Acoustic airspeed sensors and processing technology

Abstract

Acoustic airspeed sensor and processing technology. An acoustic airspeed sensor system may include: at least one acoustic transmitter configured to provide acoustic pulses; and a plurality of acoustic receivers, including at least a first acoustic receiver, a second acoustic receiver, and a third acoustic receiver, each acoustic receiver being located at a first radial distance from the at least one acoustic transmitter. The first acoustic receiver, the second acoustic receiver, and the third acoustic receiver are each configured to receive the acoustic pulses at a first time, a second time, and a third time, respectively, and to output a first receiver signal, a second receiver signal, and a third receiver signal, respectively. The system may include a computing unit operatively connected to the acoustic receivers and configured to generate a propagation function. The computing unit is further configured to determine the true airspeed based on the receiver signals and the propagation function.

Description

Background Technology

[0001] In aviation, airspeed is defined as the speed of an aircraft relative to the surrounding air. Airspeed can be reported as indicated airspeed (IAS) read from an anemometer. Airspeed can be further reported as calibrated airspeed (CAS), equivalent airspeed (EAS), and true airspeed (TAS), each based on an initial IAS. Accurate measurement of airspeed is crucial for aircraft functionality because it affects lift and drag.

[0002] Traditionally, the device used to measure airspeed in aircraft is the pitot probe, a long, thin tube with two orifices. It indirectly determines the stagnation pressure by stopping (stagnating) the moving air when there is no outlet to allow airflow to continue. In practice, the pitot probe is placed in the airflow outside the aircraft, with the front orifice measuring the stagnation pressure and the side orifice measuring the static pressure. The difference between the stagnation pressure and the static pressure can then be calculated to determine the airspeed. A disadvantage of pitot probes is that they can become clogged during flight, especially by ice, making the readings inaccurate. Inaccurate pitot probe readings can severely impair a pilot's ability to effectively fly the aircraft and may lead to a crash.

[0003] In addition to pitot tube probes, modern aircraft typically employ different and / or redundant methods / devices to measure airspeed. For this purpose, ultrasonic anemometers, also known as acoustic or sound wave anemometers, have been developed. These devices, usually built flush with or near flush with the aircraft's outer surface, measure aircraft speed based on the timing of acoustic pulses between one or more pairs of transducers, as the flight time of the acoustic pulses is altered by the direction of the airflow. A rough calculation of airspeed based on ultrasonic anemometer readings can be performed by measuring the differences in sound propagation between the transducer pairs. Currently, calculations used to determine airspeed do not accurately account for the boundary layer (i.e., the air velocity in the immediate vicinity of the aircraft's surface), ultimately reducing the accuracy of airspeed measurements. Therefore, a system or method that avoids the shortcomings of conventional methods is desired. Summary of the Invention

[0004] An acoustic airspeed sensor system may include: at least one acoustic transmitter configured to provide acoustic pulses; and a plurality of acoustic receivers, including at least: a first acoustic receiver located at a first radial distance from the at least one acoustic transmitter; a second acoustic receiver located at a second radial distance from the at least one acoustic transmitter; and a third acoustic receiver located at a third distance from the at least one acoustic transmitter. The first acoustic receiver is configured to receive the acoustic pulses at a first time and output a first receiver signal. The second acoustic receiver is configured to receive the acoustic pulses at a second time and output a second receiver signal. The third acoustic receiver is configured to receive the acoustic pulses at a third time and output a third receiver signal. The sensor system may include a computing unit operatively connected to the first, second, and third acoustic receivers. The computing unit is configured to: receive a first receiver signal, a second receiver signal, and a third receiver signal; determine a first propagation time between receiving the first receiver signal and emitting an acoustic pulse from an acoustic transmitter; determine a second propagation time between receiving the second receiver signal and emitting an acoustic pulse from an acoustic transmitter; receive or determine a wind angle; determine a third propagation time between receiving the third receiver signal and emitting an acoustic pulse from an acoustic transmitter; receive or determine the wind angle; determine the airspeed based on the first propagation time, the second propagation time, and the wind angle; and output an airspeed signal indicating the airspeed.

[0005] In some embodiments of the system, the computing unit includes one or more propagation measurement modules operatively connected to a pulse control module and at least one of a first acoustic receiver, a second acoustic receiver, or a third acoustic receiver. In some embodiments, the pulse control module is operatively connected to at least one acoustic transmitter and configured to cause the at least one acoustic transmitter to transmit an acoustic pulse at a transmission time, wherein the one or more propagation measurement modules are configured to compare the transmission time and a first time to determine a first propagation time and output first propagation data. In some embodiments, the one or more propagation measurement modules are configured to compare the transmission time and a second time to determine a second propagation time and output second propagation data, wherein the one or more propagation measurement modules are configured to compare the transmission time and a third time to determine a third propagation time and output third propagation data.

[0006] In some embodiments of the system, the calculation unit includes a wind angle module, which is operatively connected to one or more propagation measurement modules to receive first propagation data, second propagation data, and third propagation data, and is configured to determine the wind angle based on the first propagation data, the second propagation data, and the third propagation data and output the wind angle data.

[0007] In some embodiments of the system, the computing unit includes an airspeed module operatively connected to a wind angle module to receive wind angle data therefrom, wherein the airspeed module is operatively connected to one or more propagation measurement modules to receive first propagation data, second propagation data, and third propagation data, wherein the airspeed module is configured to determine airspeed based on the wind angle, the first propagation data, the second propagation data, and the third propagation data, and output an airspeed signal.

[0008] In some embodiments of the system, the computing unit includes a sound speed module operably connected to an airspeed module to receive airspeed signals, wherein the sound speed module is operably connected to one or more propagation measurement modules to receive first propagation data, second propagation data, and third propagation data, wherein the sound speed module is operably connected to one or more propagation measurement modules to receive first propagation data, second propagation data, and third propagation data, wherein the sound speed module is operably connected to a wind angle module to receive wind angle data, wherein the sound speed module is configured to determine the sound speed based on the wind speed data, the first propagation data, the second propagation data, and the third propagation data, and output the sound speed data.

[0009] In some embodiments of the system, the sound speed module is configured to determine the Mach number based on the sound speed and output a Mach number signal.

[0010] In some embodiments of the system, the computing unit includes a static air temperature module operatively connected to a sound speed module to receive sound speed data, determine the static air temperature based on the sound speed, and output a static air temperature signal.

[0011] In some embodiments of the system, the computing unit includes a multiplexer between one or more propagation measurement modules and at least one other module of the computing unit, the multiplexer being configured to receive first propagation data, second propagation data and third propagation data from one or more propagation measurement modules and to multiplex the first propagation data, second propagation data and third propagation data.

[0012] In some embodiments of the system, two of the first radial distance, the second radial distance, or the third radial distance are equivalent.

[0013] In some embodiments of the system, at least one of the first acoustic receiver, the second acoustic receiver, or the third acoustic receiver includes a microelectromechanical system (MEMS) microphone.

[0014] In some embodiments of the system, the computing unit is configured to determine whether the acoustic receiver is blocked by setting a maximum time for the response, and to ignore one or more signals from the blocked acoustic receiver.

[0015] In some embodiments of the system, the processor uses a beamforming algorithm.

[0016] In some embodiments of the system, beamforming algorithms include classical algorithms, Capon algorithms, MUSIC algorithms, root-MUSIC algorithms, Bartlett algorithms, ESPIRIT algorithms, Min-Norm algorithms, Burg algorithms, SAMV algorithms, Welch algorithms, time-reversal MUSIC algorithms, MVDR algorithms, Akaike information criterion algorithms, or minimum description length (MDL) criterion algorithms.

[0017] In some embodiments of the system, at least one acoustic transmitter and at least one of a plurality of acoustic receivers are configured to be flush-mounted on the surface of the aircraft.

