EP3134702B1 - Proximity fuze, and projectile provided with such a proximity fuze - Google Patents

Description

The present invention relates to a proximity rocket, in particular adapted to equip ammunition medium caliber. It also relates to a projectile equipped with such a proximity rocket.

Attack helicopters are usually equipped with a medium caliber gun placed in a turret. The ammunition used is equipped with an impact rocket initiating the explosive charge of the shell in contact with the target or the ground. During an impact on the ground the shell inevitably bury itself before being fired, even if the delay is weak. This configuration brings a considerable loss of efficiency, especially as the explosive charge is relatively low.
One solution to increase the efficiency is to trigger the firing before the impact, close to the target or the ground by equipping the explosive projectile with a proximity rocket.
Given the particular configuration of the shots from a helicopter, at low altitude, this proximity rocket must be compatible very grainy shooting paths. In addition, the ammunition must be completely autonomous without requiring interaction with the weapon system.
The need for a munition operating completely independently of a weapon system prohibits certain technical solutions such as those based on a chronometric function, for example a function called "airburst" programmable time. This type of chronometric solution requires a programming of the ammunition. In addition, the chronometric principle has a major disadvantage. This disadvantage is the limited, unsupported accuracy of the effectiveness of medium caliber ammunition for which the desired accuracy is of the order of a few tens of centimeters for a nominal detection distance of between 0.5 meters and 2 meters in particular.

• Intégrable dans une fusée d'ogive de calibre 30 mm, notamment ;
• Totalement autonome, ne nécessitant aucune intégration dans un système d'armes ;
• Fonctionnant dans les configurations de tir depuis un hélicoptère, en trajectoire rasante.

Le besoin peut être étendu à d'autres calibres et pour des tirs depuis des porteurs différents des hélicoptères, des véhicules au sol par exemple.
Un document EP 0 314 646 A2 divulgue des dispositifs de transmission et de réception faisant partie d'une fusée optique de proximité.There is therefore a need to realize a proximity detection device, or proximity rocket:

• It can be integrated in a 30 mm caliber warhead, in particular;
• Totally autonomous, requiring no integration into a weapons system;
• Operating in shooting configurations from a helicopter, grazing trajectory.

The need can be extended to other calibres and for shots from different carriers of helicopters, ground vehicles for example.
A document EP 0 314 646 A2 discloses transmitting and receiving devices forming part of a proximity optical fuse.

• un dispositif d'émission ayant une pupille émettant un faisceau lumineux vers l'avant de ladite fusée ;
• un dispositif de réception ayant une pupille détectant les flux lumineux dans un cône vers l'avant de ladite fusée, ledit faisceau lumineux et ledit cône ayant des orientations relatives telles qu'ils se croisent, la pupille d'émission et la pupille de réception étant excentrées ;

un volume de détection étant le volume où ledit faisceau lumineux croise ledit cône de sorte que lorsqu'un obstacle est dans ledit volume de détection, la lumière émise par ledit dispositif d'émission est rétrodiffusée vers ledit dispositif de détection, un obstacle à proximité étant détecté par la détection du maximum de puissance rétrodiffusée, ledit cône pour la réception étant centré sur l'axe de ladite fusée.The invention therefore aims to overcome the aforementioned drawbacks and meet the need expressed above. For this purpose, the object of the invention is a proximity rocket capable of equipping a projectile, said rocket having the function of detecting an obstacle in the vicinity, a nearby obstacle being defined as being an obstacle having a minimum distance to said rocket, said rocket comprising at least:

• an emitting device having a pupil emitting a light beam towards the front of said rocket;
• a receiving device having a pupil detecting luminous flux in a cone towards the front of said fuze, said light beam and said cone having relative orientations as they intersect, the transmitting pupil and the receiving pupil being eccentric;

a detection volume being the volume where said light beam crosses said cone so that when an obstacle is in said detection volume, the light emitted by said transmitting device is backscattered towards said detection device, a nearby obstacle being detected by the detection of the maximum backscattered power, said cone for the reception being centered on the axis of said rocket.

The receiving pupil has for example a crescent moon shape.

In a particular embodiment, the fuse delivers a signal if at least one condition is satisfied, said condition being the detection of said backscattered power maximum. Said signal is for example delivered if a second condition is satisfied, said second condition being that said maximum backscattered power exceeds a given threshold. Said signal is for example able to trigger the firing of an explosive charge.

