WO2012126033A1

WO2012126033A1 - A system, method and computer program for assisting in the navigation of a vehicle

Info

Publication number: WO2012126033A1
Application number: PCT/AU2011/000329
Authority: WO
Inventors: Neale FULTON; Hoo-Nhon HUYNH
Original assignee: Commonwealth Scientific And Industrial Research Organisation
Priority date: 2011-03-23
Filing date: 2011-03-23
Publication date: 2012-09-27

Abstract

A method and system for assisting in the navigation of a first vehicle are disclosed. The method includes the steps of obtaining position and velocity information for the first vehicle (A) and position and velocity information for a second vehicle (B). The position and velocity information are used to calculate a non-allowed steering direction (504), being a direction which if taken by the first vehicle (A) may result in a collision with the second vehicle (B). Data indicative of the non-allowed steering direction are output to a visual display and/or an autopilot system.

Description

A SYSTEM, METHOD AND COMPUTER PROGRAM FOR ASSISTING. IN THE

NAVIGATION OF A VEHICLE

Field of the Invention

The present invention relates to a system, method and computer program for assisting in the navigation of a vehicle. Embodiments of the invention find particular, but not exclusive, use in the determination and display of a non-allowed steering direction representative of a direction that a vehicle should avoid to prevent a

collision. In particular, embodiments of the invention find particular use in the navigation of aircraft and ships and boats .

Background of the Invention

Since the advent of air travel, many methodologies and systems have been proposed to prevent mid-air

collisions between aircraft. In particular, it is well known to define a conceptual or virtual three-dimensional volume (e.g. a sphere or a cylinder) around each aircraft. The three-dimensional volume represents a zone or space into which other aircraft should not enter. To determine whether there is a high risk of collision, an observer determines whether the volume of one aircraft intersects, or will intersect, with the volume of another aircraft. If so, then the aircraft are required to take evasive action. In other words, such a methodology merely

requires that aircraft keep a minimum distance from each other, in three-dimensional space, at all times.

Such a methodology has enjoyed a reasonable amount of success in airspace that is monitored by a third party, such as an air traffic control tower with radar and other monitoring capabilities, but is of more limited value in unmanaged airspace in which pilots receive little or no ground-based separation assurance.

Moreover, the use of a simplistic methodology, such as defining a volume around an aircraft, can be

inefficient if the defined volume is too large; conversely if the volume is too small, the risk of a collision or other undesirable interaction may increase to an

unacceptable level .

There have been numerous attempts to develop

methodologies that warn aircraft of potential dangers, such as the presence of other aircraft within a defined volume of airspace.

One system, investigated by the National Aeronautical and Space Agency (NASA) of the US, uses a display that renders an avatar of the aircraft and also renders a line which represents a "threat vector" (i.e. a line

representing both the distance and direction of another aircraft at the point of closest approach) . Such a display is somewhat counterintuitive, as the line that represents the "threat vector" becomes smaller as another aircraft approaches. Indeed, at a point close to

collision, the line disappears from the screen. The pilot is therefore required to learn that the longer the line, the smaller the risk of a collision. Where there is no threat vector, it is not clear whether there are no other aircraft in the immediate vicinity, or whether the

aircraft are only moments away from a collision.

Accordingly, the use of a "threat vector" requires very specific training for pilots.

Another system, developed by the Delft University of Technology, provides a display that renders a ^velocity envelope" for nearby aircraft relative to an avatar that represents the aircraft. The velocity envelope represents a velocity area into which the aircraft velocity vector should not enter. This system is not altogether intuitive to a pilot, as it requires the pilot to understand the significance of the velocity envelope and to learn how to react to the velocity envelope as it changes over time.

In summary, prior art systems have suffered from a conceptual gap between the information rendered on a display and the more intuitive three-dimensional

understanding that a pilot has of their aircraft's position in a given airspace and of their ability to manoeuvre in that airspace .

Summary of the Invention

In a first aspect, the present invention provides a method for assisting in the navigation of a first- vehicle, comprising the steps of obtaining position and velocity information for the first vehicle and position and velocity information for a second vehicle; using the position and velocity information for the first and second vehicles to calculate a non-allowed steering direction, being a direction which if taken by the first vehicle may result in a collision with the second vehicle; and outputting data indicative of the non-allowed steering direction.

The step of calculating the non-allowed steering direction may include the step of identifying a location at which the vehicles would collide, assuming that the first vehicle maintains its current speed and the second vehicle maintains its current velocity.

The step of calculating the non-allowed steering direction may include the step of calculating a locus of points at which the first and second vehicles might collide.

Calculating the locus of points may include the steps of calculating the relative range between the first and second vehicles; calculating the ratio of the speeds of the first and second vehicles; and determining as the locus of points at least a segment of an Apollonius circle calculated in dependence upon the relative range and the ratio of the speeds of the first and second vehicles.

The step of calculating the non-allowed steering direction may include the step of determining a plane in which the locus of points lies.

The step of calculating the non-allowed steering direction may further includes identifying the point, I, at which the second vehicle will pass. through the locus of points, assuming it continues to travel with its current velocity.

Calculating the non-allowed steering direction may further include the step of calculating an aspect angle of the second vehicle.

