EP1096219B1 - Method and system for detecting a threat thrown towards a fixed or mobile object - Google Patents

Description

The present invention relates to a method and system to detect a threat fired at a fixed or mobile object, in particular an ammunition whose trajectory is close of an armored vehicle.

We currently know a large number of ammunition, rockets or other shells. We also know decoy, masking or scrambling techniques for protect themselves against these munitions. However, these techniques cannot be used when the ammunition has undergone a hardening treatment or when these munitions are fired at distances too short for the means of decoy, masking or jamming can be oriented and implemented on time.

When the ammunition is fired at close range or is insensitive to interference or decoy a form of protection may consist in attacking the ammunition physically, for example by mechanical effect, nearby of the armored vehicle and just before impact, by projecting towards it vulgarizing elements such as plates or bars. The purpose of this attack is to reduce sufficient ammunition perforation capacity of so that its residual effect is absorbed by the vehicle armor.

• que la vitesse de la munition peut varier de 200 m/s à 1 000m/s pour les missiles et les roquettes, et de 1 000 m/s à 2 000 m/s pour les obus,
• que le diamètre de la munition peut aller d'environ 1 cm pour les obus type flèche à plus de 20 cm pour les missiles, et
• que la longueur de la munition est généralement supérieure à 60 cm.

Concretely, the implementation of this type of protection requires the calculation of the interception point between the response vector, which is fired from the tank, and the ammunition, which requires to detect the arrival of the ammunition, to identify it as such and to precisely determine its trajectory and speed, knowing:

• that the speed of ammunition can vary from 200 m / s to 1000 m / s for missiles and rockets, and from 1000 m / s to 2000 m / s for shells,
• that the diameter of the ammunition can range from approximately 1 cm for arrow type shells to more than 20 cm for missiles, and
• that the length of the ammunition is generally greater than 60 cm.

Generally speaking, dealing with threats such as that missiles is easier than that of projectiles kinetics for reasons of speed, approach and vulnerability. Indeed, for missiles, the impact of a or several fragments or small projectiles projected at from the armored vehicle may be sufficient to neutralize these missiles. This type of defense simplifies detection as well, as there is no need to know precisely the trajectory and the point of impact, that treating the response with charges with flashes.

On the other hand, the treatment of kinetic projectiles is otherwise more complex due to their high speed, the need to attack projectiles with energy very important, which requires precise knowledge of the trajectory of the projectile because we cannot consider project a large material from an armored vehicle speed over a very large surface or angle.

It is therefore necessary to have a means of threat detection that may be able to identify it with extreme reliability to avoid false alarms do not trigger unwanted responses to from the armored vehicle, locate it with extreme precision of the order of a few centimeters, and to have a response time compatible with further processing of the threat.

From these conditions, several types of solutions have already been considered.

A known solution consists in using a radar centimeter or millimeter, but this solution has major drawbacks, namely: few accuracy in locating the threat, and the fact that this speed camera is a non-discreet and expensive active element.

Other known solutions are based on imaging sensors associated with image processing, but this type of solution leads to the use of sensors able to work at acquisition frequencies of several kHz. Although such sensors begin to exist in the visible or near infrared spectral band, they are not very suitable for passive use because it is necessary to light the scene. FR-2570835-A1 describes a device for optical detection of the passage of a mobile through an area of a plane and of locating the point of crossing of the plane by said mobile.

Finally, we also find in the literature solutions showing means combining radar and optronics, but these solutions lead to costs of particularly high implementation.

The object of the invention is to design a method of detection of a threat that can overcome the disadvantages on the one hand, and can be implemented by a reliable and inexpensive system on the other hand.

