Sensor System For Determining Air Velocities

Abstract

A sensor system for an aircraft for determining the air velocity of air flowing past the aircraft includes a first sensor and an evaluation device. The first sensor is configured for being arranged at the structure of the aircraft and determines a first response of the structure to a first local pressure fluctuation of a boundary layer of the air flowing past the aircraft. Furthermore, the first sensor generates a first signal on the basis of the determined first response of the structure. The evaluation device is configured for processing said first signal and for determining the actual air velocity on the basis of the first signal.

Claims

1. A sensor system for an aircraft for determining a velocity of air flowing past the aircraft, the sensor system comprising: a first sensor configured for being arranged at a structure of the aircraft; and an evaluation device, wherein the first sensor is configured for determining a first response of the structure to a first local pressure fluctuation of a boundary layer of the air flowing past the aircraft and for generating a first signal on the basis of said determined first response, and wherein the evaluation device is configured for processing the first signal and for determining an actual air velocity on the basis of the first signal.

2. The sensor system according to claim 1, wherein the evaluation device comprises a first database, the first database comprising a plurality of first-type entries corresponding to signals of the first sensor and a plurality of second-type entries corresponding to air velocities, the first-type entries being linked to the second-type entries, and wherein the evaluation device is configured for looking-up the actual air velocity in the database on the basis of the first signal.

3. The sensor system according to claim 2, wherein the first-type entries of the first database correspond to frequency spectra of signals of the first sensor, and wherein the evaluation device is configured for generating a first frequency spectrum of the first signal and for looking-up the actual air velocity in the first database on the basis of the first frequency spectrum.

4. The sensor System according to claim 1, the sensor system comprising: a second sensor configured for being arranged at the structure of the aircraft; wherein the second sensor is configured for determining a second response of the structure to a second local pressure fluctuation of the boundary layer of the air flowing past the aircraft and for generating a second signal on the basis of said determined second response, and wherein the evaluation device is configured for processing the first signal and the second signal and for determining the actual air velocity on the basis of the first signal and the second signal.

5. The sensor system according to claim 4, wherein the evaluation device is configured for determining a correlation function between the first signal and the second signal and for determining the actual air velocity on the basis of the determined correlation function.

6. The sensor system according to claim 5, wherein the evaluation device is configured for determining a velocity of eddies of a boundary layer of the air flowing past the aircraft on the basis of the correlation function; wherein the evaluation device comprises a second database, the second database comprising a plurality of third-type entries corresponding velocities of eddies and a plurality of fourth-type entries corresponding to air velocities, the third-type entries being linked to the fourth-type entries, and wherein the evaluation device is configured for looking-up an air velocity in the database on the basis of the first signal.

7. The sensor system according to claim 4, the sensor system comprising: a third sensor configured for being arranged at a structure of the aircraft; wherein the third sensor is configured for determining a third response of the structure to a third local pressure fluctuation of the boundary layer of the air flowing past the aircraft and for generating a third signal on the basis of said determined third response, and wherein the evaluation device is configured for determining an actual angle of attack of the aircraft by determining a maximum or minimum coherence between the first signal, the second signal and the third signal.

8. The sensor system according to claim 1, wherein each sensor of the sensor system is an accelerometer and/or a strain sensor, respectively.

9. The sensor system according to claim 1, wherein the evaluation device is configured to determine whether the first response, the second response and/or the third response of the structure is generated by a respective local pressure fluctuation of the boundary layer of the air flowing past the aircraft.

10. An aircraft comprising the sensor system comprising: a first sensor configured for being arranged at a structure of the aircraft; and an evaluation device, wherein the first sensor is configured for determining a first response of the structure to a first local pressure fluctuation of a boundary layer of the air flowing past the aircraft and for generating a first signal on the basis of said determined first response, and wherein the evaluation device is configured for processing the first signal and for determining an actual air velocity on the basis of the first signal, the aircraft comprising: the structure of the aircraft; wherein the first sensor is arranged at the structure of the aircraft.

11. The aircraft comprising the sensor system according to claim 10, the sensor system further comprising: a second sensor configured for being arranged at the structure of the aircraft; and a third sensor configured for being arranged at a structure of the aircraft, wherein the second sensor is configured for determining a second response of the structure to a second local pressure fluctuation of the boundary layer of the air flowing past the aircraft and for generating a second signal on the basis of said determined second response, wherein the third sensor is configured for determining a third response of the structure to a third local pressure fluctuation of the boundary layer of the air flowing past the aircraft and for generating a third signal on the basis of said determined third response, and wherein the evaluation device is configured for processing the first signal and the second signal and for determining the actual air velocity on the basis of the first signal and the second signal and for determining an actual angle of attack of the aircraft by determining a maximum or minimum coherence between the first signal, the second signal and the third signal, wherein the second sensor and the third sensor are arranged at the structure of the aircraft.

