JP5584576B2 - Method and apparatus for detecting position of structure by eddy current exploration - Google Patents

Description

  The present invention relates to a structure position detection method and position detection apparatus by eddy current exploration.

  In structures such as power plants, there are multiple shape change parts and accessory members on the front and back sides of the structure, and it is difficult to visually confirm the positional relationship from the outside of the structure. is there. For example, it is a case where it is confirmed in the heat transfer tube expansion portion of the power plant whether the positions of the tube expansion portion on the inner surface of the heat transfer tube and the tube plate provided on the outer periphery of the heat transfer tube are correctly installed. As one of the methods for detecting the positions of the shape change portions and the attached members on the front surface side and the back surface side of these structures, use of an eddy current exploration technique is considered.

  For example, in Patent Document 1, a position detection sensor is inserted / moved in a pipe, and the position of the weld is detected from the relationship between the sensor detection amount and the wave height and the physical properties. However, in the position detection method of Patent Document 1, when the shape changing portion and the attached member are close to the inner surface and the outer surface of the pipe, the observation waveform has a shape in which each signal is superimposed, and thus it is difficult to detect the position by identifying them. become.

  A multi-frequency method is known as one method for improving detection accuracy. For example, in Patent Document 2, high-frequency and low-frequency are used for detection of a flaw at a shallow position of a steel material and a foreign object at a deep position, and high-precision detection is possible with phase settings adapted to this. However, since Patent Document 2 is directed to wrinkles and foreign matters whose positions and shapes / dimensions are indefinite, variations in observed signal amplitude and phase angle are large. Therefore, complicated signal analysis accompanies identification of both.

JP 2000-249783 A Japanese Patent Laid-Open No. 9-80028

  When detecting the position of multiple types of shape change parts and attachment members existing on the front and back sides of the structure, the observation waveform has a shape in which each detection signal is superimposed. It becomes difficult to detect the position that identifies the.

An object of the present invention is to provide a method and an apparatus for detecting a position by eddy current exploration with respect to a plurality of types of shape change portions and accessory members existing on the front side and the back side of a structure. Here, the shape change part and the attachment member existing on the front surface side and the back surface side of the structure are intended for the designed structure. For this reason, the position and the shape / dimension of the front surface side or the back surface side are known in the shape changing portion and the attached member, unlike the case of the collar or the like. Using this point, in the present invention, the depth position on the front side and the back side is discriminated by two-frequency excitation and phase separation detection, and the size of the structure is discriminated by threshold discrimination of the signal amplitude and width. to improve the accuracy of identifying the shape changing part or accessory members by, we propose a method of detecting the position of that as well as check for search target.

The present invention comprises a plurality of coils in a position detection method by eddy current exploration of an exploration target having a shape changing portion and an attached member provided on the front side or the back side of a designed structure made of a metal material. by using the probe, the surface of the structure by detecting the shape change unit with eddy current probe by a high-frequency current outputs shape change portion detection signal, the back surface side of the structure of low-frequency current Detecting the attached member by detecting eddy current and outputting an attached member detection signal, adjusting the phase of the detection waveform detected by the high-frequency current and the low-frequency current, and detecting the shape change portion detection signal and the attached member detection signal The shape change portion detection signal and the accessory member detection signal are compared with threshold values set in the shape change portion detection signal and the accessory member detection signal , respectively. Make sure And determining the position of the detection signal of the radius variations and accessory members as well as.

Further, the position detecting method according to the eddy current probe, the phase adjustment of the search object detection waveform, the said shape change portion detection signal by the high-frequency current, wherein the said armatures detection signal by the low frequency current, each frequency The phase angle that can be evaluated is determined in accordance with either the X amplitude or the Y amplitude.

In the position detection method by eddy current exploration, an upper limit threshold value and a lower limit threshold value are set for the threshold values set for each of the shape change portion detection signal and the accessory detection signal . A waveform having a maximum value in a section within the set range is determined as a shape change portion detection signal and an attached member detection signal, and a position where the differential value of the signal is zero is determined as a position to be searched .

Further, in the position detection method by eddy current exploration , a distance difference between the position of the shape change portion calculated from the shape change portion detection signal and the position of the attachment member calculated from the attachment member detection signal is the threshold value. It is characterized in that the pass / fail of the installation position of the search target is determined based on the distance difference corresponding to the set range.

