JP3377171B2 - Method and apparatus for detecting paint film damage position of buried steel pipe - Google Patents
Method and apparatus for detecting paint film damage position of buried steel pipeInfo
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- JP3377171B2 JP3377171B2 JP34199197A JP34199197A JP3377171B2 JP 3377171 B2 JP3377171 B2 JP 3377171B2 JP 34199197 A JP34199197 A JP 34199197A JP 34199197 A JP34199197 A JP 34199197A JP 3377171 B2 JP3377171 B2 JP 3377171B2
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- signal
- steel pipe
- buried steel
- coating film
- voltage
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- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、埋設された塗覆装
鋼管の塗膜損傷部位を、地上にて非接触で検出する方法
および装置に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for non-contact detection on the ground of a coating film damaged portion of a buried coated steel pipe.
【０００２】[0002]
【従来技術】一般に、埋設される鋼管には腐食を防止す
るための塗覆装がその周囲に施されている。しかしなが
ら、何らかの原因によりこの塗覆が損傷すると損傷部位
から腐食が進行し、やがて鋼管に腐食孔が生じるように
なる。このため、埋設鋼管の保全上、塗膜損傷の有無と
その位置を早期に発見することが重要である。2. Description of the Related Art Generally, a steel pipe to be buried is coated around its periphery to prevent corrosion. However, if the coating is damaged for some reason, corrosion will progress from the damaged site, and eventually corrosion holes will be formed in the steel pipe. Therefore, in order to maintain the buried steel pipe, it is important to detect the presence or absence of coating film damage and its position at an early stage.
【０００３】これに応えるものとして、従来から種々の
塗膜損傷検出が提案されている。これらのうち、作業
性、測定精度の面から優れているものとして、電位差法
が周知である。In response to this, various types of coating film damage detection have been conventionally proposed. Of these, the potentiometric method is well known as being excellent in workability and measurement accuracy.
【０００４】図８にこの方法を示す。図８において、１
は埋設鋼管、２は交流電源、３は電力増幅器、４は接地
電極、５は埋設鋼管１の塗膜損傷部、６は探査機、６
ａ、６ｂは探査機の車輪電極、７はフィルタ、８は電位
差検出器である。FIG. 8 shows this method. In FIG. 8, 1
Is a buried steel pipe, 2 is an AC power source, 3 is a power amplifier, 4 is a ground electrode, 5 is a coating film damaged portion of the buried steel pipe 1, 6 is a probe, 6
Reference numerals a and 6b are wheel electrodes of the probe, 7 is a filter, and 8 is a potential difference detector.
【０００５】埋設鋼管１と接地電極４の間に、交流電源
２から電力増幅器３を介して電圧を印加し、電流を通じ
る。この状態で探査機６を、埋設鋼管の管軸方向に沿っ
て地表面上を移動させる。探査機６には、その前後方向
に１対の車輪電極６ａ、６ｂが設けられており、それぞ
れが接触している地面の電位を検出する。これらの電位
の差は、フィルタ７を介して電圧検出器８で検出され
る。A voltage is applied between the buried steel pipe 1 and the ground electrode 4 from the AC power source 2 through the power amplifier 3 to pass a current. In this state, the probe 6 is moved on the ground surface along the pipe axis direction of the buried steel pipe. The probe 6 is provided with a pair of wheel electrodes 6a and 6b in the front-rear direction thereof, and detects the potential of the ground with which they are in contact. The difference between these potentials is detected by the voltage detector 8 via the filter 7.
【０００６】埋設鋼管１の塗膜に塗膜損傷部５がある場
合には、印加電圧に応じて塗膜損傷部５より電流が流入
し、付近の土壌中に電位勾配を作る。この電位勾配の方
向は、塗膜損傷部５の真上の位置を境にして逆転する。
よって、探査機６を埋設鋼管の管軸方向に沿って走行さ
せ、走行距離を横軸に、車輪電極６ａ，６ｂの間の電位
差を縦軸にとってグラフを作ると、塗膜損傷部５の真上
でＳ字型のカーブを描く。よって、このＳ字型のカーブ
の中央の位置（ゼロクロス点）を検出することにより、
塗膜損傷部５の位置を地上から非接触で検出できる。When the coating film of the buried steel pipe 1 has a coating film damaged portion 5, a current flows from the coating film damaged portion 5 in accordance with the applied voltage, and a potential gradient is created in the nearby soil. The direction of this potential gradient is reversed at the position directly above the coating film damaged portion 5 as a boundary.
Therefore, when the explorer 6 is run along the pipe axis direction of the buried steel pipe and a graph is made with the running distance as the horizontal axis and the potential difference between the wheel electrodes 6a and 6b as the vertical axis, the true value of the coating film damaged portion 5 can be obtained. Draw an S-shaped curve above. Therefore, by detecting the center position (zero cross point) of this S-shaped curve,
The position of the coating film damaged portion 5 can be detected from the ground without contact.
【０００７】図９は、この方法による塗膜損傷部の検出
結果を示す図である。対象とした埋設鋼管は、管径１０
０Ａ、管長１０ｍのＰＬＰ導管であり、約１ｍの深さに
埋設されたものである。塗膜損傷のサイズは５ｍｍ×４
ｍｍのものであった。探査機の車輪電極の間隔は１ｍで
あり、塗膜損傷部への流入電流は１０ｍＡ（４４０Ｈ
ｚ）である。電位差の検出は、アスファルト塗装上で散
水処理をして行った。FIG. 9 is a diagram showing a result of detection of a coating film damaged portion by this method. The target buried steel pipe has a diameter of 10
The PLP conduit has a length of 0 m and a length of 10 m, and is buried at a depth of about 1 m. The size of the coating damage is 5 mm x 4
mm. The space between the wheel electrodes of the spacecraft is 1 m, and the current flowing into the damaged coating film is 10 mA (440 H).
z). The detection of the potential difference was performed by spraying water on asphalt coating.
【０００８】図９において横軸は探査機の位置、縦軸は
探査機の車輪電極間の電位差である。図９において、電
位差は左半分では正であり、右半分は負である。これ
は、左半分の位置と右半分の位置では電位勾配の方向が
逆転していることを示す。そして、前述したように、図
９におけるＳ字カーブの中心、すなわち電位差がゼロク
ロスする位置を、塗膜損傷位置の真上であると判定する
ことができる。In FIG. 9, the horizontal axis represents the position of the spacecraft, and the vertical axis represents the potential difference between the wheel electrodes of the spacecraft. In FIG. 9, the potential difference is positive in the left half and negative in the right half. This indicates that the direction of the potential gradient is reversed at the left half position and the right half position. Then, as described above, the center of the S-shaped curve in FIG. 9, that is, the position where the potential difference crosses zero can be determined to be directly above the coating film damage position.
【０００９】しかしながら、前記周知の電位差法には、
以下のような問題点があった。すなわち、実際の塗膜損
傷の検出は探査機をアスファルト上に走らせて行うた
め、接地抵抗が大きく、車輪電極間の電位差として検出
される検出信号は微弱なものとならざるを得ない。一
方、地中には迷走電流が流れており、このため、土壌が
固有電位を有している。これが車輪電極間の電位差を測
定するときのノイズとなる。また、商用周波数による誘
導電流が電位差検出に重畳され、これもノイズとなる。
これらのノイズはフィルタ処理によりある程度は除去さ
れるものの、もともとの信号のＳ／Ｎ比が小さいため、
完全に除去することはできない。このため、塗膜損傷部
を精度良く確実に検知することは困難である。However, the known potential difference method is
There were the following problems. That is, since the actual damage to the coating film is detected by running the probe on the asphalt, the ground resistance is large, and the detection signal detected as the potential difference between the wheel electrodes must be weak. On the other hand, a stray current is flowing in the ground, so that the soil has an intrinsic potential. This becomes noise when measuring the potential difference between the wheel electrodes. Further, the induced current due to the commercial frequency is superimposed on the potential difference detection, which also becomes noise.
Although these noises are removed to some extent by the filtering process, since the original signal S / N ratio is small,
It cannot be completely removed. Therefore, it is difficult to detect the damaged portion of the coating film accurately and reliably.
【００１０】発明者らは、これらの問題点を解決する方
法として、ランダム信号又は擬似ランダム信号を用い、
信号処理として相関処理を用いた塗膜探傷方法及び装置
の発明を行い、特願平９−５７１０２号として特許出願
した。The inventors have used a random signal or a pseudo-random signal as a method for solving these problems,
An invention of a coating film flaw detection method and apparatus using correlation processing as signal processing was invented, and a patent application was filed as Japanese Patent Application No. 9-57102.
【００１１】この発明は、埋設管と大地の間に交流電圧
を印加することにより当該埋設管に交流電流を流し、管
軸方向に沿った位置にある２点間の電位差を当該２点を
移動させながら順次検出することにより、前記交流電流
により地上に発生する電位分布を測定し、その電位分布
の変化から当該埋設管の塗膜損傷位置を検知する方法に
おいて、埋設鋼管に印加する交流電圧にランダム信号ま
たは擬似ランダム信号を用い、前記埋設鋼管に印加する
交流電圧の波形と、前記２点間の電位差の検出波形との
間で相互相関処理を行い、そのピーク値を前記２点間の
電位差の代表値とし、当該代表値より電位分布を求め、
求めた電位分布の変化から当該埋設管の塗膜損傷位置を
検出するものである。ここに擬似ランダム信号とは、長
期間においては繰り返し周期がありランダム性は失われ
るが、周期内においてはランダム性が保たれるような信
号をいう。According to the present invention, an alternating current is applied to the buried pipe by applying an alternating voltage between the buried pipe and the ground, and the potential difference between two points located along the pipe axis is moved between the two points. By sequentially detecting while measuring the potential distribution generated on the ground by the AC current, in the method of detecting the coating film damage position of the buried pipe from the change in the potential distribution, in the AC voltage applied to the buried steel pipe Using a random signal or a pseudo-random signal, cross-correlation processing is performed between the waveform of the AC voltage applied to the buried steel pipe and the detection waveform of the potential difference between the two points, and the peak value thereof is the potential difference between the two points. , The potential distribution is calculated from the representative value,
The position where the coating film is damaged on the buried pipe is detected from the obtained change in the potential distribution. Here, the pseudo-random signal refers to a signal that has a repeating cycle for a long period of time and loses randomness, but maintains randomness within the cycle.