The transmission beam is for example coded to allow its identification by said receiving device, said light beam being for example modulated. The light beam can be produced by a laser diode or a light emitting diode (LED).

The invention also relates to a projectile equipped with a rocket as described above. In one possible embodiment, said projectile comprises a medium-caliber type of ammunition. It is for example suitable for being fired from an airborne platform and / or from a platform on the ground.

• La figure 1, un exemple d'utilisation d'un dispositif selon l'invention, dans le cas de tirs de projectiles depuis un hélicoptère ;
• Les figures 2a et 2b, un exemple de fusée de proximité selon l'art antérieur ;
• La figure 3, une illustration du principe de fonctionnement d'une fusée de proximité selon l'invention ;
• Les figures 4a et 4b, une illustration d'un mode de réalisation possible d'une fusée selon l'invention ;
• La figure 5, l'allure d'un signal reçu ; et
• La figure 6, un exemple de réalisation d'une fusée selon l'invention.

Other characteristics and advantages of the invention will become apparent with the aid of the following description made with reference to appended drawings which represent:

• The figure 1 an example of use of a device according to the invention, in the case of firing projectiles from a helicopter;
• The Figures 2a and 2b an example of a proximity rocket according to the prior art;
• The figure 3 , an illustration of the principle of operation of a proximity fuse according to the invention;
• The Figures 4a and 4b an illustration of a possible embodiment of a rocket according to the invention;
• The figure 5 , the appearance of a received signal; and
• The figure 6 , an embodiment of a rocket according to the invention.

The figure 1 illustrates a case of use of a device according to the invention. A helicopter 1 flying at low altitude fires a projectile equipped with a rocket close to the ground 2, the medium caliber ammunition following a grazing firing trajectory. A function of the proximity detection device equipping the munition is to allow an explosion 4 of the latter at the most appropriate time before the impact on the ground, when the distance between the proximity rocket and the target becomes less than one. given threshold. The goal is for the target to be detected before the projectile explodes or enters. The invention can also be applied for firing projectiles from other airborne platforms. It can also apply for projectiles fired from platforms on the ground, for example vehicles.

The Figures 2a and 2b show an example of proximity fuzes 21 according to the prior art.
Proximity rockets for mortar or artillery projectiles are designed to detect the ground by considering angles of arrival generally between 15 ° and 80 °. The Figures 2a and 2b present two typical configurations of the main transmission lobe 28, 29 obtained on radio frequency (RF) based proximity fuzes, based on electromagnetic sensors of the miniaturized radar type, for example. On the figure 2a , the main emission lobe 28 has an opening angle of the order of 30 ° to 45 ° relative to the axis 20 of the rocket. On the figure 2b the main emission lobe 29, located laterally, has a large angular aperture.
As previously mentioned, a medium caliber application is characterized by extremely low target angles of arrival (angle of incidence with respect to the ground).
The implementation of a proximity function must therefore meet the need for reliable operation at angles of arrival of less than a few degrees. The trigger distances, related to the effectiveness of the munition, also need to be greatly reduced, these distances may be between 0.5 meters and 1.5 meters for example. The operation of a proximity fuse for very low angles of incidence then requires a highly directional detector, in other words a particularly thin emission lobe, in particular to avoid the risk of false alarms due to obstacles. located near the trajectory of the ammunition. The configurations of Figures 2a and 2b do not respond to this need.

In particular, with respect to RF technology, the increase in directivity can be achieved by operating at higher working frequencies and by using antenna arrays. However, despite these adaptations, and in operation in the band KA, obtaining angles of opening of less than 15 ° remains difficult to achieve. An RF solution therefore does not allow to answer easily, and cheaply, if necessary. Moreover, it is important to note that the operation of an RF proximity fuse at such high frequencies, in addition to the increased sensitivity to the environment, raises the problem of the availability of components and consequently the cost of serial of production as just mentioned.
The cost performance ratio of the RF solution is that it is not adapted to meet the need expressed optimally.

• Un dispositif d'émission émettant un faisceau lumineux 31 vers l'avant de la munition, le faisceau ayant la forme d'un cône étroit, ayant une ouverture angulaire inférieure au degré ;
• Un dispositif de réception détectant un flux lumineux 32 dans un cône étroit vers l'avant de la munition, formant un cône de détection ou cône de réception ;
• Des moyens de traitement des signaux reçus.

