JP3066813B2 - Scanning pipe shape inspection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning type pipe shape inspection apparatus which scans a pipe in a non-contact manner by scanning a light beam inside the pipe in a helical manner and inspects the inside shape of the pipe.

[0002]

2. Description of the Related Art To measure the inner diameter (radius) of a tube, for example, a triangulation type non-contact displacement meter using a laser beam has been conventionally used.

[0003] In addition, the arrangement of the optical system is devised so that a light beam is radiated to the entire circumference in the pipe by a rotating mirror, and the light is moved in the longitudinal direction of the pipe by means of a moving means such as a traveling machine. A scanning type tube shape inspection device that continuously measures the inside diameter of a tube while helically scanning the beam and inspects the tube shape (for example, Japanese Patent Application No. 3-43894, “Light beam scanning type distance measuring device”). ) Has also been proposed.

[0004]

In order to examine the inside of a pipe in detail using the above-described pipe shape inspection apparatus, high-density scanning is required, and the amount of data to be measured is accordingly increased. . Further, when the length of the pipe to be measured increases, the amount of accumulated measurement data has to be enormous.

[0005] Therefore, by automatically detecting a defect in the pipe shape and accumulating and processing only the measurement data of the defective portion, a very efficient pipe shape inspection becomes possible, and when the pipe length is increased. Can also be easily handled.

SUMMARY OF THE INVENTION An object of the present invention is to provide a scanning type pipe shape inspection apparatus capable of minimizing the amount of measurement data to be processed by performing automatic defect detection in the measurement of the inside diameter of the pipe for the pipe shape inspection. And

[0007]

FIG. 1 is a block diagram showing a basic configuration of the first aspect of the present invention. In the figure, a pipe inner diameter measuring unit 11 of a scanning type pipe shape inspection apparatus 10 is shown.
Measures the inside diameter of a tube by helically scanning a light beam in all directions in the tube. The automatic defect detection means 12 performs a threshold value judgment on the measured value obtained by the tube inner diameter measuring unit 11 and displays the detection of a defect in the tube according to the measured value exceeding a predetermined threshold value. The measured value processing means 13 provides only the measured value of the portion where the defect is detected by the automatic defect detection means 12 to the in-pipe shape inspection with respect to the measured value obtained by the pipe inner diameter measuring section 11. FIG. 2A shows a threshold determination algorithm in the automatic defect detection means 12 of the present invention. The lower threshold is r ₁ and the upper threshold is r _{2. If} the measured value m is within the range, it is determined that the pipe shape is normal.

According to a second aspect of the present invention, the automatic defect detection means 12 obtains an average value of the measured values in directions different from each other by 180 degrees in the scanning direction of the light beam, and performs a threshold determination on the average value to suppress eccentric error. Means are provided. FIG. 2B shows a threshold determination algorithm in the automatic defect detection means 12 of the present invention. The average value M of the measured value m and the measured value m- _{180 in a} direction different by 180 degrees is obtained, and if the average value M is within the range of the threshold values r ₁ and r ₂ , it is determined that the pipe shape is normal.

According to a third aspect of the present invention, the automatic defect detection means 12 performs notch filter processing for suppressing a single frequency component on a measurement value obtained by helically scanning the light beam, and An eccentricity error suppressing unit that performs a threshold determination by suppressing an eccentricity error having a periodicity synchronized with the rotation of the beam is provided. Note that the automatic defect detection means 1 of the present invention
FIG. 2 (3) shows the algorithm for determining the threshold value in No. 2. Notch filter processing (NF (m)) is performed on the measured value m, and if the notch filter output m 'is within the range of the threshold values r ₁ and r ₂ , it is determined that the pipe shape is normal.

[0010]

[Action] To detect a defective part from the measured value of the pipe inner diameter,
As shown in FIG. 3, predetermined thresholds r ₁ and r ₂ are set inside and outside the regular pipe inner wall surface 21, and when the measured value exceeds these thresholds, it is determined that a defect exists in the pipe shape at that portion. to decide. In the figure, the defect site 22 is raised to the inside of the tube, the measured value of the part is determined to defect sites because it falls below the threshold r _1.

According to the first aspect of the present invention, the measured value of the defective portion is subjected to an in-pipe shape inspection, so that data to be inspected can be minimized, thereby enabling an efficient in-pipe shape inspection. be able to.

However, as shown in FIG. 4, the center of a sensor (tube inner diameter measuring unit) 23 for measuring the inner diameter of the tube and the pipe 24 to be inspected are measured.
Generally, the center of the tube axis does not coincide with the center unless otherwise devised, and a measurement error due to such an eccentricity 26 cannot be avoided in the measured value 25. Hereinafter, a measurement error caused by eccentricity will be described with reference to FIG.