【００１２】この方法によれば、印加電圧の波形と検出
信号の波形の相互相関をとった場合、その相互相関の計
算中、たとえば検出信号をシフトして掛け算を行う過程
において、印加電圧とシフトされた検出信号が同じパタ
ーンとなって同期のとれた位置に相互相関のピークが現
れる。印加電圧とパターンの異なるノイズは、相互相関
をとることによって打ち消されてしまい、ピーク値には
ほとんど影響を与えない。印加電圧はランダム信号また
は擬似ランダム信号であるので、印加電圧に基づかない
ノイズが印加電圧のパターンと同じパターンになること
はない。According to this method, when the cross-correlation between the waveform of the applied voltage and the waveform of the detection signal is taken, the shift of the applied voltage and the shift of the detection signal are performed during the calculation of the cross-correlation. The detected signals have the same pattern, and a peak of cross-correlation appears at a synchronized position. The noise having a different pattern from the applied voltage is canceled by taking the cross-correlation and has almost no effect on the peak value. Since the applied voltage is a random signal or a pseudo random signal, noise that is not based on the applied voltage does not have the same pattern as the applied voltage pattern.
【００１３】よって、本方法によれば、印加電圧に起因
する検出信号のみが車輪電極間の電位差の代表値として
検出されることになるので、Ｓ／Ｎ比が改善される。こ
の代表値を用いて電位分布を求め、その電位分布の変化
から前記従来の方法と同じ方法で塗膜損傷位置を検出す
ることにすれば、前記電位差法に比較して、塗膜損傷位
置を精度良く検出できる。Therefore, according to this method, only the detection signal resulting from the applied voltage is detected as the representative value of the potential difference between the wheel electrodes, so that the S / N ratio is improved. The potential distribution is obtained using this representative value, and if the coating film damage position is detected from the change in the potential distribution by the same method as the above-mentioned conventional method, the coating film damage position is compared with the potential difference method. Can be detected accurately.
【００１４】図１０は、この方法の実施の形態の一例を
示す図である。図１０において、１は埋設鋼管、３は電
力増幅器、４は接地電極、５は埋設鋼管１の塗膜損傷
部、６は探査機、６ａ、６ｂは探査機の車輪電極、１０
はＭ系列信号発生器、１１はＭ系列参照信号発生器、１
２は相関処理部、１３はパーソナルコンピュータ演算部
である。FIG. 10 is a diagram showing an example of an embodiment of this method. In FIG. 10, 1 is a buried steel pipe, 3 is a power amplifier, 4 is a ground electrode, 5 is a coating film damaged portion of the buried steel pipe 1, 6 is a probe, 6a and 6b are wheel electrodes of the probe, 10
Is an M-sequence signal generator, 11 is an M-sequence reference signal generator, 1
Reference numeral 2 is a correlation processing unit, and 13 is a personal computer arithmetic unit.
【００１５】この実施の形態においては、埋設鋼管１に
印加する擬似ランダム信号としてＭ系列信号を用いる。
図１１にＭ系列信号の発生回路の例を示す。Ｍ系列信号
は、図１１のようなフィードバック回路を有するシフト
レジスタによって容易に作成できる。図１２にＭ系列信
号の信号波形とその自己相関信号波形の例を示す。図１
２において、横軸は時間、縦軸は信号の大きさ、τａは
Ｍ系列信号を生成するシフトレジスタに与えられるクロ
ックの周期である。In this embodiment, an M-sequence signal is used as the pseudo random signal applied to the buried steel pipe 1.
FIG. 11 shows an example of an M-sequence signal generation circuit. The M-sequence signal can be easily created by a shift register having a feedback circuit as shown in FIG. FIG. 12 shows an example of the signal waveform of the M-sequence signal and its autocorrelation signal waveform. Figure 1
In FIG. 2, the horizontal axis represents time, the vertical axis represents the signal magnitude, and τa is the cycle of the clock given to the shift register that generates the M-sequence signal.
【００１６】Ｍ系列信号は、周期性のある擬似ランダム
信号であり、シフトレジスタのビット数に対応する周期
を持つので、自己相関をとると図１２（ｂ）に示すよう
なピーク値を周期的に持つ。このことから、他の信号と
の相互相関をとれば、当該Ｍ系列信号とパターンの一致
する信号のみが高いピーク値を有する相互相互相関値を
持つことがわかる。前記実施の態様においては、この性
質を利用してノイズ信号の低減を図るものである。Since the M-sequence signal is a pseudo random signal having a periodicity and has a period corresponding to the number of bits of the shift register, the peak value as shown in FIG. To have. From this, it can be seen that if the cross-correlation with other signals is taken, only the signal whose pattern matches the M-sequence signal has the cross-correlation value having a high peak value. In the above embodiment, this property is utilized to reduce the noise signal.
【００１７】図１０において、Ｍ系列信号発生器１０か
らのＭ系列信号は、電力増幅器３で増幅されて、埋設鋼
管１と接地電極４の間に電圧として印加される。この状
態で探査機６を、埋設鋼管の管軸方向に沿って地表面上
を移動させる。探査機６には、その前後方向に１対の車
輪電極６ａ、６ｂが設けられており、それぞれが接触し
ている地面の電位を検出する。In FIG. 10, the M-sequence signal from the M-sequence signal generator 10 is amplified by the power amplifier 3 and applied as a voltage between the buried steel pipe 1 and the ground electrode 4. In this state, the probe 6 is moved on the ground surface along the pipe axis direction of the buried steel pipe. The probe 6 is provided with a pair of wheel electrodes 6a and 6b in the front-rear direction thereof, and detects the potential of the ground with which they are in contact.
【００１８】これらの電位の差をとり、図示されていな
いＡ／Ｄ変換器でディジタル値に変換した後、パーソナ
ルコンピュータ演算部１３に取り込む。パーソナルコン
ピュータ演算部１３には、Ｍ系列参照信号発生器１１が
設けられている。このＭ系列参照信号発生器１１は、Ｍ
系列信号発生器１０とは電気的に独立しているが、同じ
パルスパターンのＭ系列信号を発生するようにされてい
る。The difference between these potentials is taken, converted into a digital value by an A / D converter (not shown), and then taken into the personal computer arithmetic unit 13. The personal computer arithmetic unit 13 is provided with the M-sequence reference signal generator 11. This M-sequence reference signal generator 11 is
Although it is electrically independent of the sequence signal generator 10, it is configured to generate an M sequence signal having the same pulse pattern.
【００１９】パーソナルコンピュータ演算部１３中の相
関処理部１２は、このＭ系列参照信号発生器１１よりの
参照信号と、Ａ／Ｄ変換された車輪電極６ａ、６ｂ間の
電位差信号（検出信号）との相互相関演算を行う。相互
相関演算結果は、参照信号と同じ周期のピーク値を有す
る。図１３に相互相関演算結果の一例を示す。このピー
ク値を検出して検出信号の代表値とすることにより、ノ
イズ信号を抑制した高精度の電位差検出ができる。The correlation processing unit 12 in the personal computer arithmetic unit 13 receives the reference signal from the M-series reference signal generator 11 and the potential difference signal (detection signal) between the A / D converted wheel electrodes 6a and 6b. Cross-correlation calculation is performed. The cross-correlation calculation result has a peak value with the same period as the reference signal. FIG. 13 shows an example of the cross-correlation calculation result. By detecting this peak value and using it as the representative value of the detection signal, it is possible to detect the potential difference with high accuracy while suppressing the noise signal.
【００２０】埋設鋼管１の塗膜に塗膜損傷部５がある場
合には、印加電圧に応じて塗膜損傷部５より電流が流入
し、付近の土壌中に電位勾配を作る。この電位勾配の方
向は、塗膜損傷部５の真上の位置を境にして逆転する。
よって、探査機６の埋設鋼管の管軸方向に沿って走行さ
せ、走行距離を横軸に、車輪電極６ａ，６ｂの間の電位
差の代表値を縦軸にとってグラフを作ると、塗膜損傷部
５の真上でＳ字型のカーブを描く。よって、このＳ字型
のカーブの中央の位置を検出することにより、塗膜損傷
部５の位置を地上から非接触で検出することができる。When the coating film of the buried steel pipe 1 has a coating film damaged portion 5, a current flows from the coating film damaged portion 5 in accordance with the applied voltage, and a potential gradient is created in the nearby soil. The direction of this potential gradient is reversed at the position directly above the coating film damaged portion 5 as a boundary.
Therefore, when a graph is made by traveling along the pipe axis direction of the buried steel pipe of the explorer 6 and plotting the traveling distance on the horizontal axis and the representative value of the potential difference between the wheel electrodes 6a, 6b on the vertical axis, Draw an S-shaped curve just above 5. Therefore, by detecting the center position of this S-shaped curve, the position of the coating film damaged portion 5 can be detected from the ground in a non-contact manner.
【００２１】図１４に、上記方法による相互相関ピーク
値（電位差の代表値）と探査機の移動距離（検査位置）
との関係を示す。対象とした埋設鋼管は、管径１００
Ａ、管長１０ｍのＰＬＰ導管であり、約１ｍの深さに埋
設されたものである。塗膜損傷サイズは、５ｍｍ×４ｍ
ｍのものであった。探査機の車輪電極の間隔は１ｍであ
った。埋設鋼管の流入電流は１ｍＡ（４４０Ｈｚ）であ
り、前記電位差法の条件の１／１０であるにもかかわら
ず、電位差の代表値はきれいなＳ字型カーブを呈してお
り、このＳ字型カーブのゼロクロス位置より、塗膜損傷
位置を知ることができる。FIG. 14 shows the cross-correlation peak value (representative value of potential difference) and the moving distance (inspection position) of the spacecraft by the above method.
Shows the relationship with. The target buried steel pipe has a pipe diameter of 100.
A, a PLP conduit having a pipe length of 10 m, which is buried at a depth of about 1 m. Coating damage size is 5mm x 4m
It was m. The space between the wheel electrodes of the spacecraft was 1 m. The inflow current of the buried steel pipe is 1 mA (440 Hz), and although it is 1/10 of the condition of the potentiometric method, the representative value of the potential difference shows a clean S-shaped curve. The position of coating film damage can be known from the zero-cross position.
【００２２】[0022]
【発明が解決しようとする課題】このように、本発明者
らの発明になる、ランダム信号または擬似ランダム信号
を用い、信号処理として相関処理を用いる方法によれ
ば、従来の電位差法に比して極めて精度良く塗膜損傷位
置を検出できる。As described above, according to the method of the present invention, which uses the random signal or the pseudo-random signal and uses the correlation processing as the signal processing, as compared with the conventional potential difference method. The position of coating film damage can be detected extremely accurately.
