TARGET SIGHTING SYSTEM

Description

[0001] The present invention relates to a target pointing system. The present invention also relates to an associated pointing method.

[0002] The pointing system in question is mounted on a support that is movable relative to the target. This support could be, for example, the frame of the pointing system itself, or a ground or aerial platform (such as a drone). The pointing system comprises a transmitting and receiving surface for a signal in a pointing direction and a pivoting mechanism that allows the orientation of the pointing direction relative to the support to be changed according to the relative movements of the target with respect to the support. The pivoting mechanism is designed to rotate the pointing direction around two axes: a first axis, called the "roll axis," coaxial with the principal axis of the support, and a second axis, called the "elevation axis," orthogonal to the first axis and to the pointing direction. The pointing direction is thus defined by a roll angle and an elevation angle in a coordinate system specific to the support.

[0003] Instructions in a hurry Ṙ And Ṡ to be applied respectively to the roll angle R and at the corner of the site S The following are necessary to maintain a constant pointing direction regardless of the movements of the support and the target: S ˙ = − q . cos R − r . sin R R ˙ = − p + − q . sin R + r . cos R tan S with p the rotational speed of the support around the roll axis, and q And r the rotational speeds of the support around respectively the pitch axis and the yaw axis, the pitch and yaw axes are orthogonal to the roll axis and orthogonal to each other.

[0004] From these equations, because of the term in 1 tan S We observe the existence of a singular point with zero site, that is, when the pointing direction is aligned with the roll axis. Indeed, when the site angle Stends towards 0, the theoretical roll speed to compensate for the movements of the support or target becomes infinite, so that it is impossible to follow the movements of a target close to the axis of the support.

[0005] Thus, when the target moves around the singularity, roll stresses can excite the platform due to abrupt changes. Furthermore, this requires a significant amount of energy to sustain these dynamics.

[0006] In EP 2 445 052 A, antennas were developed a few years ago that include a tri-axis positioner allowing the antenna's pointing direction to be pivoted around a so-called "cross-elevation" axis, used to eliminate a singular point in the antenna's pointing direction. Such an antenna is intended for satellite communication. In FR 3 055 050 A, a tertiary pivoting device is presented, comprising an electronic scanning module around the tertiary axis adapted to phase-shift the singular point.

[0007] However, these solutions require mechanical modifications and are not always compatible with the available space or are difficult to implement.

[0008] There is therefore a need for a means of orienting more simply and regardless of the available space, the pointing direction of a signal transmission / reception surface, mounted on a support, for tracking a target independently of the relative movements of the target with respect to the support.

[0009] For this purpose, the present description relates to a target pointing system, the pointing system being mounted on a support movable relative to the target, a reference frame, called the support frame, being defined relative to the support, the support frame having three axes orthogonal to each other among a primary axis, a secondary axis and a tertiary axis, the pointing system comprising: a. a transmitting-receiving surface of a signal in a pointing direction, the pointing direction being identified by a roll angle and a pitch angle in the support frame, b. a pivoting device suitable for modifying the orientation of the pointing direction according to a pivoting command, the pivoting device being suitable for rotating the pointing direction around the primary axis of the support frame to modify the roll angle and for rotating the pointing direction around the secondary axis of the support frame to modify the pitch angle, c.a device for continuously determining the pivoting setpoint as a function of the rotation speed of the support relative to the target, called the support-target speed, so as to orient the pointing direction towards the target), the pivoting setpoint comprising a rotation speed setpoint around the primary axis, called the roll speed setpoint, and a rotation speed setpoint around the secondary axis, called the elevation speed setpoint, the determining device being configured to: i. receive the support-target speed over time, ii. receive, at each instant, pointing data including the roll angle and the elevation angle of the pointing direction, the pointing direction being considered to be the direction of the target, iii. determine, at each instant, the elevation speed setpoint according to an elevation control law as a function of the received pointing data and the last received support-target speed, and iv.determine, at each instant, the roll speed command based on the received pointing data and the last received support-target speed, the roll speed command being determined according to different roll control laws when the elevation angle is greater than a limiting elevation angle, called the singular angle, and when the elevation angle is less than or equal to the singular angle.

