EP0809084A1 - Apparatus for determining the roll angle position of a flying device, especially of an ammunition - Google Patents

Abstract

The device uses a directional antenna (23) mounted on the shell body. The shell rotates in flight around its axis (21) and when the transmitter antenna points towards a GPS ground receiver (29) and antenna (28) there is a peak in received signals. The peak determines the shell angle of rotation at that instant allowing course correction signals to be calculated (27) relative to the shell missile body angle. The correction instruction (33) is transmitted from a ground GPS transmitter and received by an omni-directional antenna on the missile.

Description

The invention relates to a device for determining the roll orientation of a flying object, for example of ammunition. It applies in particular to the improvement of the effectiveness of artillery ammunition especially in the context of munitions with increased range.

Improving the effectiveness of artillery ammunition notably involves reducing the dispersion of their point of impact on the ground.

• la dispersion en portée, qui est dans le plan de la trajectoire théorique
• la dispersion latérale, qui est perpendiculaire au plan de la trajectoire théorique.

In general, this dispersion is characterized by the following two components:

• the range dispersion, which is in the plane of the theoretical trajectory
• lateral dispersion, which is perpendicular to the plane of the theoretical trajectory.

A known method, currently for reducing the imprecision of impact, consists notably in correcting the pointing angles of the tube, on the basis of information provided by advanced observers on the actual impact points of first projected munitions. There then remains in the dispersion, in addition to the error of appreciation of the observers, only the random part specific to each projectile and due to atmospheric turbulence.

• dans un premier temps corriger les angles de pointage pour les tirs futurs à partir des mesures de la trajectoire réelle du premier obus tiré, la nécessité d'observateurs étant ainsi supprimée,
• dans un deuxième temps corriger directement la trajectoire réelle, en utilisant des dispositifs de contrôle adaptés, embarqués dans la munition.

It is also known to provide an ammunition with devices capable of locating it by GPS systems or at low-cost inertial units for:

• first correct the aiming angles for future shots from measurements of the real trajectory of the first shell fired, the need for observers being thus eliminated,
• in a second step, directly correct the real trajectory, using suitable control devices, on board the munition.

• l'effet de surprise ne permet pas à la cible de quitter la zone visée,
• la minimisation du temps nécessaire pour réaliser un tir au but permet de quitter rapidement la position de tir, ce qui diminue fortement la probabilité de localisation par des radars de contre-batterie.

This second, more complex method has the advantage of avoiding adjustment shots. It allows shooting straight away. This is interesting from an operational point of view for at least the following two reasons:

• the surprise effect does not allow the target to leave the targeted area,
• minimizing the time required to make a shot on goal makes it possible to quickly leave the shooting position, which greatly reduces the probability of location by counter-battery radars.

• La première consiste à corriger uniquement les erreurs de portée. Il suffit donc d'une action dans le plan vertical qui peut être réalisée de façon relativement simple, en visant volontairement au-delà de la cible, puis en contrôlant la traînée aérodynamique par exemple par un système d'aérofrein. La courbure de la trajectoire est ainsi modulée. Le contrôle de la portée met en jeu des forces purement axiales et ne requiert donc que des informations de localisation de la munition.
• La deuxième étape, plus difficile à mettre en oeuvre, consiste à corriger à la fois les erreurs en portée et les erreurs latérales. Outre la nécessité de disposer d'actionneurs développant des forces perpendiculaires à la vitesse de la munition, il est de plus nécessaire de commander ces actionneurs lorsqu'ils sont dans une position propice pour résorber l'écart latéral de trajectoire. Cela nécessite donc de connaître l'orientation des forces de contrôle générées par les actionneurs, par rapport à une référence terrestre, par exemple la verticale.

Two stages are envisaged to correct the trajectory of the ammunition.