The normal pipe radius is R, the deformation of the pipe is d (α),
The measured value of the sensor 23 is defined as m (θ). Note that α and θ are angles formed by the vector from the tube axis and the center of the sensor to the measurement point with the y-axis. If the sensor 23 has no eccentricity, α = θ and R + d (α) = m (θ). . Here, assuming that the amount of eccentricity of the sensor 23 is e, m (θ) cos θ−e = (R + d (α)) cos α (1) m (θ) sin θ = (R + d (α)) sin α (2) The relationship holds, and from (1) ² + (2) ² , m (θ) ² −2 em (θ) cos θ + (e ² − (R + d (α)) ² ) = 0, and solving this gives m (θ) = {(R + d (α)) ² −e ² sin ² θ} ^1/2 + e cos θ (3) (m (θ)> 0).

In equation (3), ecos θ is a measurement error included in the measured value of the eccentric sensor 23. As shown in FIG. 6, a method of simply comparing the pipe radius 27 with the threshold value 28 (radius In the method, the threshold value is determined with respect to the measurement value including the eccentric error, and the defective portion cannot be specified accurately.

Therefore, according to the present invention, for example, the measured value of the radius of the pipe is stored for half a circumference, and the sum of the measured value 180 degrees before and the measured value at the present time (corresponding to the diameter value) is obtained. By performing a threshold value determination on a value (average value) obtained by halving the value, the sensor 23 can be used to identify a defective portion.
Can be suppressed. Hereinafter, the principle of suppressing the eccentricity error according to the invention (diameter method) according to claim 2 will be described with reference to FIG.

The value M obtained by halving the sum of the measured value 180 degrees before and the measured value at the present time is represented by M = (m (θ) + m (θ−π)) / 2 (4) it can. Here, since the relationship of M ² + (e sin θ) ² ≒ (R + d (α)) ² (5) holds, M 成 り (R + d (α)) ² −e ² sin ² θ｝ ^1/2 . (6) (M> 0), and errors due to eccentricity can be corrected to some extent.

That is, a defective portion can be specified more accurately than the radius method. However, in the diameter method, since the average with the measured value on the opposite side by 180 degrees is averaged, it is difficult to distinguish which one has a defect. In addition, when the eccentricity becomes large, even in a normal pipe in the direction perpendicular to the eccentric direction, the diameter is measured to be small, and it is expected that the pipe will be erroneously determined as a defective portion, and a predetermined value is determined in the measurement. Conditions are required.

When the sensor 23 has an eccentricity, an eccentricity error (ecos θ) is added to the measured value as shown in the equation (3). It has a single frequency component having periodicity (1 cycle / 1 rotation) synchronized with the rotation of the beam. Therefore, the eccentric component can be suppressed by the digital notch filter (DNF).

According to a third aspect of the present invention, a threshold value is determined after removing the eccentric component from the measured value of the sensor 23 having an eccentricity through a digital notch filter, thereby reducing the influence of the eccentricity of the sensor 23. The suppression can be made almost completely, and the defective portion can be specified accurately.

[0020]

FIG. 8 is a block diagram showing an embodiment of a scanning type in-pipe shape inspection apparatus provided with a defect automatic detection means by the diameter method according to the second aspect of the present invention.

In the figure, the measured value of the inner diameter of the tube is converted into digital data via an analog / digital converter (A / D) 31 and the FI which holds the measured data for half a round is stored.
FO (first in first out) memory 32
And input to the adder 33. In the adder 33, FI
The measured data at 180 degrees before and the measured data at that time output from the FO memory 32 are added and given to the divider 34 to calculate the average data of each measured data. The average data is input to a threshold circuit 35 for comparing the lower limit value r ₁ and the upper limit value r _2, and the obtained threshold determination result is output to a counter 37 via a gate circuit 36 for synchronizing with a clock signal.
Given to. The counter 37 generates an address of the memory 38 that stores the average data of the measurement data output from the divider 34.

Here, the tube inner diameter measuring unit 11 shown in FIG.
Is omitted, for example, because the "light beam scanning type distance measuring device" of Japanese Patent Application No. 3-43894 is used, and the automatic defect detection means 12 corresponds to the components from the analog / digital converter 31 to the counter 37. , The measured value processing means 13 corresponds to the configuration after the memory 38. The eccentricity error suppressing means which is a feature of this embodiment is a FIFO memory 3
2. This is realized by the adder 33 and the divider 34, and when this is omitted, the embodiment has a configuration corresponding to the radius method.

With such a configuration, it is possible to obtain measurement data in which the eccentricity error is suppressed according to the principle described with reference to FIG. 7, and it is possible to make a threshold determination on the measurement data (average data). . Further, the counter 37
By providing an address to the memory 38 when a threshold determination result indicating that the measured data exceeds the threshold is output, only the measured data determined to be defective can be stored in the memory 38. Note that by separately managing the scanning position, it is possible to specify a defective portion.