[0010] Depending on specific embodiments, the pointing system comprises one or more of the following characteristics, taken individually or in all technically possible combinations: When the pitch angle is less than or equal to the singular angle, the roll control law is devoid of terms in 1 tan S with S the elevation angle of the pointing direction; the area of ​​space corresponding to elevation angles less than the singular angle is a cone, called the singular cone, the target being considered outside the singular cone when the elevation angle is greater than the singular angle, and in the singular cone otherwise, when the target is in the singular cone, the roll control law being a function of an estimate of the roll angle at the next exit of the target from the singular cone; the roll control law is: a. as long as the target is in the singular cone and the support-target velocity is constant, an initial roll control law determined at the last entry of the target into the singular cone, and b. when the target is in the singular cone, and each time the received support-target velocity varies, a roll control law is updated from the point in the singular cone corresponding to the reception of the support-target velocity;when the elevation angle is less than or equal to the singular angle, the determining device is configured to determine each of the initial roll control laws and any updated roll control laws based on an initial roll angle and a final roll angle, the initial roll angle being the roll angle at a point on the singular cone, called the starting point, the starting point being the point of entry of the target into the singular cone for the initial roll control law and being the point on the singular cone corresponding to the reception of the last support-target velocity for each updated roll control law, the final roll angle corresponding to the estimated roll angle at the next exit of the target from the singular cone,The next target exit is estimated by assuming that the target follows a predetermined trajectory from the starting point; when the elevation angle is less than or equal to the singular angle, the roll control law is a function of time whose coefficients are determined by the determining device as a function of the initial roll angle and the corresponding final roll angle, the function preferably being a polynomial function. When the elevation angle is less than or equal to the singular angle, the determining device is configured to estimate the final roll angle by transforming the received support-target velocity into linear velocities in a geometric frame, called the singular frame, the singular frame being a frame in polar coordinates whose radial coordinate is the elevation angle and whose angular coordinate is the roll angle.the rotational velocity of the target around the secondary axis being a linear velocity along the ordinate axis in the singular coordinate system, the rotational velocity of the target around the tertiary axis being a linear velocity along the abscissa axis in the singular coordinate system; the final roll angle is obtained by the following formula: , R F = R 0 + π − 2 α Or: R F is the final roll angle, R 0 is the initial roll angle, α = acos U → . V c → , U → = − sin R 0 cos R 0 , V c → = q − r with q the rotational speed of the support around the secondary axis and r the rotational speed of the support around the tertiary axis; when the elevation angle is greater than the singular angle, the roll control law is of the following form: R ˙ = − p + − q . sin R + r . cos R tan S Or: Ṙ is the roll speed setpoint, p is the rotational speed of the support around the primary axis, q is the rotational speed of the support around the secondary axis, and r is the rotational speed of the support around the tertiary axis. R is the roll angle of the pointing direction, and S is the angle of the site of the pointing direction.

[0011] The present invention also relates to a method for pointing at a target using a pointing system as described above, the method comprising the following steps: the determination, at each instant, by the determination device, of the pivoting command, comprising: ∘ the reception over time of the support-target velocity, ∘ the reception, at each instant, of the pointing data including the roll angle and the elevation angle of the pointing direction in the support frame, the pointing direction being considered to be the direction of the target, ∘ the determination, at each instant, of the elevation velocity command according to an elevation control law as a function of the received pointing data and the last received support-target velocity, and ∘ the determination, at each instant, of the roll velocity command as a function of the received pointing data and the last received support-target velocity, the roll velocity command being determined according to different roll control laws when the elevation angle is greater than a limiting elevation angle, called the singular angle,and when the elevation angle is less than or equal to the singular angle, the pivoting device modifies the orientation of the pointing direction according to the last determined pivoting setting.