• The first is to correct only range errors. It therefore suffices an action in the vertical plane which can be carried out in a relatively simple manner, by voluntarily aiming beyond the target, then by controlling the aerodynamic drag for example by an air brake system. The curvature of the trajectory is thus modulated. The range control involves purely axial forces and therefore only requires information on the location of the ammunition.
• The second step, which is more difficult to implement, consists in correcting both the errors in range and the lateral errors. In addition to the need to have actuators developing forces perpendicular to the speed of the ammunition, it is also necessary to control these actuators when they are in a suitable position to absorb the lateral deviation from the trajectory. This therefore requires knowing the orientation of the control forces generated by the actuators, with respect to a terrestrial reference, for example the vertical.

The object of the invention is to determine the orientation in particular of a munition with respect to a terrestrial reference, for example the vertical plane. The angle of orientation thus defined is similar in fact to the roll angle of the munition.

• une antenne de réception d'un signal GPS
• des moyens de réémission du signal GPS vers le sol, les moyens de réémission comportant une antenne anisotrope au moins dans le plan de roulis de l'engin

   et en ce qu'il comporte au sol, au moins :

• des moyens de réception du signal GPS
• des moyens calculant l'angle que fait un premier plan avec un plan de référence lorsqu'une singularité d'anisotropie de l'antenne de réémission rencontre le premier plan, ce plan étant défini par le vecteur vitesse de l'engin et un vecteur dont l'origine et l'extrémité sont respectivement les points de référence des positions de l'engin et des moyens de réception du signal GPS, le point de référence de l'engin et son vecteur vitesse étant foumis par le signal GPS reçu par l'antenne embarquée et réémis vers les moyens de réception, l'angle calculé étant l'angle de roulis.

To this end, the subject of the invention is a device for determining the roll angle of a flying vehicle, characterized in that it includes, on board the vehicle, at least:

• an antenna for receiving a GPS signal
• means for re-transmitting the GPS signal towards the ground, the re-transmitting means comprising an anisotropic antenna at least in the roll plane of the machine

and in that it comprises on the ground, at least:

• means for receiving the GPS signal
• means calculating the angle that a first plane makes with a reference plane when a singularity of anisotropy of the antenna retransmission meets the foreground, this plane being defined by the speed vector of the machine and a vector whose origin and end are respectively the reference points of the positions of the machine and of the means for receiving the GPS signal, the reference point of the machine and its speed vector being provided by the GPS signal received by the on-board antenna and retransmitted to the reception means, the angle calculated being the roll angle.

The main advantages of the invention are that it allows the correction of trajectories in range and lateral without additional equipment of the vertical detector type on board the munition, that it allows trajectory correction calculations carried out on the ground, that it is simple to implement and is economical in particular insofar as it does not require a complete system on board in ammunition or any other flying vehicle.

• la figure 1, des exemples de trajectoires réelles et théoriques d'une munition avec des écarts en portée et en latéral au niveau des points d'impact,
• la figure 2, un mode de réalisation possible d'un dispositif selon l'invention,
• la figure 3, un exemple de signal réémis par une antenne embarquée dans une munition et anisotrope au moins dans le plan de roulis de la munition,
• la figure 4, une illustration de l'angle de roulis calculé par le dispositif selon l'invention à partir de données fournies par un système GPS combinées au signal précité relatif à la figure 3.

Other characteristics and advantages of the invention will become apparent from the following description given with reference to the accompanying drawings which represent:

• FIG. 1, examples of real and theoretical trajectories of an ammunition with deviations in range and laterally at the points of impact,
• FIG. 2, a possible embodiment of a device according to the invention,
• FIG. 3, an example of signal re-emitted by an antenna on board in a munition and anisotropic at least in the rolling plane of the ammunition,
• FIG. 4, an illustration of the roll angle calculated by the device according to the invention from data supplied by a GPS system combined with the aforementioned signal relating to FIG. 3.

FIG. 1 shows an example of the difference between a theoretical trajectory 1 and an actual trajectory 2 of an ammunition. The actual impact point Ir has a deviation Δx in range and Δy laterally from the theoretical impact point I _t . For a projectile with a range of approximately 20 km, the orders of magnitude of the deviations Δx and Δy are respectively 200m and 120m. Δy represents a deviation from the vertical plane 3 of the theoretical trajectory. As previously seen, the correction of the real trajectory requires knowing the angle that the ammunition makes with respect to a plane, preferably vertical, the angle considered being an angle of roll of the ammunition or of rotation around itself. In the remainder of the description, the determination of this angle will be applied for a munition with the aim in particular of correcting its trajectory. However, the invention can be applied to determine the roll angle of all types of flying machines regardless of the subsequent use of this angle. The flying devices can for example be shells, bombs, rockets, or missiles. The invention is particularly suitable for vehicles having rolling speeds of the order of, for example, from 10 to 50 revolutions per second.