12. A method of determining an air velocity for an aircraft, the method comprising the steps: determining a first response of a structure of the aircraft; determining the air velocity on the basis of the determined first response.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG. 1A shows a sensor system according to an exemplary embodiment.

[0059] FIG. 1B shows an evaluation device of a sensor system according to an exemplary embodiment.

[0060] FIG. 2 shows an aircraft structure with a sensor system according to an exemplary embodiment.

[0061] FIGS. 3A, 3B, 3C each show an aircraft structure, on which sensors of a sensor system are arranged according to exemplary embodiments.

[0062] FIGS. 4A and 4B show an aircraft structure, on which sensors of a sensor system are arranged according to an exemplary embodiment.

[0063] FIG. 5 shows an aircraft according to an exemplary embodiment.

[0064] FIG. 6 shows a flow-chart according to exemplary embodiments.

[0065] The figures are schematic and are not necessary true to scale. If, in the following description, the same reference signs are used in the context of different figures, they refer to similarly or equivalent elements. Similar or equivalent elements may, however, also be referenced to with different reference signs.

DETAILED DESCRIPTION

[0066] FIG. 1A shows a sensor system 100 comprising a first sensor 101 as well as an evaluation device 102. Furthermore, it is shown that the sensor system 100 comprises a second sensor 103. The sensor system 100 may also comprise only the first sensor 101. The first sensor 101 and the second sensor 103 are configured for being arranged, i.e. attached to or embedded in, a structure of an aircraft, for example a skin segment, a frame, a stringer or another kind of structural part of the aircraft.

[0067] The first sensor 101 is configured for determining a first response of the structure, at which the first sensor is arranged, to a first local pressure fluctuation of a boundary layer of the air flowing past the aircraft. Furthermore, the first sensor is configured for generating a first signal on the basis of the determined first response of the structure. The same also accounts to the second sensor 103 as described.

[0068] The first sensor 101 and the second sensor 103 are each configured for transmitting the first/second signal to the evaluation device 102. For example, the first and second sensors 101, 103 may be connected to the evaluation device 102 by means of wires 107, 108 for transmitting the signals from the sensors 101, 103 to the evaluation device 102. Alternatively or additionally, the first and second sensors 101, 103 as well as the evaluation device 102 may be equipped with antennas 104, 105 and 106 for transmitting signals from the sensors 101, 103 to the evaluation device 102.

[0069] The evaluation device is configured to determine the actual air velocity on the basis of the first signal of the first sensor 101 or on the basis of the first signal of the first sensor 101 and the second signal of the second sensor 103. For example, the evaluation device 102 may comprise a processing unit, that is configured for determining said actual air velocity. Furthermore, the evaluation device may also comprise a storing unit, on which a first database and/or a second database as described.

[0070] FIG. 1B shows an evaluation device 102 of a sensor system according to an exemplary embodiment. The evaluation device comprises a processing unit 109 and a storing unit 110. The processing unit 109 may be configured for carrying out the steps for determining the air velocity described herein. In the storing unit 110, the first and second databases described herein may be stored. It is also shown that the evaluation device 102 comprises an antenna 105 for receiving the signals of the sensors. The evaluation device may, however, alternatively or additionally comprise a wire for receiving said signals.

[0071] FIG. 2 shows a sensor system 100 according to an exemplary embodiment, which sensor system comprises a first sensor 101 and a second sensor 103 that are attached to a structure, e.g. a skin segment, 200 of an aircraft. Although, FIG. 2 shows that the first and second sensors 101 and 103 are attached to the same structure 200, for example the skin segment of the aircraft, it may also be possible that the different sensors (e.g. the first and second sensors 101 and 103) are arranged at different structures. For example, the first sensor 101 may be arranged at a first skin segment and the second sensor 103 may be arranged at a second skin segment.

[0072] In FIG. 2 it is further shown that the air is flowing past the structure 200 along the direction 202. In the boundary layer of the air flowing past the aircraft 202 or flowing past the structure 200 of the aircraft, eddies or vortices 203 are created, that travel along the structure 200 of the aircraft. These eddies or vortices 203 correspond to the local pressure fluctuations described herein. The eddies 203 may cause structural responses, for example an oscillation or vibration, of the structure 200. The responses are detected by the sensors 101 and 103, which are configured to generate a respective first/second signal on the basis of said detected responses. The signals are then transmitted to the evaluation device 102 and the evaluation device 102 is configured to determine the actual air velocity on the basis of the first/second signals transmitted from the first/second sensors 101/103 to the evaluation device 102. Furthermore, the evaluation device may comprise a storing unit on which the distance 201 between the first and second sensors 101 and 103 is stored. The evaluation device may be configured for determine the actual air velocity on the basis of the first/second signals of the first/second sensors 101, 103 and the distance 201.

