Patent Description:
The overall success of the UAM (urban air mobility) market may be tied to noise reduction. Noise reduction may be a vital component for community acceptance.

Hence, it is desirable to provide systems and methods for noise reduction in aerial vehicles. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. <CIT>, <CIT>, <CIT>, <CIT> disclose UAV with a noise reduction concept. <CIT> discloses is a system for controlling acoustic radiation from an aircraft. The system comprising a plurality of rotor systems (one or more) and a noise controller configured to regulate acoustic radiation from the plurality of rotor systems. The noise controller can be configured to regulate a commanded flight setting from the flight control system and to output a regulated flight setting to the plurality of rotor systems. Based on the regulated flight setting, the plurality of rotor systems are configured to generate, individually and in aggregate, acoustic radiation having a target acoustic behavior.

A noise reduction system in a vertical takeoff and landing (VTOL) vehicle is provided according to claim <NUM>.

A method in a vertical takeoff and landing (VTOL) vehicle for reducing the level of noise output is provided according to claim <NUM>.

The subject matter described herein discloses apparatus, systems, techniques and articles for noise reduction systems in aerial vehicles. To achieve noise reduction goals, unique noise cancelling / mitigation methods are introduced that can affect both the vehicle and vertiport noise levels and incorporate novel algorithm-based techniques versus traditional motor and propeller design approaches to noise reduction.

<FIG> is a block diagram depicting an example VTOL (vertical takeoff and landing) flight system <NUM> in a VTOL vehicle that includes a Noise Signature Proximity Warning System (NPWS) <NUM> for selectively employing noise mitigation efforts. The example VTOL vehicle may be an eVTOL (electric vertical takeoff and landing) vehicle that is powered by batteries as the primary energy source to provide electrical power or a hVTOL (hybrid vertical takeoff and landing) vehicle. A hVTOL may utilize as an energy source to produce electrical power: batteries and hydrogen fuel (energy source) coupled with a fuel cell to generate electricity to power the vehicle; batteries and hydrocarbon fuel (energy source such as jet fuel) to power a Gas Turbine Engine that is coupled with an electrical generator to produce electrical power for the vehicle; or other energy source combinations (or hybrids) can be envisioned to produce electrical power to ultimately provide power to the electric propulsion system (motor[s], fan[s], and/or propeller[s], and associated controllers]) that could contribute to the noise signature produced by the vehicle. The example VTOL flight system <NUM> includes a vehicle management computer <NUM>, a flight control computer <NUM>, and a motor/battery control system <NUM>.

The vehicle management computer <NUM>, which provides processing resources for flight control modules, display control modules, an onboard storage module, and/or a communication control module, is configured to manage vehicle management functions, is coupled to a display system <NUM> for displaying vehicle management features to flight crew, and is configured to receive flight guidance and control data <NUM> and weather/traffic/Vertiport status data <NUM>, via a high speed data link <NUM>, for use in performing its vehicle management functions. Additionally, the vehicle management computer <NUM> is configured to receive noise critical geographical locations data <NUM> for use by the NPWS <NUM> to determine when to employ noise mitigation efforts.

The flight control computer <NUM>, which actuates the primary flight control surfaces to drive the flight path of the aircraft while also providing finer control for stability, receives location/altitude/speed data <NUM> from an onboard global positioning system (GPS) <NUM> and/or inertial measurement unit (IMU) <NUM> via a navigation subsection <NUM> and weather/speed/altitude data <NUM> via an external sensor suite <NUM>. The flight control computer <NUM> is communicatively coupled to the vehicle management computer <NUM> and also receives flight envelope vehicle noise characteristics data for use by the NPWS <NUM> to determine when to employ noise mitigation efforts.

The motor/battery control system <NUM> generates control signals <NUM> for individually controlling the fan RPM and pitch for each of the plurality of motors and fans <NUM> on the VTOL vehicle. The motor/battery control system <NUM> is communicatively coupled to the flight control computer <NUM> and receives battery and fan status data <NUM> from the plurality of motors and fans <NUM>.

