JP3042833B2 - BVI noise detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION BVI (BladeVortex) generated when a rotor blade of a helicopter rotates.
Interaction (Blade Vortex Interference) BVI to detect noise
The present invention relates to a noise detection device.

[0002]

2. Description of the Related Art Helicopter noise is mainly caused by rotation of a rotor. BVI noise is also due to the rotor and is generated when a trailing blade crosses an air vortex caused by a leading blade. When this BVI noise is generated, it becomes a loud noise that surpasses other types of noise, and is particularly a problem among helicopter noises.

FIG. 10 (a) is a graph showing a noise waveform when there is no BVI noise, and FIG. 10 (b) is a graph showing a noise waveform when there is BVI noise. The horizontal axis of the graph is time, which is standardized by the rotor rotation cycle.
The vertical axis is the sound pressure of noise (unit is dyn / cm ² ). Since a helicopter having four blades is used here, a similar waveform is generated during one rotation of the rotor blade.
Repeated times.

As shown in FIG. 10 (b), when BVI noise is generated, a large spike-shaped pressure change specific to BVI noise occurs, and the large spike-shaped pressure change is also reduced to 4%.
Appears twice. Each of the four pressure changes is rapid. On the other hand, as shown in FIG. 10A, when no BVI noise occurs, no such change is observed.

FIG. 11 is a graph showing a position where BVI noise is generated on the rotor rotation surface. This graph is expressed in polar coordinates, with the circumferential direction indicating the rotor rotation angle and the radial direction indicating the distance from the rotor rotation axis on the blade. The rotor rotation angle is set to 0 degree behind the rotor rotation axis of the line of symmetry that divides the body of the helicopter into right and left. An angle of 0 to 360 degrees counterclockwise from this is defined as the rotor rotation angle.

The BVI noise has a rotor rotation angle of 3
It frequently occurs in the range of 0 to 60 degrees and 300 to 330 degrees behind port. Among them, particularly, it occurs frequently in a region of 30 to 60 degrees on the starboard side of the helicopter.

[0007] Helicopter flights include level flight, ascending flight, and descent flight.
I noise is likely to occur. That is, when the succeeding blade crosses the lower part of the vortex caused by the preceding blade, BVI noise is likely to occur. Helicopter airspeed 40-120
When descending at kt and a descending speed of 300 to 1200 ft / min, loud BVI noise is generated. Above all, when the helicopter descends at an airspeed of 60 to 80 kt and a descending speed of 500 to 700 ft / min, particularly large BVI noise is generated. It is desirable to avoid this area to reduce helicopter noise.

[0008]

In the helicopter, B
Since there is a lot of noise other than the VI noise, it is difficult for the pilot to recognize the BVI noise with his own ear and steer so that the BVI noise is not generated.

[0009] The area in which a large BVI noise is generated when the helicopter flies down depends greatly on the atmospheric conditions, the weight of the helicopter, and the like. It is impossible for the pilot to grasp all these conditions and fly down while avoiding the area where loud BVI noise occurs.

An object of the present invention is to provide a BVI noise detecting device capable of reliably detecting the occurrence of BVI noise.

[0011]

[0012]

SUMMARY OF THE INVENTION The present invention provides a pressure detecting means which is attached to a rotor blade of a rotary wing machine, detects a pressure change on the blade surface, and converts the pressure change into an electric signal. A BVI noise detection device comprising: a determination unit that searches for a peak value from a signal waveform and compares the peak value with a predetermined threshold to determine the presence or absence of BVI noise. According to the present invention, the presence or absence of BVI noise is determined by comparing a peak value with a predetermined threshold based on an electric signal obtained by detecting a pressure change on a rotor blade surface of a rotary wing machine, BVI noise can be accurately detected.

Further, the present invention is characterized in that the pressure detecting means detects a pressure of air entering through a through hole provided on a surface of the rotor blade. The present invention also provides
A differential circuit for differentiating a signal from the pressure detecting means is provided. According to the present invention, since the signal of the pressure change shows a relatively slow change in the rotor rotation cycle, the amount of change in the pressure can be clarified by passing through the differentiation circuit, and the S / N ratio is improved. be able to.
Further, the present invention is characterized in that a preamplifier for amplifying a signal from the pressure detecting means to the determining means is arranged on a rotating shaft of a rotor. Also, in the present invention, the filter interposed between the pressure detecting means and the judging means may be set to 200 Hz to 1 Hz.
It is characterized by passing a signal of a frequency included in the range of 000 Hz.

