Unmanned aerial vehicle motor driving randomization and feedback for noise abatement

• US 9,415,870 B1
• Filed: 09/02/2015
• Issued: 08/16/2016
• Est. Priority Date: 09/02/2015
• Status: Active Grant

• Current Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Original Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Inventors: Hensel, Fabian, Beckman, Brian C., Kalyan, Atishkumar, Kimchi, Gur
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): Lee, Tyler J
• Application Number:
  US14/843,635
• Time in Patent Office: 349 Days
• Field of Search: 701 1- 18
• US Class Current: 1/1
• CPC Class Codes: B64C 2220/00 Active noise reduction systems
• CPC Class Codes: B64D 31/12 for equalising or synchronising power plants
• CPC Class Codes: B64U 10/10 Rotorcrafts
• CPC Class Codes: B64U 10/13 Flying platforms
• CPC Class Codes: B64U 20/20 for noise reduction
• CPC Class Codes: B64U 20/65 Composite materials
• CPC Class Codes: B64U 2101/60 for transporting passengers; for transporting goods other than weapons
• CPC Class Codes: B64U 2101/64 for parcel delivery or retrieval
• 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 30/20 Rotors; Rotor supports
• CPC Class Codes: B64U 30/29 Constructional aspects of rotors or rotor supports; Arrangements thereof
• CPC Class Codes: B64U 50/19 using electrically powered motors

Abstract

This disclosure is directed to monitoring a noise signature of an unmanned aerial vehicle (UAV) and varying the speed of the motors of the UAV to reduce unwanted sound (i.e., noise) of the UAV based on the noise signature. The noise signature of the UAV may be measured by an audio sensor of a vibration sensor, and feedback may be provided to the UAV. The UAV may generate noise during flight, which may include a number of noise components such as tonal noise (e.g., a whining noise such as a whistle of a kettle at full boil) and broadband noise (e.g., a complex mixture of sounds of different frequencies, such as the sound of ocean surf). By measuring the noise signature of the UAV, and varying the motor revolutions per minute (RPM) during flight operations, the UAV may reduce tonal components of the UAV noise signature.

Claims

1. An unmanned aerial vehicle (UAV) configured to deliver a package, the UAV comprising:

a frame;

a plurality of motors including at least a first motor and a second motor, each motor coupled to the frame and configured to rotate at least one propeller to cause lift and propulsion for the UAV;

a power source to selectively provide power to the plurality of motors;

an audio sensor to measure a tonal component of sound generated by propellers of the UAV;

a control system in communication with at least the plurality of motors and the power source, the control system to control at least operation of the plurality of motors, the control system to perform operations comprising;

determining a flight control of the UAV, the flight control of the UAV including at least a heading and a velocity of the UAV;

determining a first motor speed of the first motor of the UAV, wherein the first motor speed is based in part on the flight control of the UAV;

determining a second motor speed of at least the second motor of the UAV, wherein the second motor speed is based in part on the flight control of the UAV;

a closed-loop noise controller configured to perform operations comprising;

determining that the UAV is operating in a noise-sensitive location;

receiving a first audio signal from the audio sensor at a first time indicating a first tonal component of the sound generated by the propellers of the UAV;

calculating a first randomization motor speed by applying a first random value within a randomization threshold to the first motor speed;

sending the first randomization motor speed to the control system to control operation of at least the first motor;

receiving a second audio signal from the audio sensor at a second time indicating a second tonal component of the sound generated by the propellers operating using the first randomization motor speed;

determining that a second amplitude of the second tonal component is greater than a first amplitude of the first tonal component;

calculating a second randomization motor speed by applying a second random value within the randomization threshold to the first motor speed; and

sending the second randomization motor speed to the control system to control operation of at least the first motor.

2. The UAV of claim 1, wherein the closed-loop controller is further configured to perform operations comprising:

receiving a third audio signal from the audio sensor at a third time indicating a third tonal component of the sound generated by the propellers operating using the second randomization motor speed;

determining that a third amplitude of the third tonal component is less than the second amplitude of the second tonal component; and

refraining from calculating another randomization motor speed for at least a predetermined amount of time.

3. The UAV of claim 1, wherein the randomization threshold comprises an upper threshold value and a lower threshold value for the first motor speed based on the flight control of the UAV.

4. The UAV of claim 1, wherein the closed-loop noise controller is further configured to perform operations comprising changing the second motor speed to an adjusted second motor speed to compensate for use of the second randomized motor speed by at least the first motor.

5. The UAV of claim 1, wherein the calculating the first randomization motor speed includes applying a motor speed pattern designed to reduce a tonal quality of a noise signature of the UAV.