FIG. 2 illustrates a possible embodiment of a device according to the invention. It includes elements on board the fired munition 21 and elements on the ground. One of the advantages of the invention is to place on the ground most of the complex and expensive elements, the elements placed in the munition being of low cost. Ground elements are common to several munitions, in practice to a large number of munitions.

The invention uses the known GPS system, this second expression coming from the Anglo-Saxon expression "Global Positioning System". The GPS system is used in particular to obtain the coordinates and the speed vector of the munition 21. In particular in order to minimize the so-called consumable costs, that is to say the costs linked to the ammunition which is used only once, munition 21 does not include a GPS receiver, an expensive system, but only a GPS antenna, with an annular structure for example, then means for re-transmitting this signal towards the ground. The retransmission means comprise at least one retransmission antenna 23 with an anisotropic structure in the rolling plane of the munition 21, that is to say in a plane perpendicular to its longitudinal axis 24. As will be explained later, the combination of the GPS signal and of a signal produced by the quality of anisotropy of the retransmission antenna 23 makes it possible according to the invention to determine the roll angle of the munition 21.

A transponder 25 is for example interposed between the GPS antenna 22 and the retransmission antenna 23. The GPS antenna receives a signal from a satellite and then the transponder 25 transposes the frequency of the signal received into another frequency band, from higher frequency preference. The transponder 25 for example transposes the GPS signal into the S band, any other frequency band can be envisaged depending on the application. Frequency transposition is preferable to avoid re-transmitting in the frequency band reserved for GPS signals and thus to avoid any risk of confusion.

On the ground, the device comprises at least one GPS receiver 26 and calculation means 27 which make it possible to define the angle made by a singular point of the retransmission antenna 23 with a reference plane passing through the roll axis of the ammunition 21, in fact its longitudinal axis 24, in particular from a particular signal picked up by the GPS reception means on the ground, when the singular point passes for example as close as possible to the latter. The angle thus defined represents the roll angle of the ammunition.

A reception antenna 28, operating for example in S-band receives the signal 32 re-emitted by the antenna 23 of the ammunition 21. The antenna 28 is for example connected to means 29 for transposing the received signal, for example in S-band , in the frequency band of GPS signals. The transposition means 29 are connected to the GPS receiver 26 via a two-position switch 30 for example. In a first position the switch 30 connects the GPS receiver 26 to an antenna 31. In a second position, it connects the frequency transposition means 29 to the GPS receiver 26. In the first position, the GPS system makes it possible to know the position of the antenna 31. When the switch switches to its second position, that is to say at the time of the firing, the receiver then indirectly exploits the signals received by the ammunition 21 and locates the latter as if it were on board .

The accuracy of the device can be significantly improved by using a second, fixed receiver allowing said differential positioning. The latter calculates corrections to be applied by the receiver 26, in the same way as a receiver carried by the munition.

The GPS information as such cannot provide any information on the orientation of the roll of the munition 21. To obtain the roll angle, the device according to the invention exploits the anisotropy property of the retransmission antenna 23 This antenna provides the reception means 28, 29, 26 located on the ground with characteristic information at each turn that the munition 21 performs on itself.

FIG. 3 shows an example of a characteristic signal as provided by the retransmission antenna 23, anisotropic at least in the rolling plane of the munition. The signal 32 retransmitted by the anisotropic antenna 23 is represented by its amplitude as a function of time t. This signal is for example in the S band. The abovementioned characteristic is for example a signal peak 39. This peak 39 appears each time that a singularity of the antenna passes opposite the reception means on the ground, for example in view of the S-band antenna 28. The singularity causing this signal characteristic is in particular a cause of anisotropy of the retransmission antenna 23, which operates in S-band for example, when using a transponder 25 of band S. The duration between two consecutive peaks 39 indicates the duration of a roll of the ammunition. The aforementioned singularity can be achieved in different ways known to those skilled in the art.