The non-allowed steering direction may be determined to be a vector from the current location of the first vehicle to the point, I.

The method may further comprise the step of

calculating the time to point of closest approach, being the time from the- present moment to the time of collision if the first vehicle follows the non-allowed steering direction.

The method may further comprise visually displaying the non-allowed steering direction.

The method may further comprise visually displaying a reference mark representing the first vehicle; and - visually displaying a line extending from the reference mark, the line representing the non-allowed steering direction.

A mark indicating the location of point I may also be displayed.

The method may further comprise visually displaying a line indicating a steering direction which, if taken by the first vehicle, would result in the first vehicle passing the second vehicle with a minimum required

miss-distance.

The method may further comprise visually displaying a plurality of lines indicating respective steering

directions which, if taken by the first vehicle, would result in the first vehicle passing the second vehicle with respective minimum required miss-distances.

The plurality of lines may include at least a first line indicating a first steering direction which, if taken by the first vehicle would result in the first vehicle passing forward of the second vehicle and a second

steering direction which, if taken by the first vehicle would result in the first vehicle passing behind the second vehicle.

The first and second steering directions may relate to minimum required miss-distances which are unequal.

The method may further comprise identifying a plurality of second vehicles within a predefined region, and obtaining velocity and position information for each of the

plurality of second vehicles; and using the information to determine respective non-allowed steering directions for the first vehicle with respect to each of the plurality of second vehicles.

The method may comprise the further step of visually displaying at least a subset of the plurality of non-allowed steering directions.

The method may further comprise calculating a respective time to closest approach for each of the plurality of second vehicles.

The method may further comprise selecting a subset of the plurality of non-allowed steering directions for visual display in dependence upon the respective

calculated times to closest approach.

The subset may be selected to include those

non-allowed steering directions having the shortest times to closest approach.

The method may be iterated to update the non-allowed steering direction.

The data indicative of the non-allowed steering direction may be output to an autopilot system.

A second aspect of the invention provides a system for assisting in the navigation of a first vehicle, comprising an arrangement arranged to obtain position and velocity information for the first vehicle and position and velocity information for a second vehicle; a processor arranged to use . the position and velocity information for the first and second vehicles to calculate a non-allowed steering direction, being a direction which if taken by the first vehicle may result in a collision with the second vehicle; and an interface arranged to output data, indicative of the non-allowed steering direction.

The processor may be arranged to use the position and velocity information for the first and second vehicles to identify a location at. which the vehicles would collide, assuming that the first vehicle maintains its current speed and the second vehicle maintains its current

velocity.

The processor may be arranged to calculate a locus of points at which the first and second vehicles might collide .

The processor may be further arranged to calculate the relative range between the first and second vehicles and the ratio of the speeds of the first and second vehicles and to determine as the locus of points at least a segment of an Apollonius circle calculated in dependence upon the relative range and the ratio of the speeds of the first and second vehicles.

The processor may be arranged to determine a plane in which the locus of points lies.

The processor may further be arranged to identify the point, I, at which the second vehicle will pass through the locus of points, assuming it continues to travel with its current velocity.

The processor may further be arranged to calculate an aspect angle of the second vehicle.

The non-allowed steering direction may be determined by the processor as being a vector from the current location of the first vehicle to the point, I.

The processor may be adapted to calculate the time to point of closest approach, being the time from the present moment to the time of collision if the first vehicle follows the non-allowed steering direction.

The system may further include a display arranged to visually display the non-allowed steering direction. .

The display may be further arranged to display a reference mark representing the first vehicle, and a line extending from the reference mark, the line representing the non-allowed steering direction.

• The display may be further arranged to display a mark indicating the location of point I.

The display may be further arranged to display a line indicating a steering direction which, if taken by the first vehicle, would result in the first vehicle passing the second, vehicle with a minimum required miss-distance.

The display may be further arranged to display a plurality of lines indicating respective steering

The arrangement may be arranged to identify a plurality of second vehicles within a predefined region; to obtain velocity and position information for each of the plurality of second vehicles; and to use the

information to determine respective non-allowed steering directions for the first vehicle with respect to each of the plurality of second vehicles.

The display may further be arranged to display at least a subset of the plurality of non-allowed steering directions.

The processor may be further arranged to calculate a respective time to closest approach for each of the plurality of second vehicles.

The processor may also be arranged to select a subset of the plurality of non-allowed steering directions for visual display in dependence upon the respective calculated times to closest approach.

The processor may be arranged to select the subset to include those non-allowed steering directions having the shortest times to closest approach.

The processor may be arranged to calculate the non-allowed steering direction repeatedly to account .for movement of the vehicles.

The system may be arranged to output the data indicative of the non-allowed steering direction to an autopilot system. . .

In a third aspect, the invention provides a computer program including at least one instruction which, when executed on a computing system, is arranged to implement a method as set out above in connection with the first aspect.

A fourth aspect of the invention provides a computer readable medium including a computer program in accordance with the third aspect.

A fifth aspect of the invention provides a method of transmitting or receiving a data signal comprising at- least one encoded instruction in accordance with the computer program of the third aspect.

