JP2539864B2 - Acoustic abnormality detection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an abnormality detection device for a large-scale device such as a boiler for business use, and more particularly to an acoustic abnormality detection device suitable for accurately detecting a noise generation direction.

[Conventional technology]

In a large-scale device composed of many devices such as a thermal power plant, in order to acoustically detect an abnormality of the device,
Multiple microphones, which are conventional acoustic detectors, are installed around a large device, and the level and frequency spectrum of the signal detected by each microphone is monitored and compared with the signal during normal operation to determine whether it is normal or abnormal. Has been done. Third
FIG. 1 shows a configuration example of a conventional abnormality detection device. Generated from the large device 12 by a plurality of semi-fixed microphones 1 (four A, B, C, D in the figure) having a mechanism such as fixing or swinging around the large device 12 such as a commercial boiler. Detect noise. The detected noise signals are respectively amplified by the amplifier 2 and then guided to the channel selector 3. The frequency spectrum analyzer 4 obtains a cross power spectrum G AB between arbitrary adjacent microphones (for example, AB) selected by the channel selector 3.
here, PA: Signal of microphone A PB: Signal of microphone B RAB: Cross-correlation between PA and PB GAB is a complex number and can be divided into a real number part and an imaginary number part, that is, an amplitude and a phase. FIG. 4 shows an example of the cross power spectrum displayed in amplitude and phase.
The frequency comparator 5 extracts about 10 frequencies showing remarkable peaks in the amplitude characteristic of the cross power spectrum, compares them with a reference frequency registered in advance, and determines whether or not the peak frequency has changed. The phase comparator 6 extracts the phase difference at the peak frequency from the phase characteristics of the cross power spectrum, compares it with the reference phase difference registered in advance, and determines whether or not there is a phase difference change. Normality / abnormality determiner 7
Then, the presence / absence signal of the change from the frequency comparator 5 and the phase comparator 6, and the operation signal 9 of the device a and the operation of the device b corresponding to the ON / OFF signals of the main constituent devices such as the forced draft fan (FDF). The signal 10 and the operation signal 11 of the device c are used to determine whether the large device 12 is normal or abnormal.

[Problems to be solved by the invention]

In such a conventional abnormality detection device, an effective cross power spectrum cannot be obtained unless the microphone interval l is reduced to some extent (especially, the phase detection accuracy decreases), and the number of microphones is very large for application to a large device. There is a drawback that the number of abnormality detection devices increases and the price of the abnormality detection device increases.

Fig. 5 shows an example of the noise power spectrum at the rated load of a thermal power plant. The maximum noise frequency range is 10
It shows that it is necessary to consider up to KHz.
Therefore, in order to obtain effective phase information from the cross power spectrum at this frequency f, It was necessary to set l to 30 mm or less because of the constraint condition that the value be 2π radians or less.

In this way, it is almost impossible to install the microphones at a narrow interval in the case of a large device, and therefore it is very difficult to improve the accuracy of the positive / abnormal determination by using the phase information (especially at a high frequency). It was difficult.

As one of the solutions, a method of mounting the above-mentioned narrowly-spaced microphones on a moving mechanism (for example, a support frame moving on a rail by a motor drive) and detecting an abnormality while moving around a large device is considered. However, it takes about one minute or more to move around the boiler with a moving mechanism (normal moving speed is, for example, 1 m / sec. If it is included, it takes 5 minutes or more), but it is difficult to make a positive / abnormal judgment, and there is a drawback that the judgment cycle becomes long.

[Means for solving problems]

The present invention has been made to solve the above problems, and is attached to a device to be inspected that is inspected for abnormality.
An acoustic anomaly detection device that detects a cross power spectrum from the detection signals of individual acoustic detectors and detects the presence or absence of anomalies based on the intensity and direction of the sound. And at least one movable acoustic detector that cyclically approaches the fixed acoustic detector, and a power spectrum between the detection signals of the fixed acoustic detection and the moving acoustic detector is calculated and compared with a normal value. And an apparatus for detecting the presence / absence of an abnormality, the acoustic abnormality detecting apparatus being provided.

〔Example〕

FIG. 1 shows the overall configuration of an acoustic abnormality detection device according to the present invention. The fixed microphones 1 are fixedly installed around a large inspected device 12 such as a boiler at intervals of 5 to 10 m (not necessarily even intervals). On the other hand, a movable microphone that moves along a moving rail 14 attached around the large device under test 12.
Provide M13. The signals received by the fixed microphone 1 and the movable microphone M13 are amplified by the amplifier 2, and then the signal from the fixed microphone 1 is guided to the channel selector 3. The frequency spectrum analyzer 4 compares the signal arbitrarily selected by the channel selector 3 (for example, the signal from the fixed microphone A) and the signal from the movable microphone M13.
(For example, a high-speed Fourier transformer: FFT) to derive a cross power spectrum GAM between two signals. The cross power spectrum GAM is a complex number, and the two terms of the real number part and the imaginary number part or the amplitude and the phase are calculated (the latter case is shown in FIG. 4). For example, the amplitude of the cross power spectrum GAM is a signal corresponding to the magnitude of the correlation between the signals of the microphone A and the microphone M, and the greater the amplitude, the greater the correlation. On the other hand, the phase of the cross power spectrum GAM is a signal corresponding to the phase difference between the signals of the microphones A and M, the positive phase difference represents the phase advance of the microphone A signal, and the negative phase difference represents the phase lag of the microphone A signal.

