Device at an airborne vehicle and a method for collision avoidance

• US 20080249669A1
• Filed: 12/21/2007
• Published: 10/09/2008
• Est. Priority Date: 12/22/2006
• Status: Active Grant

• Current Assignee: Saab AB
• Original Assignee: Saab AB
• Inventors: Skarman, Erik
• Granted Patent: US 8,700,231 B2
• Time in Patent Office: Days
• US Class Current: 701/3
• CPC Class Codes: G08G 5/0078 for monitoring traffic from the aircraft radar or analogous systems specially adapted for traffic control G01S13/91
• 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

A device at an airborne vehicle including a flight control system configured to control the behaviour of the airborne vehicle based on acceleration commands, a first control unit configured to provide the acceleration commands to the flight control system, and a collision avoidance unit. The collision avoidance unit includes a detection unit arranged to detect whether the airborne vehicle is on a collision course and a second control unit arranged to feed forced acceleration commands to the flight control system upon detection that the airborne vehicle is on a collision course. A method for collision avoidance in an airborne vehicle.

Claims

1. A device at an airborne vehicle, comprising:

a flight control system arranged to control the behaviour of the airborne vehicle based on acceleration commands,

a first control unit arranged to provide said acceleration commands to the flight control system,

a collision avoidance unit comprising a detection unit configured to detect whether the airborne vehicle is on a collision course and a second control unit arranged to feed forced acceleration commands to the flight control system upon detection that the airborne vehicle is on a collision course.

2. The device at an airborne vehicle according to claim 1, wherein the detection unit is configured to determine a first distance to at least one obstacle and a second distance at which said at least one obstacle is estimated to be passed, and to activate the second control unit when the first distance is smaller than a first predetermined value and the second distances is smaller than a second predetermined value.

3. The A device at an airborne vehicle according to claim 2, wherein the detection unit is configured to deactivate the second control unit when the second distance exceeds a predetermined third value.

4. The device at an airborne vehicle according to claim 1, wherein the second control unit comprises a calculation unit configured to

determine a product of a closing velocity (v_c) to the obstacle and a time derivative of a line of sight to the obstacle ({dot over (σ

)}), and

to form the forced acceleration commands based on a negation of the determined product (v_c·

{dot over (σ

)}).

5. The device at an airborne vehicle according to claim 4, wherein the calculation unit is configured to form the acceleration commands based on the equation a_y=−

k·

v_c{dot over (σ

)}, wherein a_y is the acceleration in a direction perpendicular to the travelling direction and k is a positive constant.

6. The device at an airborne vehicle according to claim 5, wherein the constant k lies within the range 1 to 6.

7. The device at an airborne vehicle according to claim 6, wherein the constant k lies within the range 2 to 4.

8. The device at an airborne vehicle according to claim 7, wherein the constant k is approximately 3.

9. The device at an airborne vehicle according to claim 4, wherein the second control unit comprises a pre-calculation unit arranged to compare the time derivative of the line of sight ({dot over (σ

)}) or an equivalence thereof to a thresholding value, and if the thresholding value is exceeded activate the calculation unit and if not exceeded, to feed a predetermined forced acceleration command to the flight control system.

10. The device at an airborne vehicle according to claim 4, wherein the second distance is determined as a function of the distance to the obstacle and the time derivative of the line of sight ({dot over (σ

)}).

11. A method for collision avoidance in an airborne vehicle the method comprising:

detecting whether the airborne vehicle is on a collision course, forming forced acceleration commands based on a relation between the airborne vehicle and an obstacle, and

providing forced acceleration commands to a flight control system of the airborne vehicle upon detection that the airborne vehicle is on a collision course with said obstacle so as to avoid collision.

12. The method for collision avoidance in an airborne vehicle according to claim 11, wherein detecting whether the airborne vehicle is on a collision course comprises

determining a first distance to said obstacle,

determining a second distance at which said obstacle is estimated to be passed, and

establish that the airborne vehicle is on a collision course if the first distance is smaller than a first predetermined value and the second distances is smaller than a second predetermined value.

13. The method for collision avoidance in an airborne vehicle according to claim 12, further comprising:

continuously determining the second distance during the step of providing forced acceleration commands, and

ending the step of providing forced acceleration commands to the flight control system when the second distance exceeds a predetermined third value.

14. The method for collision avoidance in an airborne vehicle according to claim 12, wherein the second distance is determined as a function of the distance to the obstacle and the time derivative of the line of sight ({dot over (σ

)}).

15. The method for collision avoidance in an airborne vehicle according to claim 11, wherein providing forced acceleration commands to the flight control system comprises

determining a product of a closing velocity (v_c) to the obstacle and a time derivative of a line of sight to the obstacle ({dot over (σ

)}), and

forming the forced acceleration commands based on a negation of the determined product (v_c·

{dot over (σ

)}).

16. The method for collision avoidance in an airborne vehicle according to claim 15, wherein the acceleration commands are formed based on the equation a_y=−

k·

v_c·

{dot over (σ

)}, wherein a_y is the acceleration in a direction perpendicular to the travelling direction and k is a positive constant.

17. The method for collision avoidance in an airborne vehicle according to claim 11, further comprising:

comparing a time derivative of a line of sight ({dot over (σ

)}) or an equivalence thereof to a threshold value,

and if comparison indicates that the threshold value is exceeded, providing forced acceleration commands to a flight control system comprises;

determining a product of a closing velocity (v_c) to the obstacle and a time derivative of a line of sight to the obstacle ({dot over (σ

)}), and

forming the forced acceleration commands based on a negation of the determined product (v_c·

{dot over (σ

)}),

and if the comparison indicates that the threshold value is not exceeded, providing forced acceleration commands to the flight control system comprises forming forced acceleration commands with a predetermined magnitude.