensor and example second sensor 106 can include an EO sensor. In the example shown in Figure 1, the sensors are disposed on the vehicle, however, the sensors can also be disposed on a

6 stationary structure. The computational unit 108 can be any combination of hardware and programming to implement the functionalities described herein. Example computational unit 108 can include a processor.

[00022] In operation, the first sensor 104 detects Shockwave (SW) vectors emanating from bullets and the second sensor 106 detects FP and CPA vectors emanating from the bullets. The SW vectors include a direction of SWs of the bullets relative to the platform. In the example shown in Figure 1, the first sensor 104 detects SW vectors SI and S2 of SW1 and SW2 emanating from the bullets Bl and B2, respectively. For example, the Shockwave is a physical and audible wave created in the air when a bullet travels at speeds faster than the speed of sound. In the example shown in Figure 1 , the Shockwave includes a mach cone shaped sound waves produced by the bullets Bl and B2.

[00023] Further in operation, the second sensor 106 detects the FP and CPA vectors emanating from the bullets. The FP vectors and the CPA vectors include a direction of FPs and a direction of CPAs, respectively, of the bullets relative to the platform. In the example shown in Figure 1 , the second sensor 106 detects FP1 and FP2 vectors and CPA1 and CPA2 vectors associated with the bullets Bl and B2, respectively. The FP is a position from which a firearm/weapon is fired. Further, a muzzle flash is produced when a weapon is fired, the muzzle flash can be used to detect/estimate the firing point of the bullets. In the example shown in Figure 1 , the muzzle flash may be a visible light that is produced by the firing of bullets from the weapon. The CPA is the position of the bullet when it is closest to the target vehicle 102, and the CPA vector is the direction of the vector pointing toward the CPA relative to the target vehicle 102. For example, the second sensor includes cameras that are disposed in the aircraft 102. These cameras

7 include a field-of-view within which the bullets (e.g., B1 and B2) may be tracked. The tracking may be done by measuring the angular positions of the bullets with respect to the platform or vehicle 102.

[00024] Furthermore, the computational unit 108 may be communicatively connected to the first sensor 104 and the second sensor 106. The computational unit 108 receives the detected SW vectors and detected FP and CPA vectors emanating from the bullets. In one example, the computational unit 108 receives the detected information (i.e., FP and CPA vectors together) from the second sensor 106 and then estimates the FP vectors and CPA vectors separately from the detected information.

[00025] Further, the computational unit 108 is configured to determine that the SW vectors, the FP vectors and the CPA vectors are emanating from the burst of bullets. In one example, the computational unit 108 computes a CPA-shock angle (e.g., CPA-shock angle 1 10) between the CPA vectors and the S W vectors and determining that the SW vectors, the FP vectors and the CPA vectors are emanating from the same burst of bullets when the computed shock angle is within a predetermined range. In another example, the computational unit 108 performs an additional coplanar check to determine whether the FP vectors, the CPA vectors, and the SW vectors are substantially coplanar and determines that the SW vectors, the FP vectors and the CPA vectors are emanating from the same burst of bullets when the FP vectors, the CPA vectors, and the SW vectors are substantially coplanar.

[00026] In yet another example, the computational unit 108 performs an additional check to determine whether the SW vectors lies in between the CPA vectors and the FP vectors

8 and determining that the SW vectors, the FP vectors and the CPA vectors are emanating from the same burst of bullets when the SW vectors lies in between the CPA vectors and the FP vectors. The one or more of these checks may ensure that the SW vectors, the FP vectors and the CPA vectors are coming from the same burst. If the detections are correlated that means they come from the same burst, then the correlated information (i.e., the SW vectors, the FP vectors and the CPA vectors) can be used to determine the miss distance and bullet speed of the bullets in the same burst. The miss distance of the burst of bullets may be determined relative to the platform. 27] The computational unit 108 is configured to determine the miss distance and bullet speed of the burst of bullets using the FP vectors, the SW vectors, and the CPA vectors upon determining that the SW vectors, the FP vectors and the CPA vectors are emanating from the same burst of bullets. In one example, the computational unit 108 computes an aggregated estimate of the SW vectors (i.e., S I , S2, and S3), an aggregated estimate of the FP vectors (e.g., Fl , F2, and F3), and an aggregated estimate of the CPA vectors (e.g., CI, C2, and C3), and determines the shock angle using the aggregated estimate of the CPA vector and the aggregated estimate of the SW vector. Computational unit 108 then computes the bullet speed using the shock angle, and then computes the miss distance using the bullet speed and the angular rate of the bullet at the CPA location. The angular rate is determined by tracking the bearing of the bullet as seen by the EO sensor. In one example, the miss distance and the bullet speed may be determined from the shock angle as follows:

9 Where, Θ is the computed shock angle between the CPA vectors and the SW vectors. From the above equation, the miss distance and bullet speed are determined as follow,

Where, the angular rate of the bullet at the CPA may be determined by tracking the bearing of the bullet using the EO sensor.