Further, in the position detection device by eddy current exploration of the shape changing portion provided on the front surface side or the back surface side of the designed structure made of metal material and the accessory member provided on the other surface side of the structure , A probe having a plurality of coils for performing eddy current exploration with a low-frequency current and a low-frequency current, and a eddy current exploration of a shape change portion provided on the front surface side or the back surface side of the structure by flowing a high-frequency current through the probe. And detecting a shape change portion detection signal, and detecting the accessory member provided on the other surface side of the structure by detecting eddy current on the other surface side of the structure with a low frequency current and detecting the accessory member An eddy current probe that outputs the probe, a scanning device that scans the probe relative to the structure, and a phase adjustment of a detection waveform of the search target by the high-frequency current and the low-frequency current, and the shape changing unit Detection signal Compared to extracts armatures detection signal, the accessory member detection signal and the shape change portion detection signal, and the shape change portion detection signal with a threshold amplitude and width of the set signal to each of the armatures detection signal And a controller for confirming the presence / absence of the shape changing portion and the attached member and determining a position of a detection signal of the shape changing portion and the attached member .

Further, in the position detection device by eddy current exploration, an upper limit threshold value and a lower limit threshold value are set for the threshold values set for each of the shape change portion detection signal and the accessory detection signal , A control device that extracts a waveform having a maximum value in a section within the set range as a shape change portion detection signal and an attached member detection signal and determines a position where the differential value of the signal becomes zero as a position to be searched It is characterized by.

Further, in the position detection device based on eddy current exploration, the control device sets an upper threshold value and a lower threshold value for the signal width threshold values set for each of the shape change portion detection signal and the accessory detection signal. Function, the function of comparing the position of the shape change portion detection signal and the accessory member detection signal, and the position of the shape change portion detection signal and the accessory member detection signal is the distance difference within the setting range of the upper limit threshold value and the lower limit threshold value. It is characterized by having a function of determining whether or not there is.

The present invention relates to a shape detecting portion provided on the front surface side or the back surface side of a designed structure and a position detecting method for an attached member, and a probe is used to search the surface side of the structure with eddy currents with a high-frequency current. Detecting the change part and outputting the shape change part detection signal, searching the eddy current with the low frequency current on the back side, detecting the attached member and outputting the attached member detection signal, the object to be probed by the high frequency current and the low frequency current The shape change portion detection signal and the attached member detection signal are separated and extracted by adjusting the phase of the detection signal , and the shape change portion detection signal and the attached member detection signal are set to the shape change portion detection signal and the attached member detection signal , respectively. the amplitude and the threshold value and compare to Rukoto the width of the signal can be reliably determine the position of the accessory member and radius variations as well as check for search object shape changing part or accessory members.

It is a block diagram showing the structure of the position detection system of this invention. It is a schematic diagram showing the position detection method of this invention. It is a flowchart showing the position detection method by the eddy current search of this invention. It is a Lissajous waveform diagram of a detection signal in eddy current exploration of the present invention. It is a Lissajous waveform diagram of a detection signal in eddy current exploration of the present invention. It is a signal waveform diagram measured between the upper limit threshold value and the lower limit threshold value of the present invention. It is a signal waveform diagram which shows the measurement result in the position detection system of this invention. It is a signal waveform diagram which shows the measurement result in the position detection system of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
[Position detection system]
FIG. 1 is a schematic diagram illustrating a configuration of a position detection system 20 according to an embodiment of the present invention. In FIG. 1, the position detection system 20 includes a monitor 21, a computer 22, an eddy current probe 23, a scanning device 24, and a probe 25. In the position detection system 20, the probe 25 is connected to the eddy current probe 23 with a cable, an excitation signal is transmitted as a search signal of the eddy current probe 23, and a detection signal is received. The eddy current probe 23 is connected to the computer 22 with a cable, and the probe 25 probe signal and probe signal input / output are electrically transmitted and received. The scanning device 24 moves the probe 25 and transmits position information to the computer 22.

  The probe 25 has a shape corresponding to the object, but can be realized by a general configuration having an excitation coil and a detection coil. As an operation of the position detection system, the probe 25 is moved by the scanning device 24, and the search data is acquired from the eddy current probe 23 with respect to the detection position. The search data is processed by a computer 22 as a control device having a software program and displayed on the monitor 21.