The calculation means 27 use the signal of FIG. 3 as well as the GPS data made up in particular of the position and the speed vector of the ammunition 21. Digitization means not shown, for example integrated into the calculation means 27, deliver the data and the aforementioned characteristics directly exploitable by the latter.

FIG. 4 illustrates a possible processing carried out by the calculation means 27. The latter use the base-munition direction, the base reference point being given by the signal received by the antenna 31 for receiving GPS on the ground. This direction is known with precision since the reference point of the base as well as the reference point of the ammunition 21 are perfectly determined by the GPS signals as it was seen previously.

. M étant le point de référence de la munition 21 et S étant le point de référence de la base au sol, la direction base-munition est portée par le vecteur d'origine S et d'extrémité M. Par la suite, le vecteur opposé $\overrightarrow{\text{MS}}$

est pris en compte.The signal peak 29 as for example illustrated by FIG. 3 appears when the singularity 41 of the retransmission antenna 23 passes as close as possible, for example to the antenna 28 for receiving band S, that is to say precisely when the singularity 41 passes in the plane Ps formed by the axis 24 of the munition 21 and the base-munition direction. The axis 24 of the ammunition is carried by a vector $\overrightarrow{\text{X}}$

. M being the reference point of the ammunition 21 and S being the reference point of the base on the ground, the direction base-ammunition is carried by the vector of origin S and of end M. Thereafter, the opposite vector $\overrightarrow{\text{MS}}$

is taken into account.

. En ce qui concerne le vecteur $\overrightarrow{\text{X}}$

qui porte l'axe 24 de la munition 21, ce vecteur $\overrightarrow{\text{X}}$

est, à quelques degrés près, colinéaire au vecteur vitesse $\overrightarrow{\text{V}}$

de la munition 21. Ce vecteur vitesse $\overrightarrow{\text{V}}$

est aussi obtenu au moyen des signaux GPS. Les quelques degrés d'erreur précités sont négligés et le vecteur $\overrightarrow{\text{X}}$

est considéré colinéaire au vecteur vitesse $\overrightarrow{\text{V}}$

. Les données GPS permettent donc alors d'obtenir le plan Ps formé par les vecteurs $\overrightarrow{\text{X}}$

et $\overrightarrow{\text{MS}}$

.M and S being given by the GPS signals, it is the same for the vector $\overrightarrow{\text{MS}}$

. Regarding the vector $\overrightarrow{\text{X}}$

which carries the axis 24 of the ammunition 21, this vector $\overrightarrow{\text{X}}$

is, to within a few degrees, collinear to the velocity vector $\overrightarrow{\text{V}}$

of ammunition 21. This speed vector $\overrightarrow{\text{V}}$

is also obtained by means of GPS signals. The aforementioned few degrees of error are neglected and the vector $\overrightarrow{\text{X}}$

is considered collinear to the velocity vector $\overrightarrow{\text{V}}$

. The GPS data therefore make it possible to obtain the plane Ps formed by the vectors $\overrightarrow{\text{X}}$

and $\overrightarrow{\text{MS}}$

.

. Les moyens de calcul 27 déterminent alors l'orientation en roulis de la munition 27 en exécutant par exemple des calculs appropriés à partir de données de position et de direction.According to the invention, the calculation means 27 exploit the fact that there is a correlation between the presence for example of a signal peak with a known direction in the terrestrial frame of reference, this known direction being carried by the vector $\overrightarrow{\text{MS}}$

. The calculation means 27 then determine the roll orientation of the ammunition 27 by performing, for example, appropriate calculations from position and direction data.