Further, the present invention further comprises a rotor rotation angle detecting means for detecting a rotor rotation angle of the rotary wing machine, wherein the judging means comprises a pressure peak value and a predetermined threshold value within a specific rotor rotation angle range. BVI by comparing
It is characterized by determining noise. According to the invention, B
B in a specific rotor rotation angle range characteristic of VI noise
Since the determination of the VI noise is performed, the BVI noise can be accurately detected.

[0015]

FIG. 1 is a diagram showing a configuration of a BVI noise detection device according to a first embodiment of the present invention. The microphone 11 is mounted, for example, on the starboard side of the helicopter. The reason why the mounting position is set to the starboard side is that it is known that a large amount of BVI noise is generated particularly in the region of the rotor rotation angle of 30 to 60 ° in FIG. 11 and that the BVI noise is accurately detected. Embodiments of the invention are not limited to this.

The microphone 11 converts noise generated from the rotor blade of the helicopter into an electric signal. The signal obtained by the microphone 11 is amplified by the preamplifier 12 and sent to the filter 13.

A low-pass filter for removing a signal having a frequency equal to or higher than a predetermined frequency from the signal;
Or, conversely, a high-pass filter that removes a signal having a frequency equal to or lower than a predetermined frequency from a signal, or a frequency included in a frequency band having predetermined upper and lower limits from a signal by combining these two functions. It functions as a band-pass filter that extracts only the signal having the signal. The frequency band of the filter 13 can be arbitrarily set as a frequency characteristic for each helicopter.

The signal passing through the filter 13 is A / D
The signal is sampled by an (analog / digital) conversion circuit 14, converted into a digital signal, and taken into an arithmetic unit 15 such as a computer. The arithmetic unit 15 performs threshold processing for searching for a peak value of a signal waveform and frequency processing for performing FFT (Fast Fourier Transform) to analyze frequency components.

FIG. 2A is a graph showing an output signal of the microphone 11, and FIG. 2B is a graph showing a signal passed through the filter 13. The horizontal axis of this graph is time, which is standardized by the rotation cycle of the rotor. The vertical axis is the sound pressure of the noise (unit: Pa). Since this graph is for a four blade helicopter, a similar waveform is repeated four times. The signal shown in FIG. 2A includes various frequency components from a low frequency to a high frequency having a maximum cycle of 0.25.
The signal shown in (b) includes only frequency components distributed in a frequency band characteristic of BVI noise, for example, in the range of 200 Hz to 1000 Hz.

FIG. 2C is a graph showing a signal waveform when BVI noise is generated, and FIG. 2D is a graph showing BVI noise.
5 is a graph showing a signal waveform when no noise is generated. The horizontal axis of this graph is time, which is standardized by the rotor rotation cycle. The vertical axis is the sound pressure. The calculation unit 15
The peak value is directly searched from the signal waveforms of FIGS. 2C and 2D, and the peak value is compared with the threshold value T1. From FIG. 2C, a peak value M1 is found, and since the peak value M1 is larger than the threshold value T1, the calculation unit 15 determines that "BVI noise is present". The peak value M2 is found from FIG. 2D, and since the peak value M2 is smaller than the threshold value T1, the calculation unit 15 determines that "no BVI noise".

FIG. 2E is a graph showing the result of the FFT processing performed by the arithmetic unit 15. The horizontal axis of this graph is frequency, and the vertical axis is sound pressure. The calculation unit 15 performs an FFT on the signal waveform to obtain a frequency distribution of sound pressure, extracts only a frequency component of the window region W1 characteristic of BVI noise, searches for a peak value, and searches for a peak value M3 and a predetermined value. Compare with threshold value T2. From FIG. 2E, a peak value M3 is found, and since this peak value M3 is larger than the predetermined threshold value T2, it is determined that "BVI noise is present".

When the FFT processing is performed, the filter 13 may function only as a low-pass filter.

