JPS603626B2 - Cable detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system for detecting the position of cables that are laid, particularly cables that are laid underground, on the ocean floor, at the bottom of a river, or the like.

On land, cables have long been buried underground to protect them from external forces.

On the other hand, when laying cables in the ocean or rivers, it has become popular in recent years to bury the cables under the ocean floor or riverbed to prevent them from being broken by fishing nets, ship anchors, etc. It's coming. When digging up such a buried cable for repair or hoisting it onto a repair ship, conventionally, a special hook shaped to go deep into the sand on the seabed is used to hold the cable. The method used is to tow it across the ship, hook a cable on it, and pull it onto the ship. However, since the cable is buried and fixed in the earth and sand, the cable will be severed by the hook unless the towing of the hook is stopped immediately when the cable is caught on the hook. As a result, the hook had to be towed at extremely low speeds, necessitating extremely long hours of work. The present invention aims to provide a method for solving the drawbacks of the conventional technology as described above, and has three magnetic field detectors (hereinafter referred to as "component magnetic field detection") each having magnetic field detection directivity of cosine characteristic with the same sensitivity. Magnetic field detectors with this configuration are hereinafter referred to as "orthogonal 3
The maximum detection sensitivity directivity direction of one of the component magnetic field detectors (referred to as "axial magnetic field detector") is always in the vertical direction, and
Maximum detection sensitivity of component magnetic field detector Using a magnetic field detector (hereinafter referred to as "vertically oriented orthogonal 3-axis magnetic field detector") configured so that the directional direction always points in the horizontal direction, Information regarding the cable installation position is obtained by detecting the signal magnetic field generated due to the applied search current and processing the detection signals of the component magnetic field detectors that constitute the vertically oriented orthogonal three-axis magnetic field detector. It is characterized by displaying this or guiding and controlling a cable burying machine or a line searching machine to a predetermined position or direction.

According to the present invention, the cable position can be detected even from a distance, which greatly improves the efficiency of cable detection work.In addition, since the cable position can be detected accurately, the cable can be pulled onto the ship without being cut. It is possible. Furthermore, when burying a cable, accurate detection of the cable allows safe and reliable guidance control of the cable burying machine. FIG. 1 is a drawing showing one embodiment of the cable detection method of the present invention.

In order to explain FIG. 1 in detail, the vertically oriented orthogonal three-axis magnetic field detector 15 will be explained using FIGS. 2 and 3. FIG. 2A is a drawing showing the configuration of the orthogonal three-anchor magnetic field detector 10. The component magnetic field detectors 4, 6, and 8, each having a cosine characteristic detection directivity, are arranged so that their maximum detection sensitivity directivity directions are orthogonal to each other. Now, the detection directivity of the component magnetic field detector 4 is set to three orthogonal axes x, y.
, if the maximum detection sensitivity is in the y-axis direction of the z-axis, the detection directivity of the detector has a string characteristic directivity on all planes including the y-axis as shown in Figure 2B. shall be taken as a thing. It is also assumed that the other component magnetic field detectors 6 and 8 have similar cosine characteristic detection directivity. These component magnetic field detectors 4, 6, and 8 constituting the orthogonal three-axis magnetic field detector 10
detects the surrounding magnetic field according to each detection directivity,
It outputs a corresponding electrical signal. These component magnetic field detectors 4, 6, and 8 can be easily realized by, for example, a flux gate magnetic field detector or a thin film double frequency oscillation type magnetic field detector. FIG. 3 shows a configuration example of a vertically oriented orthogonal three-axis magnetic field detector 15, in which the orthogonal three-axis magnetic field detector 10 explained using FIG. It is configured so that the direction of sensitivity directivity always points in the vertical direction.

Note that if the maximum detection sensitivity directivity direction of the component magnetic field detector 4 is always oriented in the vertical direction, the maximum detection sensitivity directivity of the other component magnetic field detectors 6 and 8 whose maximum detection sensitivity directivity direction is perpendicular to it is Naturally, the direction is always horizontal. In FIG. 3, parts common to FIGS. 1 and 2 are given the same numbers. In the figure, 10 is an orthogonal 3-axis magnetic field detector, 15 is a vertically oriented orthogonal 3-axis magnetic field detector, Yotsukawa is the same container, 41 is a wheel weight attached to the bottom of the orthogonal 3-axis magnetic field detector 10, and 42 is a relatively It is a highly viscous liquid paraffin-like liquid. 43 is orthogonal three-axis magnetic field detector 10
A light and flexible wire is used as a signal line for extracting electrical signals.

