Safe emergency landing of a UAV

• US 9,274,529 B2
• Filed: 02/21/2013
• Issued: 03/01/2016
• Est. Priority Date: 02/26/2012
• Status: Active Grant

• Current Assignee: Elbit Systems Limited
• Original Assignee: Elbit Systems Limited
• Inventors: Ben-Shachar, Eyal, Godel, Reuven, Mor, Roy
• Primary Examiner(s): Dager, Jonathan M
• Application Number:
  US14/380,949
• Publication Number:
  US 20150153740A1
• Time in Patent Office: 1,104 Days
• US Class Current: 1/1
• CPC Class Codes: B64U 2201/10 autonomous, i.e. by navigating independently from ground or air stations, e.g. by using inertial navigation systems [INS]
• CPC Class Codes: B64U 2201/104 using satellite radio beacon positioning systems, e.g. GPS
• CPC Class Codes: B64U 2201/20 Remote controls
• CPC Class Codes: B64U 70/40 Landing characterised by flight manoeuvres, e.g. deep stall
• CPC Class Codes: G05D 1/0072 to counteract a motor failure
• CPC Class Codes: G05D 1/0088 characterized by the autonomous decision making process, e.g. artificial intelligence, predefined behaviours using knowledge based models G06N5/00
• CPC Class Codes: G05D 1/0676 specially adapted for landing
• CPC Class Codes: G05D 1/105 specially adapted for unpowered flight, e.g. glider, parachuting, forced landing parachutes per se B64D17/00
• CPC Class Codes: G05D 1/106 Change initiated in response to external conditions, e.g. avoidance of elevated terrain or of no-fly zones

Abstract

Method for autonomous safe emergency landing of a powered unmanned aerial vehicle (UAV) in the event of an engine failure. A landing approach trajectory is generated, including a downwind leg, initiating at an initiation point of the trajectory, an upwind leg, terminating at a selected touchdown point, and a U-turn leg, joining between the downwind leg and the upwind leg. The UAV is directed to the initiation point to follow the downwind leg. A glide ratio of the UAV is repeatedly determined based on current flight conditions. A current turning point is repeatedly determined along the downwind leg based on the determined glide ratio, the U-turn leg initiating at the current turning point. When the UAV arrives at the current turning point, the UAV is directed to follow the U-turn leg and the upwind leg, for landing the UAV at the selected touchdown point.

Claims

1. A method for autonomous safe emergency landing of a powered unmanned aerial vehicle (UAV) in the event of an engine failure, the method comprising the procedures of:

generating a landing approach trajectory, comprising;

a downwind leg, initiating at an initiation point of said trajectory, said downwind leg directed toward a first direction of a runway;

an upwind leg, extending along said runway and terminating at a selected touchdown point located on said runway, said upwind leg being substantially parallel to said downwind leg and directed toward a second direction of said runway opposite to said first direction; and

a U-turn leg, joining between said downwind leg and said upwind leg;

directing said UAV to said initiation point to follow said downwind leg of said landing approach trajectory;

repeatedly determining a glide ratio of said UAV, based on current flight conditions of said UAV;

repeatedly determining a current turning point along said downwind leg for landing said UAV at said selected touchdown point, said U-turn leg initiating at said current turning point, wherein the determination of said current turning point is based on the determined glide ratio and is performed each time with respect to a precedingly determined turning point;

repeatedly determining a touchdown point corresponding to said current turning point, based on said determined glide ratio, wherein said procedure of determining a current turning point is performed with respect to the discrepancy between;

(i) the touchdown point that was precedingly determined in correspondence with the precedingly determined turning point, and (ii) said selected touchdown point; and

when said UAV arrives at said current turning point, directing said UAV to follow said U-turn leg and said upwind leg of said landing approach trajectory, for landing said UAV safely along said runway at said selected touchdown point.

2. The method of claim 1, further comprising the procedures of:

selecting a selected touchdown point, wherein a determined prospective height of said UAV over said selected touchdown point is sufficient to enable said UAV to perform said safe emergency landing at said selected touchdown point, and wherein said prospective height is determined based on said determined glide ratio; and

directing said UAV to glide towards said selected touchdown point, once said engine failure occurs.

