EP0228925A1 - Automatic missile guidance system and missile provided with such a system - Google Patents

Abstract

- Multi-target guidance system for missile. - According to the invention, the system (2) is provided with an antenna with electronic bayalage; it classifies the targets in order of priority and directs the missile (1) by controlling the control surfaces (3) towards the highest priority target. During classification, the system (2) varies the direction of advance of said missile in order to keep said targets as long as possible in its field of action D.

Description

The present invention relates to a system for the automatic guidance of a missile, of the active electromagnetic seeker type. Although not exclusively, it is particularly suitable for air-sea or sea-sea missiles.

Active electromagnetic seeker devices are already known which allow the automatic guiding of a missile towards a target, in particular a marine target. These known seekers use two measurement channels exploiting signals from a mechanical scanning antenna, in order to deliver to the missile a deviation signal allowing it to control its trajectory towards a detected target. This phase of automatic tracking of the target is generally preceded by a search phase allowing the seeker to detect the echo (s) present in his research domain and possibly to make a quick choice of these echoes, depending on simple criteria, such as for example the amplitude or the width thereof. During this search phase, no guidance order is sent to the missile, so this phase must be short (in general, less than 1 second), which therefore does not allow a parallel and permanent analysis of all the echoes. present in the research area and therefore a fine classification of these echoes and potential targets.

Thus, the guidance of the missiles by known active electromagnetic seeker is done by enslavement of the missile on a given target. Once said missile is enslaved to said target, it can no longer be directed towards another target without there appearing the risk of missing, on the one hand, the target towards which the missile was first directed since it is purposely diverted to be directed to the last moment on another and, on the other hand, the last target indicated, because this one will have been designated too late by the seeker.

The object of the present invention is to improve the active seeker in order to allow them to finely analyze a field of targets, possibly including decoys and jammers, and to choose the most priority target.

To this end, according to the invention, the system for guiding a missile intended to hit a target chosen from several targets located in a geographic region where they can move, this system comprising observation means exploring a domain of action whose lateral limits are determined by the possibilities of exploration of said observation means and by the possibilities of maneuvering of said missile and whose limit in depth is at most equal to the maximum range of said observation means, as well as calculation means for processing the information delivered by said observation means, said missile being provided with directional controls controllable by said calculation means, is remarkable:
- in that said observation means are of the electronic scanning antenna type and successively and permanently explore the whole of a plurality of elementary zones fictitiously subdividing the part of said geographic region covered at each instant by said field of action ;
- in that said calculation means are associated with memory means in which the electronic images of potential targets are pre-recorded classified in decreasing order of priority;
- in that said calculation means determine the positions of the targets located at each instant in said field of action;
- in that said calculation means act on the direction commands of said missile to slide said field of action relative to said geographic region in order to delay the exit, outside the field of observation, of at least some of the targets reaching the lateral limits thereof;
- in that said calculating means continuously classify the targets located in said geographic region by comparing the electronic images thereof provided by said observation means with said prerecorded images; and
- in that said calculation means finally act on said direction commands to guide said missile towards the target of higher priority determined by said classification.

Thus, thanks to the high rate of scanning of an electronic antenna and the delay brought to the exit of the targets outside the field of observation, the system according to the present invention makes it possible to benefit from optimal time (despite the speed often missile level) to detect and classify targets by comparison with the recorded electronic images and to direct the missile towards the highest priority target.

Preferably, in order to lighten the calculation work as much as possible, prior to determining the trajectories followed by the targets, said calculation means perform a pre-classification of the targets in order of importance. This preclassification can for example be carried out by means of the amplitude of the echoes returned by said targets and it makes it possible to determine the positions only of the most important targets.

In order to establish only one microwave link between said antenna and the rest of the guidance system, it is advantageous that the latter comprises a microwave transmitter controlled by said calculation means and supplying said antenna via a circulator. , which, moreover, sends to said calculation means the signals received from said targets by said antenna. It is also advantageous for the exploration of said antenna to be controlled by said calculation means.

The electronic scanning antenna can be of the type described in patents FR-A-2 400 781, FR-A-2 494 870 and EP-A-0 039 702. It can be:
- either of the monoplane type,
- either of the monoplane type, but additionally comprising a mechanical device for decoupling the position of the antenna in site of the movements of the missile,
- or of the type with two planes making it possible to decouple electronically the beam of the movements of the missile in site.

