Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41G—WEAPON SIGHTS; AIMING
  • F41G7/00—Direction control systems for self-propelled missiles
  • F41G7/20—Direction control systems for self-propelled missiles based on continuous observation of target position
  • F41G7/22—Homing guidance systems
  • F41G7/2246—Active homing systems, i.e. comprising both a transmitter and a receiver
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41G—WEAPON SIGHTS; AIMING
  • F41G7/00—Direction control systems for self-propelled missiles
  • F41G7/20—Direction control systems for self-propelled missiles based on continuous observation of target position
  • F41G7/22—Homing guidance systems
  • F41G7/2273—Homing guidance systems characterised by the type of waves
  • F41G7/2286—Homing guidance systems characterised by the type of waves using radio waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/88—Radar or analogous systems specially adapted for specific applications
  • G01S13/883—Radar or analogous systems specially adapted for specific applications for missile homing, autodirectors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
  • G01S13/88—Radar or analogous systems specially adapted for specific applications
  • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
  • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
  • G01S13/904—SAR modes
  • G01S13/9041—Squint mode

Definitions

• the present invention relates to guided or missile-type ammunition comprising a homing device (AD).
• munitions mainly comprise an inertial unit, a GPS receiver and control surfaces to control the trajectory of the ammunition and its roll.
• missile type ammunition comprising a synthetic SAR (Synthetic Aperture Radar) synthetic radar SAR (AD).
• SAR Synthetic Aperture Radar
• a homing device equipped with a radar in Synthetic Aperture Radar (SAR) mode enables an all-weather metric precision guidance of a munition on a target in a complex environment, even in the presence of heavy rainfall.
• Radar guidance in radar SAR mode is known to those skilled in the art.
• a squint angle (or "squint" angle according to the English terminology generally used by those skilled in the art) is required between the propagation direction of the radar waves and the carrier velocity vector.
• the movement of the ammunition provides exploitable information comparable to Doppler measurements.
• the SAR detection is advantageously used for an observation of the Earth in carriers of the type of reconnaissance aircraft or artificial satellite
• the carrier has in these cases a well-defined and regular trajectory
• the squint angle is close to 90 °, which is the ideal configuration.
• the SAR detection induces significant constraints on the trajectory of a missile type munition comprising a homing device (AD) during the acquisition of the radar signal, since the missile must move towards the target it observes.
• Figure 1 shows schematically the projection in a horizontal plane of the trajectory 5 of a missile 1 to a target 2 (also called desired impact point PID).
• the target 2 is visible on the one hand by the missile 1 when the image is taken and on the other hand that the missile moves towards the target.
• the squint angle should not be too big.
• the visualization of the target is complicated by the uncertainties on the relative position between the missile 1 and the target 2. These errors are due to the combination of the designation errors of the target 2 and the missile location errors 1 in position and in attitude.
• the trajectory 5 corresponds to the terminal phase of the missile path between the first radar signal acquisition and the impact.
• the trajectory 5 can be divided into two parts 51 and 52.
• the part 51 corresponds to the phase during which the missile can take images.
• Part 52 corresponds to the phase during which it becomes necessary to reach the estimated position of the target 2. Due to the need for squint, it becomes during this phase difficult or impossible to take images of the estimated target. After part 51, it is almost impossible to take images centered on the estimated target, but it may be interesting to take images by aiming at other points on the ground that are compatible with the target 2's joining by the missile 1. These ground points are offset from the target, but if the munition knows the relative position of these points relative to the estimated target, it may improve the impact accuracy.
• the invention proposes to overcome at least one of the disadvantages of the missiles of the prior art.
• the invention proposes a missile equipped with a homing device comprising an antenna of a synthetic aperture radar having a main direction of detection, characterized in that the antenna is arranged relative to the missile so that the main direction of the antenna is fixed relative to the missile and offset by a constant angle relative to a longitudinal axis of the missile.
• the angle of offset between the main direction of the antenna and the longitudinal axis of the missile is between 5 ° and 35 °, preferably substantially equal to 10 °;