[0012] Other features and advantages of the invention will become apparent from the following description of embodiments of the invention, given by way of example only and with reference to the drawings which are: [ Fig 1], Figure 1 , a schematic representation of an example of a target pointing system, the system being mounted on a support movable relative to the target, the system being pivotable (in roll and elevation) relative to the support, the system comprising a transmitting-receiving surface for a signal in a pointing direction, [ Fig 2], Figure 2 , a schematic representation of the pointing system of the figure 1 and roll and elevation angles allowing the orientation of the pointing direction to be determined in a frame of reference specific to the support, [ Fig 3], Figure 3 , a schematic representation of an example of different roll control laws depending on the target's position relative to the singular cone, [ Fig 4], Figure 4 , a schematic representation of radial coordinates in the singular frame, [ Fig 5], Figure 5 , a schematic representation of the angular coordinates in the singular frame, [ Fig 6], Figure 6 , a schematic representation of the transformation of the rotational velocity into pitch of the support relative to the target into a linear velocity in the singular frame of reference, [ Fig 7], Figure 7 , a schematic representation of the transformation of the yaw rate of rotation of the support relative to the target into a linear rate in the singular frame, [ Fig 8], Figure 8 , a schematic representation of the transformation of the rotational velocity (yaw, pitch) of the support relative to the target into a linear velocity in the singular frame of reference, [ Fig 9], Figure 9 , a schematic representation of the estimated trajectory of the target in the singular cone in the case of constant rotational speed of the support relative to the target, [ Fig 10], Figure 10 , a schematic representation of the boundary conditions, the initial roll angle and the estimated final roll angle allowing the roll control law to be determined when the target is in the singular cone, and [ Fig 11], Figure 11 , a schematic representation of the estimated trajectory of the target in the singular cone in the case of variable rotation speed of the support relative to the target.

[0013] A 20-point system for scoring a target C is illustrated by the figure 1 .

[0014] The pointing system 20 is mounted on a support 22 that is movable relative to the target C. The relative movements of the support 22 with respect to the target C are at least rotational movements (roll, yaw, pitch), and preferably also translational movements. The relative movements of the support 22 with respect to the target C are due either to the movement of the support 22 while the target C is fixed, or to the movement of the target C while the support 22 is fixed, or to a movement of both the support 22 and the target C.

[0015] A coordinate system, called the support frame, is defined with respect to support 22. The support frame is a coordinate system attached to support 22 (and therefore fixed with respect to support 22). The support frame comprises three axes orthogonal to each other, namely: a primary axis X, also called the roll axis, around which the roll rotation of support 22 relative to target C is defined; a secondary axis Y, also called the pitch axis, around which the pitch rotation of support 22 relative to target C is defined; and a tertiary axis Z, also called the yaw axis, around which the yaw rotation of support 22 relative to target C is defined. These axes are illustrated on the figures 1 And 2 .

[0016] The rotational speed of the support 22 relative to the target C is called the support-target speed VS. The support-target speed VS is, therefore, a relative speed that varies: when the speed of the target C varies while the support 22 is fixed, or when the speed of the support 22 varies while the target C is fixed, or when both the support 22 and the target C are moving and the speed of the target C varies relative to the speed of the support 22.

[0017] The support-target velocity VS includes a rotational velocity component around the primary axis X, called roll velocity p, a rotational velocity component around the secondary axis Y, called pitch velocity q, and a rotational velocity component around the tertiary axis Z, called yaw velocity r.

[0018] The support 22 is, for example, an element of the pointing system 20, such as a frame component. Alternatively, the pointing system 20 is a carrier, such as a drone or a targeting pod.

[0019] The pointing system 20 includes a transmitting-receiving surface 30, a pivoting device 32 and a determining device 34.

[0020] The transmitting-receiving surface 30 is designed to emit a signal in a pointing direction P. The signal is, for example, an electromagnetic wave. The transmitting-receiving surface 30 is, for example, an antenna.

[0021] The pointing direction P is defined by a roll angle R and a pitch angle S in the support frame. As illustrated by the figure 2 The roll angle R is the angle between the tertiary axis Z and the projection of the pointing direction P onto a plane orthogonal to the primary axis X (the YZ plane). The elevation angle S is the angle between the primary axis X and the pointing direction P. In what follows, the pointing direction P is considered to be the direction of the target C. Thus, the target C is initially pointed in the pointing direction P, and the pivot commands calculated below aim to maintain this alignment.

[0022] Typically, the roll angle R varies between 0 and 360°. On the other hand, the elevation angle S varies between 0 and 60° (no negative elevation due to a technological limitation of the transmitting-receiving surface 30).

[0023] The area of ​​space corresponding to site angles less than the singular angle SL is a cone, called the singular cone C sing. The target C is considered outside the singular cone C sing when the site angle S of the target C is greater than the singular angle SL, and inside the singular cone C sing otherwise.