• à définir en avant d'une zone de l'objet au moins deux champs d'observation tels que la menace soit obligée de traverser ces deux champs avant d'atteindre ladite zone de l'objet,
• à détecter les points d'entrée et de sortie de la menace dans chaque champ d'observation, et leurs coordonnées par rapport à un système de référence,
• à calculer les temps mis par la menace pour traverser chaque champs d'observation et pour passer d'un champ d'observation à l'autre, et
• à calculer à partir des coordonnées des points d'entrée et de sortie d'une part, et des temps de traversée de la menace d'autre part, au moins la vitesse et la trajectoire de la menace pour permettre à l'objet de pouvoir déclencher une riposte appropriée contre la menace.

To this end, the invention proposes a method for detecting a threat fired towards a fixed or mobile object, in particular a munition with high perforating power, at a short distance from an armored vehicle, the method being characterized in that it consists :

• to define in front of an area of the object at least two fields of observation such that the threat is forced to cross these two fields before reaching said area of the object,
• to detect the entry and exit points of the threat in each field of observation, and their coordinates relative to a reference system,
• to calculate the time taken by the threat to cross each field of observation and to pass from one field of observation to another, and
• to calculate from the coordinates of entry and exit points on the one hand, and crossing times of the threat on the other hand, at least the speed and trajectory of the threat to allow the object of power trigger an appropriate response to the threat.

Generally, the method consists in defining each field of observation from photo-detectors arranged in lines in a substantially vertical plane by on the one hand, and on the other hand part, to define two vertical planes forming a dihedral and delimiting each field of observation in the form of a angular sector.

In particular, the method consists in defining each dihedral plan of a field of observation from a pair of arrays or arrays of photo-detectors, these two pairs being located at a distance from each other for that the two fields of observation intercept one with the other.

The method also includes identifying the type of the threat by calculating its length taking into account between other of the time required for the threat to cross at minus a field of observation.

Advantageously, the method consists in measuring the threat surface temperature to identify it with more precision, especially when the threat is a arrow projectile and for this purpose the process consists of use photo-detector arrays sensitive to different wavelengths in the range of thermal infrared.

• des barrettes ou des matrices de photo-détecteurs associées à un dispositif optique pour définir au moins deux champs d'observation en avant d'une zone de l'objet, et
• des moyens de traitement analogique et numérique qui sont reliés aux dits photo-détecteurs pour détecter l'arrivée d'une menace qui traverse les deux champs d'observation à partir des signaux analogiques délivrés par les photo-détecteurs, et pour calculer au moins la vitesse, la trajectoire et la longueur de la menace.

The subject of the invention is also a system for detecting a threat fired towards a fixed or mobile object for the implementation of the method as defined above, characterized in that it comprises:

• bars or arrays of photo-detectors associated with an optical device to define at least two fields of observation in front of an area of the object, and
• analog and digital processing means which are connected to said photo-detectors to detect the arrival of a threat which crosses the two fields of observation on the basis of analog signals delivered by the photo-detectors, and to calculate at least the speed, trajectory and length of the threat.

• chaque champs d'observation est défini à partir d'une paire de deux barrettes adjacentes de photo-détecteurs montées dans un plan sensiblement vertical par rapport à l'objet, et
• les deux paires de barrettes de photo-détecteurs sont portées par l'objet et situées à distance l'une de l'autre pour que les deux champs d'observation qu'elles définissent s'interceptent l'un avec l'autre.

In a general way :

• each field of observation is defined from a pair of two adjacent arrays of photo-detectors mounted in a plane substantially vertical relative to the object, and
• the two pairs of photo-detector arrays are carried by the object and located at a distance from each other so that the two fields of observation that they define intercept each other.

The system for implementing the method presents in particular the advantage of being not very complex, while with good reliability in the treatment of threats likely to attack the armored vehicle and allowing the latter to be able to retaliate in the more appropriate.