Detailed Description of the Drawings

Notwithstanding any other embodiments that may fall within the scope of the present invention, an embodiment of the present invention will now be described, by way of example only, with reference to the accompanying Figures, in which:

Figure 1 is a block diagram which illustrates the components of an example system in accordance with an embodiment of the invention; Figure 2 is a block diagram illustrating a computing system which may be used to carry out a method in

accordance with an embodiment of the invention;

Figure 3 is a plan view of an operational scenario in which embodiments of the invention find application;

' Figure 4 is a flow diagram illustrating a process flow in accordance with an embodiment of the present invention; and

Figures 5, 6 and 7 are illustrations of example interfaces used to display a non-allowed steering

direction in accordance with an embodiment of the present invention.

Detailed Description of an Embodiment

Referring to Figure 1, there is shown an example of a system which may be used to carry out a method (or execute a software application) in accordance with an embodiment of the present invention. The method comprises the steps of obtaining respective position and velocity information for at least two vehicles, using the information to calculate a non-allowed steering direction, and outputting data indicative of the non-allowed steering direction.

A non-allowed steering direction for a given vehicle is a direction which, if taken by that vehicle, may result in a collision.

The present embodiment will be described with reference to aircraft, airspace and air traffic control, but it will be understood that Other embodiments may be used in any situation where there is an inherent danger that vehicles may collide (such as shipping/boating applications) .

In this example embodiment, the method is implemented by a computing system, such as a flight management computer or a navigational system (such as a satellite navigation system) .

Referring in detail to Figure 1, there is a shown a schematic diagram of a system which in this embodiment is a flight computer 100. The flight computer includes a datalink device 102, for example in the form of an

Automatic Dependent Surveillance-Broadcast (ADS-B) device and a navigation device 104, for example in the form of a Global Positioning System (GPS) device. Information from these devices 102, 104 are provided to a flight computer processor 106, which calculates the non-allowed steering direction, which is then provided to an output means, such as a display 108.

Referring to Figure 2, there is shown a schematic diagram of an example flight computing system 200 (which is a more detailed example of flight system 100 of

Figure 1) . The computing system 200 comprises suitable components necessary to receive, store and execute appropriate computer instructions. In the present embodiment, the components include a processing unit 202, read-only memory (ROM) 204, random access memory (RAM) 206, and other devices such as a storage device in the form of a disk drive 208, input devices 210 such as a keyboard, keypad, joystick, trackball or any other suitable input device. In other embodiments, the storage device may instead be a solid state drive, an optical drive or any other suitable device . Multiple storage devices may be provided as required.

The system is in communication with at least one display 212 (equivalent. to display 108 in Figure 1) such as a liquid crystal display, a light emitting display, head-up display, panel -mounted display or any other suitable display. The system also includes communications links 214, arranged to receive data or instructions from one or more sources. The system 200 includes instructions stored in ROM 204, RAM 206 and/or storage device 208 for execution by the processing unit 202.

In another embodiment, the information relating to the non-allowed steering direction is additionally or alternatively passed to an autopilot system.

The system includes an operating system 220 residing in computer memory (e.g. ROM 204) , on a disk or other storage device which is arranged t6 store and allow the computer to run one or more software applications,

including the application described herein.

Operational Scenario

Before discussing an algorithm by which a non-allowed steering direction may be calculated, by way of overview/ an operational scenario will be outlined, with reference to Figure 3, in which the system may be used.

This example has been created to illustrate the process of solution. A person skilled in the art of creating navigation equations will recognise there are skills such as the correct interpretation of circular functions, expansion of determinants and transformation from one frame of reference to another that are required to fully implement this solution. This detail has not been included so as not to obscure the fundamental

solution strategy.

1. Consider a first aircraft A (for the purposes of this discussion, aircraft A is considered to be the aircraft in which the presently-disclosed navigation system is located) and a second aircraft B, known as an "intruder" aircraft, in such proximity as to be of operational concern. Aircraft A passes its position and velocity information to aircraft B (in a fully .

co-operative situation aircraft B will also transmit its position and velocity information to aircraft A) . On this basis a plan position display may be generated with features as shown in Figure 3.

2. On the basis of this information, aircraft A constructs the line of sight vector between the^' aircraft and can also construct an "Apollonius circle" that identifies all possible collision points for the given speed ratio of the aircraft. That is to say, the

Apollonius circle is the locus of the points in space that the aircraft could reach simultaneously by moving from their current location at their current speeds . Equations for the circle, its centre and its radius are given below. While the circle indicates the possible collision points, knowing the aspect angle, a , of aircraft B means that the specific collision point, I, can be calculated on the basis that aircraft B maintains its present velocity ^' vector. If it does not the calculations can be reiterated at a suitable update rate. Predictor lines are provided to the pilot or other crew of the aircraft A. The

Predictor lines are an extrapolation (prediction) of each aircraft's flightpath for a set time interval (e.g. 45s) .

3. With this information the pilot of A is in a position to plan a flight direction to avoid the point I. To facilitate this, in one embodiment, a range bar is placed on the Intruder's Predictor line to indicate where aircraft A will intercept aircraft B's Predictor line and the miss-distance that aircraft A would achieve if it maintained its current velocity vector direction.