[0024] The transmitting-receiving surface 30 is designed to be rotated relative to the support 22 so as to change the orientation of the pointing direction P. Preferably, the rotation occurs only around the primary axis X (to change the roll angle R) and the secondary axis Y (to change the elevation angle S). The transmitting-receiving surface 30 is therefore not designed to rotate in azimuth.

[0025] The pivoting device 32 is designed to modify the orientation of the pointing direction P according to a pivoting instruction.

[0026] In particular, the pivoting device 32 is suitable for rotating the pointing direction P around the primary axis X of the support frame to change the roll angle R and for rotating the pointing direction P around the secondary axis Y of the support frame to change the elevation angle S.

[0027] In one embodiment, the pivoting device 32 includes a first intermediate support 40, a first actuator 42, a second intermediate support 44, and a second actuator 46.

[0028] The first intermediate support 40 is mounted to rotate freely relative to the support 22 around the primary axis X. The transmitting-receiving surface 30 is mounted on the first intermediate support 40.

[0029] The first actuator 42 is designed to drive the first intermediate support 40 in rotation around the roll axis X of the support frame. The first actuator 42 is, for example, a motor.

[0030] The second intermediate support 44 is mounted to rotate movably relative to the support 22 around the secondary axis Y. The transmitting-receiving surface 30 is mounted on the second intermediate support 44.

[0031] The second actuator 46 is designed to drive the second intermediate support 44 in rotation around the secondary axis Y of the support frame. The second actuator 46 is, for example, a motor.

[0032] Alternatively, the transmitting-receiving surface 30 is an electronically scanned antenna, and the pivoting of the pointing direction P around the secondary axis Y is achieved by electronic scanning replacing the second intermediate support 44 and the second actuator 46.

[0033] The determination device 34 is, for example, a computer interacting with a computer program product. In this case, the computer includes a processor comprising a data processing unit, memory, and a data storage device. Alternatively, the determination device 34 is implemented at least partially as a programmable logic component, or even as a dedicated integrated circuit.

[0034] The determining device 34 is configured to continuously determine the pivoting command as a function of the rotation speed of the support 22 relative to the target C, referred to as the support-target speed VS, so as to orient the pointing direction P towards the target C. More precisely, the pivoting command aims to keep the pointing direction P substantially aligned with the target C. By substantially, it is understood that a tolerance of a few degrees is allowed. Furthermore, as will be explained later in the description, the pointing direction P is potentially misaligned with the target within the singular cone, but becomes substantially aligned with the target again upon exiting the singular cone.

[0035] The pivoting command includes a rotation speed command around the primary X axis, called the roll speed command. Ṙ and a rotation speed setpoint around the secondary Y axis, called the elevation speed setpoint Ṡ .

[0036] The determining device 34 is configured to determine the speed setpoint by implementing steps of a method for pointing at a target C. Such a method is described below.

[0037] The scoring process is implemented by the scoring system 20 described previously.

[0038] In particular, the pointing process includes a step 100 for determining the pivoting setpoint at each instant and a step 200 for modifying the orientation of the pointing direction P according to the last determined pivoting setpoint. Step 100 is implemented by the determining device 34. Step 200 is implemented by the pivoting device 32.

[0039] The determination step 100 includes the time-dependent measurement of the target-support velocity VS. The target-support velocity VS is acquired, for example, at regular time intervals, such as every 5 milliseconds. The target-support velocity VS is obtained, for example, through measurements taken by a sensor or by an inertial measurement unit specific to the support 22.

[0040] The determination step 100 includes the reception, at each instant, of pointing data DP comprising the roll angle R and the elevation angle S of the pointing direction P. The pointing data DP is, for example, obtained from a sensor. The roll angle R is, for example, obtained by a position copy encoder of the first intermediate support 40. The elevation angle S is, for example, obtained by the antenna (range measurement).

[0041] The determination step 100 includes determining, at each instant, the site speed setpoint Ṡ according to a site control law based on the received DP pointing data and the last received support-target VS velocity.

