Method for working out an avoidance path in the horizontal plane for an aircraft to resolve a traffic conflict

• US 6,546,338 B2
• Filed: 02/11/2002
• Issued: 04/08/2003
• Est. Priority Date: 06/09/2000
• Status: Expired due to Term

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Sainthuile, Gérard, Solans, Christophe
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): MANCHO, RONNIE M
• Application Number:
  US10/049,292
• Publication Number:
  US 20020152029A1
• Time in Patent Office: 421 Days
• Field of Search: 701/3, 701/4, 701/201, 701/301, 701/120, 701/302, 701/7, 340/961, 340/968, 340/971, 340/972, 340/825.69, 342/455, 342/32, 342/29, 342/30, 342/25
• US Class Current: 701/301
• CPC Class Codes: G01S 13/933 of aircraft or spacecraft
• CPC Class Codes: G08G 5/045 Navigation or guidance aids, e.g. determination of anti-collision manoeuvers radar or analogous systems specially adapted for anti-collision between aircraft G01S13/933

Abstract

The preparation of an avoidance path in the horizontal plane so that an aircraft can resolve a conflict of routes with another aircraft that entails a risk of collision within 5 to 10 minutes. This avoidance path minimizes the negative effects of the resultant route diversion on the flight plan of the aircraft. A method prepares an avoidance path with two parts. The first part is an evasive part with an initial heading such that the threatening aircraft takes a path, in relation to the threatened aircraft, that is tangential, on one side or the other, to the edges of the angle at which the threatening aircraft perceives a circle of protection plotted around the threatened aircraft. The radius of this circle of protection is equal to a minimum permissible separation distance. The second part of the evasive path is that of homing in on the initial route. This method of preparing an avoidance path can be implemented by a flight management computer. Once the avoidance path has been accepted by the aircraft crew, the flight management computer ensures that the avoidance path is followed by the automatic pilot.

Claims

1. Method for preparation of an avoidance path in a horizontal plane, for a first aircraft following an initial route, to resolve a conflict of traffic with a second aircraft following a second route that may be identical to the first route, based on knowledge (a) of a minimum safety distance S to be maintained between the first and second aircraft, (b) of current positions X₁ and X₂ of the first and second aircraft, and (c) of horizontal speed vectors {right arrow over (V 

)}₁ and {right arrow over (V 

)}₂ of the first and second aircraft, said method comprising;

determining a horizontal speed vector {right arrow over (V 

)}_rel of the second aircraft relative to the first aircraft;

determining, in the horizontal plane, a circle of protection around the first aircraft with the minimum safety distance as its radius;

testing an intersection of a straight line bearing the horizontal speed vector {right arrow over (V 

)}hd rel of the second aircraft with respect to the first aircraft, with the circle of protection of the first aircraft;

further comprising, in an event the intersection of the circle of protection of the first aircraft by the horizontal speed vector {right arrow over (V 

)}_rel of the second aircraft relative to the first aircraft, implying a risk of collision, tests affirmative;

determining an angle {right arrow over (α

 

)}_b-{right arrow over (α

 

)}_c at which the second aircraft perceives the circle of protection of the first aircraft;

determining a start-of-avoidance-maneuver point located on the initial route of the first aircraft and shifted downline from the current position X₁ of the first aircraft;

determining at least one value of heading angle {right arrow over (Θ

 

)}_1b and/or {right arrow over (Θ

 

)}_1c to be followed by the first aircraft, without changing a horizontal speed modulus, to bring the horizontal speed vector {right arrow over (V 

)}_rel of the second aircraft relative to the first aircraft at most on one of sides {right arrow over (X 

)}₂b, {right arrow over (X 

)}₂c of the angle at which the second aircraft perceives the circle of protection of the first aircraft; and

determining at least one collision-risk avoidance path for the first aircraft comprising a first evasive path constituted by a rectilinear segment having the start-of-avoidance-maneuver point as its point of origin, one of new values of the obtained heading angle {right arrow over (Θ

 

)}_1b or {right arrow over (Θ

 

)}_1c as its heading and having, as its end, a rotating point chosen beyond a point where the separation distance between the first and second aircraft passes through a minimum value equal to a minimum safety distance, and, beyond the rotating point, a second homing path to the initial route.