【００２３】しかしながら、前記実施の形態で例として
示した方法には、以下のような問題点があった。すなわ
ち、埋設鋼管に給電する擬似ランダム信号は矩形波であ
り、直流成分を有しているため、直流成分の減衰する系
における電位測定には不向きである。しかるに、地中の
電位伝播特性においては、直流成分が著しく減衰する。
よって、電位差測定に基づいている前記実施の形態の方
法において大きな誤差の要因となる。However, the method shown as an example in the above embodiment has the following problems. That is, since the pseudo-random signal feeding the buried steel pipe is a rectangular wave and has a DC component, it is not suitable for potential measurement in a system in which the DC component is attenuated. However, in the potential propagation characteristics in the ground, the DC component is significantly attenuated.
Therefore, it causes a large error in the method of the above embodiment based on the potential difference measurement.
【００２４】図１５に前記実施の形態における実際の印
加電圧波形と車輪電極間の検出電圧波形を示す。対象と
した埋設鋼管は、管径１００Ａ、管長１０ｍのＰＬＰ導
管であり、約１ｍの深さに埋設されたものである。塗膜
損傷サイズは、５ｍｍ×４ｍｍのものであった。探査機
の車輪電極の間隔は１ｍであった。埋設鋼管の流入電流
は１ｍＡ（４４０Ｈｚ）であった。印加電圧の直流成分
は、検出電圧では時定数ＣＲ＝約２ｍｓで指数減衰して
いる。よって、前記実施の形態の方法では、従来の電位
差法に比してはＳ／Ｎ比が大幅に向上するものの、これ
が更なるＳ／Ｎ比の向上をはばんでいる。FIG. 15 shows the actual applied voltage waveform and the detected voltage waveform between the wheel electrodes in the above embodiment. The target buried steel pipe is a PLP pipe having a pipe diameter of 100 A and a pipe length of 10 m, and is buried at a depth of about 1 m. The coating damage size was 5 mm x 4 mm. The space between the wheel electrodes of the spacecraft was 1 m. The inflow current of the buried steel pipe was 1 mA (440 Hz). The DC component of the applied voltage is exponentially attenuated at the detection voltage with a time constant CR = about 2 ms. Therefore, in the method of the above-described embodiment, the S / N ratio is significantly improved as compared with the conventional potential difference method, but this further prevents the S / N ratio from being further improved.
【００２５】さらに、一般には、相互相関演算処理は時
間領域演算により行われているが、時間領域演算では相
関処理を行う２信号をそれぞれサンプリングして、掛け
合わせた後に、片方の信号を１サンプリング幅ずらしな
がら、ピークを探していくという逐次処理が必要なた
め、相互相関演算処理に時間がかかるという問題点があ
る。Further, generally, the cross-correlation calculation process is performed by the time domain calculation. In the time domain calculation, two signals to be subjected to the correlation process are sampled and multiplied, and then one signal is sampled once. Since it is necessary to sequentially search for peaks while shifting the width, there is a problem that the cross-correlation calculation process takes time.
【００２６】本発明は、このような問題点を解決するた
めになされたもので、前記実施の形態に示した方法より
も信号のＳ／Ｎ比を向上させ、塗膜損傷位置を精度良
く、確実に、さらに高速に検出する方法、およびこの方
法を実施するのに好適な装置を提供することを課題とす
る。The present invention has been made in order to solve such a problem, and improves the S / N ratio of a signal as compared with the method shown in the above-mentioned embodiment, and the position of coating film damage can be accurately measured. An object of the present invention is to provide a method for surely detecting even faster, and an apparatus suitable for carrying out this method.
【００２７】[0027]
【課題を解決するための手段】本発明の骨子は、埋設鋼
管に印加する交流電圧にランダム信号または擬似ランダ
ム信号を使用し、相互相関処理を行うことによりノイズ
を除去してＳ／Ｎ費を改善する特願平９−５７１０２号
の発明において、搬送波の位相を変調することによって
生成したランダム信号または擬似ランダム信号を用いる
こと、さらに前記相互相関処理を、参照信号と検出信号
それぞれにフーリエ変換を行って、そのスペクトルの共
役積の逆フーリエ変換を行うことにより実施することに
ある。The skeleton of the present invention uses a random signal or a pseudo-random signal as an AC voltage applied to an embedded steel pipe, and performs cross-correlation processing to remove noise and reduce S / N cost. In the invention of Japanese Patent Application No. 9-57102 to be improved, a random signal or a pseudo-random signal generated by modulating the phase of a carrier wave is used.
It, the cross-correlation processing further, performs Fourier transform to each reference signal and the detection signal is to carried out by performing an inverse Fourier transform of the conjugate product of the spectrum.
【００２８】すなわち、前記課題を解決するための第１
の手段は、埋設鋼管と大地の間に交流電圧を印加するこ
とにより当該埋設鋼管に交流電流を流し、管軸方向に沿
った位置にある２点間の電位差を当該２点を移動させな
がら順次検出することにより、前記交流電流により地上
に発生する電位分布を測定し、その電位分布の変化から
当該埋設鋼管の塗膜損傷位置を検知する方法において、
搬送波の位相を変調させることによって生成したランダ
ム信号又は擬似ランダム信号を、埋設鋼管に印加する信
号として用い、前記埋設鋼管に印加する交流電圧信号か
ら取りだした参照信号と、前記２点間の電位差の検出信
号それぞれにフーリエ変換を行って、そのスペクトルの
共役積の逆フーリエ変換を行うことにより、前記２信号
の相関処理を行い、そのピーク値を前記２点間の電位差
の代表値とし、当該代表値より電位分布を求め、求めた
電位分布の変化から当該埋設管の塗膜損傷位置を検出す
ることを特徴とする埋設鋼管の塗膜損傷位置検出方法
（請求項１）である。That is, the first means for solving the above problems
Means applies an AC voltage between the buried steel pipe and the ground to cause an AC current to flow through the buried steel pipe, and the potential difference between two points along the pipe axis direction is sequentially moved while moving the two points. By detecting, measuring the potential distribution generated on the ground by the alternating current, in the method of detecting the coating film damage position of the buried steel pipe from the change in the potential distribution,
A random signal or a pseudo-random signal generated by modulating the phase of the carrier wave is used as a signal to be applied to the embedded steel pipe, and a reference signal extracted from an AC voltage signal applied to the embedded steel pipe and the potential difference between the two points. By performing a Fourier transform on each of the detection signals and performing an inverse Fourier transform of the conjugate product of the spectrum, the correlation processing of the two signals is performed, and the peak value is set as the representative value of the potential difference between the two points, and the representative A method for detecting a coating film damage position of an embedded steel pipe, wherein a potential distribution is obtained from the value and the coating film damage position of the buried pipe is detected from the obtained change in the potential distribution.
【００２９】ここに擬似ランダム信号とは、長期間にお
いては繰り返し周期がありランダム性は失われるが、周
期内においてはランダム性が保たれるような信号をい
う。Here, the pseudo-random signal is a signal that has a repeating period for a long period of time and loses randomness, but keeps randomness within the period.
【００３０】印加電圧の波形と検出信号の波形の相互相
関をとった場合、その相互相関の計算中、たとえば検出
信号をシフトして掛け算を行う過程において、印加電圧
とシフトされた検出信号が同じパターンとなって同期の
とれた位置に相互相関のピークが現れる。印加電圧とパ
ターンの異なるノイズは、相互相関をとることによって
打ち消されてしまい、ピーク値にはほとんど影響を与え
ない。印加電圧はランダム信号または擬似ランダム信号
であるので、印加電圧に基づかないノイズが印加電圧の
パターンと同じパターンになることはない。When the waveform of the applied voltage and the waveform of the detection signal are cross-correlated, the applied voltage and the shifted detection signal are the same during the calculation of the cross-correlation, for example, in the process of shifting and multiplying the detection signal. A peak of cross-correlation appears at a synchronized position as a pattern. The noise having a different pattern from the applied voltage is canceled by taking the cross-correlation and has almost no effect on the peak value. Since the applied voltage is a random signal or a pseudo random signal, noise that is not based on the applied voltage does not have the same pattern as the applied voltage pattern.
【００３１】よって、この第１の手段によれば、印加電
圧に起因する検出信号のみが車輪電極間の電位差の代表
値として検出されることになるので、Ｓ／Ｎ比が大きく
改善される。この代表値を用いて電位分布を求め、その
電位分布の変化から前記従来の方法と同じ方法で塗膜損
傷位置を検出することにすれば、塗膜損傷位置を精度良
く、確実に検出できる。Therefore, according to the first means, only the detection signal resulting from the applied voltage is detected as the representative value of the potential difference between the wheel electrodes, so that the S / N ratio is greatly improved. If the potential distribution is obtained using this representative value and the coating film damage position is detected from the change in the potential distribution by the same method as the conventional method, the coating film damage position can be detected accurately and reliably.
【００３２】この第１の手段においては、ランダム信号
または擬似ランダム信号は、搬送波を位相変調すること
によって生成されている。よって、搬送波として直流分
を含まないか直流分が少ない信号を用いれば、埋設鋼管
に印加されるランダム信号または擬似ランダム信号も直
流分を含まないか直流分が少ない信号となる。従って、
地中における信号の減衰が少ないので、印加した電圧と
相似の検出信号が得られることになり、信号処理後のＳ
／Ｎ比が向上する。In the first means, the random signal or the pseudo random signal is generated by phase-modulating the carrier wave. Therefore, if a signal containing no DC component or a small DC component is used as the carrier wave, the random signal or the pseudo-random signal applied to the buried steel pipe also becomes a signal containing no DC component or a small DC component. Therefore,
Since the signal attenuation in the ground is small, a detection signal similar to the applied voltage can be obtained.
The / N ratio is improved.
