Unmanned aerial vehicle motor driving randomization for noise abatement

• US 9,802,702 B1
• Filed: 08/02/2016
• Issued: 10/31/2017
• 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: Beckman, Brian C., Hensel, Fabian, Kalyan, Atishkumar, Kimchi, Gur
• Primary Examiner(s): Lee, Tyler J
• Application Number:
  US15/226,492
• Time in Patent Office: 455 Days
• Field of Search: 701 3, 701 23
• CPC Class Codes: B64C 2220/00 Active noise reduction systems
• CPC Class Codes: B64C 39/024 of the remote controlled vehicle type, i.e. RPV
• CPC Class Codes: B64U 10/10 Rotorcrafts
• CPC Class Codes: B64U 10/13 Flying platforms
• CPC Class Codes: B64U 20/40 Modular UAVs
• 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 2201/00 UAVs characterised by their flight controls
• CPC Class Codes: B64U 30/20 Rotors; Rotor supports
• CPC Class Codes: B64U 50/19 using electrically powered motors

Abstract

This disclosure is directed to varying a speed of one or more motors in an unmanned aerial vehicle (UAV) to reduce unwanted sound (i.e., noise) of the UAV. A UAV may include motors coupled with propellers to provide lift and propulsion to the UAV in various stages of flight, such as while ascending, descending, hovering, or transiting. The motors and propellers may generate noise, 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 varying the controls to the motors, such as by varying the speed or revolutions per minute (RPM) of a motor during operation by providing random or pseudo-random RPM variations, the UAV may generate a noise signature with reduced tonal noise.

Claims

1. 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;

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

generating a first random value within a randomization threshold, the randomization threshold being an allowable deviation from the flight control of the UAV;

determining a randomized motor speed based at least in part by applying the first random value to the first motor speed; and

driving the first motor of the UAV at the randomized motor speed.

2. The processor-implemented method of claim 1, wherein applying the first random value to the first motor speed includes increasing or decreasing the first motor speed by the first random value.

3. The processor-implemented method of claim 1, further comprising:

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

changing at least the second motor speed to an adjusted second motor speed based in part on the determining that the first motor speed and at least the second motor speed are approximately the same motor speed or are within the threshold speed variance.

4. The processor-implemented method of claim 1, further comprising:

decreasing the first motor speed by the first random value;

generating a second random value within the randomization threshold; and

increasing at least a second motor speed for at least a second motor of the UAV by the second random value.

5. The processor-implemented method of claim 1, 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 randomized motor speed.

6. The processor-implemented method of claim 1, further comprising determining that a remaining power resource of the UAV is above a remaining power resource threshold.

7. The processor-implemented method of claim 1, wherein the driving the first motor at the randomized motor speed occurs during a first time period, and further comprising:

determining an updated motor speed based on a new flight control; and

driving the first motor of the UAV at the updated motor speed during a second time period.

8. The processor-implemented method of claim 7, wherein the second time period is a random amount of time after the first time period.

9. The processor-implemented method of claim 1, further comprising determining a payload characteristic of the UAV, wherein the randomization threshold is based in part on the payload characteristic of the UAV.

10. The processor-implemented method of claim 1, further comprising determining that the UAV is operating in a noise-sensitive location prior to the driving the first motor of the UAV at the randomized motor speed.

11. An unmanned aerial vehicle (UAV) comprising:

one or more processors; and

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;

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

generating a first random value within a randomization threshold, the randomization threshold based in part on the flight control of the UAV;

determining a randomized motor speed by applying the first random value to the first motor speed; and

causing the first motor of the UAV to operate at the randomized motor speed.

12. The UAV of claim 11, wherein applying the first random value to the first motor speed includes increasing or decreasing the first motor speed by the first random value.

13. The UAV of claim 11, wherein driving the first motor at the randomized motor speed is performed for a predetermined time period;

and

wherein the operations further comprise;

determining an updated motor speed based on a new flight control; and

applying the updated motor speed to the first motor of the UAV after the predetermined time period.

14. The UAV of claim 11, wherein the determining the randomized motor speed includes applying a motor speed pattern designed to reduce a tonal quality of a noise signature of the UAV.

15. The UAV of claim 11, wherein the operations further comprise determining that the UAV is operating in a noise-sensitive location.

16. An unmanned aerial vehicle (UAV) comprising:

one or more processors; and

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;

setting a motor speed of a motor of the UAV;

generating a random value within a randomization threshold;

determining a randomized motor speed by applying the random value to the motor speed;

causing the motor of the UAV to operate at the randomized motor speed; and

determining that the UAV is operating within a position threshold associated with a flight path.

17. The UAV of claim 16, wherein the operations further comprise determining at least a portion of the flight path overlaps with at least one noise-sensitive location.

18. The UAV of claim 16, wherein the random value is a first random value, wherein the randomized motor speed is a first randomized motor speed, and wherein the operations further comprise:

operating the motor of the UAV at the first randomized motor speed for a first time period;

generating a second random value within the randomization threshold;

determining a second randomized motor speed by applying the second random value to the motor speed; and

causing the motor of the UAV to operate at the second randomized motor speed for a second time period after the first time period.

19. The UAV of claim 16, wherein the operations further comprise:

determining that the UAV is operating outside the position threshold associated with the flight path;

determining a corrective motor speed to operate the motor of the UAV; and

causing the motor of the UAV to operate at the corrective motor speed to return the UAV within the position threshold associated with the flight path.

20. The UAV of claim 16, wherein the motor of the UAV is a first motor of the UAV, wherein the motor speed is a first motor speed, wherein the random value is a first random value, wherein the randomized motor speed is a first randomized motor speed, and wherein the operations further comprise:

determining a second motor speed of a second motor of the UAV;

generating a second random value within the randomization threshold;

determining a second randomized motor speed by applying the second random value to the second motor speed; and

causing the second motor of the UAV to operate at the second randomized motor speed.