DE4008341A1 - System for guiding projectiles by means of a directional beam coded in polar coordinates - Google Patents

Abstract

In a control system for projectiles, a directional beam is used, which is coded in polar coordinates. The firing station (1) comprises: - means for tracking a target (2) and defining a sighting line (LV); - means for scanning a guide cone (5), the axis of symmetry (AS) of the line of sight (LV) is readjusted by means of a laser beam (3), said cone consists of elementary cells, which are successively illuminated by the beam (3), the deflected by an acousto-optic deflector in a plane passing through the axis of symmetry (AS), further comprising an opto-mechanical circular scanning device which rotates this plane; - means for modulating the beam (3) with a binary sequence representing the polar coordinates (Thetarho) of the illuminated cell; while the projectile (4) comprises: - means for receiving the laser beam (3), demodulating it and decoding the polar coordinates; - means for determining a trajectory correction, whereby the projectile approaches the axis of symmetry (AS) of the traffic cone.

Description

The The invention relates to a steering system for projectiles, by means of working in polar coordinates coded beam works. projectiles may be missiles or grenades that come with a device for correcting the trajectory are provided.

The Steering by means of a directional beam is a method by which Any number of projectiles are guided very precisely to a target without determining the position of each projectile would have to be determined simply by a sight line becomes, which runs through the position to be reached, at It is either the current target position or a future one Position determined based on characteristics of its trajectory become. Means for tracking the target determine this line of sight.

From the launcher goes an infrared laser beam out, which illuminates a part of the room, as a traffic cone referred to as. The position of the symmetry axis of the traffic cone is the sighting line readjusted. The traffic cone consists of elementary Cells individually identified by a coding method. The projectile includes means for receiving the directional beam and to determine in which cell the projectile is located. Computers determined a correction of the trajectory of the projectile, in such a way that it adjoins the symmetry axis of the guide cone approaches. This correction is done by a tail unit or Gas nozzles.

One System for steering by means of a directional beam has a high steering precision and a very good security regarding countermeasures on, because the means for receiving the beam, which is itself is generally a lens and an optical detector, are in the direction of the launcher and not in the direction of the target.

Two main types of systems for steering by means of a directional beam are known. In a system of the first type which employs "space coding", means are provided for emitting a laser beam which simultaneously illuminates all of the elementary cells of the beacon, each cell being identified by locally modulating the amplitude of the laser beam for each cell different binary codes. The projectile determines which cell it is in by detecting the binary code that modulates that part of the beam the projectile is receiving. Such a system is in Optical Command and Beamrider Missile Guidance, RL Sitton, SPIE. Vol. 317, pp. 358-364 ,

a such system has the defect that a laser beam of relatively high power must be sent out at the same time to illuminate all the cells of the traffic cone, with a given range must be achieved. Approximately present room as well as the flame and smoke of the projectile, if it is a missile acts to dampen the laser beam between the Launcher and the reception facilities for this beam to a great extent. For a given range To achieve it is therefore necessary to emit a laser beam, whose spatial energy density is sufficiently high to to compensate for this damping.

In a second-type control system, a "temporal coding" or "sampling" is performed. The firing station transmits a laser beam which scans a traffic cone by successively illuminating all unit cells. Such a system is in Michael Higgins, Gerald Titmuss, John Evans, Richard Martyn, British Aerospace UK "An improved acousto-optic laser scanner guidance system described. In this system, the firing station includes a CW laser and means to scan the traffic cone along a group of horizontal lines, then along a group of vertical lines, each line being traversed twice before the subsequent one is scanned. For example, each horizontal line is scanned from left to right and then from right to left so that the projectile receives the laser beam twice during the horizontal scanning period of the entire traffic cone. The time interval between the two reception time points makes it possible to determine the position of the projectile with respect to a horizontal axis.

The Projectile also receives twice the laser beam during the vertical scanning period of the entirety of the traffic cone. A measurement of the time interval between these two reception times allows the determination of the position of the projectile in with respect to a vertical axis. Every elementary cell is on the Cut a vertical scan line with a horizontal scan line centered. The width and the length of each cell are like this designed so that the diameter of the laser beam is a cell completely covered and slightly over the neighboring cells overlap.

One Such a system allows the full performance of the Laser bundle on an elementary cell at a given Time to concentrate. This concentration of total energy of the laser beam to a single cell a significant improvement in the signal-to-noise ratio, so that the power of the laser for a given Range can be reduced.

• – eine weitere Verminderung der Leistung des Lasers für eine gegebene Reichweite;
• – eine Steigerung der Leitpräzision;
• – die Übertragung von Nachrichten zu dem Flugkörper, z. B. von Informationen über die Evolution der Flugbahn des Ziels;
• – eine Integration der Zielverfolgungsmittel mit den Einrichtungen zur Abtastung des Leitkegels mittels eines Laserstrahls.

The invention has for its object to propose a control system that allows the following:

• A further reduction in the power of the laser for a given range;
• - an increase of the guiding precision;
• - The transmission of messages to the missile, z. For example, information about the evolution of the trajectory of the target;
• - An integration of the target tracking means with the means for scanning the traffic cone by means of a laser beam.

object The invention is a system which is essentially an optoacoustic Deflector for deflecting a laser beam in a plane, which passes through the symmetry axis of the traffic cone to but also to modulate the amplitude of this beam and send a message to transfer to the projectile; furthermore an optomechanical Device for controlling the plane containing the laser beam about the axis of symmetry of the laser beam To twist traffic cones.