[0018] A computer-implemented method may include: transmitting an acoustic pulse using at least one acoustic transmitter; receiving the acoustic pulse at a first time using a first acoustic receiver located at a first radial distance from the at least one acoustic transmitter; and providing a first receiver signal from the first acoustic receiver in response to receiving the acoustic pulse. The method may include: receiving the acoustic pulse at a second time using a second acoustic receiver located at a second radial distance from the at least one acoustic transmitter; and providing a second receiver signal from the second acoustic receiver in response to receiving the acoustic pulse. The method may include: receiving the acoustic pulse at a third time using a third acoustic receiver located at a third radial distance from the at least one acoustic transmitter; and providing a third receiver signal from the third acoustic receiver in response to receiving the acoustic pulse. The method may include determining a first propagation time between receiving the first receiver signal and transmitting the acoustic pulse by the at least one acoustic transmitter. The method may include determining a second propagation time between receiving the second receiver signal and transmitting the acoustic pulse by the at least one acoustic transmitter. The method may include determining a third propagation time between receiving the third receiver signal and transmitting the acoustic pulse by the at least one acoustic transmitter. The method may include constructing a propagation function based on at least one of the following: the position of at least one acoustic transmitter relative to at least one of a first receiver, a second receiver, and a third receiver; the amplitude of at least one of the first receiver signal, the second receiver signal, or the third receiver signal; or the phase of at least one of the first receiver signal, the second receiver signal, or the third receiver signal. The method may include receiving or determining a wind angle. The method may further include determining airspeed based on the propagation function and at least one of a first propagation time, a second propagation time, a third propagation time, or a wind angle, and outputting an airspeed signal indicating the airspeed.

[0019] This invention is provided solely as an introduction to the subject matter fully described in the detailed description and accompanying drawings. The summary should not be construed as describing essential features, nor should it be used to define the scope of the claims. Furthermore, it should be understood that both the foregoing summary and the following detailed description are merely illustrative and explanatory, and do not necessarily limit the claimed subject matter. Attached Figure Description

[0020] A detailed description is provided with reference to the accompanying drawings. The use of the same reference numerals in different instances in the specification and drawings may indicate similar or identical entries. Various embodiments or examples (“Examples”) of this disclosure are disclosed in the following detailed description and drawings. The drawings are not necessarily to scale. Generally, unless otherwise specified in the claims, the disclosed processes can be performed in any order. In the figures:

[0021] Figure 1A This is a top view of an air data sensor according to one or more embodiments of the present disclosure, showing an embodiment of the transmitter and receiver layout.

[0022] Figure 1B This is a top view of an air data sensor according to one or more embodiments of the present disclosure, showing an embodiment of the transmitter and receiver layout.

[0023] Figure 2 It is a polar plot depicting the flight time between an acoustic transmitter and an acoustic receiver at various airspeeds (as shown, V=0, 60, 120, 180 and 240) according to one or more embodiments of the present disclosure.

[0024] Figure 3 It is a graph depicting the time-of-flight difference between relative acoustic receivers according to one or more embodiments of the present disclosure.

[0025] Figure 4 This is a system and software block diagram of a first example of an acoustic air data sensor according to one or more embodiments of the present disclosure.

[0026] Figure 5 This is a pulse timing diagram of an acoustic air data sensor according to one or more embodiments of the present disclosure.

[0027] Figure 6 An equivalent subsystem of an acoustic air data sensor according to one or more embodiments of the present disclosure is described.

[0028] Figure 7 This is a top view of an acoustic air data sensor with unrestricted airflow according to one or more embodiments of the present disclosure.

[0029] Figure 8This is a system and software block diagram of a second example of an acoustic air data sensor according to one or more embodiments of the present disclosure.

[0030] Figure 9 This is a flowchart of an acoustic angle-of-attack process according to one or more embodiments of the present disclosure.

[0031] Figure 10 This is a schematic diagram of an embodiment of a sensor or sensor system according to one or more embodiments of the present disclosure.

[0032] Figure 11 This is a view of an acoustic air data sensor with unrestricted airflow, having a boundary layer indication, according to one or more embodiments of the present disclosure.

[0033] Figure 12 It is a polar plot depicting the flight time between an acoustic transmitter and an acoustic receiver at various airspeeds (as shown, V=0, 60, 120, 180 and 240) according to one or more embodiments of the present disclosure, showing the masking effect due to velocity.

[0034] Figure 13 This is a schematic diagram of an embodiment of placing one or more sensors on an aircraft according to one or more embodiments of the present disclosure. Detailed Implementation

[0035] Before explaining one or more embodiments of this disclosure in detail, it is to be understood that the embodiments, in their application, are not limited to the details of the construction and the arrangement of components or steps or methods set forth in the following description or illustrated in the accompanying drawings. In the following detailed description of the embodiments, many specific details may be set forth to provide a more thorough understanding of this disclosure. However, it will be apparent to those skilled in the art who will benefit from this disclosure that the embodiments disclosed herein can be practiced without some of these specific details. In other instances, well-known features may not be described in detail to avoid unnecessarily complicating this disclosure.

[0036] As used herein, the letters following the reference numerals are intended to refer to embodiments of features or elements that may be similar to, but are not necessarily identical to, previously described elements or features having the same reference numerals (e.g., 1, 1a, 1b). Such shorthand notation is for convenience only and should not be construed as limiting this disclosure in any way unless expressly stated otherwise.

[0037] Furthermore, unless explicitly stated otherwise, "or" refers to inclusive "or," not exclusive "or." For example, condition A or B is satisfied by any one of the following: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist).

[0038] Furthermore, the use of “a” or “an” can be used to describe elements and components of the embodiments disclosed herein. This is done merely for convenience, and “a” and “an” are intended to include “one” or “at least one”, and the singular includes the plural unless it is obvious that they have a different meaning.

[0039] Finally, as used herein, any reference to “one embodiment” or “some embodiments” means that a particular element, feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment disclosed herein. The phrase “in some embodiments” appearing in different places in the specification does not necessarily refer to the same embodiment, and embodiments may include one or more of the features explicitly described or inherent in this document, or any combination of sub-combinations of two or more such features, and any other features that may not necessarily be explicitly described or inherent in this disclosure.

[0040] The apparatus, systems, and associated methods relate to acoustic air data sensors. Using the apparatus, systems, and associated methods described herein allows for the sensing of wind angles (e.g., angle of attack, angle of slip, airspeed) without the presence of mechanical moving parts or obstruction of airflow. Furthermore, this allows for high bandwidth and update rates for measurements such as wind angle and airspeed.

[0041] Figure 1A This is a top view of the acoustic air data sensor 10, including an acoustic transmitter 12, acoustic receivers 14A-14L, a radius 16, an airflow 18, and a wind angle 20 (e.g., angle of attack). While some embodiments may involve an angle of attack, those skilled in the art will understand that the wind angle is the sensed angle, which can be the angle of attack (AOA), the slip angle (AOS), or any angle in between, depending on local flow conditions (e.g., due to sensor placement and the aircraft's operating state).

[0042] Regarding the determination of the wind angle (e.g., AOA), in some embodiments, acoustic receivers 14A-14L may be placed at a fixed radius (r) around the acoustic transmitter 12. The acoustic transmitter 12 may be a piezoelectric loudspeaker, a cone loudspeaker, a microelectromechanical system (MEMS) loudspeaker, or other acoustic transducer. The acoustic receiver may be a microphone, including a MEMS microphone, a condenser microphone, a laser, or other acoustic transducer.

[0043] Acoustic receivers 14A-14L can be positioned at 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°, respectively, as shown. Any other suitable numbering or positioning of the receivers is considered herein. The flight time of the acoustic pulse emitted by acoustic transmitter 12 can be measured for each of the acoustic receivers 14A-14L. ) or phase modulation. For example, from the acoustic transmitter (T) 12 to the acoustic receiver (R) placed at an angle θ. θ The flight time of each acoustic pulse in 14A-14L is given by the following formula:

[0044] (Equation 1)

[0045] Where C0 is the speed of sound, α is the angle of attack of 20°, and V is the airspeed of the airflow 18. A similar arrangement of acoustic receiver 14 and transmitter 12 is disclosed in U.S. Patent No. 10,739,371 entitled "Acoustic Airspeed Sensors," which is incorporated herein by reference in its entirety.

[0046] As shown in Equation 1, the flight time is affected by airspeed and wind angle 20°. The radius r is constant, with acoustic receivers 14A-14L located at a fixed radius 16 and at an angle to acoustic transmitter 12. The speed of sound in the air is unaffected by wind angle or airspeed. Therefore, for a known airspeed, the only variable affecting the flight time of the acoustic pulse to acoustic receivers 14A-14L is the wind angle 20°.