FIG. 9 is a block diagram showing an embodiment of a scanning type in-pipe shape inspection apparatus provided with an automatic defect detection means by the notch filter method according to the third aspect of the present invention. In the figure, the feature of this embodiment is that the F shown in FIG.
A digital notch filter 41 is used in place of the eccentricity error suppressing means composed of the IFO memory 32, the adder 33 and the divider. Other configurations are shown in FIG.
This is the same as that of the embodiment of the scanning type in-pipe shape inspection apparatus provided with the automatic defect detection means by the diameter method shown in FIG. The digital notch filter 41 is publicly known, and suppresses a periodic eccentricity error by utilizing the fact that a single frequency component can be removed.

Here, FIGS. 10, 11 and 12 show the experimental results of the threshold judgment of the inner surface shape in each of the defect automatic detection means of the radius method, the diameter method and the notch filter method.
The tube to be inspected should be tapered so that the depth is thinner so that the suppression effect on the eccentricity of the sensor can be remarkably compared. Is made artificially.

Automatic defect detection means by radius method (FIG. 10)
In this case, a defective part is observed, but a part erroneously determined to be defective due to the eccentricity of the sensor is observed. In addition, the code | symbol is a part, such as an electric wire pulled out from a sensor.

Automatic defect detection means by diameter method (FIG. 11)
In, it is observed that the defect part and the part narrowed in the back are uniformly observed and the eccentricity error is sufficiently suppressed, but the position symmetrical to the defect part and the axis (originally, A part ',' determined to be a defect is also observed at a position that is not a defect), and a part 'similarly determined to be a defect is also observed at a position axially symmetric to the electric wire portion.

In the automatic defect detection means (FIG. 12) using the notch filter method, it is observed that the defect portion and the narrow portion at the back are uniformly observed and the eccentricity error is sufficiently suppressed. It can be seen that the disadvantages of the diameter method have been eliminated.

[0029]

As described above, according to the present invention, a defect in a pipe shape can be automatically detected, so that a monitoring operation during an inspection is facilitated, and only the measurement data of the defective portion is stored. It becomes possible. That is, since the amount of data to be handled can be minimized, it is possible to easily cope with an increase in the pipeline length.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the invention described in claim 1;

FIG. 2 is a diagram showing a threshold determination algorithm in an automatic defect detection means for each claim.

FIG. 3 is a diagram for explaining a threshold value for detecting a defective portion from a measured value of a pipe inner diameter.

FIG. 4 is a diagram illustrating a state of eccentricity of a sensor for measuring a pipe inner diameter.

FIG. 5 is a diagram illustrating a measurement error caused by eccentricity of a sensor.

FIG. 6 is a diagram illustrating a relationship between a measured value of an eccentric sensor and a threshold value.

FIG. 7 is a diagram illustrating the principle of suppressing eccentricity error by the diameter method.

FIG. 8 is a block diagram showing a configuration of an embodiment of the invention described in claim 2;

FIG. 9 is a block diagram showing a configuration of an embodiment of the invention described in claim 3;

FIG. 10 is a diagram showing an experimental result of threshold value determination of the inner surface shape in the radius automatic defect detection means.

FIG. 11 is a diagram showing an experimental result of threshold value determination of the inner surface shape in the defect automatic detection means of the diameter method.

FIG. 12 is a diagram illustrating an experimental result of threshold value determination of the inner surface shape in the automatic defect detection means of the notch filter method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Scanning pipe shape inspection apparatus 11 Pipe inner diameter measuring part 12 Automatic defect detection means 13 Measured value processing means 21 Pipe inner wall surface 22 Defective part 23 Sensor 24 Inspection pipe 25 Measurement value 26 Eccentricity 27 Pipe radius 28 Threshold 31 Analog-digital conversion (A / D) 32 FIFO memory 33 Adder 34 Divider 35 Threshold circuit 36 Gate circuit 37 Counter 38 Memory 41 Digital notch filter

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01N 21/84-21/958

Claims (3)

(57) [Claims] 1. A scanning type pipe shape inspection apparatus which spirally scans a light beam in the entire circumferential direction of a pipe to measure the inner diameter of the pipe, and checks whether or not there is a defect in the pipe shape based on the measured value. A threshold value judgment is performed on the measured value, and an automatic defect detection means for displaying the detection of the defect in the pipe shape in accordance with the measured value exceeding a predetermined threshold value, and only the measured value of the part where the defect is detected by the automatic defect detection means And a measured value processing means for subjecting the sample to an in-pipe shape inspection. 2. The scanning type in-pipe shape inspection apparatus according to claim 1, wherein the automatic defect detecting means obtains an average value of measured values in directions different from each other by 180 degrees in a scanning direction of the light beam. What is claimed is: 1. A scanning type pipe shape inspection apparatus, comprising: an eccentricity error suppressing unit for performing a threshold determination. 3. The scanning-type in-pipe shape inspection apparatus according to claim 1, wherein the automatic defect detecting means suppresses a single frequency component to a measurement value obtained by helically scanning the light beam. A scanning type pipe shape inspection apparatus, comprising: an eccentricity error suppressing unit that performs a notch filter process, suppresses an eccentricity error having a periodicity synchronized with the rotation of the light beam, and performs a threshold determination.