FIG. 2 is a schematic diagram showing the principle of the position detection method of the present invention. 25 is a probe, and 33 is a search target. An example in which a shape changing portion 31 having a specific shape exists on the front surface side of the structure 30 provided with the probe 25 and an attachment member 32 separate from the structure 30 is installed on the back surface side of the structure is shown. The attachment member 32 may be provided on the front surface side of the structure 30 and the shape changing portion 31 may be provided on the back surface side.

FIG. 3 shows a flowchart of the position detecting method for the shape changing portion and the attached member by the eddy current exploration according to the embodiment of the present invention. First, two excitation frequencies (high frequency fH, low frequency fL) and two phase angles (θH, θL) of the excitation signal are set. Next , two threshold values , upper limit / lower limit, are set for discriminating detection signals for eddy current exploration (S101).

  Next, a data file is created and measurement of the structure 30 to be searched is started (S102), and two search data of signal X and signal Y are acquired while changing the detection position of the probe with respect to the search target (S103). The measurement is terminated, and the signal X and the signal Y are displayed for the detected position (S104).

Identify the search target from the waveform pattern sandwiched upper and lower thresholds in signal X and signal Y to calculate the position by (S105). Whether or not the structure is correctly installed is determined from the positional relationship of the search target (S106). The presence or absence of the next search target is determined (S107). If there is a search target, the process returns to (S102), and if not, the measurement is terminated.

(Position detection method)
Next, details of the position detection method of FIG. 2 will be described for each step of the flowchart of FIG.

(S101)
In S101, search conditions such as the excitation frequency / phase of the excitation signal of the eddy current probe 23 are set. As the excitation frequency, a high frequency fH for detecting the shape change portion 32 on the front surface side and a low frequency fL for detecting the accessory member 33 on the back surface side are selected .

  In general, in eddy current exploration, two exploration data of X amplitude and Y amplitude are obtained for one excitation frequency, and the mean square value thereof is called the total amplitude. In selecting the high frequency fH, a high frequency fH having a large ratio (Ssurf / Sback) of the total amplitude (Sback) from the attachment member 33 on the back surface side to the total amplitude (Ssurf) from the shape changing portion 32 on the front surface side is selected. It is preferable. On the other hand, in selecting the low frequency fL, it is preferable to select a low frequency fL having a small ratio (Ssurf / Sback).

  However, signals from the attachment member 33 on the back surface side are observed together even at the high frequency fH selected above, and signals from the shape changing portion 32 on the front surface side are observed even at the low frequency fL. .

  Next, the phase angle θH of the high frequency fH and the phase angle θL of the low frequency fL are selected, and the signals from the shape change part 32 on the front surface side and the attachment member 33 on the back surface side are separated. For example, the phase angle θH and the phase angle θL are selected so that the signal amplitude from the attachment member 33 on the back surface side becomes the Y amplitude.

  The Lissajous waveform of the detection signal is schematically shown in FIGS. 4A and 4B. FIG. 4A shows a shape change portion detection signal 41 from the shape change portion 32 on the front surface side and an attachment member detection signal 42 from the attachment member 33 on the back surface side by the excitation signal of the high frequency fH, and FIG. The shape change part detection signal 41 from the shape change part 32 on the front surface side and the attachment member detection signal 42 from the attachment member 33 on the back surface side by the excitation signal of the frequency fL are shown. In FIG. 4A, the shape change portion detection signal 41 is observed largely from the origin O, and the accessory detection signal 42 is observed small in the Y amplitude direction. That is, when the X amplitude direction is observed, the attached member detection signal 42 is greatly reduced, and only the shape change portion detection signal 41 can be determined and detected.

  In FIG. 4B, the shape change portion detection signal 41 is observed small from the origin O, and the accessory detection signal 42 is observed largely in the Y amplitude direction. That is, when the Y amplitude direction is observed, the shape change portion detection signal 41 is greatly reduced, and only the attached member detection signal 42 can be emphasized and detected.

  Table 1 is a table showing combinations of two-frequency excitation and phase separation detection for identifying and detecting the surface shape changing portion signal 41 and the accessory member signal 42. The X amplitude of the high frequency fH is observed for detection of the shape changing unit 31, and the Y amplitude of the low frequency fL is observed for detection of the attached member 32. Hereinafter, in this specification, they are referred to as a signal X and a signal Y, respectively.