According to one further feature, the system comprises a common optical Way for the target tracking agents and for the Scanning of the traffic cone.

According to one further feature, the system comprises means for modulating of the laser beam with a binary sequence intended for each cell is different, this sequence being the polar coordinates represents the cell in a plane perpendicular to the axis of symmetry of the traffic cone.

• – Mittel zur Verfolgung eines Ziels und Bildung einer Visierlinie;
• – Mittel zum Abtasten eines als Leitkegel bezeichneten Raumteiles mittels eines Laserstrahls, wobei dieser Leitkegel eine Symmetrieachse aufweist, deren Lage der Visierlinie nachgeregelt wird, wobei ferner dieser Leitkegel aus elementaren Zellen besteht, die durch den Strahl nacheinander beleuchtet werden;

wobei das Projektil aufweist:

• – Mittel zum Empfangen des Laserstrahls; Mittel, um zu bestimmen, in welcher Zelle sich das Projektil befindet; und Mittel, um daraus eine Korrektur der Flugbahn des Projektils abzuleiten, in solcher Weise, daß es sich an die Symmetrieachse des Leitkegels annähert;
• – Mittel zum Durchführen dieser Flugbahn-Korrektur;

das System ist erfindungsgemäß dadurch gekennzeichnet, daß die Abtastmittel umfassen:

• – Mittel zur Ablenkung des Laserstrahls in einer Ebene, welche durch die Symmetrieachse des Leitkegels verläuft;
• – Mittel zur Ablenkung dieses Laserstrahls, indem diese Achse um die Symmetrieachse des Leitkegels verdreht wird;
• – Mittel zum Modulieren des Laserstrahls mit einer binären Sequenz, die für jede Zelle verschieden ist;

und daß die Mittel zum Empfangen des Laserstrahls Mittel aufweisen, um diese strahlzudemodulieren und die Binärsequenz decodieren.The projectile guidance system according to the invention by means of a directional beam coded in polar coordinates comprises a firing station which comprises:

• - means of tracking a target and forming a sighting line;
• - means for scanning a designated as a traffic cone part of space by means of a laser beam, said traffic cone has an axis of symmetry, the position of the line of sight is readjusted, further wherein this traffic cone consists of elementary cells, which are illuminated by the beam successively;

wherein the projectile comprises:

• - means for receiving the laser beam; Means for determining in which cell the projectile is located; and means for deriving therefrom a correction of the trajectory of the projectile such that it approximates the axis of symmetry of the pilot cone;
• - means for performing this trajectory correction;

the system according to the invention is characterized in that the scanning means comprise:

• - means for deflecting the laser beam in a plane passing through the axis of symmetry of the guide cone;
• - means for deflecting this laser beam by rotating this axis about the axis of symmetry of the pilot cone;
• - means for modulating the laser beam with a binary sequence that is different for each cell;

and in that the means for receiving the laser beam comprises means for beam modulating and decoding the binary sequence.

Further Features and advantages of the invention will become apparent from the following Description and from the drawing, to which reference is made. In the drawing show:

1 schematically a firing station, the projectile, the target and the traffic cone;

2 schematically the section of the traffic cone with a plane which is perpendicular to its axis of symmetry;

3 a timing chart showing the coding of the laser beam for a cell of the traffic cone;

4 a schematic diagram of a first embodiment of the system according to the invention;

5 schematically a part of this first embodiment;

6 . 7 and 8th the operation of this first embodiment; and

9 a schematic diagram of a second embodiment of the system.

According to 1 creates the firing station 1 a traffic cone 5 for steering a missile 4 on a goal 2 , This traffic cone 5 has the axis of symmetry AS, whose position is readjusted to a line of sight LV, extending from the firing station 1 to the goal 2 extends. This sighting line is defined by tracking means used in the launching station 1 are included. At a given time the firing station sends 1 a laser beam 3 , which is an elementary cell of the traffic cone 5 illuminated. This elementary cell is cylindrical or of the shape of a cone with a small opening.

To denote each elementary cell of the traffic cone, the section of the traffic cone is viewed with a plane x o, which is perpendicular to the axis of symmetry AS and of the missile 4 is traversed at the time considered. The section of the traffic cone with the xoy plane is a surface 7 , which is approximately circular, and the elementary cell, which at the time considered by the laser beam 3 is illuminated, forms with the plane xoy a cut, of a circular surface 6 equivalent. The location of this surface 6 is defined with respect to the axes ox and oy, which are perpendicular to each other and intersect each other at the point o which lies on the axis of symmetry AS. The axis ox is horizontal, while the axis oy is contained in a vertical plane. The center of the surface 6 is located at the distance ρ from the point o, and the vector radius, which is the center of the surface 6 with the point o forms an angle θ with respect to the axis ox. The one cell whose cut is the surface 6 is in the frame of reference xoy denoted by the polar coordinates ρ, θ.

In practice, the plane xoy and the corresponding frame of reference move by the missile 4 consequences. In order for the given cell to maintain the same coordinate value, the unit of distance to be used with respect to the axis of symmetry AS must be a unit that varies as the missile moves 4 from the firing station 1 away. For example, this unit is equal to 1/16 of the radius of the cut surface 7 of the traffic cone 5 with the plane xoy.