2. Method according to claim 1, wherein the determining at least one new value of heading angle comprises:

comparatively testing an oriented angle existing between the horizontal speed vector {right arrow over (V 

)}₂ of the second aircraft and the side {right arrow over (X 

)}₂b of the sides {right arrow over (X 

)}₂b, {right arrow over (X 

)}₂c of the angle at which the second aircraft perceives the circle of protection of the first aircraft, whose orientation is at a greatest distance from that of the horizontal speed vector {right arrow over (V 

)}₂ of the second aircraft;

3. Method according to claim 1, wherein, if more than one new value of heading angle {right arrow over (Θ

 

)}_1b and {right arrow over (Θ

 

)}_1c to be followed by the first aircraft, without changing its horizontal speed modulus to bring the horizontal speed vector {right arrow over (V 

)}_rel of the second aircraft relative to the first aircraft to one of the sides {right arrow over (X 

)}₂b, {right arrow over (X 

)}₂c of the angle at which the second aircraft perceives the circle of protection of the first aircraft, has been determined during the determining at least one new value of heading angle, the step for determining at least one avoidance path includes determining two avoidance paths, one avoidance path for each of the two new values of heading angle {right arrow over (Θ

 

)}_1b and {right arrow over (Θ

 

)}_1c.

4. Method according to claim 1, wherein, when the determining at least one avoidance path leads to determining more than one avoidance path, the method further comprises selecting the avoidance path to be implemented, including making a choice, from among the avoidance paths determined, of the path that minimizes a lengthening of the initial route of the first aircraft.

5. Method according to claim 1, wherein the at least one avoidance path determined during the determining at least one avoidance path comprises a second homing part for homing into the initial route, starting, from a rotating point marking an end of a first evasive part of the at least one avoidance path, with a rectilinear segment following a new heading which, with respect to a heading of the initial route, has an angular divergence opposite to that of the rectilinear segment of the first evasive part of the at least one avoidance path.

6. Method according to claim 5, wherein the rotating point that makes a transition, within said avoidance part, between an end of the rectilinear segment of the first evasive part and the rectilinear segment staffing a second homing part of the initial route, is chosen, on the rectilinear segment of the first evasive part, so that the rotating point is sufficiently distant from a point where a separation distance between the first and second aircraft passes through a minimum distance equal to the minimum safety distance so that the separation distance between the first and second aircraft does not go below the minimum safety distance, by the first aircraft, on the rectilinear segment starting the second homing part of the at least one avoidance path.

7. Method according to claim 1, wherein a modulus of half-angle ∥

{right arrow over (α

)}_b∥

or ∥

{right arrow over (α

)}_c∥

at which the second aircraft perceives the circle of protection of the first aircraft is deduced from relationship;

$<br><br>\stackrel{\to <br><br>}{{\mathrm{\alpha <br><br>}}_b}<br><br>=<br><br>\stackrel{\to <br><br>}{{\mathrm{\alpha <br><br>}}_c}<br><br>=\arcsin <br><br>\left(\frac{S}{<br><br>\stackrel{\to <br><br>}{X_1<br><br>X_2}<br><br>}\right).$

8. Method according to claim 1, wherein the determining of a new value of heading angle {right arrow over (Θ

 

)}_1j be followed by the first aircraft, without changing a horizontal speed modulus, to bring the horizontal speed vector {right arrow over (V 

)}_rel of the second aircraft relative to the first aircraft on one of the sides {right arrow over (X 

)}₂b or {right arrow over (X 

)}₂c, as an envisaged side {right arrow over (X 

)}₂j, of the angle at which the second aircraft perceives the circle of protection of the first aircraft, is obtained by application of an angular relationship that links the new value of heading angle {right arrow over (Θ

 

)}_1j to;

a heading {right arrow over (Ψ

)} of an oriented straight line linking the position X₁ of the first aircraft to the position X₂ of the second aircraft,

a half-angle {right arrow over (α

)}_i at which the second aircraft perceives the circle of protection of the first aircraft, oriented from a bisector of the angle at which the second aircraft perceives the circle of protection of the first aircraft constituted by oriented straight line {right arrow over (X₂X₁ 

)} linking the position X₂ of the second aircraft to the position X₁ of the first aircraft, towards the envisaged side {right arrow over (x 

)}₂j of the angle at which the second aircraft perceives the circle of protection of the first aircraft, and

an oriented angle {right arrow over (γ

 

)}_j made by the envisaged side {right arrow over (X 

)}₂j of the angle at which the second aircraft perceives the circle of protection of the first aircraft, with a new vector {right arrow over (V 

