JP2002071447A - Pulse sound judgment method - Google Patents

Abstract

(57) [Summary] [Problem] Engine, motor, mission, or
Even if a sudden loud sound is included in the pulse sound caused by the rotation axis of a rotating body such as a plant, it can be easily calculated by calculating the number of pulse sounds of the waveform data collected in a certain unit time. The present invention provides a pulse sound determination method capable of accurately determining whether a rotating body is normal or abnormal with a simple method. SOLUTION: This is a pulse sound judging method for judging a normal / abnormal product of a rotating body by using a pulse sound caused by a rotating shaft of the rotating body. This pulse sound determination method calculates the mean square value of the amplitude of the waveform data collected in a certain unit time, then obtains the square root of the mean square value, and calculates the amplitude threshold multiplied by a constant and the amplitude of the original waveform data. In comparison, when the number of the amplitudes of the waveform data exceeding the amplitude threshold exceeds the set number threshold, it is determined that the waveform data includes a periodic pulse sound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a pulse sound, and more particularly to a method for determining a pulse sound caused by a rotating shaft of a rotating body such as an engine, a motor, a mission, or a plant. The present invention relates to a pulse sound determination method for a system for detecting a normal / abnormal state by detecting a characteristic of a pulse sound of waveform data collected in a unit time.

[0002]

2. Description of the Related Art Conventionally, an index called a crest factor (crest factor or impact index) is generally used for detecting a pulse sound or a sound greatly exceeding an average value of a waveform. The crest factor is the ratio of the maximum value (peak value) of the target time waveform to the root-mean-square value (RMS value), and the presence or absence of a pulse and the sharpness of the pulse can be expressed numerically. Therefore, it is used to judge a bearing defect.

[0003]

For example, using the above-mentioned technique to measure an engine sound and detect an abnormality characterized by a pulse sound caused by rotation of a crankshaft as the same rotating body. think of. If there is a pulse sound in the collected sound, the crest factor will be high, so it is expected that the abnormal product will have a high crest factor. However, when a sound having a large amplitude enters unexpectedly, such as when a loud sound suddenly enters the background noise, the crest factor becomes a high value due to the sound. As a result, in the abnormal product judgment method using the crest factor, when suddenly large background noise enters, the background noise cannot be eliminated, and the crest factor increases. There is a problem in that the accuracy of determining an abnormal product is reduced, such as the determination of an abnormal product.

The present invention focuses on the above-mentioned conventional problems and relates to a pulse sound determination method. In particular, the present invention relates to a pulse sound generated due to a rotating shaft of a rotating body such as an engine, a motor, a mission, or a plant. Even if a loud noise is heard, the number of pulse sounds of the waveform data collected in a certain unit time is calculated and obtained, so that a simple method can accurately and accurately determine whether the rotating body is normal or abnormal. It is intended to provide a determination method.

[0005]

Means for Solving the Problems Conventionally, inspection of a rotating body is intended to detect a periodic pulse sound.
If an appropriate time range is set, a plurality of pulse sounds should be included. The present invention has been made by paying attention to this, and proposes a method of detecting a periodic pulse sound by paying attention to the number of waveform data whose amplitude is equal to or larger than a certain amplitude threshold value. The amplitude threshold is a constant multiple of the RMS value, and this constant is determined from normal and abnormal data collected in advance. At this time, the waveform data is A / D-converted in order to capture and store the waveform data in a computer.
Data is discretized by sampling and stored. For example,
When sampling is performed at 20 kHz, waveform data for one second is stored as 20,000 discrete data. The discretized waveform data has an amplitude {xi} =
(X1, x2, x3,..., Xn).

Next, an RMS value (a) is calculated for the waveform data. The RMS value a is calculated by the following equation 1.

[Formula 1]

The RMS value a is compared with an amplitude xi measured using αa using a certain constant α as an amplitude threshold, and the number of amplitudes (in this case, absolute values) exceeding αx _RMs is counted. This count number is used as an index value of each data. The constant α is determined from the crest factor of the abnormal data and the normal data obtained in advance. In order to detect an abnormality, it is necessary to set α to be equal to or less than the crest factor of the abnormal data. Finally, a number threshold is set for the count number obtained for each data, and an individual whose count number exceeds a certain number threshold is determined to be abnormal.

Using the above point of interest, the pulse sound determination method of the present invention calculates the mean square value of the amplitude of waveform data collected in a certain unit time, then calculates the square root of the mean square value and multiplies by a constant. The amplitude threshold value is compared with the amplitude of the original waveform data, and when the number of waveform data amplitudes exceeding the amplitude threshold exceeds a set number threshold, the waveform data includes a periodic pulse sound. Is determined. In the above, when the engine sound includes a pulse sound having a number equal to or larger than the set threshold value, it is preferable that the engine is determined to be rejected.