4. The acceptable miss-distance (that is the smallest acceptable distance between the aircraft as they pass) can be less for an intercept that passes behind aircraft B than for one that passes in front in which the acceptable miss distance will be required to be

significantly higher. Another feature of this method is the ability to construct a cone of general cross section (it does not have to necessarily be of circular or elliptic cross section) with axis centred on the line AI that defines a cone of non-allowed steering directions determined with reference to a schema of acceptable miss-distances. The cone can be skewed about the line AI to provide protection for the required miss-distances along the Intruder's Predictor line before and after the Point I (the point I represents zero miss-distance) .

5. By inspection, it can be seen that if aircraft A passes · through the Apollonius circle then there can be two possible intercept points one for aircraft B

approaching aircraft A and one for aircraft A generally following aircraft B. In other words, the pilot of aircraft A (assumed in this example to be the faster aircraft) needs to be aware that if aircraft B manoeuvres in such a way that one of the potential conflicts is resolved, it may continue to manoeuvre so as another conflict may arise.

Referring to Figure 4, there is shown a flow chart generally denoted by numeral 400, which lists the steps performed by a software application (or in another embodiment, a hardware system) in accordance with an embodiment of the invention. At step 402, the method is arranged to obtain data prior to performing any

calculations.

The data collected in the present aircraft example are position and velocity data for the aircraft in which the system is located (the first aircraft) , obtained from the navigation device 104, and position and velocity information for a second aircraft, obtained from the datalink device 102 which is adapted to receive such information transmitted from other aircraft.

Given the position and velocity of the first and second aircraft, an algorithm commences at step 404, as described in further detail below, to determine a^' non-allowed steering direction of the first aircraft with respect to the second aircraft.

Theoretical Background and Outline of Algorithm

-With further reference to Figure 4, an algorithm for calculating the non-allowed steering direction will now be described, including specific calculations in connection with an example scenario.

For the purposes of illustrating the method of calculation, assume that the aircraft in which we are located (A) is the faster aircraft and that this aircraft occupies airspace i the same vicinity of a slower aircraft (B) . It will be clear to the skilled addressee that the algorithm discussed may be appropriately applied in situations where the opposite is true (i.e. where aircraft A is the slower aircraft) .

In the following discussion, for the purposes of clarity, the algorithm is separated out into discrete steps. In particular, the reception by own aircraft, A, of the position and velocity vectors of the intruder aircraft, B, are discussed in separate sequential steps. The skilled addressee will appreciate, however, that the various steps need not necessarily be performed in the order they are presented below. For example, in typical systems, aircraft transmit position and velocity

information automatically (i.e. without interrogation) and, for all practical purposes, in real-time via an ADS-B datalink system.

Compute Relative Range

Aircraft maintain their position in an Earth

coordinate system (geocentric-inertial frame) . The reference for each aircraft may be expressed as triplets of coordinates such as (latitude, longitude, altitude) or (North, East, Down) . Each of the position, P_{j t} and the velocity, K, , vectors of each aircraft are expressed as three-dimensional vectors in the frame of reference. On this basis, and in the Earth frame of reference ( _E,y_E,z_E) , the following calculations are performed

1. Own aircraft, A, has a position, P_t , defined in an Earth-centric coordinate system and is the point of reference.

For example P, = (1, 2, 3) .

2. Own aircraft, A, receives the position vector, P, , of the Intruder aircraft, B,. via a data link.

For example £, = (1, 5, 7) .

3. ·^',· Based upon the respective position vectors, the processing unit 202 calculates a Line of Sight (relative range) vector, R , thus:

For example _ώ8 = P, - P _s = (0, 3, 4) .

4. At step 404, the processing unit then

calculates the relative range (slant range), which is the absolute value of the Line of Sight vector (put simply, the distance between the aircraft) : In. the running example R_/)S = 5 .

5. The processing unit 202 uses the relative range to determine the unit vector, ULOS, for the Line of Sight vector: y^∞"lli

In the example scenario J_L0S -^'(0, 0.6, 0.8) . Compute Relative Velocity

6. Own aircraft, A, has velocity v__t .

In the example scenario V, = (0.383, 1.785, 2.380) .

7. Own aircraft, A, receives the velocity vector, V_₂ , of the Intruder aircraft via the datalink.

For example V₇ =.(0.383, -0.554, -0.7391) .

8. The processing unit 202 computes the unit vector for V_₂ :

. . _g ; _{D i} . (0.383, - 0.554, - 0.739) _ ^ ^ . _{Q m)}

^■ 9. The processing unit also calculates the relative velocity vector, _R ·

v« = v₁-v, = (V_2x-v_lx,v,_y-v_ly,v_2!-v

In the example Y__R=V__]-V__I = (0.000, - 2.339, -3.1 195) .

10. At step 406, the processing unit uses the norms of the ^"velocity vectors to calculate the ratio, k, of the aircraft speeds (recalling our assumption that aircraft A is the faster aircraft) : In the example sce

Compute the Time to Intercept

11. The processing unit then calculates the "time to collision" , t:

The skilled addressee will recognise that special cases exist' where k = 1, and the aircraft are approaching and head-on. Special cases for£≠l exist where the aircraft are directly in trail, quartering (abeam) or approaching head-on.