The 2 explains the operation of the system and shows the location of the elementary cells, one after the other in the traffic cone 5 be illuminated. These cells are each represented by their intersection with the xoy plane. The scanning is performed successively on 16 radii evenly distributed around the point o, which forms a center of symmetry for the scan. For example, on the radius oA, there is the scan therein, successively a cell with the cut surface 10 and then a cell with the cut surface 11 , then a cell with the cut surface 12 etc. to illuminate. These cells have no sharp boundaries in practice, but partially overlap each other. Furthermore, the other radii are scanned in succession, in the same way as for the radius oA.

at In the example shown, the elemental cells are regular distributed from the middle to the periphery, which has the consequence that the close to each other at the center o lying cells strongly overlap, while the peripheral cells cover each other little.

A A special feature of the scanning of the traffic cone is that each Radius oA virtually simultaneously with the diametrically opposite Radius oA 'is scanned. This peculiarity arises from the Coding method, which is used to each cell of the traffic cone to identify by the laser beam is modulated. This Coding is essentially a binary To send out a sequence that is different for each cell, and a complementary binary sequence for to send out that cell, with respect to the axis of symmetry AS is symmetrical.

at A practical embodiment becomes a CW laser used. Each bit of the binary sequence is transmitted by modulating the amplitude of the laser beam.

Various conventional modulation techniques can be used. A modulation which consists in illuminating for the value 1 and no illumination for the value 0 of the binary sequence would be disadvantageous in that no mean of zero magnitude would result. A better modulation technique is to represent, for example, each bit of the sequence by two elementary information whose duration is equal to half a bit period. For example, each bit of value 1 is transmitted in the form of illumination during a half-bit period, followed by a lighting pause during a half bit period; conversely, for each bit of value 0. This modulation technique also makes it possible to perform error detection because every bit transmitted has a transition. A missing bit can therefore be detected by counting the transitions.

The implementation of such 100% amplitude modulation is to direct the laser beam to a given cell 9 divert to transmit elemental information; further therein, the laser beam to a cell 9 ' to deflect, which is symmetric to the given cell, to transmit opposite elementary information. The binary sequence passing through the laser beam to the given source 9 is thus complementary to the binary sequence, which during the same time interval to the symmetrical cell 9 ' is transmitted.

These particular form of 100% modulation of the laser beam is special effective, because the laser beam is transmitted without interruption. These Efficiency comes to the effect of the concentration of the laser beam on a single cell and allows for a strong Reduction of average laser power over one Performance in a system that uses spatial coding is working.

When preferred embodiments are two coding methods proposed to identify each cell of the traffic cone ren The first coding method comprises each binary sequence a first and a second binary word representing the coordinates θ and ρ of the Play cell in the xoy system. Each cell is transmitted through two Coordinates are completely marked so that the cells with a non-uniform pitch step on each radius can be distributed, but the symmetry with respect is maintained on the axis of symmetry of the cone. This non-uniform Distribution allows a large number of To bring cells into abolition, each other in the central zone of the traffic cone. If the overlapping ones Cells are numerous, they have an oversampling to Sequence, reducing the transmitted energy in the middle of the traffic cone unnecessarily concentrated. On the other hand, can by a Enlargement of the division step of the center closer cells the number of cells and thus the Be reduced for the entire traffic cone, so that the missile its position with higher frequency can determine.

It However, there are still partial overlaps, the one significant advantage over the method of a spatial Coding according to the prior art. The means of receiving the laser beam, which are in the missile, can almost always at any time Coordinates of two or three cells can and receive calculate interpolated coordinates, taking into account the respective received amplitudes for each of the received binary sequences. Through this interpolation, the position determination of the missile refined and thus the steering precision be increased.

At the in 2 In the example shown, the 16 radii are marked by 16 angle values θ which vary from 0 to 180 ° and from 0 to -180 ° and are encoded by a 3 bit binary word and a sign bit. The correspondence is given in the tables below. The binary words representing θ and 180 ° + θ corresponding to two diametrically opposite radii are chosen in such a way that the corresponding bits are complementary.

For example, in 2 two symmetrical cells passing through the surfaces 9 and 9 ' are shown, the coordinates θ = 123.75 ° and θ = -56.25 °. They are coded in the following way:
1 101 = .5 and 0 010 = -2 Coding of θ in the upper half space Value in degrees Code value 11.25 ° +0 33.75 ° +1 56.25 ° +2 78.75 ° +3 101.25 ° +4 123.75 ° +5 146.25 ° +6 168.75 ° +7 Coding of θ in the lower half space Value in degrees Code value -11.25 ° -0 -33.75 ° -1 -56.25 ° -2 -78.75 ° -3 -101.25 ° -4 -123.75 ° -5 -146.25 ° -6 -168.75 ° -7

3 illustrates the coding method used to encode the coordinates of the cells 9 and 9 ' is used by means of a binary sequence S and the complementary sequence. This sequence S starts with two bits, the upper / lower discrimination bits being the distinction of a cell belonging to the upper half space, like the cell 9 , from a symmetrical cell, the lower hemisphere 1 listened to, like the cell 9 ' , enable. The two up / down discrimination bits consist of a so-called reference bit, which always has the same value 1, and a so-called sign bit, which represents the sign of the angle value θ. The sequence S then contains three bits which encode the absolute value of the angle θ. The sequence S then contains three bits representing the value ρ on a scale of 0 to 7.

One bit of the sequence S with the value 0 is transmitted by the cell 9 ' illuminated during a half-period and the cell 9 illuminated during the following half-period. Conversely, a bit of value 1 is transmitted by the cell 9 during half a period and the cell 9 ' illuminated during the following half-period.