• les figures 1 et 2 représentent respectivement et schématiquement les projections dans un plan horizontal et dans un plan vertical de deux champs d'observation définis en avant de l'objet selon un premier mode de réalisation d'un système de mise en oeuvre du procédé de l'invention,
• la figure 3 illustre schématiquement dans un plan horizontal la trajectoire d'une menace qui traverse les deux champs d'observation tels que représentés aux figures 1 et 2,
• la figure 4 est une vue dans un plan vertical des champs d'observation selon un deuxième mode de réalisation, et
• les figures 5 et 6 représentent schématiquement les projections dans un plan vertical et dans un plan horizontal de deux champs d'observation définis autour de l'objet selon un troisième mode de réalisation.

Other advantages, characteristics and details of the invention will emerge more clearly on reading the additional description which will follow with reference to the appended drawings, given solely by way of example and in which:

• FIGS. 1 and 2 represent schematically respectively the projections in a horizontal plane and in a vertical plane of two fields of observation defined in front of the object according to a first embodiment of a system for implementing the method of the invention,
• FIG. 3 schematically illustrates in a horizontal plane the trajectory of a threat which crosses the two fields of observation as represented in FIGS. 1 and 2,
• FIG. 4 is a view in a vertical plane of the observation fields according to a second embodiment, and
• Figures 5 and 6 schematically represent the projections in a vertical plane and in a horizontal plane of two fields of observation defined around the object according to a third embodiment.

As mentioned in the preamble, a vehicle armored vehicle is likely to be attacked by a threat which can be fired from a short distance from this vehicle.

To be able to trigger an appropriate response against this threat the armored vehicle is equipped with a system who is able to detect the arrival of the threat, identify it as such, to precisely determine its trajectory and its speed and, if possible, identify it.

According to the invention, the arrival of a threat is detected by a process which consists in defining, from the armored vehicle and in front of an area thereof, fields of observation such that the threat must necessarily cross at at least two of these fields CH ₁ and CH ₂ before reaching said zone of the armored vehicle according to the embodiment illustrated in FIGS. 1 to 3.

Each bar associated with its optics defines an observation plane. As the two bars delimiting a field of observation are very close, they can be considered as spatially combined. Under these conditions, each observation field CH ₁ and CH ₂ is delimited by the two faces of a dihedral corresponding to the two observation planes and by the common edge materialized by the bars.

Each detector in the array will be able to react as soon as the threat crosses the observation plane of either bar.

The two photo-detector arrays associated with the two faces of a dihedral are placed at the level of the common edge of the dihedral, and the two pairs of photo-detector arrays are supported by the object, each located in a substantially plane vertical to the object and arranged so that the two observation fields CH ₁ and CH ₂ intercept each other.

The two observation fields CH ₁ and CH ₂ are schematically illustrated in projection in a horizontal plane H (FIG. 1) and in a vertical plane V (FIG. 2).

The two bars b ' ₁ and b ₁ of photo-detectors associated with the observation field CH ₁ are located at point B. The bar b' ₁ is associated with the face f ' ₁ of the dihedron, while the bar b ₁ is associated with the face f ₁ of the dihedral, these two faces f ' ₁ and f ₁ forming angles ' ₁ and  ₁ with respect to the horizontal axis AX (FIG. 1). In an analogous manner, the two arrays b ' ₂ and b ₂ of photo-detectors associated with the observation field CH ₂ are located at point A.

The two faces f ' ₁ and f ₁ of the observation field CH delimit between them an angle α1 in the vertical plane V (FIG. 2), while the two faces f' ₂ and f ₂ of the observation field CH ₂ delimit between them an angle α ₂ in this vertical plane V (Figure 2).

Either a threat M which was fired towards the armored vehicle. Suppose the threat has a trajectory in a direction D, this trajectory being comparable to a straight line. Indeed, we can admit that the speed of threat M is substantially constant over the time interval considered which may vary from only a few micro-seconds to a few milliseconds, and that in this time interval the vehicle, even in movement, can be considered to be fixed.

• un détecteur de la barrette b'₂ va détecter le point d'entrée de la menace M dans le champ d'observation CH₂, ce point d'entrée projeté dans un plan horizontal H donnant un point M'₂, et,
• un détecteur de la barrette b₂ va détecter le point de sortie de la menace M hors du champ d'observation, ce point de sortie projeté dans le plan horizontal H donnant un point M₂.