44 is a connector for connecting the signal lines 31 and 44.

The operation shown in FIG. 3 will be explained.

A buoyant force is generated by the liquid 42, and at a position where the weight and buoyancy of the detector 10 and the additional weight 10 are balanced, the detector 10 generates an orthogonal 3-axis magnetic field detector in the liquid 42. It floats with the weight 41 attached to 10 facing down. In this state, if the maximum detection sensitivity direction of the component magnetic field detector 4 is oriented vertically, no matter how the container 40 is tilted, the maximum detection sensitivity direction of the same component magnetic field detector 4 will always be vertical. , and component magnetic field detectors 6 and 8
The maximum detection sensitivity directivity direction is always oriented in the horizontal direction, and these component magnetic field detectors 4, 6, and 8 detect the magnetic field at that point according to their respective detection directivity, and output electric signals corresponding to the magnetic field. , the electrical signal can be taken out to the outside via the signal line 43, the connector 44, and the signal line 31. Next, one embodiment of the cable detection system of the present invention will be described based on FIG.

One vertically oriented orthogonal three-axis magnetic field detector 15 is mounted on a mobile body 2 that can freely move underwater by remote control from a mother ship.

If a fault occurs in the cable 21 buried under the seabed, for example, if the conductor is shorted at the fault point 22, a search current cannot be supplied from the cable terminal 23 on land using the search signal source 24. , the return path of the search current is formed between the ground fault point 22 and the ground point 25 of the search signal source 24. The search current generates a magnetic field around the cable. The strength of this search signal magnetic field is proportional to the magnitude of the search current and inversely proportional to the distance from the cable. Further, the direction of the search signal magnetic field is a tangential direction on the circumference centered on the cable. When the movable body 2 equipped with the vertically oriented orthogonal 3-axis magnetic field detector 15 is placed around the cable 21, the component magnetic field detectors 4 and 6 forming the vertically oriented orthogonal 3-axis magnetic field detector 15 are arranged around the cable 21.
and 8 detect the strength of the magnetic field caused by the search current supplied to the cable 21 according to the respective directional characteristics,
It outputs a corresponding electrical signal.

Each signal output is transmitted by a signal line 31 to a receiving section 32 on the bus.

The receiving section 32 mainly consists of the following four types of functions.
That is, '1) extracting each signal component corresponding to the search signal magnetic field from the signal of each component magnetic field detector,
Calculating the strength and direction of the magnetic field from each extracted signal; [3' Calculating the position information of the cable based on the calculation results; [4] Calculating the position of the cable based on the calculation results. It is to display information. Receiving section 3 in Fig. 1
2, the block 33 plays the role of function '1}, the block 34 plays the role of function {2}, the block 35 plays the role of function '3', and the block 36 plays the role of function (4'. Note that the functions m, {
Of course, it is also possible to configure the hardware playing the roles of 2), the legs, and 4) without clearly distinguishing them, as in blocks 33, 34, 35, and 36 in FIG. Below is a first example of the operation of the cable detection method according to the present invention.
This will be explained with reference to FIGS. 2 and 3.

When a search current is supplied to the cable 21, a magnetic field is generated around the cable that is distributed concentrically with the cable as the center. The magnitude of this magnetic field (Gauss) is the distance R (m) from the cable, and the current applied to the cable 21 is 1
When (A) is assumed, a magnetic field with a strength of H=a-reed (where a is a proportionality constant) is generated, and the direction of the magnetic field is tangential to the circumference of the cable.

component magnetic field detector 4 of the vertically oriented orthogonal three-axis magnetic field detector 15;
6 and 8 each detect a search signal magnetic field having a strength corresponding to the distance from the cable 21 according to the respective detection directivity, and each detected signal is transmitted to the receiving section 32 via the signal line 31. Ru. The receiving unit 32 extracts electrical signals corresponding to the search signal magnetic field from the output signals of the component magnetic field detectors 4, 6, and 8 (33), and determines the strength and direction of the search signal magnetic field from the extracted signals. is calculated (34) by arithmetic processing as described below, and from the results of the calculated magnetic field strength and direction, the position and burial depth of the cable 21 are determined by further arithmetic processing as will be described later (35). The results are displayed moment by moment (36) on, for example, a cathode ray tube display. In this way, detection of the cable can be made extremely easy,
It is possible to improve the efficiency of the cable search work, thereby shortening the work time for cable search and reducing costs. Furthermore, since a single vertically oriented orthogonal three-axis magnetic field detector is sufficient as a detector, the apparatus can be manufactured at low cost.
FIG. 4 is for explaining the embodiment of FIG. 1 in more detail; FIG. 4A shows a plan view, FIG. 4B shows a side view, and FIG. 4C shows a conceptual diagram of magnetic field vectors.

