Method for generating a horizontal path avoiding dangerous zones for an aircraft

• US 6,424,889 B1
• Filed: 10/12/2000
• Issued: 07/23/2002
• Est. Priority Date: 02/12/1999
• Status: Expired due to Term

• Current Assignee: Thomson-Csf Sextant
• Original Assignee: Thomson-Csf Sextant
• Inventors: Inglese, Fabien, Bonhoure, Fabienne
• Primary Examiner(s): LOUIS JACQUES, JACQUES H
• Application Number:
  US09/646,917
• Time in Patent Office: 649 Days
• Field of Search: 701/3, 701/13, 701/14, 701/16, 701/200, 701/207, 701/209, 701/120, 701/121, 701/122, 701/300, 701/301, 340/945, 340/947, 340/948, 340/961, 244/75.R, 244/76.R, 244/175, 244/183
• US Class Current: 701/3
• CPC Class Codes: G05D 1/0202 specially adapted to aircraft
• CPC Class Codes: G08G 5/006 in accordance with predefined flight zones, e.g. to avoid prohibited zones

Abstract

A method for generating a horizontal path for the avoidance of danger zones for an aircraft. The method models the contours of each danger zone by a succession of segments demarcated by points. The method determines two homing circles and two capture circles passing respectively through the initial point and final point which are tangential respectively to the initial route and to the final route and have respectively the initial and final turning radius. The method also determines tangents both to the homing circles or the capture circles and to the contour of each danger zone. Among these tangents, a pair of tangents to a homing circle and to a capture circle are selected, defining a path skeleton connecting a homing circle to a capture circle without meeting a danger zone. And, an automatically controllable evasion path that lies on the previously defined path skeleton is then determined.

Claims

1. A method for generating a horizontal path of danger zone avoidance between two obligatory points of passage, one called an initial point and the other called a final point, that complies with constraints of approach, route or course, turning radius at the obligatory points of passage, and avoidance of a field of danger zones, each demarcated by contours, the method comprising the steps of:

modeling contours of each danger zone by a succession of segments demarcated by a plurality of geographical points;

determining characteristics of a first homing circle and a second homing circle, passing through the initial point, that are tangential to an initial route and have a radius corresponding to that of an initial turn, the first and second homing circles having directional senses of travel that are in reverse to each other, determined by the directional sense of the initial route;

determining characteristics of a first capture circle and a second capture circle passing through the final point, that are tangential to a final route and have a radius corresponding to a final turn, the first and second capture circles having directional senses of travel that are in reverse to each other, determined by the directional sense of the final route;

determining characteristics of tangents both to the homing circles and substantially to the contour of each danger zone and tangents both to the capture circles and to the contour of each danger zone;

selecting, among the previously determined tangents, a pair of tangents that intersect, comprising a tangent to one of the homing circles and a tangent to one of the capture circles, the pair of tangents defining a path skeleton connecting a homing circle to a capture circle without penetrating a danger zone;

determining an automatically controllable avoidance path that lies on the previously defined path skeleton; and

following the avoidance path with an aircraft.

2. The method according to claim 1, further comprising optimizing the avoidance path by adding an intermediate path segment between the routes of the previously selected pair of tangents.

3. The method according to claim 1, wherein circles of equiprobability of danger are centered on the plurality of geographical points demarcating the contour segments of the danger zones, the diameter of these circles corresponding to a fineness of meshing of terrain, the tangents to the danger zones being tangential to these circles.

4. The method according to claim 1, further comprising preselecting danger zones to be taken into account for the computation of an avoidance path, by selecting all danger zones that have points of definition of their contour located in a disk centered on the middle of the segment demarcated by the initial point and the final point, and including these points.

5. The method according to claim 1, wherein prior to selecting the pair of tangents defining the path skeleton, the method further comprises:

determining possible points of intersection between the previously determined tangents and the danger zones; and

eliminating tangents that go through a danger zone between their points of tangency to a danger zone and to a homing or capture circle, each of the non-eliminated circles being limited to a half line whose point of origin is its point of tangency to a homing or capture circle and extending from its point of tangency to a danger zone, this half line being reduced to a straight line segment extending from this point of origin, and being located outside any danger zone.

6. The method according to claim 5, wherein selecting a pair of tangents comprises:

locating points of intersection between the tangents reduced to half lines or segments, coming from homing circles and capture circles, respectively, each point of intersection found corresponding to a pair of tangents that defines a possible path skeleton; and

selecting, among all the pairs of tangents corresponding to the located points of intersections, that pair of tangents which leads to the shortest path.

7. The method according to claim 1, wherein if the determined avoidance path has a length exceeding a certain threshold that is predetermined in relation to the length of the initial path without danger zones, then the method further comprises determining an avoidance path that penetrates the interior of the field of danger zones without going through a danger zone.

8. The method according to claim 7, wherein determining an avoidance path that penetrates the interior of the field of the danger zones comprises:

selecting a pair of tangents, tangential to a homing circle and to a capture circle, respectively, comprising up to two tangents of the segment type penetrating as far as possible into the field of danger zones, if they exist, or, if necessary, of the half-line type which corresponds to a minimum angle of diversion from the initial route if it is a tangent to a homing circle or final route if it is a tangent to a capture circle;

determining a segment that is tangential to the danger zones on which the tangents of the selected pair lie, and demarcated by the points of intersection with these tangents; and

determining an avoidance path lying on the path skeleton demarcated by the selected pair of tangents and the previously determined tangent segment.

9. The method according to claim 8, wherein determining a segment tangential to two danger zones comprises:

selecting from among all straight lines connecting two respective points of two danger zones, two straight lines respectively having a minimum and a maximum route angle; and

selecting, from these two straight lines, a straight line that meets the previously selected tangents between their respective points of tangency to the two danger zones.

10. The method according to claim 8, wherein determining a segment tangential to two danger zones comprises:

selecting four straight lines connecting two respective points of the two danger zones, but not penetrating the danger zones; and

selecting one of these four straight lines that meets the previously selected tangents between their respective points of tangency to the homing circles and capture circles.

11. The method according to claim 1, wherein determining an avoidance path from a previously obtained path skeleton, comprising two or three segments, includes determining turning phases, by placing, in the vicinity of each junction point of two segments of the path skeleton, a turning circle with a predetermined turning radius tangential to these two segments.

12. The method according to claim 11, wherein, if an arc of a turning circle goes through a danger zone, the method comprises:

placing a new turning circle centered on the junction point between the two path skeleton segments; and

computing new avoidance path segments tangential to the new turning circle.