Exploration by the antenna is preferably carried out according to a pseudo-random process, making it possible to overcome certain jammers.

For each antenna position, the system according to the invention emits a microwave signal (a narrow pulse for example) and then it digitizes the amplitude of the return signal after detection, and possibly integration. At this level, it is advantageous to precede the digitizing stage with a logarithmic amplifier, in order to reduce the number of bits required, taking into account the desired dynamics.

The system therefore continuously manufactures radar maps, by quantifying the amplitude of the signal received from each elementary area.

A digital processing, such as that described in the patents FR-A-2 402 971 and FR-A-2 494 870, then allows, scanning after scanning, to establish tracks characterized by their energy and corresponding to a maximum possible evolution targets from scan to scan.

In parallel, the signal received around the tracks thus created is used more finely: the autocorrelation functions of the amplitude responses obtained in successive elementary zones and compared according to mathematical laws are calculated with characteristic functions obtained by learning, in particular at either from real targets, or from measurements made on models and extrapolated, or even by methods based on a mathematical modeling of targets.

For this purpose, for example, with a radar having characteristics (frequency, resolution, distance etc.) identical or as close as possible to those of said missile observation means, impulse responses from real targets are recorded, possibly according to different presentations (in attitude) and said impulse responses are subsequently subjected to autocorrelation treatments comparable to those which will be carried out by the seeker. The results of this processing constitute the prerecorded electronic images.

To obtain these images, it is also possible to reconstitute said targets in the form of models on a reduced scale and measurements of the type mentioned above are carried out in an anechoid chamber with transposed frequency (in the reduction report of models).

A classification of targets and decoys, according to their probability of being the designated target, is thus carried out.

The type of continuous scanning carried out by the invention, associated with multi-target guidance, has many advantages compared to the seeker heads known to date, namely:
- the sensitivity of detection of echoes is better, because the antenna returns continuously in all directions of the research field, thus allowing a longer integration of the signals. This is particularly advantageous in the case of marine targets, since the fluctuation spectrum of the latter extends to very low values (a few tenths of Hertz);
- the parallel and continuous analysis and classification of all the echoes of the domain makes it possible to neglect none a priori, while having significant analysis time (which is useful given the fluctuation spectrum mentioned above ). This is particularly advantageous in the case of long-range shots, for which the errors in the designation of the objective on the one hand, and the inaccuracies of the inertial flight on the other hand, mean that the designated target can be located randomly. in the whole field of research displayed;
- facing jammers and their associated listening system, the fact that the lighting of the target is intermittent, can delay and even prevent the response of a jammer.

In addition, the fact of having at all times a maximum of analyzed and memorized information for the entire research field promotes the localization of the target chosen at the output of the interference sphere. This is particularly advantageous in the case where a jammer is triggered after the seeker is sent.

In addition, the present invention provides simplifications in the production of the seeker, namely:
- only one reception channel,
- removal of position detectors and mechanical antenna decoupling systems,
- removal of microwave rotating joints.

Preferably, at least as regards the highest priority potential targets, the prerecorded electronic images correspond to several different attitudes of said targets with respect to the missile. Thus, the guidance system according to the invention not only identifies the targets, but knows their relative angular position relative to the missile. Instead of guiding the missile towards the brightest point of the priority target, it can therefore direct the missile to a more vulnerable point of impact. This favorable point of impact can be chosen by an internal decision program of the guidance system according to the invention or by display before the firing of said missile.

For example, this point of impact is determined to be the barycenter of a plurality of bright points (not necessarily the brightest) of said target, the coefficients assigned to each of these being predetermined according to said attitude.

• La figure 1 est une vue en plan schématique illustrant le fonctionnement du système de guidage conforme à la présente invention.
• La figure 2 donne le schéma synoptique du système de guidage conforme à la présente invention.
• La figure 3 donne le schéma synoptique du calculateur pour le système de guidage conforme à la présente invention.
• La figure 4 illustre l'exploration du domaine d'action du missile par l'antenne à balayage électronique.

The figures of the appended drawing will make it clear how the invention can be implemented.