  Finally, threshold values are set for the signals X and Y. The shapes / dimensions of the shape changing portion 31 and the attachment member 32 are known. Therefore, the amplitude and width of the signal X and the signal Y can be limited. For example, when the signal X and the signal Y include an end signal of a structure with a large amplitude, an upper limit threshold is set to identify the end signal. Further, since the signal X and the signal Y include device noise having a small amplitude, a lower limit threshold is set to identify the device noise. That is, the upper and lower threshold values that can ensure a statistically sufficient detection rate for detecting the shape changing portion 31 and the attached member 32 by the signals X and Y are set.

  Further, in the position detection method by eddy current exploration, the threshold value set for each of the shape changing unit 31 and the accessory member 32 can be set for the signal width. A threshold value is set according to the dimensions of the shape changing portion 31 and the attached member 32 by the signal X and the signal Y.

(S102)
In S102, a data file for storing exploration data is created and measurement is started. Data acquisition may be started by an operator trigger, or an end signal or the like may be triggered in an automated system.

(S103)
In S103, the signal X and the signal Y are acquired for the detected position. To move the detection position, the probe is scanned by a scanning device, or the target structure is moved by fixing the probe. For obtaining the data of the detection position, an encoder is used or it is calculated from the moving speed and time of the probe or the like. Acquiring pitch for detecting the position is arbitrary but, in the range that can determine the position of its addition to confirm the presence or absence of the target.

(S104)
In S104, the measurement is terminated, and the data of the signal X and the signal Y are displayed for the detected position. Data acquisition may be terminated by an operator trigger, or an end signal or the like may be triggered in an automated system.

(S105)
In S105, to determine the identification及beauty position location of search object from the waveform of the signal X and the signal Y. In the identification of the search target, a signal waveform pattern observed between the upper threshold value and the lower threshold value is used. FIG. 5 shows three possible patterns. The section (a) in FIG. 5 is a waveform that monotonously increases from the lower threshold to the upper threshold, the section (b) is a waveform that monotonously decreases from the upper threshold to the lower threshold, and the section (c) is the lower limit. It is a waveform that decreases to the lower threshold after reaching the maximum from the threshold.

Here, the waveform determined as the search target signal is the section (c) having the maximum value. The decision is made by differentiating the interval between two points crossing the threshold, extracting the waveform with positive / negative inversion (zero) as the target signal, and searching for the detection position where the differential value becomes zero. to determine the position of the target. The observed waveform must be a smooth waveform with sufficient sampling points. If not, change the sampling condition or approximate by a smooth curve. Calculating a position to identify the search target for the signal X and signal Y in the above procedure. The upper threshold and the lower threshold are different for the signal X and the signal Y because the object is different between the shape changing portion and the attached member, and are set in S101.

  Further, it is confirmed that the signal width and the signal Y are within a preset signal width threshold range. The signal X and the signal Y that satisfy both the amplitude and the width of the signal are recognized as the shape change portion and the attached member.

(S106)
In S106, by comparing the position of the accessory member is calculated from the position and the signal Y change in shape of the surface was calculated from the signal X side back side, determines acceptance of setting the positional relationship between search target. For example, displaying or marked and the position of the surface side of the shape changing portion and the back side of the accessory member in color relative to the examination position, position setting range of the surface side of the shape changing portion and the back side of the accessory members Or confirm that the distance is within the range. Furthermore, it is also possible to confirm the quantity of the shape change part on the surface side and the attached member.

(S107)
In S107, when all the objects are evaluated, the measurement is ended. Otherwise, the measurement is started again in S102.

〔measurement data〕
6A and 6B show measurement results obtained by the position detection method of FIG. The high frequency fH = 500 kHz and the low frequency fL = 10 kHz. The phase angle θH = 116 degrees and the phase angle θL = 120 degrees. At the high frequency fH, the upper threshold value was 0.2V and the lower threshold value was 0.05V. At the low frequency fL, the upper threshold value was 2V and the lower threshold value was 0.5V.

6A shows the signal X of the shape change portion on the front surface side, and FIG. 6B shows the signal Y of the accessory member on the back surface side. The signal X and the signal Y are observed within the respective upper and lower threshold values, and are within the signal width threshold range. It was detected by discriminating between the shape change part on the front surface side and the attached member on the back surface side. Position of that is 41.2mm and 66.2mm from the reference position for signal X of the surface-side radius variations were 50.1mm from the reference position for signal Y on the back side of the accessory member. In this case, it is designed in advance so that the attachment member is provided on the back side of the structure between the two shape change parts. This confirms the presence of the shape change part on the front side and the attachment member on the back side. And confirm the position.