[0042] Preferably, the site command law is of the following form: S ˙ = − q . cos R − r . sin R Or : Ṡ is the elevation speed setpoint, q is the rotational speed of support 22 around the secondary Y axis, r is the rotational speed of support 22 around the tertiary Z axis, and R is the roll angle.

[0043] The determination step 100 includes determining, at each instant, the roll speed setpoint. Ṙ based on the DP scoring data received and the last received support-target VS velocity.

[0044] The roll speed instruction Ṙ is determined according to different roll control laws when the pitch angle S is strictly greater than a limiting pitch angle, called the singular angle SL, and when the pitch angle S is less than or equal to the singular angle SL. The singular angle is typically a few degrees, for example, is less than or equal to 5 degrees. figure 3 illustrates an example of the different roll control laws applied in and out of the singular cone C sing.

[0045] Preferably, when the elevation angle S is strictly greater than the singular angle SL, the roll control law is of the following form: R ˙ = − p + − q . sin R + r . cos R tan S Or: Ṙ is the roll speed setpoint, p is the rotation speed of support 22 around the primary axis X, q is the rotation speed of support 22 around the secondary axis Y, r is the rotation speed of support 22 around the tertiary axis Z, Ris the roll angle of the pointing direction P, and S is the angle of the site of the pointing direction P.

[0046] Preferably, when the pitch angle S is less than or equal to the singular angle SL, the roll control law is devoid of terms in 1 tan S with S the angle of the site of the pointing direction P.

[0047] In an example implementation, when target C is in the singular cone C sing, the roll control law is a function of an estimate of the roll angle R of target C at the next exit of target C from singular cone C sing.

[0048] According to this implementation example, the roll control law is preferably: as long as the target C is in the singular cone C sing and the support-target velocity VS is constant, an initial roll control law determined at the last entry of the target C into the singular cone C sing, and when the target C is in the singular cone C sing, and each time the received support-target velocity VS varies, a roll control law updated from the point in the singular cone C sing corresponding to the reception of the support-target velocity VS.

[0049] According to this implementation example, preferably, when the site angle S is less than or equal to the singular angle SL, each of the initial roll control law and any updated roll control laws are determined as a function of an initial roll angle R 0 and a final roll angle RF.

[0050] The initial roll angle R0 is the roll angle at a point in the singular cone Csing, called the starting point PD. The starting point PD is the entry point of the target C into the singular cone Csing for the initial roll control law and is the point in the singular cone Csing corresponding to the reception of the last support-target velocity VS for each updated roll control law.

[0051] The final roll angle RF corresponds to the estimated roll angle at the next exit of target C from the singular cone C sing. The next exit of target C is estimated by assuming that target C follows a predetermined trajectory from the starting point PD. The predetermined trajectory is, for example, a straight path.

[0052] Preferably, when the pitch angle S is less than or equal to the singular angle SL, the roll control law is a function of time whose coefficients are determined by the determining device 34 as a function of the initial roll angle R0 and the corresponding final roll angle RF. The function is preferably a polynomial function.

[0053] Preferably, when the site angle S is less than or equal to the singular angle SL, the determination device 34 is configured to estimate the final roll angle RF by transforming the received support-target velocity VS into linear velocities in a geometric frame, called a singular frame.

[0054] The singular frame of reference is a polar coordinate system where the radial coordinate (expressed in radians) is the elevation angle S and the angular coordinate is the roll angle R. The rotational velocity of the target C around the secondary axis Y (pitch) is a linear velocity along the vertical axis Zsing in the singular frame of reference. The rotational velocity of the target C around the tertiary axis Z (yaw) is a linear velocity along the horizontal axis Ysing in the singular frame of reference.

[0055] THE figures 4 And 5 These respectively illustrate the radial and angular coordinates in the singular frame. Thus, each position of the target C in space is defined by a position in the singular frame (O, Ysing, Zsing) and vice versa. This position is unique. Indeed, the transformation from 3-dimensional space to the 2-dimensional singular frame (O, Ysing, Zsing) is bijective.

[0056] THE figures 6 And 7 respectively illustrate the transformations of the rotational speed of support 22 in the singular frame of reference. Indeed, let us consider a rotational speed q of support 22 around its secondary axis Y, in relative terms this amounts to a velocity of the target C in -q relative to support 22. In the singular frame of reference this velocity becomes a linear velocity along Zsing (see figure 6 ). Let us consider a rotational speed r of support 22 around its tertiary axis Z, in relative terms this amounts to a velocity of the target C in -r relative to support 22. In the singular frame of reference, this velocity becomes a linear velocity along the -Ysing axis (see figure 7 ).