La puissance émise est avantageusement de l'ordre de quelques milliwatts.
La pupille 33 de l'émission et la pupille 34 de la réception sont séparées de façon notamment à ce que les deux cônes 31, 32 se croisent devant la munition. Le volume de détection est le volume 35 où le faisceau lumineux 35 est dans le cône de réception 34. Ce volume est avantageusement centré sur l'axe 40 de la munition, axe commun à la fusée. Lorsque la munition se rapproche dans un premier temps la tache de l'émission sur l'obstacle est en dehors du cône de réception 32. Il n'y a pas de signal détecté.
Puis, l'obstacle se rapprochant, la tache sur l'obstacle entre dans le champ de réception. Le signal augmente avec l'augmentation de la fraction de la tache dans le du cône de réception 32.
La tache de l'émission sur l'obstacle entre dans la zone de détection. La fraction de la tache de l'émission sur l'obstacle augmente avec le rapprochement de la munition. Lorsque toute la tache est dans le cône de réception 32 le flux rétrodiffusé à détecter croit comme l'inverse du carré de la distance à l'obstacle.
Enfin la tache de l'émission sur l'obstacle sort progressivement du cône de réception 32. Le flux détecté décroît rapidement lorsque le cône d'émission 31 sort du cône de réception 32. Ce passage par un maximum du flux détecté est le repère temporel de proximité de l'obstacle.
Les figures 4a et 4b illustrent plus précisément un mode de réalisation possible correspondant à l'exemple de la figure 3. Les pupilles d'émission et les pupilles de réception sont représentées sur la figure 4a par une vue en coupe des cônes d'émission 31 et de réception 32, à proximité des pupilles. Cette figure 4a montre que les pupilles d'émission et de réception sont excentrées. Plus précisément la pupille de réception a une forme en croissant de lune inscrit dans un cercle 10, la pupille d'émission est située en dehors de ce croissant, centrée sur l'intersection de l'axe de symétrie du croissant et du cercle 10. La pupille d'émission 31 peut-être située à un autre endroit par rapport au croissant, tout en étant excentrée par rapport à celui-ci. Comme le montre la figure 4b, les cônes d'émission 31 et de réception 32 se croisent, ceux-ci étant représentés par une vue en coupe longitudinale, le cône d'émission 31 entrant dans le cône de réception devant la munition.The figure 3 illustrates the principle of operation of a proximity fuse 30 according to the invention. The rocket 30 uses a laser source as the emission source. More particularly, a proximity fuse according to the invention comprises in particular:

• An emission device emitting a light beam 31 towards the front of the munition, the beam having the shape of a narrow cone, having an angular aperture smaller than the degree;
• A reception device detecting a luminous flux 32 in a narrow cone towards the front of the munition, forming a detection cone or receiving cone;
• Means for processing the received signals.

The power emitted is advantageously of the order of a few milliwatts.
The pupil 33 of the emission and the pupil 34 of the reception are separated in such a way that the two cones 31, 32 intersect in front of the munition. The detection volume is the volume 35 where the light beam 35 is in the receiving cone 34. This volume is advantageously centered on the axis 40 of the ammunition, axis common to the rocket. When the ammunition is approaching at first the stain of the emission on the obstacle is outside the cone of reception 32. There is no signal detected.
Then, the obstacle getting closer, the stain on the obstacle enters the field of reception. The signal increases with the increase of the fraction of the spot in the cone of reception 32.
The emission spot on the obstacle enters the detection zone. The fraction of the stain of the emission on the obstacle increases with the approximation of the ammunition. When the whole spot is in the reception cone 32, the backscattered flux to be detected increases as the inverse of the square of the distance to the obstacle.
Finally, the stain of the emission on the obstacle progressively leaves the reception cone 32. The detected flux decreases rapidly when the emission cone 31 leaves the reception cone 32. This passage through a maximum of the detected flux is the temporal reference proximity of the obstacle.
The Figures 4a and 4b illustrate more precisely one possible embodiment corresponding to the example of the figure 3 . The transmission pupils and the reception pupils are represented on the figure 4a by a sectional view of the emission cones 31 and reception 32, near the pupils. This figure 4a shows that the transmit and receive pupils are eccentric. More precisely, the reception pupil has a shape in crescent moon inscribed in a circle 10, the emission pupil is located outside this crescent, centered on the intersection of the axis of symmetry of the crescent and the circle 10. The sending pupil 31 may be located in another place with respect to the crescent, while being eccentric with respect to this one. As shown in figure 4b the transmitting and receiving cones 32 cross each other, these being represented by a longitudinal sectional view, the transmission cone 31 entering the receiving cone in front of the munition.

