阅读说明：本技术 用于为混合动力和电动飞行器降低噪声的系统和方法 (System and method for reducing noise for hybrid and electric aircraft ) 是由 L·加滕贝格 R·P·安德森 B·马托斯 于 2018-05-09 设计创作，主要内容包括：一种用于混合动力和电动飞行器的降噪系统和方法,该飞行器具有可控制螺距的螺旋桨或者旋翼(或多个),该螺旋桨或者旋翼具有多个叶片。螺旋桨或者旋翼(或多个)由驱动系统驱动,以向飞行器提供推力,螺旋桨或者旋翼(或多个)的叶片进一步可以绕枢转轴线移动以改变其螺距。飞行器机载的控制器可操作以使螺旋桨或旋翼(或多个)的叶片绕其枢转轴线旋转或者移动,以改变和/或聚焦螺旋桨产生的噪声的至少一个方面,以减少或降低这种噪声,同时保持飞行器的基本恒定的推力、高度和/或飞行速度。(A noise reduction system and method for hybrid and electric aircraft having a controllable pitch propeller or rotor(s) with a plurality of blades. The propeller or rotor(s) is driven by a drive system to provide thrust to the aircraft, and the blades of the propeller or rotor(s) are further movable about the pivot axis to vary the pitch thereof. A controller onboard the aircraft is operable to rotate or move the blades of the propeller or rotor(s) about their pivot axis to alter and/or focus at least one aspect of the noise generated by the propeller to reduce or reduce such noise while maintaining a substantially constant thrust, altitude and/or flight speed of the aircraft.)

1. An aircraft, the aircraft comprising:

a controllable pitch propeller or rotor comprising a plurality of blades movable about at least one axis to change the pitch of the blades thereof;

a drive system having a drive shaft and operable to drive a plurality of propeller blades to rotate relative to the drive shaft to provide thrust for propelling the aircraft; and

a controller in communication with the drive system, the controller operable to rotate the plurality of blades to selectively vary the blade pitch of the plurality of blades to thereby vary and/or focus at least one aspect of noise generated by a propeller of the aircraft while maintaining a substantially constant thrust, a substantially constant altitude, and/or a substantially constant flight speed of the aircraft.

2. The aircraft of claim 1, wherein the drive system comprises an electric motor.

3. The aircraft of claim 1, wherein the drive system comprises an electric motor and an internal combustion engine.

4. The aerial vehicle of claim 3 wherein the electric motor and the internal combustion engine are arranged in a series configuration, wherein the internal combustion engine generates electrical power for the electric motor, and wherein the electric motor is coupled to and drives the propeller or the rotor.

5. The aircraft of claim 1 wherein the blades are rotatable between a plurality of positions including a high blade pitch position and a low blade pitch position.

6. The aircraft of claim 1, further comprising one or more displays, wherein the controller is operable to generate at least one noise map and display the at least one noise map on the one or more displays of the aircraft.

7. The aircraft of claim 6, wherein the at least one noise map comprises a geographical map having noise sensitive areas or noise sensitive zones displayed thereon, and wherein the noise of the aircraft is reduced by changing the blade pitch at constant thrust of the aircraft throughout flight of the aircraft as the aircraft passes over or near the noise sensitive areas or noise sensitive zones.

8. The aircraft of claim 7, wherein the noise sensitive area or the noise sensitive zone is defined using a noise sensitivity index.

9. A hybrid aircraft, comprising:

a controllable pitch propeller assembly including a base and a plurality of propeller blades arranged about the base, wherein the plurality of propeller blades are rotatable about an axis of rotation extending through the base to provide thrust for propelling the hybrid aircraft, the plurality of propeller blades being pivotable about a transverse axis transverse to the axis of rotation of the aircraft to vary a propeller blade angle of the plurality of propeller blades associated therewith;

a drive system including a propeller shaft coupled to the propeller, an internal combustion engine and an electric motor selectively engaged with and disengaged from the propeller shaft to drive rotation of the propeller shaft; and

a controller in communication with the drive system, the controller operable to vary the propeller blade angle of the propeller blades to vary the noise amplitude of the hybrid aircraft while maintaining a substantially constant thrust, a substantially constant altitude, and/or a substantially constant airspeed of the hybrid aircraft in flight.

