JPH04143608A - Device for measuring flatness of steel plate - Google Patents

Abstract

PURPOSE:To enable execution of highly precise computation of strain by conducting the computation of strain for a prescribed time with an output signal from a laser range finder masked, even when detection of a signal is stopped during the detection. CONSTITUTION:When a laser range finder 6 outputs an alarm signal, an alarm signal detecting circuit 36 detects the alarm signal made to bypass a low-pass filter (LPF) 11 thereby and outputs a signal of detection of the alarm signal to a first arithmetic unit 13. The signal detecting circuit 36 outputs the signal to the first arithmetic unit 13 continuously during the detection of the alarm signal, while the arithmetic unit 13 processes distance data as a blank continuously during reception of that signal. Although the signal detecting circuit 36 stops the signal output when the alarm signal is stopped, the first arithmetic unit 13 processes the distance data collected through the LPF, as the blank, also thereafter for a time corresponding to the time constant of the LPF 11. Based on the data blanked partially, each sort of computation of strain can be executed by a second arithmetic unit 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a steel plate flatness measuring device using a laser distance meter.

[Prior Art] The present applicant previously proposed a steel plate flatness measuring device using a non-contact distance meter (Japanese Patent Application No. 162719/1999).
issue). The configuration of the device according to this application is shown in FIG. In the figure, 1 is a conveyance table for the steel plate 10, 2m, 2b are conveyance rolls constituting the conveyance table 1, 5a, 5b, 5c
1 is an idle roller disposed between conveyance rolls, 6 is a plurality of non-contact distance meters arranged at equal intervals in the board width direction between adjacent conveyance rolls, 8 is a controller, and 11 is a non-contact distance meter 6 12 is an amplifier; 13 is a low-pass filter in the controller 8 that removes the influence component of the fluctuation of the steel plate pass line from the output signal waveform of the non-contact distance meter 6; A first computing unit 16 calculates various distortions in the longitudinal direction and width direction regarding the flatness of the steel plate based on the output of the first computing unit 13.
A second computing unit 14.15 in the controller 8 is a pulse generator and a pulse counter for determining the roll period necessary for calculating the strain of the steel plate. And the calculated distortion is CRT
17. It is output to the printer 20 or the like. Note that 21 is a sheet passing detector that detects when the steel sheet is passing.

In the above device, a laser range finder is used as the non-contact range finder 6, and the output of the laser range finder 6 is first input to a low-pass filter 11, and then to a computing unit 13 of section 1. The signal is input to the second computing unit 16 and various distortions are computed.

By the way, a laser rangefinder used for boat fishing is constructed as shown in FIG.
4, the object to be measured 26 is irradiated with light through the light projecting lens 25 and reflected.The reflected light 27 is received by the light receiver 29 of the position detection element through the condensing lens 28, and the amount of the received light is first amplified by the amplifier 30. It is designed to be output. As described above, this output is input to the arithmetic unit 13.16 through the low-pass filter 11, and a distortion calculation is performed.

At this time, the relationship between the operating distance and output voltage of the laser rangefinder is as shown in Figure 7, and although there is a constant proportional relationship between the operating distance and the output voltage, even within the same operating distance range,
Depending on the amount of light received, the output of the laser distance meter will output an alarm signal outside the normal output voltage range. Note that the operating distance shown in the figure is when the standard distance is set to 75 1.

[Problem to be solved by the invention] However, if the surface of the steel plate of the target object is black and dirty, or if there are scratches on the surface as shown in Figure 8, when the laser beam spot of the laser rangefinder passes over it, diffuse reflection will occur. An abnormality may occur, which may cause the amount of light received to be insufficient or excessive. For example, when the laser beam 23 hits a vertical scratch 32 on the steel plate 10, strong diffuse reflection occurs in the C direction (sheet width direction) (see FIG. 8(b)). Due to such an excess or deficiency in the amount of received light, the laser distance meter will output an alarm signal outside the normal output voltage range as described above.