In FIG. 4, parts common to those in FIG. 1 are given the same numbers. Now, it is assumed that the mobile object 2 equipped with the vertically oriented orthogonal 3-axis magnetic field detector 15 is being towed almost parallel to the seabed surface, and the distance between the vertically oriented orthogonal 3-axis magnetic field detector 15 and the cable 21 is as shown in FIG. As shown in B, it is assumed that the distance is R, the horizontal distance between the detector 15 and the cable 21 is L, and the buried depth of the cable is D.

The strength of the search signal magnetic field caused by the current supplied to the cable 21 at the point where the vertically oriented orthogonal three-axis magnetic field detector 15 is located is Hf, the angle of that direction with respect to the horizontal plane is 8, and each component magnetic field detector Let the intensities of the search signal magnetic fields detected by 4, 6, and 8 be approximately, day 6, and day 8, respectively. The component magnetic field detectors 4, 6, and 8 have magnetic field detection directivity with cosine characteristics of the same sensitivity, and are configured so that the direction of maximum detection sensitivity directivity of the component magnetic field detector 4 always points in the vertical direction. Therefore, even if the vertically oriented orthogonal three-axis magnetic field detector 15 is subjected to vibration, pitching, or rolling, the component magnetic field detector 4 detects the vertical magnetic field component of the signal magnetic field at the point where it is located. Further, component magnetic field detectors 6 and 8 detect components in respective directional directions of the signal magnetic field. The search signal magnetic field vector (strength and direction) at the point of the magnetic field detector 15 is related only to the positional relationship between the vertically oriented orthogonal three-axis magnetic field detector 15 and the cable 21 and the magnitude of the search current supplied to the cable 21. Therefore, they have the following relationship. However, a is a proportionality constant, and 1 is a search current supplied to the cable.

On the other hand, as is clear with reference to FIG. 4B, the horizontal distance and vertical distance (burying depth) D between the vertically oriented orthogonal three-axis magnetic field detector 15 and the cable 21 are shown as follows.

L=R・sinal D=Rlcosal '2' formula m
From (2), L and D are expressed as follows.

However, it is calculated from IHI = nohi reed 10 day cost.

In the end, the cable 21 is generated using the vertically oriented orthogonal three-axis magnetic field detector 15 (component magnetic field detectors 4, 6, and 8) in which the maximum detection sensitivity directivity direction of the component magnetic field detector 4 is always oriented in the vertical direction. By detecting the strength and direction of the search signal magnetic field and performing arithmetic processing using the above equations {1} and '3', the position of the cable (horizontal distance between the moving body 2 and the cable 21) L and burial depth (moving body 2 and cable 2)
1) can be obtained at the same time. Also L
It is also possible to track the cable (tracing directly above the cable) by controlling the distance D, for example, so that the moving body 2 is directly above the cable. Note that since the value of L changes as the ship moves, the location of the cable can also be known from this change. FIG. 5 is for explaining an example of a portion of the receiving section 32. In FIG.

The receiving unit 32 uses the detected voltages V4, V6, and V8 of the respective component magnetic field detectors 4, 6, and 8 to execute the calculations shown in the formula '11 and formula above. In Figure 5, the detection signal V4
, V6 and V8 are each first converted to 2 by the squaring circuit 501.
After the calculation, an addition circuit 51 adds the calculated values, and a square root circuit 52 obtains a voltage lVI corresponding to the strength IHI of the search signal magnetic field shown in the formula '11 above. while V4 and square root circuit 5
The output voltage fVl of 2 (=So V 覦 1 V 取 1 V 萱) is sent to the divider circuit 53 and is further used by the reverse positive yabu circuit 54 to form a line with the horizontal plane in the direction of the search signal magnetic field shown in equation [1] above. angle a
is obtained.

