Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Aeronautical vehicle
Reexamination Certificate
1998-12-30
2001-01-09
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Aeronautical vehicle
C701S120000, C701S226000, C701S301000, C701S201000, C244S075100
Reexamination Certificate
active
06173219
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for the automatic piloting of a vehicle allowing the lateral avoidance of a fixed zone, for example a zone which it is forbidden to traverse.
2. Discussion of the Background
It applies in particular, but not exclusively, to the automatic piloting of an aerodyne whose initially planned route traverses a fixed zone with predefined contours which must be bypassed, while entry thereto is prohibited.
Such a situation occurs for example when, during the flight, the pilot receives a message prohibiting him from overflying a zone situated on his route. Such cases arise in particular when there is a prohibition to overfly a zone of air space, such as a military zone or a state.
Such information is, for example, received by the aerodyne by way of a device for transmitting digital data, for example a Data-Link, and has been sent by a ground station. The contours of the zone to be avoided figure within the on-board documentation, or else are transmitted by the ground station.
Currently, it is up to the pilot to handle the problem manually, by carrying out avoidance within sight of the zone, these operations having to take account of a considerable number of parameters, and in particular, of the regulations in force within the air space traversed, of the performance of the aerodyne, and of the weight of fuel in its tanks. Moreover, it may happen that the pilot receives such information only a very short time before entering the prohibited zone, and in many cases, this time is insufficient to enable him to take into account all the necessary parameters for determining the best avoidance trajectory.
SUMMARY OF THE INVENTION
The objective of the present invention is to eliminate these drawbacks. It is also aimed at determining the new route to be followed, while reducing as far as possible the distance to be travelled. For this purpose, it proposes a method for the automatic piloting of a vehicle for the lateral avoidance of a fixed zone.
The method according to the invention is characterized in that it comprises the following steps in succession:
the modelling of the contour of the zone to be avoided by a convex polygonal shape, by approximating the contour of the zone by a succession of segments, and eliminating the points of concavity and the excessively short segments,
the locating of the planned route with respect to the modelled zone,
the computation of port and starboard sections of route for exit and for return to the planned route, forming a predetermined angle with the latter and meeting up with the corner point of the polygonal shape closest to the planned route, so as to obtain two avoidance routes, port and starboard, formed by the exit and return sections of route and by the portions of the modelled contour respectively connecting the port and starboard exit and return transition sections of route, and
the selection of one of the two avoidance routes, port or starboard as a function of a predetermined criterion.
By virtue of these provisions, the pilot is completely unburdened of the job of modifying the flight plan and the piloting of the aerodyne with a view to avoiding the prohibited zone. Furthermore, the new route has been optimized by reducing as far as possible the distance to be travelled.
The present invention also relates to an optimized method for changing heading in order to bypass the prohibited zone modelled by a convex polygonal shape, that is to say, with compulsory overflying of the change of heading point and prohibition to enter the zone inside the turn.
Currently, these heading changes are made with a predetermined constant turning radius, for example one which depends on the speed of the aerodyne, in such a way as to retain a constant angle of roll. To comply with a predetermined turning radius, it is therefore necessary to commence the turn at the moment at which the transit point is overflown, in which case the aerodyne will, after overflying the transit point, lie outside the planned turn and will then have to follow a trajectory intended to meet up with the initially planned route.
It transpires, as represented in
FIG. 4
, that during its change of heading &Dgr;
104
, at the moment at which the transit point is overflown, the aerodyne strays significantly from the planned route R
1
, R
2
, and is even a relatively large distance d from it, which on the one hand causes a relatively large lengthening of the trajectory and on the other hand is undesirable in relation to surveillance and air control (compliance with variable lateral width margins).
To eliminate these drawbacks, the piloting method according to the invention comprises, at each corner point of the convex polygonal contour of the zone to be avoided, the computation and following by the vehicle of a curved change of heading trajectory passing through the said corner point, whose turning centre lies on the interior bisector of the angle formed by the two rectilinear portions of route which meet up at the corner point.
Such a change of heading trajectory offers numerous advantages by comparison with the trajectory of the prior art illustrated by FIG.
4
. This is because it makes it possible to save several seconds (up to 35 seconds or 4.5 nautical miles for a 90-degree turn). It deviates less from the planned route defined by the rectilinear sections of route (less than 30% of the deviation incurred by the conventional transition trajectory), this being of considerable benefit in respect of surveillance and air control. It also carries less risk of culminating in a linked succession of turns which criss-cross if the segments of route are short.
Moreover, if this change of heading trajectory is compared with the conventional trajectory which consists of a tangent curve to the two portions of route, which is situated inside the turn, it is observed that the trajectory according to the invention deviates less from the portions of route than the conventional trajectory.
Advantageously, the method according to the invention comprises the computation and following of two portions of curved linking trajectory, respectively between the first portion of route and the change of heading trajectory, and between the latter and the second portion of route, these two portions of linking trajectory having the same radius of curvature as that of the change of heading trajectory, and being tangent to the latter and to the two portions of route respectively.
REFERENCES:
patent: 5555175 (1996-09-01), D'orso
patent: 5581250 (1996-12-01), Khvilivitzky
patent: 5838262 (1998-11-01), Kershner et al.
patent: 5872526 (1999-02-01), Tognazzini
patent: 0 381 178 A1 (1990-08-01), None
patent: WO 95/19547 (1995-07-01), None
Arthur Gertrude
Cuchlinski Jr. William A.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sextant Avionique
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