This alarm signal is normally output for a short period of time, but it becomes an obstacle to distortion calculation. That is, when the output waveform of the alarm signal is as shown by the dotted line A in FIG. 9, the signal waveform after passing through the low-pass filter is as shown by the solid line B in the same figure.

Figures 9(a) to (f) show the input pulse width t(1@pressure 7, O
V) is 1ms, 40m5, 100m5, 200 respectively
m5, 300m5. and 600 m5, the step response characteristics of the low-pass filter are shown. When the input pulse width t is 1 to 20 ms, the table shows that t
When the distance becomes 2 ms or more, the peak displacement of the distance meter becomes 0.7 degrees or more and cannot be ignored.

Since the computing units 13 and 16 shown in FIG. 5 sample the distance signal every 50 minutes of the conveyance distance, the influence usually remains for several points after the alarm signal returns, although it depends on the conveyance speed. As a result, spike-like noise 34 as shown in FIG. 10 appears in the steel sheet shape waveform, which has a very negative effect on strain calculation.

As described above, the present invention aims to eliminate measurement defects caused by abnormalities in optical surface properties due to scratches, dirt, etc. on a steel plate, which is a target object, in a flatness measuring device using a laser distance meter. This is an improved system that detects the above alarm signal and performs distortion calculations by masking the output signal from the laser 7 range finder while the signal is being detected and for a certain period of time even after the detection is stopped. By doing so, the present invention aims to provide a flatness measuring device that enables highly accurate distortion calculation.

[Means for Solving the Problems] In order to achieve the above object, a steel plate flatness measuring device according to the present invention is a device for measuring the flatness of a conveyed steel plate using a laser distance meter. It is equipped with a low-pass filter that removes the influence component of the vibration of the steel plate from the output of the rangefinder, and a calculator that calculates distortion related to the flatness of the steel plate based on the output after passing through the low-pass filter. When the laser distance meter outputs an alarm signal due to the presence of an abnormal part in the optical surface texture due to An alarm signal detection circuit is provided which instructs the arithmetic unit to perform calculations while masking the output signal from the laser distance meter.

[Function] Distance data for the steel plate being conveyed is obtained by a laser distance meter, and the output signal waveform of the laser distance meter at this time is as follows:
First, the influence component of the vibration of the steel plate is removed by a low-pass filter, and the influence component of the pass line fluctuation of the steel plate is further removed by the first computing unit, and then input to the second computing unit. Necessary strain calculations are performed, and the calculation results are output as measured values regarding the flatness of the steel plate.

Here, the distance data from the laser distance meter is based on a normal steel plate with no scratches or dirt on the surface of the steel plate.
This is obtained from the output of a good amount of diffusely reflected laser light.

However, since it is fully expected that there may be flaws, dirt, etc. on the surface of the steel plate, the present invention further includes a detection circuit for the alarm signal of the laser distance meter.

This alarm signal detection circuit is installed in parallel with a low-pass filter, and when the laser distance meter outputs an alarm signal due to an abnormality in the optical surface texture of the steel plate,
The output is detected without going through a low-pass filter, and an alarm signal detection signal is output to the first arithmetic unit. The alarm signal detection circuit continues to output a signal while detecting the alarm signal, and the first computing unit continues to mask the output signal from the laser distance meter while receiving the signal. This masking time is the sum of the detection time of the alarm signal and the time corresponding to the time constant of the low-pass filter. Therefore, during this time, the distance data of the laser distance meter is treated as blank. The second arithmetic unit performs various distortion calculations based on this partially blank distance data. Therefore, the above-described spike-like noise no longer appears in the distortion calculation results.

[Example] FIG. 1 is a schematic configuration diagram showing an example of a steel plate flatness measuring device according to the present invention.

In this embodiment, an alarm signal detection circuit 36 is provided in parallel with a low-pass filter 11 for each laser distance meter 6. 37 is an amplifier for alarm signals. The rest of the structure is the same as in FIG. 5, so the same reference numerals are used.

