# US 11,053,017 B1 · Rotor noise reduction using signal processing

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- Number: US 11,053,017 B1
- Document ID: US11053017B1
- Status: Granted
- Kind: B1
- Application number: 16/998,241
- Filed: 2020-08-20
- Granted: 2021-07-06
- Earliest claimed: 2020-08-20
- Assignees: Kitty Hawk Corporation
- Applicants: Kitty Hawk Corporation
- Inventors: Cameron Robertson
- Web page: https://patentgrep.com/patent/US11053017B1

## CPC

- B64C 29/0025: {the propellers being fixed relative to the fuselage}
- B64D 31/06: actuated automatically
- G10K 11/175: using interference effects; Masking sound
- G10K 11/1752: {Masking}
- H02P 5/52: additionally providing control of relative angular displacement
- H02P 5/74: controlling two or more AC dynamo-electric motors (H02P5/46, H02P5/60 take precedence)
- H02P 23/06: Controlling the motor in four quadrants
- B64C 2220/00: Active noise reduction systems
- G10K 2210/123: Synchrophasors or other applications where multiple noise sources are driven with a particular phase relationship
- B64C: AEROPLANES; HELICOPTERS
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

A vehicle which includes a flight controller that is configured to receive one or more desired forces or moments associated with a plurality of rotors in the vehicle and determine a plurality of motor control signals for the plurality of rotors based at least in part on the desired forces or moments and an expected rotor noise produced by at least one of the plurality of rotors. The vehicle further includes the plurality of rotors, where the plurality of motor control signals is used to control the plurality of rotors.

## Claims

### Claim 1

A vehicle, comprising:
a flight controller that is configured to:
receive one or more desired forces or moments associated with a plurality of rotors in the vehicle;
determine a plurality of motor control signals for the plurality of rotors based at least in part on the desired forces or moments, including by performing thrust allocation using a feed-forward, multi-function thrust allocation optimization block that finds the plurality of motor control signals that achieve the desired forces and moments and optimize a plurality of cost functions, including a control authority function and a noise function;
determine if a moving window of past motor control signals satisfies a steady state criteria, wherein it is a necessary condition that the moving window of past motor control signals satisfies the steady state criteria in order for the plurality of motor control signals to be determined based at least in part on the desired forces or moments, including by performing thrust allocation using the feed-forward, multi-function thrust allocation optimization block; and
in the event it is determined that the moving window of past motor control signals does not satisfy the steady state criteria, determine the plurality of motor control signals based at least in part on the desired forces or moments and without the feed-forward, multi-function thrust allocation optimization block taking into account the noise function; and
the plurality of rotors, wherein the plurality of motor control signals is used to control the plurality of rotors.

### Claim 2 (depends on 1)

The vehicle of claim 1, wherein the vehicle includes a vertical takeoff and landing (VTOL) multicopter.

### Claim 3 (depends on 1)

The vehicle of claim 1, wherein the flight controller is further configured to:
determine if the vehicle is located in a defined space, wherein it is a necessary condition that the vehicle be located in the defined space in order for the plurality of motor control signals to be determined based at least in part on the desired forces or moments, including by performing thrust allocation using the feed-forward, multi-function thrust allocation optimization block; and
in the event it is determined that the vehicle is not located in the defined space, determine the plurality of motor control signals based at least in part on the desired forces or moments and without the feed-forward, multi-function thrust allocation optimization block taking into account the noise function.

### Claim 4 (depends on 1)

The vehicle of claim 1, wherein the flight controller is further configured to:
determine if the vehicle is located in a defined space, wherein:
it is a necessary condition that the vehicle be located in the defined space in order for the plurality of motor control signals to be determined based at least in part on the desired forces or moments and, including by performing thrust allocation using the feed-forward, multi-function thrust allocation optimization block; and
the defined space has a maximum velocity that is automatically enforced and the automatically-enforced maximum velocity is slower than a second automatically-enforced maximum velocity associated with a second defined space that is mutually exclusive with the defined space; and
in the event it is determined that the vehicle is not located in the defined space, determine the plurality of motor control signals based at least in part on the desired forces or moments and without the feed-forward, multi-function thrust allocation optimization block taking into account the noise function.

### Claim 5 (depends on 1)

The vehicle of claim 1, wherein the flight controller is further configured to:
determine if a battery level satisfies a minimum battery level, wherein it is a necessary condition that the battery level satisfies the minimum battery level in order for the plurality of motor control signals to be determined based at least in part on the desired forces or moments, including by performing thrust allocation using the feed-forward, multi-function thrust allocation optimization block; and
in the event it is determined that the battery level does not satisfy the minimum battery level, determine the plurality of motor control signals based at least in part on the desired forces or moments and without the feed-forward, multi-function thrust allocation optimization block taking into account the noise function.

### Claim 6 (depends on 1)

The vehicle of claim 1, wherein:
the vehicle includes an autonomously flown vehicle; and
an autonomous flight control system included in the autonomously flown vehicle generates a noise reduced trajectory based at least in part on an expected rotor noise produced by at least one of the plurality of rotors.