[0047] The acoustic receiver 14 can be placed at any point relative to the transmitter 12 and can have any symmetrical, asymmetrical or random arrangement. Figure 1B This is a top view of the asymmetric acoustic air data sensor 21, including a transmitter 12, acoustic receivers 14M-14R, airflow 18, and wind angle 20 (e.g., angle of attack). The acoustic receiver pairs (e.g., 14M / 14N, 14O / 14P, 14Q, 14R) are randomly placed along the surface plane of the asymmetric acoustic air data sensor 21 at angles (e.g., θ1, θ2, and θ3) relative to the X-axis, with different distances (e.g., d1, d2, and d3) between each pair of acoustic receivers 14. In some embodiments, the transmitter 12 and two or more acoustic receivers 14 are arranged in a line (e.g., a straight line may pass through the transmitter and two or more acoustic receivers 14, such as...). Figure 1B (as in the example). In some embodiments, only one acoustic receiver 14 and transmitter 12 are arranged in a line. Any arrangement of the acoustic receiver 14 and transmitter 12 is possible. Therefore, the above description should not be construed as a limitation of this disclosure, but is merely illustrative.

[0048] Figure 2 Polar coordinate plot 22 is shown, including radial axis 24, angular axis 26, legend 28, and ellipses 30A-30E. For clarity and ease of discussion, it is described below in the context of the acoustic air data sensor 10 of Figure 1. Figure 2 .

[0049] Radial axis 24 indicates time in microseconds. Angular axis 26 indicates angle in degrees. Figure 28 matches each of ellipses 30A-30E to airspeed. Ellipses 30A-30E represent the time (flight time) for a pulse to travel from acoustic transmitter 12 to radius 16 based on an angle of attack 20° and a given airspeed. Ellipses 30A-30E represent the flight time at airspeeds of 0 m / s, 60 m / s, 120 m / s, 180 m / s, and 240 m / s, respectively. Ellipses 30A-30E can be derived using Equation 1, where the angle of attack is 20°, the radius is 0.05 m, and the speed of sound is 331.45 m / s.

[0050] like Figure 2 As shown, except for those angles of attack 90° with the wind angle 20, airspeed affects the flight time of the acoustic pulse at all angles. Ellipses 30A-30E have the same flight time at 110° and 290°. At an angle of attack 90° with the wind angle 20, the velocity term in Equation 1 is zero. This means that the speed of sound at an angle of attack 90° with the wind angle 20 can be determined by the following equation:

[0051] (Equation 2)

[0052] Figure 3 Figure 32 illustrates the time-of-flight difference between the relative acoustic receivers, including x-axis 34, y-axis 36, legend 38, and curves 40A-40F. Figure 32 depicts the difference (Δ) in the time of flight between the relative acoustic receivers R6 and R6+180°, given by the following formula:

[0053] (Equation 3)

[0054] The angle of attack is 20°, and the radius is 0.05 meters. X-axis 34 depicts the difference in flight time in microseconds. Y-axis 36 depicts the angle in degrees. Figure 38 matches each of curves 40A-40F to a given airspeed. Curves 40A-40F represent the difference in flight time of the relative acoustic receiver at airspeeds of 0 m / s, 60 m / s, 120 m / s, 180 m / s, 240 m / s, and 300 m / s, respectively. The zero-crossing point of each curve 40A-40F occurs at 90° with respect to the angle of attack. Curves 40A-40F can be represented by a polynomial. At 90° with respect to the angle of attack, the polynomial will equal zero.

[0055] Figure 4 A system diagram 42 is shown for an embodiment of the acoustic wind angle sensor 10 of FIG1, which includes an acoustic transmitter 12, an acoustic receiver 14A-14L, a delay circuit 44A-44L, a differential circuit 46A-46F, a polynomial fitting circuit 48, a zero-crossing circuit 50, and a subtraction circuit 52.

[0056] Acoustic transmitter 12 can provide electrical signals representing the waveform of the transmitted acoustic pulse to delay circuits 44A-44L. Acoustic receivers 14A-14L can provide signals representing the waveform of the acoustic pulse received from acoustic transmitter 12 to delay circuits 44A-44L. Delay circuits 44A-44L can extract the delay between the transmitted and received waveforms and provide the extracted delay to differential circuits 46A-46F. Each of the differential circuits 46A-46F can receive the extracted delay of a pair of opposing (180° apart) acoustic receivers. Differential circuits 46A-46F can determine the difference (Δθ) in the time of flight between each pair of opposing acoustic receivers and provide this difference to polynomial fitting circuit 48. For clarity, Figure 4 The relative timing of transmitted and received signals with overlapping delays (θ) and delay differences (Δθ) is shown.

[0057] The polynomial fitting circuit 48 can receive time-of-flight differences or phase differences from the differential circuits 46A-46F. Each time-of-flight difference represents two points, one on either side of zero, because the difference is associated with two acoustic receivers 180° apart. In some embodiments, the polynomial fitting circuit 48 determines the best least-squares polynomial fit for the two points. In another example, the polynomial fitting circuit 48 determines the polynomial based on a known curve. The acoustic receivers 14A-14L can be located with a known angle (Rθ) and a known radius 16. Because the variables used to determine the delay, and therefore the delay difference, are known except for the wind angle and airspeed, the delay difference curve is well established. This can be used... Figure 3The curves 40A-40F are used to depict the difference (Δ) in the time of flight between the relative acoustic receiver R6 and R6+180°, as given by Equation 3. The polynomial fitting circuit 48 provides the polynomial ( Zero-crossing circuit 50 receives a polynomial from polynomial fitting circuit 48. Zero-crossing circuit 50 determines the angle in which the polynomial crosses zero. Zero-crossing circuit 50 provides the angle in which the polynomial crosses zero to subtraction circuit 52. Subtraction circuit 52 receives the angle from zero-crossing circuit 50. Subtraction circuit 52 determines the wind angle (α) by subtracting 90° from the angle provided by zero-crossing circuit 50. The delay circuits 44A-44L, differential circuits 46A-46F, polynomial fitting circuit 48, zero-crossing circuit 50, and subtraction circuit 52, as described herein, can be implemented in hardware and / or software.

[0058] Figure 5 The pulse timing diagram 54 includes an acoustic transmitter waveform 56, an acoustic receiver waveform 58, and a corresponding acoustic receiver waveform 60. The acoustic transmitter waveform 60 may include an acoustic transmitter pulse 62. The acoustic receiver waveform 58 may include an acoustic receiver pulse 64. The corresponding acoustic receiver waveform 60 may include a corresponding acoustic receiver pulse 66.

[0059] Acoustic transmitter pulse 62 represents an acoustic pulse emitted by the acoustic transmitter of the acoustic angle-of-attack sensor. Acoustic receiver pulse 64 represents an acoustic pulse sensed by the first acoustic receiver. Opposite acoustic receiver pulse 66 represents an acoustic pulse sensed by the second acoustic receiver, which is 180° away from or opposite to the first acoustic receiver. This timing diagram illustrates the time between the emission of an acoustic pulse from the acoustic transmitter and the sensing of the acoustic pulse by each of the first and second acoustic receivers. The region of interest represents the time period in which acoustic receiver pulse 64 and opposite acoustic receiver pulse 66 are received. Acoustic receiver pulses from other acoustic receivers can be characterized similarly (e.g., pulses such as those from a third acoustic receiver).

[0060] Figure 6 Subsystems of two different embodiments of an acoustic air data sensor are depicted, including a delay subsystem 68 and a cross-correlation subsystem 70. The delay subsystem 68 includes an acoustic transmitter 72, acoustic receivers 74A and 74B, delay circuits 76A and 76B, and a differential circuit 78. The cross-correlation subsystem 70 includes acoustic receivers 74A and 74B, a cross-correlation circuit 80, and a maximum delay circuit 82.

[0061] The delay subsystem 68 and the cross-correlation subsystem 70 can be used interchangeably in an acoustic wind angle sensor. The delay subsystem 68 represents... Figure 4The system diagram 42 shows a subsystem of the acoustic angle-of-attack sensor system. Acoustic transmitter 72 represents acoustic transmitter 12, acoustic receivers 74A and 74B represent acoustic receivers 14A and 14G, delay circuits 76A and 76B represent delay circuits 16A and 16B, and differential circuit 78 represents differential circuit 18A. The delay subsystem 68 uses delay circuits 76A and 76B to determine the respective delays between the acoustic pulses emitted by acoustic transmitter 72 and the acoustic pulses received by acoustic receivers 74A and 74B. Differential circuit 78 determines the delay difference between acoustic receivers 74A and 74B based on these respective delays. ).

