JP2019122979A - Abnormal vibration detection method of rolling mill - Google Patents

Abstract

To provide an abnormal vibration detection method of a rolling mill capable of determining accurately abnormal vibration linked to a chatter mark.SOLUTION: At a cold rolling time of a metal plate, a vibration signal is collected by a vibration meter installed on one or more places on a rolling stand, and frequency analysis by fast Fourier transformation is performed at every prescribed period, to vibration signals collected in a constant speed condition having little fluctuation of rolling speed, and an averaging process is performed to spectrum values of obtained each frequency component.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for detecting abnormal vibration of a rolling mill, which is suitable for detecting chattering generated during rolling of a metal plate by the rolling mill.

In rolling equipment such as cold rolling mills and tension levelers in the manufacture of metal plates, when abnormal vibration (chattering) occurs, marks in the width direction (chatter marks) are formed on the surface of the metal plate, and stripe patterns are formed in the longitudinal direction of the metal plate. In the past, various proposals have been made as a technique for detecting such abnormal vibration.
In patent document 1, a vibration detector is installed in one place abnormality of each part of a metal rolling mill, and when an acceleration of vibration and energy of vibration exceed a fixed value, an abnormal signal is emitted.

  In Patent Document 2, a vibration detector is installed at one place in each part of the rolling mill, and the detected vibration frequency is the natural frequency of the mill, gear meshing failure, bearing failure, play of the spindle-roll coupling, roll 疵The inherent vibration frequency generated by this is regarded as the fundamental frequency for each chatter mark occurrence cause, and the result of frequency analysis of the measured value of the vibration exceeds the set value at the frequency of integral multiples of the fundamental frequency for each chatter mark occurrence It is defined as chattering occurrence.

In Patent Document 3, the vibration in the natural frequency region of the vibration sensor is measured to detect micro slip.
In Patent Document 4, a vibration value during operation detected by a vibration sensor provided in a steel strip rolling mill is subjected to frequency analysis, and the presence or absence of abnormality is detected by collating with a frequency indicating occurrence of a scratch on a bearing of the rolling mill. There is.
In Patent Document 5, the fluctuation of the steel plate tension value between the stands of the rolling mill is read, the fluctuation of the tension value is frequency analyzed, and the strength of each frequency in the frequency band including the natural frequency of the steel plate at the occurrence of abnormality of the rolling mill is determined When it becomes a predetermined threshold abnormality, it is judged as abnormal.
In Patent Document 6, among the vibration values detected by a vibrometer installed on the small diameter roll on the entry and exit side of the rolling mill, a component that matches the frequency of the string vibration of the steel plate exceeds the preset threshold. doing.

Japanese Patent Application Laid-Open No. 50-8445 JP-A-8-108205 Japanese Patent Application Laid-Open No. 7-12641 JP, 2010-234422, A JP, 2014-4612, A JP, 2016-153138, A

By the way, in the prior art described in the above-mentioned patent documents 1, although the method of setting a threshold without doing frequency analysis etc. is proposed to the vibrational acceleration obtained from the installed vibration meter, the vibrational acceleration obtained is The vibration intensity of low frequency is mainly dominant, and there is a problem that it is difficult to capture the change of the vibration intensity on the high frequency side.
Also, as in the prior art described in Patent Documents 2 to 6, a method of monitoring vibration by paying attention to equipment-predicted frequency in advance is also proposed, but the present inventors et al. As a result of investigating the generated chatter marks, there are cases where chatter marks are generated other than the frequency previously predicted in equipment, and there is a problem that chatter mark generation can not be caught if only the characteristic frequency is monitored. . Such chattering is caused by the occurrence of polygon wear on the roll due to the minute vibrations of the roll and the accessory equipment of the rolling mill caused by the breakage of the plate during operation, and the frequency is predicted in advance. There is a problem that it is impossible to do. Furthermore, it is empirically known that the vibration that causes such chatter marks is very small compared to the vibration intensity generated due to, for example, a bearing failure.

In addition, when a threshold is provided without specifying the frequency to detect such a chatter mark as abnormal vibration, meshing vibration of a gear that is not connected to the chatter mark that is normally generated, bearing vibration or vibration noise There is a problem that it is judged as abnormal.
Therefore, the present invention has been made focusing on the problems of the above prior art, and it is an object of the present invention to provide a method of detecting abnormal vibration of a rolling mill which can accurately determine abnormal vibration leading to chatter marks. .