For example, if this laser operates continuously, the illumination of the cell will stop 9 by deflecting the beam very quickly and on the cell 9 ' is stopped. Conversely, the completion of the illumination of the cell 9 ' in that the beam very quickly to the cell 9 is deflected and stopped there. The circular scan, which varies the angle θ, can be continuous because the duration of each frequency S is very small compared to the duration for a circular deflection movement from one value θ to the next.

The decoding of the modulation of the laser beam received by the missile takes place by means of a decoder on board the missile. This decoder begins by reproducing a binary sequence T in which one bit is equal to 1 when the decoder detects illumination for a period of time equal to one-half bit period and then missing illumination during a duration also equal to one Half-period is. One bit of the sequence T has the value 0 if the decoder uses the Absence of illumination during a period equal to half a period, followed by illumination for a period equal to half a period. Subsequently, the sequence T is decoded to discriminate between the upper half space and the lower half space, and to reproduce a value θ and a value ρ. When the missile is in the upper half-space, the reception of the directional beam begins with illumination for a duration equal to one bit period. When the missile is in the lower half-space, the reception of the directional beam begins with illumination for half a bit period, followed by the lack of illumination for a duration equal to one bit period. The length of the first signal rectangle of the sequence T thus forms the distinguishing criterion for upper or lower half space. Then only the values θ and ρ have to be decoded.

For example, if the missile is in the cell 9 demodulation of the laser beam received by the missile results in the following binary sequence:
T (9): 0 1 1 0 1 1 0 0

The first two bits 0, 1 mean that the missile is in the upper half-space. The second, third, fourth and fifth bits directly give the encoded value θ:
θ = 1 101 = +5 corresponding to a value of + 123.75 °.

The Sixth, seventh and eighth bits result directly in the value ρ = 4th

When the missile is in the cell 9 ' demodulation of the laser beam received by the missile results in the following binary sequence:
T (9 '): 1 0 0 1 0 0 1 1

The first two bits 1 and 0 mean that the missile is in the lower half-space. The second, third, fourth and fifth bits directly give the coded value of θ:
θ = 0 0 1 0 = -2 corresponding to -56.25 °.

The sixth, seventh and eighth bits yield the value of ρ which is complementary to 1. Complementation then returns the value:
ρ = 1 0 0 = 4.

The Sequence S can also be an additional binary Word containing a message. This message can an information about the evolution of the trajectory of the target be to allow the word calculator of the missile to produce improved corrections of its trajectory. These news may also contain information about a possible instruction error be the symmetry axis of the traffic cone, so the word calculator a such correction of trajectory can calculate that the missile approximates to an axis that in is offset with respect to the axis of symmetry of the traffic cone.

After all This message can activate one of the missile trigger entrained proximity rocket.

If the missile is in the upper half-space supplies the binary obtained by demodulation of the laser beam Sequence directly the bits of the message. If the missile is located in the lower half space, the decoder complements the obtained by demodulation of the laser beam binary sequence, to reconstruct the exact value of the message bits.

If The message is long, it can be in several binary words be divided, each with an identification prefix are provided and transmitted in the course of several consecutive sampling periods become.

to Acceleration of the scanning of the traffic cone makes it possible the scans with sole transmission alternate from coordinates with scans, in which only one message is transmitted, so that one Messaging is only assigned time if a message should actually be transmitted. The messages are then sent by coordinates through an additional Differentiated bit.

A second encoding method is to transmit a binary sequence representing only the angular position θ. The type of scanning then differs from that previously described, since each Ra is traversed twice by a back and forth movement of the laser beam before moving on to the next radius. The speed of the scan is constant so that the cells have a constant pitch step along the radii, but it may be different for trace and retrace. The missile is provided with a decoder which detects two passes of the laser beam during each period of scanning the entire traffic cone. From the knowledge of the scan rate for each radius, the decoder derives the value of the distance from the axis of symmetry AS by forming the ratio between the duration of the time interval between two passes and the duration of two scans for a radius.

to Distinction between trace and rewind need binary sequences are sent out whose composition different for trace and retrace is. For example, the binary sequence may consist of two distinguishing bits for up / down and three bits for the absolute value of θ during the trace, while for the return of two distinguishing bits for top / bottom and a 6 bit word for messages consists. Due to the length of the sequences can be between Hinlauf and return are distinguished. In this example The sequence contains five bits for the Trace and eight bits for the return.

A Variant of this second coding method is while of trace two discrimination bits for up / down and three bits for the absolute value of θ and six To transfer message bits. During the return The laser beam is faster than during the trace distracted, each cell during half a lifetime Bit period is illuminated. This variant can gain time to shorten the sampling period.

A Variant for the first and for the second encoding method is to use instead of a continuous wave laser to use a pulse laser whose cadence is higher as the bit frequency; Further, a receiving device is then used which is designed for the laser pulses. The laser pulses then form a subcarrier, passing through the binary Sequence is digitally modulated, in a manner analogous to a continuously transmitting laser. This results in an improvement the signal-to-noise ratio for the same average power of the laser. Furthermore, there is a lower Sensitivity to disturbances caused by Flames and smoke caused by the propulsion of the missile out.

Another variant is to use a CW laser and chop the laser beam with a cadence much higher than the bit frequency of the sequence to be transmitted. The encoder 31 must then have logic means to provide a logic signal which is the product of the sequence to be transmitted and a chopping signal, which then replaces the previously described binary sequence for controlling the jumps of the laser beam.

Another variant is to use a pulse laser whose cadence is twice the bit frequency, then means are provided to synchronize the laser frequency with the bit frequency. The modulation of the beam is to send two pulses for each bit, regardless of their value. One bit with the value 1 to the cell 9 For example, the first pulse to the cell becomes 9 deflected while the second pulse to the symmetrical cell 9 ' is distracted. Conversely, one bit from value 0 to cell 9 to send, the first impulse to the cell 9 ' redirected while the second pulse to the cell 9 is steered.

If A pulsed laser is used, the two deflections and the laser is synchronized with each other.

The 4 shows a schematic diagram of a first embodiment of the system according to the invention. This embodiment comprises means for scanning the traffic cone, namely a laser 33 , two deflecting mirrors 34 . 35 , an afocal optical adapter 36 , An acousto-optic deflector 37 , an afocal zoom unit 38 , a circular scanning device 40 and control means 39 , Further, it comprises tracking means consisting of: the circular scanning device 40 , an optical device 41 , a cooled detector line 42 , a tracking calculator 43 , a directive device 44 and a dichroic plate 45 , Further, means are provided for automatically aligning the sighting lines: a shutter 46 , a damping plate 47 , a cube corner 48 , a device 49 for controlling the harmonization of the sighting lines and a position tracking device 50 ,

It should be noted that the plate 45 used both by the tracking devices and by the means for harmonizing the sighting lines. Further, the tracking means and the means include for scanning the traffic cone, a common optical path through the directional device 44 and the circular scanning device 40 is formed. This integration of the tracking means, the guide cone deflection means and the sight line harmonization means allows a simple and compact implementation.

The laser 33 is a CO ₂ laser that operates continuously at the wavelength of 10.6 μm and with linear polarization. The deflection mirror 34 . 35 have the task to reduce the space requirement of the entire device. They direct the laser 33 outgoing beam to the entrance of the device 36 which adapts the diameter and divergence of the laser beam to values suitable for the subsequent optical elements. The acousto-optic deflector 37 deflects the laser beam within a plane that is vertically oriented, for example.

The location of the mirror 35 is by means of a position-Nachregelvorrichtung 50 adjustable to displace the laser beam in a plane which is horizontal in this example. The device 50 receives at a control input a correction signal which is an output of the device 49 supplies.

The acousto-optic deflector 37 consists of a Bragg cell of conventional design. This deflects the laser beam quickly. The device comprises a germanium crystal traversed by mechanical waves which generates a piezoelectric transducer which is excited by a high frequency generator. This generator is conventional.

The distractor 37 receives at a input a desired voltage, which from a first output of the control means 40 is supplied and defines the deflection angle φ. That the distractor 37 leaving bundles then traverses the afocal zoom 38 which makes it possible to adjust the divergence of the laser beam and the magnitude of its deflection, depending on the distance between the firing station and the missile. The use of this zoom 38 will be explained below. The zoom 38 comprises a conventional control arrangement, which is controlled by a setpoint voltage, which is a second output of the control means 39 supplies. This voltage represents a magnification value G that depends on the distance the missile has traveled since its launch.

The dichroic plate 45 is transmissive for wavelengths greater than 10 μm and reflective for wavelengths less than 10 μm. The zoom 38 leaving laser beam passes through the dichroic plate 45 with a low attenuation based on the reflection of a small fraction of the energy of the beam. Subsequently, a deflection by the Kreisabtasteinrichtung 40 showing the plane containing the beam in the course of the deflection by the deflector 37 twisted. When in the device 40 entering beam forms a non-vanishing angle with its optical axis, which shifts through the device 40 caused circular scanning of the beam on the surface of a cone whose axis of symmetry is the axis of symmetry AS of the cone.

The device 40 is provided with a control input connected to a third output of the control means 39 is connected to receive a setpoint voltage representing the value of the angle θ. An embodiment of the device 40 will be described below. The out of the device 39 exiting beam then traverses the directive device 44 , which is a conventional opto-mechanical device provided by the tracking computation circuit 43 is controlled in such a way that the sight line of the device 44 is constantly directed to the target or a future position, that of the device 43 is predicted. An output of the device 44 thus gives a laser beam 3 whose middle direction is the line of sight, which passes through the computing device 43 is set, and which moves around this central direction so that the traffic cone is scanned, with deflecting movements by the deflector 37 and the device 40 be abandoned.

The tracking is done by detecting the infrared radiation of the target. This radiation is in a bundle 29 receive the devices 44 and 40 traversed and almost completely through the dichroic plate 45 on the optical device 41 is reflected, which is an image on the detector 42 generated. This detector consists of a series of cells that are photosensitive in the infrared range. This detector is cooled by cryogen and has an output connected to an input of the tracking arithmetic circuit 43 connected is. The through the device 39 Circular scan causes the image on the detector line 42 passes. The output of this detector 42 thus provides a video signal representing a radially scanned image. The device 43 determines a line of sight from the position of the target and its movements within the image sequence. The one in the device 43 applied algorithm is of conventional type.

The devices 40 and 44 are opto-mechanical devices that have an extended optical passband to obtain an image of the target in a large spectral range.

In each guidance system, harmonization is required between the sight line of the tracking devices and the sight line of the traffic cone scanning devices. These sightlines are not strictly colinear, because the plate 45 is not exactly at 45 ° to the optical axis of the zoom 38 and the scanning device 40 and the optical axis of the optical device 41 inclined; another reason is that the optical axes of all the optical elements are not completely stable when vibrations and temperature changes occur.