【００３３】さらに、この第１の手段においては、埋設
鋼管に印加する交流電圧信号から取りだした参照信号
と、２点間の電位差の検出信号それぞれにフーリエ変換
を行って、そのスペクトルの共役積の逆フーリエ変換を
行うことにより、前記２信号の相関処理を行い、そのピ
ーク値を前記２点間の電位差の代表値としている。すな
わち、信号発生器の出力信号と電圧測定器の出力信号そ
れぞれにフーリエ変換を行って得られた２つのスペクト
ルの内、一方は原スペクトルのままで、他方のスペクト
ルの複素共役をとり、両スペクトルの畳み込み積分を行
った後に逆フーリエ変換を行うことによって、前記２信
号の相互相関を演算している。Further, in the first means, the Fourier transform is applied to each of the reference signal extracted from the AC voltage signal applied to the buried steel pipe and the detection signal of the potential difference between the two points, and the conjugate product of the spectrum is calculated. By performing an inverse Fourier transform, the correlation processing of the two signals is performed, and the peak value thereof is used as the representative value of the potential difference between the two points. That is, of the two spectra obtained by performing the Fourier transform on each of the output signal of the signal generator and the output signal of the voltage measuring device, one remains the original spectrum and the complex conjugate of the other spectrum is taken to obtain both spectra. The cross-correlation between the two signals is calculated by performing the inverse Fourier transform after performing the convolution integration of.
【００３４】つまり、第１の手段は、相関処理演算を行
う際に、従来の時間領域の演算でなく、フーリエ変換、
畳み込み積分、逆フーリエ変換といった周波数領域での
演算を特徴としている。時間領域演算では相関処理を行
う２信号をそれぞれサンプリングして、掛け合わせた後
に、片方の信号を１サンプリング幅ずらしながら、ピー
クを探していくという逐次処理が必要であるが、第１の
手段で採用している周波数領域演算では、逐次処理が生
じないため、大幅な演算時間の短縮が図れ、処理効率が
向上する。なお、フーリエ変換を用いて相互相関処理す
る方式は公知である。（オーム社 稲葉博 他 「現代
制御工学概論」 1980 他多数）That is, the first means, when performing the correlation processing operation, is not the conventional time domain operation but Fourier transform,
It features arithmetic operations in the frequency domain such as convolutional integration and inverse Fourier transform. In the time domain calculation, it is necessary to perform sequential processing in which two signals to be subjected to correlation processing are sampled and multiplied, and then one signal is shifted by one sampling width to search for a peak. Since the frequency domain calculation adopted does not cause sequential processing, the calculation time can be greatly shortened and the processing efficiency can be improved. A method of performing cross-correlation processing using Fourier transform is known. (OHM, Hiroshi Inaba et al. "Introduction to modern control engineering" 1980 and many others)
【００３５】前記課題を解決するための第２の手段は、
埋設鋼管と大地の間に交流電圧を印加することにより当
該埋設鋼管に交流電流を流し、管軸方向に沿った位置に
ある２点間の電位差を当該２点を移動させながら順次検
出することにより、前記交流電流により地上に発生する
電位分布を測定し、その電位分布の変化から当該埋設鋼
管の塗膜損傷位置を検知する方法において、搬送波の位
相を変調させることによって生成した擬似ランダム信号
を、埋設鋼管に印加する信号として用い、埋設鋼管に印
加する交流電圧とは独立に生成された、当該交流電圧と
同じパターンの参照信号と、前記２点間の電位差の検出
信号それぞれにフーリエ変換を行って、そのスペクトル
の共役積の逆フーリエ変換を行うことにより、前記２信
号の相関処理を行い、そのピーク値を前記２点間の電位
差の代表値とし、当該代表値より電位分布を求め、求め
た電位分布の変化から当該埋設管の塗膜損傷位置を検出
することを特徴とする埋設鋼管の塗膜損傷位置検出方法
（請求項２）である。The second means for solving the above-mentioned problems is as follows.
By applying an AC voltage between the buried steel pipe and the ground, an AC current is made to flow through the buried steel pipe, and the potential difference between the two points along the pipe axis direction is detected sequentially while moving the two points. , Measuring the potential distribution generated on the ground by the alternating current, in the method of detecting the coating film damage position of the buried steel pipe from the change in the potential distribution, a pseudo-random signal generated by modulating the phase of the carrier , Fourier transform is performed on each of the reference signal having the same pattern as the AC voltage generated independently of the AC voltage applied to the embedded steel pipe and the detection signal of the potential difference between the two points, which is used as a signal applied to the embedded steel pipe. Then, the inverse Fourier transform of the conjugate product of the spectrum is performed to perform the correlation processing of the two signals, and the peak value thereof is used as the representative value of the potential difference between the two points, Calculated potential distribution than the representative value, a coating damage position detecting method embedded steel pipe and detects the coating damage location of the buried pipe from a change in the determined potential distribution (claim 2).
【００３６】第２の手段と前記第１の手段との違いは、
第２の手段においては、埋設管に印加する交流電圧信号
を擬似ランダム信号に特定すると共に、参照信号とし
て、埋設鋼管に印加する交流電圧とは独立に生成され
た、当該交流電圧と同じパターンの信号を用いているこ
とである。この場合、パターンが同じということは、繰
り返し周波数も一致していることを意味する。The difference between the second means and the first means is that
In the second means, the AC voltage signal applied to the buried pipe is specified as a pseudo-random signal, and the reference voltage has the same pattern as the AC voltage generated independently of the AC voltage applied to the buried steel pipe. It is using the signal. In this case, the fact that the patterns are the same means that the repetition frequencies are also the same.
【００３７】印加電圧波形に擬似ランダム信号を用いる
場合には、参照信号として、埋設鋼管に印加する交流電
圧とは独立に生成された、当該交流電圧と同じパターン
の信号を用いることができる。When a pseudo random signal is used for the applied voltage waveform, a signal having the same pattern as the AC voltage generated independently of the AC voltage applied to the buried steel pipe can be used as the reference signal.
【００３８】すなわち、擬似ランダム信号は繰り返し周
期を有するので、検出信号をシフトさせれば、必ずある
シフト量において参照信号とシフトされた検出信号の同
期がとれる。よって、周期に対応する有限の期間に亘っ
て相互相関をとれば、同期がとれるシフト量の位置で相
互相関信号にピークが現れることが保証される。従っ
て、交流電圧と参照信号の同期をとる必要が無いので、
通電装置と検出装置を独立のものとすることができ、装
置の簡略化ができる。That is, since the pseudo random signal has a repeating period, if the detection signal is shifted, the reference signal and the shifted detection signal can be synchronized with each other with a certain shift amount. Therefore, if the cross-correlation is performed over a finite period corresponding to the cycle, it is guaranteed that a peak appears in the cross-correlation signal at the position of the shift amount that can be synchronized. Therefore, it is not necessary to synchronize the AC voltage with the reference signal.
The energization device and the detection device can be independent, and the device can be simplified.
【００３９】前記課題を解決するための第３の手段は、
搬送波の位相を変調することによって生成したランダム
信号または擬似ランダム信号を発生する信号発生器と、
信号発生器の出力に比例した電圧を発生し、埋設鋼管と
大地の間に通電する電力増幅器と、地表面を埋設鋼管の
管軸方向に沿って走行し、埋設鋼管の管軸方向に隔離し
て配置された複数の車輪電極を有する探査機と、前記複
数の車輪電極の間の電位差を測定する電圧測定器と、前
記信号発生器から取り出した参照信号と前記電圧測定器
の出力信号それぞれにフーリエ変換を行って、そのスペ
クトルの共役積の逆フーリエ変換を行うことにより、前
記２信号の相関処理を演算しそのピーク値を出力する相
関処理装置と、当該相関処理装置の出力の変化から当該
埋設鋼管の塗膜損傷位置を検出する手段とを有してなる
埋設鋼管の塗膜損傷位置検出装置（請求項３）である。The third means for solving the above-mentioned problems is as follows.
A signal generator that generates a random signal or a pseudo-random signal generated by modulating the phase of a carrier wave ,
A power amplifier that generates a voltage proportional to the output of the signal generator and energizes between the buried steel pipe and the ground, and runs on the ground surface along the pipe axis direction of the buried steel pipe to isolate it in the pipe axis direction of the buried steel pipe. And a probe having a plurality of wheel electrodes arranged as a voltage measuring device for measuring a potential difference between the plurality of wheel electrodes, a reference signal taken out from the signal generator and an output signal of the voltage measuring device, respectively. By performing a Fourier transform and performing an inverse Fourier transform of the conjugate product of the spectrum, the correlation processing apparatus that calculates the correlation processing of the two signals and outputs the peak value thereof, and the change of the output of the correlation processing apparatus A coating film damage position detection device for an embedded steel pipe, comprising: means for detecting a coating film damage position of the embedded steel pipe (claim 3).
【００４０】この装置は、前記第１の手段に係る方法を
実現するのに好適である。すなわち、信号発生器より発
生したランダム信号または擬似ランダム信号を、電力増
幅器により増幅して、埋設鋼管と大地の間に通電する。
塗膜損傷があると損傷部に電流が流入し、その結果、大
地表面に電位勾配が発生する。探査機を埋設鋼管に沿っ
て地上を走行させ、車輪電極間の電圧を検出することに
より、この電位勾配を測定する。そして、相関処理装置
により、信号発生器から取出した参照信号（前記ランダ
ム信号または擬似ランダム信号と同一パターンの信号）
と、検出された車輪電極間の電圧との相互相関を演算
し、そのピーク値を求める。そして、相関処理装置の出
力であるこのピーク値の変化から埋設鋼管の塗膜損傷位
置を検出する。This device is suitable for realizing the method according to the first means. That is, a random signal or a pseudo-random signal generated by a signal generator is amplified by a power amplifier, and electricity is applied between the buried steel pipe and the ground.
When the coating film is damaged, an electric current flows into the damaged part, and as a result, a potential gradient is generated on the ground surface. This potential gradient is measured by running a probe along the buried steel pipe on the ground and detecting the voltage between the wheel electrodes. Then, the reference signal taken out from the signal generator by the correlation processing device (a signal having the same pattern as the random signal or the pseudo random signal)
And a cross-correlation with the detected voltage between the wheel electrodes are calculated, and the peak value is obtained. Then, the coating film damage position of the buried steel pipe is detected from the change of the peak value which is the output of the correlation processing device.
