JP4003580B2 - Vibration wave determination device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vibration wave determination device that determines a state of an object, for example, a fitting state, based on a vibration wave generated during the operation of the object such as an assembly operation.
[0002]
[Prior art]
Conventionally, for example, in Embodiment 3 of Japanese Patent Laid-Open No. 10-300730, a target is tapped with a hammer or the like, and the sound or vibration generated at that time is frequency-separated by a wavelet transform computing means, and the time for each frequency band is determined. A technique is described in which a series signal is formed, and based on the determination of the time series signal, the contents of the object are discriminated and the structure is inspected for cracks. In this specification, sound and vibration are collectively referred to as vibration waves.
[0003]
[Problems to be solved by the invention]
By the way, in the above publication, one wavelet transformation calculation means is used. In general, when determining the state of an object based on a vibration wave generated from the object, continuous wavelet transform calculation means is required to capture the vibration wave with high accuracy. However, in this case, a very long calculation time is required, and high performance is also required for calculation hardware. On the other hand, if a discrete wavelet transform computing means with a high computing speed is used, it becomes information about the frequency band of 1/2 factorial, and the state of the vibration wave in the intermediate frequency band between the selected frequency bands is unknown. The determination accuracy may be reduced.
[0004]
The present invention has been made in view of the above points, and by combining the discrete wavelet transformation calculation means and the continuous wavelet transformation calculation means, it is possible to achieve both high speed judgment processing and improvement in judgment accuracy. An object of the present invention is to provide a vibration wave determination device capable of performing the above-described operation.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the technical means according to claims 1 to 5 are employed.
According to the first aspect of the present invention, the vibration wave input means for detecting and inputting the vibration wave generated when the object is operated, the storage means for storing the input vibration wave as detection information in time series, and the detection information as the frequency Discrete wavelet transform calculation means for separating and forming a first time-series signal for each predetermined frequency band, and a target operation sound indicating at least a predetermined operation state of an object is generated based on the first time-series signal An area specifying means for specifying a time series range, and a continuous wavelet transform calculating means for extracting the detection information within the time series range specified by the area specifying means from the detection information and continuously separating the frequency, And a determination means for determining the state of the object based on the second time-series signal frequency-separated by the continuous wavelet transform calculation means and the second threshold value.
[0006]
As a result, the time series range (that is, the generation period) of the vibration wave necessary for determining the state of the object using the discrete wavelet transform computing means can be specified in advance, and the calculation by the continuous wavelet transform computing means for detailed analysis. Since the range can be narrowed down, calculation time can be reduced. As a result, it is possible to achieve both speeding up of the determination process and improvement of the determination accuracy.
[0007]
According to the second aspect of the present invention, the region specifying unit generates a time series in which the target operation sound is generated based on the specific time series signal in the predetermined frequency band in the first time series signal and the first threshold value. By specifying the range, it is possible to specify the time-series range on the assumption of the area to be specified and the sound pressure level in advance, and it is possible to extract the time-series range efficiently and more accurately.
[0008]
According to the third aspect of the present invention, the region specifying means includes a first corrector that corrects the level of the first time-series signal for each predetermined frequency band, and the first corrector. A time series in which a target operation sound is generated based on a first parameter table that gives a set first correction amount, a time series signal obtained by correcting the first time series signal with a first correction amount, and a first threshold value. In addition to the effect of the second aspect, the determination process can be speeded up by including the first determination unit that specifies the range.
[0009]
According to the fourth aspect of the invention, the first determiner determines the state of the object by specifying the frequency band in which the target operating sound is generated in addition to the time-series range in which the target operating sound is generated. This area can be further narrowed down to reduce the subsequent calculation time and the burden of determination processing.
[0010]
According to the fifth aspect of the present invention, the determination means includes a second corrector that corrects the level of the second time-series signal for each frequency band, and a preset second value for the second corrector. A second parameter table that gives a correction amount of 2, a second time-series signal obtained by correcting the second time-series signal with the second correction amount, and a second threshold value for determining the state of the object By having the determination device, it is possible to speed up the determination processing.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0012]
In the following description, an example will be described in which a product assembly (fitting) failure is determined by detecting an assembly sound (fitting sound) generated during assembly of the product as an object. However, the vibration wave determination apparatus 100 of the present invention is not limited to this application, and can be applied to other applications. It can also be applied to detection of vibration instead of sound.
