Operating aerial vehicles with intentionally imbalanced propellers

Patent metadata

Field	Value
Publication number	US-10214279-B2
Application number	US-201815904014-A
Country	US
Kind code	B2
Filing date	Feb 23, 2018
Priority date	Dec 18, 2015
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

Aerial vehicles may be operated with discrete sets of propellers, which may be selected for a specific purpose or on a specific basis. The discrete sets of propellers may be operated separately or in tandem with one another, and at varying power levels. For example, a set of propellers may be selected to optimize the thrust, lift, maneuverability or efficiency of an aerial vehicle based on a position or other operational characteristic of the aerial vehicle, or an environmental condition encountered by the aerial vehicle. At least one of the propellers may be statically or dynamically imbalanced, such that the propeller emits a predetermined sound during operation. A balanced propeller may be specifically modified to cause the aerial vehicle to emit the predetermined sound by changing one or more parameters of the balanced propeller and causing the balanced propeller to be statically or dynamically imbalanced.

First claim

What is claimed is:

1. A method comprising:
identifying information regarding at least one attribute of a mission for the aerial vehicle comprising a first motor;
predicting a noise to be emitted during a rotation of a first propeller above a critical speed of the first propeller, wherein the first propeller is statically balanced and dynamically balanced;
determining that at least one of a frequency spectrum of the noise or a sound pressure level of the noise is not consistent with the at least one attribute of the mission;
executing a modification to the first propeller, wherein the modified first propeller is at least one of statically imbalanced or dynamically imbalanced after executing the modification;
rotatably coupling the modified first propeller to a first shaft of the first motor; and
causing the aerial vehicle to perform the mission, wherein the causing the aerial vehicle to perform the mission comprises:
operating the first motor to rotate the modified first propeller above the critical speed of the first propeller during at least a portion of the mission.

2. The method of claim 1 , wherein the at least one attribute includes at least one of:
a location of an origin for the mission;
a location of a destination for the mission;
a location of an intervening waypoint between the origin and the destination;
at least one course to be traveled during the performance of the mission;
at least one air speed of the aerial vehicle required during the performance of the mission; or
a mass of a payload to be carried by the aerial vehicle during the mission.

3. The method of claim 1 , wherein a first center of mass of the modified first propeller is not aligned along an axis of rotation of the first shaft, and
wherein centrifugal forces acting upon each of a plurality of blades of the modified first propeller are not equal to or do not counteract one another when the modified first propeller is rotated above the critical speed.

4. The method of claim 1 , wherein the first propeller is one of a type of propeller, and
wherein predicting the noise to be emitted during the rotation of the first propeller above the critical speed of the first propeller comprises:
rotatably coupling a second propeller to a second shaft of a second motor, wherein the second propeller is one of the type of propeller, and wherein a critical speed of the second propeller is approximately the critical speed of the first propeller;
operating the first motor to rotate the second propeller above the critical speed;
capturing information regarding at least one sound emitted by the second propeller during rotation of the second propeller above the critical speed by the second motor; and
predicting the noise to be emitted during the rotation of the first propeller above the critical speed of the first propeller based at least in part on the information regarding the at least one sound emitted by the second propeller during the rotation of the second propeller above the critical speed by the second motor.

5. The method of claim 1 , wherein the aerial vehicle further comprises a second motor having a second propeller rotatably coupled to a second shaft of the second motor, and
wherein causing the aerial vehicle to perform the emission comprises:
prior to operating the first motor to rotate the modified first propeller above the critical speed of the first propeller during at least the portion of the mission,
operating the second motor to rotate the second propeller above a critical speed of the second propeller;
determining a position of the aerial vehicle;
determining that the position of the aerial vehicle is within a predetermined range of one of a location of an origin for the mission, a location of a destination for the mission or a location of an intervening waypoint between the origin and the destination;
in response to determining that the position of the aerial vehicle is within the predetermined range of one of the location of the origin, the location of the destination or the location of the intervening waypoint,
stopping the operation of the first motor; and
operating the first motor to rotate the modified first propeller above the critical speed of the first propeller.

6. The method of claim 1 , wherein the first propeller comprises a first blade and a second blade, and wherein executing the modification to the first propeller comprises at least one of:
removing a core from the second blade;
inserting a slug into the second blade, wherein a density of the slug is greater than a density of a material from which the second blade is formed;
drilling at least a first hole in the second blade; or
exposing, by a retractable cover disposed within the second blade, at least a second hole in the second blade; or
modifying at least one of a blade angle or a rake angle of the second blade.

7. A method comprising:
prior to an operation of an aerial vehicle, predicting an attribute of the aerial vehicle during the operation;
selecting a modification to a first propeller based at least in part on the predicted attribute;
modifying the first propeller in accordance with the selected modification, wherein the first propeller is statically balanced and dynamically balanced prior to modifying the first propeller in accordance with the selected modification, and wherein the modified first propeller is at least one of statically imbalanced or dynamically imbalanced;
coupling the modified first propeller to a first shaft of a first motor of the aerial vehicle; and
initiating the operation of the aerial vehicle, wherein the operation of the aerial vehicle comprises:
operating the first motor to rotate the first propeller above a critical speed at a first time.

8. The method of claim 7 , wherein a center of mass of the modified first propeller is not aligned with an axis of rotation of the first shaft after the modified first propeller has been coupled to the first shaft.

9. The method of claim 7 , wherein the predicted attribute is one of:
a predicted position of the aerial vehicle during the operation;
a predicted course of the aerial vehicle during the operation;
a predicted air speed of the aerial vehicle during the operation;
a predicted environmental condition around the aerial vehicle during the operation;
a predicted operating condition of the aerial vehicle during the operation; or
a predicted sound emitted by the aerial vehicle during the operation.

10. The method of claim 7 , wherein the first propeller is of a type of propeller, and
wherein the method further comprises:
prior to modifying the first propeller,
rotating a second propeller above the critical speed, wherein the second propeller is of the type of propeller;
capturing information regarding a first sound emitted by the second propeller while rotating above the critical speed, wherein the information regarding the first sound comprises at least one of a first frequency spectrum of the first sound or a first sound pressure level of the first sound;
determining that at least one of the first frequency spectrum or the first sound pressure level is not acceptable based at least in part on the predicted attribute of the aerial vehicle during the operation and the information regarding the first sound; and
selecting the modification based at least in part on the first frequency spectrum or the first sound pressure level.

11. The method of claim 10 , wherein determining that the at least one of the first frequency spectrum or the first sound pressure level is not acceptable based at least in part on the predicted attribute of the aerial vehicle during the operation comprises:
identifying informatio

Assignees

• Amazon Tech Inc

Inventors

• Beckman Brian C
• Ko Allan

Classifications

• B64U2201/10

  autonomous, i.e. by navigating independently from ground or air stations, e.g. by using inertial navigation systems [INS] · CPC title

• B64C2201/027

  Operations & Transport · mapped topic

• G05D1/101

  specially adapted for aircraft · CPC title

• B64C11/00 Primary

  Propellers, e.g. of ducted type; Features common to propellers and rotors for rotorcraft · CPC title

• B64C2201/141

  Operations & Transport · mapped topic