【００４１】相関処理は、信号発生器から取り出した参
照信号と前記電圧測定器の出力信号それぞれにフーリエ
変換を行って、そのスペクトルの共役積の逆フーリエ変
換を行うことにより行う。すなわち、相関処理演算を行
う際に、従来の時間領域の演算でなく、フーリエ変換、
畳み込み積分、逆フーリエ変換といった周波数領域での
演算を特徴としている。前にも説明したように、時間領
域演算では相関処理を行う２信号をそれぞれサンプリン
グして、掛け合わせた後に、片方の信号を１サンプリン
グ幅ずらしながら、ピークを探していくという逐次処理
が必要であるが、第３の手段で採用している周波数領域
演算では、逐次処理が生じないため、大幅な演算時間の
短縮が図れ、処理効率が向上する。Correlation processing is performed by performing a Fourier transform on each of the reference signal extracted from the signal generator and the output signal of the voltage measuring device, and performing the inverse Fourier transform of the conjugate product of the spectrum. That is, when performing the correlation calculation, the Fourier transform, instead of the conventional time domain calculation,
It features arithmetic operations in the frequency domain such as convolutional integration and inverse Fourier transform. As described above, in the time domain calculation, it is necessary to perform sequential processing in which two signals to be subjected to correlation processing are sampled and multiplied, and then one signal is shifted by one sampling width to search for a peak. However, in the frequency domain calculation adopted in the third means, sequential processing does not occur, so that the calculation time can be greatly shortened and the processing efficiency is improved.
【００４２】この相関処理装置の出力の変化から埋設鋼
管の塗膜損傷位置を検出する手段は、従来技術のものと
変わることが無く、公知のものが使用できる。例えば、
電位差がゼロクロスする点を検出する回路による方法、
正の電位差が最大を示す点と負の電位差が最大値を示す
点との中点を検出する回路等を、適宜選択して使用すれ
ばよい。The means for detecting the coating film damage position of the buried steel pipe from the change in the output of the correlation processing device is the same as that of the prior art, and any known means can be used. For example,
Method by a circuit that detects the point where the potential difference crosses zero,
A circuit or the like for detecting the midpoint between the point where the positive potential difference is maximum and the point where the negative potential difference is maximum may be appropriately selected and used.
【００４３】前記課題を解決するための第４の手段は、
搬送波の位相を変調することによって生成した擬似ラン
ダム信号を発生する第１の信号発生器と、第１の信号発
生器の出力に比例した電圧を発生し、埋設鋼管と大地の
間に通電する電力増幅器と、地表面を埋設鋼管の管軸方
向に沿って走行し、埋設鋼管の管軸方向に隔離して配置
された複数の車輪を有する探査機と、前記複数の車輪電
極の間の電位差を測定する電圧測定器と、第１の信号発
生器と同じパターンの波形を出力する第２の信号発生器
と、第２の信号発生器の出力信号と前記電圧測定器の出
力信号それぞれにフーリエ変換を行って、そのスペクト
ルの共役積の逆フーリエ変換を行うことによって、前記
２信号の相関処理を演算しそのピーク値を出力する相関
処理装置と、当該相関処理装置の出力の変化から当該埋
設鋼管の塗膜損傷位置を検出する手段とを有してなる埋
設鋼管の塗膜損傷位置検出装置（請求項４）である。The fourth means for solving the above-mentioned problems is as follows.
A first signal generator that generates a pseudo-random signal generated by modulating the phase of a carrier wave , and a power that generates a voltage proportional to the output of the first signal generator and that is applied between the buried steel pipe and the ground. An amplifier, a ground plane running along the pipe axis direction of the buried steel pipe, and a probe having a plurality of wheels arranged separately in the pipe axis direction of the buried steel pipe, and a potential difference between the plurality of wheel electrodes. A voltage measuring device to be measured, a second signal generator that outputs a waveform having the same pattern as that of the first signal generator, an output signal of the second signal generator, and a Fourier transform to the output signal of the voltage measuring device. By performing the inverse Fourier transform of the conjugate product of the spectrum, the correlation processing apparatus that calculates the correlation processing of the two signals and outputs the peak value, and the buried steel pipe from the change in the output of the correlation processing apparatus. Coating damage A coating damage position detecting device embedded steel pipe comprising a means for detecting the location (claim 4).
【００４４】この装置は、前記第２の手段に係る方法を
実現するのに好適である。この装置においては、相関処
理装置に使用される参照信号が、第１の信号発生器から
のものではなく、これと同じパターンの擬似ランダム信
号を発生する第２の信号発生器からのものである点のみ
が前述の第３の手段と異なっている。前述したように、
擬似ランダム信号を用いる場合には、参照信号は、埋設
鋼管と大地の間に印加された電圧波形に同期している必
要はなく、パターンさえ同じであれば、前記第３の手段
と同じ作用効果が得られる。This device is suitable for realizing the method according to the second means. In this device, the reference signal used in the correlation processing device is not from the first signal generator but from the second signal generator which generates a pseudo-random signal of the same pattern. Only the points differ from the above-mentioned third means. As previously mentioned,
When the pseudo random signal is used, the reference signal does not have to be synchronized with the voltage waveform applied between the buried steel pipe and the ground, and if the pattern is the same, the same effect as the third means is obtained. Is obtained.
【００４５】[0045]
【発明の実施の形態】以下、本発明の実施の形態を図を
用いて説明する。図１は、本発明の実施の形態の例を示
す図である。図１において、１は埋設鋼管、３は電力増
幅器、４は接地電極、５は埋設鋼管１の塗膜損傷部、６
は探査機、６ａ、６ｂは探査機の車輪電極、１０はＭ系
列信号発生器、１１はＭ系列参照信号発生器、１３はパ
ーソナルコンピュータ演算部、１４は正弦波発生器、１
５は掛算器、１６はＦＦＴ処理部、１７は複素共役処理
部、１８は畳み込み積分処理部、１９は逆ＦＦＴ処理部
である。BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of an embodiment of the present invention. In FIG. 1, 1 is a buried steel pipe, 3 is a power amplifier, 4 is a ground electrode, 5 is a coating film damaged portion of the buried steel pipe 1, 6
Is a probe, 6a and 6b are wheel electrodes of the probe, 10 is an M-sequence signal generator, 11 is an M-sequence reference signal generator, 13 is a personal computer arithmetic unit, 14 is a sine wave generator, 1
Reference numeral 5 is a multiplier, 16 is an FFT processing unit, 17 is a complex conjugate processing unit, 18 is a convolution integration processing unit, and 19 is an inverse FFT processing unit.
【００４６】本実施の形態においては、埋設鋼管１に印
加する信号として、正弦波発生器１４とその正弦波に同
期したＭ系列信号発生器１０で生成された２値のＭ系列
信号を掛算器３で掛け合わせることによって、Ｍ系列パ
ターンになった二位相変調された正弦波信号を生成し、
これを埋設鋼管１に印加する信号として用いる。In this embodiment, as the signal applied to the buried steel pipe 1, the binary M-sequence signal generated by the sine-wave generator 14 and the M-sequence signal generator 10 synchronized with the sine-wave is multiplied. Multiplying by 3 produces a bi-phase modulated sine wave signal in the M-sequence pattern,
This is used as a signal applied to the buried steel pipe 1.
【００４７】従来技術で述べたＭ系列信号（Ｍ系列原信
号と呼ぶ）と、ここで用いる正弦波位相変調型Ｍ系列信
号（Ｍ系列変調信号と呼ぶ）の比較を以下に示す。A comparison between the M-sequence signal (referred to as M-sequence original signal) described in the prior art and the sine wave phase modulation type M-sequence signal (referred to as M-sequence modulated signal) used here will be shown below.
【００４８】正弦波位相変調に関しては、搬送波の位相
を切り替えることによって情報を伝送する一方式とし
て、ＰＳＫ（Phase shift keying）として公知である。The sine wave phase modulation is known as PSK (Phase shift keying) as one method of transmitting information by switching the phase of a carrier wave.
【００４９】たとえば、図２に示すように、搬送波（こ
こでは正弦波）に情報波形（ここではベースバンド波
形）を掛け合わせることによって、搬送波の位相変調を
起こす。そのとき生成されたＰＳＫ波形を図２（ｂ）に
示す。（電気大出版局 山内雪路著 スペクトラム拡散通
信1994出典）For example, as shown in FIG. 2, a carrier wave (here, a sine wave) is multiplied by an information waveform (here, a baseband waveform) to cause phase modulation of the carrier wave. The PSK waveform generated at that time is shown in FIG. (Yukiji Yamauchi, Denki Univ., Spread Spectrum Communications 1994)
【００５０】図３に、Ｍ系列原信号とＭ系列変調信号を
示す。図４に両信号の周波数スペクトラムを示す。図３
（ａ）はＭ系列原信号であり、ＨレベルとＬレベルの２
値信号である。Ｈレベルを１に、Ｌレベルを−１に対応
させている。このＭ系列原信号を搬送波である正弦波信
号に掛け合わせることによって、図３（ｂ）に示すよう
なＭ系列変調信号が得られる。Ｍ系列変調信号は、Ｍ系
列原信号が１の値をとるとき、搬送波に対して同位相で
あり、Ｍ系列原信号が−１の値をとるとき、搬送波に対
して位相がπだけずれた信号となる。FIG. 3 shows an M-series original signal and an M-series modulated signal. Figure 4 shows the frequency spectrum of both signals. Figure 3
(A) is an M-series original signal, which has 2 levels of H level and L level.
It is a value signal. The H level corresponds to 1 and the L level corresponds to -1. By multiplying this M-series original signal by a sine wave signal which is a carrier wave, an M-series modulated signal as shown in FIG. 3B is obtained. The M-sequence modulated signal is in phase with the carrier when the M-series original signal has a value of 1, and is out of phase with the carrier by π when the M-series original signal has a value of -1. Become a signal.
【００５１】Ｍ系列変調信号のパワースペクトラムにお
いては、図４（ｂ）に示されるように、Ｍ系列原信号の
主要成分である直流および低周波成分はクロック周波数
の分だけ高周波側にシフトし、信号が各クロック毎のモ
ノサイクルパルスで構成されるために、直流成分がなく
なる。よって、地中における直流成分の減衰の影響を受
けなくなり、地中の伝播特性と整合した波形となる。図
４（ｂ）に示されるように、Ｍ系列変調信号の周波数の
主成分は、クロック周波数と等しい。In the power spectrum of the M-sequence modulated signal, as shown in FIG. 4 (b), the DC and low frequency components, which are the main components of the M-series original signal, shift to the high frequency side by the clock frequency, Since the signal is composed of monocycle pulses for each clock, there is no DC component. Therefore, the influence of the attenuation of the direct current component in the ground is eliminated, and the waveform matches the propagation characteristics in the ground. As shown in FIG. 4B, the main component of the frequency of the M-sequence modulated signal is equal to the clock frequency.