[0013]
FIG. 1 shows a system configuration in an embodiment of the present invention.
[0014]
Here, as an object 1, in this example, as an example of the automatic assembly of resin products, particularly an example in which a loud sound is generated during assembly, a snap fit mechanism as shown in FIG. An example of sound generation from a work process in which the fitting protrusion 104 of the resin component 103 is fitted in the hole portion 102 and the both resin components 101 and 103 are assembled is given. 4A and 4B are examples of vibration waves generated at the time of assembly, and show that the sound pressure level of the fitting sound changes according to the quality of the assembly. As a feature of sound generation at the time of assembly, a mechanical operation sound accompanying the movement of the assembly equipment and a fitting sound that conveys the fitting status (that is, a target operation sound to be judged) are generated. It has a sound pressure level corresponding to the magnitude of the assembly speed and the like, and the sound pressure levels of both sounds change in correlation with each other.
[0015]
The microphone 2 detects the vibration generated in the object 1 for vibration wave determination as a sound wave and converts it into an electric signal. The sound pressure electrical signal input from the microphone 2 is input to the amplifier 3 of the vibration wave determination device 100 and output to the A / D converter 4. The A / D converter 4 converts the sound pressure signal into a digital signal, which is output to the storage device 5 at the subsequent stage for storage processing. The storage device 5 stores digital sound pressure signals sequentially output from the A / D converter 4 in time series, and specifies the generation time, generation timing, or generation period as a time series range later. By making it possible, the sound pressure signal at that time can be taken out and stored in a format in which the signal level can be understood. As the storage format, there can be various formats such as storing time information and sound pressure signal information as a pair, or storing the time information so that the time series relationship can be understood according to the memory location and order of storage.
[0016]
A discrete wavelet transform (hereinafter referred to as DWT) computing unit 6 takes in a digital sound pressure signal stored in the storage device 5 at a predetermined timing, and uses this sound pressure signal as a preset frequency. Each band is separated and converted to the first time-series signal S1. For example, when the sampling frequency of the sound pressure signal is 44 kHz, the time for each frequency band of 1/2 factorial increments such as 1/2 (22 KHz), 1/4 (11 KHz), and 1/8 (5.5 KHz). It will be converted into a series signal. In general, a wavelet transform computing unit is a computing unit that separates sound pressure signals into time-series signals of each frequency by expanding or reducing a basis function (wavelet function). In this example, a frequency band is set in accordance with a fitting sound that is a target operation sound generated from one or more snap-fit mechanisms as at least an assembly sound. This frequency band is composed of a set band of one or a plurality of frequency bands according to the characteristics of the target fitting sound.
[0017]
The first corrector 7 constitutes a part of the region specifying means, and usually includes one or more correctors 7a, 7b,... That receive the first time-series signal S1 for each predetermined frequency band. It is an aggregate. Each of the correctors 7a, 7b... Has a gain G1 (G11, G12,...) That is a correction amount (or correction coefficient) set for each predetermined frequency band from a first parameter table 8 described later. In response, the first time-series signal S1 is weighted for each frequency band. This is because the time-series signal in the frequency band other than the assumed fitting sound is regarded as noise and the level is lowered, and on the other hand, the frequency band with less noise in the fitting sound is amplified to improve the S / N ratio. is there.
[0018]
The first parameter table 8 constitutes a part of the region specifying means, and has a table as shown in FIG. 2A as an example, and each corrector 7a, 7b,... According to the frequency band f. Gain G1 (G11, G12,...) Is adjusted to improve the determination accuracy of the first determiner 9 described later.
[0019]
The first determiner 9 constitutes a part of the region specifying means, and uses the threshold value L1 and the like to determine the level and generation period of the time series signal for each frequency band obtained from each corrector 7a, 7b,. Analysis is performed to roughly specify a fitting sound generation range assumed in advance, that is, a frequency band and a generation period (time series range) of the fitting sound. As a result, the first determiner 9 outputs both pieces of information to the signal extractor 10 to be described later, and the signal extractor 10 stores the digital sound pressure signal generated during the fitting sound generation period (time series range) to be determined. The data is read from the means 5 and output to the subsequent continuous wavelet transform (hereinafter referred to as CWT) computing unit 11. In addition, the frequency band information of the fitting sound to be determined is also output to the CWT calculator 11.