In this embodiment device, when a steel plate 10 to be measured is conveyed on the conveying table 1 and passes above the laser distance meter 6, each laser distance meter 6 irradiates the steel plate 10 with a laser beam, and the laser beam is reflected. Distance data is obtained by receiving light. This distance data is obtained at predetermined pitches in the steel plate conveyance direction (L direction) and the plate width direction (C direction). For example, 50 square pitch in the L direction, C
The direction is 250 to 280 *vs pitch (the number of laser range finders 6 is 16).

The output of each laser distance meter 6 is filtered through a low-pass filter 11. The signal is input to the first arithmetic unit 13 in the controller 8 through the amplifier 12, and is further input to the second arithmetic unit 16, where the necessary distortion calculation is performed.

Here, the low-pass filter 11 is provided to remove the influence component of vibration caused by the rolling of the steel plate, and from empirical facts, the vibration frequency of the rolling of the steel plate is 5Hz.
Based on the above. Furthermore, from the viewpoint of mechanical structure, idle rollers 5g, 5b are located near the conveyor rolls 2a, 2b.
, 5c are provided to prevent shock vibrations as much as possible when the steel plate passes.

The first computing unit 13 is provided to eliminate influence components of changes in the pass line of the steel plate caused by roll shape defects such as bending, eccentricity, and wear of the conveyor rolls 2a and 2b, and looseness of the bearings. . In other words, the original signal waveform output from the laser distance meter 6 includes the vibration of these steel plates and the path line fluctuation components, so in order to obtain the actual distortion signal waveform, these influencing components must be removed. This is because it needs to be removed from the original signal waveform.

Therefore, first, the influence component of the vibration of the steel plate is removed by the low-pass filter 11, and the influence component of the pass line fluctuation is removed by signal processing in the first arithmetic unit 13, so that the pass line is corrected.

Original signal waveform f after passing through the low-pass filter 11
As shown in Fig. 2, (i) is a wavy waveform s (i) containing the influence component of cross line fluctuations and a distorted signal waveform h (i
), the distortion signal waveform h (
i) is h (i) = f (i) −s (i) ・
...It can be obtained from (1).

Here, since the undulating waveform s (i) is mainly a fundamental wave with a period T related to the roll circumference, it can be approximated as follows, and the above equation (1) can be expressed as... (3) be able to.

Here, A: amplitude T: number of data taken at equal intervals over a distance equivalent to the circumference of the transport roll (for example, T-20) i: data number ψ: initial phase. By performing the calculation, the desired distortion signal waveform h(i) can be obtained.

In practice, the Fourier series method is applied to the right-hand side of the above equation (2), and only the first term or harmonic components from the second term onward are also employed to improve accuracy.

The following five items are subject to distortion calculation.

(1) Longitudinal strain (see Figure 3 (a)) The longitudinal strain is
This is the difference between the total maximum value and the minimum distortion value for each channel. That is, longitudinal strain - 1 strain maximum value - strain minimum value Furthermore, the maximum value of this value between channels is also determined.

(2) Strain in the width direction (see FIG. 3(b)) The strain in the width direction is the maximum value over the entire length of the difference between the total maximum value and the minimum strain value in each width direction cross section.

Width direction strain - 1 Strain maximum value - Strain minimum value (3) Maximum steepness (see Figure 3 (c)) The maximum steepness is:
This is the maximum value of the value obtained by dividing the height of the mountain by the pitch of the mountain.

Maximum steepness - [h / 11 maximum for all mountains (4) Curvature at the tip or tail (see Figure 3 (d)) Curvature at the tip or tail is the amount of curvature in the area excluding the dead zone at the tip or tail. It is. Note that warping may occur at the tip and tail ends of the steel plate, so these areas are treated as dead zones and excluded from the measurement target.

Warpage -Δh (5) 1m strain, 2m strain (see Figure 3 (f) and (e)) 1
The m strain and 2m strain are the distances between a line segment drawn between the two highest peaks in a 1 m and 2 m section, respectively, and the lowest valley between them.

Find the maximum value for the total length.