• the missile further comprises means able to vary the transmitting / receiving surface of the antenna, so that the detection field of the antenna also varies;
• the antenna is a slot antenna;
• the missile further comprises means capable of controlling the control surfaces of the missile in order to modify the roll angle of the missile;
• the invention also relates to a method for guiding and controlling a missile according to the invention
• the guidance and control method is characterized in that it comprises a step in which the image is taken by means of the antenna, the antenna being arranged relative to the missile so that the main direction of the antenna is fixed relative to the missile and offset by a constant angle with respect to a longitudinal axis of the missile.
• the emitter / receiver surface of the antenna is varied so that the detection field of the antenna also varies
• the missile roll angle is varied to obtain a better aiming of the target or to refine the slope of the missile, radar detection data are used to readjust the errors in the navigation speed of the missile;
• radar discrepancy information is used to improve the relative position of the reconstructed radar image with respect to the missile
• the image-taking phase is triggered as soon as the homing device detects a signal whose signal-to-noise ratio exceeds a given threshold
• a calibration phase is made for altitude errors between the missile and the ground before the image is taken, in order to optimize the probability of viewing the target in the image;
• a missile comprising a searcher head without axis of movement relative to the missile is reliable and economical.
• the missile is easy to manufacture.
• FIG. 2 schematically shows the arrangement of a main direction of an antenna in a missile according to the invention
• FIG. 3 schematically represents the projection of velocity vectors in a vertical plane containing the missile / target axis for two different slopes
• FIG. 4 shows schematically the projection in the plane transverse to the axis missile / target roll for two angles of incidence.
• similar elements bear identical reference numerals.
• FIG. 2 shows that a missile 1 according to the invention is mainly equipped with a homing device comprising an antenna 7 of a synthetic aperture radar.
• the antenna 7 has a main direction of detection 70, corresponding to the direction of the main lobe of the antenna.
• the antenna 7 is arranged relative to the missile 1 so that the main direction 70 of the antenna is fixed on the one hand with respect to the missile, and on the other hand offset by a constant offset angle ⁇ relative to the a longitudinal axis 6 of the missile 1.
• the offset angle ⁇ is set at a value greater than the minimum squint angle.
• the missile is guided in attitude so that the antenna is aimed at the estimated target while respecting the squint angle. This induces a trajectory of the missile with a maximum chance of correct correction.
• the angle ⁇ of offset between the main direction 70 of the antenna and the longitudinal axis 6 of the missile is greater than or substantially equal to the minimum squint angle to obtain a satisfactory resolution image.
• the angle ⁇ has a value between 5 ° and 35 °, preferably substantially equal to 10 °.
• ⁇ is the offset angle and ⁇ H is the projection of this angle in a horizontal plane.
• FIG. 2 shows that when the missile is navigating on its trajectory 5, the instantaneous squint angle ⁇ is equal to the offset angle ⁇ H plus a skid angle ⁇ of the missile 1 on its trajectory 5.
• the angle y of skid reflects the fact that the speed vector 3 of the missile is not exactly coincident with the axis 6 of the missile.
• ⁇ H is the offset angle of the axis 70 of the antenna relative to the axis of the missile in the horizontal plane. It is the ⁇ H part of the angle ⁇ which participates in the squint angle, with the skid y for complement.
• the angle is often greater than zero but with low values, which still contributes to the squint.
• the angle y can of course be zero at given times.
• the roll angle of the missile is controlled so that ⁇ H is substantially equal to ⁇ . It is for this reason that by construction ⁇ is set to a value greater than the minimum squint angle.
• a method of guiding a missile according to the invention uses guiding and driving laws which enslave the position of the axis 6 of the munition in the space so that the main axis 70 of the antenna is aimed at zone containing target 2 during the image capture phase.
• This mode of guidance / guidance in aiming makes it possible to ensure the presence of the target 2 in the main lobe of the antenna 7 and to maintain the squint angle a during the acquisition of the radar signal.
• FIG. 1 already partially commented, represents an example of a trajectory 5 of a missile 1 towards a target 2.
• the velocity vector 3 is parallel to the axis 6 of the missile 1.
• the trajectory 5 corresponds to the terminal phase of the missile between the first radar signal acquisition and the impact.
• Part 51 corresponds to the phase during which images can be taken.
