Aeronautics and astronautics – Missile stabilization or trajectory control – Automatic guidance
Reexamination Certificate
1998-11-20
2001-01-30
Gregory, Bernarr E. (Department: 3662)
Aeronautics and astronautics
Missile stabilization or trajectory control
Automatic guidance
C244S003150
Reexamination Certificate
active
06179246
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a seeker head for target tracking missiles having an image resolving seeker being gimbal suspended in a seeker gimbal assembly and adapted to be aligned to a target by target deviation signals, and inertial sensors,
Target tracking missiles are known having an image resolving sensor, e.g. in the form of a detector matrix having a two-dimensional array of detector elements. This seeker is gimbal suspended in a seeker gimbal assembly. Inertial sensors respond to the angular movements of the missile in inertial space. Torquers act on the gimbals of the seeker gimbal assembly and decouple the seeker from the thus determined angular movements of the missile. An image of an object scene is generated on the detector matrix. Target deviation data of a target located in the object scene, e.g. an enemy aircraft to be attacked, are generated by image processing of this image. The target deviation data represent the deviation of the target from an optical axis of the seeker. By means of these target deviation data the seeker tracks the target. From the tracking the angular rate of the line of sight is determined. From the angular rate of the line of sight, in turn, steering signals for the missile are derived. By means of a helmet visor a target recognized by the pilot is designated to the seeker. The missile is guided to this target in the described manner.
During air combats with close curves (“close-in-combat”) it is desirable to detect a target even at a large look angle of the seeker. However, the look angle of the seeker is, of course, limited by the design. During air combats with close curves, situations can arise, in which the target occurs under an angle of vision, which is larger than the maximum allowable look angle of the seeker. Then the target cannot be designated to the seeker head. During the further course of the curved flight, the angle of sight can be reduced to a value below the maximum allowable look angle. Then the target can be designated to the seeker head and the missile can be fired. The earlier this is made, the greater are the chances of hitting the target. If, however, the missile is fired, then it first has the tendency to align aerodynamically with the direction of the velocity vector of the missile. Then the angle of vision to the target can again exceed the maximum allowable look angle of the seeker, such that the target gets lost. The target can also be covered temporarily by clouds.
SUMMARY OF THE INVENTION
One of the objects of the present invention is hence to provide a seeker head for target tracking missiles such that, even when the target tracking is disturbed for a short time, the seeker is re-aligned to the target as soon as the disturbance ceases.
This object is achieved in that a virtual inertially stabilized reference coordinate system is defined from signals from the image resolving seeker and from the seeker gimbal assembly, the stabilized reference coordinate system having an axis pointing to said target, the stabilized reference coordinate system is caused to point to predicted target positions, in case of disturbance of the target-tracking function of the seeker, in accordance with the line of sight information (e.g. direction, angular rate, angular acceleration) of said reference coordinate system then present, and the seeker is aligned with the axis of the reference coordinate system, when the disturbance ceases, the signals from the seeker resuming the tracking function of the seeker again.
Thus, according to the invention, a reference coordinate system is permanently defined, the axis of which points to the target. This is a type of “virtual” seeker. Normally, this reference coordinate system follows the target in the same manner as the seeker tracks the target from the deviation data. If the tracking movement of the seeker to the target is deteriorated, e.g. when the seeker attains its maximum allowable look angle or when the seeker temporarily cannot “see” the target anymore due to clouds, the reference coordinate system tracks a predicted target position. The predicted target position is determined by a kind of extrapolation from the line of sight information determined immediately before the deterioration occurs. When the deterioration then ceases, that means, for example, that the target occurs under an angle of vision falling below the maximum allowable look angle again, the seeker is aligned with the reference coordinate system. Then the seeker again detects the target, which target has been lost for a short time in its field of view. Then the seeker again tracks the target exactly by means of the deviation data supplied by the image processing.
Further objects and features of the invention will be apparent to a person skilled in the art from the following specification of a preferred embodiment when read in conjunction with the appended claims.
REFERENCES:
patent: 5702068 (1997-12-01), Stoll et al.
patent: 28 41 748 C1 (1996-07-01), None
patent: 0 653 600 A1 (1994-10-01), None
patent: 0 714 013 A1 (1996-05-01), None
patent: 0 797 068 A2 (1997-09-01), None
patent: 2 632 072 (1985-08-01), None
Fisel Herbert
Hartmann Ulrich
Bodenseewerk Geratetechnik GmbH
Gregory Bernarr E.
McDermott & Will & Emery
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