MOTOR-DRIVEN AIMING DEVICE AND METHOD

Abstract

A method of controlling a motor-driven aiming device, the method including the steps of servo-controlling the motor as a function of a difference between a nominal speed setpoint and a measurement of the angular speed sensor, and in the event of saturation, determining a correction value for correcting the nominal speed setpoint as a function of a difference between a reference inertial position prior to the saturation and a current inertial position, and applying the correction value to the nominal speed setpoint. An aiming device for implementing the method.

Claims

1. A method of controlling an aiming device comprising a stationary structure having mounted thereon a support so as to be steerable about at least one axis of rotation by means of at least one motor, the support being provided with at least one inertial sensor of angular speed about that axis, the method comprising the steps of: servo-controlling the motor as a function of a difference between a nominal speed setpoint and a measurement of the angular speed sensor, and monitoring for the motor becoming saturated; and in the event of saturation being detected, determining a correction value for correcting the nominal speed setpoint as a function of a difference between a reference inertial position prior to the saturation and a current inertial position, and applying the correction value to the nominal speed setpoint.

2. The method according to claim 1, wherein the correction value is obtained by a correction of the proportional integral correction type.

3. An aiming device comprising a stationary structure having mounted thereon a support to be steerable about at least one axis of rotation by means of at least one motor connected to a control unit, the device being characterized in that the support is provided with at least one inertial sensor of angular speed about that axis, and in that the control unit is arranged: to servo-control the motor as a function of a difference between a nominal speed setpoint and a measurement of the angular speed sensor, and monitoring for the motor becoming saturated; and in the event of saturation being detected, to determine a correction value for correcting the nominal speed setpoint as a function of a difference between a reference inertial position prior to the saturation and a current inertial position, and applying the correction value to the nominal speed setpoint.

4. The device according to claim 3, wherein the correction value is obtained via a correction of the proportional integral correction type.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0014] Reference is made to the accompanying drawing, in which:

[0015] FIG. 1 is a diagrammatic view of an aiming device in accordance with the invention; and

[0016] FIG. 2 is a view showing diagrammatically how the motor of the aiming device is controlled.

DETAILED DESCRIPTION OF THE INVENTION

[0017] With reference to FIG. 1, the aiming device of the invention comprises a stationary structure 1 in which there is mounted a support 2 to pivot about an axis 3, which is vertical in this example. The structure 1 is arranged to be secured on a carrier, e.g. a vehicle or a tank turret. The support 2 is arranged to carry the element that is to be aimed, a weapon or an aiming device, for example, and it is connected to the structure 1 by rolling bearings coaxial about the axis 3.

[0018] The angular position of the support 2 is adjustable about the axis 3 by means of an electric motor 4 having an outlet shaft connected via motion transmission means to a ring that is coaxial about the axis 3 and that is secured to the support 2. The motion transmission means may for example be gears, a belt, cables, . . . . The motor may also be mounted to be directly engaged with the element that is to be driven, thereby connecting the structure 1 to the support 2.

[0019] The support 2 is also fitted with an inertial sensor for sensing angular speeds about the axis 3, namely a gyro 5. The electric motor 4 and the gyro 5 are connected to a computer control unit 6 arranged to run a control program and including an interface enabling an operator of the aiming device to input data into the control program. The computer control unit 6 continuously stores the angular speed measured by the gyro 5.

[0020] The operation of the control program is illustrated in FIG. 2 in the form of a control system given overall reference 10 and arranged to control the electric motor 4 as a function of a nominal speed setpoint {dot over (?)} calculated from data input by the operator of the aiming device.

[0021] The control system comprises a main control loop 20 and a correction loop 30 that intervenes in the event of the electric motor 4 becoming saturated.

[0022] The main control loop 20 comprises a control element 21 for controlling motors that determines the control parameters for the electric motor 4 as a function of a difference between a speed setpoint {dot over (?)}.sub.l and a speed of the support 2, written {dot over (?)}.sub.M. The speed {dot over (?)}.sub.M is measured by the gyro 5.

[0023] The correction loop 30 comprises an estimator 31 for estimating the difference between a reference inertial position prior to saturation and a current inertial position, and a corrector 32 that is arranged to correct the nominal speed setpoint {dot over (?)} as a function of the difference. This correction is a correction of the proportional integral type that supplies a corrected speed setpoint {dot over (?)}.sub.c. The correction loop 30 also has a detector 33 for detecting saturation of the electric motor 4 on the basis of saturation information coming from the control element 21. The detector 33 serves to monitor the occurrence of saturation of the electric motor 4 and it is arranged to activate the correction loop 30 in the event of the electric motor 4 saturating. A summing circuit 34 adds the nominal speed setpoint {dot over (?)} and the corrected speed setpoint {dot over (?)}.sub.c in order to obtain the speed setpoint {dot over (?)}.sub.l.

[0024] Thus, in normal operation, when saturation does not occur, the speed setpoint {dot over (?)}.sub.l is equal to the nominal speed setpoint {dot over (?)}.

[0025] In contrast, in the event of said saturation, the correction loop 30 is activated by the detector 33 so that the nominal speed setpoint {dot over (?)} is corrected by the corrector 32, which supplies the corrected speed setpoint {dot over (?)}.sub.c.

[0026] Naturally, the invention is not limited to the embodiments described but encompasses any variant coming within the ambit of the invention as defined by the claims.

[0027] In particular, the support 2 may be mounted in the structure 1 so as to be adjustable in position about two mutually perpendicular axes, for example. The support 2 may be mounted in the structure 1 to be adjustable in elevation and in bearing relative to the structure 1 by means of two motors using either an inertial angle sensor having two sensing axes or else two inertial angle sensors each having one sensing axis.

[0028] The invention is applicable to any aiming device that is arranged to steer any element in a predetermined direction.

[0029] The support may be fitted with a plurality of inertial sensors: a first sensor used for the conventional stabilization control loop, and a gyro for the correction loop.

[0030] It is possible either to use an absolute reference position value, as mentioned above, or else to use the current absolute position error as calculated at each iteration of the control.

[0031] The method may be implemented continuously by adding an outer absolute (or inertial) position loop. The device for implementing the method then does not have elements for triggering and stopping the function 33; there is no reference measurement made by the estimator and the speed setpoint supplied by the operator is always corrected by the speed setpoint from the corrector 32. This implementation serves to reduce considerably the impact of friction and also to increase performance in terms of stabilizing oscillations of the servo-controlled system. The method can thus also be used as a friction compensator.