Before every start the control device leads 49 automatically harmonize the sightlines. For this purpose it controls the opening of a closure 46 that between the plate 45 and the cube corner 48 is inserted in the extension of the optical axis of the optical device 41 , This closure 46 then passes a fraction of the laser beam through the plate 45 is reflected. This fraction of the laser beam is through the cube corner 48 reflected back to itself, regardless of the orientation error of this cube corner 48 , He then passes through the lock 46 and then the plate 45 as well as the optical device 41 to turn on a cell of the detector 42 impinge.

If the harmonization is imperfect, hits the fraction of the laser beam that is on the detector 42 arrives, not to the point which represents the center of the picture. The device controls to measure the harmonization error in two orthogonal directions 49 the distractor 37 to produce a deflection of predetermined magnitude in the vertical plane, which manifests itself in a deflection of the laser beam incident on the detector 42 incident. An output of the detector 42 is connected to an input of the control device 49 connected to it to supply the video signal resulting from the deflection of the laser beam on the detector 42 results. The control device 49 determines two correction signals to a correction input of the acousto-optic deflector 37 or to a control input of the device 50 emits. When the device 49 has completed this action, it closes the closure 46 to prevent the fraction of the laser beam from receiving an image on the detector 42 disturbs.

Although the fraction of the laser beam coming from the plate 45 is reflected very small compared to the other fraction of this beam is the plate 45 It is necessary to have a damping plate 47 to arrange on the path of the fraction that passes through the cube corner 48 is reflected to the detector 42 not to saturate.

The measurement of the harmonization error takes place for several magnification values of the zoom 38 , The various corresponding values of the correction signals are in the device 49 stored and in real time the devices 37 . 50 supplied, in the rhythm of the increase of the magnification value during the flight of the missile.

The control means 39 include: a flow control 30 , an encoder 31 and a device 32 to the enlargement calculation. The flow control 30 has three outputs: a first output which gives an angle value θ to an input of the encoder 31 gives and the third output of the funds 39 forms; a second output providing a missile start signal to an input of the device 32 for magnification calculation outputs; and a third output that provides the value ρ. The device 32 determines the distance traveled by the missile from the time of its launch and deduces therefrom the magnification value G. An output of the device 32 forms the second exit of the means 39 ,

The encoder 31 also has an input connected to an output of the device 43 for tracking computation to supply it with a binary word representing a message to be transmitted to the missile. The encoder 31 forms a binary sequence consisting of the value ρ, the value θ and the message word. From the value ρ, the encoder determines 31 a deflection angle value φ corresponding to the position of a cell to be illuminated at a given time and that of a cell symmetrically located with respect to the axis of symmetry of the guide cone. To illuminate these two cells, the encoder modulates 31 the laser beam with the binary sequence and delivers to the deflector 37 a setpoint signal, the value of which is first + φ and then -φ), to first transmit the value 1 and then the value 0.

In the distractor 37 This will be done by the device 39 supplied signal algebraically added to the setpoint signal, which the encoder 31 supplies.

The 5 schematically shows an embodiment of the Kreisabtastvorrichtung 40 , It essentially comprises a cylinder 20 rotating about an axis BB 'which forms the optical axis of the device; This cylinder contains two prisms 21 . 22 as well as a mirror 23 , The two prisms 21 . 22 and the mirror 23 are on the cylinder 20 attached symmetrically with respect to a plane of symmetry of this cylinder, which is perpendicular to its axis of symmetry. A ray of light in the cylinder 20 enters and coincides with the axis BB ', through the prism 21 to the mirror 23 deflected, is reflected and then through the prism 22 distracted to get out of the cylinder 20 again along the axis BB 'exit. When the incident radiation forms a non-zero angle with the axis BB ', it turns out of the cylinder 20 outgoing beam around a cone whose axis of symmetry is BB 'and whose opening angle is equal to the angle of inclination of the incoming beam with respect to the axis BB'.

The cylinder 20 is driven at constant speed by an electric motor 27 in rotation, to which it passes through a mechanical transmission device 26 is coupled. A position detector 24 is at the cylinder 20 via a mechanical transmission device 25 coupled and provides an electrical signal indicating the angular position of the cylinder 20 about the axis BB 'with respect to a reference size, the z. B. is the vertical. A position control device 28 receives this electrical signal at a first input and receives a setpoint signal representing the value θ at a second input. An output of the device 28 is with an input of the engine 27 connected to this to supply a drive signal, which depends on the difference between the setpoint signal and the measurement signal that the detector 24 supplies.

to Realization of the circular scan can also be done by other devices Wollaston-Prima, Péchant prism, rotating Two-flat, etc.

The 6 to 8th illustrate the operation of this embodiment of the control system according to the invention. The 6 shows the evolution of the traffic cone in the course of the flight of the missile 4 , At the time considered, the missile becomes 4 through a traffic cone 5 steered, a cut surface 55 having a plane which is perpendicular to the axis of symmetry AS of the traffic cone. This surface 55 is approximately circular and has a diameter that varies depending on the distance that the missile 4 has covered. The evolution of the diameter of the surface 55 is shown in dashed lines.

When the missile 4 from a ramp 58 is stacked, the beam is from a guidance system 57 sent, which is near the ramp 58 located. The sight line LV of the control system 57 coincides with the symmetry axis AS of the traffic cone. The launcher of the ramp 58 is parallel to this line of sight, but does not coincide with it. At the beginning of the flight, the missile is thus outside the traffic cone. In order to avoid that the missile leaves the traffic cone and is lost, the opening angle of the traffic cone is increased during a so-called tracking phase until the missile has traveled a distance d1.