Compute the Aspect Angle of the Intruder

12. The processing unit 202 calculates the aspect angle, a, of the Intruder aircraft, B:

cos(or) = \J_y2 · U_/∞

e.g. cos(a) = (0.383, - 0.554, - 0.739) · (¾ 0.6, 0.8) = -0.92388

= -157.5 (supplementary angle « = 22.5

Define the Conflict Frame of Reference

In general, the conflict frame of reference will be a two-dimensional plane with general orientation in the Earth coordinate system. The collision point lies in this frame, as does the Apollonius circle that defines all possible collision points. As the aircraft manoeuvre in both position and velocity, this two-dimensional plane will continuously reorient in three-dimensional space. At any given instant, a coordinate system may be established such that the two-dimensional conflict plane is defined as the x_c x y_c plane of this new frame of reference.

13. The processing unit 202 defines the x_c axis of the conflict plane in the direction of the Line of Sight vector, R_LOS , calculated in step 3 above, directed from own aircraft, A, to the Intruder aircraft, B:

In the example scenario x_c =U_/QS = (0, 0.6, 0.8) .

14. The z axis of the coordinate system is then

y_E

e.g. ^ZC ~ .V2 ^X MLOS ~ 0.383 -0.554 -0J39 = (0.000, -0.306, 0.229)

0 0.6 0.8

15 ; The unit vector for the y axis is then

yc ~ ^zc ^{x x}c ' e-g. y_c = ^ze ^xc = (-0.383, 0.000, 0.000)

At this point, the two-dimensional conflict plane now defined in inertial space and its three-dimensional orientation is known in the Earth coordinate system.

The results of the following calculations may be computed and measured within the x_c x y_c plane (i.e. the conflict plane) of the conflict frame of reference. The skilled addressee will recognise that the Apollonius circle is a theoretical construct representing all possible collision points given the present relative position and velocity of the two aircraft, as noted above. Accordingly, it is not in fact essential to calculate the location of the circle within the conflict frame of reference to determine the non-allowed steering direction. In some embodiments, however, the location of the circle is calculated and at least a portion of it is displayed to the pilot of the aircraft, together with the non-allowed steering direction, as a navigational aid.

Calculate the Apollonius Circle (Step 408)

16. The equation of the A ollonius circle is

17. The circle has its centre at:

In the example

18. The radius of the circle is

R ^L,

R = k- OS

R

In the example R = k Los _ 3^J* ^J5 -Z 1Z5. - 1 875

(r- l) (3 x 3 - 1) 8

Compute the Non-Allowed Steering Direction

The non-allowed steering direction is the direction which, if taken by aircraft A at its present speed would result in collision with the intruder aircraft B, assuming that aircraft B maintains its present velocity.

19. At step 410, the processing unit 202 calculates the non-allowed steering direction as an angle, η , to the x axis, x_c , of the conflict frame of reference (equivalent to the Line of Sight vector, R_LOS :

. . . sin(a) ,

sm(77) =— *≥1

In the example

η = -7.3°

That is to say, in the example scenario, the

non-allowed steering direction for aircraft A is a

direction, within the conflict plane of -7.3° relative to the x axis of that plane.

In embodiments of the invention, at least this direction is represented to the pilot of aircraft A.

20. The collision point is the point in the x_c x y_c conflict plane at which a collision would occur if

aircraft A were to travel along the non-allowed steering direction, at its present speed, and if the velocity vector of the Intruder aircraft B were not to change. It is given by the coordinates I : (kcos{ ), k sm^' ), 0), or

equivalently by I {kcosty), sin(a), 0) .

In the example /:(2.975, -0.383, 0) .

At step 412, the non-allowed steering direction is displayed on a display (generally in the cockpit of the aircraft), so that a pilot may act on the information.

It will be understood that in other embodiments, the output may be provided directly to a flight computer or autopilot, so that the flight computer or autopilot may take action, where required. In yet further embodiments, the method may be carried out at a fixed location, such as an air traffic control tower. In such a situation, the air traffic control system receives velocity and position information from a plurality of aircraft, and the system calculates non-allowed steering directions for each aircraft with respect to the other aircraft. The air traffic controller may use the information to direct aircraft within the controller's airspace. Of course, it will be understood that the output may be provided to a plurality of different locations and/or devices, as required.

Turning to Figure 5, there is shown an example of a display that may be used when the collision velocity derived using the algorithm is to be provided to a cockpit of an aircraft for use by a pilot. The display provides for all practical purposes instantaneous information to a pilot about a potential collision or intercept.

Figure 5, at 500, is a display that represents a defined area of airspace (as denoted symbolically for discussion at 500 by the region) and the arrow 502 denotes the velocity of the first aircraft A relative to the airspace. In the simple example of Figure 5, it is assumed that there is only one other aircraft B in the airspace defined by region 500.^' The line 504 represents a non-allowed steering direction to a point of intercept with the second aircraft B. That is, the pilot is required to control the first aircraft A so that it does not track along the direction of the line 504. If the pilot controls the aircraft so that arrow 502 and line 504 overlap, a collision will result if this direction is taken by the first aircraft A until the time to intercept has elapsed. Also shown in display 500 of Figure 5 is a segment 506 of the Apollonius circle drawn around the second aircraft B. An arrow 508 denotes the velocity vector of the second aircraft B and the point, I, where the arrow 508 intersects the segment 506 indicates the point at which a collision will occur.