Suppose that threat M successively crosses the two fields of observation CH ₂ and CH ₁ . In this hypothesis illustrated in Figure 3 in the horizontal plane H (Figure 3):

• a detector of the bar b ′ ₂ will detect the entry point of the threat M into the observation field CH ₂ , this entry point projected into a horizontal plane H giving a point M ′ ₂ , and,
• a detector of the bar b ₂ will detect the exit point of the threat M outside the field of observation, this exit point projected in the horizontal plane H giving a point M ₂ .

In a similar way, one can define the entry points M ' ₁ and exit M ₁ of the threat M which then crosses the field of observation CH ₁ .

We will thus be able to calculate the times T ₂₂ , TR ₂ and T ₁₁ taken by the threat M to cross the field CH ₂ , to pass from the field CH ₂ to the field CH ₁ and to cross the field CH ₁ , respectively.

Knowing that the associated speeds V ₂₂ , V ₂₁ and V ₁₁ of threat M are the same, we can deduce the following two relationships: T 21 x M ' 2 M 2 = T 22 x M 2 M 1 (V 22 = V 21 ) T 11 x M ' 2 M 2 = T 22 x M ' 1 M 1 (V 22 = V 11 ).

These two relations will give rise to four equations according to the projections on the two axes of the horizontal plane H. In addition, the four points M ' ₂ , M ₂ ,, M' ₁ and M ₁ each belong to distinct lines of the horizontal plane H, which will provide four additional equations. There will therefore be eight equations with eight unknowns, the latter being the two coordinates of each of the points M ' ₂ , M ₂ , M' ₁ and M ₁ in the horizontal plane H.

We can thus calculate the speed of threat M in the horizontal plane H.

In addition, the coordinate along a vertical axis of each of the four points where the threat M crosses the fields of observation CH ₁ and CH ₂ , is deduced from the photo-detectors which have reacted and which are representative of the site of the threat M, knowing that the resolution of the site measurement will be equal to α / N or N represents the number of photo-detectors contained in a strip.

From these coordinates along the vertical axis, the coordinates of the points M ' ₂ , M ₂ , M' ₁ and M ₁ in the horizontal plane H and the measurement of times T ₂₂ , T ₂₁ and T ₁₁ , we can calculate the speed of threat M along the vertical axis.

The trajectory and speed in the threat space M are then known, and we can then trigger a responds from the vehicle. This response, consisting of a system for projecting offensive elements for example, is triggered after calculating an interception point and the right time for this trigger.

In general, it is also desirable to ability to identify type of threat M, in particular in the case of an arrow projectile.

From the signals delivered by the photo-detectors who were excited by the threat threat M we can deduce the length of this threat, but this is not sufficient to identify it precisely.

One means of identification is to be able to measure the threat M surface temperature which in the case of a arrow projectile, can reach several hundred degrees.

For this purpose, the two pairs of photo-detectors will be chosen to work in two length bands of different waves, which will allow us to go back to the true temperature of threat M, these two bands being of 3 to 5 µm for one and 3 to 12 µm for the other, for example.

Preferably, a compromise is chosen in the choice of these wavelength bands to be able to identify several types of threats.

Generally speaking, the corresponding angle or each field of observation of each dihedral face can be chosen to be as thin as possible to improve the detection accuracy. However, this finesse is not not essential because it is possible to base only on the beginning of detection by the faces of the dihedral to carry out the calculations described above. Concretely, the only condition to respect is that the energy emitted by the threat is greater than the energy perceived by the photo-detectors.

According to a second embodiment illustrated schematically in FIG. 4 in a vertical plane V, a field of observation CH _{3 is added,} starting from the roof of the vehicle for example, which is directed towards the ground and which intercepts the two fields of observation CH ₁ and CH ₂ .