  In order to solve the above-mentioned subject, one mode of the abnormal vibration detection method of the rolling mill concerning the present invention collects a vibration signal with a vibrometer installed in one or more places of a rolling stand at the time of cold rolling of a metal plate. The frequency analysis is performed by fast Fourier transform for every predetermined period on the vibration signal collected when the rolling speed fluctuates at a constant speed with little fluctuation, and the averaging process is performed on the spectrum values of the obtained frequency components. Do.

  According to one aspect of the present invention, abnormal vibration that generates chatter marks can be accurately detected.

It is a system configuration figure showing a schematic structure of rolling equipment to which the present invention can be applied. It is a flowchart which shows an example of the abnormal vibration detection processing procedure effective with a vibration signal processing computer. It is a characteristic diagram which shows the change of a rolling speed. It is a wave form diagram showing the frequency analysis result at the time of high speed rolling, and (a) shows the frequency analysis result before averaging processing, and (b) shows the frequency analysis result of averaging processing error. It is a wave form diagram showing the frequency analysis result at the time of low speed rolling, and (a) shows the frequency analysis result before averaging processing, and (b) shows the frequency analysis result of averaging processing error.

  Hereinafter, an embodiment of a steel block rolling apparatus according to the present invention will be described based on the drawings. Each drawing is schematic and may be different from the actual one. In addition, the following embodiments illustrate apparatuses and methods for embodying the technical idea of the present invention, and the configuration is not specified to the following. That is, the technical idea of the present invention can be variously modified within the technical scope described in the claims.

First, a rolling system configuration to which the present invention can be applied will be described with reference to FIG.
In a cold continuous rolling mill (cold tandem mill) 10 to be subjected to abnormal vibration detection, four rolling stands ST1 to ST4 are arranged in a line at a predetermined interval.
Each rolling stand STi (i = 1 to 4) applies a pressure to a pair of work rolls (WR) 13 and work rolls 13 for rolling the metal plate (steel strip) 12 in the mill housing 11 A pair of backup rolls (BUR) 14 are provided.
A tension meter roll 15 and a pass line roll 16 are provided between the rolling stands.

And while the vibration meter 17 is provided in the upper part of the mill housing 11 of each rolling stand STi, the vibration meter 18 is provided also in the tension meter roll 15 and the pass line roll 16, respectively. The vibration sensors 17 and 18 are preferably piezoelectric element type sensors, but are not limited thereto, and any vibration meter can be applied.
In addition, a rolling speed detection unit 19 is provided which detects the rolling speed by detecting the rotational speed of the work roll 13 of the rolling stand ST4 on the outlet side of the cold continuous rolling mill 10. The rolling speed detection unit 19 is not limited to the case of detecting the rotational speed of the work roll 13, and may be a non-contact type board speed detector such as a contact type board speed detector such as a measuring roll or a laser Doppler method. It may be applied.

The vibration detection signal SV detected by each of the vibration meters 17 and 18 and the rolling speed detection signal Vr detected by the rolling speed detection unit 19 are input to the vibration signal processing computer 20.
The vibration signal processing computer 20 individually performs abnormal vibration detection processing on the vibration detection signals SV input from the respective vibration meters 17 and 18.
In this abnormal vibration detection processing, frequency analysis of a fast Fourier transform (FFT) method is performed on the vibration detection signal SV collected at a predetermined sampling period T1 to represent frequency components included in the vibration detection signal SV and the magnitude thereof. A frequency analysis process for obtaining spectrum values is performed multiple times. Then, the vibration signal processing computer 20 averages each spectrum value, which is the result of frequency analysis processing of a plurality of times, to extract a spectrum value that generates chatter marks, and compares the extracted spectrum value with a threshold to make abnormality. It is determined whether or not it is vibration.

  Here, the sampling period T1 for performing frequency analysis is determined by the capability of the computer mounted and the required frequency analysis range and resolution, but considering that chattering of the rolling mill occurs at 0 to 1000 Hz. The sampling frequency is required to be 2000 Hz or more, and preferably have a frequency resolution of 5 Hz or less. In such a case, the sampling period T1 is preferably 0.2 seconds or more. However, if the sampling cycle is too long, the number of samples decreases in the averaging process performed later, so that the sampling cycle T1 is preferably in the range of 0.2 to 1 second.