[0073] FIGS. 3A, 3B and 3C show different arrangements of pairs of sensors of a sensor system described on a structure, for example a skin segment 200, of an aircraft. Although it is shown that the sensors are arranged on the same structure, the different sensors may also be arranged at different structures.

[0074] FIG. 3A shows a pair of sensors 101, 103 that are arranged at a distance 201. The arrow 300 refers to the z-direction or longitudinal direction of the aircraft. Thus, the distance between the two sensors 101 and 103 is along the z-direction 300.

[0075] FIG. 3B shows an arrangement of three pairs of sensors 101 and 103, 301 and 302, 303 and 304 on the structure 200 of the aircraft. All three pairs of sensors 101 and 103, 301 and 302, 303 and 304 are arranged with the same distance 201 in z-direction 300. By having more than two sensors, it is possible to determine an angle of attack of the aircraft. For example, the evaluation device (not shown) can be configured to determine coherences between the sensors attached to the structure 200. For example, if the evaluation device determines that the maximum or minimal coherence is between the sensors 103 and 303, the angle of attack may be derived from the line connecting the sensor 103 and the sensor 303. This is, however, only a simplified example for explaining how the angle of attack can principally be determined.

[0076] FIG. 3C shows an aircraft structure 200 with three pairs of sensors 101 and 103, 301 and 302, and 303 and 304. According to this exemplary embodiment, the distances 201, 305 and 306 between the pairs of sensors 101 and 103, 301 and 302, 303 and 304 along the z-direction 300 are different.

[0077] The accuracy of the results is sensitive to the sensor distances. A short distance will lead to a good signal correlation, but the delay time becomes very short. This short delay time is sensitive to the measurement uncertainty. For a longer distance the coherence between the two signals becomes worse. Depending on the turbulent boundary layer thickness and the air velocity there is an optimal distance between the sensors. During a flight, these parameters are changing such that different distances between the sensors are needed for optimally determining the air velocity. Thus, by providing sensor pairs with different distances along the z-direction, the sensor system may be adapted to precisely determine the air velocity in different flight situations (e.g. at different aircraft velocities).

[0078] FIG. 4A shows a structure 200 of an aircraft, at which sensors 401 to 406 of a sensor system according to an exemplary embodiment are arranged. The arrow 300 refers to the z-direction of the aircraft. According to this exemplary embodiment, the sensor system comprises a first sensor 401 as well as additional sensors 402 to 406, which additional sensors 402 to 406 are arranged on a circular arc. The evaluation device may be configured to determine a correlation between the first sensor 401 and the additional sensors 402 to 406. By determining the additional sensor 402 to 406, which produces together with the first sensor the maximum or minimum coherence, the evaluation device (not shown) can determine the actual angle of attack. For example, the angle of attack may be determined by the line connecting the first sensor 401 and the additional sensors 402 to 406 which yields the maximum or minimum coherence together with the first sensor 401.

[0079] FIG. 4B shows a similar structure 200 of an aircraft, at which sensors 401 to 403 of a sensor system according to an exemplary embodiment are arranged. According to this exemplary embodiment, the sensors 401 to 403 are arranged in a triangular configuration.

[0080] FIG. 5 shows an aircraft 500 according to an exemplary embodiment. The aircraft 500 comprises a sensor system. The sensor system 100 comprises first and second sensors 101 and 103 as well as an evaluation device. Although it is shown that the sensor system 100 comprises two sensors 101 and 103, the sensor system may also comprise only one sensor 101. The first and second sensors 101 and 103 are arranged, for example attached or embedded in, a structure 501 of the aircraft 500, for example a skin segment.

[0081] FIG. 6 shows a flow-chart of a method of determining an air velocity for an aircraft according to exemplary embodiments. The method comprises step S1 of determining a first response of a structure of the aircraft and the step S2 of determining the air velocity on the basis of the determined first response. According to a further exemplary embodiment, the method may comprise the step S1 of determining a first response of a structure of the aircraft, the step S3 of determining a second response of the structure of the aircraft and the step S2 of determining the air velocity on the basis of the determined first and second responses.

[0082] In the claims, the word comprising does not exclude other elements or steps and the indefinite article a or an does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The reference numerals in the claims are not intended to restrict the scope of the claims.

[0083] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.