The judgment signal obtained as described above is transmitted to the alarm 1
6 to alert the pilot to encourage the pilot to avoid BVI noise. Further, it is also possible to send this determination signal to the flight control computer 17 of the helicopter to perform an autopilot operation to avoid BVI noise.

FIG. 3 shows a second embodiment B of the present invention.
It is a figure showing composition of a VI noise detection device. The microphone 11 is attached to the body of the helicopter as in FIG. 1, and the rotor rotation angle detector 21 is attached so as to contact the rotor rotation axis.

The signal obtained from the microphone 11 is
The signal is amplified by the preamplifier 12. The amplified signal is extracted by the filter 13 only in a predetermined frequency band.
The signal that has passed through the filter 13 is sampled by an A / D conversion circuit 14 and converted into a digital signal.

The signal obtained from the rotor rotation angle detector 21 is also sampled by the A / D conversion circuit 14 and converted into a digital signal. The arithmetic unit 15 obtains a rotor rotation angle distribution of sound pressure from these converted digital signals. Further, the calculation unit 15 searches for a peak value from this distribution to determine the presence or absence of BVI noise.

FIG. 4A is a graph showing a signal waveform when no BVI noise is generated, and FIG. 4B is a graph showing a signal waveform when a noise different from the BVI noise is generated. FIG. 4C is a graph showing a signal waveform when BVI noise occurs. The horizontal axis of this graph is the rotor rotation angle, and the vertical axis is the sound pressure.

The arithmetic unit 15 searches for a peak value from the signal waveform, and compares the peak value with a predetermined threshold. Also,
It is checked whether the peak value is included in the predetermined window area W2. The window area W2 is, for example, as shown in FIG.
The rotation angle is 30 to 60 degrees as shown in FIG.

From FIG. 4A, a peak value M4 is found, and since this peak value M4 is smaller than a predetermined threshold T2, it is determined that "no BVI noise". In FIG. 4B, since no peak value can be found in the window area W2, it is determined that "no BVI noise". In this case, since the peak value M5 exists outside the window area W2, it is considered that a large noise different from the BVI noise is generated. The peak value M5 obtained from FIG.
Since the peak value M5 is larger than 2 and the peak value M5 is included in the window area W2, it is determined that "BVI noise is present".

The determination signal of the arithmetic unit 15 may be sent to the alarm 16 or to the flight control computer 17.

As described above, by determining the occurrence of BVI noise in the region of the rotor rotation angle characteristic of BVI noise, a more reliable determination can be obtained.

FIG. 5 shows a BV according to a third embodiment of the present invention.
It is a figure showing composition of an I noise detection device. As shown in FIG. 3, the microphone 11 is attached to the body, and the rotor rotation angle detector 21 is attached to contact the rotor rotation axis.

The signal obtained by the microphone 11 is amplified by the preamplifier, and the low-pass filter 3
1 and the high-pass filter 32, only a signal in a predetermined frequency band is extracted.
The signal is sampled by the / D conversion circuit 14, converted into a digital signal, and the arithmetic unit 15 searches for the peak value, compares the peak value with the threshold value, and determines the presence or absence of BVI noise, as in the first embodiment. .

The signal obtained by the microphone 11 and amplified by the preamplifier 12 passes only through the low-pass filter 31 of the filter 13, and is supplied to another A / D conversion circuit 11
4 The signals obtained by the rotor rotation angle detector 21 are also sent to the A / D conversion circuit 114, and these signals are respectively sampled and converted into digital signals.
From the converted digital signal, another arithmetic unit 115
Similarly to the embodiment, a rotor rotation angle distribution of a signal is created, a peak value is searched, and the peak value is compared with a threshold value to determine the presence or absence of BVI noise.

The respective operation results obtained from the operation units 15 and 115 are sent to the AND circuit 41.
In the logical product circuit 41, the logical product of the two operation results is BVI
Output as a noise determination signal. By obtaining the logical product of the two operation results in this manner, the BVI
Noise can be detected.

The determination signal of the arithmetic unit 15 may be sent to the alarm 16 or to the flight control computer 17.