• Part 52 corresponds to the phase during which it becomes necessary to reach the estimated position of the target 2. Due to the need for squint, it becomes during this phase difficult or impossible to take images of the estimated target.
• the position 11 of the missile 1 corresponds to the first acquisition of the radar signal (image).
• the position 12 of the missile 1 corresponds to the last acquisition of the radar signal (image) and corresponds to the transition between the first and the second part.
• the squint angle ⁇ 1 is measured between the velocity vector 31 and the axis 41 missile 1 - target 2
• the axis 41 coincides with the axis 70.
• a coordinate attitude aiming law is used, with control of the roll angle.
• the squint angle a2 is measured between the velocity vector 32 and the axis 42 missile 1 - target 2.
• the axis 42 corresponds again to the axis
• the guidance / steering of the missile is to enslave its attitude so that the direction of the radar antenna is directed at the estimated target, and that the roll of the missile is controlled such that the ammunition meets the minimum squint angle during the part 51 of the terminal trajectory (which leads the munition to follow the trajectory 51).
• a proportional navigation law is used, for example.
• the angle of approach of the velocity vector with respect to the horizontal is between 20 ° and 45 ° for example.
• the angle of the velocity vector with respect to the vertical impact is between 70 "and 45 ° for example.
• the guide / control laws are known to those skilled in the art and are not described in more detail in the following description. In addition, other guide laws / steering than those mentioned here are possible.
• the criteria advantageously used as end of pursuit criteria are as follows.
• the instant squint angle must be less than the minimum squint angle of approximately 10 °.
• the viewing angle of the target 2 should be greater than about 45 °.
• the true target must be located off the main lobe of antenna 7.
• the missile must reach the estimated target.
• the missile furthermore preferably comprises means able to vary the transmitting / receiving surface of the antenna 7.
• the detection field of the antenna also varies. Thus, the surface of the antenna can be reduced at the beginning of the first part of the trajectory 5 to have a very large main lobe.
• the chances of finding the target 2 are increased, in the case where inaccuracies on the position of the missile 1 relative to the target 2 are important.
• the inaccuracies may be due to a misidentification of the target, and / or strong misalignment errors of the missile 1 in position and attitude due for example to a jamming of the GPS and a drift of the missile on the trajectory between the release and the first image in position 11.
• the antenna surface is increased to obtain a finer detection of said target.
• the antenna 7 is a slot antenna.
• the width of the main lobe of the antenna is for example substantially equal to 7.5 ° and the radar range at the beginning of search is for example 2500 m.
• the missile advantageously comprises means capable of controlling the control surfaces of the missile to modify in particular the roll angle of the missile on the trajectory. You can get a better aim of the target or refine the slope of the missile.
• the use of the roll angle of the missile 1 makes it possible to increase or refine the area 8 displayed on the ground.
• the enslavement of the aiming direction of the missile then corresponds to a polar coordinate system whose variable is the roll of the ammunition.
• Figure 3 shows that the roll may also be useful in adjusting a slope of the munition.
• Figure 4 shows that the roll ⁇ can also be used to control the altitude of the missile and its incidence. Roll control techniques and their influences on the trajectory are known to those skilled in the art.
• radar detection data are also used to readjust errors in the navigation speed of the missile.
• radar deviation information is used to improve the relative position of the reconstructed radar image relative to the missile.
• the image capture phase is triggered as soon as the homing device detects a signal whose signal-to-noise ratio exceeds a given threshold.
• a altitude error registration phase is performed between the missile and the ground before the image is taken, in order to optimize the probability of viewing the target 2 in the image.

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• Engineering & Computer Science (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Computer Networks & Wireless Communication (AREA)
• General Physics & Mathematics (AREA)
• Radar Systems Or Details Thereof (AREA)
• Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)

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• 2004
  • 2004-12-22 FR FR0413713A patent/FR2879753B1/fr not_active Expired - Lifetime
• 2005
  • 2005-12-22 WO PCT/EP2005/057117 patent/WO2006067220A2/fr active Application Filing
  • 2005-12-22 EP EP05825298A patent/EP1839009A2/fr not_active Withdrawn

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