6. The UAV of claim 1, wherein the closed-loop noise controller is further configured to perform operations comprising:

determining that the UAV is outside of a position threshold for an intended flight path; and

driving the plurality of motors of the UAV to within the position threshold.

7. A processor-implemented method comprising:

determining a flight control of an unmanned aerial vehicle (UAV), the flight control of the UAV including at least a heading and a velocity of the UAV;

determining a first motor speed of the first motor of the UAV, wherein the first motor speed is based in part on the flight control of the UAV;

receiving, from one or more audio sensors, a first audio sensor signal at a first time indicating that a first tonal component of a first noise signature of the UAV operating at the first motor speed is greater than a threshold tonal noise value;

changing the first motor speed to a first adjusted motor speed by randomly selecting the first adjusted motor speed within a randomization threshold; and

causing the UAV to operate using the first adjusted motor speed.

8. The processor-implemented method of claim 7, further comprising:

changing the first adjusted motor speed to a second adjusted motor speed by randomly selecting the second adjusted motor speed within the randomization threshold;

receiving, from the one or more audio sensors, a second audio sensor signal at a second time indicating that a second tonal component of a second noise signature of the UAV operating at the second adjusted motor speed is less than the threshold tonal noise value; and

refraining from calculating another randomization motor speed for at least a predetermined amount of time.

9. The processor-implemented method of claim 7, further comprising determining that the UAV is operating in a noise-sensitive location.

10. The processor-implemented method of claim 7, wherein the receiving the first audio sensor signal at the first time further indicates that a first broadband component of the first noise signature of the UAV operating using the first motor speed is greater than a threshold broadband noise value.

11. The processor-implemented method of claim 7, wherein the one or more audio sensors are coupled to the UAV.

12. The processor-implemented method of claim 7, further comprising receiving vibration feedback from a vibration sensor coupled to the UAV.

13. The processor-implemented method of claim 7, further comprising shifting a weight or a ballast in the UAV based at least in part on a difference between the first motor speed and the first adjusted motor speed.

14. The processor-implemented method of claim 13, further comprising:

determining that the first motor speed and the second motor speed are approximately a same motor speed or are within a threshold speed variance; and

changing the second motor speed to an adjusted second motor speed based in part on the first audio sensor signal.

15. The processor-implemented method of claim 7, further comprising changing the first adjusted motor speed to a second adjusted motor speed at a second time, wherein the second time is a random amount of time after the first time.

16. The processor-implemented method of claim 7, further comprising determining that a remaining power resource of the UAV is above a remaining power resource threshold prior to the changing the first motor speed to the first adjusted motor speed.

17. The processor-implemented method of claim 7, further comprising:

determining that the UAV is outside of a position threshold for an intended flight path; and

driving a plurality of motors of the UAV to navigate the UAV towards the intended flight path or within the position threshold.

18. An unmanned aerial vehicle (UAV) comprising:

one or more processors;

memory coupled to the one or more processors, the memory including one or more modules that are executable by the one or more processors to perform operations comprising;

determining a flight control of the UAV, the flight control of the UAV including at least a heading and a velocity of the UAV;

receiving, from one or more sensors coupled to the UAV, first sensor feedback at a first time indicating a first tonal component of a first noise signature of the UAV;

determining a first motor speed of the first motor of the UAV, wherein the first motor speed is based in part on the flight control of the UAV;

changing the first motor speed to a first adjusted motor speed by randomly selecting the first adjusted motor speed within a randomization threshold;

receiving, from the one or more sensors coupled to the UAV, second sensor feedback at a second time indicating a second tonal component of a second noise signature of the UAV;

comparing a second amplitude of the second tonal component of the second noise signature to a first amplitude of the first tonal component of the first noise signature;

determining that the second amplitude of the second tonal component of the second noise signature is greater than the first amplitude of the first tonal component of the first noise signature; and

changing the first adjusted motor speed to a second adjusted motor speed by randomly selecting the second adjusted motor speed within the randomization threshold.

19. The UAV of claim 18, wherein the operations further comprise determining that the UAV is operating in a noise-sensitive location.

20. The UAV of claim 18, wherein the operations further comprise:

receiving, from the one or more sensors coupled to the UAV, third sensor feedback at a third time indicating a third tonal component of a third noise signature of the UAV;

determining that a third amplitude of the third tonal component of the third noise signature is less than the second amplitude of the second tonal component of the second noise signature; and

refraining from calculating another adjusted motor speed for at least a predetermined amount of time.