The figure 5 illustrates the detection principle explained above corresponding in particular to the exemplary embodiment of Figures 4a and 4b . The power of the signal received on the ordinate is a function of the distance to the target, on the abscissa.
A curve 61 represents the signal received in the case of a modulated transmitted signal. The passage to the maximum 62 of received power serves as a distance reference to the obstacle.

In this case, at a great distance from the obstacle or the target, the receiving pupil collects the backscattered flux by the obstacle illuminated by the emission beam 31. By approaching, the signal increases according to the inverse of the square of the distance from the ammunition to the obstacle. Then the signal reaches a maximum 62 when the backscattered stream no longer reaches the entire receiving pupil in the receiving field. Then, the signal decreases rapidly until the emission spot is no longer visible by the reception.
The received signals are for example digitized and analyzed by the processing means.

• Un émetteur à diode laser 51, produisant une émission lumineuse de faible divergence, la pupille 33 ;
• Un récepteur 52 réalisant une détection mono élément dont le cône est étroit, quelques milliradians par exemple, observant vers l'avant de la fusée précisément dans la direction de déplacement de la munition, de préférence la pupille 34 est centrée dans l'avant de la fusée et dans tous les cas séparée de la pupille 33 d'émission ;

L'alignement de l'axe du cône de réception 32 sur l'axe 40 de la munition permet avantageusement au flux lumineux venant de l'obstacle éclairé par la lumière ambiante de varier lentement malgré la rotation de la munition, ce qui facilite la détection de l'émission sur l'obstacle. Egalement, la puissance émise peut ainsi être avantageusement réduite. La détection du récepteur est synchrone de l'émission. La direction d'émission croise le cône de réception, pas nécessairement sur l'axe de la munition. L'émission est par exemple codée et modulée pour faciliter son identification par le récepteur. L'émetteur est par exemple placé sur un premier circuit imprimé 53 dont le plan est perpendiculaire à l'axe 40 de la fusée. L'émetteur est par exemple placé dans une position excentrée de façon à croiser les faisceaux d'émission et de réception comme illustré par la figure 3. Le premier circuit imprimé comporte par exemple les moyens de codage ou de modulation de l'onde émise.
Le récepteur 52 est par exemple monté sur un deuxième circuit imprimé 54 dont le plan contient l'axe 40 de la fusée. Le récepteur 52 est par exemple positionné sur cet axe 40, vers l'avant conformément à la position centrée de la pupille 34. Le deuxième circuit imprimé 54 comporte par exemple les moyens de traitement. Ces moyens de traitement détectent notamment un obstacle à proximité conformément à la méthode décrite à la figure 4. En particulier, les moyens de traitement reçoivent du récepteur le signal reçu numérisé selon une fréquence d'échantillonnage adéquat. Les signaux reçus sont par exemple numérisés à l'intérieur du récepteur qui effectue la conversion numérique de la puissance de signal reçu. A partir de ces données numérisées, les moyens de traitement détectent le maximum. Lorsque ce maximum est détecté, les moyens de traitement envoient par exemple un signal pour activer l'explosion de la charge portée par le projectile équipé de la fusée de proximité selon l'invention. La détection du maximum permet de s'affranchir des variations du niveau du signal reçu à cause de la nature de l'obstacle. Un obstacle clair renverra plus de lumière qu'un obstacle foncé. Le maximum est à une distance fixe de la munition du fait de la géométrie relative du cône d'émission 31 et du cône de réception 32. Un seuil de niveau de puissance reçue peut être combiné avec la détection du maximum de puissance reçue. Ceci pour éviter de déclencher sur des signaux trop faibles d'origine parasite.The figure 6 presents a preferred embodiment of a proximity fuse according to the invention. It involves :

• A laser diode transmitter 51, producing a light emission of low divergence, the pupil 33;
• A receiver 52 performing a single-element detection whose cone is narrow, some milliradians, for example, looking forward to the rocket precisely in the direction of movement of the munition, preferably the pupil 34 is centered in the front of the rocket and in all cases separated from the pupil 33 of emission;