This 8 is sent to the sine circuit 55 and the cosine circuit 56, and the si
Obtain the absolute values of no and coso. The other output amount Vl of the square root circuit 52 is sent to a division circuit 57, and after dividing the constant signal a, is multiplied by the constant signal 1 in the multiplication circuit 58 to obtain al/Hayabusa Vl. In the multiplier circuit 59, the output signal sin of the sine circuit 55 is multiplied by the output signal al/IVI of the multiplier circuit 58, and a signal L indicating the position of the cable is output. On the other hand, in the multiplication circuit 60, the output signal cos8 of the cosine circuit 56 and the output signal al of the multiplication circuit 58 are
/fVI is multiplied, and a signal D indicating the buried depth of the cable is output. As described above, by using the detection outputs V4, V6, and V8 of the component magnetic field detectors 4, 6, and 8 of the vertically oriented orthogonal three-axis magnetic field detector 15, two pieces of information about the cable position and burial depth can be obtained simultaneously. Can be done.

In the example of FIG. 3, the case where the orthogonal three-way magnetic field detector 10 is floated on the liquid 42 has been described, but when an irregular external force is applied to the vertically oriented orthogonal three-way magnetic field detector 15, the orthogonal three-way magnetic field detector 15 can be detected. Irregular vibrations may be applied to the device 10, making it difficult to detect the cable. In such a case, it is preferable to completely immerse the orthogonal three-way magnetic field detector 10 in the liquid as shown in the embodiment shown in FIG. In this figure, parts common to those in FIG. 3 are given the same numbers. Reference numeral 45 indicates a liquid having a specific gravity lower than that of the liquid 42.

In this case, the three orthogonal magnetic field detectors 10, the weights of the additional weights 41, and the buoyancy of the liquids 42, 45 are balanced, and the magnetic field detectors 1 float in the liquid, similar to the example shown in FIG. The maximum detection sensitivity directivity direction of the component magnetic field detector 4 can always be directed in the vertical direction. In this example, since the container 401 is filled with liquid, even if an irregular external force is applied, irregular vibrations are less likely to be applied to the orthogonal three-bag magnetic field detector. FIG. 7 shows another embodiment in which the maximum detection sensitivity directivity direction of the component magnetic field detector 4 of the orthogonal three-axis magnetic field detector 10 is always directed in the vertical direction.

In this figure, the same numbers are given to the same parts as in FIGS. 3 and 6. In this example, the orthogonal three-ball magnetic field detector 10 and the additional weight 41 are constructed so that their weight is much greater than the buoyancy of the liquid 42, and the device has the same characteristics and characteristics as shown in FIG. . FIG. 8 shows another embodiment in which the maximum detection sensitivity directivity direction of the component magnetic field detector 4 of the orthogonal three-axis magnetic field detector 10 is always directed in the vertical direction.

In this figure, the same numbers are given to the same parts as in FIG. 3, FIG. 6, FIG. 7, etc. In the figure, a shaft 46 is fixed to the orthogonal three crane magnetic field detector ID, and this shaft can freely rotate in bearings A and A' of an arm 47.

Furthermore, the arm 47 can freely rotate in the bearing B of the arm 48. Arm 48 is fixed to the inner wall of container 40, which is not shown in the figure. The additional wheel weight 41 allows the maximum detection sensitivity directivity direction of the component magnetic field detector 4 of the orthogonal three-way magnetic field detector 10 to always be oriented in the vertical direction. In the case of this example, the entire portion shown in Fig. 8 is placed in a comparatively high viscosity liquid filled with a container 4 for the purpose of reducing irregular vibrations applied to the orthogonal three-wavelength magnetic field detector 10 from irregularly applied external forces. It is best to bury it. Figure 9, 1st
Figures 0, 11, and 12 show examples of application of the cable detection method of the present invention. When cable detection is carried out by mounting a cable detector on a vehicle that can move freely on the seabed, Figure 11 shows how to detect cables while towing the cable detector with a cable burying machine when burying the cable. In particular, when performing cable burying (measurement of burying depth), Figure 12 shows each case when performing cable detection (particularly cable position measurement) to guide and control the cable burying machine onto the cable when burying cables. An example of application is shown.