The averaging process is performed in a section (referred to as an average processing section) rolling at a constant rolling speed for a fixed time or more. The averaging process is a very general arithmetic averaging process, and the result of dividing the frequency analysis result (N times) for each sampling cycle T1 obtained in the averaging process interval by frequency and dividing by the sampling frequency N As the average value.
Here, as for the constant rolling speed, it is desirable that the rolling speed is rolling within a fluctuation range of, for example, ± 1 m / min. This is because, when averaging is performed in a section where the fluctuation of the rolling speed is large, the frequency response obtained for the vibration whose frequency changes according to the speed becomes broad.
In addition, it is desirable that the predetermined time or more be a time at which a frequency analysis result of at least 10 points or more can be obtained at a constant rolling speed. For example, in the case where the sampling period T1 is 1 second, it is necessary that the constant time rolling is performed at a constant rolling speed for 10 seconds or more.

Next, the abnormal vibration detection processing will be specifically described with reference to the flowchart of FIG.
This abnormal vibration detection processing is executed as timer interrupt processing for the main program in an operation cycle obtained by adding a margin to the sampling cycle T1 of the vibration detection signal SV.
In this abnormal vibration detection process, as shown in FIG. 2, first, in step S1, the rolling speed Vr (n) detected by the rolling speed detector 19 is read, and then, the process proceeds to step S2 and the vibration detection signal SV (n And the vibration detection signal read processing to be stored in the vibration detection signal storage area is started. In the vibration detection signal reading process, the vibration detection signal SV output from the vibration meter 17 or 18 is collected during the sampling period T1 and stored in the vibration detection signal storage area 22 formed in the storage unit 21.

Subsequently, the process proceeds to step S3, and it is determined whether the rolling speed flag F is reset to "0". If F = "0", the process proceeds to step S4. In step S4, the rolling speed Vr (n) read in step S1 is stored as the reference rolling speed Vrb in the primary storage unit as the reference rolling speed Vrb, and then the process proceeds to step S5 and the rolling speed flag F is set to "1". Finish the loading process.
On the other hand, when the determination result in step S3 is that the rolling speed flag F is set to "1", the process proceeds to step S6, and the absolute value obtained by subtracting the rolling speed Vr (n) read in step S1 from the reference rolling speed Vrb. It is determined whether the value exceeds a preset speed deviation ΔV (for example, 1 m / min). This determination is to determine whether the rolling speed Vr of the metal plate 12 is a constant speed. When the determination result in step S6 is | Vrb−Vr (n) |> ΔV, it is determined that the vehicle is not in the constant speed state, and the process proceeds to step S7 to erase the analysis result in the frequency analysis result storage area The process proceeds to step S4 described above.

Further, when the determination result in step S6 is | Vrb−Vr (n) | ≦ ΔV, it is determined that the rolling speed Vr of the metal plate 12 is a constant speed with little fluctuation, and the process proceeds to step S8.
In this step S8, the frequency analysis of the fast Fourier transform (FFT) method is performed on the previous vibration detection signal SV (n-1) stored in the vibration detection signal storage area, and the frequency component and its size included in the vibration signal After obtaining an analysis result composed of spectrum values representing heights and storing the analysis result in the analysis result storage area 23 formed in the storage unit 21, the process proceeds to step S9.

In step S9, it is determined whether a predetermined number N (for example, N = 10) of analysis results are accumulated in the analysis result storage area. If the determination result in step S9 indicates that the number of stored analysis results has not reached N, the timer interrupt processing is ended as it is.
In addition, when the determination result in step S9 reaches N, the number of storages of analysis results reaches N, the process proceeds to step S10, the averaging process of each analysis result is performed, and the process proceeds to step S11. In this averaging process, a total spectrum value obtained by adding spectrum values for each frequency of each analysis result is divided by the number N to calculate an average value.
In step S11, the spectrum value of the chattering cause frequency for generating the chatter mark is extracted from the averaged frequency analysis result, and the spectrum value of the chattering cause frequency and the spectrum value of the chattering cause frequency at the normal time set beforehand. Compare to threshold.

  Here, the chattering cause frequency changes according to the rolling speed of the cold rolling mill 10. That is, as shown in FIG. 3, when rolling is started from the stopped state, the rolling speed in the case of rolling the metal plate 12 by the cold continuous rolling mill 10 increases rapidly in about 10 seconds to a high speed rolling speed of about 800 m / min. High speed constant rolling state after speeding up and then slowing down to low speed rolling speed of about 600 m / min after about 200 seconds, then low constant speed rolling state and over 270 seconds from this low constant speed rolling state At the moment it is decelerated at once and stopped. As described above, the rolling speed changes in two stages of the high constant speed rolling state and the low constant speed rolling state, and the chattering cause frequency also changes accordingly. That is, the chattering cause frequency in the high constant speed rolling state is 510 Hz, and the chattering cause frequency in the low constant speed rolling state is 400 Hz.

Therefore, when the cold continuous rolling mill 10 is normal, the spectrum value at the chattering cause frequency 510 Hz in the high constant speed rolling state is determined as the spectrum threshold, and the spectrum value at the chattering cause frequency 400 Hz in the low constant speed rolling state Is determined as the spectrum threshold, and the spectrum threshold of the chattering cause frequency is determined based on the reference rolling speed Vrb.
If the spectrum value extracted as the comparison result in step S11 exceeds the spectrum threshold value, it is determined that chattering has occurred, the process proceeds to step S12, an alarm is issued, and then the process proceeds to step S13. Further, when the determination result in step S11 is that the extracted spectrum value is equal to or less than the spectrum threshold value, it is determined as normal, and the process proceeds to step S13.
In this step S13, after the stored data in the frequency analysis result storage area and the vibration detection signal storage area are erased, the process proceeds to step S14, and the timer interrupt processing is ended since the rolling speed flag F is reset to "0". .

Next, an abnormal vibration detection method according to the present invention will be described.
In this abnormal vibration detection method, the abnormality determination is performed in a state where the rolling state in which the fluctuation of the rolling speed Vr is small is continued for a predetermined time. Therefore, as shown in the flowchart of FIG. 2 described above, the rolling speed Vr (n) is read from the rolling speed detection unit 19 every time the vibration detection signal is read from the vibration meter 17 or 18 and the constant speed rolling state is determined It is determined.
Therefore, as shown in FIG. 3, assuming that cold rolling is started at time t1 and transition to the high constant speed rolling state is performed at time t2, the rolling speed Vr becomes steep between time t1 and time t2. It is increasing with the slope. At this time, when the abnormality determination process of FIG. 2 is started, the rolling speed flag F is initialized to “0”, so the rolling speed Vr (n) read in step S1 is stored as the reference rolling speed Vrb ( Step S4). At this time, since the rolling speed flag F is set to "1", at the next timer interruption, the process proceeds from step S3 to step S6, and the read rolling speed Vr (n) is relative to the reference rolling speed Vrb. It is determined whether or not the vehicle is in a constant speed state within the speed deviation ΔV (± 1 m / min).

At this time, in the acceleration state of the rolling speed Vr, | Vrb−Vr (n) |> ΔV, and the analysis result is not stored in the frequency analysis result storage unit, but the stored data is erased and the rolling speed read Vr (n) is again stored as the reference rolling speed Vrb.
This state is repeated, and the rolling speed changes to the high constant speed rolling state, and analysis of the read vibration detection signal SV (n) is started from the time when the fluctuation of the rolling speed Vr decreases. In this case, the vibration detection signal SV (n) whose reading is started in step S2 takes 0.2 to 1 second to complete reading, so the vibration detection signal SV (n) stored in the previous timer interrupt process The frequency analysis of the fast Fourier transform method is performed for (step S8).

In the frequency analysis result at this time, as shown in FIG. 4A, a large number of spectrum values are generated for each frequency in a frequency range of 0 to 1000 Hz. Here, the chattering cause frequency 510 Hz at the rolling speed Vr = 800 m / min in the high constant speed rolling state is buried in the spectrum value due to the nearby vibration, and the spectrum value of the chattering cause frequency can not be extracted.
For this reason, in the present embodiment, in a state where the rolling speed Vr maintains a constant speed, multiple N times (N = 10) frequency analysis is executed every time the vibration detection signal SV is sampled, and the analysis result is a frequency Store in the analysis result storage area.

Then, when a plurality N of frequency analysis results are stored in the frequency analysis result storage area, the process proceeds from step S9 to step S10, and spectrum values for each frequency in the stored plurality N of frequency analysis results are obtained. Averaging process. That is, the average spectrum value is calculated by performing arithmetic mean processing in which the total spectrum value obtained by individually adding the spectrum values at the frequency of each frequency analysis result is divided by the storage number N.
Thus, the average spectrum value at the chattering cause frequency of 510 Hz is caused by the generation of chattering continuously by averaging the N frequency analysis results and the spectrum value for each frequency. The peak of the average spectrum value of the frequency appears clearly as shown in FIG. 4 (b). On the other hand, since the vibration is irregular at frequencies before and after the chattering cause frequency, the average spectrum value becomes smaller when averaged.

  Therefore, an average spectrum value of the chattering cause frequency of 510 Hz is extracted from FIG. 4B, and this average spectrum value is compared with a spectrum threshold which is a spectrum value at the normal time (step S11). This makes it possible to determine whether the vibration is abnormal or not, and when the average spectrum value of the chattering cause frequency 510 Hz is equal to or less than the spectrum threshold, it is judged normal and storage of the frequency analysis result storage area and the vibration detection signal storage area The data is erased (step S13), and the rolling speed flag F is reset to "0" (step S14).

Therefore, at the next timer interruption timing, a new reference rolling speed Vrb is set, and the reading process of the vibration detection signal SV, the frequency analysis process, and the averaging process are executed.
If one or more vibration detection signals are stored in the vibration detection signal storage area, and the rolling speed Vr (n) fluctuates from the reference rolling speed Vrb beyond the speed deviation ΔV, The stored vibration detection signal and frequency analysis result are erased, and frequency analysis is newly started from the vibration detection signal being read.

After that, when the rolling speed Vr starts decelerating at time t3, frequency analysis is interrupted, and low constant speed rolling state is entered at time t4, and frequency analysis is performed when constant speed state is continued for a fixed time, When the analysis results become N, the averaging process is executed to detect the abnormal vibration by comparing the average spectrum value of the chattering cause frequency 400 Hz with the spectrum threshold value which is the spectrum value at the normal time.
Also in this case, as shown in FIG. 5 (a), the frequency analysis result before the averaging process can determine the peak value to some extent, but as shown in FIG. 5 (b) by performing the averaging process. In addition, the average spectrum value at the chattering cause frequency of 400 Hz can be determined more clearly.

  As described above, according to the present embodiment, the vibration detection signal is sampled at a predetermined sampling period and the sampled vibration detection signal is subjected to frequency analysis for each frequency while the rolling speed is maintained at a constant speed for a fixed period. Perform a frequency analysis process to obtain spectral values of The spectrum value of the chattering cause frequency can be accurately detected by obtaining the average spectrum value at the chattering cause frequency by repeating the frequency analysis process a plurality of times and averaging the plural frequency analysis results. Then, by comparing the average spectrum value with the spectrum threshold value, it can be accurately determined whether or not abnormal vibration causing chattering has occurred.

In the above embodiment, the case where the frequency analysis is repeated ten times while the sampling period of the vibration detection signal SV is 1 second has been described, but the present invention is not limited to this. As described above, the sampling period T1 is It may be set to 0.2 seconds or more, and the number of analysis results to be averaged is not limited to 10, and can be set arbitrarily.
In the above embodiment, although the rolling speed Vr is also collected each time the vibration detection signal is collected, the present invention is not limited to this, and a predetermined number of vibration detection signals are continuously collected. In the meantime, the rolling speed Vr may be collected at a predetermined interval, and when there is a fluctuation of the rolling speed, collection of the vibration detection signal may be started again.

In this case, frequency analysis processing may be executed each time a vibration detection signal with a sampling period T1 is collected, and frequency analysis results may be averaged when N frequency analysis results are reached.
Moreover, although the said embodiment demonstrated the case where a rolling speed was detected by last stand ST4, it is not limited to this, You may make it provide separately in each rolling stand ST1-ST3.

  DESCRIPTION OF SYMBOLS 10 ... Cold continuous rolling machine, 11 ... Housing, 12 ... Metal plate, 13 ... Work roll, 14 ... Backup roll, 15 ... Tension meter roll, 16 ... Pass line roll, 17, 18 ... Vibration meter, 19 ... Rolling speed Detection unit, 20: Vibration signal processing computer, 21: Vibration detection signal storage area, 22: Frequency analysis result storage area

Claims (2)

  During cold rolling of a metal plate, vibration signals are collected by a vibrometer installed at one or more locations of the rolling stand, and the vibration signals collected when the rolling speed is in a constant speed state with little fluctuation every predetermined cycle A method of detecting abnormal vibration of a rolling mill, comprising performing frequency analysis by fast Fourier transform and performing averaging processing on spectrum values of the respective frequency components obtained.   The rolling mill according to claim 1, characterized in that when the spectrum value subjected to the averaging process exceeds the spectrum value at normal time at the corresponding constant speed rolling speed obtained in advance, it is judged as abnormal. Abnormal vibration detection method.

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