【００５２】Ｍ系列原信号とＭ系列変調信号の自己相関
関数を図５に示す。後者は、前者の自己相関関数にcos
(2πfct)を乗じた関数となる。なお、図５において、ｆ
cはＭ系列信号の周波数、ＮはＭ系列信号１周期分の符
号長である。（たとえば、Ｍ系列信号を発生するシフト
レジスタの段数がｎ段のとき、Ｎ＝２n−１）図１にお
いて、正弦波発生器１４とその正弦波に同期したＭ系列
信号発生器１０で生成されたＭ系列信号（Ｍ系列原信
号）を掛算器３で掛け合わせることによって、Ｍ系列パ
ターンとなり二位相変調された正弦波信号（Ｍ系列変調
信号）は、電力増幅器３で増幅されて、埋設鋼管１と接
地電極４の間に電圧として印加される。この状態で探査
機６を、埋設鋼管の管軸方向に沿って地表面上を移動さ
せる。探査機６には、その前後方向に１対の車輪電極６
ａ、６ｂが設けられており、それぞれが接触している地
面の電位を検出する。FIG. 5 shows the autocorrelation function of the M-series original signal and the M-series modulated signal. The latter has cos in the former autocorrelation function.
It is a function multiplied by (2πfct). In FIG. 5, f
c is the frequency of the M-sequence signal, and N is the code length for one cycle of the M-sequence signal. (For example, when the number of stages of the shift register that generates the M-sequence signal is n, N = 2 n -1) In FIG. 1, the sine wave generator 14 and the M-sequence signal generator 10 synchronized with the sine wave generate the signal. The sine wave signal (M-sequence modulated signal) that has become a M-sequence pattern and is bi-phase modulated by multiplying the generated M-sequence signal (M-sequence original signal) by the multiplier 3 is amplified by the power amplifier 3 and embedded. A voltage is applied between the steel pipe 1 and the ground electrode 4. In this state, the probe 6 is moved on the ground surface along the pipe axis direction of the buried steel pipe. The probe 6 includes a pair of wheel electrodes 6 in the front-rear direction.
a and 6b are provided to detect the potential of the ground with which they are in contact.
【００５３】これらの電位の差をとり、図示されていな
いＡ／Ｄ変換器でディジタル値に変換された後、パーソ
ナルコンピュータ演算部１３に取り込む。パーソナルコ
ンピュータ演算部１３には、Ｍ系列参照信号発生器１１
が設けられている。このＭ系列参照信号発生器１１は、
Ｍ系列信号発生器１０とは電気的に独立しているが、同
じパルスパターン（周波数も同一）のＭ系列信号（Ｍ系
列原信号）と正弦波を掛け合わせることにより、掛算器
３から出力されるのと同じパターンのＭ系列変調信号を
発生するようになっている。同じパターンとは、信号の
形状及び周波数（周期）が一致しているものをいう。The difference between these potentials is taken, converted into a digital value by an A / D converter (not shown), and then taken into the personal computer arithmetic unit 13. The personal computer arithmetic unit 13 includes an M-sequence reference signal generator 11
Is provided. This M-sequence reference signal generator 11 is
Although it is electrically independent of the M-sequence signal generator 10, it is output from the multiplier 3 by multiplying the M-sequence signal (M-sequence original signal) having the same pulse pattern (same frequency) with a sine wave. The M-sequence modulated signal having the same pattern as that of the above-mentioned is generated. The same pattern means that the signal shapes and frequencies (cycles) are the same.
【００５４】パーソナルコンピュータ演算部１３中のＦ
ＦＴ処理部１６は、このＭ系列参照信号発生器１１より
の参照信号g(t)と、Ａ／Ｄ変換された車輪電極６ａ、６
ｂ間の電位差信号（検出信号）f(t)それぞれのフーリエ
変換演算を行い、それぞれＧ（ｉω）、Ｆ（ｉω）を得
る。Ｇ（ｉω）は複素共役処理部１７で複素共役演算さ
れ、Ｇ（ｉω）*が得られる。Ｆ（ｉω）とＧ（ｉω）*
は畳み込み積分処理部１８で畳み込み積分された後に逆
ＦＦＴ処理部１９で逆フーリエ変換される。以上の演算
処理により、f(t)とg(t)の相互相関が演算される。F in the personal computer arithmetic unit 13
The FT processing unit 16 receives the reference signal g (t) from the M-sequence reference signal generator 11 and the A / D converted wheel electrodes 6a, 6
The Fourier transform calculation of each potential difference signal (detection signal) f (t) between b is performed to obtain G (iω) and F (iω), respectively. G (iω) * is obtained by performing a complex conjugate operation on the complex conjugate processing unit 17 to obtain G (iω) * . F (iω) and G (iω) *
Is subjected to convolutional integration in the convolutional integration processing unit 18, and then subjected to inverse Fourier transform in the inverse FFT processing unit 19. Through the above calculation processing, the cross-correlation between f (t) and g (t) is calculated.
【００５５】検出信号f(t)にはＭ系列信号成分が含ま
れ、参照信号g(t)はこれと同じパターンのＭ系列信号で
あるので、相互相関演算結果は、参照信号と同じ周期の
ピーク値を有する。Since the detection signal f (t) contains an M-series signal component and the reference signal g (t) is an M-series signal having the same pattern as this, the cross-correlation calculation result shows that the cross-correlation calculation result has the same cycle as the reference signal. It has a peak value.
【００５６】図６に、相互相関演算結果の一例を示す。
図６においては、埋設鋼管１に印加する電圧および参照
信号にＭ系列原信号を使用したもの、すなわち図１０に
示した特願平９−５７１０２号に係る発明によるものを
（ａ）に、本発明によるもの、すなわち埋設鋼管１に印
加する電圧および参照信号にＭ系列変調信号を使用した
ものを（ｂ）に示す。図６において、横軸は相互相関演
算における畳み込み積分の時間差（相互相関演算におい
てｆ（ｔ）・ｇ（ｔ−τ）を変数ｔについて０からτま
で積分するときのτ）、縦軸はf(t)とg(t)の相互相関値
Φfg（τ）である。図６を見ると、Ｍ系列変調信号を使
用した本発明の場合の方が、Ｍ系列原信号を使用したも
のに比べてＳ／Ｎ比が向上しているのが分かる。FIG. 6 shows an example of the cross-correlation calculation result.
In FIG. 6, the M-series original signal is used for the voltage and the reference signal applied to the buried steel pipe 1, that is, the invention according to Japanese Patent Application No. 9-57102 shown in FIG. The one according to the invention, that is, the one using the M-sequence modulation signal for the voltage applied to the buried steel pipe 1 and the reference signal is shown in (b). In FIG. 6, the horizontal axis represents the time difference of convolutional integration in the cross-correlation calculation (τ when f (t) · g (t-τ) is integrated from 0 to τ for the variable t in the cross-correlation calculation), and the vertical axis represents f. It is the cross-correlation value Φ fg (τ) of (t) and g (t). It can be seen from FIG. 6 that the S / N ratio is improved in the case of the present invention using the M-sequence modulated signal as compared with the case using the M-sequence original signal.
【００５７】このピーク値を検出して検出信号の代表値
とすることにより、ノイズ信号を抑制した高精度の電位
差検出ができる。そして、この代表値を用いて処理を行
うことにより、塗膜損傷位置を高精度で確実に検出でき
る。By detecting this peak value and setting it as the representative value of the detection signal, it is possible to detect the potential difference with high accuracy while suppressing the noise signal. By performing processing using this representative value, the coating film damage position can be detected with high accuracy and reliability.
【００５８】埋設鋼管１の塗膜に塗膜損傷部５がある場
合には、印加電圧に応じて塗膜損傷部５より電流が流入
し、付近の土壌中に電位勾配を作る。この電位勾配の方
向は、塗膜損傷部５の真上の位置を境にして逆転する。
よって、探査機６の埋設鋼管の管軸方向に沿って走行さ
せ、走行距離を横軸に、車輪電極６ａ，６ｂの間の電位
差の代表値を縦軸にとってグラフを作ると、塗膜損傷部
５の真上でＳ字型のカーブを描く。よって、このＳ字型
のカーブの中央の位置を検出することにより、塗膜損傷
部５の位置を地上から非接触で検出することができる。When the coating film of the buried steel pipe 1 has a coating film damaged portion 5, a current flows from the coating film damaged portion 5 in accordance with the applied voltage, and a potential gradient is created in the soil nearby. The direction of this potential gradient is reversed at the position directly above the coating film damaged portion 5 as a boundary.
Therefore, when a graph is made by traveling along the pipe axis direction of the buried steel pipe of the explorer 6 and plotting the traveling distance on the horizontal axis and the representative value of the potential difference between the wheel electrodes 6a and 6b on the vertical axis, Draw an S-shaped curve just above 5. Therefore, by detecting the center position of this S-shaped curve, the position of the coating film damaged portion 5 can be detected from the ground in a non-contact manner.
【００５９】特に本実施の形態における方法は、相関処
理演算を行う際に、従来の時間領域の演算でなく、フー
リエ変換、畳み込み積分、逆フーリエ変換といった周波
数領域での演算を特徴としている。すなわち、時間領域
演算では相関処理を行う２信号をそれぞれサンプリング
して、掛け合わせた後に、片方の信号を１サンプリング
幅ずらしながら、ピークを探していくという逐次処理が
必要であるが、周波数領域演算では、逐次処理が生じな
いため、大幅な演算時間の短縮が図れる。ＦＦＴ演算に
おいて、ＤＳＰ（Digital signal processing）素子を
用いるとさらに演算時間の短縮が図れる。In particular, the method according to the present embodiment is characterized in that, in performing the correlation calculation, not the conventional calculation in the time domain but the calculation in the frequency domain such as Fourier transform, convolution integral, and inverse Fourier transform. That is, in the time domain calculation, two signals to be subjected to correlation processing are sampled and multiplied respectively, and then one signal is shifted by one sampling width, and a sequential process of searching for a peak is required. In this case, since sequential processing does not occur, it is possible to significantly reduce the calculation time. In the FFT calculation, if a DSP (Digital signal processing) element is used, the calculation time can be further shortened.
【００６０】一例として、符号長127×サンプリング10
＝総サンプリング数1270の相関処理当たりの演算時間を
示す。As an example, code length 127 × sampling 10
= Indicates the computation time per correlation process for the total sampling number 1270.