FIGS. 6 and 7 are views showing the configuration of a BVI detecting device according to a fourth embodiment of the present invention. FIG. 6A shows the mounting positions of a pressure sensor, a preamplifier and a slip ring. FIG. 6B is a cross-sectional view of the rotor blade as viewed from a section line AA, and FIG. 6C is a partially enlarged view thereof.

As shown in FIG. 6 (a), the distance L2 from the rotation axis of the rotor blade to the mounting position of the pressure sensor 54 is determined by L2 based on the length L1 of the rotor blade.
/ L1 = about 0.6 or more. However, since the optimum pressure sensor mounting position changes depending on the shape and size of the blade, the numerical value is not strictly defined. The preamplifier 12 is attached to the rotation axis of the rotor as close as possible to the pressure sensor 54 and less affected by centrifugal force.
The signal S / N ratio is ensured. The slip ring 51 is attached to the rotor rotation shaft, and takes in the signal of the rotating preamplifier 12 to the inside of the machine.

As shown in FIG. 6B, the cross section of the rotor blade has a front part 5 made of a spar (Spar).
2 and a rear portion 53 made of a honeycomb core are covered with an outer skin 50, and an erosion protector 56 is further provided at a front end portion.
Is formed. The mounting position of the pressure sensor 54 is selected as far forward as possible, excluding the area where the erosion protector 56 is provided, in the cross section of the rotor blade. In addition, you may attach to either the upper and lower surfaces.

As shown in FIG. 6C, the pressure sensor 54
A through-hole is provided on the blade surface at the mounting position. By measuring the pressure of the air entering through the through hole, the pressure on the blade surface is detected. The pressure sensor 54 includes a diaphragm and a piezo element. The diaphragm deforms in response to a change in pressure, and the piezo element converts the deformation displacement of the diaphragm into an electric signal.

FIG. 7 is a block diagram showing an electrical configuration of the fourth embodiment of the present invention. The pressure sensor 54 converts a pressure change on the blade surface into an electric signal. The signal obtained by the pressure sensor 54 is amplified by the preamplifier 12.
The amplified signal is transmitted from the rotor rotating by the slip ring 51 to the non-rotating helicopter main body, sent to the differentiating circuit 55, and differentiated.

The differentiated signal is converted into a digital signal by the A / D conversion circuit 14 and sent to the arithmetic unit 15. The calculation unit 15 searches for the peak value of the signal waveform obtained by taking the absolute value of the signal, and compares the peak value with a predetermined threshold. Based on the comparison result, the presence / absence of BVI noise is determined from the magnitude relationship between the peak value and the threshold value, as in the first embodiment.

FIG. 8A is a graph showing a signal waveform obtained by the pressure sensor 54, and FIG.
5 is a graph showing a signal waveform obtained in FIG. The horizontal axis of this graph is the rotor rotation angle, and the vertical axis is the pressure (FIG. 8).
(A)) or time derivative of pressure (FIG. 8 (b)).
The graph is for a trailing blade crossing a vortex created by a leading blade. The pressure at the moment of crossing will drop slightly from atmospheric pressure. The dashed line in FIG.
The following signals are folded at 0.

As described above, the S / N ratio can be improved by differentiating the weak signal from the pressure sensor 54 with the differentiating circuit 55.

It should be noted that the judgment signal of the operation unit 15 is
May be sent to the flight control computer 17.

FIG. 9 is a block diagram showing an electrical configuration of a BVI noise detection device according to a fifth embodiment. Pressure sensor 54, preamplifier 12, and slip ring 51
Is mounted at the same position as in FIG. 6, and the rotor rotation angle detector 21 is mounted at the same position as in FIG.

The pressure sensor 54 converts a pressure change on the blade surface into an electric signal. The converted signal is amplified by the preamplifier 12, transmitted from the rotor to the helicopter main body by the slip ring 51, sent to the differentiation circuit 55, and differentiated. The signal obtained by the differentiating circuit 14 is converted into a digital signal by the A / D conversion circuit 14 and sent to the arithmetic unit 15.

The rotor rotation angle detector 21 converts the rotor rotation angle into an electric signal. The signal obtained by the rotor rotation angle detector 21 is also converted into a digital signal by the A / D conversion circuit 14 and sent to the arithmetic unit 15.