### Claim 7 (depends on 1)

The vehicle of claim 1, wherein:
the vehicle includes an piloted vehicle; and
the piloted vehicle includes a hand control and an input shaper, wherein the input shaper inputs a raw input signal from the hand control that generates a shaped and noise reduced input signal.

### Claim 8

A method, comprising:
receiving one or more desired forces or moments associated with a plurality of rotors in a vehicle;
determining a plurality of motor control signals for the plurality of rotors based at least in part on the desired forces or moments, including by:
performing thrust allocation using a feed-forward, multi-function thrust allocation optimization block that finds the plurality of motor control signals that achieve the desired forces and moments and optimize a plurality of cost functions, including a control authority function and a noise function;
determining if a moving window of past motor control signals satisfies a steady state criteria, wherein it is a necessary condition that the moving window of past motor control signals satisfies the steady state criteria in order for the plurality of motor control signals to be determined based at least in part on the desired forces or moments, including by performing thrust allocation using the feed-forward, multi-function thrust allocation optimization block; and
in the event it is determined that the moving window of past motor control signals does not satisfy the steady state criteria, determining the plurality of motor control signals based at least in part on the desired forces or moments and without the feed-forward, multi-function thrust allocation optimization block taking into account the noise function; and
controlling the plurality of rotors using the plurality of motor control signals.

### Claim 9 (depends on 8)

The method of claim 8, wherein the vehicle includes a vertical takeoff and landing (VTOL) multicopter.

### Claim 10 (depends on 8)

The method of claim 8, wherein determining the plurality of motor control signals includes:
determining if the vehicle is located in a defined space, wherein it is a necessary condition that the vehicle be located in the defined space in order for the plurality of motor control signals to be determined based at least in part on the desired forces or moments, including by performing thrust allocation using the feed-forward, multi-function thrust allocation optimization block; and
in the event it is determined that the vehicle is not located in the defined space, determining the plurality of motor control signals based at least in part on the desired forces or moments and without the feed-forward, multi-function thrust allocation optimization block taking into account the noise function.

### Claim 11 (depends on 8)

The method of claim 8, wherein determining the plurality of motor control signals includes:
determining if the vehicle is located in a defined space, wherein:
it is a necessary condition that the vehicle be located in the defined space in order for the plurality of motor control signals to be determined based at least in part on the desired forces or moments, including by performing thrust allocation using the feed-forward, multi-function thrust allocation optimization block; and
the defined space has a maximum velocity that is automatically enforced and the automatically-enforced maximum velocity is slower than a second automatically-enforced maximum velocity associated with a second defined space that is mutually exclusive with the defined space; and
in the event it is determined that the vehicle is not located in the defined space, determining the plurality of motor control signals based at least in part on the desired forces or moments and without the feed-forward, multi-function thrust allocation optimization block taking into account the noise function.

### Claim 12 (depends on 8)

The method of claim 8, wherein determining the plurality of motor control signals includes:
determining if a battery level satisfies a minimum battery level, wherein it is a necessary condition that the battery level satisfies the minimum battery level in order for the plurality of motor control signals to be determined based at least in part on the desired forces or moments, including by performing thrust allocation using the feed-forward, multi-function thrust allocation optimization block; and
in the event it is determined that the battery level does not satisfy the minimum battery level, determining the plurality of motor control signals based at least in part on the desired forces or moments and without the feed-forward, multi-function thrust allocation optimization block taking into account the noise function.

### Claim 13 (depends on 8)

The method of claim 8, wherein:
the vehicle includes an autonomously flown vehicle; and
an autonomous flight control system included in the autonomously flown vehicle generates a noise reduced trajectory based at least in part on an expected rotor noise produced by at least one of the plurality of rotors.

### Claim 14 (depends on 8)

The method of claim 8, wherein:
the vehicle includes an piloted vehicle; and
the piloted vehicle includes a hand control and an input shaper, wherein the input shaper inputs a raw input signal from the hand control that generates a shaped and noise reduced input signal.

### Claim 15

A computer program product embodied in a non-transitory computer readable medium and comprising computer instructions for:
receiving one or more desired forces or moments associated with a plurality of rotors in a vehicle;
determining a plurality of motor control signals for the plurality of rotors based at least in part on the desired forces or moments, including by:
performing thrust allocation using a feed-forward, multi-function thrust allocation optimization block that finds the plurality of motor control signals that achieve the desired forces and moments and optimize a plurality of cost functions, including a control authority function and a noise function;
determining if a moving window of past motor control signals satisfies a steady state criteria, wherein it is a necessary condition that the moving window of past motor control signals satisfies the steady state criteria in order for the plurality of motor control signals to be determined based at least in part on the desired forces or moments, including by performing thrust allocation using the feed-forward, multi-function thrust allocation optimization block; and
in the event it is determined that the moving window of past motor control signals does not satisfy the steady state criteria, determining the plurality of motor control signals based at least in part on the desired forces or moments and without the feed-forward, multi-function thrust allocation optimization block taking into account the noise function; and
controlling the plurality of rotors using the plurality of motor control signals.