It will be understood that in the context described herein, the term "control" refers to either steering the aircraft and/or controlling the speed of the aircraft, as it will be understood that any change in the direction or the speed of the aircraft will affect the non-allowed steering direction relative to the other aircraft.

At Figure 6, there is shown a more complex example of a display in accordance with an embodiment of the

invention.

In particular, the region 600 is equivalent to region 600 in Figure 6 (i.e. the region represents a general volume/area of airspace relative to the aircraft) and arrow 602 (or reference mark) defines the general velocity of the aircraft relative to the airspace.

In Figure 6, however, it is assumed that there are three aircraft in the defined airspace 600. The three aircraft are denoted by lines 604a, 604b and 604c. Each line represents a non-allowed steering direction.

That is, the pilot is required to control the aircraft so that the aircraft (as represented by arrow 602) does not sustain tracking along any one of lines 604a, b or c. If the pilot controls the aircraft so that arrow 602 and any one of lines 604a, b or c overlap until the respective time to intercept elapses, a collision will most likely result.

Although not the case in Figure 5, 6 and 7, inpreferred embodiments, the length of the line (i.e. line 504 or 604) represents a velocity component, thereby providing the pilot, with more information regarding the movement of other aircraft in the airspace.

It will also be understood that instead of a line, a region (not shown) may also be used to represent a non-allowed steering region. This may be useful where there, is a need to provide a buffer between aircraft · In such a situation, a pilot would need to ensure that they do not control the aircraft in a way that allows the aircraft to track along a direction within the one or more non-allowed regions. For example, Figure 7 shows a display 700 similar to that shown in Figure 5, with own aircraft A shown at bottom-centre with a velocity vector 702 extending from ^'it. As in Figure 5, an intruder aircraft B is shown, also having a velocity vector, which serves as a predictor line. A segment of an Apollonius circle, calculated as described herein, is shown around the intruder aircraft. The predictor line and the circle intersect at the point I, which is the point at which a collision would result if aircraft A were to travel towards it at its current speed and if the intruder aircraft were to maintain its current velocity.

Accordingly, a line 704 is shown on the display,

representing the non-allowed steering direction for aircraft A. In this example, however, there is also a schema of desired minimum miss-distance, which includes a minimum miss-distance if A were to pass aft of B and another, larger, minimum miss-distance if A were to pass ahead of B. Accordingly, the display also shows

respective bars 704a, 704b indicative of the minimum fore and aft miss-distances. To assist the pilot of aircraft A further, in some embodiments respective vectors 706a, 706b shown from aircraft A to the fore and aft bars 704a, 704b. To satisfy the schema, aircraft A should not track along a direction falling between these vectors 706a, 706b!

It will also be understood that^" while Figures 5, 6 and 7 are representations of two dimensional displays, such information may be provided on a three-dimensional display, on a head-up display, or on an augmented display (e.g. a display that projects the information into a "real" space (e.g. out of a cockpit window)) , to provide the pilot with a more realistic and intuitive manner of visualising the non-allowed steering direction.

It will further be understood that, while the embodiments discussed above involve providing information relating to the non-allowed steering direction to the pilot via a display, embodiments of the invention are possible in which this information is provided

additionally or alternatively to an autopilot system 218 (in Figure 2) , which controls the aircraft in . dependence upon that information in such a manner as to avoid a collision. In a preferred such embodiment, the autopilot does not indiscriminately- avoid tracking along the non-allowed steering direction, but avoids doing so only in certain circumstances (for example, the circumstance that the time to intercept, discussed below, is less than a predetermined threshold) .

Advantages

The embodiments and the broader invention described herein provide a number of advantages.

Firstly, embodiments of the invention provide a system and method that allow each individual aircraft in a particular space (such as an airspace) to track other vehicles, using information (e.g. GPS and ADS-B) which is commonly available to many aircraft. This is particularly important in airspace that is not monitored or controlled by third parties (such as services from air traffic control towers) . Secondly, embodiments of the invention provide an output that significantly decreases the conceptual gap between a pilot's intuitive understanding of airspace and the type of information provided on the display. That is, a pilot can intuitively understand a non-allowed steering direction, or a region including a continuum of

non-allowed steering directions for the purpose of

satisfying a schema of desired minimum miss-distances, and correspondingly, the pilot does not need comprehensive training on how to use the system.

Thirdly, at least preferred embodiments of the invention provide a visual representation to the pilot of the point, I, at which a collision will arise if he or she tracks towards it, which can be of assistance in planning manoeuvres and reducing thinking time .

Fourthly, embodiments of the invention are easily adapted for use in any traffic system where there is an inherent danger of collision. Such applications could include boating/shipping/underwater applications, road vehicle applications, space/outer space applications, or any other situation where a number of vehicles need to be managed without collision within a defined space.