The alignment of the axis of the reception cone 32 on the axis 40 of the munition advantageously allows the luminous flux coming from the obstacle illuminated by the ambient light to vary slowly despite the rotation of the munition, which facilitates the detection of emission on the obstacle. Also, the emitted power can be advantageously reduced. The detection of the receiver is synchronous with the emission. The direction of emission crosses the cone of reception, not necessarily on the axis of the ammunition. The transmission is for example coded and modulated to facilitate its identification by the receiver. The transmitter is for example placed on a first printed circuit 53 whose plane is perpendicular to the axis 40 of the rocket. For example, the transmitter is placed in an eccentric position so as to intersect the transmit and receive beams as illustrated by FIG. figure 3 . The first printed circuit comprises, for example, coding or modulation means for the transmitted wave.
The receiver 52 is for example mounted on a second printed circuit 54 whose plane contains the axis 40 of the rocket. The receiver 52 is for example positioned on this axis 40, forwards in accordance with the centered position of the pupil 34. The second printed circuit 54 comprises for example the processing means. These processing means detect in particular a nearby obstacle in accordance with the method described in figure 4 . In particular, the processing means receive from the receiver the received signal digitized at an adequate sampling frequency. The received signals are for example digitized inside the receiver which performs the digital conversion of the received signal power. From these digitized data, the processing means detect the maximum. When this maximum is detected, the processing means send for example a signal to activate the explosion of the load carried by the projectile equipped with the proximity rocket according to the invention. Detection of maximum makes it possible to overcome variations in the level of the signal received because of the nature of the obstacle. A clear obstacle will return more light than a dark obstacle. The maximum is at a fixed distance from the munition due to the relative geometry of the emission cone 31 and the reception cone 32. A received power level threshold can be combined with the detection of the maximum power received. This is to avoid triggering on weak signals of parasitic origin.

The invention can also be integrated as a proximity function, in any ammunition rocket, including in indirect fire configurations, such as artillery or mortar. It is also suitable for all types of gauges.

Claims (12)

1. A proximity fuse able to be fitted to a projectile, said fuse having the mission of detecting an obstacle (2) in proximity, an obstacle in proximity being defined as being an obstacle exhibiting a minimum distance from said fuse, said fuse (30) comprising at least:

   - an emission device (51, 33) having an emission pupil (33) emitting a light beam (31) directed forward of said fuse;

   - a reception device (52, 34) having a reception pupil (34) detecting the luminous fluxes in a reception cone (32) forward of said fuse, said light beam and said reception cone having relative orientations such that they cross one another, the emission pupil (31) and the reception pupil (32) being off-centred;

   a detection volume (35) being the volume where said light beam crosses said cone so that when an obstacle is in said detection volume, the light emitted by said emission device is backscattered toward said detection device, an obstacle in proximity being detected by detecting the maximum of backscattered power (62, 72), characterised in that said reception cone (32) is centred on the axis (40) of said fuse.
2. The proximity fuse according to claim 1, characterised in that the reception pupil (32) has a crescent moon shape.
3. The proximity fuse according to any one of the preceding claims, characterised in that it delivers a signal if at least one condition is satisfied, said condition being the detection of said maximum of backscattered power.
4. The proximity fuse according to claim 3, characterised in that said signal is delivered if a second condition is satisfied, said second condition being that said maximum of backscattered power exceeds a given threshold.
5. The proximity fuse according to any one of claims 3 or 4, characterised in that said signal is able to trip the detonation (4) of an explosive charge.
6. The proximity fuse according to any one of the preceding claims, characterised in that the emission beam (31) is coded to allow its identification by said reception device.
7. The fuse as claimed in claim 6, characterised in that said light beam is modulated.
8. The proximity fuse according to any one of the preceding claims, characterised in that the light beam is produced by a laser diode or a light-emitting diode.
9. A projectile, characterised in that it is fitted with a proximity fuse according to any one of the preceding claims.
10. The projectile according to claim 9, characterised in that it comprises a munition of medium calibre type.
11. The projectile according to any one of the preceding claims, characterised in that it is able to be fired from an airborne platform (1).
12. The projectile according to any one of claims 1 to 10, characterised in that it is able to be fired from a ground platform.

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