[0020]
Here, the extraction procedure of the digital sound pressure signal applied to the CWT calculator 11 will be described with reference to FIG.
[0021]
(A) in FIG. 5 is a digital sound pressure signal stored in the storage device 5 in time series. (B) is the first time-series signal S1 frequency-separated by the DWT calculator 6 for each frequency band of 1/2 factorial increments. The sound pressure signal includes machine operation sound, equipment ambient sound, and the like in addition to the assumed fitting sound. Since the fitting sound to be determined is usually a composite sound of vibration waves in a plurality of frequency bands, even if the frequency is roughly separated by the DWT calculator 6, a part of the vibration waves is separated in any of the separated frequency bands. Can be caught. Therefore, as shown in FIG. 5B, if the first time series signal S1 frequency-separated by the DWT calculator 6 is evaluated with reference to the frequency band information of the fitting sound assumed in advance, each period is evaluated. It can be discriminated whether the generated sound pressure signal is a fitting sound or a non-fitting sound. In the example of FIG. 5, the sound pressure signals at times t1 to t2 (time series range T1) and times t5 to t6 (time series range T3) are time series generated in a frequency band in which a fitting sound exists in advance. Since the signal level is high, it can be determined that there is a fitting sound, and the frequency band and generation period (time series range) of the fitting sound can be specified as the fitting sound generation range. On the other hand, the sound pressure signal at times t3 to t4 (time series range T2) has a low level of the time series signal generated in the frequency band in which the presumed fitting sound exists, and the time series signal generated in another frequency band. Since this level is high, it can be identified that this is a sound pressure signal other than the fitting sound.
[0022]
The CWT calculator 11 takes in the digital sound pressure signals extracted in the generation periods (time series ranges) T1 and T3 in FIG. 5, for example, extracted by the signal extractor 10, and there is a fitting sound to be determined. Import frequency band information. Therefore, CWT processing is performed in a relatively narrow range in which the frequency band and generation period (time series range) are specified as the generation range of the fitting sound, and the acquired sound pressure signal is sufficiently compared with the DWT calculator 6. Each frequency band is separated and converted into a second time series signal S2.
[0023]
The second corrector 12 is an aggregate of a plurality of correctors 12a, 12b,... That receive the second time-series signal S2 for each frequency band. Each of the correctors 12a, 12b,... Receives a gain G2 (G201, G202,...) That is a correction amount (or correction coefficient) set for each frequency band from a second parameter table 13 described later. The second time series signal S2 is weighted for each frequency band.
[0024]
The second parameter table 13 has a table as shown in FIG. 2B as an example, and a gain G2 (G201, G202,...) Given to each corrector 12a, 12b,. ..) Is adjusted to improve the determination accuracy of the second determiner 14 described later.
[0025]
The second determiner 14 receives the corrected fitting sound signal and the threshold value L2, and determines whether the product is assembled (fitted). As an example of the determination method, the sum of the fitting sound signal levels for each of a plurality of divided frequency bands is obtained and compared with a threshold value L. If the threshold value L2 is exceeded, the result is good (fitting is good) and smaller than the threshold value L2. Is determined to be rejected (with poor fitting).
[0026]
The second determiner 14 displays the result on the display 15 based on the determination result, and outputs the alarm to the alarm 12 when it fails.
[0027]
Next, the determination flow of the vibration wave determination apparatus 100 configured as described above is summarized as shown in FIG. FIG. 7 is a waveform diagram of a CWT signal of a vibration wave.
[0028]
When the apparatus 100 is instructed to start determination, the vibration wave (FIG. 5A) generated from the object 1 is recorded as a digital sound pressure signal by the microphone 2 to the storage device 5 (step 201). The DWT computing unit 6 separates and extracts (step 202) the digital sound pressure signal into time-series signals (FIG. 5B) for each frequency band of 1/2 factorial. In the example of FIG. 5, the sampling frequency of the digital sound pressure signal is 44 KHz, the frequency band 11 is 11 to 22 KHz, the frequency band 10 is 5.5 to 11 KHz, and the frequency band 9 is 2.8 to 5.5 KHz. Appears prominently. In addition, machine operating noise appears in the frequency band below 2.8 KHz.