[0062] In contrast, the cross-correlation subsystem 70 uses cross-correlation circuit 80 to generate a correlation signal (ρ) using the signals provided by acoustic receivers 74A and 74B. The correlation signal represents the cross-correlation function of the signals provided by the acoustic receivers. The cross-correlation function indicates how similar two signals are based on shifting one of the signals in time by a given amount. As shown in the maximum delay diagram, the delay circuit 82 can determine the correlation corresponding to the delay difference (ρ). The peak correlation of the relevant signal. This can be found in... Figure 5 As seen in the diagram, shifting the relative receiver waveform 60 to the left on the time axis by a time equal to the delay difference will cause the acoustic receiver pulse 64 and the relative acoustic receiver pulse 66 to align, resulting in maximum correlation between the two signals. For example, correlation circuit 80 and maximum delay circuit 82 can be used in place of delay circuits 76A and 76B and differential circuit 78. In some embodiments, correlation circuit 80 can be used in place of delay circuits 76A, 76B and differential circuit 78.

[0063] Figure 7 This is a top view of an example acoustic air data sensor 84 that can be used when the wind angle for a given application has a known finite range. In this example, the wind angle limit 96 is ±30°. The acoustic angle of attack sensor 84 includes an acoustic transmitter 86, acoustic receivers 88A-88J, a radius 90, an airflow 92, an angle of attack 94, an angle of attack limit 96, and a mounting plate 98.

[0064] Acoustic receivers 88A-88J are positioned along a radius 90 orthogonal to the wind angle limit 96. This embodiment allows for the use of fewer acoustic receivers and / or a densely populated array of acoustic receivers without increasing the overall number of receivers. As shown, acoustic transmitter 86 and acoustic receivers 88A-88J can be arranged on mounting plate 98. This allows for easy installation and replacement of the acoustic angle-of-attack sensor 84, as the entire sensor can be immediately removed and replaced instead of being embedded, for example, in the aircraft fuselage. In some embodiments, acoustic transmitter 86 is an ultrasonic transmitter. Ultrasonic transmitters will not be audible to passengers. In some embodiments, acoustic receivers 88A-88J may include a high-pass filter to filter out audible noise. As shown, airflow 92 can pass unobstructed across the acoustic air data sensor 84, thereby reducing airflow disturbance and drag.

[0065] Figure 8 System diagram 100 includes an acoustic transmitter 86, acoustic receivers 88A-88J, analog-to-digital converters 102A-102E, cross-correlation circuits 104A-104E, maximum delay circuits 106A-106E, timing control circuit 108, polynomial fitting circuit 110, zero-crossing circuit 112, and computing device 113. For clarity and ease of discussion, Figure 7 The system is discussed in the context of the acoustic air data sensor 84 in Figure 100.

[0066] Timing control circuit 108 is configured to provide a pulse command to acoustic transmitter 86. Acoustic transmitter 86 can be configured to transmit an acoustic pulse in response to receiving the pulse command. Acoustic receivers 88A-88E can receive the acoustic pulse after a time delay affected by airspeed 92, as shown in Equation 1. Acoustic receivers 88A-88E provide receiver signals to analog-to-digital converters 102A-102E. Analog-to-digital converters 102A-102E can convert the receiver signals into digital waveforms. Analog-to-digital converters 102A-102E can provide digital waveforms to cross-correlation circuits 104A-104E. Cross-correlation circuits 104A-104E receive the digital waveforms. Cross-correlation circuits 104A-104E use the digital waveforms to determine a correlation signal (ρ). The correlation signal represents the cross-correlation function of the signals provided by the acoustic receivers. The cross-correlation function indicates how similar two signals are based on shifting one signal in the signals by a given amount in time. Cross-correlation circuits 104A-104E provide correlation signals to maximum delay circuits 106A-106D. Maximum delay circuits 106A-106D receive the cross-correlation signals. Maximum delay circuits 106A-106D determine the peak correlation of the correlation signals. The peak correlation corresponds to the delay difference of acoustic receivers 88A-88J. The maximum delay circuits 106A-106D provide delay differences to the polynomial fitting circuit 110. ).

[0067] Polynomial fitting circuit 110 receives time-of-flight differences from maximum delay circuits 106A-106D. Each time-of-flight difference represents two points, one on either side of zero, because the difference is associated with two acoustic receivers 180° apart. In one example, polynomial fitting circuit 110 determines the best least-squares polynomial fit for the two points. In another example, polynomial fitting circuit 48 determines the polynomial based on a known curve. Acoustic receivers 88A-88E are positioned with a known angle (Rθ) and a known radius 90. Because the variables used to determine the delay, and therefore the delay difference, are known except for the angle of attack and airspeed, the delay difference curve is well established. Polynomial fitting circuit 110 provides the polynomial ( Zero-crossing circuit 112 receives a polynomial from polynomial fitting circuit 110. Zero-crossing circuit 112 determines the angle (α) at ​​which the polynomial crosses zero. Zero-crossing circuit 112 provides the angle at which the polynomial crosses zero to computing device 113. The computing device may be an aircraft controller, engine controller, or other computing device. Analog-to-digital converters 102A-102E, cross-correlation circuits 104A-104E, maximum delay circuits 106A-106E, timing control circuit 108, polynomial fitting circuit 110, zero-crossing circuit 112, and computing device 113, as described herein, may be implemented in hardware and / or software, such as a processor executing instructions of computer-readable storage.

[0068] Figure 9 This is a flowchart of an embodiment of the acoustic wind angle sensing process 114. For the purposes of clarity and ease of discussion, in Figure 8 The wind angle sensing process 114 is discussed in the context of system diagram 100. At step 116, an acoustic pulse may be emitted by acoustic transmitter 86. In one example, the acoustic pulse is emitted by acoustic transmitter 86 in response to receiving a pulse command from timing control circuitry 108. At step 118, the acoustic pulse may be received by acoustic receiver 88A. At step 120, acoustic receiver 88A may provide a receiver signal in response to receiving the acoustic pulse. At step 122, acoustic receiver 88F may receive the acoustic pulse. At step 124, acoustic receiver 88F may provide a receiver signal in response to receiving the acoustic pulse. At step 126, the delay difference between the first and second receiver signals may be determined. In some examples, the following can be used: Figure 4The delay circuit 44A and differential circuit 46A are used to determine the delay difference. In other examples, cross-correlation circuit 104E and maximum delay circuit 106E can be used to determine the delay difference. At step 128, the wind angle (e.g., AOA) is determined based on the delay difference. In some examples, the delay difference can be used to determine a polynomial using polynomial fitting circuit 110. Zero-crossing circuit 112 can determine the angle at which the polynomial equals zero to determine the wind angle. At step 130, the wind angle can be provided to computing device 113. In some embodiments, computing device 113 can be an aircraft computer or any other suitable device. It should be understood that more than two acoustic receivers can be used to determine the wind angle. For example, a third acoustic receiver can receive acoustic pulses and provide a receiver signal in response to the acoustic pulses.

[0069] Therefore, by implementing certain techniques of this disclosure, acoustic air data sensors can be used to accurately determine wind angles without obstructing airflow or using mechanically moving parts. Using acoustic air data sensors as described herein provides high bandwidth and rate-of-update measurements of angle of attack without placing the sensor assembly directly in the airflow. This reduces the risk of icing for the angle-of-attack sensor and minimizes airflow disturbance and drag.

[0070] According to at least one aspect of this disclosure, one or more embodiments of the air data sensor system 500 can be used to determine airspeed and / or other air data parameters. For example, referring to... Figure 10 The acoustic airspeed sensor system 500 may include at least one acoustic transmitter 12 (T) configured to provide acoustic pulses and a plurality of acoustic receivers, such as 14A-14K as shown in FIG1. ​​One or more receivers may include at least a first acoustic receiver (e.g., 14A) located at a first radial distance from at least one acoustic transmitter 12 (e.g., downstream in operation) and a second acoustic receiver (e.g., 14B) located at a second radial distance from at least one acoustic transmitter 12 (e.g., downstream in operation).

[0071] A first acoustic receiver can be configured to receive an acoustic pulse 501 at a first time and output a first receiver signal 503. A second acoustic receiver is configured to receive an acoustic pulse 501 at a second time and output a second receiver signal 505. A third acoustic receiver is configured to receive an acoustic pulse 501 at a third time and output a third receiver signal 506. The sensor system 500 may include a computing unit 507 operatively connected to the first, second, and third acoustic receivers. The computing unit 507 includes one or more processors and a memory communicatively coupled to the one or more processors. The memory stores instructions for the one or more processors to perform the tasks described herein. The computing unit 507 may perform all computing tasks within a centralized component (e.g., an integrated circuit) or within a set of modules, each module including the electronic circuitry required to perform a specific computing task.

[0072] The calculation unit 507 is configured to receive a first receiver signal 503, a second receiver signal 505, and a third receiver signal 506; determine a first propagation time between receiving the first receiver signal and transmitting an acoustic pulse 501 by the acoustic transmitter 12; determine a second propagation time between receiving the second receiver signal and transmitting an acoustic pulse 501 by the acoustic transmitter 12; and determine a third propagation time between receiving the third receiver signal and transmitting an acoustic pulse 501 by the acoustic transmitter 12. The calculation unit 507 is configured to determine the first propagation time, the second propagation time, and the propagation time of the third signal via any known method or combination of known methods. For example, the calculation unit 507 may be configured to determine the propagation time based on changes in the signal amplitude. In another example, the calculation unit 507 may be configured to determine the propagation time based on changes in the signal phase. In yet another example, the calculation unit may be configured to determine the propagation time based on the difference between the time the signal is transmitted and the time it is received.

[0073] The calculation unit 507 can be configured to receive or determine the wind angle. For example, the calculation unit 507 may include any suitable circuitry described above to determine the wind angle (e.g., AOA). The calculation unit 507 can be configured to determine the airspeed (e.g., True Airspeed (TAS), Equivalent Airspeed (EAS), or Calibrated Airspeed (CAS)) based on a first propagation time, a second propagation time, and the wind angle, and output an airspeed signal indicating the airspeed.

[0074] In some embodiments, the computing unit 507 may include one or more propagation measurement modules 509 (e.g., which may resemble the delay circuit described above) operatively connected to the pulse control module 511 and the first, second, and / or third acoustic receivers. As shown, each receiver may include a dedicated delay measurement module 509. Any other suitable number of propagation measurement modules 509 is considered herein. The pulse control module 511 may be operatively connected to the transmitter 12 and configured to cause the transmitter 12 to transmit an acoustic pulse 501 at a transmission time. One or more propagation measurement modules 509 may be configured to compare the transmission time with a first time to determine a first propagation time and output first propagation data 513 indicating the first propagation time. One or more propagation measurement modules 509 may be configured to compare the transmission time with a second time to determine a second propagation time and output second propagation data 515. One or more propagation measurement modules 509 may be configured to compare the transmission time with a third time to determine a third propagation time and output third propagation data 516.

[0075] The calculation unit 507 may include a wind angle module 517 operatively connected to one or more propagation measurement modules 509 to receive first propagation data 513, second propagation data 515, and third propagation data 516. The wind angle module 517 may be configured to determine the wind angle based on the first propagation data 513, second propagation data 515, and third propagation data 516, and output wind angle data 519 (e.g., to an aircraft computer and / or other modules). The calculation unit 507 may include a curve fitting module 521 configured to perform curve fitting on the first propagation data 513, second propagation data 515, and third propagation data, and output the curve fitting data 523 to the wind angle module 517.

[0076] The calculation unit 507 may include an airspeed module 525, which is operatively connected to the wind angle module 517 to receive wind angle data 519 therefrom. The airspeed module 525 may be operatively connected to one or more propagation measurement modules 509 to receive first propagation data 513, second propagation data 515, and third propagation data 516. The airspeed module 525 may be configured to determine airspeed based on the wind angle data 519, the first propagation data 513, the second propagation data 515, and the third propagation data 516, and output an airspeed signal 527 (e.g., to an aircraft computer and / or other modules).

[0077] The computing unit 507 may include a sound velocity module 529, which is operatively connected to the airspeed module 525 to receive an airspeed signal 527. The sound velocity module 529 may be operatively connected to one or more propagation measurement modules 509 to receive first propagation data 513, second propagation data 515, and third propagation data 516. The sound velocity module 529 may also be operatively connected to a wind angle module 517 to receive wind angle data 519. The sound velocity module 517 may be configured to determine the speed of sound based on the airspeed signal 527, the first propagation data 513, the second propagation data 515, and the third propagation data 516, and output sound velocity data 531 (e.g., to an aircraft computer and / or other modules).

[0078] The sound speed module 529 can be configured to determine the Mach number based on the sound speed and output a Mach number signal 533 (e.g., to an aircraft computer and / or other modules). The computing unit 507 may include a static air temperature module 535 operatively connected to the sound speed module 529 to receive sound speed data 531, determine the static air temperature based on the sound speed data 531, and output a static air temperature signal 537 (e.g., to an aircraft computer and / or other modules).

[0079] In some embodiments, the computing unit 507 may include a multiplexer 539 between one or more propagation measurement modules 509 and at least one other module (e.g., Figure 10 The multiplexer 539 can be configured to receive first propagation data 513 and second propagation data 515 from one or more propagation measurement modules and multiplex the data (e.g., for output to consumption modules, such as wind angle module, airspeed module and sound speed module).

[0080] In some embodiments, the computing unit is configured to construct a propagation function for calculating the true airspeed. The propagation function can be constructed by inputting several types of data. For example, the propagation function may include data relating to the position of the acoustic transmitter relative to a first acoustic receiver, a second acoustic receiver, and / or a third acoustic receiver. In another example, the propagation function may further include data relating to the amplitude of the first receiver signal / pulse, the second receiver signal / pulse, or the third receiver signal / pulse relative to the amplitude of a test signal / pulse. In yet another example, the propagation function may further include data relating to the phase shift of the first receiver signal / pulse, the second receiver signal / pulse, or the third receiver signal / pulse relative to the test signal / pulse. The propagation function may also include data relating to wind angle (e.g., angle of attack) and / or sound speed.

[0081] In some embodiments, the computation unit 507 may use a beamforming algorithm when generating the propagation function. Beamforming is a data processing technique that has been widely used in radar and acoustics. Traditionally, beamforming algorithms use a hypothetical propagation function and a known receiver location to determine the location of an unknown source (e.g., a transmitter). These same beamforming algorithms can also be rearranged so that if both the receiver and transmitter locations are known and the receiver signal / pulse has been characterized (e.g., by determining the phase and / or amplitude of the receiver signal / pulse, as well as the angle of attack and speed of sound), the propagation function can be determined.

[0082] Beamforming algorithms are particularly well-suited for considering the effects of boundary layers on airspeed measurements in anemometers that are flush with or nearly flush with the aircraft surface. The boundary layer is the layer of air close to the surface or skin of a flying aircraft, varying from zero velocity to free-flow velocity, such as… Figure 11 As shown in the diagram, this gradient of airspeed within the boundary layer makes it difficult to accurately determine the true airspeed using conventional calculation methods with flush or near-flush instruments, thus necessitating the use of other calculation methods, such as beamforming algorithms.

[0083] The beamforming algorithm used in generating the propagation function can include any known beamforming algorithm, including but not limited to classical beamforming algorithms, Capon algorithms, MUSIC algorithms, root-MUSIC algorithms, Bartlett algorithms, ESPIRIT algorithms, Min-Norm algorithms, Burg algorithms, SAMV algorithms, Welch algorithms, time-reversal MUSIC algorithms, MVDR algorithms, Akaike information criterion algorithms, and minimum description length (MDL) criterion algorithms. Beamforming algorithms can also include newly described beamforming algorithms.

[0084] Typically, beamforming algorithms used to determine the propagation function can include equations where the signal at each microphone is a function of the number of discrete sources multiplied by the convolution integral of the propagation function (e.g., Green's function) between each source: .here, t It is the time of transmission. x s Describes the vector coordinates of each transmitter, μ n ( t ) is in x n The propagation response of each receiver at the location (e.g., x n Defined as the vector coordinates of each receiver. Cn(x) n ） It is a receiver （n） and in x s The propagation function (e.g., Green's function) between emitters at a given point. For linear propagation without flow, the propagation function can be defined as:

[0085] (Equation 1)

[0086] in, σ(x) n ，x s ） It is x n The receiver and x at the location s The propagation time between transmitters at a given location (e.g., typically a function of the speed of sound and the distance between the transmitter and receiver), D(x n x s ) is x n The receiver and x at the location s The amplitude factor between transmitters at a given location (e.g., typically a function of source directivity and distance between transmitter / receiver), and 𝜔 is the wind angle (e.g., angle of attack).

[0087] In some embodiments, the beamforming-based equations used to determine the propagation function and / or true wind speed assume that only a single transmitter is used with multiple receivers, and that the timing of the acoustic pulses is known. The beamforming-based equations also assume that the propagation function is measured via a known absence of airflow, and that the propagation function during flight is a function of airspeed, wind angle (e.g., angle of attack), and the local sound speed outside the boundary layer. There are also assumptions that the signal-to-noise ratio is sufficient (e.g., both propagation time and amplitude can be measured).

[0088] In some embodiments, the acoustic airspeed sensor system 500 includes a phase / amplitude module communicatively coupled to and / or included within a computing unit 507, configured to determine the phase of an acoustic wave and / or determine the difference in phase between an acoustic pulse and a test pulse (e.g., a pulse measured under windless conditions) received at a first, second, or third acoustic receiver. A phase-shifting module includes an oscilloscope configured to measure the phase of the acoustic pulse at the first, second, and / or third acoustic receiver. Circuitry within the phase-shifting module and / or computing unit 507 can be configured to calculate the difference between the phase of the received test pulse and the received acoustic pulse from the first, second, and third acoustic receivers. Once the phase shift has been determined, the difference (Δt) in the propagation time between the test pulse and the acoustic pulse can be calculated. The oscilloscope method for determining the phase shift of wind speed has been practiced for decades and is extensively described in R.M. Schotland's manuscript "The Measurement of Wind Velocity by Sonic Means" (Vol. 12, pp. 386-390, which is incorporated in its entirety). The phase / amplitude module can also be configured to measure the amplitude of a received acoustic pulse via an oscilloscope and determine the difference between the amplitude of the received acoustic pulse and the amplitude of a test pulse. The calculated difference in amplitude between the pulses can then be used in the determination of wind speed or other characteristics.

[0089] As described above, in some embodiments, at least two of the first radial distance, second radial distance, and third radial distance of receivers 14A-14K may be the same. However, it is contemplated that varying radial distances may be used to determine certain air data parameters (e.g., airspeed). For example, the first receiver (e.g., 14A), the second receiver (e.g., 14B), and / or any other additional receivers (e.g., 14C-14K) may be arranged in a circular pattern around transmitter 12.

[0090] In some embodiments, the pattern need not be circular. For example, the radial distance from the transmitter to all receivers need not be a fixed distance. Each receiver can be placed at a different known radial distance. Then, all measured transmission delays can be normalized to any fixed reference distance. As a non-limiting example, if the first receiver is at 1 cm and the second receiver is at 4 cm, both can be normalized to a fixed reference distance of, for example, 2 cm. In this example, the measured delay of the first receiver will be doubled (delay = 2 cm / 1 cm), and the measured delay of the second receiver will be halved (delay = 2 cm / 4 cm). If all receivers are located at 2 cm, then such a new delay number is actually what will have been measured. This is one way to allow non-circular patterns of receivers. The receivers still span multiple angles. Any other suitable embodiments that allow non-circular receivers are considered herein.

[0091] In some embodiments, one or more of the receivers (e.g., 14A-14K) may include a microelectromechanical system (MEMS) microphone. Any other suitable type of acoustic receiver is considered herein.

[0092] For further reference Figure 12 Under certain operating conditions (e.g., as a function of wind angle and airspeed), some receivers may be blocked. The dashed areas relative to the polar plot above indicate receivers at certain locations that will be blocked due to wind angle and airspeed. When selecting the number and location of receivers, consider that only receivers that are not blocked under all operating conditions can be used in the sensor, rather than the entire circle of receivers (e.g., such as...). Figure 7 The embodiments shown in the embodiments are as follows.

[0093] In some embodiments, the calculation unit 507 may be configured to determine whether the acoustic receiver is blocked, for example, by setting a maximum time for the response. The calculation unit 507 may ignore any signals from the blocked acoustic receiver, such that spurious data or noise is not taken into account when determining air data parameters (e.g., wind angle and airspeed).

[0094] For further reference Figure 13 The illustration shows an embodiment of the placement of one or more sensors. As shown, in some embodiments, one or more sensors may be placed on one side of the aircraft (e.g., where a pitot tube is installed, so that airflow remains attached to the fuselage and / or where overhead airflow will not be obstructed). As shown, multiple sensor locations can be used to determine both the angle of attack and the slip angle.

[0095] In the embodiments of the systems disclosed herein, the transmitter is upstream of all receivers used to determine, for example, airspeed. This is not the case for conventional acoustic sensors, and allows operation at airspeeds above approximately Mach 0.2.

[0096] A computer-implemented method may include: transmitting an acoustic pulse using at least one acoustic transmitter; receiving the acoustic pulse at a first time using a first acoustic receiver located at a radial distance from the at least one acoustic transmitter; providing a first receiver signal from the first acoustic receiver in response to receiving the acoustic pulse; receiving the acoustic pulse at a second time using a second acoustic receiver located at a radial distance from the at least one acoustic transmitter; and providing a second receiver signal from the second acoustic receiver in response to receiving the acoustic pulse. The computer-implemented method may further include: receiving the acoustic pulse at a third time using a third acoustic receiver located at a radial distance from the at least one acoustic transmitter; and providing a third receiver signal from the third acoustic receiver in response to receiving the acoustic pulse.

[0097] The method may include determining a first propagation time between a first acoustic receiver and an acoustic transmitter, determining a second propagation time between a second acoustic receiver and an acoustic transmitter, and determining a third propagation time between a third acoustic receiver and an acoustic transmitter.

[0098] The method may include constructing a propagation function based on at least one of the following: the position of at least one acoustic transmitter relative to at least one of a first receiver, a second receiver, or a third receiver; the amplitude of at least one of a first receiver signal, a second receiver signal, or a third receiver signal; or the phase of at least one of a first receiver signal, a second receiver signal, or a third receiver signal.

[0099] The method may include determining airspeed based on a first propagation time, a second propagation time, a third propagation time, and a wind angle, and outputting the airspeed signal to the aircraft system.

[0100] The method may include receiving the wind angle, or determining the wind angle based on a first propagation time, a second propagation time, or a third propagation time. The method may also include determining the speed of sound based on wing angle, airspeed, a first propagation time, a second propagation time, or a third propagation time.

[0101] This method may include determining the Mach number based on the speed of sound and outputting that Mach number to the aircraft system. This method may also include determining the static air temperature based on the speed of sound and outputting the static air temperature to the aircraft system.

[0102] An ultrasonic acoustic system is disclosed that directly measures aircraft airspeed and relative wind angle (e.g., angle of attack or sideslip angle). This design has no pitot tube probe or moving mechanical parts, typical of conventional pressure-based air data systems and wind vane sensor designs. This information can be used to construct aircraft airspeed and wind angle by measuring the acoustic time-of-flight / phase modulation and the signal strength of the acoustic pulse across the angle and distance of a horizontal surface.

[0103] As shown in Figure 1, by placing a ring of ultrasonic receivers (microphones) at a fixed radius r around the transmitter, the flight time of the acoustic pulse at each receiver can be measured. The flight time of the acoustic pulse from the transmitter T to the receiver Rθ placed at an angle θ is also shown. It is given by the following formula: (e.g., V ≥ 0, and C0 ≥ 0), where C0 is the speed of sound, V is the airspeed, α is the relative wind angle, and r is the separation radius. This is the delay equation, which defines the fundamental relationship between these air data parameters and the actual acoustic pulse arrival time delay between the transmitter and multiple receivers. In some embodiments, as shown in Figure 1, the geometry of the receiver Rθ can be a circular pattern from the transmitter T at a radius r and a fixed angle θ. Embodiments for finding one or more air data parameters may include an incremental approach, first receiving or determining the wind angle (e.g., angle of attack), then using the wind angle to determine the true airspeed (e.g., real air velocity), then optionally using the wind angle and true airspeed to determine the speed of sound, and then optionally using the speed of sound to determine the static air temperature.

[0104] The embodiments for determining the wind angle have been disclosed above. Additional embodiments for the process of determining the wind angle are described below.

[0105] Even if the true angle of attack or other wind angle is not aligned with any receiver, we can still interpolate to estimate the angle. This is because the delay equation is minimized at the angle of attack (i.e., ...). ), and it is symmetric about α (i.e.: This indicates that the fitted receiver delay is surrounded by a parabola around the minimum. Since each receiver delay measurement will be corrupted by measurement noise, and the minimum may occur between two receivers, it is best to fit a function curve to the receiver delay and extract the minimum from the fitted function. Fit this to a second-order equation: It has a minimum value at θ = −(b / 2a).

[0106] The minimum measurement delay and its receiver angle are represented as points. Then, represent the point on any of its corner sides as and This yields the formula for estimating the angle of attack: .

[0107] The following describes an embodiment of the process for determining True Airspeed (TAS). For any two different receiver delays... and Their reciprocal difference is: And solve for the true airspeed estimate: .

[0108] The following describes an embodiment of the process for determining the speed of sound (SOS). For any two different receiver delays... and Their reciprocals sum to And solve for the speed of sound estimation: .

[0109] For numerical reasons, ideally, a pair of receivers would be selected on opposite sides of the receiver circle, both perpendicular to the angle of attack. Since not all receivers will produce a delay measurement due to shielding effects, a second-best option is to select a pair that is as close as possible to 180 degrees apart and as close as possible to 90 degrees away from α. As will be understood by those skilled in the art, the Mach number can be determined using the actual airspeed and the speed of sound.

[0110] An embodiment of the process for determining static air temperature (SAT) using the speed of sound in knots is used, and then the static air temperature in degrees Celsius is estimated as follows: ,in Or equivalent to the speed of sound in meters per second per degree Celsius: ,in .

[0111] Signal loss between the transmitter and any receiver is driven by geometric scattering, molecular absorption, and turbulent scattering. The first two effects are omnidirectional and therefore affect all receivers equally. Geometric scattering is caused by the outward diffusion of sound energy as it propagates from its source. Molecular absorption is caused by the conversion of sound energy into heat as sound waves propagate through the air.

[0112] Turbulent scattering is directional and caused by local gradients in wind speed and temperature. As sound waves propagate through the air, turbulent scattering causes fluctuations in the phase and amplitude of the sound waves. Because the transmitter and receiver are flush-mounted, the velocity boundary layer effect will bend sound waves propagating upstream away from the mounting surface and downstream into the mounting surface. This bending results in an increase in signal strength in the downstream receiver and a loss or blockage of signal strength in the upstream receiver. Sound propagating at right angles to the airflow is not bent. Only at low airspeeds will all receivers have sufficient signal strength to separate the acoustic impulse from background noise. At higher airspeeds, the upstream receiver will be "blocked" due to signal loss through the air. Figure 12As shown, this shielding effect becomes more pronounced at higher airspeeds. The faster the speed, the less signal a receiver far from the velocity vector will receive, and thus be effectively shielded. The shielded portion of the arc can be called the "wedge angle," and may not always require a sensor to be shielded (e.g., for normal operation in commercial aircraft, beyond approximately 90 degrees of the wedge angle).

[0113] Similarly, if the base is warmer than the surrounding air, the temperature gradient effect will block the receiver, and if the base is cooler than the surrounding air, the temperature gradient effect will strengthen the signal. Thermal gradient blocking is a transient effect because the base temperature will be cooled due to the large airflow. Due to this blocking effect, all airspeed information needs to be extracted from delayed data collected from an unblocked receiver.

[0114] Using receiver pairs spaced 180° apart directly contradicts the typical approach to acoustic wind measurements. As mentioned above, the delay measurement logic could include a threshold time at which the receivers are assumed to never receive a signal, then determine that the receivers are "masked" and enter an empty entry.

[0115] As described herein, the pulse command from the pulse control timing logic of the pulse control module 511 can be converted into an acoustic pulse by the transmitter 12. The pulse control module 511 can create a shaped waveform designed to be robust to ambient noise, allowing the propagation measurement module 509 to extract pulse timing information even in the presence of noise interference. The pulse control module 509 can also timestamp the pulse transmission time, allowing the pulse arrival time to be determined by module 509. The propagation measurement module 509 can extract the delay between the transmitter pulse command and the received waveform and output the time delay between them as... For clarity, Figure 5 The relative timing of the transmitted and received signals is shown. For illustrative purposes, the pulse shape depicted is a sine wave train, but it could also be a simple Gaussian pulse or a more complex pattern, depending on the difficulty of extracting the received pulse from the background noise.

[0116] As described above, each delay measurement module may include an analog-to-digital converter that samples at a sufficient rate to determine the delay time with sufficient resolution for accurate airspeed measurement (e.g., in fractions of a microsecond). Multiplexer 539 can collect the measured delay times / data into an indexable list. Masked receiver delays can be included in the list as empty entries, allowing subsequent boxes to dynamically adapt to varying lengths and distributions of unmasked entries.

[0117] The curve fitting module 521 can accept a set of delay differences as shown, where the delay differences are points along a line in a curve. The curve fitting module 521 can determine the best least-squares fit for the non-empty list entries, and the resulting output parameters can be defined as follows: The equation of the curve.

[0118] The wind angle module 517 can use curve fitting functions. The airspeed module 525 calculates the angle α, where the function is minimized as described above. This minimized angle can be output as the wind angle α. The airspeed module 525 uses the delay list of wind angle estimation and measurement from the wind angle module 517. To calculate the true airspeed V, as described above.

[0119] The sound speed module 529 can use the estimated wind angle and the true airspeed to calculate the estimated sound speed C0, as described above. The estimated true airspeed is divided by C0 to calculate the Mach number m. The static air temperature module 535 can calculate the static temperature (Ts), as described above.

[0120] The use of an ultrasonic angle-of-attack sensor design that captures the time-of-flight of acoustic pulses at multiple angles relative to the aircraft's airflow offers the following benefits: a single unit can measure true airspeed and wind angle (e.g., angle of attack or sideslip angle); direct measurement of sound speed to calculate current, Mach number, and static air temperature; unobstructed airflow across the sensor; elimination of airflow disturbances and drag; no mechanical moving parts, resulting in higher bandwidth and wind angle update rate; lower de-icing requirements because no sensor components directly face the airflow; and true positive fault detection compared to a pitot tube hydrostatic port icing to a fixed, reasonable but erroneous pressure when the receiver cannot extract the pulse signal (due to various reasons, including icing).

[0121] As those skilled in the art will understand, aspects of this disclosure can be implemented as a system, method, or computer program product. Therefore, aspects of this disclosure can take the form of a completely hardware embodiment, a completely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which can be referred to herein as a “circuit,” “module,” or “system.” A “circuit,” “module,” or “system” can include one or more portions of one or more separate physical hardware and / or software components that can together perform the functions of the disclosed “circuit,” “module,” or “system,” or a “circuit,” “module,” or “system” can be a single self-contained unit (e.g., hardware and / or software). Furthermore, aspects of this disclosure can take the form of a computer program product implemented on one or more computer-readable media on which computer-readable program code is implemented.

[0122] Any combination of one or more computer-readable media may be used. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any suitable combination of the foregoing. More specific examples (not an exhaustive list) of computer-readable storage media will include the following: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium can be any tangible medium that can contain or store programs for use by or in conjunction with an instruction execution system, apparatus, or device.

[0123] Computer-readable signal media may include, for example, propagated data signals having computer-readable program code implemented therein, in baseband or as part of a carrier wave. Such propagated signals may take any of a variety of forms, including, but not limited to, electromagnetic, optical, or any suitable combination thereof. A computer-readable signal medium may be any computer-readable medium that is not a computer-readable storage medium and may transmit, propagate, or transfer a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0124] Program code implemented on a computer-readable medium can be transmitted using any suitable medium, including but not limited to wireless, wired, fiber optic cable, RF, or any suitable combination thereof.

[0125] Computer program code for performing operations relating to the aspects of this disclosure may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, Smalltalk, C++, or the like, and traditional procedural programming languages ​​such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partially on the user's computer as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0126] The aspects of this disclosure have been described above with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It will be understood that each block in any flowchart illustration and / or block diagram, and any combination of blocks in a flowchart illustration and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus to produce a machine such that the instructions, executable via the processor of the computer or other programmable data processing apparatus, create means for implementing the function / action specified in any of the flowchart and / or one or more block diagram blocks.

[0127] These computer program instructions may also be stored in a computer-readable medium that can instruct a computer, other programmable data processing apparatus or other device to operate in a particular manner, such that the instructions stored in the computer-readable medium produce an article of writing including instructions that implement the functions / actions specified in the flowchart and / or one or more block diagram frames.

[0128] Computer program instructions may also be loaded onto a computer, other programmable data processing apparatus or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide a process for implementing the function / action specified herein.

[0129] It should be understood that embodiments of the methods disclosed herein may include one or more of the steps described herein. Furthermore, such steps may be performed in any desired order, and two or more steps may be performed simultaneously with each other. Two or more steps disclosed herein may be combined in a single step, and in some embodiments, one or more steps may be performed as two or more sub-steps. In addition, other steps or sub-steps may be performed in addition to, or as alternatives to, the steps disclosed herein.

[0130] Those skilled in the art will understand that any numerical value disclosed herein can be an exact value or a value within a range. Furthermore, any approximate terms used in this disclosure (e.g., “approximately,” “about,” “about”) can refer to the value within a range. For example, in some embodiments, this range can be within (positive or negative) 20%, or within 10%, or within 5%, or within 2%, or within any other suitable percentage or amount as understood by those skilled in the art (e.g., for known tolerance limits or error ranges).

[0131] Although the inventive concept has been described with reference to embodiments illustrated in the accompanying drawings, equivalents and substitutions may be used without departing from the scope of the claims. The components illustrated and described herein are merely examples of systems / devices and components that can be used to implement embodiments of the inventive concept and may be replaced with other devices and components without departing from the scope of the claims. Furthermore, any dimensions, degrees, and / or numerical ranges provided herein are to be understood as non-limiting examples unless otherwise specified in the claims.

Claims

1. An acoustic airspeed sensor system, comprising: At least one acoustic transmitter is configured to provide acoustic pulses; Multiple acoustic receivers, including at least: A first acoustic receiver is located at a first radial distance from at least one acoustic transmitter, and the first acoustic receiver is configured to: receive an acoustic pulse at a first time; and output a first receiver signal; A second acoustic receiver is located at a second radial distance from at least one acoustic transmitter, and the second acoustic receiver is configured to: receive an acoustic pulse at a second time; and output a second receiver signal; A third acoustic receiver, located at a third radial distance from at least one acoustic transmitter, is configured to: receive an acoustic pulse at a third time; and output a third receiver signal; and A computing unit operatively connected to a first acoustic receiver, a second acoustic receiver, and a third acoustic receiver, the computing unit comprising: One or more processors; and A memory communicatively coupled to one or more processors, and storing instructions thereon that, when executed by the one or more processors, cause the one or more processors to: Receive signals from the first receiver, the second receiver, and the third receiver; Determine the first propagation time between receiving a signal from a first receiver and emitting an acoustic pulse from at least one acoustic transmitter; Determine the second propagation time between receiving a signal from the second receiver and emitting an acoustic pulse from at least one acoustic transmitter; Determine the third propagation time between receiving a signal from a third receiver and emitting an acoustic pulse from at least one acoustic transmitter; A propagation function is constructed for propagation between at least one acoustic transmitter and at least one of a first acoustic receiver, a second acoustic receiver, or a third acoustic receiver when the aircraft is in flight. The propagation function is constructed using a beamforming algorithm, taking into account the influence of boundary layers adjacent to the aircraft's surface, and is constructed based on at least the following: The position of at least one acoustic transmitter relative to at least one of the first acoustic receiver, the second acoustic receiver, and the third acoustic receiver; The amplitude of at least one of the first receiver signal, the second receiver signal, or the third receiver signal; and The phase of at least one of the first receiver signal, the second receiver signal, or the third receiver signal; Receive or determine the wind angle; and Airspeed is determined based on the propagation function and at least one of the first propagation time, second propagation time, third propagation time, and wind angle, and an airspeed signal indicating the airspeed is output.

2. The acoustic pitot sensor system of claim 1, wherein, The computing unit includes one or more propagation measurement modules operatively connected to a pulse control module and at least one of a first acoustic receiver, a second acoustic receiver, or a third acoustic receiver. The pulse control module is operatively connected to at least one acoustic transmitter and configured to transmit an acoustic pulse at a transmission time. The one or more propagation measurement modules are configured to compare the transmission time and a first time to determine a first propagation time and output first propagation data. The one or more propagation measurement modules are configured to compare the transmission time and a second time to determine a second propagation time and output second propagation data. The one or more propagation measurement modules are configured to compare the transmission time and a third time to determine a third propagation time and output third propagation data.

3. The acoustic airspeed sensor system according to claim 2, wherein, The calculation unit includes a wind angle module, which is operatively connected to one or more propagation measurement modules to receive first propagation data, second propagation data, and third propagation data, and is configured to determine the wind angle based on the first propagation data, second propagation data, and third propagation data and output the wind angle data.

4. The acoustic airspeed sensor system according to claim 3, wherein the computing unit includes an airspeed module operatively connected to a wind angle module to receive wind angle data therefrom, wherein the airspeed module is operatively connected to one or more propagation measurement modules to receive first propagation data, second propagation data, and third propagation data, wherein the airspeed module is configured to determine airspeed based on wind angle, first propagation data, second propagation data, and third propagation data, and output an airspeed signal.

5. The airspeed sensor system according to claim 4, wherein the computing unit includes a sound speed module, the sound speed module being operably connected to the airspeed module to receive airspeed signals, wherein the sound speed module is operably connected to one or more propagation measurement modules to receive first propagation data, second propagation data, and third propagation data, wherein the sound speed module is operably connected to one or more propagation measurement modules to receive first propagation data, second propagation data, and third propagation data, wherein the sound speed module is operably connected to a wind angle module to receive wind angle data, wherein the sound speed module is configured to determine the sound speed based on the wind speed data, the first propagation data, the second propagation data, and the third propagation data, and output the sound speed data.

6. The airspeed sensor system of claim 5, wherein the sound speed module is configured to determine the Mach number based on the sound speed and output a Mach number signal.

7. The airspeed sensor system according to claim 6, wherein, The calculation unit includes a static air temperature module, which is operatively connected to a sound speed module to receive sound speed data, determine the static air temperature based on the sound speed, and output a static air temperature signal.

8. The airspeed sensor system according to claim 2, wherein, The computing unit includes a multiplexer between one or more propagation measurement modules and at least one other module, the multiplexer being configured to receive first propagation data, second propagation data and third propagation data from one or more propagation measurement modules and to multiplex the first propagation data, second propagation data and third propagation data.

9. The airspeed sensor system according to claim 1, wherein two of the first radial distance, the second radial distance, or the third radial distance are equivalent.

10. The airspeed sensor system of claim 1, wherein at least one of the first acoustic receiver, the second acoustic receiver, or the third acoustic receiver includes a microelectromechanical system (MEMS) microphone.

11. The airspeed sensor system according to claim 1, wherein, The computing unit is configured to determine whether the acoustic receiver is blocked by setting a maximum time for the response, and to ignore one or more signals from the blocked acoustic receiver.

12. The acoustic airspeed sensor system according to claim 1, wherein, Beamforming algorithms include classical algorithms, Capon algorithms, MUSIC algorithms, root-MUSIC algorithms, Bartlett algorithms, ESPIRIT algorithms, Min-Norm algorithms, Burg algorithms, SAMV algorithms, Welch algorithms, time-reversal MUSIC algorithms, MVDR algorithms, Akaike information criterion algorithms, or minimum description length (MDL) criterion algorithms.

13. The system according to claim 1, wherein, At least one acoustic transmitter and at least one of a plurality of acoustic receivers are configured to be flush-mounted on the surface of the aircraft.

14. A computer-implemented method, comprising: Use at least one acoustic transmitter to emit acoustic pulses; At the first time point, an acoustic pulse is received using a first acoustic receiver located at a first radial distance from at least one acoustic transmitter; In response to receiving an acoustic pulse, a first receiver signal is provided from the first acoustic receiver; At the second time point, an acoustic pulse is received using a second acoustic receiver located at a second radial distance from at least one acoustic transmitter; In response to receiving an acoustic pulse, a second receiver signal is provided from the second acoustic receiver; At the third time point, an acoustic pulse is received using a third acoustic receiver located at a third radial distance from at least one acoustic transmitter; In response to receiving an acoustic pulse, a third receiver signal is provided from the third acoustic receiver; Determine the first propagation time between receiving a signal from a first receiver and emitting an acoustic pulse from at least one acoustic transmitter; Determine the second propagation time between receiving a signal from the second receiver and emitting an acoustic pulse from at least one acoustic transmitter; Determine the third propagation time between receiving a signal from a third receiver and emitting an acoustic pulse from at least one acoustic transmitter; Construct a propagation function for propagation between at least one acoustic transmitter and at least one of a first acoustic receiver, a second acoustic receiver, or a third acoustic receiver when the aircraft is in flight, wherein the propagation function is constructed by a beamforming algorithm, wherein the propagation function takes into account the influence of the boundary layer of the surface adjacent to the aircraft, and wherein the propagation function is constructed based on at least one of the following: The position of at least one acoustic transmitter relative to at least one of the first receiver, the second receiver, or the third receiver; The amplitude of at least one of the first receiver signal, the second receiver signal, or the third receiver signal; as well as The phase of at least one of the first receiver signal, the second receiver signal, or the third receiver signal; Receive or determine the wind angle; as well as Airspeed is determined based on the propagation function and at least one of the first propagation time, second propagation time, third propagation time, or wind angle, and an airspeed signal indicating the airspeed is output.

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