[0009]

According to the above method, in the case of a sample containing a periodic pulse sound, the crest factor also becomes high, but the number of pulse sounds exceeding the amplitude threshold within the observation time increases in accordance with this. Output values are obtained. On the other hand, in the case of a sample containing a loud sound due to a sudden factor, the crest factor becomes high similarly to the case of a sample containing a periodic pulse sound, but a loud sound is included. Since only a portion contributes to the output, a small output value is obtained with the number of pulse sounds. Therefore, by comparing the number of pulse sounds exceeding the amplitude threshold value within the observation time with the number threshold value, it is possible to determine whether the sample of the rotating body is normal or abnormal. In a rotating body with many types of engines, etc., the engine sounds are collected,
The determination is made in accordance with the crest factor and whether or not the periodic pulse sound is included in the number equal to or more than the number threshold value.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the pulse sound determination method according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an example of an apparatus for performing the pulse sound determination method according to the present invention. FIG. 2 is a flowchart illustrating the pulse sound determination method, and FIG. It is an experimental data figure of an example. FIG. 3A is a data diagram showing an example of a normal state, FIG. 3B is a data diagram showing an example of an abnormal state, and FIG. 3C shows an example of a normal state in which noise is mixed. It is a data diagram.

FIG. 1 shows an example in which the pulse sound judging device 1 is applied to a case where a normal or abnormal engine is detected. In the pulse sound determination device 1, a sound receiving device 12 that collects sounds is arranged near an engine 10 to be inspected. The sound receiving device 12 is configured by a microphone.
The sound (engine sound) generated from 0 is collected, converted into an electric signal corresponding to the magnitude of the engine sound, and input to the signal analyzer 14 via an amplifier (not shown). Sound receiving device 12
Between the control signal input / output device 1 and the signal analyzer 14
6 is arranged, and the control signal input / output device 16 processes the engine sound collected by the sound receiving device 12 in accordance with the control steps (flowchart) of FIG.
4 and to the determination unit 28.

The signal analyzing device 14 comprises a digital filter 20, a computing unit 22, a comparator 24, and a data storage unit 26. The comparator 24 is connected to the determination unit 28, and the sound collected from the engine 10 is calculated by the calculator 22, compared with the predetermined threshold value as described above, and the result is output to the determination unit 28. ing. The determination unit 28 detects the periodically generated pulse sound in the waveform data collected in a certain unit time. Therefore, even when a suddenly large sound is input, the determination unit 28 determines the number of pulse sounds exceeding the amplitude threshold value. By detecting, normal / abnormal product can be determined. This eliminates the need for the conventional sensory test based on the sense of sound of the operator, eliminates the need for a lot of experience to judge the quality of the engine, eliminates the variation in the judgment due to individual differences, and reduces inspection errors. Is also lost.

The digital filter 20 has a configuration in which upper and lower limit frequency setting, attenuation setting, and the number of filter taps can be arbitrarily set. In the present embodiment, as shown in FIG. 3, the digital filter 20 discriminates the waveform data collected in a certain unit time in a time-series manner, as shown in FIG. , {Xi} = (x1, x2, x3,..., Xn) are output to the arithmetic unit 22 and stored in the data storage unit 26. The computing unit 22 receives the amplitude of the waveform data collected in a certain unit time, computes the RMS value a by the above-described formula 1, and outputs the RMS value a to the comparator 24. The comparator 24 calculates the RMS value a received from the arithmetic unit 22.
And the amplitude threshold value αa set in the comparator 24 to detect the number Qn of RMS values a exceeding the amplitude threshold value αa. The detected number Qn is output to the determination unit 28. The determination unit 28 determines the detected number Qn
Is compared with the number threshold value Sa set in the determination unit 28 to output a determination.

The control signal input / output device 16 sequentially outputs control step commands to the signal analyzer 14 in accordance with the flowchart shown in FIG. In step 1, the waveform data collected in a certain unit time is A / D converted, and the discrete amplitude data, {xi} = (x1, x
2, x3,..., Xn), and outputs a command to store the data in the data storage device 26. In step 2,
A command for calculating the square root of the mean square value of the amplitude (RMS value) is output, and the calculation result is output as the RMS value a by the comparator 2
4 is output. In step 3, a command to count the number Qn of data having the amplitude value xi equal to or larger than the constant multiple α of the RMS value a is output to the comparator 24. At this time, the constant α is determined from abnormal data and normal data obtained in advance.

This counting is performed according to a partial flowchart for performing the pulse sound determination method shown in FIG. In step 4, int i = 1; int
count = 0; counting is started. In step 5, the number i of amplitude comparisons reaches n (Fals
e) or not reached (True).
If it has not reached (True) in step 5, go to step 6. In step 6, it is determined whether the absolute value xi of the amplitude, that is, [abs (xi)] is larger (True) or smaller (False) than the amplitude threshold αa. If it is large (True) in step 6, go to step 7. In step 7, count = count
t + 1 is calculated, and the number Qn of absolute values xi [abs (xi)] having an amplitude larger than the amplitude threshold αa is accumulated and counted.