20: Position detection system 21: Monitor 22: Computer 23: Eddy current probe 24: Scanning device 25: Probe 30: Structure 31: Shape changer 32: Attached member 33: Search target 41: Shape changer detection signal 42: Attached member detection signal

Claims (7)

In the position detection method by the eddy current exploration of the exploration target having the shape changing portion and the attached member provided on the front side or the back side of the designed structure made of the conductive material,
Using a probe composed of a plurality of coils, eddy current exploration on the surface side of the structure with high frequency current to detect the shape change portion and output a shape change portion detection signal ,
Eddy current exploration at low frequency current on the other side of the structure to detect the attached member and output an attached member detection signal ;
The high frequency current and a detection signal of the search object and the phase adjustment by the low frequency current, separates and extracts the armatures detection signal and the shape change portion detection signal,
Wherein the shape changing part together with the shape change portion detection signal and said accessory member detection signal is compared with the threshold value of the amplitude and width of the signal set for each to confirm the presence or absence of the shape changing portion and the accessory member And a position detection method by eddy current exploration, wherein the position of the detection signal of the attachment member is determined. The position detecting method according to eddy currents exploration according to claim 1, the phase adjustment of the search object detection waveform, and the shape change portion detection signal by the high frequency current, the armatures detection signal by the low frequency current and The position detection method by eddy current exploration is characterized in that a phase angle that can be evaluated corresponding to either X amplitude or Y amplitude at each frequency is determined. 3. The position detection method by eddy current exploration according to claim 1, wherein an upper limit threshold is set for a threshold value of the amplitude and width of the signal set in each of the shape change portion detection signal and the accessory detection signal. A value and a lower threshold value are set , and a waveform having a maximum value in a section within the threshold setting range is determined as the shape change portion detection signal and the accessory detection signal, and a differential value of the signal is zero. A position detection method by eddy current exploration , wherein the position to be determined is determined as the position of the exploration target . The position detection method by eddy current exploration according to claim 3, wherein a distance difference between the position of the shape change portion calculated from the shape change portion detection signal and the position of the attachment member calculated from the attachment member detection signal is calculated. A position detection method by eddy current exploration, wherein pass / fail of the installation position of the exploration target is determined based on a distance difference corresponding to a set range of the threshold value. In the position detecting device by eddy current exploration of the shape changing portion provided on the front side or the back side of the designed structure made of a conductive material and the attached member provided on the other side of the structure,
A probe that is arranged on the surface side of the structure and has a plurality of coils that perform eddy current exploration with a high-frequency current and a low-frequency current;
A high-frequency excitation signal is sent to the probe to detect a shape change portion provided on the front side or the back side of the structure by eddy current detection and output a shape change portion detection signal, and the other side of the structure Eddy current probe with a low frequency excitation signal to detect the attached member provided on the other side of the structure and output an attached member detection signal ;
A scanning device for scanning the probe relative to the structure;
The high frequency current and the search target of the detected waveform by the low frequency current to the phase adjustment, to extract the armatures detection signal and the shape change portion detection signal, the shape change portion detection signal and said accessory member detection signal, the wherein together compared to shape change portion detection signal and said each set to signal that comes member detection signal amplitude and width of the threshold to confirm the presence or absence of the shape changing portion and the accessory member shape changing portion and the A position detection device by eddy current exploration, comprising a control device for determining a position of a detection signal of an attachment member . In the position detection device by eddy current exploration according to claim 5 , with respect to the threshold values of the amplitude and width of the signal set in each of the shape change portion detection signal and the accessory detection signal, an upper limit threshold value is set. A lower threshold value is set , and a waveform having a maximum value in a section within the threshold setting range is extracted as the shape change portion detection signal and the accessory detection signal, and the differential value of the signal becomes zero. A position detecting device by eddy current exploration , comprising a control device for determining a position as the position of the exploration target . The position detection device by eddy current exploration according to claim 6, wherein the control device sets an upper limit threshold value for a threshold value of the signal set for each of the shape change portion detection signal and the accessory detection signal. And a function for setting the lower limit threshold value, a function for comparing the positions of the shape change portion detection signal and the accessory member detection signal, and the positions of the shape change portion detection signal and the accessory member detection signal are the upper limit threshold value and the lower limit. A position detection device by eddy current exploration, characterized in that it has a function of determining whether the distance is within a threshold setting range.

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