. L'instant d'apparition d'un pic correspond à l'instant où le vecteur $\overrightarrow{\text{Y}}$

se situe dans le plan Ps porté par les vecteurs $\overrightarrow{\text{X}}$

et $\overrightarrow{\text{MS}}$

.The direction of the singularity 41 of the retransmission antenna 23 is carried by a vector noted $\overrightarrow{\text{Y}}$

. The instant of appearance of a peak corresponds to the instant when the vector $\overrightarrow{\text{Y}}$

is located in the plane Ps carried by the vectors $\overrightarrow{\text{X}}$

and $\overrightarrow{\text{MS}}$

.

de la munition, approximativement colinéaire au vecteur $\overrightarrow{\text{X}}$

, et du vecteur $\overrightarrow{\text{MS}}$

défini par les points de référence de la munition 21 et de la base sol 28, 29, 26. Le vecteur $\overrightarrow{\text{MS}}$

et vecteur $\overrightarrow{\text{V}}$

sont issus des données de positionnement et de direction fournies par les signaux GPS.At this instant, the roll position of the munition 21 with respect to a reference plane is defined by the angle ϕ made by the plane Ps with this reference plane. The latter is for example the vertical plane P _v . At each round of ammunition, when the singularity 41 coincides in the plane Ps, the calculation means 27 can therefore determine the angle ϕ made by the singularity with for example the vertical plane P _v , which in fact gives an indication of l 'roll angle which is this calculated angle ϕ. Of course, the Ps plane varies during the time as a function of the trajectory of the munition 21. In a certain way, the measurements of the roll angle are sampled over time, the sampling instants being the instants where the characteristic 41 of the retransmission antenna 21 meets the plane Ps formed in fact of the velocity vector $\overrightarrow{\text{V}}$

of ammunition, approximately collinear to the vector $\overrightarrow{\text{X}}$

, and the vector $\overrightarrow{\text{MS}}$

defined by the reference points of the munition 21 and of the ground base 28, 29, 26. The vector $\overrightarrow{\text{MS}}$

and vector $\overrightarrow{\text{V}}$

are derived from positioning and direction data provided by GPS signals.

• $\overrightarrow{\text{X}}$
  
  étant le vecteur unitaire définissant l'axe 24 de la munition, pris par approximation colinéaire au vecteur vitesse $\overrightarrow{\text{V}}$
  
  de la munition
• $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  étant le vecteur du plan vertical Pv dirigé du point M de référence de la munition 21 vers le sol, le plan vertical contenant $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  et $\overrightarrow{\text{X}}$
  
  .
• $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  ∧ $\overrightarrow{\text{X}}$
  
  , $\overrightarrow{\text{X}}$
  
  ∧ $\overrightarrow{\text{MS}}$
  
  et $\overrightarrow{\text{X}}$
  
  ∧ $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  représentent respectivement les produits vectoriels entre les vecteurs $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  et $\overrightarrow{\text{X}}$
  
  , $\overrightarrow{\text{X}}$
  
  et $\overrightarrow{\text{MS}}$
  
  et $\overrightarrow{\text{X}}$
  
  et $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  .

The angle ϕ can be calculated by the calculation means 27 according to the following relation:

• $\overrightarrow{\text{X}}$
  
  being the unit vector defining the axis 24 of the ammunition, taken by collinear approximation to the speed vector $\overrightarrow{\text{V}}$
  
  ammunition
• $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  being the vector of the vertical plane Pv directed from the reference point M of the munition 21 towards the ground, the vertical plane containing $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  and $\overrightarrow{\text{X}}$
  
  .
• $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  ∧ $\overrightarrow{\text{X}}$
  
  , $\overrightarrow{\text{X}}$
  
  ∧ $\overrightarrow{\text{MS}}$
  
  and $\overrightarrow{\text{X}}$
  
  ∧ $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  respectively represent the vector products between the vectors $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  and $\overrightarrow{\text{X}}$
  
  , $\overrightarrow{\text{X}}$
  
  and $\overrightarrow{\text{MS}}$
  
  and $\overrightarrow{\text{X}}$
  
  and $\overrightarrow{{\text{Z}}_{\text{o}}}$
  
  .

de la munition et de l'angle ϕ de roulis.Once the angle ϕ has been calculated, the calculation means 27 can also carry out a processing operation to determine a correction order 33 to be sent to the munition 21. This correction order is in particular a function of the position of the ammunition in the terrestrial frame of reference. , from the position of the lens of the ammunition in the same terrestrial reference, of the speed vector $\overrightarrow{\text{V}}$

ammunition and roll angle ϕ.

It appears that the invention offers several advantages. It allows in particular a trajectory correction in range and lateral without additional equipment, for example of the vertical detector type on board the munition. The combination of GPS data and of the signal retransmitted by the anisotropic antenna 23 makes it possible according to the invention to determine the roll angle, necessary in particular for the correction of the trajectory in range and in side.

The cost of the materials on board the ammunition and necessary in particular for determining the roll angle ϕ are reduced insofar as it only requires at most one GPS antenna 22, a transponder 25 and a re-emission antenna 23. The costly means are placed on the ground and are common to all ammunition, these ground means are mainly the GPS receiver 26 and the means 27 for calculating the roll angle, then the antenna 28 for example of band S and the means of transposition 29.

Claims (9)

Device for determining the roll angle of a flying vehicle (21), characterized in that it includes, on board the vehicle (21), at least: - An antenna (22) for receiving a GPS signal - re-transmission means (23, 25) of the GPS signal towards the ground, the re-transmission means comprising an anisotropic antenna (23) at least in the roll plane of the vehicle (21) and in that it comprises on the ground, at least: - means (28, 29, 30, 26) for receiving the GPS signal - Means (27) calculating the angle (ϕ) made by a first plane (Ps) with a reference plane (Pv) when a singularity of anisotropy (41) of the antenna (23) of retransmission meets the foreground (P1), this plane (Ps) being defined by the speed vector ( $\overrightarrow{\text{V}}$

) of the machine (21) and a vector $\overrightarrow{\text{MS}}$

whose origin (M) and end (S) are respectively the reference points of the positions of the machine (21) and of the means (28, 29, 30, 26) for receiving the GPS signal, the point of reference (M) of the machine (21) and its speed vector being supplied by the GPS signal received by the on-board antenna (22) and retransmitted to the reception means (28, 29, 30, 26), the angle (ϕ) calculated as the roll angle. Device according to claim 1, characterized in that the retransmission means comprise a transponder (25) transposing the GPS signal into another frequency band, the retransmission antenna (23) being adapted to this latter frequency band, the means for receiving the GPS signal comprising on the ground, in addition to a GPS receiver (26), a suitable receiving antenna (28) and means (29) for transposing the signal received in the frequency band of GPS signals to supply the GPS receiver ( 26). Device according to claim 2, characterized in that the GPS signal is transposed in the S band. Device according to any one of the preceding claims, characterized in that the reference plane (Pv) is the vertical plane. Device according to any one of the preceding claims, characterized in that it comprises before the GPS receiver (26) a switch (30) which in a first position connects the input of the GPS receiver (26) to a GPS antenna (31 ) on the ground to determine the position of the reception means on the ground, and in a second position connects the input of the GPS receiver (26) to the signal (32) received from the flying vehicle (21). Device according to claim 5, characterized in that the switch (30) is in its first position before the launch of the machine (21). Device according to any one of the preceding claims, characterized in that the meeting of the singularity (41) of the anisotropic antenna (23) with the foreground (Ps) is defined by a peak (29) of the signal (32) received by the receiving means (28, 29, 30, 26) on the ground from the flying object (21). Device according to any one of the preceding claims, characterized in that the angle ϕ between the first plane (Ps) and the reference plane (Pv) is calculated by the calculation means (27) according to the following relation:

- $\overrightarrow{\text{MS}}$

being the vector having for origin and end respectively the reference points (M) of the machine (21) and (S) of the receiving means (28, 29, 30, 26) on the ground - $\overrightarrow{\text{X}}$

being a unit vector collinear with the speed vector ( $\overrightarrow{\text{V}}$

) of the machine (21) - $\overrightarrow{{\text{Z}}_{\text{o}}}$

being a vector of the reference plane not collinear with the vector $\overrightarrow{\text{X}}$

, the reference plane passing through it. Device according to any one of the preceding claims, characterized in that the flying object (21) is a munition.

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