Method and device for projectile measurements

Details Method and device for projectile measurements Method and device for projectile measurements

1999-02-26

2001-03-06

Pihulic, Daniel T. (Department: 3662)

Communications, electrical: acoustic wave systems and devices

Distance or direction finding

With time interval measuring means

Reexamination Certificate

active

06198694

ABSTRACT:

TECHNICAL FIELD
This invention relates to a method and a device for deciding, relative to a chosen reference system and without contact, the position, direction or speed, or any combination thereof, for a projectile during its flight through a gas towards a given target, where the position of the projectile, in at least one plane, is determined at a certain distance from the target by means of at least three acoustic sensors arranged in the vicinity of said plane.
DESCRIPTION OF THE PRIOR ART
A common application in the above mentioned technical field is target shooting with small-arms, e.g. rifles or pistols, at some form of target. It can for instance be a conventional target practising panel with concentric rings, where scores are given depending on the bullet hit point relative to the target panel centre. A common form of military target shooting is shooting against so called pop-up targets, i.e. target panels picturing e.g. an enemy soldier, which at irregular time intervals are raised in the terrain in front of the shooter. The shooter's task is, as quickly as possible, to give fire against the said target, and if the shooter hits the target, the target drops down.
There are different ways to indicate hits in a target shooting system as described above. The simplest is to simply use conventional target panels of wood, cardboard or similar material, which are thin enough to be penetrated by a bullet. The hit point of the bullet in the target is in this way visible to the naked eye, at least at close distance.
Another known way to detect the hit point of the bullet is to use acoustic sensors, which are fixed to the target panel and which are arranged to detect the vibrations or sound waves, which are generated in the hit point and propagate concentrically in the target panel around the hit point. In the American patent publication U.S. Pat. No. 5,095,433 a target shooting system is shown, wherein a range of vibration sensors are arranged at different places on the target panel with known relative distances. The vibration sensors are arranged to detect vibrations or sound waves in the target panel, when a bullet hits the latter, and supply electric signals to a microprocessor as a result thereof. By registering the time differences for the hit signals from the respective sensor the microprocessor can, by triangulation, decide the hit point of the bullet in the target panel. The result is presented by a synthetic voice announcing the result through a loud-speaker. Systems of this nature have the drawback that since the sensors are fixed in connection with the target panel, they suffer a great risk of, sooner or later, being hit by an incoming bullet resulting in destruction of the hit sensors.
In a different target shooting system non-contact detection of the position of the projectile is used. Here, non-contact detection means that the sensors used for detection are arranged at a certain distance from the target panel, wherein the risk for destruction through a bullet hit is considerably reduced or even completely eliminated. A number of different systems for such non-contact detection with acoustic sensors are known today through e.g. the European patent publications EP-B1-0 259 428 and EP-B1-0 157 397, the American patent publications U.S. Pat. Nos. 5,247,488 and 5,349,853, the Swedish patent publication SE-B-467 550 and the German patent publication DE-C2-41 06 040. In SE-B-439 985 a system for deciding the position of high-speed projectiles is shown, wherein the passage of the projectile through two parallel planes is detected with three acoustic transducers for each plane. All of these inventions relate to the detection of so called supersonic projectiles, i.e. such projectiles, which travel faster than the sound in the same medium (normally air). Such projectiles can e.g. be anti-aircraft projectiles for shooting against towed air target, bullets from high-speed small-arms, etc.
Common to the above-mentioned inventions is that they all use the so called Mach cone, which is generated around a supersonic projectile. The Mach cone is a pressure or bow wave (sometimes called sound bang), which is generated when a supersonic projectile “overtakes” its own sound, whereby a strong conical pressure change is generated around the projectile. The cone angle of the Mach cone depends on the so called Mach index, M, which is defined as the quotient between the speed of the projectile and the speed of sound. When the sound bang reaches the sensors, it is converted to a rapid, almost N-shaped electrical pulse, which can be used in analogy with the above to decide the time differences between the electrical signals and thereafter, e.g. by triangulation, decide the position of the projectile in some plane. Certain systems of this kind use other acoustic information as well, such as hit sound or firing sound.
However, not all projectiles travel faster than sound (M>1). Many simpler small-arms fire bullets, which travel slower than sound. For pistols with 9 mm ammunition a bullet speed of around 300 m/s (M≈0,9) may appear, and the corresponding speed for 5,6 mm ammunition may be 250 m/s (M≈0,7). For 0.22 rifles a bullet speed as low as 140 m/s (M≈0,4) can be found. Since a sub-sonic projectile does not create a Mach cone or a sound bang, the above-mentioned systems are not applicable for the detection of such projectiles.
SUMMARY OF THE INVENTION
The object of this invention is to make possible non-contact measurement of position, direction or speed for a projectile, e.g. a bullet, which is fired at a target panel from small-arms, without using neither firing sound nor target hit sound for the measurement. In particular, this invention is directed towards making measurements possible as above for such projectiles, that travel at a speed, which is below the speed of sound in the same gaseous medium (M<1), and that do not create any sound bang.
The object is achieved by a method and a device with the features, which are to be found in the characterising part of the enclosed independent patent claims. Preferred embodiments of the invention are defined by the appended sub-claims.


REFERENCES:
patent: 3445808 (1969-05-01), Johnson
patent: 4261579 (1981-04-01), Bowyer et al.
patent: 4333170 (1982-06-01), Mathews et al.
patent: 4505481 (1985-03-01), Knight
patent: 4805159 (1989-02-01), Negendank et al.
patent: 5095433 (1992-03-01), Botarelli et al.
patent: 5241518 (1993-08-01), McNelis et al.
patent: 5247488 (1993-09-01), Borberg et al.
patent: 5258962 (1993-11-01), Karlsen
patent: 5349853 (1994-09-01), Oehler
patent: 4106040 (1992-08-01), None
patent: 157397 (1985-10-01), None
patent: 259428 (1991-06-01), None
patent: 439985 (1985-07-01), None
patent: 467550 (1990-01-01), None

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