ADAPTIVE FEEDBACK CONTROL OF AN OPTRONIC SIGHT

Abstract

An optronic sight for a motorized vehicle such as an aerial or marine vehicle propelled by a propeller, or a tracked land vehicle. The optronic sight can include an aiming module, means for moving the aiming module about the first and second axes, and means for continuously measuring angular data. The optronic sight can further include a feedback control loop having means for continuously measuring the acceleration of the aiming module in three orthogonal directions of the space, means for detecting at least one fundamental frequency of the vibratory disturbances, and an adaptive corrector configured to continuously receive as input said fundamental frequency, a discrepancy between an angular setpoint value and said angular data, output a movement setpoint value to the moving means.

Claims

1. An optronic sight for a motorized vehicle such as an aerial or marine vehicle propelled by a propeller or a tracked land vehicle, the optronic sight comprising: an aiming module configured to be moved about a first axis and a second axis not parallel to the first axis, means for moving the aiming module about the first and second axes, means for continuously measuring an angular data of the aiming module about the first and second axes; a feedback control loop, comprising: means for continuously measuring the acceleration of the aiming module according to three orthogonal directions of a space; and, means for detecting at least one fundamental frequency of the vibratory disturbances generated by the operation of the motorized vehicle, the at least one fundamental frequency being obtained based on the output data of the acceleration measuring means; and an adaptive corrector configured to: continuously receive as input: said fundamental frequency; and, a discrepancy between an angular setpoint value and said angular data; and output a movement setpoint value to the moving means.

2. The optronic sight of claim 1, wherein the means for continuously measuring the angular data include a gyroscope configured to obtain an angular position or a gyrometer configured to obtain an angular speed.

3. The optronic sight of claim 1, wherein the means for measuring the acceleration comprise an accelerometer.

4. The optronic sight of claim 1, wherein the fundamental frequency is obtained by Fast Fourier Transform followed by a calculation of a maximum in the frequency band obtained after carrying out the Fast Fourier Transform or by phase-locked loop.

5. The optronic sight of claim 1, wherein the adaptive corrector comprises a Linear Variant Parameter corrector.

6. The optronic sight of claim 5, wherein the adaptive corrector follows a state representation according to the following formula: where xk is the state variable of the corrector, ε_k is the feedback control error at the input of the adaptive corrector, uk is the digital motor command calculated by the adaptive corrector (output of the corrector), fmin and fmax are two frequencies limiting the fundamental frequency in real-time f{circumflex over ( )}_vk of the disturbing vibrations γ_vib.

7. The optronic sight of claim 5, wherein the Linear Variant Parameter (LPV) corrector comprises the following affine state matrices: where A0, B0, C0, D0, A1, B1, C1, D1 designate matrix gains which are the parameters saved in the memory of the corrector.

8. The optronic sight of claim 1, wherein the first axis and the second axis are perpendicular to each other.

9. A motorized vehicle, such as an aerial or marine vehicle propelled by a propeller or a tracked land vehicle, comprising an optronic sight according to claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0022] FIG. 1 is a schematic view of an optronic sight of the prior art,

[0023] FIG. 2 is a diagram representing the operation of an optronic sight in the prior art,

[0024] FIG. 3 is a schematic view of an optronic sight according to the invention,

[0025] FIG. 4 is a diagram representing the operation of an optronic sight according to the invention,

DETAILED DESCRIPTION OF THE INVENTION

[0026] FIGS. 3 and 4 respectively illustrate a schematic view of an optronic sight 2 and a diagram representing the operation of such a sight according to an embodiment of the invention.

[0027] Similarly to the prior art, said optronic sight 2 comprises in particular: [0028] an aiming module 4 able to be moved about a first axis 8a and a second axis 10 perpendicular to the first axis, [0029] means 17a, 17b for moving the aiming module 4 about the first 8a and second 10 axes, [0030] means 14 for continuously measuring an angular data of said module about the first 8a and second 10 axes.