[0057] There figure 8 This illustrates the transformation of the rotational motion of support 22 into pitch and yaw in the singular frame of reference. The rotational motion of support 22 into pitch and yaw is thus transformed into a linear velocity of the target C in the singular frame of reference. This linear velocity is given by the value in the new frame of reference. V c = q - r .

[0058] Recall that we are trying to calculate the roll rate to keep the pointing direction P constant on the target C. When the target C is located within the singular cone Csing (near the zero point), we estimate the trajectory of the target C to find its exit point PF from the cone using the new coordinate system in which the rotational velocities are transformed into linear velocities. More precisely, the different parameters of the trajectory are expressed as follows with reference to the figure 9 : Either R 0 the roll angle when target C enters the singular cone C sing.

[0059] Either V c = q - r the velocity of the target C at the entrance of the singular cone C sing.

[0060] Initially, we assume that the velocity remains constant within the singular cone C sing: By geometric construction, the exit point PF is calculated as follows: U = − sin R 0 cos R 0 is a unit vector oriented towards the center of the singular coordinate system. α = atan2 ( U ) - atan2 ( Vc ) is the angle between the velocity vector V c and the unit vector U The function atan2(y,x) is a variant of the arctangent function. For all non-zero real arguments x and y, atan2(y,x) is the angle in radians between the positive part of the x-axis of a plane and the point in that plane with coordinates (x,y). The roll angle corresponding to the exit point PF of the singular cone C sing is: R F = R 0 + π - 2 α.

[0061] The magnitude of the trajectory segment in the cone is: d = |2 cos( α ). S |

[0062] The time required to traverse the singular cone C sing is: T = d r 2 + q 2

[0063] In this implementation example, the roll control law is generated as follows with reference to the figure 10 Thanks to the bijectivity of the transformation from support to singular frame of reference, tracking the target C in the new two-dimensional frame is equivalent to tracking the orientation of the target C in real space. Thus, knowing the input and output information of the singular cone Csing, the boundary conditions, and the initial and final conditions, a roll velocity command is generated. Ṙ in a predetermined form. This could be a polynomial function, trigonometric function, etc.

[0064] For example, in the case of a 3rd-order polynomial order: The speed command in the cone is Ṙ ( t ) = poly ( t ) = at 3< + bt 2< + ct + d Initial condition: R(0) = R 0 Final condition: R(T) = R F Continuity of velocity at the boundaries of the singular cone C sing: Poly 0 = − p 0 + − q . sin R 0 + r . cos R 0 tan S 0 Poly T = − p T + − q . sin R F + r . cos R F tan S T With S(T) = S(0) = S L limiting site angle of the singular cone C sing.

[0065] Thus, from the 4 equations above, we can deduce the 4 unknowns. a, b, c And d, and therefore the speed command to control roll and pointing direction P.

[0066] Thus, in this implementation example, the generated speed setpoint comes from a prediction that anticipates the movement of the target C in the singular cone C sing.

[0067] There figure 11 This illustrates the case of a variation in the velocity of the target C or the support 22 in the singular cone C sing. For example, velocity or position information for the support 22 and the target C is obtained via sensors carried by the support 22. This information is updated at a given rate.

[0068] To take into account the change in dynamics in the singular cone C sing, we regularly update the position of the target C in the cone (P DM ) and we again predict the exit point (P FM ) of the target C in the singular cone C sing .

[0069] For the prediction, the trajectory considered is a linear trajectory or any other extrapolation. Next, the intersection of this trajectory with the circle of the singular cone Csing is calculated to deduce the final roll angle at the exit point. This update is performed at the refresh rate of the dynamic velocity and position information for the support 22 and the target C, or at longer intervals. With each update, the exit point, and therefore the final roll angle, is adjusted. Consequently, the roll control law is also updated so that the pointing is as close as possible to the direction of the target C.

[0070] Modification step 200 involves changing the orientation of the pointing direction P according to the last determined pivoting instruction. Specifically, the pointing direction P is pivoted around the primary axis according to the roll rate instruction. Ṙ and is pivoted around the secondary axis according to the site speed command Ṡ .