The NPWS <NUM> may reside in and be implemented by the vehicle management computer <NUM>, the flight control computer <NUM>, or some other processing element on the VTOL. The NPWS <NUM> computes power modulations (e.g., realized in propeller RPM) to be made at each individual motor (from the plurality of motors and fans <NUM>) that would yield the lowest noise contribution, while still permitting safe vehicle performance. The NPWS <NUM>, based on the computations, is configured to generate motor control commands <NUM> that are provided to the motor/battery control system <NUM> which, in turn, controls the fan RPM and pitch for each of the plurality of motors and fans <NUM>.

The NPWS <NUM> consumes inputs including battery information comprising battery charge, battery temperature and battery discharge rates over a calculated flight envelope and one or more of (but are not limited to):
weather conditions (e.g., from direct measurement from vehicle sources or from cloud-based sources via secure data link) such as temperature, humidity, and winds; vehicle parameters such as location (e.g., from GPS or other sources), speed (e.g., horizonal and vertical from GPS or on-board pitot systems), attitude (e.g., from attitude and heading reference system), weight (e.g., calculated from onboard systems), and altitude (e.g., barometric, radar altitude, GPS in AGL); noise data such as existing (e.g., standard) area baseline noise map (e.g., existing for Dallas), open source map outlining other sources of noise mapping, and 3D layout and applications of predictive analysis of noise patterns; vehicle flight envelope data (e.g., from flight certification parameters and embedding in the vehicle control laws); estimated current vehicle noise emission (e.g., from flight testing and certification); flight guidance information (e.g., from the on-board flight/navigation system) such as time/distance to destination and approach parameters to destination; and traffic/vertiport status data.

The NPWS <NUM> includes a controller that can reside in the vehicle management computer102, flight control computer <NUM>, a dedicated computing device on the VTOL, or some other onboard computing device on the VTOL. The controller uses a series of available information, at the vehicle level, to calculate the adjustment of individual motors (in a VTOL aircraft) to allow the power (and resulting RPMs) of the motors to be dynamically adjusted (either individually or as a set) in a manner that allows for both safe operations and significantly reduce noise levels.

The controller includes at least one processor and a computer-readable storage device or media encoded with programming instructions for configuring the controller. The processor may be any custom-made or commercially available processor, a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), an auxiliary processor among several processors associated with the controller, a semiconductor-based microprocessor (in the form of a microchip or chip set), any combination thereof, or generally any device for executing instructions.

The computer readable storage device or media may include volatile and nonvolatile storage in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM), for example. KAM is a persistent or non-volatile memory that may be used to store various operating variables while the processor is powered down. The computer-readable storage device or media may be implemented using any of a number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrically PROM), EEPROMs (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory devices capable of storing data, some of which represent executable programming instructions, used by the controller.

The NPWS <NUM> is configured to: identify a VTOL noise level at which the VTOL vehicle can operate at a specific geographical location to not cause a total noise level at the geographical location to exceed a predetermined threshold noise level; dynamically determine, for the plurality of vehicle lifter motors, a motor-specific fan RPM and a motor-specific fan pitch that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location based on VTOL vehicle noise characteristics for the VTOL vehicle and an ambient noise level at the geographical location; determine whether the determined motor-specific fan RPM and motor-specific fan pitch for the plurality of vehicle lifter motors will allow the VTOL vehicle to operate within its safety envelope; and cause a motor-specific fan RPM command and a motor-specific fan pitch command to be sent to a lifter motor controller to cause the vehicle lifter motors to operate at the determined motor-specific fan RPM and motor-specific fan pitch for the lifter motor at the specific geographical location when it is determined that the determined motor-specific fan RPM and motor-specific fan pitch for the plurality of vehicle lifter motors will allow the VTOL vehicle to operate within its safety envelope.

