Rotor control law for multi-rotor vehicles systems and methods

Patent metadata

Field	Value
Publication number	US-10908618-B2
Application number	US-201816188938-A
Country	US
Kind code	B2
Filing date	Nov 13, 2018
Priority date	Aug 31, 2018
Publication date	Feb 2, 2021
Grant date	Feb 2, 2021

Abstract

Methods and systems according to one or more examples are provided for controlling a multi-rotor vehicle. In one example, a multi-rotor vehicle comprises an airframe and a plurality of rotors coupled to the airframe. The multi-rotor vehicle further comprises a controller, coupled to the airframe, configured to determine a rotational speed of each of the plurality of rotors, and adjust the rotational speed of each of the plurality of rotors such that the rotors do not dwell within a no-dwell zone comprising rotational speeds associated with one or more frequency aspects of the airframe.

First claim

What is claimed is:

1. A multi-rotor vehicle comprising:
an airframe;
a plurality of rotors coupled to the airframe; and
a controller, coupled to the airframe, configured to:
determine a rotational speed of each of the plurality of rotors; and
adjust the rotational speed of each of the plurality of rotors such that the rotors do not dwell within a no-dwell zone comprising rotational speeds associated with one or more frequency aspects of the airframe.

2. The multi-rotor vehicle of claim 1 , further comprising a memory, wherein the no-dwell zone is determined based on one or more frequency aspects of the airframe comprising one or more resonance frequencies of the airframe and a physical configuration of the airframe, and wherein no-dwell zone information is stored within the memory.

3. The multi-rotor vehicle of claim 1 , further comprising at least one first sensor, coupled to the airframe, configured to provide first sensor information associated with the rotational speed of each of the plurality of rotors, and wherein the controller is configured to receive the first sensor information to determine the rotational speed of each of the plurality of rotors.

4. The multi-rotor vehicle of claim 1 , further comprising at least one second sensor, coupled to the airframe, configured to provide second sensor information associated with a vibration of the airframe, wherein the controller is configured to monitor the second sensor information and adjust the rotational speed of each of the plurality of rotors such that the rotors do not dwell within the no-dwell zone based on the second sensor information.

5. The multi-rotor vehicle of claim 1 , wherein the plurality of rotors are oriented in one or more groups, wherein a first number of rotors oriented in a first group are substantially equal to a second number of rotors oriented in a second group, and wherein each one of the rotors in the first group are arranged symmetrically opposite a corresponding one of the rotors in the second group to provide a plurality of symmetrically opposite pairs of rotors relative to a center of gravity of the airframe.

6. The multi-rotor vehicle of claim 5 , wherein the plurality of rotors comprises six rotors, wherein the rotors are configured to rotate in a same rotational direction, and wherein the controller is configured to maintain a substantially equal rotational speed between the rotors of each of the plurality of symmetrically opposite pairs of rotors.

7. The multi-rotor vehicle of claim 5 , wherein the plurality of rotors comprises between three and twelve rotors, and wherein the symmetrically opposite pairs of rotors comprise between two and six symmetrically opposite pairs.

8. The multi-rotor vehicle of claim 5 , wherein the rotors of the first group rotate in a first rotational direction and the rotors of the second group rotate in a second rotational direction that is opposite the first rotational direction.

9. The multi-rotor vehicle of claim 5 , wherein the first group of rotors comprise a first trefoil configuration and the second group of rotors comprise a second trefoil configuration.

10. The multi-rotor vehicle of claim 9 , wherein the controller is further configured to provide a first commanded phasor angle to each of the rotors in the first trefoil configuration and a second commanded phasor angle to each of the rotors in the second trefoil configuration such that the rotational speeds of the opposite pairs of rotors are adjusted to cause at least one opposite pair of rotors with rotational speeds nearest the no-dwell zone to rapidly traverse the no-dwell zone, and wherein a mean angular velocity of the rotors is substantially constant during the traverse.

11. The multi-rotor vehicle of claim 10 , wherein the second commanded phasor angle comprises a direction opposite the first commanded phasor angle.

12. The multi-rotor vehicle of claim 10 , wherein the controller is configured to provide a third commanded phasor angle that is opposite the first commanded phasor angle to each of the rotors in the first trefoil configuration and a fourth commanded phasor angle that is opposite the second commanded phasor angle to each of the rotors in the second trefoil configuration, and wherein the third commanded phasor angle and the fourth commanded phasor angle are provided after the rotational speeds of each corresponding opposite pair of rotors are adjusted.

13. The multi-rotor vehicle of claim 1 , further comprising:
a third sensor, coupled to the airframe, comprising at least one of a video imaging camera system, a lidar imaging sensor, or a radar imaging sensor system configured to provide image information of an object approaching at least one of the plurality of rotors, wherein the controller is configured to:
process the image information to determine a position and a trajectory of the object approaching at least one of the plurality of rotors; and
adjust the rotational speed of the at least one of the plurality of rotors such that the rotors do not dwell within the no-dwell zone, and to minimize damage to the rotors by the object.

14. The multi-rotor vehicle of claim 13 , further comprising one or more control surfaces, coupled to the airframe, wherein the controller is configured to adjust the one or more control surfaces to maintain controlled flight of the multi-rotor vehicle.

15. A method of determining the no-dwell zone of claim 1 , the method comprising:
generating a plurality of rotational speeds by the plurality of rotors;
measuring a vibration at the airframe;
determining one or more resonance frequencies of the airframe based on the measured vibration; and
determining the no-dwell zone associated with one or more resonance frequencies of the airframe.

16. A method comprising:
determining a rotational speed of each of a plurality of rotors coupled to an airframe of a multi-rotor vehicle; and
adjusting the rotational speed of each of the plurality of rotors such that the rotors do not dwell within a no-dwell zone comprising rotational speeds associated with one or more frequency aspects of the airframe.

17. The method of claim 16 , further comprising:
determining the no-dwell zone based on one or more frequency aspects of the airframe comprising one or more resonance frequencies of the airframe and a physical configuration of the airframe; and
storing no-dwell zone information within a memory.

18. The method of claim 16 , further comprising providing first sensor information associated with the rotational speed of each of the plurality of rotors, wherein the determining comprises determining the rotational speed of each of the plurality of rotors based on the first sensor information.

19. The method of claim 16 , further comprising:
providing second sensor information associated with a vibration of the airframe;
monitoring the second sensor information; and
adjusting the rotational speed of each of the plurality of rotors such that the rotors do not dwell within the no-dwell zone based on the second sensor information.

20. The method of claim 16 , further comprising:
orienting the plurality of rotors in one or more groups, wherein a first number of rotors oriented in a first group are substantially equal to a second number of rotors oriented in a second group, wherein each one of the rotors in the first group are arranged symmetrically opposite a corresponding one of the rotors in the second group to provide a plurality of symmetrically opposite pairs of rotors relative to a center of gravity of

Assignees

• Boeing Co

Inventors

• Tillotson Brian J

Classifications

• H02P5/56 Primary

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• B64U2201/00

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• G06V20/13

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• B64D31/06

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• G08G5/80

  Anti-collision systems · CPC title