Variations and Modifications

Although not required, the embodiments described with reference to the Figures can be implemented as an

Application Programming Interface (API) or as a series of libraries for use by a developer or can be included within another software application, such as a terminal or personal computer operating system or a portable computing device operating system. Generally> as program modules include routines, objects, components and data files assisting in the performance of particular functions, the skilled person will understand that the functionality of the software application may be distributed across a number of routines, objects or components to achieve the same functionality desired herein.

It will also be appreciated that where the methods and systems of the present invention are either wholly implemented by a computing system or partly implemented by one or more computing systems then any appropriate computing system may be used. This may include a

standalone computing device, a networked computing device or devices and/or a dedicated hardware device, such as a vehicle management system. Where the terms "computing system" and "computing device" are used, these terms are intended to cover any appropriate arrangement of hardware capable of implementing the function or functions

described.

Where the term "processor" is used, the term is intended to cover an arrangement capable of carrying out one or more appropriate calculations or logical processes. Therefore, the term "processor" may encompass a generic central processing unit commonly found in a flight management system, mission computer, or autopilot, a desktop or portable computing systems and programmable using software, an integrated circuit specifically designed and programmed to carry out the method steps and the calculations required by the embodiments or broader invention described herein, an electrical circuit or circuits, such as a logic array, which is physically wired to carry out the method steps and the calculations required by the embodiments or broader invention described herein, or any other device, whether electrical, optical, or mechanical in nature, or any combination thereof. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of. the

invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

The foregoing describes only some preferred

embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

Any reference to prior art contained herein is not to be taken as an admission that the information is common general knowledge, unless otherwise indicated.

Claims

CLAIMS :

1. A method for assisting in the navigation of a first, vehicle, comprising the steps of:

obtaining position and velocity information for the first vehicle and position and velocity information for a second vehicle;

using the position and velocity information for the first and second vehicles to calculate a non-allowed steering direction, being a direction which if taken by the first vehicle may result in a collision with the second vehicle; and

outputting data indicative of the_. non-allowed steering direction.

2. A method in accordance with Claim 1, wherein the step of calculating the non-allowed steering direction includes the step of identifying a location at which the vehicles would collide, assuming that the first vehicle maintains its current speed and the second vehicle maintains its^' current velocity.

3. A method in accordance with any one of Claims 1 and 2, wherein the step of calculating the non-allowed

steering direction includes the step of calculating a locus of points at which the first and second vehicles might collide.

4. A method in accordance with Claim 3, the step of calculating the locus of points including the steps of: calculating the relative range between the first and second vehicles;

calculating the ratio of the speeds of the first and second vehicles; and

determining as the locus of points at least a segment of an Apollonius circle calculated in dependence upon the relative range and the ratio of the speeds of the first and second vehicles.

5. A method in accordance with any one of Claims 3 and Claim 4, wherein the step of calculating the non-allowed steering direction includes the step of determining plane in which the locus of points lies.

6. A method in accordance with any one of Claims 3 to 5, wherein the step of calculating the non-allowed steering direction includes identifying the point, Γ, at which the second vehicle will pass through the locus of points, assuming it continues to travel with its current velocity.

7. A method in accordance with Claim 6, wherein the step of calculating the non-allowed steering direction includes the step of calculating an aspect angle of the second vehicle.

8. A method in, accordance with any one of Claims 6 and 7, wherein the non-allowed steering direction is

determined to be a vector from the current location of the first vehicle to the point, I.

9. A method in accordance with any one of the preceding Claims, further comprising the step of calculating the time to point of closest approach, being the time from the present moment to the time of collision if the first vehicle follows the non-allowed steering direction.

10. A method in accordance with any one of the preceding Claims, comprising the further step of visually displaying the non-allowed steering direction.

11. A method in accordance with Claim 10, comprising the further step of:

visually displaying a reference mark representing the first vehicle; and

visually displaying a line extending from the reference mark, the line representing. the non-allowed steering direction.

12. A method in accordance with Claim 11 when dependent upon Claim 6, further comprising visually displaying a mark indicating the location of point I.

13. A method in accordance with any one of Claims 11 and 12, further comprising visually displaying a line

indicating a steering direction which, if taken by the first vehicle, would result in the first vehicle passing the second vehicle with a minimum required miss-distance.

1 . A method in accordance with Claim 13 , further comprising visually displaying a plurality of lines indicating respective steering directions which, if taken by the first vehicle, would result in the first vehicle passing the second vehicle with respective minimum

required miss-distances.

15. A method in accordance with Claim 14, wherein the plurality of lines includes at least a first line

indicating a first steering direction which, if taken by the first vehicle would result in the first vehicle passing forward of the second vehicle and a second steering direction which, if taken by the first vehicle would result in the first vehicle passing behind the second vehicle.

16; A method in accordance with Claim 15, wherein the first and second steering directions relate to minimum required miss-distances which are unequal.

17. A method in accordance with any one of the preceding Claims, comprising:

identifying a plurality of second vehicles^' within a predefined region, and obtaining velocity and position information for each of the plurality of second vehicles; and

using the information to determine respective non-allowed steering directions for the first vehicle with respect to each of the plurality of second vehicles.

18. A method in accordance with Claim 17, comprising the further step of visually displaying at least a subset of the plurality of non-allowed steering directions.

