EP0809084B1 - Apparatus for determining the roll angle position of a flying device, especially of an ammunition - Google Patents

Description

The invention relates to a device for determining the orientation. roll of a flying object, for example of ammunition. It applies especially for improving the efficiency of artillery ammunition especially as part of extended range ammunition.

Improving the effectiveness of artillery ammunition goes in particular by 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 dispersion in range, 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 imprecision of impact notably consists in correcting the pointing angles of the tube, from information provided by advanced observers on the actual impact points of first projected munitions. There does not remain then in the dispersion, in addition to the error of appreciation of the observers, that the random part specific to each projectile and due to turbulence atmospheric.

It is also known to provide a missile with means of correction of its range trajectory, as described in document US-A-3 374,967.

• 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:

• initially 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, embedded in 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.

The latter method, which is more complex, offers 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 traínée 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 connaítre 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 aiming voluntarily beyond the target, then by controlling the aerodynamic drag for example by a system of airbrake. 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 reduce the lateral deviation of 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 ammunition with respect to a terrestrial reference, for example the plan vertical. The orientation angle thus defined is similar in fact to the angle of ammo roll.

• 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 fournis 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 an anisotropy singularity of the retransmission antenna meets the first plane, this plane being defined by the speed vector of the machine and a vector whose the origin and the 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 correction of trajectories in range and lateral without equipment of the vertical detector type on board the ammunition, that it allows trajectory correction calculations made at soil, that it is simple to implement and that it is economical in the especially since it does not require a complete on-board system in ammunition or any other flying object.

• 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 with the aid of the description which follows given with reference to the appended 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 real 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 seen above, 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 d 'herself. 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 ammunition 21 and elements on the ground. One of the interests of the invention is to have at the ground most of the complex and expensive elements, the elements arranged in ammunition being of low cost. Ground elements are common to several munitions, in practice 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 velocity vector of ammunition 21. In particular for minimize the so-called consumable costs, i.e. the costs linked to the ammunition that is used only once, ammunition 21 does not include GPS receiver, expensive system, but only a GPS antenna, annular structure for example then means for retransmitting this signal to the ground. The retransmission means comprise at least one antenna reissue 23 with anisotropic structure in the ammunition rolling plane 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 a signal produced by the quality of anisotropy of the retransmission antenna 23 allows according to the invention to determine the roll angle of the ammunition 21.

A transponder 25 is for example interposed between the antenna GPS 22 and the retransmission antenna 23. The GPS antenna receives a signal from a satellite then the transponder 25 transposes the frequency of the signal received in another frequency band, preferably of higher frequency. The transponder 25 for example transposes the GPS signal in the S band, any other frequency band is possible depending on the application. Frequency transposition is preferable for avoid re-transmitting in the frequency band reserved for GPS signals and 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 point singular of the retransmission antenna 23 with a passing reference plane by the roll axis of the munition 21, in fact its longitudinal axis 24, from in particular of a particular signal received by the GPS reception means at ground, when the singular point passes for example closest to these last. The angle thus defined represents the roll angle of the ammunition.

A reception antenna 28, operating for example in a band S receives the signal 32 retransmitted by the antenna 23 of the munition 21. The antenna 28 is for example connected to means 29 for transposing the received signal, by example in S band, in the frequency band of GPS signals. The transposition means 29 are connected to the GPS receiver 26 via a switch 30 with two positions 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 allows know the position of the antenna 31. When the switch switches in its second position, that is to say at the time of the firing, the receiver operates then indirectly the signals received by ammunition 21 and locates this last as if he were on board.

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

GPS information as such cannot provide no information on the direction of the roll of the ammunition 21. To obtain the roll angle, the device according to the invention exploits the property anisotropy of the retransmission antenna 23. This antenna provides the reception means 28, 29, 26 located on the ground information characteristic at each turn that the ammunition 21 performs on itself.

Figure 3 shows an example of a characteristic signal such as supplied by the retransmission antenna 23, anisotropic at least in the plane of ammo roll. The signal 32 re-emitted by the anisotropic antenna 23 is represented by its amplitude as a function of time t This signal is by example in band S. The above characteristic is for example a peak 39 signal. This peak 39 appears whenever a singularity of the antenna passes opposite the reception means on the ground, for example by look of the antenna of band S. The singularity causing this signal characteristic is notably a cause of anisotropy of the retransmission antenna 23, which operates in S band for example, in the case of using an S-band transponder 25 The time between two peaks 39 consecutive indicates the duration of a roll of the ammunition. The aforementioned singularity can be achieved in various ways known to the skilled person.

The calculation means 27 use the signal of FIG. 3 as well that the GPS data consisting in particular of the position and the vector speed of the munition 21. Digitization means not shown, for example integrated into the calculation means 27, deliver the data and above characteristics directly exploitable by them.

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

The signal peak 29 as for example illustrated in Figure 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 through 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 X . M being the reference point of the ammunition 21 and S being the reference point of the base on the ground, the base-munition direction is carried by the vector of origin S and of end M. Thereafter, the opposite vector MS is taken into account.