3. The method of claim 2, wherein said selected touchdown point is selected from a database comprising a collection of information relating to a plurality of touchdown points for emergency landing, the information comprising:

the direction of the runway on which the respective touchdown point is located; and

the geographical location of the respective touchdown point.

4. The method of claim 1, further comprising the procedures of:

determining a prospective height of said UAV over said selected touchdown point, based on said determined glide ratio;

determining if gliding along a waiting trajectory is possible, based on whether the prospective height of said UAV exceeds a minimum height predefined to enable said safe emergency landing at said selected touchdown point; and

directing said UAV to glide along said waiting trajectory if determined to be possible.

5. The method of claim 4 further comprising the procedure of:

generating said waiting trajectory, comprising the sub-procedures of;

generating a waiting pattern, located over an area in proximity of said selected touchdown point;

determining a joining point along said waiting pattern;

determining an exit point along said waiting pattern wherefrom said UAV can begin following said landing approach trajectory;

directing said UAV to join said waiting pattern at said joining point;

directing said UAV to glide along said waiting pattern; and

directing said UAV to exit said waiting pattern at said exit point.

6. The method of claim 5, wherein said UAV is directed to exit said waiting pattern once said UAV descends below a predefined exit height that is of sufficient height for said UAV to perform said safe emergency landing at said selected touchdown point.

7. The method of claim 5, wherein said waiting trajectory is tangential to said downwind leg of said landing approach trajectory, and wherein an exit point of said waiting trajectory and an initiation point of said landing approach trajectory are determined to be located at the tangency point of said waiting trajectory and said downwind leg.

8. The method of claim 1, further comprising the procedure of continuously measuring said current flight conditions with sensors mounted onboard said UAV, wherein said flight conditions are selected from the list consisting of:

location and navigation information of said UAV;

level of fuel onboard said UAV; and

atmospheric conditions in the vicinity of said UAV.

9. The method of claim 1, wherein said procedure of repeatedly determining a glide ratio of said UAV comprises auto-learning the glide ratio by iteratively determining said glide ratio until convergence to a definite value, wherein said auto-learning is at least partially empiric.

10. The method of claim 1, wherein said UAV operates autonomously.

11. A powered unmanned aerial vehicle (UAV) operable to perform an autonomous safe emergency landing in the event of an engine failure, said UAV comprising:

a flight control system for controlling the flight of said UAV, said flight control system comprising a processing unit;

a safe emergency landing system coupled with said flight control system, said safe emergency landing system comprising a storage device readable by said processing unit of said flight control system, tangibly embodying a program of instructions executable by said processing unit to perform method procedures for safe emergency landing of said unmanned aerial vehicle in the event of an engine failure, the method procedures comprising;

generating a landing approach trajectory, comprising;

a downwind leg, initiating at an initiation point of said trajectory, said downwind leg directed toward a first direction of a runway;

an upwind leg, extending along said runway and terminating at a selected touchdown point located on said runway, said upwind leg being substantially parallel to said downwind leg and directed toward a second direction of said runway opposite to said first direction; and

a U-turn leg, joining between said downwind leg and said upwind leg;

providing said landing approach trajectory to said flight control system, for directing said UAV to said initiation point to follow said downwind leg;

repeatedly determining a glide ratio of said UAV, based on current flight conditions of said UAV;

repeatedly determining a current turning point along said downwind leg for landing said UAV at said selected touchdown point, said U-turn leg initiating at said current turning point, wherein the determination of said current turning point is based on the determined glide ratio and is performed each time with respect to a precedingly determined turning point;

repeatedly determining a touchdown point corresponding to said current turning point, based on said determined glide ratio, wherein said procedure of determining a current turning point is performed with respect to the discrepancy between;

(i) the touchdown point that was precedingly determined in correspondence with the precedingly determined turning point, and (ii) said selected touchdown point;

repeatedly providing said current turning point to said flight control system, for directing said UAV to glide towards said current turning point; and

when said UAV arrives at said current turning point, indicating to said flight control system to direct said UAV to follow said U-turn leg and said upwind leg of said landing approach trajectory, for landing said UAV safely along said runway at said selected touchdown point.