The frequency comparator 5 selects, from the amplitude signal of the cross power spectrum GAM calculated by the frequency spectrum analyzer 4, a signal showing a peak, for example, 10 signals which are at least twice as large as the average amplitude in each frequency band, in descending order, and select them. The peak frequency fpn and the peak amplitude Vpn are obtained.

The phase comparator 6 finds the phase difference θpn at the peak frequency fpn found by the frequency comparator 5. These peak frequency fpn, peak amplitude Vpn, and phase difference θpn signals are normal.
Guided by abnormal unit 7, movable microphone drive controller
The reference value of the relevant condition is selected from the reference values tabulated by the position signal from 15, the blower operation signal 9, the fuel pump operation signal 10, the turbine operation signal 11, etc., and fpn,
Each of Vpn and θpn is compared with a reference value, and if there is a change within a permissible range, an output signal 8 for judging an abnormality is transmitted.

The movable microphone M13 is moved by the movable microphone drive controller 15, and the fixed microphone 1
And the movable microphone M13 is moved so that the distance l between the wave receiving surfaces is 50 mm or less (see FIG. 2). The procedure for moving the movable microphone is, for example, in FIG. 1, moving to the microphone A position for determination, then moving to the microphone B position for determination, moving to the microphone C position for determination, moving to the microphone D position for determination, and thereafter. It returns to the C, B, and A positions.

Since this acoustic anomaly detection device can accurately detect the amplitude and phase of the cross power spectrum up to a high frequency range at each fixed microphone 1 position, the frequency fpn to be noticed in noise and the phase difference at fpn are detected. The calculation of the acoustic direction can be performed relatively easily. Therefore, for example, when the movable microphone M is located at the fixed microphone A position, GBM, G in addition to the cross power spectrum GAM.
It is possible to obtain each cross power spectrum of CM and GDM, and use the amplitude at the frequency of interest fpn (the accuracy with respect to the amplitude value is quite good even if the microphone interval is large) as a signal for positive / abnormal judgment. It is possible to determine the correctness / abnormality of the entire large device at each measurement point, and the determination of correctness / abnormality is quicker than the case of moving a pair of microphones arranged at narrow intervals.

Further, the number of microphones can be reduced and the signal processing system can be simplified as compared with the case where a plurality of pairs of closely spaced microphones are fixedly installed, and this effect becomes more remarkable as the size of a large device increases.

In the embodiment of the present invention, a plurality of microphones fixedly arranged at a long distance are used as a pair (2) required for sound direction measurement.
One of the microphones, and the movable microphone constitutes the other microphone. Only the low frequency range (eg 10Hz order) noise phase can be measured between microphones that are fixedly arranged at a long distance, but the distance between the movable microphone and the fixed microphone is several cm (for example, 5 cm) depending on the installation method and moving mechanism. Since it can be shortened to up to 6KHz, if you reduce the accuracy by several tens of percent, it will be approx.
Phase detection is possible up to noise of 10 KHz, and acoustic direction can be identified.

〔The invention's effect〕

According to the present invention, the number of microphones for acoustic detection is set to two.
It is possible to improve the accuracy of sound positive / abnormal determination at each measurement point of a large device without increasing the number of times (therefore, the number of amplifiers etc. is also doubled). Since it is possible to judge whether the whole is correct or abnormal, the judgment can be speeded up.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of an acoustic abnormality detecting device according to the present invention, FIG. 2 is a diagram showing an example of a method of installing a fixed microphone and a movable microphone, and FIG. 3 is a conventional acoustic abnormality. FIG. 4 is a configuration diagram of the detection device, FIG. 4 is an explanatory diagram of a cross power spectrum between two microphones of noise collected in the thermal power plant, and FIG. 5 is a frequency distribution diagram of noise in the thermal power plant. 1 ... Fixed microphone, 2 ... Amplifier, 3 ... Channel selector, 4 ... Frequency spectrum analyzer, 5 ...
Frequency comparator, 6 ... Phase comparator, 7 ... Normality / abnormality determiner, 8 ... Output signal, 9 ... Blower operation signal, 10 ...
Fuel pump operating signal, 11 …… Turbine operating signal, 12 ……
Device to be inspected, 13 ... movable microphone, 14 ... moving rail, 15 ... movable microphone drive controller.

Claims (1)

(57) [Claims] 1. An acoustic abnormality detection for detecting the presence / absence of abnormality based on the intensity and direction of the sound by obtaining a cross power spectrum from the detection signals of two acoustic detectors attached to an inspected device to be inspected for abnormality. In the apparatus, acoustic detectors fixedly installed at a plurality of locations of the device to be inspected, at least one movable acoustic detector cyclically approaching the fixed acoustic detectors, and fixed acoustic detection And a device for detecting the presence or absence of abnormality by calculating a power spectrum between the detection signals of the detector and the moving acoustic detector and comparing the power spectrum with a value in a normal state.