In FIG. 9, 80 is a cable ship, 81 is a carrier with a signal line inside, 82 is a coupler that branches signal lines and traces to a cable detector 86 and a special hook 83, and 21 is a cable. , 84 is the sea level, and 85 is the sea bottom surface. The cable detector 86 is composed of vertically oriented orthogonal three-magnetic field detectors as shown in FIGS. 3 to 6. K
As shown in the figure, the bull detector 86 is towed by a cable ship with a special hook, and is supplied to the cable from the land and tin station.
The magnetic field (dotted line in the figure) generated by the supplied search current is detected, and the detection signal is transmitted to the receiving section in the cable ship 80 through the signal line in the antenna 81. On the cable ship, based on the processing results of the transmitted signals, the position of the cable and the depth to which it is buried can be determined from far in front of the cable, so the towing speed can be adjusted as necessary. In FIG. 10, parts common to those in FIG. 7 are given the same numbers. In the same figure, 87 is a self-propelled Veagle, 88 is a control device for cable tracking, and a cable detector 86 is installed on the same aircraft as in the case of Fig. 7, and a magnetic field (see Fig. dotted line) and sends the detection signal to the receiving section 88, and calculates it based on the above equations '1} and '3', and then sends it to the cable tracking control device 8.
8, the horizontal distance L to the cable is constant (for example, 0
), for example, by controlling a steering mechanism to guide and control the vehicle 87. FIG. 11 shows an embodiment in which the present invention is applied to measurement of cable burial depth, and parts common to those in FIG. 9 etc. are given the same numbers.

In the figure, 90 is a cable burying machine that buries cables while excavating the seabed, and the cable detector 86 is either mounted on the cable burying machine 90 or towed. In this example, based on the same principle as described in FIG. 9, the buried depth of the cable 21 is
displayed on the receiving section of the device. FIG. 12 shows an embodiment in which the present invention is applied to cable tracking when burying cables, and parts common to those in FIG. 9 etc. are given the same numbers. In the same figure, cable burying machine 9
0' Therefore, to bury the cable 21, the cable 21
The cable burying machine detects the position of the cable 21 and faithfully buries the cable 21.
It is necessary to control the guidance above. Therefore, the cable detector 86 will be mounted at the front of the cable burying machine 90. In this example, the position of the cable is detected by the cable detector 86 and the receiver 88 based on the same principle as explained using FIG. 10, and based on the results, In order to guide the cable burying machine 90, the steering mechanism of the cable tracking control device 88 is controlled. Any type of magnetic field detector may be used as long as it has cosine characteristic detection directivity.

In addition, although the above description deals with the case where the cable is on the seabed, it is not limited to the seabed, but can also be applied to detecting the position of cables buried on land, cables laid in rivers, or indoor overhead wires. Needless to say.

As described above, according to the present invention, the position of a buried cable can be accurately detected.

[Brief explanation of the drawing]

Figure 1 shows an example of the configuration of the cable detection method according to the present invention;
Figure A is a configuration diagram of an orthogonal 3-axis magnetic field detector, Figure 2 B is a detection directivity characteristic diagram of a component magnetic field detector, Figure 3 is a structural example of a vertically oriented orthogonal 3-axis magnetic field detector of the present invention, and Figure 4 A, B, and C are diagrams explaining the principle of the cable detection method according to the present invention, FIG. 5 is a block diagram of the main part of the receiving section 32 in FIG. 1, and FIGS. Modified examples of the structure of the vertically oriented orthogonal three-axis magnetic field detector, Figures 9 and 10
11 and 12 are diagrams showing an application example of the cable detection method of the present invention. 2...Moving object, 4, 6, 8... Component magnetic field detector, 10・・・・・・Orthogonal 3-axis magnetic field detector, 15...
...Vertically oriented orthogonal 3-axis magnetic field detector, 21...
・Cable, 22...Failure point, 23...Grounding point, 24...Search signal source, 23...
・Cable terminal, 31...Signal line, 32...
. . . Receiving section, 38 . . . Control signal line. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Traditional T Figure Figure 8 Figure 12 Figure 9 Figure 10 Figure 11

Claims (1)

[Claims] 1. At least three magnetic field detectors having magnetic field detection directivity with cosine characteristics, the maximum detection sensitivity directivity directions of which are orthogonal to each other, and the maximum detection sensitivity directivity direction of one magnetic field detector is A vertically oriented orthogonal three-axis magnetic field detector configured so as to be in the vertical direction is moved near the cable to be searched, and the magnetic field caused by the current in the cable is detected by each magnetic field detector, and the strength of the magnetic field is determined by the strength of the cable. The horizontal distance from the vertically oriented orthogonal 3-axis magnetic field detector to the cable and the buried depth of the cable are detected because the direction of the magnetic field is tangential to the circumference of the cable and is proportional to the reciprocal of the distance between the cables. This cable detection method is characterized by: 2. The cable detection method according to claim 1, wherein the vertically oriented orthogonal three-axis magnetic field detector has a weight so that the maximum detection sensitivity directivity direction of one magnetic field detector is in the vertical direction. .