If it is small (False) in step 6,
After the accumulated number Qn is obtained in step 7, the process goes to step 8. In step 8, assuming that i = i + 1,
In step 5, it is determined whether or not the next comparison number i + 1 has reached n (False) or not (True). This is repeated, and if the number i of amplitude comparisons reaches n (False) in step 5, the process returns to the flowchart of FIG.
In step 9, the absolute value xi of the amplitude obtained in step 7
A command is output to determine whether the cumulative number Qn of [abs (xi)] is larger (False) or smaller (True) than the number threshold Sa set in the determination unit 28.

The determination unit 28 determines in step 9 that the value (Fa
1se) determines that the engine 10 to be inspected is abnormal and outputs it.
In e), it is determined that the engine 10 to be inspected is normal and output. The result is displayed on the display 30. Accordingly, the pulse sound determination device 1 detects a periodically generated pulse sound in the waveform data collected in a certain unit time. An abnormal product can be determined.

Next, the experimental results shown in FIG. 3 will be described. In FIG. 3, as waveform data, normal data A in FIG. 3A, abnormal data B in FIG.
(C), mixed data C in which a high amplitude was accidentally mixed as noise due to the influence of a target machine or background noise or the like was obtained. As to the obtained data, the crest factor of the abnormal data B is 2.12 and the crest factor of the mixed data C is 2.60 when only the crest factor is considered as in the related art. . Therefore, if the determination is made based on the crest factor, the mixed data C is more than the crest factor of the abnormal data B.
Since the crest factor is high, the mixed data C must be determined to be abnormal.

Then, using each RMS value a,
When counting the cumulative number Qn of the amplitude threshold value αa or more having the amplitude data of 1.5 times which is the constant multiple α of the RMS value a, the abnormal data B is 6 and the mixed data C is 2 is there. Therefore, for example, if the number threshold of the cumulative number Qn is set to 5 or more, it is determined that the product is abnormal, and the mixed data C can be determined to be normal. In this way, using the RMS value a, a pulse sound that periodically occurs in the waveform data collected in a certain unit time is detected, and the number of the amplitudes xi exceeding the predetermined amplitude threshold αa is counted. If the cumulative number Qn of this number exceeds the set number threshold value Sa, it is determined as an abnormal product,
If it does not exceed it, it is judged as a normal product.
Even when a loud sound suddenly enters, the determination can be made with high accuracy.

In the above-described pulse sound determination method, after calculating the mean square value of the amplitude of the waveform data collected in a certain unit time, the square root of the mean square value is obtained, the amplitude threshold value multiplied by a constant, and the original waveform data And when the number of the amplitudes of the waveform data exceeding the amplitude threshold exceeds the set number threshold, it is determined that the waveform data includes a periodic pulse sound. For this reason, even if a sudden loud sound is included in the pulse sound caused by the rotating shaft of a rotating body such as an engine, a motor, a mission, or a plant, the pulse of the waveform data collected in a certain unit time By calculating and obtaining the number of sounds, it is possible to accurately determine whether the rotating body is normal or abnormal with a simple method.

[0021]

As described above, according to the present invention, in the pulse sound judging method, after the amplitude of the waveform data in a certain unit time is set to the mean square value, the square root of the mean square value is obtained, and the constant is multiplied. The amplitude threshold is compared with the amplitude of the original waveform data, and when the number of amplitudes of the waveform data exceeding the amplitude threshold exceeds the set number threshold, a periodic pulse sound is generated in the waveform data. Is determined to be included. Thereby, even in a situation where it is difficult to detect the crest factor due to the sudden pulse sound included in the background noise or the like, the method of the present invention can obtain an output corresponding to the number of pulses exceeding the threshold value. Thus, a sample including a periodic pulse sound can be detected more easily. This means that the influence of background noise can be further reduced, and it is possible to improve the accuracy of determining whether a sample is normal or abnormal. There are many types like engines, and
When a pass / fail judgment is made in a place where background noise is likely to occur, a particularly high-precision judgment can be made.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of an apparatus that performs a pulse sound determination method according to the present invention.

FIG. 2 is a flowchart illustrating a pulse sound determination method according to the present invention.

FIG. 3 is an experimental data diagram of an example obtained according to a flowchart of a pulse sound determination method according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pulse sound determination device, 10 ... Engine, 12 ... Sound receiving device, 14 ... Signal analysis device, 16 ... Control signal input / output device,
Reference Signs List 20 digital filter, 22 arithmetic unit, 24 comparator, 26 data storage unit, 28 determination unit, 30 display unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G064 AA15 AB02 AB13 CC06 CC26 CC28 CC32 CC35 CC46 CC55 CC57 CC65 2G087 BB04 CC15 EE21 FF04 FF23

Claims (2)

[Claims] After calculating a root-mean-square value of amplitude of waveform data collected in a certain unit time, a square root of the root-mean-square value is calculated, and an amplitude threshold value multiplied by a constant is compared with the amplitude of the original waveform data. And a method for determining that the waveform data includes a periodic pulse sound when the number of amplitudes of the waveform data exceeding the amplitude threshold exceeds a set number threshold. 2. The pulse sound determination method according to claim 1, wherein the device is determined to be rejected when the device sound includes a pulse sound having a number greater than or equal to the set number threshold.