【００６１】 時間領域処理（従来法） １〜２秒 周波数領域処理 10〜20ms ＤＳＰ処理 1ms以下[0061] Time domain processing (conventional method) 1-2 seconds Frequency domain processing 10 to 20ms DSP processing 1ms or less
【００６２】相関処理以降の処理方法は従来技術と同じ
であるが、本発明においては、電位差検出においてノイ
ズ成分が抑制されているので、高精度で高感度な検出が
可能となっている。この処理方法を行うには、従来公知
である回路を使用すればよい。たとえば、電位差がゼロ
クロスする点で検出する回路による方法、電位差に閾値
を設け、電位差の絶対値がこの閾値を越えた後でゼロク
ロスする点を検出する回路による方法、正の電位差が最
大値を示す点と負の電位差が最大値を示す点との中点を
検出する回路による方法がある。The processing method after the correlation processing is the same as that of the prior art, but in the present invention, since the noise component is suppressed in the potential difference detection, highly accurate and highly sensitive detection is possible. A conventionally known circuit may be used to perform this processing method. For example, a method using a circuit that detects a point where the potential difference crosses zero, a method that sets a threshold value for the potential difference, and a method that detects a point that crosses zero after the absolute value of the potential difference exceeds this threshold, and the positive potential difference indicates the maximum value. There is a method using a circuit that detects the midpoint between the point and the point where the negative potential difference shows the maximum value.
【００６３】図７に、上記方法による相互相関ピーク値
（電位差の代表値）と探査機の移動距離（検査位置）と
の関係を、埋設鋼管１に印加する電圧および参照信号に
Ｍ系列原信号を使用したもの、すなわち図１０に示した
特願平９−５７１０２号に係る発明によるものと比較し
て示す。図７において、「原信号」は、特願平９−５７
１０２号に係る発明によるものを示し、「変調信号」は
本発明によるものを示す。FIG. 7 shows the relationship between the peak value of the cross-correlation (representative value of the potential difference) and the movement distance (inspection position) of the probe by the above method, in which the voltage applied to the buried steel pipe 1 and the reference signal are the M-series original signal. Is used, that is, in comparison with the invention according to Japanese Patent Application No. 9-57102 shown in FIG. In FIG. 7, “original signal” is Japanese Patent Application No. 9-57.
No. 102 according to the present invention, and “modulation signal” indicates one according to the present invention.
【００６４】測定の対象とした埋設鋼管は、管径１００
Ａ、管長１０ｍのＰＬＰ導管であり、約１ｍの深さに埋
設されたものである。塗膜損傷サイズは、５ｍｍ×４ｍ
ｍのものであった。探査機の車輪電極の間隔は１ｍであ
った。埋設鋼管への流入電流は１ｍＡ（４４０Ｈｚ）で
あった。The buried steel pipe to be measured had a pipe diameter of 100.
A, a PLP conduit having a pipe length of 10 m, which is buried at a depth of about 1 m. Coating damage size is 5mm x 4m
It was m. The space between the wheel electrodes of the spacecraft was 1 m. The inflow current into the buried steel pipe was 1 mA (440 Hz).
【００６５】図７を見ると、本発明においては、Ｍ系列
原信号を用いたものに比べてＳ／Ｎ比が２倍向上してい
ることがわかる。It can be seen from FIG. 7 that in the present invention, the S / N ratio is improved by a factor of 2 as compared with that using the M-sequence original signal.
【００６６】図６と図７からわかるように、本発明によ
れば、相互相関波形単体のＳ／Ｎ比が向上すると共に、
相互相関ピーク値と探査機の位置の関係を示すグラフ
も、きれいなＳ字型カーブを呈しており、このＳ字型カ
ーブのゼロクロス位置より、塗膜損傷位置を正確に知る
ことができる。よって、本発明の方法は、特願平９−５
７１０２号に係る発明による方法に比べて高感度、高精
度な塗膜損傷位置検出能を有することがわかる。As can be seen from FIGS. 6 and 7, according to the present invention, the S / N ratio of the cross-correlation waveform alone is improved, and
The graph showing the relationship between the cross-correlation peak value and the position of the spacecraft also shows a clean S-shaped curve, and the coating damage position can be accurately known from the zero-cross position of this S-shaped curve. Therefore, the method of the present invention is described in Japanese Patent Application No. 9-5.
It can be seen that, compared with the method according to the invention of No. 7102, it has a highly sensitive and highly accurate coating film damage position detection ability.
【００６７】特に地中の電気的な物理定数が変化すると
ころでは、Ｍ系列原信号を用いた方法は測定精度が著し
く悪くなるが、地中の伝播特性を考慮した本方法は安定
した検出能を発揮する。In particular, where the underground electrical physical constant changes, the method using the M-series original signal deteriorates the measurement accuracy remarkably, but this method considering the propagation characteristics in the ground has stable detection capability. Exert.
【００６８】以上説明した実施の形態では、Ｍ系列参照
信号をパーソナルコンピュータを用いて作成している
が、外部発生器からＡ／Ｄ変換器等を介して取り込んで
もよい。相互相関処理もパーソナルコンピュータで行う
代わりに、電子回路を用いて行ってもよい。In the embodiment described above, the M-series reference signal is created using a personal computer, but it may be taken in from an external generator via an A / D converter or the like. The cross-correlation process may be performed using an electronic circuit instead of the personal computer.
【００６９】本実施の形態では、Ｍ系列信号発生器１０
とＭ系列参照信号発生器１１を独立させている。このこ
とにより、埋設鋼管１に電圧を印加する装置と、信号を
検出して処理を行う装置を独立させることができ、最も
好ましいのであるが、もちろん、電力増幅器３に供給さ
れる掛算器３の信号をそのまま、あるいは遅延させて参
照信号として使用することもできる。この場合には、擬
似ランダム信号のみでなく、ランダム信号を印加電圧信
号、参照信号として使用することができる。In this embodiment, the M-sequence signal generator 10
And the M-sequence reference signal generator 11 are independent. This allows the device for applying a voltage to the buried steel pipe 1 and the device for detecting and processing the signal to be independent, which is the most preferable, but of course, of the multiplier 3 supplied to the power amplifier 3. The signal can be used as a reference signal as it is or after being delayed. In this case, not only the pseudo random signal but also the random signal can be used as the applied voltage signal and the reference signal.
【００７０】[0070]
【発明の効果】以上説明したように、本発明において
は、埋設鋼管に印加する交流電圧に、搬送波の位相を変
調することによって生成したランダム信号または擬似ラ
ンダム信号を使用し、相互相関処理を行うことにより、
ノイズ成分を除去してＳ／Ｎ比を改善しているので、埋
設鋼管の塗膜損傷位置を高感度で精度良く、確実に検出
することができる。また、ランダム信号、擬似ランダム
信号として、搬送波の位相を変調したものを用いている
ので、地中での減衰が少なく、感度のよい検出方法を実
現することができる。さらに、相互相関処理を、参照信
号と検出信号それぞれにフーリエ変換を行って、そのス
ペクトルの共役積の逆フーリエ変換を行うことにより実
施しているので、演算時間を短縮することができる。As described above, in the present invention, the cross-correlation process is performed by using the random signal or the pseudo-random signal generated by modulating the phase of the carrier wave as the AC voltage applied to the buried steel pipe. By
Since the noise component is removed and the S / N ratio is improved, it is possible to detect the coating film damage position of the buried steel pipe with high sensitivity, accuracy and reliability. Further, since the random signal and the pseudo-random signal that are obtained by modulating the phase of the carrier are used, it is possible to realize a highly sensitive detection method with little attenuation in the ground. Further, since the cross-correlation processing is performed by performing the Fourier transform on each of the reference signal and the detected signal and performing the inverse Fourier transform of the conjugate product of the spectrum, the calculation time can be shortened.
【００７１】相関処理演算が短縮できるので、サンプリ
ング間隔が短くでき、高精度な測定が可能となる。さら
に、検出感度がよくなったため、印加電流能力の低減、
検査面への散水処理の省略、車輪電極間距離の縮小化に
よる探査機の小型化が可能となり、システムを安価なも
のにすることができる。Since the correlation processing calculation can be shortened, the sampling interval can be shortened and highly accurate measurement can be performed. Furthermore, the improved detection sensitivity reduces the applied current capability,
It is possible to reduce the size of the probe by omitting the water spraying treatment on the inspection surface and reducing the distance between the wheel electrodes, which makes the system inexpensive.
【図１】本発明の実施の形態の一例を示す図である。FIG. 1 is a diagram showing an example of an embodiment of the present invention.
【図２】ＰＳＫ送信機の構成と出力波形を示す図であ
る。FIG. 2 is a diagram showing a configuration and output waveform of a PSK transmitter.
【図３】Ｍ系列原信号とＭ系列変調信号の波形を示す図
である。FIG. 3 is a diagram showing waveforms of an M-series original signal and an M-series modulated signal.
【図４】Ｍ系列原信号とＭ系列変調信号のパワースペク
トラムを示す図である。FIG. 4 is a diagram showing power spectra of an M-series original signal and an M-series modulated signal.
【図５】Ｍ系列原信号とＭ系列変調信号の自己相関関数
を示す図である。FIG. 5 is a diagram showing an autocorrelation function of an M-sequence original signal and an M-sequence modulated signal.
【図６】Ｍ系列原信号とＭ系列変調信号の相関処理結果
の一例を示す図である。FIG. 6 is a diagram showing an example of a correlation processing result of an M-series original signal and an M-series modulated signal.
【図７】本発明による塗膜損傷部の検出結果とＭ系列原
信号を用いた塗膜損傷部の検出結果の例を示す図であ
る。FIG. 7 is a diagram showing an example of a detection result of a damaged coating film according to the present invention and a detection result of a damaged coating film using an M-series original signal.
【図８】電位差法における塗膜損傷検出方法の概要を示
す図である。FIG. 8 is a diagram showing an outline of a coating film damage detection method in the potential difference method.
【図９】電位差法による塗膜損傷部の検出結果の例を示
す図である。FIG. 9 is a diagram showing an example of a detection result of a coating film damaged portion by a potential difference method.
【図１０】先願発明による塗膜損傷検出法の概要を示す
図である。FIG. 10 is a diagram showing an outline of a coating film damage detection method according to the prior application.
【図１１】Ｍ系列信号発生回路の例を示す図である。FIG. 11 is a diagram showing an example of an M-sequence signal generation circuit.
【図１２】Ｍ系列信号とその自己相関信号波形の例を示
す図である。FIG. 12 is a diagram showing an example of an M-sequence signal and its autocorrelation signal waveform.
【図１３】先願発明による参照信号と検出信号の相互相
関波形の例を示す図である。FIG. 13 is a diagram showing an example of a cross-correlation waveform of a reference signal and a detection signal according to the prior invention.
【図１４】先願発明による塗膜損傷部の検出結果を示す
図である。FIG. 14 is a diagram showing a detection result of a coating film damaged portion according to the prior invention.
