Aeronautics and astronautics – Missile stabilization or trajectory control – Automatic guidance
Reexamination Certificate
2000-03-28
2002-03-26
Gregory, Bernarr E. (Department: 3662)
Aeronautics and astronautics
Missile stabilization or trajectory control
Automatic guidance
C244S003160, C244S003210
Reexamination Certificate
active
06360986
ABSTRACT:
The present invention relates to a process and a device for guiding a flying craft, in particular a missile, onto a target.
More precisely, the said process and device are intended for implementing autoguidance, that is to say guidance which can be carried out solely with the aid of the information available on the said flying craft.
In a known manner, for a missile, in particular an air-to-ground missile, such autoguidance is implemented in the terminal phase of the guidance, on approach to the target.
Generally, the said autoguidance is carried out with the aid of information supplied by a seeker head, and in particular of the information relating to the said target which is situated in a field of view of the said seeker head. To this end, the line of sight of the seeker head is continually servocontrolled.
In a known manner, such servocontrol exhibits different objects, depending on the guidance phase considered, and consisting:
before “lock-on”, that is to say before actual detection of the target, in pointing the said seeker head within the assumed environment of the said target; and
after “lock-on”, in maintaining the target within the measurement field (restricted by design) of the said seeker head and in tracking the said target.
The guidance commands for the said flying craft are then deduced, in a known manner, by using the signals supplied by the seeker head tracking the target, the said guidance commands being implemented by the steering of the craft carrying out the commanded maneuvers in terms of pitch and yaw, possibly with roll servocontrol, either to keep the roll of the craft constant, or to distribute the aerodynamic load by performing an aerodynamic roll check of the craft so as to improve the aerodynamic characteristics such as the useable load factor, the load on the steering actuators, the roll torques induced, etc.
This standard solution of autoguidance nevertheless has a number of drawbacks. In particular, it is complex and expensive, since it requires, in a known manner, for its implementation, in addition to the seeker head detection system, several other expensive measurement and processing devices, in particular:
mechanical devices for rendering the line of sight moveable, with mobility according to at least two or three axes for guidance in space. These mechanical devices comprise, for example, articulations with a gimbal mounting and motorization of each axis;
measuring equipment and associated electronic means for monitoring line of sight servocontrol loops.
To remedy these drawbacks, it is known practice to use a detector, for example of the infrared or optical detection type, in particular laser detection, which is rigidly tied to the flying craft and which carries out the overall function of detection (location and identification) of the target.
However, such an implementation, which exhibits undeniable advantages relative to the aforesaid standard solution, requires a detector exhibiting a measurement field of considerable size so as, the flying craft being guided on a trajectory toward the target:
before lock-on, to have the target in the said measurement field, whilst taking into account, not only errors in objective designation and guidance of the craft, but also incidences of the said craft due to the disturbances of the environment (wind, effect of gravity, etc.) and to the achieving of the load factor; and
after lock-on, continuing to maintain the target in the said measurement field.
Of course, the requirement of a considerable size for the field of measurement of the detector entails drawbacks, in particular in terms of cost, bulk, weight, etc.
The object of the present invention is to remedy these drawbacks and in particular to reduce the size of the field of measurement of the detector whilst remaining compatible with the effectiveness of guidance. It relates to a process for guiding a flying craft onto a target, the said guiding exhibiting various successive phases, including a terminal phase for which at least the guidance is carried out with the aid of measurements performed by a detector mounted on the said flying craft and pointed with its line of sight toward the said target so that a projection of the latter is situated on a field of measurement of the said detector, as well as with the aid of information, in particular navigation and inertial information, emanating from information sources mounted on the said flying craft.
To this end, according to the invention, the said process is noteworthy in that at least in the said terminal phase, attitudes of the said flying craft are controlled in such a way as to center the projection of the target with respect to a first direction of the said measurement field, in that the line of sight of the said detector is moveable about a second direction of the said field of measurement, which is different from the said first direction, and in that at least in the said terminal phase, the mobility of the line of sight of the said detector is controlled in such a way as to center the said projection of the target with respect to the said second direction.
Thus, since by virtue of the invention the projection of the target onto the field of measurement of the detector is automatically centered with respect to the said first and second directions which are orthogonal, respectively by controlling the attitudes of the flying craft and the mobility of the said line of sight, the said measurement field may exhibit a reduced size so that the said detector makes it possible to remedy the aforesaid drawbacks (cost, bulk, weight, etc.).
Advantageously, at least in the said terminal phase, the relative motion between the flying craft and the target is estimated, thus making it possible in particular to estimate the kinematics of the target with respect to the flying craft and thus to implement the process in accordance with the invention even:
when the projection of the target leaves the field of measurement of the detector; and even
in flight phases for which such a projection does not exist or does not yet exist.
Moreover, advantageously, at least in the said terminal phase, attitudes of the said flying craft are controlled in such a way as to distribute the aerodynamic load over axes tied to the said flying craft.
Such a distributing of the aerodynamic load exhibits several advantages and makes it possible in particular:
to relieve the actuators of the steering control surfaces of the flying craft; and
to increase the total steerable domain of incidence.
Moreover, advantageously, the roll of the flying craft is controlled as attitude of the latter.
Thus, since the guidance of the flying craft is carried out in a standard manner in terms of pitch and yaw, the (roll) control in accordance with the invention with a view to the centering and, as appropriate, the distributing of the aerodynamic load is compatible with the effectiveness of the guidance.
To determine a roll control command, use is preferably made for this purpose of the deviation measurement values determined at least from certain of the following information:
information relating to measurements performed by the said detector;
inertial information and navigational information; and
information relating to the orientation of the line of sight of the detector, with respect to the flying craft.
In an advantageous mode of implementation, to simultaneously carry out a distributing of the aerodynamic load over axes tied to the flying craft and the centering of the projection of the target, the roll is controlled on the basis of a roll variation command &Dgr;&phgr;co which satisfies the relation:
Δ
ϕ
co
=
{
ΔΔϕ
coA
,
if
the
value
Δϕ
coA
is
defined
between
values
Δϕ
co1
and
Δϕ
co2
·
Δϕ
Delmau Cyril
Larcher Eric
Aerospatiale Matra
Gregory Bernarr E.
Stevens Davis Miller & Mosher LLP
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