19. A method in accordance with Claim 18, further comprising calculating a respective time to closest approach for each of the plurality of second vehicles.

20. A method in accordance with Claim 19, comprising selecting a subset of the ^' plurality of non-allowed steering directions for visual display in dependence upon the respective calculated times to closest approach.

21. A method in accordance with Claim 20, wherein the subset is selected to include those non-allowed steering directions having the shortest times to closest approach.

22. A method in accordance with any one of the preceding claims, comprising iterating the method of any one of Claims 1 to 21 to update the non-allowed steering

direction.

23. A method in accordance with any one of the preceding claims, comprising the step of outputting the data

indicative of the non-allowed steering direction to an autopilot system.

24. A system for assisting in the navigation of a first vehicle, comprising:

• an arrangement arranged to obtain position and velocity information for the first vehicle and position and velocity information for a second vehicle;

a processor arranged to use the position and velocity information for the first and second vehicles to calculate a non-allowed steering direction, being a direction which if taken by the first vehicle may result in a collision with the second vehicle; and

an interface arranged to output data indicative of the non-allowed steering direction.

25. A system in accordance with Claim 24, wherein the processor is arranged to use the position and velocity information for the first and second vehicles to identify a location at which the vehicles would collide, assuming that the first vehicle maintains its current speed and the second vehicle maintains . its current velocity.

26. A system in accordance with any one of Claims 24 and 25, wherein the processor is arranged to calculate a locus of points at which the first and second vehicles might collide .

27. A system in accordance with Claim 26> wherein the processor is arranged to calculate the relative range between the first and second vehicles and the ratio of the speeds of the first and second vehicles and to determine as the locus of points at least a segment of an Apollonius · circle calculated in dependence upon the relative range and the ratio of the speeds of the first and second

vehicles .

28. A system in accordance with any one of Claims 26 and Claim 27, wherein the processor is arranged to determine a plane in which the locus of points lies.

29. A system in accordance with any one of Claims 26 to 28, wherein the processor is arranged to identify the point, I, at which the second vehicle will pass through the locus of points, assuming it continues to travel with its current velocity.

30. A system in accordance with Claim 29, wherein the processor is arranged to calculate an aspect angle of the second vehicle .

31. A system in accordance with any one of Claims 29 and 30, wherein the processor is arranged to determine the non-allowed steering direction as being a vector from the current location of the first vehicle to the point, I.

32. A system in accordance with any one Claims 24 to 31, wherein the processor is adapted to calculate the time to point of closest approach, being the time from the present moment to the time of collision if the first vehicle follows the non-allowed steering direction.

33. A system in accordance with ariy one of Claims 24 to 32, further including a display arranged to visually display the non-allowed steering direction.

34. A system in accordance with Claim 33, wherein the display is further arranged to display a reference mark representing the first vehicle/ and a line extending from the reference mark, the line representing the non-allowed steering direction.

35. A system in accordance with Claim 34 when dependent upon Claim 29, wherein the display is further arranged to display a mark indicating the location of point I.

36. A system in accordance with any one of Claims 34 and 35, wherein the display is further arranged to display a line indicating a steering direction which, if taken by the first vehicle, would result in the first vehicle passing the second vehicle with a minimum required miss-distance.

37. A system in accordance with Claim 36, wherein the display is further arranged to display a plurality of lines indicating respective steering directions which, if taken by the first vehicle, would result in the first vehicle passing the second vehicle with respective minimum required miss-distances.

38. A system in accordance ith Claim 37, wherein the plurality of lines includes at least a first line

indicating a first steering direction which, if taken by the first vehicle would result in the first vehicle .

passing forward of the second vehicle and a second steering direction which, if taken by the first vehicle would result in the first vehicle passing behind the second vehicle.

39. A system in accordance with Claim 38, wherein the first and second steering directions .relate to minimum required miss-distances which are unequal.

40. A system in accordance with any one of Claims 24 to 39, wherein the arrangement is arranged to identify a plurality of second vehicles within a predefined region; to obtain velocity and position information for each of the plurality of second vehicles; and to use the

41. A system in accordance with Claim 40 where dependent upon Claim 33, wherein the display is further arranged to display at least a subset of the plurality of non-allowed steering directions.

42. A system in accordance with Claim 41, wherein the processor is further arranged to calculate a respective time to closest approach for each of the plurality of second vehicles.

43. · A system in accordance with Claim 42, wherein the processor is arranged to select a subset of the plurality of non-allowed steering directions for visual display in dependence upon the respective calculated times to closest approach.

44. A system in ' accordance with Claim 43, wherein processor is arranged to select the subset to include those non-allowed steering directions having the shortest times to closest approach.

45. A system in accordance with any one of the preceding claims, arranged to iterate the method of any one of

Claims 24 to 44 to update the non-allowed steering

direction .

46. A system in accordance with any one of Claims 24 to 45, arranged to output the data indicative of the

non-allowed steering direction to an autopilot system.

47. A computer program including at least one instruction which, when executed on a computing system, is arranged to implement a method in accordance with any one of Claims 1 to 23.

48. A computer readable medium including a computer program in accordance with Claim 47.

49. Transmitting or receiving a data signal comprising at least one encoded instruction in accordance with the computer program of Claim 47.