• Figure 1 is a schematic plan view illustrating the operation of the guidance system according to the present invention.
• Figure 2 gives the block diagram of the guidance system according to the present invention.
• Figure 3 gives the block diagram of the computer for the guidance system according to the present invention.
• FIG. 4 illustrates the exploration of the range of action of the missile by the electronic scanning antenna.

In Figure 1, there is shown very schematically a missile 1 intended to hit a target t _i (with i = 1,2,3, ...., n) chosen from several targets t₁, t₂, t₃, t₄ , t₅, ... being in a geographical area Z, in which they can possibly move.

The missile 1 is provided with a guidance system 2 and directional controls 3, for example aerodynamic fins, capable of being controlled by said guidance system 2 to act on the direction of advance F of said missile.

As will be seen below, the guidance system 2 comprises observation means, constituted by an antenna 4 with electronic scanning, and calculation means 5, intended for the processing of the information delivered by the antenna 4 and for monitoring steering controls 3.

The antenna 4 explores a portion of space limited, laterally, by two divergent lines L1 and L2 corresponding to the amplitude of exploration (scanning) A of said antenna. Since, moreover, said means for observing missile 1 have a maximum range depending on their own characteristics, it follows that the field of action D of said missile at a given instant is at most a sector delimited by lines L1 and L2 and by the portion of circle P centered on the instantaneous position of the missile and whose radius corresponds to said maximum range. However, due to its maneuverability limits, missile 1 cannot immediately reach the portions of lines L1 and L2 which are assigned to it. close, so that said field of action D is further amputated, just in front of said missile, of a zone d which is delimited by the lines L1 and L2 and by curves l1 and l2 and inside which it is not possible to drive the missile.

Thus, at a given instant in the flight of missile 1, the area of action D thereof consists of the portion of sector delimited by lines L1, L2, l1, l2 and P.

Of course, as the missile 1 advances, the lines L1, L2, l1 and l2 move with the missile, so that the geographical area on which the field of action is superimposed is constantly changing. In FIG. 1, it has been shown that in position (I) the action area D of missile 1 is sufficiently large to include the targets t1, t2, t3 and t4 (the target t5 having already left the area D), whereas for position II of said missile, the domain D has been limited to the point that only the target t3 remains inside of it, the targets t1 and t4 being released laterally through the lines L1 and L2 and the target t2 then being in the domain d .

It will be noted that the exit of said targets occurs systematically during the advance of missile 1, even in the case where said targets are fixed. When the targets are mobile and move in the zone Z, it goes without saying that their exit from the domain D can be advanced or delayed according to the trajectories which they follow.

The main object of the present invention is to guide the missile 1 so that the targets ti remain as long as possible within the field of action D, so that the guidance system 2 can benefit from the optimal time to perform the operations allowing it to classify said targets in order of importance, for at all times, leave only the target (s) which are not the most important (or priority) and leave guide finally missile 1 towards the most important target.

The embodiment, shown in FIG. 2, of the guidance system 2 according to the invention comprises an antenna 4 with electronic scanning transmitting and receiving the microwave signals intended to detect the targets ti, as well as a computer 5 and a transmitter 6 of said signals. The computer 5 controls the antenna 4 thanks to the link 7 and the transmitter 6 thanks to the link 8. The transmitter 6, working for example in X or Ku band, can be of the pulse transmitter type (magnetron) or of the pulse compression system. The signals it emits can be coherent or not.

The signals from the transmitter 6 are sent to the antenna 4 via a circulator-limiter 9 and a link 10. In the opposite direction, the signals received by the antenna 4 are sent by the latter. said circulator-limiter 9 through said link 10. There is thus a unique microwave link 10 between the antenna 4 and said circulator-limiter 9.

Furthermore, the guidance system 2 comprises a local oscillator 11 making it possible to transpose the microwave signals received by the antenna 4 into medium frequency signals, via a mixer 12. These medium frequency signals are transmitted to a receiver 13 which filters it, detects it and amplifies it. To this end, the receiver 13 may include an amplifier with automatic control gain. However, it is preferable that said amplifier is of the logarithmic type so that one can have a large instantaneous dynamic (greater than 70 dB).

The analog video signals from the receiver 13 are transmitted to an analog-digital converter 14, which transforms them into digital signals. Preferably, the converter 14 is fast (of the flash type with a sampling frequency greater than 20 MHz) and delivers a signal coded with at least six bits.