The NPWS <NUM> is further configured to: retrieve vehicle lifter motor parameters comprising a battery status for the plurality of vehicle lifter motors on the VTOL vehicle and a fan status for the plurality of vehicle lifter motors on the VTOL vehicle; and dynamically determine, for the plurality of vehicle lifter motors, the motor-specific fan RPM and the motor-specific fan pitch that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location based on the retrieved vehicle lifter motor parameters. The NPWS <NUM> may be further configured to: retrieve VTOL operating parameters at the specific geographical location comprising one or more of location, altitude, and speed; and dynamically determine, for the plurality of vehicle lifter motors, the motor-specific fan RPM and the motor-specific fan pitch that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location based on the retrieved operating parameters. The NPWS <NUM> may be further configured to: retrieve environmental parameters for the specific geographical location, wherein the retrieved environmental parameters comprise one or more of weather, wind, traffic status, and vertiport status; and dynamically determine, for the plurality of vehicle lifter motors, the motor-specific fan RPM and the motor-specific fan pitch that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location based on the retrieved environmental parameters. The NPWS <NUM> may be further configured to: dynamically determine, for the plurality of vehicle lifter motors, the motor-specific fan RPM and the motor-specific fan pitch that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location during a takeoff or landing at the geographical location. The VTOL noise level to not cause the total noise level to exceed the predetermined noise threshold level may be determined based on the difference between the predetermined noise threshold level and a measured ambient noise level at the geographical location. The predetermined noise threshold level may be a maximum noise level specific to the specific geographical location.

The NPWS <NUM> may be implemented using Artificial Intelligence/Machine Learning (AI/ML) techniques that includes an algorithm to "learn" how and when to apply its noise reduction parameters based on multiple dynamic environmental changes. These changes will automatically and dynamically adapt to changing geographical noise levels and restrictions of various areas without lengthy and expensive updates associated with traditional database implementation.

<FIG> is a process flow chart depicting an example process <NUM> performed in an example NPWS. The example process <NUM> starts by determining that a minimum set of data/information from both the vehicle (decision <NUM>) and external sources (decision <NUM>) needed for noise adjustments are available. If the minimum set is not available (no at decision <NUM> or decision <NUM>), then the NPWS will not generate motor commands.

If the minimum set of data/information is available (yes at decision <NUM> and decision <NUM>), the NPWS will determine if the vehicle had entered a geographical area associated with lower VTOL noise restrictions (decision <NUM>). If the vehicle had not entered a geographical area associated with lower VTOL noise restrictions (no at decision <NUM>), then the NPWS will not generate motor commands (operation <NUM>). If the vehicle had entered a geographical area associated with lower VTOL noise restrictions (yes at decision <NUM>), the NPWS will calculate the correct power adjustments (e.g., motor RPM and pitch control parameters) required to reduce the vehicle noise emissions (operation <NUM>). The NPWS will determine if the calculated power adjustments would cause the vehicle to operate outside a safe flight envelope (decision <NUM>). If the calculated power adjustments would cause the vehicle to operate outside a safe flight envelope (yes at decision <NUM>), then the NPWS will recognize this potential and cancel the application of any noise reduction parameters (operation <NUM>). If the calculated power adjustments would not cause the vehicle to operate outside a safe flight envelope (no at decision <NUM>), then the NPWS will cause the noise reduction motor RPM and pitch control parameters to be sent to the motors <NUM> (operation <NUM>).

<FIG> is a process flow chart depicting an example process <NUM> in a vertical takeoff and landing (VTOL) vehicle for reducing the level of noise output. The VTOL comprises a plurality of vehicle lifter motors and a lifter motor controller. The order of operation within the process <NUM> is not limited to the sequential execution as illustrated in the figure, but may be performed in one or more varying orders as applicable and in accordance with the present disclosure.

The example process <NUM> includes identifying a VTOL noise level at which the VTOL vehicle can operate at a specific geographical location to not cause a total noise level at the geographical location to exceed a predetermined threshold noise level (operation <NUM>). The VTOL noise level to not cause the total noise level to exceed the predetermined noise threshold level may be determined based on the difference between the predetermined noise threshold level and a measured ambient noise level at the geographical location. The predetermined noise threshold level may be a maximum noise level specific to the specific geographical location.

The example process <NUM> includes dynamically determining, for the plurality of vehicle lifter motors, a motor-specific fan RPM and a motor-specific fan pitch that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location based on VTOL vehicle noise characteristics for the VTOL vehicle and an ambient noise level at the geographical location (operation <NUM>). The example process <NUM> further comprises retrieving vehicle lifter motor parameters comprising a battery status for the plurality of vehicle lifter motors on the VTOL vehicle and a fan status for the plurality of vehicle lifter motors on the VTOL vehicle; and dynamically determining, for the plurality of vehicle lifter motors, the motor-specific fan RPM and the motor-specific fan pitch that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location based on the retrieved vehicle lifter motor parameters. The example process <NUM> may further comprise retrieving VTOL operating parameters at the specific geographical location comprising one or more of location, altitude, and speed; and dynamically determining, for the plurality of vehicle lifter motors, the motor-specific fan RPM and the motor-specific fan pitch that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location based on the retrieved operating parameters. The example process <NUM> may further comprise retrieving environmental parameters for the specific geographical location, the retrieved environmental parameters comprising one or more of weather, wind, traffic status, and vertiport status; and dynamically determining, for the plurality of vehicle lifter motors, the motor-specific fan RPM and the motor-specific fan pitch that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location based on the retrieved environmental parameters. The example process <NUM> may further comprise dynamically determining, for the plurality of vehicle lifter motors, the motor-specific fan RPM and the motor-specific fan pitch that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location during a takeoff or landing at the geographical location.

The example process <NUM> includes determining whether the determined motor-specific fan RPM and motor-specific fan pitch for the plurality of vehicle lifter motors will allow the VTOL vehicle to operate within its safety envelope (operation <NUM>) and sending a motor-specific fan RPM command and a motor-specific fan pitch command to the lifter motor controller to cause the vehicle lifter motors to operate at the determined motor-specific fan RPM and motor-specific fan pitch for the lifter motor at the specific geographical location when it is determined that the determined motor-specific fan RPM and motor-specific fan pitch for the plurality of vehicle lifter motors will allow the VTOL vehicle to operate within its safety envelope (operation <NUM>).

Described herein are apparatus, systems, techniques and articles for providing a noise reduction system in an aerial vehicle. The apparatus, systems, techniques and articles provided herein are provided in the context of an example implementation in a VTOL vehicle. The apparatus, systems, techniques and articles provided herein may also be realized in other aerial vehicles such as drones, UAVs (unmanned aerial vehicles), helicopters and others.

Claim 1:
A noise reduction system (<NUM>) in a vertical takeoff and landing (VTOL) vehicle comprising a plurality of vehicle lifter motors (<NUM>) and a lifter motor controller (<NUM>) for the vehicle lifter motors, the noise reduction system comprising a controller (<NUM>, <NUM>) configured to:
identify a VTOL noise level at which the VTOL vehicle can operate at a specific geographical location to not cause a total noise level at the geographical location to exceed a predetermined threshold noise level;
retrieve vehicle lifter motor parameters comprising a battery status for the plurality of vehicle lifter motors on the VTOL vehicle , the battery status comprising battery charge, battery temperature and battery discharge rates over a calculated flight envelope for each of the plurality of vehicle lifter motors, and a fan status for the plurality of vehicle lifter motors on the VTOL vehicle; and
dynamically determine, for the plurality of vehicle lifter motors, a motor-specific fan RPM and a motor-specific fan pitch (<NUM>) that will allow the VTOL vehicle to achieve sufficient lift and not exceed the identified VTOL noise level at the specific geographical location based on VTOL vehicle noise characteristics for the VTOL vehicle and an ambient noise level measured at the geographical location and the retrieved vehicle lifter motor parameters;
determine whether the determined motor-specific fan RPM and motor-specific fan pitch (<NUM>) for the plurality of vehicle lifter motors will allow the VTOL vehicle to operate within its safety envelope; and
cause a motor-specific fan RPM command and a motor-specific fan pitch command (<NUM>) to be sent to the lifter motor controller (<NUM>) to cause the vehicle lifter motors to operate at the determined motor-specific fan RPM and motor-specific fan pitch for the lifter motor at the specific geographical location when it is determined that the determined motor-specific fan RPM and motor-specific fan pitch for the plurality of vehicle lifter motors will allow the VTOL vehicle to operate within its safety envelope.