Based on these digital signals, the calculation unit 15 obtains a rotor rotation angle distribution of pressure. As in the second embodiment, a peak value is searched from the rotor rotation angle distribution of this pressure, the peak value is compared with a threshold value, and the peak value is included in a region of the rotor rotation angle characteristic of BVI noise. Then, the presence or absence of BVI noise is determined.

The determination signal of the arithmetic unit 15 may be sent to the alarm 16 or to the flight control computer 17.

Although not shown, a configuration in which a logical product is obtained from two operation results by combining FIGS. 7 and 9 is also possible, as in the configuration in FIG. 5 which is a configuration in which FIGS. 1 and 3 are combined. It is.

According to the above embodiment, a determination signal indicating the presence or absence of BVI noise is obtained, and BVI noise can be detected with high accuracy.

[0053]

According to the present invention, the presence or absence of BVI noise is determined by comparing a peak value with a predetermined threshold value based on an electric signal obtained by converting a pressure change.
VI noise can be accurately detected.

Further, according to the present invention, the presence or absence of BVI noise is determined in a specific rotor rotation angle range characteristic of BVI noise, so that BVI noise can be detected with higher accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a BVI device detection device according to a first embodiment of the present invention.

FIG. 2A is a signal waveform of a microphone 11,
FIG. 2B shows a signal waveform after passing through the filter 13.
(C) is a signal waveform when BVI noise occurs, and FIG.
(D) is a signal waveform when no BVI noise is generated, FIG.
(E) is a graph each showing the signal waveform obtained by FFT.

FIG. 3 is a diagram showing a configuration of a second embodiment of the present invention.

4 (a) shows a case where BVI noise is not generated, FIG. 4 (b) shows a case where noise different from BVI noise is generated, and FIG. 4 (c) shows a case where BVI noise is generated. 7 is a graph showing each signal waveform when the signal is present.

FIG. 5 is a diagram showing a configuration of a third embodiment of the present invention.

6 (a) shows a mounting position of a pressure sensor, and FIG. 9 (b) is a cross-sectional view taken along line AA of a rotor blade in a fourth embodiment of the present invention. , FIG. 9
(C) is a partially enlarged view thereof.

FIG. 7 is a block diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 8A is a graph showing a signal waveform obtained by a pressure sensor, and FIG. 8B is a graph showing a signal waveform obtained by a differentiating circuit.

FIG. 9 is a block diagram showing a configuration of a fifth embodiment of the present invention.

FIG. 10A is a graph showing a noise waveform when BVI noise is not generated, and FIG. 10B is a graph showing a noise waveform when BVI noise is generated.

FIG. 11 is a graph showing a position where BVI noise is generated on a rotor rotation surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Microphone 12 Preamplifier 13 Filter 14 A / D conversion circuit 15 Operation part 16 Alarm 17 Flight control computer

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Claims (6)

(57) [Claims] 1. A pressure detector attached to a rotor blade of a rotary wing machine, for detecting a pressure change on a blade surface and converting the pressure into an electric signal, and searching for a peak value from a signal waveform obtained by the pressure detector. A BVI noise detection device, comprising: a determination unit that determines the presence or absence of BVI noise by comparing a peak value with a predetermined threshold value. 2. The BVI according to claim 1, wherein said pressure detecting means detects a pressure of air entering the inside through a through hole provided in a rotor blade outer skin.
Noise detection device. 3. A BV according to claim 1, further comprising a differentiating circuit for differentiating a signal from said pressure detecting means.
I noise detector. 4. The BVI noise detecting device according to claim 1, wherein a preamplifier for amplifying a signal from said pressure detecting means to said judging means is arranged on a rotating shaft of a rotor. 5. The BVI noise detecting device according to claim 1, wherein a filter interposed between said pressure detecting means and said judging means passes a signal having a frequency within a range of 200 Hz to 1000 Hz. 6. A rotor rotation angle detecting means for detecting a rotor rotation angle of the rotary wing machine, wherein the determination means compares a pressure peak value with a predetermined threshold value in a specific rotor rotation angle range. By B
The B noise according to claim 1, wherein VI noise is determined.
VI noise detector.