These digital signals are transmitted to a radar extractor 15, which stores them after having carried out a preprocessing (averaging, comparison with thresholds, etc.). This extractor 15 can be made up of a wired fast processing unit (adders, comparators, logic gates, etc.) and a dynamic memory with fast access.

The computer 5 manages the entire system and uses the data stored by the extractor 15, with which it is connected by the bus 16, in order to carry out the tracking and classification operations in accordance with the invention . This results in orders transmitted to the missile 1 and in particular to the direction commands 3 via a digital bus 17 and commands intended for the electronic scanning antenna 4 (via the link 7). The computer 5 also ensures via the bus 16 the dialogue with the missile during the initialization phase of the seeker. It can also control the operation of the transmitter (time of transmission), control of the type of transmission, etc.), via link 8.

In the embodiment shown in FIG. 3, the computer 5 comprises a central unit 18, for example constituted by a 16 or 32-bit management microprocessor, which, via a bus line 19 is connected to :
a memory 20, for example read only, containing the software and prerecorded electronic images of potential targets;
- A working memory 21, for example RAM, for the temporary storage of data;
- a rapid arithmetic and logic unit 22;
- an interface circuit 23 for the bus 17;
- an input-output circuit 24 for links 7 and 8 internal to system 2; and
an interface circuit 25 with the extractor bus 16 connecting the computer 5 to the extractor 15.

As shown in FIG. 4, at a given instant, the computer 5 controls the antenna 4 so that it explores an elementary sector sj of the action domain D, chosen from a plurality p of adjacent elementary sectors s1 to sp ( with j = 1,2,3, ... p) covering all of said action domain D. Preferably, in order to avoid as much as possible the interference of the exploration of the antenna 4, the scanning of the domain action D is not done in the order of sectors from s1 to sp, but in a random fashion.

Furthermore, the computer 4 fictitiously subdivides each elementary sector sj, along the radius thereof, into a plurality q of adjacent elementary zones zj1 to zjq covering the whole of said sector sj.

Thus, the action domain D is fictitiously subdivided into a plurality pxq of elementary zones zjk (with k = 1,2,3, ..., q) explored successively, according to sequences imposed by the computer 5, by said antenna 4 .

The antenna 4, controlled by the computer 5 by the link 7 and supplied by the transmitter 6 by the link 10, receives in return the echo of the targets ti and, by the chain 9,10,12,13,14, 15 and 16, this echo is addressed to the computer 5, which thus knows in which elementary zone zjk is located each target ti.

Of course, it is essential that at all times the computer 5 modifies the indices j and k of the elementary zones zjk to take account of the advance (arrow F) and any change of direction of said missile 1.

The continual updating of the indices j and k as a function of the advance of the missile is automatically taken into account by the computer 5. In addition, since the changes in direction of the missile are imposed on it by the system 2 (by l 'intermediary of the link 17 and the direction commands 3) the computer 5 knows them and can continuously modify, in an appropriate manner, said indices j and k as a function of said changes of direction.

Thus, at all times the computer 5 knows precisely the position of each target ti in its field of action D.

At this stage of the exploration, the computer 5 can make a preselection of the targets ti and, for the rest of the process, be interested for example only in targets whose amplitude of the echo exceeds a predetermined threshold, c that is to say to the biggest targets. Thus, in FIG. 1 for example, it has been assumed that in position (I) the guidance system 2 has voluntarily allowed the target t5 to leave its area of action D (through the line L2), because the amplitude of the echo of this target t5, determined for a position of missile 1 prior to position (I) (and not shown), was found to be lower than said predetermined threshold.

Since the computer 5 knows the position of each target ti at all times, it can follow the movements of said targets under the action of their own propulsion means. In fact, from one scan to the next carried out by the antenna 4, a moving target ti will pass from an elementary zone zjk to an elementary zone adjacent to or adjacent to it.

The computer 5 therefore follows, within its field of action 5, the displacement of the targets ti, as a function of its own advance and of its own changes of direction. It therefore knows, at all times, those of the targets ti which are about to leave its field of action D through the lines L1, L2, l1 and l2.

Simultaneously with the position determination operations described above, the computer 5 engages in classification operations of said targets ti. For this, it compares the echoes received by the antenna 4, that is to say the electronic images of said targets, with electronic images of potential targets recorded in the memory 20. These prerecorded images are classified in decreasing order of priority. .