During this tracking phase, the traffic cone has 51 a fixed aperture that is relatively large and is achieved by the deflection amplitude of the acousto-optic deflector 37 caused distraction is increased. For this purpose, the encoder provides 31 the distractor 37 Setpoints φ which are greater than those corresponding to the subsequent flight phase. During this tracking phase, the zoom is received 38 a magnification value G which is the minimum value. The number of elementary cells forming the cone is constant throughout the flight of the missile, but during the tracking phase the elemental cells are located at the circumference of the cone 51 , There is thus an inactive rule 56 in which there is no elementary cell and no steering takes place. The missile 4 penetrates the traffic cone 51 by crossing the periphery obliquely, so that the absence of cells near the axis of the traffic cone is of no importance.

The 7 shows the section of the Leitzellen with a plane which is perpendicular to the axis of symmetry AS, at a time of the tracking phase, which corresponds, for example, the distance traveled d1.

This follow-up phase is followed by three more leadership phases. While the missile is at a distance that is between d1 and a distance d2, the diameter of the cut surface of the pilot cone is held constant by the deflection amplitude of the acousto-optic deflector 37 is kept constant, depending on the distance traveled by the missile. The surface 55 then shifts and creates a cylinder 52 , As the missile moves away, the diameter decreases Cut surface of each elementary cell too. Since the diameter of the cone is constant and the number of elemental cells is also constant, they gradually take up an increasing proportion of the surface 55 and approach more and more the axis of the cone.

The 8th shows the intersections of all the elemental cells that make up the traffic cone as the missile approaches distance d2. From this figure, it is apparent that an increase in the sectional area of each elementary cell occurs and a reduction in the sectional area of the inactive cone 56 entry. When the missile reaches the distance d2, there is no longer an inactive cone, and the elementary cells closest to the axis of symmetry AS overlap each other and surround this axis.

When the missile is at a distance that is between d2 and a distance d3, the diameter of the cut surface becomes 55 constant. For this purpose, the device increases 32 the setpoint for the magnification G, the zoom 38 is supplied. The surface 55 therefore moves with the missile in a cylinder 53 ,

If the missile exceeds the distance d3, the zoom has 38 reaches its maximum magnification, and it is no longer possible the diameter of the surface 55 hold constant. This therefore shifts and becomes linearly larger, depending on the distance covered, around a cone 54 to produce, which has a small opening.

The device 32 to calculate the magnification receives a start signal, which is the sequence control 30 supplies. From this point on, it determines the values for the magnification G as a function of a predetermined time law. The flow control 30 determines a sequence of values θ and a sequence of values ρ, whereby the sampling of the cone by means of the deflector 37 and the device 40 is realized. The sequence of values ρ develops as a function of the time from the start of the missile according to a predetermined time law. The determination of these two laws from the optical laws and from the characteristics of the zoom 38 as well as the distractor 37 lies within the scope of expert knowledge. The encoder 31 and the computing device 32 can be formed by a microprocessor. His programming is also within the skill of the art.

The 9 schematically shows a second embodiment of a system according to the invention, which differs from the first embodiment in that a different optical signal pickup is used for the tracking. This embodiment comprises an imager 60 which analyzes a two-dimensional image by a TV-type scan, each image consisting of mutually parallel lines. Those elements which are analogous to those in the first embodiment bear the same reference numerals but with an apostrophe.

Because the imager 60 performs an analysis according to two orthogonal axes, the circular scanning device is not used for the analysis of this image. The common channel for tracking and the means for scanning the traffic cone is thus on the directive device 44 ' reduced. On the other hand, the circular scanning device 40 ' before the aphocal zoom 38 ' arranged while the Kreisabtastvorrichtung 40 behind the aphocal zoom 38 was. This new arrangement allows a Kreisabtastvorrichtung 40 ' to be used, which is designed for a smaller beam diameter than in the previously described embodiment.

Otherwise, the device is the same as the first embodiment. A laser 33 ' delivers a beam successively through two deflecting mirrors 34 ' . 35 ' is reflected. The laser beam then traverses successively: an afocal optical matching device 36 '; an acousto-optic deflector 37 '; the circular scanning device 39 '; the afocal zoom 38 '; a dichroic plate 45 '; and the directive device 44 ' , The second embodiment further comprises: control means 39 '; an optical device 41 ' to generate an image on the imager 60 ; a device 49 ' to control the harmonization between the sighting lines; a closure 46 '; a steaming plate 47 '; a cube corner 48 '; and a position control 50 ' ,

in the Frame of the numerous embodiments of the invention In particular, it is intended to use a dichroic plate which reflects at the wavelength of the laser light and at the wavelengths to produce a target image is permeable. In this case, a permutation results the optical path of the means for scanning the traffic cone with the optical path through the shutter, the damping Plate and the cube corner is formed.