12. The UAV of claim 11, wherein said flight conditions are selected from the list consisting of:

location and navigation information of said UAV;

level of fuel onboard said UAV; and

atmospheric conditions in the vicinity of said UAV.

13. The UAV of claim 11, further comprising at least one sensor selected from the list consisting of:

a sensor for continuously providing said location and navigation information;

a sensor for continuously indicating said level of fuel;

a sensor for continuously providing said atmospheric information.

14. The UAV of claim 11, further comprising a database comprising a collection of touchdown points for emergency landing of said UAV, wherein said program of instructions of said safe emergency landing system is executable to further perform the method procedure of selecting said selected touchdown point from said collection of touchdown points, wherein a determined prospective height of said UAV over said selected touchdown point is sufficient to enable said UAV to perform said safe emergency landing at said selected touchdown point, and wherein said prospective height is determined based on said determined glide ratio.

15. The UAV of claim 11, wherein said program of instructions of said emergency landing system is executable to further perform the method procedures of:

determining a prospective height of said UAV over said selected touchdown point, based on said determined glide ratio;

determining if gliding along a waiting trajectory is possible, based on whether the prospective height of said UAV exceeds a minimum height predefined to enable said safe emergency landing at said selected touchdown point; and

indicating to said flight control system to direct said UAV to glide along said waiting trajectory if determined to be possible.

16. The UAV of claim 15, wherein said program of instructions of said emergency landing system is executable to further perform the method procedures of:

generating said waiting trajectory, comprising the sub-procedures of;

generating a waiting pattern, located over an area in proximity of said selected touchdown point;

determining a joining point along said waiting pattern; and

determining an exit point along said waiting pattern wherefrom said UAV can begin following said landing approach trajectory;

providing the generated waiting trajectory to said flight control system for directing said UAV to join said waiting pattern at said joining point, to glide along said waiting pattern, and to exit said waiting pattern at said exit point.

17. The UAV of claim 11, wherein said method procedure of repeatedly determining a glide ratio of said UAV comprises auto-learning the glide ratio by iteratively determining said glide ratio until convergence to a definite value, wherein said auto-learning is at least partially empiric.

18. A system for mounting on a powered unmanned aerial vehicle (UAV) to allow safe emergency landing of said UAV in the event of an engine failure, said system coupled with a flight control system of said UAV, said system comprising:

a storage device readable by a processing unit of said flight control system, tangibly embodying a program of instructions executable by said processing unit to perform method procedures comprising;

generating a landing approach trajectory, comprising;

a downwind leg, initiating at an initiation point of said trajectory, said downwind leg directed toward a first direction of a runway;

an upwind leg, extending along said runway and terminating at a selected touchdown point located on said runway, said upwind leg being substantially parallel to said downwind leg and directed toward a second direction of said runway opposite to said first direction; and

a U-turn leg, joining between said downwind leg and said upwind leg;

providing said landing approach trajectory to said flight control system, for directing said UAV to said initiation point to follow said downwind leg;

repeatedly determining a glide ratio of said UAV, based on current flight conditions of said UAV;

repeatedly determining a current turning point along said downwind leg for landing said UAV at said selected touchdown point, said U-turn leg initiating at said current turning point, wherein the determination of said current turning point is based on said determined glide ratio and is performed each time with respect to a precedingly determined turning point;

repeatedly determining a touchdown point corresponding to said current turning point, based on said determined glide ratio, wherein said procedure of determining a current turning point is performed with respect to the discrepancy between;

(i) the touchdown point that was precedingly determined in correspondence with the precedingly determined turning point, and (ii) said selected touchdown point;

repeatedly providing said current turning point to said flight control system, for directing said UAV to glide towards said current turning point; and

when said UAV arrives at said current turning point, indicating to said flight control system to direct said UAV to follow said U-turn leg and said upwind leg of said landing approach trajectory, for landing said UAV safely along said runway at said selected touchdown point.