In this case, the number of unknowns increases (M0 and M'0) but based as before on the principle that the speed of the ammunition is assumed to be constant, the system enriched with a sufficiently large number of equation so that the trajectory is perfectly identifiable in space (and no longer only in a plane projection).

With this embodiment, the measurement of the site of the crossing points of the observation fields CH ₁ and CH ₂ by the threat M becomes unnecessary. Thus, the number of photo-detectors per strip is no longer dictated by the desired resolution in a vertical plane but by obtaining a sufficient signal / noise ratio in the field observed.

According to a third embodiment illustrated diagrammatically in FIGS. 5 and 6, three fields of observation CH ₁ , CH ₂ and CH ₃ having conical shapes (which surround the vehicle) are used as shown in FIG. 5 and which, in a horizontal plane H, forming concentric circles C ' ₃ -C ₃ , C' ₂ -C ₂ and C ' ₁ -C ₁ which intercept each other.

In this example, at least the speed and the trajectory of the threat M are determined by detecting the order in which the fields CH ₁ , CH ₂ and CH ₃ are crossed, and the times measured between each crossing of the field. However, the resulting equations are non-linear and therefore less simple to solve than the previous embodiments.

In general, the photo detectors used are of the photovoltaic type for example, which deliver analog signals.

Claims (9)

1. A process to detect a threat fired at a fixed or mobile object, in particular a piece of ammunition with high penetrating capacities, at a short range from an armoured vehicle, process wherein it consists in:

   defining ahead of a zone of the object at least two fields of observation (CH₁, CH₂) such that the threat is obliged to pass through these two fields before attaining said zone of the object,

   detecting the points of entry and exit of the threat in each field of observation, and their coordinates with respect to a reference system,

   computing the time taken by the threat to pass through each field of observation to move from one field to another, and

   computing, using the coordinates of entry and exit as well as the time taken by the threat to pass through, at least the velocity and trajectory of the threat to allow the object to be able to trigger an appropriate counter response against the threat.
2. Detection process according to Claim 1, wherein it consists in firstly defining each field of observation (CH₁, CH₂) using photo detectors (b₁, b'₁, b₂, b'₂) arranged in lines in a substantially vertical plane (V) with respect to the object, and secondly in using an optic, to define two vertical planes forming a dihedron and delimiting each field of observation in the shape of an angular sector.
3. A process according to Claim 2, wherein it consists in defining each dihedral plane of a field of observation using a pair of arrays or matrices of photo detectors (b₁, b'₁, b₂, b'₂), these two pairs being located at a distance from one another so that the two fields of observation (CH₁, CH₂) intersect each other.
4. A process according to any one of Claims 1 to 3, wherein it consists in identifying the type of threat by calculating its length given, among other things, the time required for the threat to pass through at least one field of observation.
5. A detection process according to Claim 4, wherein it consists in measuring the surface temperature of the threat so as to more accurately identify it, in particular when the threat is an APFSDS type projectile.
6. A process according to Claim 5, wherein it consists in using photo detector arrays having different wave lengths.
7. A system to detect a threat fired at a fixed or mobile object for the implementation of the process such as defined by any one of the above Claims, wherein it comprises:

   photo detector (b₁, b'₁, b₂, b'₂) arrays or matrices associated with an optic device to define at least two fields of observation (CH₁, CH₂) ahead of a zone of the object, and

   analogical and digital processing means that are connected to said photo detectors to detect the threat passing through the two fields of observation from the analogical signals delivered by the photo detectors, and to calculate at least the velocity, the trajectory and the length of the threat.
8. A detection system according to Claim 7, wherein each field of observation (CH₁, CH₂) is defined from a pair of adjacent photo detector (b₁, b'₁, b₂, b'₂) arrays mounted in a substantially vertical plane with respect to the object
9. A detection system according to Claim 8, wherein the two pairs of photo detector arrays are carried by the object and located at a distance from one another.

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