)}₁^j sought for a horizontal speed of the first aircraft to eliminate a risk of collision,

this angular relationship being expressed by relationship;

9. Method according to claim 5, wherein the rotating point linking the rectilinear segment of the first evasive part and the rectilinear starting segment of the second homing part of an avoidance trajectory is chosen to be reached by the first aircraft after a minimum period of time t_cpa equal to:

$t_{\mathrm{cpa}}=-\left(\frac{\left(\stackrel{\to <br><br>}{X_1<br><br>X_2}\right)<br><br>\left(\stackrel{\to <br><br>}{V_2}-\stackrel{\to <br><br>}{V_1^n}\right)}{{<br><br>\stackrel{\to <br><br>}{V_2}-\stackrel{\to <br><br>}{V_1^n}<br><br>}^2}\right)$

{right arrow over (V 

)}₁ⁿ being a horizontal speed vector of the first aircraft when it travels through the first evasive part of its avoidance trajectory.

10. Method according to claim 6, wherein the rotating point linking the rectilinear segment of the first evasive part and the rectilinear starting segment of the second homing part of an avoidance trajectory is chosen on the rectilinear part of the first evasive part, beyond a point where the separation distance between the first and second aircraft passes through a minimum distance equal to the minimum safety distance, and whose position is determined by distance D_CPA1 from a point marking a start of the at least one avoidance path drawn from relationship:

$D_{\mathrm{CPA1}}=t_{\mathrm{cpa}}\times <br><br><br><br>\stackrel{\to <br><br>}{V_1}<br><br>$$\text{with;<br><br>}$$t_{\mathrm{cpa}}=-\left(\frac{\left(\stackrel{\to <br><br>}{X_1<br><br>X_2}\right)<br><br>\left(\stackrel{\to <br><br>}{V_2}-\stackrel{\to <br><br>}{V_1^n}\right)}{{<br><br>\stackrel{\to <br><br>}{V_2}-\stackrel{\to <br><br>}{V_1^n}<br><br>}^2}\right)$

{right arrow over (V 

)}₁ⁿ being a horizontal speed vector of the first aircraft following the rectilinear segment of the first evasive part of its avoidance trajectory.

11. Method according to claim 9, wherein the rotating point linking the rectilinear segment of the first evasive part and the rectilinear starting segment of the second homing part of an avoidance trajectory is chosen on the rectilinear segment of the first evasive part, beyond the point where the separation distance between the two aircraft passes through a minimum distance equal to the minimum safety distance, at a distance D_PT from this point drawn from relationship:

$t_{\mathrm{PT}}=S\times <br><br>\tan <br><br>\left(\frac{\stackrel{\to <br><br>}{{\mathrm{\chi <br><br>}}_{\mathrm{EOM}}}-\left(\stackrel{\to <br><br>}{{\mathrm{\psi <br><br>}}_{\mathrm{SOM}}}+\mathrm{\pi <br><br>}+\stackrel{\to <br><br>}{{\mathrm{\alpha <br><br>}}_{\mathrm{SOM}}}\right)}{2}\right)\times <br><br>\frac{1}{<br><br>\stackrel{\to <br><br>}{V_2}-\stackrel{\to <br><br>}{V_{1<br><br>\mathrm{SOM}}}<br><br>}$

wherein;

χ

{right arrow over (_E 

)}_OM is a heading of a relative speed vector of the second aircraft with respect to the first aircraft when the first aircraft embarks on the rectilinear segment starting the second evasive part of its avoidance trajectory,

Ψ

{right arrow over (_S 

)}_OM is a heading of the oriented segment linking a position of the first aircraft with that of the second aircraft when the first aircraft is at the starting point of the first evasive part of its avoidance trajectory, after having adopted its heading,

α

{right arrow over (_S 

)}_OM is a half-angle at which the second aircraft perceives the circle of protection of the first aircraft while the first aircraft is at the starting point of the first evasive part of its avoidance path, this half-angle being oriented from the oriented segment, linking the position of the second aircraft to that of the first aircraft, towards a side of the angle at which the second aircraft perceives the circle of protection of the first aircraft, adopted to obtain passage of a trajectory of the second aircraft relative to the first aircraft, when the first aircraft describes the rectilinear segment of the first evasive part of its avoidance trajectory, and

V{right arrow over (₁ 

)}_SOM is a horizontal speed vector adopted by the first aircraft when it follows the rectilinear segment starting the second homing part of its avoidance trajectory.