【図１５】Ｍ系列法による印加電圧と検出電圧の信号波
形の例を示す図である。FIG. 15 is a diagram showing an example of signal waveforms of an applied voltage and a detected voltage according to the M-sequence method.
１：埋設鋼管 ２：交流電源 ３：電力増幅器 ４：接地電極 ５：塗膜損傷部 ６：探査機 ６ａ，６ｂ：車輪電極 ７：フィルタ ８：電位差検出器 １０：Ｍ系列信号発生器 １１：Ｍ系列参照信号発生器 １２：相関処理部 １３：パーソナルコンピュータ １４：正弦波発生器 １５：掛算器 １６：ＦＦＴ処理部 １７：複素共役処理部 １８：畳み込み積分処理部 １９：逆ＦＦＴ処理部 1: Buried steel pipe 2: AC power supply 3: Power amplifier 4: Ground electrode 5: Damaged part of coating film 6: probe 6a, 6b: Wheel electrodes 7: Filter 8: Potential difference detector 10: M-sequence signal generator 11: M-sequence reference signal generator 12: Correlation processing unit 13: Personal computer 14: Sine wave generator 15: Multiplier 16: FFT processing unit 17: Complex conjugate processing unit 18: Convolution integration processing unit 19: Inverse FFT processing section
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7，ＤＢ名) G01N 27/00 - 27/24 G01N 27/72 - 27/90 ＪＩＣＳＴファイル（ＪＯＩＳ)─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. 7 , DB name) G01N 27/00-27/24 G01N 27/72-27/90 JISST file (JOIS)
Claims (4)
ることにより当該埋設鋼管に交流電流を流し、管軸方向
に沿った位置にある２点間の電位差を当該２点を移動さ
せながら順次検出することにより、前記交流電流により
地上に発生する電位分布を測定し、その電位分布の変化
から当該埋設鋼管の塗膜損傷位置を検知する方法におい
て、搬送波の位相を変調させることによって生成したラ
ンダム信号又は擬似ランダム信号を、埋設鋼管に印加す
る信号として用い、前記埋設鋼管に印加する交流電圧信
号から取りだした参照信号と、前記２点間の電位差の検
出信号それぞれにフーリエ変換を行って、そのスペクト
ルの共役積の逆フーリエ変換を行うことにより、前記２
信号の相関処理を行い、そのピーク値を前記２点間の電
位差の代表値とし、当該代表値より電位分布を求め、求
めた電位分布の変化から当該埋設管の塗膜損傷位置を検
出することを特徴とする埋設鋼管の塗膜損傷位置検出方
法。1. An alternating current is applied to the buried steel pipe by applying an alternating voltage between the buried steel pipe and the ground, and the potential difference between the two points located along the pipe axis direction is moved while the two points are moved. By sequentially detecting the potential distribution generated on the ground by the alternating current and detecting the coating film damage position of the buried steel pipe from the change in the potential distribution, it was generated by modulating the phase of the carrier wave . Random signal or pseudo-random signal is used as a signal to be applied to the buried steel pipe, the reference signal extracted from the AC voltage signal applied to the buried steel pipe, and the Fourier transform to each of the detection signals of the potential difference between the two points, By performing the inverse Fourier transform of the conjugate product of the spectrum,
Correlating the signals, using the peak value as the representative value of the potential difference between the two points, obtaining the potential distribution from the representative value, and detecting the coating film damage position of the buried pipe from the change in the obtained potential distribution. A method for detecting the position of coating film damage on a buried steel pipe, characterized by.
ることにより当該埋設鋼管に交流電流を流し、管軸方向
に沿った位置にある２点間の電位差を当該２点を移動さ
せながら順次検出することにより、前記交流電流により
地上に発生する電位分布を測定し、その電位分布の変化
から当該埋設鋼管の塗膜損傷位置を検知する方法におい
て、搬送波の位相を変調させることによって生成した擬
似ランダム信号を、埋設鋼管に印加する信号として用
い、埋設鋼管に印加する交流電圧とは独立に生成され
た、当該交流電圧と同じパターンの参照信号と、前記２
点間の電位差の検出信号それぞれにフーリエ変換を行っ
て、そのスペクトルの共役積の逆フーリエ変換を行うこ
とにより、前記２信号の相関処理を行い、そのピーク値
を前記２点間の電位差の代表値とし、当該代表値より電
位分布を求め、求めた電位分布の変化から当該埋設管の
塗膜損傷位置を検出することを特徴とする埋設鋼管の塗
膜損傷位置検出方法。2. An alternating current is applied to the buried steel pipe by applying an alternating voltage between the buried steel pipe and the ground, and the potential difference between the two points along the pipe axis direction is moved while the two points are moved. By sequentially detecting the potential distribution generated on the ground by the alternating current and detecting the coating film damage position of the buried steel pipe from the change in the potential distribution, it was generated by modulating the phase of the carrier wave . A pseudo random signal is used as a signal to be applied to the buried steel pipe, the reference signal having the same pattern as the AC voltage generated independently of the AC voltage applied to the buried steel pipe, and the above-mentioned 2
A Fourier transform is performed on each of the detection signals of the potential difference between the points, and an inverse Fourier transform of the conjugate product of the spectrum is performed to perform the correlation processing of the two signals, and the peak value thereof is a representative of the potential difference between the two points. Value, the potential distribution is obtained from the representative value, and the coating film damage position of the buried pipe is detected from the change in the obtained potential distribution.
成したランダム信号または擬似ランダム信号を発生する
信号発生器と、信号発生器の出力に比例した電圧を発生
し、埋設鋼管と大地の間に通電する電力増幅器と、地表
面を埋設鋼管の管軸方向に沿って走行し、埋設鋼管の管
軸方向に隔離して配置された複数の車輪電極を有する探
査機と、前記複数の車輪電極の間の電位差を測定する電
圧測定器と、前記信号発生器から取り出した参照信号と
前記電圧測定器の出力信号それぞれにフーリエ変換を行
って、そのスペクトルの共役積の逆フーリエ変換を行う
ことにより、前記２信号の相関処理を演算しそのピーク
値を出力する相関処理装置と、当該相関処理装置の出力
の変化から当該埋設鋼管の塗膜損傷位置を検出する手段
とを有してなる埋設鋼管の塗膜損傷位置検出装置。3. A signal generator that generates a random signal or a pseudo-random signal generated by modulating the phase of a carrier wave , and a voltage that is proportional to the output of the signal generator and that is energized between the buried steel pipe and the ground. Between the power amplifier and the exploration machine having a plurality of wheel electrodes that travel along the pipe axis direction of the buried steel pipe on the ground surface and are separated in the pipe axis direction of the buried steel pipe, and the plurality of wheel electrodes. Voltage measuring device for measuring the potential difference of, a Fourier transform to each of the reference signal and the output signal of the voltage measuring device taken out from the signal generator, by performing an inverse Fourier transform of the conjugate product of the spectrum, A buried structure having a correlation processing device for calculating a correlation process of two signals and outputting a peak value thereof, and means for detecting a coating film damage position of the buried steel pipe from a change in output of the correlation processing device. Coating damage position detecting device of the tube.
成した擬似ランダム信号を発生する第１の信号発生器
と、第１の信号発生器の出力に比例した電圧を発生し、
埋設鋼管と大地の間に通電する電力増幅器と、地表面を
埋設鋼管の管軸方向に沿って走行し、埋設鋼管の管軸方
向に隔離して配置された複数の車輪を有する探査機と、
前記複数の車輪電極の間の電位差を測定する電圧測定器
と、第１の信号発生器と同じパターンの波形を出力する
第２の信号発生器と、第２の信号発生器の出力信号と前
記電圧測定器の出力信号それぞれにフーリエ変換を行っ
て、そのスペクトルの共役積の逆フーリエ変換を行うこ
とによって、前記２信号の相関処理を演算しそのピーク
値を出力する相関処理装置と、当該相関処理装置の出力
の変化から当該埋設鋼管の塗膜損傷位置を検出する手段
とを有してなる埋設鋼管の塗膜損傷位置検出装置。4. A first signal generator for generating a pseudo-random signal generated by modulating the phase of a carrier wave , and a voltage proportional to the output of the first signal generator,
A power amplifier that energizes between the buried steel pipe and the ground, a ground plane running along the pipe axis direction of the buried steel pipe, and a probe having a plurality of wheels arranged separately in the pipe axis direction of the buried steel pipe,
A voltage measuring device for measuring a potential difference between the plurality of wheel electrodes, a second signal generator for outputting a waveform having the same pattern as that of the first signal generator, an output signal of the second signal generator, and A correlation processing device that calculates a correlation process of the two signals and outputs a peak value by performing a Fourier transform on each output signal of the voltage measuring device and performing an inverse Fourier transform of the conjugate product of the spectrum, and the correlation A coating film damage position detection device for a buried steel pipe, comprising means for detecting the coating film damage position of the buried steel pipe from changes in the output of the processing device.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP34199197A JP3377171B2 (en) | 1997-11-28 | 1997-11-28 | Method and apparatus for detecting paint film damage position of buried steel pipe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP34199197A JP3377171B2 (en) | 1997-11-28 | 1997-11-28 | Method and apparatus for detecting paint film damage position of buried steel pipe |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11160281A JPH11160281A (en) | 1999-06-18 |
| JP3377171B2 true JP3377171B2 (en) | 2003-02-17 |
Family
ID=18350337
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP34199197A Expired - Lifetime JP3377171B2 (en) | 1997-11-28 | 1997-11-28 | Method and apparatus for detecting paint film damage position of buried steel pipe |
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| Country | Link |
|---|---|
| JP (1) | JP3377171B2 (en) |
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|---|---|---|---|---|
| JP5325963B2 (en) * | 2011-10-24 | 2013-10-23 | 本田技研工業株式会社 | Sequential impedance measurement method, measurement device, and fuel cell system |
| CN103063738A (en) * | 2012-12-19 | 2013-04-24 | 上海市特种设备监督检验技术研究院 | Detecting method of outer anti-corrosion layer of buried fuel gas steel pipeline |
| CN103592363B (en) * | 2013-03-04 | 2016-05-04 | 常州大学 | Method and the device of the breakage of monitoring buried metal pipeline corrosion-inhibiting coating |
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1997
- 1997-11-28 JP JP34199197A patent/JP3377171B2/en not_active Expired - Lifetime
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|---|---|
| JPH11160281A (en) | 1999-06-18 |
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