Further Also, a laser can be used whose wavelength deviates from 10.6 microns.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• - Optical Command and Beamrider Missile Guidance, RL Sitton, SPIE. Vol. 317, pp. 358-364 [0005]
• "Michael Higgins, Gerald Titus, John Evans, Richard Martyn, British Aerospace UK" - "An improved acousto-optic laser scanner guidance system" [0007]

Claims (11)

Guiding system for projectiles, in which a directional beam is used, which is coded in polar coordinates, wherein the firing station ( 1 ) comprises: - means ( 40 to 45 ) to pursue a goal ( 2 ) and definition of a sight line (LV); - Medium ( 30 to 40 . 44 ) for scanning a space area designated as a traffic cone by means of a laser ( 33 ) generated beam ( 3 ), this traffic cone having an axis of symmetry (AS) whose position of the line of sight (LV) is readjusted, and this traffic cone ( 5 ) from elemental cells ( 10 to 13 ; 10 ' to 13 ' ) which is successively passed through the beam ( 3 ) are illuminated; where the projectile ( 4 ): - means for receiving the laser beam ( 3 ); Means for determining the cell in which the projectile is located; and means for deriving therefrom a correction of the trajectory of the projectile in such a way that it adjoins the axis of symmetry (AS) of the cone ( 5 ) approximates; - means for carrying out this correction of trajectories; characterized in that the scanning means ( 30 to 40 . 44 ): - means ( 37 ) to the beam ( 3 ) to deflect in a plane passing through the axis of symmetry (AS) of the traffic cone; - Medium ( 39 ) for deflecting the beam ( 3 ) by placing this plane around the symmetry axis (AS) of the traffic cone ( 5 ) is twisted; - Medium ( 30 . 31 . 37 ) for modulating the laser beam ( 3 ) with a binary sequence that is different for each cell; and in that the means for receiving the laser beam ( 3 ) Have means to demodulate this beam and to decode the binary sequence. System according to claim 2, characterized in that the modulation means ( 30 . 31 . 37 ) an encoder ( 31 ) to provide binary sequences of such type that each cell corresponding sequence contains: a first binary word representing the angular position (θ) of a plane passing through that cell ( 6 ) and the symmetry axis (AS) of the traffic cone ( 5 ), this angular position being a first coordinate of the target ( 6 ) forms; and a second binary word representing the distance (ρ) of that cell ( 6 ) from the symmetry axis (AS), this distance being a second coordinate of the cell (FIG. 6 ) in a polar coordinate system whose origin (o) on the symmetry axis (AS) of the traffic cone ( 5 ) lies. System according to claim 1, characterized in that the scanning means ( 30 to 40 . 44 ) scan each cell twice in the course of one scan period of the entire cone, at a constant speed during a trace and at a constant speed during a retrace; and that the modulation means ( 30 . 31 . 37 ) an encoder ( 31 ) to provide binary sequences of such type that each sequence corresponding to a cell contains a binary word representing an angular position (θ) of a plane passing through that cell ( 6 ) and the symmetry axis (AS) of the traffic cone ( 5 ), this angular position being a first coordinate of the projectile ( 4 ) in the traffic cone ( 5 ); and such that their composition makes it possible to distinguish between trace and retrace; and in that the means for receiving the laser beam determine in which cell the projectile ( 4 ), having means for measuring the duration of the interval between two times at which the laser beam ( 3 ) is received to derive a second coordinate (ρ) therefrom. System according to claim 1, characterized in that for the modulation of the laser beam ( 3 ) placed in a given cell ( 9 ), facilities ( 31 . 37 ) are provided to the beam ( 3 ) for each bit of the sequence with a predetermined value (0) to a cell ( 9 ' ), which are symmetrical to the given cell ( 9 ) with respect to the axis of symmetry (AS), and the beam for each bit with the opposite value (1) to the given cell (FIG. 9 ) distract. System according to one of Claims 2 and 3, characterized in that the modulation means ( 30 . 31 . 37 ) an encoder ( 31 ) which further encodes a message to be transmitted in the binary sequence; and in that the means for receiving the laser beam ( 13 ) comprise a decoder for decoding this message. System according to claim 1, characterized in that the means ( 40 to 45 ) on target tracking and the means ( 30 to 40 . 44 ) for scanning the traffic cone ( 5 ) have a common optical path through a directional device ( 44 ) which orients the sighting line of the tracking means and the sighting line of the scanning means and by the means ( 40 ) for deflecting the beam ( 3 ) is formed in a plane passing through the axis of symmetry (AS); these means ( 40 ) and the directive device ( 44 ) through the laser beam ( 3 ) in one sense and in the opposite sense by a ray of light ( 29 ), which is caught in the sighting line (LV). A system according to claim 6, wherein the target tracking means comprises an optical detector ( 42 ), characterized in that in order to harmonize the sighting line of the target tracking means ( 40 to 45 ) with the line of sight of the funds ( 30 to 40 . 44 ) are provided for scanning the guide cone: a semipermeable plate ( 45 ); and a catadioptric device ( 48 ); wherein these elements are arranged in such a way that a fraction of the laser beam to a predetermined point of the detector ( 42 ) is projected when the sight lines are harmonized with each other. System according to claim 1, characterized in that the laser ( 33 ) is a CW laser, and that the modulation means further comprise means ( 31 ) to the laser beam ( 33 ) with a frequency much higher than the frequency of the bits in the binary sequence to be transmitted. System according to claim 1, characterized in that the laser ( 33 ) is a pulse laser whose frequency is greater than that of the binary bit sequence to be transmitted. System according to claim 1, characterized in that the laser ( 33 ) is a pulse laser whose frequency is twice that of the bits of the binary sequence to be transmitted, and in that the modulation means further comprise means for synchronizing the laser to the frequency of the bits in the sequence. System according to claim 1, characterized in that the scanning means ( 30 to 40 . 44 ) Facilities ( 30 to 32 ) to the opening ( 51 ) of the traffic cone ( 5 ) depending on the distance that the projectile ( 4 ), this opening being larger during a so-called follow-up phase during which the projectile ( 4 ) in the traffic cone ( 5 ) entry; further comprising means for detecting the elemental cells ( 6 ) during the tracking phase at the circumference of the traffic cone ( 5 ) while a central zone ( 56 ) remains without cells.