[00028] Referring now to Figure 2, which illustrates an example system 200 depicting an actual firing point, actual CPA vector and an actual SW vector of the burst of bullets. Figure 2 depicts the actual SW vector 206B, FP vector 202B, and CPA vector 204B of a bullet/burst of bullets that are computed based on the tracked/detected/predicted SW vectors 206A, FP vectors 202A and CPA 204A vectors.

[00029] FIG. 3 illustrates an example flowchart for determining miss distance and bullet speed of a burst of bullets. At block 302, shock wave (SW) vectors emanating from bullets are estimated/predicted using a first sensor. Example first sensor is an acoustic sensor. The SW vectors include a direction of SWs of the bullets relative to the platform. At block 304, firing point (FP) vectors and closest-point-of-approach (CPA) vectors emanating from the bullets are estimated/predicted using a second sensor. Example second sensor is an electro-optic sensor. The FP vectors and the CPA vectors include a direction of FPs and a direction of CPAs, respectively, of the bullets relative to the platform. The first sensor and the second sensor are disposed on a platform such as a stationary platform or a vehicle (e.g., Aircraft on fly).

[00030] At block 306, the SW vectors, the FP vectors and the CPA vectors are determined as emanating from the burst of bullets. In one example, a shock angle between the CPA vectors and the SW vectors is computed. Further, the SW vectors, the FP vectors and the CPA vectors are determined as emanating from the burst of bullets when the computed shock angle is within a predetermined range. In another example, a coplanar check is performed to determine whether the FP vectors, the CPA vectors, and the SW vectors are substantially coplanar. Further, the SW vectors, the FP vectors and the CPA vectors are determined as emanating from the burst of bullets when the FP vectors, the CPA vectors, and the SW vectors are substantially coplanar. In yet another example, a check is made to determine whether the SW vectors lies in between the CPA vectors and the FP vectors. Further, the SW vectors, the FP vectors and the CPA vectors are determined as emanating from the burst of bullets when the SW vectors lies in between the CPA vectors and the FP vectors.

[00031] At block 308, the miss distance and bullet speed of the burst of bullets are determined using the FP vectors, the SW vectors, and the CPA vectors that are emanating from the burst of bullets. In one example, an aggregated estimate of the SW vectors, an aggregated estimate of the FP vectors, and an aggregated estimate of the CPA vectors are computed. Then, the miss distance and bullet speed of the burst of bullets are determined using the aggregated estimate of the SW vectors, the aggregated estimate of the FP vectors and the aggregated estimate of the CPA vectors. [00032] FIG. 4 illustrates a block diagram of an example computing system 400 for determining miss distance and bullet speed of a burst of bullets in a burst mode. The computing system 400 includes a processor 402 and a machine-readable storage medium 404 communicatively coupled through a system bus. The processor 402 may be any type of central processing unit (CPU), microprocessor, or processing logic that interprets and executes machine-readable instructions stored in the machine-readable storage medium 404. The machine-readable storage medium 404 may be a random access memory (RAM) or another type of dynamic storage device that may store information and machine-readable instructions that may be executed by the processor 402. For example, the machine-readable storage medium 404 may be synchronous DRAM (SDRAM), double data rate (DDR), Rambus® DRAM (RDRAM), Rambus® RAM, etc., or storage memory media such as a floppy disk, a hard disk, a CD-ROM, a DVD, a pen drive, and the like. In an example, the machine-readable storage medium 404 may be a non- transitory machine-readable medium. In an example, the machine-readable storage medium 404 may be remote but accessible to the computing system 400.

[00033] The machine-readable storage medium 404 may store instructions 406, 408, 410, and 412. In an example, instructions 406, 408, 410, and 412 may be executed by processor 402 for determining the miss distance and bullet speed of the bullet in the burst mode.

[00034] Some or all of the system components and or data structures may also be stored as contents (e.g., as executable or other machine-readable software instructions or structured data) on a non-transitory computer-readable medium (e.g., as a hard disk; a computer memory; a computer network or cellular wireless network or other data transmission medium; or a portable media article to be read by an appropriate drive or via an appropriate connection, such as a DVD or flash memory device) so as to enable or configure the computer-readable medium and/or one or more host computing systems or devices to execute or otherwise use or provide the contents to perform at least some of the described techniques. Some or all of the components and/or data structures may be stored on tangible, non-transitory storage mediums. Some or all of the system components and data structures may also be provided as data signals (e.g., by being encoded as part of a carrier wave or included as part of an analog or digital propagated signal) on a variety of computer-readable transmission mediums, which are then transmitted, including across wireless-based and wired/cable-based mediums, and may take a variety of forms (e.g., as part of a single or multiplexed analog signal, or as multiple discrete digital packets or frames). Such computer program products may also take other forms in other embodiments. Accordingly, embodiments of this disclosure may be practiced with other computer system configurations. 35] The above-described examples of the present solution are for the purpose of illustration only. Although the solution has been described in conjunction with a specific embodiment thereof, numerous modifications may be possible without materially departing from the teachings and advantages of the subject matter described herein. Other substitutions, modifications and changes may be made without departing from the spirit of the present solution. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 36] The present description has been shown and described with reference to the foregoing examples. It is understood, however, that other forms, details, and examples can be made without departing from the spirit and scope of the present subject matter that is defined in the following claims.