M and S being given by the GPS signals, it is the same for the vector MS . Regarding the vector X which carries the axis 24 of the munition 21, this vector X is, to within a few degrees, collinear to the velocity vector V of ammunition 21. This speed vector V is also obtained by means of GPS signals. The aforementioned few degrees of error are neglected and the vector X is considered collinear to the velocity vector V . The GPS data therefore make it possible to obtain the Ps plane formed by the vectors. X and MS .

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, this known direction being carried by the vector 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.

The direction of the singularity 41 of the retransmission antenna 23 is carried by a vector noted Y . The instant of appearance of a peak corresponds to the instant when the vector Y is located in the plane Ps carried by the vectors X and MS .

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 plane Ps varies over time as a function of the trajectory of the munition 21. In a certain way, the roll angle measurements are sampled over time, the sampling instants being the instants where the particularity 41 of the retransmission antenna 21 meets the plane Ps formed in fact of the speed vector V ammunition, approximately collinear to the vector X , and the vector MS defined by the reference points of the munition 21 and of the ground base 28, 29, 26. The vector MS and vector V are derived from positioning and direction data provided by GPS signals.

• X étant le vecteur unitaire définissant l'axe 24 de la munition, pris par approximation colinéaire au vecteur vitesse V de la munition
• Z_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 Z_o et X.
• Z_o ∧ X, X ∧ MS et X ∧ Z_o représentent respectivement les produits vectoriels entre les vecteurs Z_o et X, X et MS et X et Z_o .

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

• X being the unit vector defining the axis 24 of the ammunition, taken by collinear approximation to the speed vector V ammunition
• Z _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 Z _o and X .
• Z _o ∧ X , X ∧ MS and X ∧ Z _o respectively represent the vector products between the vectors Z _o and X , X and MS and X and Z _o .

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 munition in the terrestrial frame of reference. , of the position of the target of the ammunition in the same terrestrial reference, of the speed vector V the ammunition and the roll angle ϕ.

It appears that the invention offers several advantages. She allows in particular a trajectory correction in range and lateral without additional equipment, for example of the vertical detector type loaded in the ammunition. The combination of GPS data and signal re-emitted by the anisotropic antenna 23 makes it possible according to the invention to determine the roll angle, necessary in particular for correcting the span and lateral trajectory.

The cost of the materials loaded in the ammunition and necessary in particular to the determination of the roll angle ϕ are reduced in the since it only requires at most one GPS 22 antenna, one transponder 25 and a retransmission antenna 23. Expensive means are arranged on the ground and are common to all ammunition, these means on the ground are mainly the GPS receiver 26 and the computing means 27 for the roll angle, then the antenna 28 for example of band S and the means of transposition 29.

Claims (9)

1. Device for determining the angle of roll of a projectile (21), characterized in that it comprises, on board the projectile (21), at least:

   an antenna (22) for receiving a GPS signal

   means of retransmission (23, 25) of the GPS signal to the ground, the retransmission means comprising an antenna (23) which is anisotropic at least in the plane of roll of the projectile (21)

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

   means (28, 29, 30, 26) of reception of the GPS signal

   means (27) calculating the angle (ϕ) made by a first plane (Ps) varying over time as a function of the trajectory of the projectile (21) with a reference plane (Pv) when a singularity of anisotropy (41) of the retransmission antenna (23) meets the first plane (Ps), this plane (Ps) being defined by the velocity vector (V) of the projectile (21) and a vector MS whose origin (M) and tip (S) are respectively the reference points of the positions of the projectile (21) and of the means of reception (28, 29, 30, 26) of the GPS signal, the reference point (M) of the projectile (21) and its velocity vector being supplied by the GPS signal received by the onboard antenna (22) and retransmitted to the means of reception (28, 29, 30, 26), the angle (ϕ) calculated being the angle of roll.
2. 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 matched to this latter frequency band, the means of reception of the GPS signal comprising on the ground, in addition to a GPS receiver (26), a matched reception antenna (28) and means (29) of transposition of the signal received into the frequency band of the GPS signals so as to supply the GPS receiver (26).
3. Device according to Claim 2, characterized in that the GPS signal is transposed into the S band.
4. Device according to any one of the preceding claims, characterized in that the reference plane (Pv) is the vertical plane.
5. Device according to any one of the preceding claims, characterized in that it comprises ahead of the GPS receiver (26), a switch (30) which in a first position links the input of the GPS receiver (26) to a GPS antenna (31) on the ground so as to determine the position of the ground reception means and in a second position links the input of the GPS receiver (26) to the signal (32) received from the projectile (21).
6. Device according to Claim 5, characterized in that the switch (30) is in its first position before the launching of the projectile (21).
7. 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 first plane (Ps) is defined by a spike (29) of the signal (32) received by the ground reception means (28, 29, 30, 26) from the projectile (21).
8. Device according to any one of the preceding claims, characterized in that the means of calculation (27) carry out the following operation:

   

   so as to calculate the angle between the first plane (Ps) and the reference plan (Pv)

   ϕ being the angle between the first plane (Ps) and the reference plane (Pv);

   MS being the vector whose origin and tip are respectively the reference points (M) of the projectile (21) and (S) of the ground reception means (28, 29, 30, 26)

   X being a unit vector collinear with the velocity vector ( V) of the projectile (21)

   Z_o being a vector of the reference plane which is not collinear with the vector X, the reference plane passing through the latter.
9. Device according to any one of the preceding claims, characterized in that the projectile (21) is a munition.

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