[0029]
Next, the first corrector 7 receives the gain G1, which is the correction amount from the first parameter table 8, and weights the first time-series signal S1 for each frequency band. The first determiner 9 analyzes the sound pressure level of the first time series signal S1 and the generation period thereof, and generates the fitting sound generation range to be determined, that is, the fitting sound frequency band and the generation period ( (Time series range) is roughly specified (step 203). Based on the output of the first determiner 9, the signal extractor 10 extracts the sound pressure signals of the designated generation periods T 1 and T 3 from the digital sound pressure signals stored in time series in the storage device 5. (Step 203).
[0030]
The CWT calculator 11 finely separates the extracted sound pressure signal in the frequency band of the fitting sound to form a second time series signal S2 as shown in FIG. 7 (step 204). The second corrector 12 receives the correction amount G2 of the second parameter table 13 and appropriately weights and corrects the second time series signal S2 (step 205). Based on the second time-series signal S2 and the threshold value L2, the second determiner 14 determines whether the product is assembled (fitted) or not (step 206). If it is greater than or equal to the threshold value L, a pass display (good fitting) is obtained, and if it is less than the threshold value L, a fail display (with poor fitting) and alarm output are performed (steps 207 and 208).
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a system configuration of an embodiment of the present invention.
2A and 2B are diagrams showing contents of parameter tables 8 and 13 in FIG.
FIG. 3 is a diagram showing a part of the assembly process of the product of FIG. 1;
4 is a diagram showing a sound pressure waveform detected in the process of FIG. 3;
FIG. 5 is a signal waveform diagram of the vibration wave determination device 100 shown in FIG. 1;
6 is a flowchart showing a processing flow of the vibration wave determination apparatus 100 shown in FIG. 1;
7 is a signal waveform diagram of the CWT calculator 11 shown in FIG.
[Explanation of symbols]
1 Object 2 Microphone (vibration wave input means)
5. Storage device (storage means)
6 Discrete Wavelet Transform (DWT) Calculator 7 First corrector (part of region specifying means)
8 First parameter table (part of area specifying means)
9 First determiner (part of area specifying means)
10 signal extractor 11 continuous wavelet transform (CWT) calculator 12 second corrector 13 second parameter table 14 second determiner (determination means)
15 Display 16 Alarm

Claims (5)

Vibration wave input means for detecting and inputting vibration waves generated during operation of the object;
Storage means for storing the input vibration wave as detection information in time series;
Discrete wavelet transform computing means for frequency-separating the detection information to form a first time-series signal for each predetermined frequency band;
Based on the first time-series signal, region specifying means for specifying a time-series range in which a target operation sound indicating at least a predetermined operation state of the object is generated;
Among the detection information, continuous wavelet transform calculation means for extracting detection information within the time series range specified by the area specifying means and continuously separating the frequency,
A vibration wave determination apparatus comprising: a determination unit that determines a state of the object based on a second time-series signal frequency-separated by the continuous wavelet transform calculation unit and a second threshold value. The region specifying means specifies the time-series range in which the target operation sound is generated based on a specific time-series signal in a predetermined frequency band of the first time-series signal and a first threshold value. The vibration wave determination apparatus according to claim 1, wherein The region specifying means includes a first corrector for correcting the level of the first time-series signal for each predetermined frequency band, and a first correction amount set in advance for the first corrector. The time-series range in which the target operation sound is generated is specified based on a first parameter table to be given, a time-series signal obtained by correcting the first time-series signal with the first correction amount, and the first threshold value. The vibration wave determination apparatus according to claim 2, further comprising: a first determination unit that performs the determination. The vibration wave determination device according to claim 3, wherein the first determination unit specifies a frequency band in which the target operation sound is generated in addition to the time-series range in which the target operation sound is generated. The determination means includes a second corrector that corrects the level of the second time-series signal for each frequency band, and a second correction amount that is set in advance to the second corrector. And a second determiner that determines the state of the object based on a time-series signal obtained by correcting the second time-series signal with the second correction amount and a second threshold value. The vibration wave determination apparatus according to claim 3 or 4,

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