Control Method to Damp Quadrotor Slung Payload Mode

• US 20150331427A1
• Filed: 05/13/2014
• Published: 11/19/2015
• Est. Priority Date: 05/13/2014
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Chaudary, Ashwani K.
• Granted Patent: US 10,739,790 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B64D 1/22 Taking-up articles from earth's surface
• CPC Class Codes: B64U 10/13 Flying platforms
• CPC Class Codes: B64U 10/14 with four distinct rotor axes, e.g. quadcopters
• CPC Class Codes: B64U 2101/60 for transporting passengers; for transporting goods other than weapons
• CPC Class Codes: B64U 30/20 Rotors; Rotor supports
• CPC Class Codes: G05D 1/0858 specially adapted for vertical take-off of aircraft

Abstract

A quadrotor or other vertical lift aerial vehicle measures an angle of a payload slung from the quadrotor relative to a body of the quadrotor. Using this measurement a signal may be generated that adjusts a flight characteristic of the quadrotor to counteract swing in the payload. A feedback function for generating the feedback signal may include proportional and derivative gain functions as well as non-linear signal processing functions. The feedback signal may be added to normal input control signals to cause acceleration in the direction of the payload angle that damp oscillation of the slung payload caused by wind or movements of the quadrotor.

Claims

1. A method of controlling a payload angle of a payload that is slung from an aerial vehicle comprising:

determining an angle of the payload relative to a body of the aerial vehicle;

generating an adjustment command corresponding to the angle of the payload;

applying the adjustment command to cause a change in at least one of a pitch angle of the body and a roll angle of the body that accelerates the aerial vehicle in a direction of the angle of the payload.

2. The method of claim 1, wherein generating the adjustment command comprises:

applying a proportional gain function to the payload angle;

applying a derivative function to the payload angle, the derivative function including a delay filter fed back to an output of a derivative gain function;

ignoring the angle of the payload when the angle is less than a threshold angle; and

generating the adjustment command including a first modification to at least one of an aerial vehicle pitch command and a second modification to an aerial vehicle roll command.

3. The method of claim 2, wherein the threshold angle is a range of 0 degrees to 3 degrees.

4. The method of claim 2, wherein the threshold angle is a range of 0 degrees to 5 degrees.

5. The method of claim 2, wherein the payload angle is half-wave rectified prior to applying the proportional gain function and applying the derivative function.

6. The method of claim 1, wherein applying the adjustment command comprises adding the adjustment command to an existing control input signal of the aerial vehicle.

7. The method of claim 1, wherein the aerial vehicle is a quadrotor.

8. An aerial vehicle that damps oscillation of a payload that is slung from the aerial vehicle comprising, the aerial vehicle comprising:

a body having lift elements;

a payload attachment configured to attach the payload, the payload coupled to the payload attachment; and

a controller configured to measure an angle of the payload relative to the body and, responsive to the angle of the payload, adjust an orientation of the body in a direction of the angle of the payload.

9. The aerial vehicle of claim 8, wherein the controller has computer-executable instructions that cause the controller to:

implement a forward control path that controls the orientation of the body; and

implement a feedback function that processes the angle of the payload into an adjustment command that is fed into the forward control path.

10. The aerial vehicle of claim 9, wherein the feedback function comprises a proportional gain function and a derivative function that acts on the angle of the payload.

11. The aerial vehicle of claim 10, wherein the feedback function further comprises a first non-linear function that creates a null-control zone when the angle of the payload is less than a threshold.

12. The aerial vehicle of claim 11, wherein the feedback function further comprises a second non-linear function that implements a relay function when developing the adjustment command.

13. The aerial vehicle of claim 12, wherein the adjustment command includes a pitch angle adjustment and a roll angle adjustment.

14. The aerial vehicle of claim 8, wherein the lift elements include rotors mounted in a plane parallel to or coincident with a long dimension of the body.

15. A quadrotor configured to automatically compensate for changes in an angle of a payload that is slung from the quadrotor comprising:

four lift rotors;

a body coupling the four lift rotors;

a payload attachment; and

a controller configured to;

measure the angle of the payload relative to a plane through the four lift rotors;

when a threshold condition is present, generate an adjustment command responsive to the angle of the payload; and

apply the adjustment command to an input control signal to cause the quadrotor to accelerate in a direction of the angle of the payload.

16. The quadrotor of claim 15, wherein the threshold condition is the angle of the payload being greater than a predetermined minimum angle of the payload wherein when the threshold condition is not present, setting the adjustment command to null so that no change is made to the input control signal.

17. The quadrotor of claim 15, wherein the controller is further configured to cap the adjustment command to a value corresponding to a saturation threshold angle when the angle of the payload exceeds the saturation threshold angle.

18. The quadrotor of claim 15, wherein generating the adjustment command comprises processing the angle of the payload using a feedback function with a proportional gain function and a derivative gain function to provide an intermediate result.

19. The quadrotor of claim 18, wherein generating the adjustment command further comprises processing the intermediate result to remove values below a threshold value.

20. The quadrotor of claim 18, where applying the adjustment command to the input control signal comprises adding a pitch correction signal to a pitch input signal and a roll correction signal to a roll input signal.