10. The hybrid aircraft of claim 9, further comprising a power source in communication with the electric motor and operable to provide electrical power to the electric motor, wherein the internal combustion engine is operably coupled to the power source and configured to charge the power source during flight.

11. The hybrid aircraft of claim 9, further comprising one or more displays, wherein the controller is operable to generate at least one noise map and display the at least one noise map on the one or more displays of the aircraft.

12. The hybrid aircraft of claim 11, wherein the at least one noise map comprises a geographical map having noise sensitive areas or noise sensitive zones displayed thereon, and wherein the noise of the aircraft is reduced by changing the propeller blade angle as the aircraft passes over or near the noise sensitive areas or noise sensitive zones while providing constant thrust for the aircraft throughout the flight of the aircraft.

13. The hybrid aircraft of claim 12, wherein the ground noise experienced by the noise sensitive region or the noise sensitive zone is calculated based on a determined distance and azimuth angle between the propeller assembly of the hybrid aircraft and a reference point on the ground.

14. A method for reducing noise generated by an aircraft having a propeller or rotor and a drive system for driving rotation of the propeller, the method comprising:

generating a noise map comprising a series of noise sensitive areas or a series of noise sensitive zones;

displaying the noise map on one or more displays of the aircraft; and

while flying in or near one of the series of noise sensitive areas or the series of noise sensitive zones, changing an angle or pitch of the propeller or the rotor of the aircraft to change and/or focus a noise amplitude of the aircraft while maintaining a substantially constant thrust, a substantially constant altitude, and/or a substantially constant flying speed during flight.

15. The method of claim 14, further comprising moving the propeller or the rotor of the aircraft between a plurality of positions including a high blade pitch position and a low blade pitch position.

16. The method of claim 14, wherein the series of noise sensitive areas or each of the series of noise sensitive zones is defined using a noise sensitivity index.

17. The method of claim 16, wherein generating the noise map comprises applying each of the series of noise-sensitive areas or the series of noise-sensitive zones to a geographic map.

18. The method of claim 14, wherein the experienced ground noise for the noise map is determined using a distance and an azimuth angle between the propeller of the aircraft and a reference point on the ground.

Technical Field

The present disclosure relates to hybrid and electric aircraft, and in particular, to systems and methods for reducing noise from operation of such aircraft.

Background

Hybrid and electric aircraft propulsion technologies can reduce carbon emissions, fossil fuel usage, operating costs, and noise amplitude (footprint) effects of modern aircraft. However, aircraft noise is not a trivial problem, and is expected to be a major design issue for hybrid and electric aircraft. For example, when the demands for propulsion and/or power are balanced, such as to maintain constant thrust for flight, the noise generated by the propellers of the aircraft is a function of rotational speed, blade pitch, flight speed, and other factors. Accordingly, the present disclosure addresses the above-referenced problems in the art as well as other related and unrelated problems.

Disclosure of Invention

Briefly described, in one aspect, the present disclosure is directed to systems and methods for reducing noise generated by hybrid and electric aircraft.

In one example aspect, an aircraft (e.g., a hybrid aircraft) will include an aircraft drive or propulsion system that includes an electric motor, and may further include an internal combustion engine. Alternatively, the aircraft may comprise an aircraft driven or powered by an electric motor, wherein the drive system comprises an electric motor, without necessarily requiring or having an internal combustion engine or other internal combustion engine powered by gas, and without departing from the scope of the present disclosure.

The aircraft will further include one or more rotatable airfoils or blades that are movable or otherwise reconfigurable to change or control the pitch or angle thereof. In one embodiment, the aircraft may include and be driven by a controllable pitch propeller, which will typically have a plurality of airfoils or blades that are rotatable, pivotable, or otherwise movable between a plurality of positions to vary the noise footprint on the ground of the hybrid and/or electric aircraft relative to the drive shaft of the drive system as desired, while also maintaining substantially constant thrust and altitude in flight during operation of the electric motor. Additionally or alternatively, the aircraft may include and be driven by one or more rotors or proprotors having a controllable pitch or otherwise movable/reconfigurable to change its angle or orientation to allow control of the noise emitted thereby without departing from the scope of the present disclosure.