[0071] Thus, the present control system allows controlled, limited and optimal roll control to maintain a constant or slightly modified pointing direction P, and this independently of the movements of the support 22 when the target C is in the singular cone C sing.

[0072] The proposed solution overcomes the singular point problem without requiring any mechanical modification to the control system, particularly the addition of a third pivot axis. Indeed, the invention only involves an evolution of the control laws (software modification). It enables controlled and intelligent control (anticipating the target C). Furthermore, the energy and speed required to control the roll direction of the pointing direction P are optimized.

[0073] The described pointing system was tested for various pitch and roll values. The following values ​​pertain to one of the tested examples: q = 35° / s (pitch), r = 0° / s (yaw), and SL = 3° (singular angle), using a polynomial control law in t3 within the singular cone. The resulting roll rate is 15.4 rad / s, the roll acceleration is 866 rad / s2, and the motor torque is 12 Nm. These values ​​can be compared with those obtained for a state-of-the-art roll control system (in 1 tan S ) in the singular cone, namely 27.2 rad / s for the roll rate, 2632 rad / s² for the roll acceleration, and 34 Nm for the engine torque. The pointing accuracy is essentially the same for both solutions, namely a circular deviation of less than 1° and an elevation deviation of less than 0.05°. Thus, these results clearly demonstrate the significant gain in speed and energy of the pointing system of the invention.

Claims

1. Pointing system (20) for a target (C), the pointing system (20) being mounted on a support (22) mobile with respect to the target (C), a frame, called support frame, being defined with respect to the support (22), the support frame having three axes orthogonal to one another from among a primary axis (X), a secondary axis (Y) and a tertiary axis (Z), the pointing system (20) comprising: a. a transmitting-receiving surface (30) for a signal in a pointing direction (P), the pointing direction (P) being identified by a roll angle (R) and an elevation angle (S) in the support frame, b. a pivoting device (32) suitable for modifying the orientation of the pointing direction (P) as a function of a pivoting setpoint, the pivoting device (32) being suitable for pivoting the pointing direction (P) about the primary axis (X) of the support frame in order to modify the roll angle (R) and for pivoting the pointing direction (P) about the secondary axis (Y) of the support frame in order to modify the elevation angle (S), c. a device (34) for continuously determining the pivoting setpoint as a function of the speed of rotation of the support (22) with respect to the target (C), called support-target speed (VS), so as to orient the pointing direction (P) toward the target (C), the pivoting setpoint comprising a setpoint for speed of rotation about the primary axis (X), called roll speed setpoint (Ṙ), and a setpoint for speed of rotation about the secondary axis (Y), called elevation speed setpoint (S), characterized in that the determination device (34) is configured to: i. receive over time the support-target speed (VS), ii. receive, at each instant, pointing data (DP) comprising the roll angle (R) and the elevation angle (S) of the pointing direction (P), the pointing direction (P) being considered to be the direction of the target (C), iii. determine, at each instant, the elevation speed setpoint (Ṡ) according to an elevation control law as a function of the pointing data (DP) received and of the last support-target speed (VS) received, and iv. determine, at each instant, the roll speed setpoint (Ṙ) being determined according to different roll control laws when the elevation angle (S) is greater than a limit elevation angle, called singular angle (SL), and when the elevation angle (S) is less than or equal to the singular angle (SL).

2. Pointing system (20) according to claim 1, wherein when the elevation angle (S) is less than or equal to the singular angle (SL), the roll control law is devoid of terms in 1 tan S with S the elevation angle of the pointing direction (P).

3. Pointing system (20) according to claim 1 or 2, wherein the region of space corresponding to elevation angles less than the singular angle (SL) is a cone, called singular cone (Csing), the target (C) being considered outside the singular cone (Csing) when the elevation angle (S) is greater than the singular angle (SL), and in the singular cone (Csing) otherwise, when the target (C) is in the singular cone (Csing), the roll control law being a function of an estimation of the roll angle (R) upon the next exit of the target (C) from the singular cone (Csing).

4. Pointing system (20) according to claim 3, wherein the roll control law is: a. as long as the target (C) is in the singular cone (Csing) and the support-target speed (VS) is constant, an initial roll control law determined upon the last entry of the target (C) into the singular cone (Csing), and b. when the target (C) is in the singular cone (Csing), and each time the support-target speed (VS) received varies, a roll control law updated from the point of the singular cone (Csing) corresponding to the reception of the support-target speed (VS).

5. Pointing system (20) according to claim 4, wherein when the elevation angle (S) is less than or equal to the singular angle (SL), the determination device (34) is configured to determine each of the initial roll control law and of the possible updated roll control laws as a function of an initial roll angle (R0) and of a final roll angle (RF), the initial roll angle (R0) being the roll angle at a point of the singular cone (Csing), called starting point (PD), the starting point (PD) being the point of entry of the target (C) into the singular cone (Csing) for the initial roll control law and being the point of the singular cone (Csing) corresponding to the reception of the last support-target speed (VS) for each updated roll control law, the final roll angle (RF) corresponding to the roll angle estimated upon the next exit (PF) of the target (C) from the singular cone (Csing), the next exit of the target (C) being estimated by assuming that the target (C) follows a predetermined trajectory from the starting point (PD).

6. Pointing system (20) according to claim 5, wherein when the elevation angle (S) is less than or equal to the singular angle (SL), the roll control law is a function of time of which the coefficients are determined by the determination device (34) as a function of the corresponding initial roll angle (R0) and final roll angle (RF), the function being preferably a polynomial function.

7. Pointing system (20) according to claim 5 or 6, wherein when the elevation angle (S) is less than or equal to the singular angle (SL), the determination device (34) is configured to estimate the final roll angle (RF) by transformation of the support-target speed (VS) received into linear speeds in a geometric frame, called singular frame, the singular frame being a frame in polar coordinates of which the radial coordinate is the elevation angle (S) and the angular coordinate is the roll angle (R), the rotational speed of the target (C) about the secondary axis (Y) being a linear speed along the axis of ordinates (Zsing) in the singular frame, the rotational speed of the target (C) about the tertiary axis (Z) being a linear speed along the axis of abscissas (Ysing) in the singular frame.

8. Pointing system (20) according to any one of claims 5 to 7, wherein the final roll angle (RF) is obtained by the following formula: R F = R 0 + π − 2 α Where: - RF is the final roll angle, - R0 is the initial roll angle, - α = acos U → . V c → , U → = − sin R 0 cos R 0 , - V c → = q − r with q the speed of rotation of the support (22) about the secondary axis (Y) and r the speed of rotation of the support (22) about the tertiary axis (Z).

9. Pointing system (20) according to any one of claims 1 to 8, wherein when the elevation angle (S) is greater than the singular angle (SL), the roll control law is of the following form: R ˙ = − p + − q . sin R + r . cos R tan S Where: - Ṙ is the roll speed setpoint, - p is the speed of rotation of the support (22) about the primary axis (X), q the speed of rotation of the support (22) about the secondary axis (Y) and r the speed of rotation of the support (22) about the tertiary axis (Z), - R is the roll angle of the pointing direction (P), and - S is the elevation angle of the pointing direction (P).

10. Method for pointing a target (C) by a pointing system (20) according to any one of claims 1 to 9, the method comprising the following steps: a. the determination, at each instant, by the determination device (34), of the pivoting setpoint, comprising: i. the reception over time of the support-target speed (VS), ii. the reception, at each instant, of the pointing data (DP) comprising the roll angle (R) and the elevation angle (S) of the pointing direction (P) in the support frame, the pointing direction (P) being considered to be the direction of the target (C), iii. the determination, at each instant, of the elevation speed setpoint (Ṡ) according to an elevation control law as a function of the pointing data (DP) received and of the last support-target speed (VS) received, and iv. the determination, at each instant, of the roll speed setpoint (Ṙ) as a function of the pointing data (DP) received and of the last support-target speed (VS) received, the roll speed setpoint (Ṙ) being determined according to different roll control laws when the elevation angle (S) is greater than a limit elevation angle, called singular angle (SL), and when the elevation angle (S) is less than or equal to the singular angle (SL), b. the modification, by the pivoting device (32), of the orientation of the pointing direction (P) as a function of the last determined pivoting setpoint.