Thus, at each instant, the computer 5 not only knows the position of each target ti, but determines an order of priority in the destruction of said targets.

As a result, the computer 5 knows whether or not it can leave a target outside its area of action. For example, in FIG. 1, the position (II) of missile 1 corresponds to the fact that, in position (I), the guidance system 2 has determined, in addition to the positions of the targets t1, t2, t3, and t4, a order of priority according to which the target t3 has the highest priority. By moving from position (I) to position (II), system 2 allowed the targets t1, t2 and t4 to exit the area of action D.

On the other hand, position (III) in FIG. 1 illustrates the situation in which, in position (I) of the missile, system 2 has determined that the target with the highest priority is the target t4. Under these conditions, the system 2 modified the direction of advance of the missile 1 so that this target t4 remains in the field of action D thereof.

This position (III) of missile 1 also illustrates the case where, the computer 5 having already eliminated of its choice the targets t1 and t2 having the lowest priority, however has not yet definitively chosen between the targets t3 and t4. Consequently, the guidance system 2 communicated to the missile 1 a change of direction making it possible to maintain, at the same time, and for as long as possible, the targets t3 and t4 in the field of action D, in order to benefit the computer. 5 of an optimal time to make its final choice.

When the most priority target is definitively determined, the guidance system according to the invention goes into its final tracking phase, with for example a frequency of exploration by the antenna 4 greater than in the guidance phase .

In the favorable case where, by comparing the electronic images of the highest priority target with the prerecorded electronic images, it is possible to determine the attitude of this target relative to the missile, we can choose a different point of impact from the brightest point of the target, for example according to criteria such as those mentioned above.

Claims (9)

1 - System for guiding a missile (1) intended to reach a target chosen from several targets (t1 to t5) located in a geographic region (Z) where they can move, this system (2) comprising means observation (4) exploring a field of action (D) whose lateral limits are determined by the possibilities of exploration of said observation means and by the possibilities of maneuvers of said missile and whose limit in depth is at most equal at the maximum range of said observation means, as well as calculation means (5) for processing the information delivered by said observation means, said missile being provided with directional controls (3) controllable by said calculation means, characterized:
- in that said observation means (4) are of the electronic scanning antenna type and successively and permanently explore the whole of a plurality of elementary areas (zjk) fictitiously subdividing the part of said geographic region covered at each instant by said field of action;
- in that said calculating means (5) are associated with memory means (20) in which are pre-recorded the electronic images of potential targets classified in decreasing order of priority;
- in that said calculation means (5) determine the positions of the targets located at each instant in said field of action;
- in that said calculation means (5) act on the direction commands (3) of said missile to slide said field of action relative to said geographic region in order to delay the exit, outside the field of observation, of at least some of the targets reaching its lateral limits;
- in that said calculating means continuously classify the targets located in said geographic region by comparing the electronic images thereof provided by said observation means (4) with said prerecorded images; and
- in that said calculation means (5) finally act on said direction commands (3) to guide said missile towards the target of higher priority determined by said classification. 2 - System according to claim 1,
characterized in that, prior to the determination of the trajectories followed by the targets, said calculation means carry out a pre-classification of the targets in order of importance. 3 - System according to one of claims 1 or 2,
characterized in that it comprises a microwave transmitter (6) controlled by said calculation means (5) and supplying said antenna (4) via a circulator (9), which, moreover, addresses to said means of calculating (5) the signals received from said targets by said antenna. 4 - System according to one of claims 1 to 3,
characterized in that the exploration of said antenna (4) is controlled by said calculation means (5). 5 - System according to claim 4,
characterized in that the exploration of said antenna is controlled in a pseudo-random manner. 6 - System according to one of claims 1 to 4,
characterized in that, at least for the highest priority potential targets, the prerecorded electronic images correspond to several different attitudes of said targets with respect to the missile. 7 - System according to claim 6,
characterized in that the final point of impact of the missile on the priority target is chosen different from the brightest point of the latter by said system. 8 - System according to claim 7,
characterized in that the final point of impact of the missile on the priority target is defined as the barycenter of a plurality of bright points of said target, the coefficients assigned to each of these bright points being predetermined according to said attitude. 9 - Missile,
characterized in that it comprises a guidance system of the type specified under any one of claims 1 to 8.

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