The aircraft further may include a controller or other suitable mechanism operable to adjust the blades of the propellers between different positions during flight to change the pitch or angle of the propeller blades or the pitch or angle of the rotor/proprotor blades. The controller may automatically adjust the blades and/or the controller may facilitate manual adjustment of the blades by a pilot or other operator of the aircraft. This variation of the blades may be controlled independently of the operation of the engine to change or focus the direction of the peak noise of the noise generated by the rotation of the blades, while also maintaining a substantially constant thrust and a substantially constant airspeed.

In one aspect, the controller may include programming operable to determine and/or map the distance and azimuth angle between the propeller and the observer using a series of noise map inputs including characteristics of the propeller or rotor, power, and other factors based on the flight path of the aircraft, configuration information, such as determined attitude, azimuth angle, and/or position of the aircraft, to create or generate a noise pattern or noise map. The noise sensitive areas of the map may further be marked by an indicator of relative sensitivity/noise level versus power setting or speed of the aircraft.

The controller may automatically change the pitch or angle of the blades based at least in part on the generated noise pattern/map, the determined noise sensitive area, and/or other suitable information. Additionally or alternatively, the controller may be configured to display the noise map on one or more displays of the aircraft, such as on a monitor, head-up display, instrumentation, or other instrumentation on an aircraft control panel, or by display on any other suitable display in the cockpit or cabin of the aircraft. The displayed noise map may be used by the pilot, for example, in abnormal situations, as a guide to changing the pitch of the blades to reduce or skew aircraft noise over highly sensitive areas without changing the flight path or flight speed of the aircraft.

Further, a method for reducing the noise footprint of a hybrid and/or electric aircraft may include using a propulsion system having an electric motor and a controllable pitch propeller. The method may include varying the propeller blade angle independently of engine operation to vary the peak noise direction while maintaining substantially constant thrust and flight speed of the aircraft.

The method may include determining and/or mapping the distance and azimuth angle between the propeller and the observer based on the altitude, attitude and/or position of the aircraft and applying these results with additional factors or parameters to generate a noise map for the aircraft with a noise sensitive region marked by a relative sensitivity index for that particular region.

The noise map may be used by an aircraft pilot to control changes in the pitch of the aircraft propeller so that noise can be reduced over highly sensitive areas, rather than significantly changing the flight path or flight speed of the aircraft.

With systems and methods according to the principles of the present disclosure, pilots may be allowed to fly over densely populated or noise sensitive areas, such as national parks, cities, etc., and the noise amplitude of the aircraft may be reduced as they approach these areas, without changing their flight plan or route at the expense of propulsion efficiency. In addition, a noise sensitive map may be developed and displayed to provide visual guidance or indication of the area where the pilot needs to adjust flight settings to best meet noise limits, which further may be presented to the pilot on the display of the aircraft.

Various objects, features and advantages of the present invention will become apparent to those skilled in the art upon a review of the following detailed description when taken in conjunction with the accompanying drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the detailed description serve to explain the principles of the embodiments discussed herein. No attempt is made to show structural details of the present disclosure in more detail than is necessary for a fundamental understanding of the exemplary embodiments discussed herein and the various ways in which they may be practiced. In accordance with common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings may be expanded or reduced to more clearly illustrate the embodiments of the disclosure.

Fig. 1 schematically illustrates an exemplary aircraft according to principles of the present disclosure.

Fig. 2 shows the controllable pitch propeller of the aircraft of fig. 1 in a high blade pitch position and a low blade pitch position.

FIG. 3 illustrates an exemplary graph showing aircraft noise at constant thrust according to one aspect of the present disclosure.

FIG. 4 illustrates another exemplary plot showing directional behavior of aircraft noise as a function of blade pitch angle at constant thrust, according to one aspect of the present disclosure.

Fig. 5 shows a representation of an azimuth angle associated with the aircraft of fig. 1 during flight.

FIG. 6 illustrates an exemplary propeller noise map in accordance with an aspect of the present disclosure.

FIG. 7 illustrates the exemplary noise plot of FIG. 6 with a constant thrust curve.

FIG. 8 illustrates the exemplary noise plot of FIG. 6 with a constant thrust curve and high and low propeller speed settings.

FIG. 9 illustrates an exemplary representation of noisy observation distances and orientations of an aircraft according to one aspect of the present disclosure.

FIG. 10A illustrates a representative geographic map in accordance with an aspect of the present disclosure.

FIG. 10B shows the noise sensitive area and application index applied to the geographic map of FIG. 10A.

Fig. 11 illustrates a net efficiency propulsion diagram for an electric motor with an electric propeller having a controllable pitch according to one aspect of the present disclosure.

FIG. 12 illustrates an exemplary aircraft and on-ground marker for use in the systems and methods of the present disclosure.

Detailed Description

FIG. 1 illustrates an aircraft 100 constructed and/or operable to reduce noise in accordance with the principles of the present invention. It should be understood that the following description is provided as an enabling teaching of embodiments of the present disclosure. One skilled in the relevant art will recognize that many changes can be made to the embodiments described, while still obtaining beneficial or desired results. It is also apparent that: some of the desired benefits of the described embodiments may be obtained by selecting some of the features of the embodiments without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the described embodiments are possible and can even be desirable in certain circumstances. Accordingly, the following description is provided as illustrative of the principles of embodiments of a system and method for providing noise reduction for an aircraft and not in limitation thereof.

As shown in fig. 1, an aircraft 100 includes a forward mounted propeller 102 driven by a drive system or propulsion system 104. The drive system 104 may include a hybrid propulsion system having one or more electric motors 106, and may also include an internal combustion engine 108, each of which may be communicatively coupled or linked with the propeller 102, such as by a propeller drive shaft 110 operatively connected to the aircraft propeller 102, to enable power to be transmitted between the electric motor 106 and/or the internal combustion engine 108 and the propeller 102. The electric motor 106 and/or the internal combustion engine 108 may be connected to the propeller drive shaft 110 or the propeller 102 by one or more gear assemblies or pulley assemblies and/or using other suitable drive coupling mechanisms or connection devices without departing from the scope of the present invention.

Additionally or alternatively, the aircraft 100 may include and be driven by one or more rotors or proprotors having a plurality of blades or airfoils with controllable pitch or otherwise movable/reconfigurable to change its angle or direction without departing from the scope of the present disclosure.

In one example, the hybrid propulsion system 104 further may include one or more mechanisms, such as a clutch or other suitable mechanism or device, that allows for selectively engaging and disengaging the electric motor 106 or the internal combustion engine 108 with the propeller 102, such as: such that the aircraft 100 may operate in a hybrid mode in which the propeller 102 is driven by the electric motor 106 and the internal combustion engine 108; so that the aircraft 100 can operate in an electric mode in which the propeller 102 is driven solely by the electric motor, while the internal combustion engine is separate from the propeller; and/or to enable the aircraft 100 to have a combustion engine only mode in which the propeller 102 is driven only by the combustion engine 108 and the electric motor 106 is decoupled from the propeller. Exemplary assemblies for hybrid aircraft are shown and described in U.S. patent nos. 9,102,326 and 9,254,992, which are incorporated herein by reference as if set forth in their entirety.

In another example, the electric motor 106 and the internal combustion engine 108 may be arranged in a series configuration, wherein the internal combustion engine 108 is operatively coupled to the electric motor 106 or a power source 113 (i.e., one or more batteries) of the electric motor, and wherein the internal combustion engine 108 serves primarily only to generate electricity to power the electric motor 106 and/or to charge the power source 113 that powers the electric motor 106.

In yet another example, the aerial vehicle 100 may comprise an electrically powered aerial vehicle that may omit the internal combustion engine 108, and wherein the propeller 102 of the aerial vehicle is powered by one or more electric motors 106. Such electric motor(s) may be connected to the propeller 102 by one or more gear assemblies or pulley assemblies or other suitable devices/mechanisms.

For embodiments of the present disclosure, an exemplary gear or pulley ratio between the propeller and the electric motor may be 1:1, but any suitable ratio is possible without departing from the present disclosure, such as 1.5:1, 2:1, 3:1, 1:3, 1:2, 1:1.5, and so forth. The electric motor may also be directly connected to the propeller 102, for example, with the propeller attached to the drive shaft of the electric motor, in such a manner without departing from the scope of the present disclosure.

The electric motor 106 typically uses electricity as its primary power source. For example, the electric motor 106 may be in communication with one or more power sources 113 (e.g., one or more batteries) and/or other suitable power generation devices. The internal combustion engine 108 may further be connected to a generator in order to be able to charge the power source 113 during flight. The use of electric motors expands performance and can provide benefits not provided by gas engines because electric motors are naturally quieter, efficient, do not produce carbon emissions, and can have fewer moving parts, thereby reducing operating costs and maintenance. By way of illustration and example, the electric motor 106 may comprise YASA 750, provided by YASA ltd of kingdom bedrington, of kingdom, and it will be appreciated that other suitable electric motors capable of delivering hundreds of horsepower with high specific torque power, such as electric motors suitable for light aircraft operation, may also be used without departing from the disclosure. Other examples of electric motors may include AF-130, AF-140, AF-230, or AF-240 electric motors available from GKN of Worcestershire, UK; HVH410-075 or HVH410-150 electric motor from Remy International, Inc. of Pendleton, India; and/or Powerphase HD 220 or Powerphase HD 250 electric motors from UQM technologies of Longmont, Columbia.

The propeller 102 generally includes a plurality of blades 114 disposed about a base 115. Each of the blades 114 may rotate about a rotational axis RA (fig. 1-2, 5) that extends through the base 115 and along the drive/propeller shaft 110 of the aircraft to provide thrust to the aircraft 100. For example, fig. 1, 2 show a propeller 102 including two blades 114. However, the propeller 102 may also be configured in other forms, for example, having three or four blades, without departing from the scope of the present disclosure. In one embodiment, the propeller 102 may have a span, diameter, or overall length of about 6 feet between the ends of the propeller blades, although other spans, diameters, or lengths are possible without departing from the scope of the present disclosure, such as a diameter in the range from about 5 feet to about 25 feet.

As generally shown in fig. 1 and 2, the Propeller 102 will comprise a controllable pitch Propeller, which may comprise a multi-bladed Propeller available from MT-Propeller engineering of Atting, germany, which will be operable to enable the blades 114 of the Propeller to be pivoted, rotated or otherwise moved about the pitch axis PA and relative to the axis of rotation RA to change or vary the blade pitch or angle of the blades 114. For example, as shown in fig. 1 and 2, the pitch axis PA may be transverse or oblique to the rotational axis RA, as shown.

In addition, the aircraft 100 includes a controller 112 that is typically located within the cockpit or other suitable location of the aircraft and is in communication with the controllable pitch propeller 102 and is operable to control adjustment or variation of the controllable pitch propeller to enable a pilot or co-pilot to change the pitch of the propeller blades by moving the propeller blades between a plurality of positions, such as a high blade pitch position 116 and a low blade pitch position 118 (fig. 2). In some embodiments, the drive(s) or actuator(s) controlling the change in pitch of the blades of the propeller 102 may be powered by operation of the aircraft's electric motor 106, or by using other suitable means, such as an additional electric motor(s) or other suitable actuator(s), such as a hydraulic actuator. Thus, during operation of the aircraft in the gas engine mode, the controller 112 or pilot may also vary the angle or pitch of the propeller blades 114 in flight to vary the torque and aircraft speed to help improve performance over a range of flight speeds and to help reduce noise generated by the propellers. However, the propeller 102 may similarly operate in a hybrid mode or an electric mode without torque and motor speed limitations.

The combination of the electric propulsion motor 106 and the controllable pitch propeller 102 may further provide additional degrees of freedom over conventional aircraft internal combustion engines. For example, unlike conventional engines where the engine speed and torque curves are typically fixed, the above combination may vary torque independently of motor speed, and may allow for maintaining substantially constant thrust of the aircraft while flying at multiple engine speeds by varying the blade pitch angle and thus varying the torque. In reducing noise using this approach, a substantially constant thrust may further be maintained without substantially changing aircraft acceleration or performance.

When the internal combustion engine 108 is running, both the propeller and the internal combustion engine will generate noise. For example, at lower engine operating speeds, the engine will dominate the noise output, while at higher operating speeds, the propeller will begin to dominate the perceived noise level. In hybrid and/or electric modes, or where electric aircraft use electric motors rather than internal combustion engines, only propeller noise considerations are typically a problem, since electric motors are virtually silent compared to the noise generated by propellers for most operating speeds. To address this propeller noise, the pitch or position of the blades 114 of the propeller 102 may be changed to change or reduce the noise footprint in flight and on the ground as discussed below.

FIG. 3 illustrates an exemplary curve 119 that illustrates the noise signature of an aircraft at constant thrust. The noise from the propeller 102 detected/experienced at some location spaced from the propeller 102 may be expressed as a function of its speed, blade pitch (producing a particular torque), true flight speed, and distance and position relative to the rotational axis of the propeller. The total amplitude of the noise generated by the propeller 102 at constant thrust can be summarized as generating high noise at high rotational speeds due to the tip speed of sound. High noise may also be generated by reducing the rotational speed at a constant thrust while generating a blade pitch angle that results in separation (i.e., a stall condition). The noise minimum is between these two extremes, generally as shown in FIG. 3.

Thus, the noise may be expressed as a function of the rotational speed and the blade angle. However, the noise does not typically radiate uniformly outward as a point source. Fig. 4 further illustrates that the noise from the propeller is directional, and thus, there are directions that experience a greater magnitude of noise than other directions. The direction of maximum noise may be expressed as a function of true airspeed (true airspeed), rotational speed, and blade angle.

As generally shown in fig. 5, an azimuth angle δ may also be defined, which continues from the rotational axis RA of the propeller or from the nose, zero degrees, to about 90 degrees, the position of the propeller disk. However, the azimuthal angle may range from about 0 degrees to about 180 degrees, and may be further defined as being opposite the direction of the nose, e.g., behind the aircraft, or with any other suitable arrangement/configuration, without departing from the scope of the present disclosure.

With the combination of the propeller 102 and the electric propulsion motor 106 having controllable pitch according to the present disclosure, substantially constant thrust may be maintained by controlling the blade pitch to move the point of maximum noise to form a graphical representation of the noise amplitude produced by the propeller at different pitches.

As generally shown in fig. 6-8, it is further possible to generate a noise map 120 and an arbitrary constant thrust curve 122 as a function of propeller torque and rotational speed. Such a graph may also show high noise and low noise propeller speed settings (fig. 8). For example, using a defined input (e.g., as shown in table 1 below), a noise map may be generated, which may also be displayed in a similar general format as the electric motor efficiency. In one example, the Hamilton standard may be used for empirical noise calculations. Table 1 provides exemplary inputs to generate an exemplary noise map.

TABLE 1

Input device	Value of	Unit of
			Diameter of propeller	6	Foot
Number of blades	2	-
			Number of propellers	1	-
Power input to each propeller	*****	Hp
			Flying speed	100	KTAS
Ambient temperature	59	℉
			Azimuth angle	105	Degree of rotation
Defining the distance of the noise	1000	Foot

The value of the power input to each propeller may be arbitrary and/or may vary due to the nature of the torque versus rotational speed map.

A noise map 120 may be generated for all power settings within a defined envelope, where a defined noise level may be calculated, and each power setting may correspond to a single thrust value, allowing any thrust value to be selected for the calculation. For example, as shown in fig. 7 and 8, a thrust of 500 lbf may be used.

Through the defined noise map, and through the selected or known cruise thrust, the varying propeller blade angles (or rotor/proprotor blade angles) required to minimize noise at different positions, altitudes, and speeds during flight of the aircraft can be determined. These noise maps 120 may be generated by the controller 112 of the aircraft, and the controller 112 of the aircraft may display the noise maps 120 on one or more displays 121 disposed within the cockpit of the aircraft. However, the present disclosure is not so limited, and the noise map(s) may be generated off-board using a computer or other suitable device (e.g., a flight control center) and may be communicated to the aircraft prior to or during flight.

Thus, based on these generated noise maps 120, the aircraft controller 112 may maintain constant thrust at multiple engine speeds or motor speeds, and may control the pitch of the propellers by varying the angle of the propeller blades 102 (or the angle of the rotor/proprotor blades) and the resulting torque to allow the aircraft controller 112 to maintain a substantially constant airspeed (airspeed) with the ability to vary the propeller noise amplitude. Additionally or alternatively, a pilot or other operator of the aircraft may control/vary the angle/pitch, thrust, and/or torque of the propeller blades 114 based on the generated noise map 120 to minimize noise over a selected area.

In one example, a map of noise related variables such as propeller rotational speed, blade pitch, angle of attack, and true airspeed may also be generated for each aircraft propulsion system in its use. A noise sensitive area map may also be generated on the surface of the earth from latitude, longitude and noise sensitive indicators. These may also be generated by the controller and displayed on a display, or alternatively, generated by an off-board computer (e.g., at a flight control center) before or during flight.

Propeller noise does not radiate uniformly outward as a point source, and noise in some directions may be greater than in others. Using the noise directivity pattern and the noise sensitive area pattern in a north-east-down (NED or NEU) system, the ground noise can be predicted by mapping it with the attitude (Euler angle) and position (e.g., from a position device or positioning device, such as an IMU or GPS in communication with an aircraft controller) of the aircraft 100.

Using the expected flight path of the aircraft, noise may be reduced as it passes through the noise sensitive area throughout flight by changing the pitch of the blades at constant thrust (e.g., by the pilot or automatically by the controller). For example, given a noise map, a geographical map, and a state vector of the aircraft, an optimization algorithm may be used. The location of maximum noise for the aircraft may move rapidly or jump over the noise sensitive area, staying loitering in the non-sensitive area.

Accordingly, the exemplary embodiment of the electric motor 106 and the controllable pitch electric propeller 102 may minimize noise in noise sensitive areas while substantially avoiding potentially sacrificing performance of the aircraft or causing substantial discomfort to passengers and crew.

Also generally shown in fig. 9, the perceived noise may be expressed as a function of the distance from the propeller 102 and the azimuth angle δ in the forward direction relative to the propeller axis. It may be desirable to be able to determine distance and orientation based on the position and attitude of the aircraft relative to observers or measurement devices (e.g., noise observations or reference points 124) on the ground. The position may be determined from latitude, longitude and altitude, while the attitude is the pitch angle θ, the grade angle φ and the heading ψ. It may be assumed that the pitch angle phi is rotated about a longitudinal axis of the aircraft or a rotational axis RA, which may be parallel to said longitudinal axis.

The distance between a pair of latitude and longitude, or arc length L, may be calculated, for example, using the Haversene equation shown below:

(3)L＝2R*b

the defined distance, which has not taken into account the difference in height between the aircraft and the observer position, can be calculated as follows, where R is the radius of the earth and A is the central angle of the earth:

the azimuth angle δ may then be calculated to complete the function. Using the aircraft location as the origin, two three-dimensional vectors may be generated and/or graphically represented, one pointing toward the observer and the other pointing toward the direction of travel of the aircraft. The angle between these vectors is the azimuth angle, calculated as follows:

wherein:

for example, the Haversine formula can be used to calculate Latitude and longitude terms inside without any altitude correction, since the goal is to determine the component vectors in the NED. The first term in each vector represents the "north" component, the second term represents the "east" component, and the third term represents the "down" component. To calculate dlat, a constant longitude may be applied to the Haversine formula to determine the distance between two lines of latitude. To calculate dlon, a constant latitude may be applied to the Haversine formula to determine the distance between two longitude lines. Finally, to calculate dh, the two altitudes for the aircraft and the observer can be subtracted. If the aircraft is north or east of the observer, negative correction factors are required to calculate the correct azimuth angle. If the aircraft is north of the observer, dlat ═ -dlat; if the aircraft is east of the observer, dlon ═ isDlon. This correction is only applied when the variable assignments shown in fig. 9 are used, where location a is the aircraft and location B is the observer.

The noise sensitivity index may further be rated on a scale of 1 to 10, where 1 is defined as least sensitive to noise and 10 is most sensitive to noise. This indicator comes into play when a noise sensitive area is defined in a specific geographical area of the earth. For example, a sea is likely to have a noise sensitivity index of 1, while a metropolitan city is likely to have a noise sensitivity index of 10.

A sampled noise map combined with or superimposed on the geographical map may be generated and overlaid on the selected area. For example, fig. 10A and 10B show a map of the region of the Daytona Beach (FL region) in florida with noise sensitive regions generated and added on the surface of the earth, as shown in fig. 10A. As shown on the graph of fig. 10B, a noise sensitive area and an application index may also be provided. Such a combined sampled noise geographical map may be generated by the controller 112 and displayed on a display in the cockpit, although such a map may also be generated off-board (e.g., at a flight control center) without departing from this disclosure.

Using the determined or known sensitivity zones and corresponding indices, the controller 112 may automatically change to minimize or produce minimized noise over a particular area (e.g., an area having index 9), and generally any blade pitch or angle may be used over an area having index 1. Additionally or alternatively, a pilot or other operator of the aircraft may manually change the pitch or angle of the blades based on the area, sensitive zone, and/or corresponding index over which the aircraft 100 is traveling. This allows for reduced noise on major population areas and includes transition zones, so the aircraft may have reduced noise when approaching highly sensitive zones.

Fig. 11 shows a propulsion diagram developed for YASA 750 electric motors with controllable pitch electric propellers (e.g., MT propellers). In fig. 11, the equipotential lines 126 are lines of constant propulsive efficiency in percent. The dotted line 128 represents Hamilton standard constant far field noise (dBA). The dashed line 130 is the line of minimum voltage across the electric motor and represents the envelope. The solid line 132 is the envelope for high fidelity propeller data. The chain line 134 is a line indicating a constant thrust. This is data for the HK-36 "St.Louis" construct, which is present in EFRC. In hybrid-electric applications, any region may be selected/selected on line 134 to facilitate active optimization of far field noise emissions, propulsion efficiency, or a combination of both. This can be done at constant flying speed. This is an algorithm for active ground (far-field) noise reduction.

Additionally, a method for reducing noise amplitude of a hybrid and/or electric aircraft may be provided that may include providing a propulsion system having an electric motor and an electrically controllable pitch propeller. The method may further include varying the propeller blade angle independently of the engine to vary the peak noise direction while maintaining constant thrust and airspeed. The method may further include mapping the distance and azimuth angle between the propeller and the observer by mapping the attitude and/or position of the aircraft, and applying these results to a noise map of a noise sensitive area marked with a relative sensitivity index through that particular area to help reduce noise over a high sensitivity area without changing the flight path and flight speed of the aircraft.

Examples of the invention

The following example demonstrates low noise or high noise at about 500 feet above ground level during ascent from the Daytona Beach international airport using data from Cessna 172S (200 in fig. 12). Although the Cessna 172S does not have an electric motor or controllable pitch propeller, this example assumes that this is the case while maintaining the geometry and performance characteristics of the propeller. It is also assumed that the transmission between the motor and the propeller is 1:1.

Fig. 12 shows the east ground planning region of the Daytona Beach international airport.

TABLE 2

Fig. 12 shows a marker 202 located on the ground as a reference point for an observer (here measuring noise). Latitude, longitude and altitude at average sea level were obtained using Google Earth.

The above procedure is used to determine the distance and azimuth angle between the aircraft and the observer, assuming an earth radius R of 20902232 feet:

(11) L＝2(209022312)*1.67e ^-5

＝771.34ft

(13) d ²＝(20902232+500) ²+(20902232+32) ²-2(20902232+500)(20902232+32(cos(0.0021))

＝8.14e ⁵

the azimuth angle can now be calculated:

a noise map for this flight condition can now be generated.

Table 3 summarizes the results of the figure. The 500 lbf thrust is arbitrarily chosen and does not necessarily represent the actual thrust value generated under given flight conditions.

TABLE 3

Parameter(s)	High noise	Low noise	Unit of
				Rotational speed of propeller	2700	2000	Rpm/min
Propeller torque	220	300	Foot-pound force
				Noise of propeller	86.1	76.4	Decibel
Thrust force	500	500	Pound force

The measurement may be 86.1 db or 76.4 db depending on the propeller settings. Due to the combination of the electric motor assumed and the controllable pitch propeller, both 86.1 db or 76.4 db are achievable at a single point with constant thrust and flight speed. If the noise sensitivity index is high, similar to that shown in FIG. 10B, a lower noise value is desired.

The foregoing description generally illustrates and describes various embodiments of the present invention. Those skilled in the art will understand, however, that various changes and modifications may be made in the above-described structure of the invention without departing from the spirit and scope of the invention disclosed herein, and it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. Further, the scope of the present disclosure should be construed as encompassing various modifications, combinations, additions, permutations and the like of the foregoing and the above-described embodiments, as would be considered within the scope of the present invention. Accordingly, the various features and characteristics of the present invention discussed herein are selectively interchangeable and apply to other illustrated and non-illustrated embodiments of the invention, and many further variations, modifications, and additions may be made thereto without departing from the spirit and scope of the invention as set forth in the appended claims.