Multi-rotor tonal noise control for UAV

Patent metadata

Field	Value
Publication number	US-10946953-B2
Application number	US-201715849365-A
Country	US
Kind code	B2
Filing date	Dec 20, 2017
Priority date	Dec 20, 2017
Publication date	Mar 16, 2021
Grant date	Mar 16, 2021

Abstract

A technique of controlling tonal noises produced by an unmanned aerial vehicle (UAV) includes generating thrust with a plurality of rotor units mounted to the UAV to propel the UAV into flight. Each of the rotor units includes a bladed rotor. A rotation rate or a phase delay of at least one of the rotor units is adjusted relative to another of the rotor units. The adjustment causes a spread in the tonal noises generated by the rotor units.

First claim

What is claimed is:

1. An unmanned aerial vehicle (UAV), comprising:
a UAV body;
a plurality of rotor units mounted to the UAV body, each of the rotor units including a bladed rotor that rotates to generate thrust; and
a control system coupled to each of the rotor units to control rotation of the bladed rotor of each of the rotor units, wherein the control system includes a controller with logic that, when executed by the controller, will cause the UAV to perform operations including:
adjusting at least one of a rotation rate or a phase delay of at least one of the rotor units relative to another of the rotor units, wherein adjusting the at least one of the rotation rate or the phase delay causes a spread in tonal noises generated by the rotor units,

wherein adjusting at least one of the rotation rate or the phase delay comprises offsetting phase delays of the rotor units relative to each other to offset phases of peak amplitudes of the tonal noises generated by different ones of the rotor units from each other,
wherein offsetting the phase delays of the rotor units relative to each other comprises:
determining a revolution frequency for one or more of the rotor units to determine a rotation period for the one or more of the rotor units;
dividing the rotation period by a number N of the rotor units to generate a phase delay value; and
phase delaying each of the number N of the rotor units by a different integer multiple of the phase delay value.

2. The UAV of claim 1 , wherein the number N comprises a total number of the rotor units mounted to the UAV body.

3. The UAV of claim 1 , wherein offsetting the phase delays of the rotor units relative to each other further comprises:
grouping the plurality of rotor units into noise generating subgroups (i) based upon proximity of the rotor units to each other;
generating a phase delay value D(i) for each of the noise generating subgroups (i) based upon a number N(i) of the rotors in each of the noise generating subgroups (i); and
phase delaying each of the rotor units within a given one of the noise generating subgroups (i) relative to other ones of the rotor units within the given one of the noise generating subgroups (i) by a different integer multiple of the phase delay value D(i).

4. The UAV of claim 3 , wherein the UAV body includes a wing assembly and first and second boom assemblies mounted to the wing assembly and wherein the rotor units are mounted to the first and second boom assemblies, wherein the rotor units mounted to the first boom assembly fore of the wing assembly comprise a first one of the noise generating subgroups (i), the rotor units mounted to the first boom assembly aft of the wing assembly comprise a second one of the noise generating subgroups (i), the rotor units mounted to the second boom assembly fore of the wing assembly comprise a third one of the noise generating subgroups (i), and the rotor units mounted to the second boom assembly aft of the wing assembly comprise a fourth one of the noise generating subgroups (i).

5. The UAV of claim 1 , wherein offsetting the phase delays of the rotor units relative to each other further comprises:
updating the phase delay value in real-time based upon changes in the revolution frequency of the one or more of the rotor units.

6. The UAV of claim 1 , wherein determining the revolution frequency for the one or more of the rotor units comprises monitoring one or both of a voltage or a current driving the one or more of the rotor units in real-time and wherein phase delaying each of the rotor units comprises adjusting a pulse width modulation of each of the rotor units in real-time.

7. The UAV of claim 1 , wherein adjusting at least one of the rotation rate or the phase delay comprises varying rotation rates of the rotor units relative to each other to spectrally spread out component frequencies of the tonal noises collectively generated by the rotor units.

8. The UAV of claim 7 , wherein one or more of the rotor units have different physical geometries relative to each other such that different rotation rates for different ones of the rotor units produce a common amount of thrust.

9. The UAV of claim 8 , wherein the different physical geometries includes differences in one or more of a diameter of the bladed rotor, a surface area of the bladed rotor, a pitch of the bladed rotor, or a number of blades on the bladed rotor.

10. The UAV of claim 7 , wherein varying the rotation rates of the rotor units relative to each other comprises varying the rotation rates in groups of the rotor units to spectrally spread out the component frequencies of the tonal noises while maintaining flight stability.

11. The UAV of claim 7 , wherein varying the rotation rates of the rotor units relative to each other to spectrally spread out the component frequencies of the tonal noises comprises introducing a gyroscopic wobble about a stabilized center of the UAV by dynamically modulating the rotation rates of different ones of the rotor units.

12. The UAV of claim 1 , wherein the controller includes further logic that, when executed by the controller, will cause the UAV to perform additional operations including:
dynamically modulating the rotation rates of the rotor units to generate a melody with the tonal noises generated by the rotor units, wherein the melody comprises arranging the tonal noises to an acoustical beat;
associating the melody with a particular flight phase;
generating the melody with the rotor units while the UAV is operating in the particular flight phase; and
producing different melodies for different flight phases.

13. The UAV of claim 12 , wherein the particular flight phase comprises one of an arrival phase, a departure phase, or a transit phase.

14. The UAV of claim 1 , further comprising:
generating chords with the tonal noises by varying the rotation rates between the rotor units.

15. A method of controlling tonal noises produced by an unmanned aerial vehicle (UAV), the method comprising:
generating thrust with a plurality of rotor units mounted to the UAV to propel the UAV into flight, each of the rotor units including a bladed rotor; and
adjusting at least one of a rotation rate or a phase delay of at least one of the rotor units relative to one or more others of the rotor units, wherein adjusting the at least one of the rotation rate or the phase delay causes a spread in the tonal noises generated by the rotor units,
wherein adjusting at least one of the rotation rate or the phase delay comprises varying rotation rates of the rotor units relative to each other to spectrally spread out component frequencies of the tonal noises collectively generated by the rotor units,
wherein one or more of the rotor units have different physical geometries relative to each other such that different rotation rates for different ones of the rotor units produce a common amount of thrust.

16. The method of claim 15 , wherein adjusting at least one of the rotation rate or the phase delay comprises offsetting phase delays of the rotor units relative to each other to offset phases of peak amplitudes of the tonal noises generated by different ones of the rotor units from each other.

17. The method of claim 16 , wherein offsetting the phase delays of the rotor units relative to each other comprises:
determining a revolution frequency for one or more of the rotor units to determine a rotation period for the one or more of the rotor units;
dividing the rotation period by a number N of the rotor units to generate a phase delay value; and
phase delaying each of the

Assignees

• Wing Aviation Llc

Inventors

• Pantalone Giulia
• Woodworth Adam
• Teller Eric
• Kim Ealgoo
• Huffman Jacob
• Kubie Martin

Classifications

• B64U2201/20

  Remote controls · CPC title

• B64U2201/10

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

• B64D31/06

  actuated automatically · CPC title

• B64U2101/30

  for imaging, photography or videography · CPC title

• B64U2101/60

  for transporting passengers; for transporting goods other than weapons · CPC title