[0031] In the embodiment illustrated in the figures, the first axis 8a and the second axis 10 are perpendicular but it should be understood that the details of embodiments given hereinafter are also applicable to embodiments wherein the axes are not perpendicular and not even secant. The first axis 8a and the second axis 10 may also be secant and not perpendicular. Said optronic sight 2 of FIGS. 3 and 4 differs from the optronic sight 2 presented with reference to FIGS. 1 and 2 and in that, in the feedback control loop 34 according to the present disclosure, at the input of the corrector K, we now find not only the feedback control error ε.sub.k which depends on the sampled measurement y.sub.mk of the angular data but also the fundamental frequency .sub.vk, varying in real-time, of the disturbing vibrations γ.sub.vib. Hence, this new adaptive corrector K(.sub.vk) 26 is calculated in order to compensate for the disturbing vibration γ.sub.vib (f.sub.v) whose fundamental frequency f.sub.v varies over time. For this purpose, means for continuously measuring the acceleration 28 of the aiming module according to the three axes 8a, 8b, 8c of an orthogonal reference frame in the space. These means for continuously measuring the acceleration comprise an accelerometer 28. The transfer function of the accelerometer H.sub.accelero allows accounting for the dynamics of said accelerometer. After passing through an Analogue-to-Digital Converter, the fundamental frequency .sub.vk associated with the vibratory disturbances γ.sub.vib is estimated in real-time. The detection means 32 of the fundamental frequency .sub.vk is based on two possible techniques: either it is calculated by Fast Fourier Transform, or by a phase-locked loop.

[0032] Phase-locked loops conventionally consist of a phase comparator, a loop filter, a voltage-controlled oscillator and a possible frequency divider.

[0033] As regards the calculations operated by the adaptive corrector K(.sub.vk), three techniques can be used: either by using a Linear Parameter Variant (LPV) control, or by means of a symbol corrector, or by a combination of its two types of correctors (LPV and symbol).

[0034] In the case of an LPV control corrector, a minimum state representation of the system K(.sub.vk) is designated by (A, B, C, D) with Aϵ.sup.n×n, Bϵ.sup.n×1, Cϵ.sup.1×n and Dϵ. . . The software implementation in the form of a state of the adaptive corrector K(.sub.vk) is done according to the following relationship:

[00002]$\{\begin{array}{c}{x}_{k+1}=A\left({\hat{f}}_{\mathrm{vk}}\right)x_k+B\left({\hat{f}}_{\mathrm{vk}}\right){\epsilon }_k\\ u_k=C\left({\hat{f}}_{\mathrm{vk}}\right)x_k+D\left({\hat{f}}_{\mathrm{vk}}\right){\epsilon }_k\end{array}$$f_{\min }\le {\hat{f}}_{\mathrm{vk}}\le f_{\max }$

where x.sub.kϵ.sup.n is the state variable of the adaptive corrector, ε.sub.k is the feedback control error at the input of the adaptive corrector, u.sub.k is the digital motor control calculated by the adaptive corrector (output of the adaptive corrector), f.sub.min and f.sub.max are two frequencies limiting the fundamental frequency in real-time .sub.vk of the disturbing vibrations γ.sub.vib. The state matrices (A, B, C, D) are .sub.vk affine and are written in the form:

A(.sub.vk)=A.sub.0+.sub.vkA.sub.1

B(.sub.vk)=B.sub.0+.sub.vkB.sub.1

C(.sub.vk)=C.sub.0+.sub.vkC.sub.1

D(.sub.vk)=D.sub.0+.sub.vkD.sub.1

where A.sub.0, B.sub.0, C.sub.0, D.sub.0, A.sub.1, B.sub.1, C.sub.1, D.sub.1 designate matrix gains which are the parameters saved in the memory of software that implements said adaptive corrector K(.sub.vk).

[0035] Thus, the adaptive corrector K(.sub.vk) varies according to the fundamental frequency of the spectrum of the lines of the disturbing vibrations γ.sub.vib (f.sub.v), while guaranteeing the stability of the feedback control loop. This adaptive corrector K(.sub.vk) allows automatically adapting in real-time (without having to recalculate the entire corrector unlike the prior art) the frequency of the selector filter to be used without any risk of instability, saturation or degradation of the robustness of the feedback control.