1m strain/2m total strain - h1] At the maximum total length, when the steel plate 10 to be measured has black stains or linear scratches, and the laser beam spot of the laser distance meter 6 passes over it, the laser distance meter The amount of light received by the laser distance meter 6 may be too small or too large, and in this case, the laser distance meter 6 outputs an alarm signal in place of the normal analog output. This alarm signal has a value different from that of a normal analog output, so it can be distinguished from a distance signal. Therefore, when the laser distance meter 6 outputs an alarm signal, the alarm signal detection circuit 36 provided in parallel with the low-pass filter 11 outputs the alarm signal to the low-pass filter 11.
1 is bypassed and detected, and an alarm signal detection signal is output to the first arithmetic unit 13. The alarm signal detection circuit 36 continues to output a signal to the first arithmetic unit 13 while detecting the alarm signal, and the first arithmetic unit 13 continues to process the distance data as blank while receiving the signal.

Since the alarm signal detection circuit 36 performs detection in an extremely short cycle, detection can be performed without delay or oversight. When the alarm signal stops, the alarm signal detection circuit 36 stops outputting the signal, but the first arithmetic unit 13
In this case, the distance data collected through the low-pass filter 11 is processed as blank for a time corresponding to the time constant of the low-pass filter 11. Then, the second arithmetic unit 16 performs various distortion calculations based on this partially blank data.

FIG. 4 is a distortion waveform diagram obtained in this manner, and the XXX portion 38 in the diagram is a blank data portion.

As seen in the figure, spike-like noise caused by the output of the alarm signal does not appear at all, making highly accurate distortion calculation possible.

[Effects of the Invention] As described above, according to the present invention, a flatness measuring device using a laser distance meter is provided with an alarm signal detection circuit configured and operated as described above. Even if there is an unmeasurable area due to partial surface roughness, the unmeasurable area can be removed to a minimum extent from the distance data of the laser rangefinder, making it possible to perform highly accurate distortion calculations. can get.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram showing a method of obtaining distortion from the output of a laser distance meter.
The same figure (a) is the original signal waveform diagram of the laser distance meter, the same figure (b)
Figure 3 (C) is an actual strain signal waveform diagram of the steel plate, Figures 3 and 3 (f) are explanatory diagrams of various types of strain that are measurement items, and Figure 4 is a diagram of the waveform caused by vibration of the steel plate. Measurement data diagram according to the invention, Figure 5 is a configuration diagram of the flatness measuring device according to the prior application, Figure 6 is a configuration diagram of a conventional laser distance meter, and Figure 7 is the relationship between the operating distance and output voltage of the laser distance meter. Figures 8(a) and (b) are explanatory diagrams showing the state when the laser beam spot hits a flaw on the surface of the steel plate, and Figures 9(a) to (f)
are the output characteristic diagrams after passing through a low-pass filter with respect to the input pulse width of the alarm signal of the laser distance meter, and the 10th
The figure shows measurement data with spike-like noise due to flaws on the surface of the steel plate. 1...Transport table 6...Laser distance meter 8...Controller 10...Steel plate 11...Low pass filter 13...First computing unit 16...Second computing unit 36...・Alarm signal detection circuit representative Patent attorney Muneharu Sasaki Diagram (a) Wavy waveform diagram (b) Distortion signal waveform diagram (C) Longitudinal strain = Maximum strain - Minimum distortion diagram (a) Amount in width direction = Maximum strain and minimum strain engraving (b) Engraving (C) Warp = Δh Fig. (d) m3i Fig. (e) Fig. (f) Fig. Fig. (c) Fig. (V) (d) (f) Figure

Claims (1)

[Scope of Claims] A steel plate flatness measuring device using a laser range finder, comprising: a low-pass filter that removes components affected by vibration of the steel plate from the output of the laser range finder, and the laser range finder that has passed through the low-pass filter. a computing unit that calculates distortion related to the flatness of the steel plate based on the output of the laser rangefinder; and a computing unit that bypasses the low-pass filter to detect the output of an alarm signal of the laser distance meter that is generated due to the presence of an abnormal part in the optical surface texture of the steel plate. and an alarm signal detection circuit that instructs the calculator to perform calculations while masking the output signal from the laser distance meter during alarm signal detection and for a time corresponding to the time constant of the low-pass filter. A steel plate flatness measuring device characterized by: