JPH06102307A - Cable tracking device - Google Patents

Abstract

PURPOSE:To reduce the size of a magnetic sensor by detecting two components, in the vertical direction and in the horizontal direction, of a magnetic field generated by an alternating current flowing through a cable so as to calculate the cable position. CONSTITUTION:Three magnetic sensors 4x-4z are provided in the axial directions of xyz co-ordinates fixed to a robot in such a manner that the optimum sensitivity direction agrees with the x-axis in the case of the sensor 4x, y-axis in the case of the sensor 4y and z-axis directing downward in the vertical direction in the case of sensor 4z, respectively, and installed close to each other. A magnetic sensor container 4a for storing the sensors 4x-4z is suspended from a robot through a universal joint. In a signal processing means 9, the respective signals ix-iz and i1, i2 output from a filter block 9a are amplified by a signal amplifying block 9b, and then operated according to a designated expression by an arithmetic block 9c to calculate an angle theta in the horizontal direction and an angle phi in the vertical direction that show the attitude of a robot to a submarine cable, and geomagnetic orientation beta.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device used for so-called cable tracking for searching the position of an electric cable buried in the seabed, and more specifically to a ground fault of the electric cable by the detecting means. The present invention relates to a cable tracking device that can search for an accident point.

[0002]

2. Description of the Related Art An electric cable (hereinafter simply referred to as a submarine cable) laid on the bottom of the sea for the purpose of communication between the land and the sea separated from each other, power transmission, etc. is generally buried by digging the bottom of the sea about 1 m deep. However, such a submarine cable has a problem that it is damaged by being hooked on a ship anchor or the like, and a ground fault often occurs. Ground fault (accident point) to repair the submarine cable where the ground fault occurred
The following means have been conventionally used to search for. That is, when a current is passed between the submarine cable and the ground electrode, the current does not flow before the ground fault. Therefore, if you detect the magnetic field generated by the current along the submarine cable,
The position where the magnetic field disappears is the ground fault point. The conventional ground fault detection method will be specifically described below with reference to FIGS.

FIG. 5 shows a state in which an AC power supply 3 is connected between the submarine cable 1 and the ground electrode 2 in order to search the ground fault point S of the submarine cable 1. In this case, an electric closed circuit is formed between the submarine cable 1 and the ground / seawater through the ground fault point S, and the current I flows, but the current I does not flow in the submarine cable 1 beyond the ground fault point S. Therefore, the current I
The position of the submarine cable 1 can be detected by detecting the magnetic field generated by, and the position of the ground fault point S can be detected by detecting the point where the magnetic field disappears. The frequency of the AC power supply 3 is generally 1 kHz in addition to commercial AC power supply frequencies such as 50 Hz and 60 Hz. Reference numeral 4 in FIG. 5 is a magnetic sensor that is towed by the mother ship 5 and moves in the sea, and 6 is the seabed. Due to the current I flowing through the submarine cable 1, a magnetic field H (FIG. 6A) generated from the submarine cable 1 at a position with a radius r is

[0004] It is represented by. Now, the horizontal component Hy of the magnetic field H at the point P on the radius r in the direction of the angle θ with respect to the vertical axis Z whose origin is the center of the submarine cable 1 is

[0005] The relationship between the coordinate Y and the horizontal component Hy when the magnetic sensor 4 is moved across the submarine cable 1 when Z is constant, that is, the height from the submarine cable 1 is constant, is shown in FIG. As shown in FIG. 6B, the maximum value is directly above the submarine cable 1 and the curve changes so as to decrease as the submarine cable 1 is left. The vertical component Hz is

[0006] And the relationship between the coordinate Y and the vertical component Hz when Z is made constant, that is, when the height from the submarine cable 1 is made constant and the magnetic sensor 4 is moved, as in the above. As shown in FIG. 6C, it has a minimum value just above the submarine cable 1, and once the maximum value occurs as the submarine cable 1 is left, it changes in a curve that decreases as the submarine cable 1 is left.

That is, by using the magnetic sensor 4 which simultaneously detects the horizontal component Hy and the vertical component Hz, the horizontal component Hy is detected, but the position where the vertical component Hz is not detected is almost directly above the submarine cable 1. It can be determined that the sensor 4 is located. Therefore, as shown in FIG. 7, the magnetic sensor 4 towed by the mother ship 5 (FIG. 5) is made to meander, and the vehicle is sailed across the submarine cable 1 many times, and the vertical component is detected although the horizontal component Hy is detected. The laying position of the submarine cable 1 can be confirmed by obtaining the position where Hz is not detected. Moreover, the ground fault point S can be detected by detecting the position where the magnetic field H (FIG. 5) generated around the submarine cable 1 disappears.

Further, instead of the means for towing the magnetic sensor 4 by the mother ship 5 as described above, an underwater swimming type robot 7 as shown in FIG. 8 can be used. That is, as shown in FIG. 8, brackets 7a provided on the left and right of the robot 7
The magnetic sensors 4z ₁ and 4z ₂ for detecting the vertical component Hz of the magnetic field H are attached to the tip of, and propelled by the propulsion device 7b.

When the robot 7 runs along the submarine cable 1 as shown in FIG. 9, the magnetic sensor 4
The vertical components Hz ₁ and Hz ₂ detected by z ₁ and 4z ₂ are the robot 7
Is inconsistent depending on the horizontal distance ΔY from the submarine cable 1, that is, the difference ΔHz between the two detection values is detected. Therefore, if the robot 7 is moved horizontally and sailed so that the difference ΔHz becomes zero, the robot 7 can run almost directly above the submarine cable 1, that is, the cable tracking can be performed.

[0010]

By the way, many submarine cables are laid in places where the tidal current is fast such as the strait. Therefore, in the underwater swimming robot 7 shown in FIG. 9, the detection accuracy is improved if the distance y between the left and right magnetic sensors 4z ₁ and 4z ₂ is increased to some extent, but the bracket 7a protruding left and right is affected by the tidal current. Rolling is easy to occur. When the underwater swimming robot 7 rolls in this way, the heights Z of the left and right magnetic sensors 4z ₁ and 4z ₂ become non-uniform, and accurate vertical components Hz ₁ and Hz ₂ cannot be detected, so that the submarine cable 1 cannot be detected. There is a problem that an error occurs in position detection. Therefore, in order to make the underwater swimming type robot that performs cable tracking practical, it is desirable to first make it compact and to further improve the tidal current resistance performance. The present invention has been made in view of the above problems, and an object thereof is to provide a cable tracking device including a magnetic sensor that can be miniaturized.

[0011]

SUMMARY OF THE INVENTION To achieve the above object, the cable tracking device of the present invention has a magnetic sensor for detecting a magnetic field generated by a current flowing through an electric cable buried in the seabed, and a magnetic sensor for detecting the magnetic field. The magnetic sensor is composed of a plurality of sensitivity directivity type magnetic sensors, and the magnetic detection unit is attached in three directions of a vertical component of the magnetic field and two horizontal components. A means for constantly orienting the magnetic detection unit for detecting the vertical component of the magnetic field in the vertical component detection direction, and a signal processing means for calculating the direction of the cable with respect to the robot from the signal output from each magnetic sensor. .

As the magnetic sensor used in the present invention, for example, a fluxgate type magnetic sensor is preferable because it is small in size, has sensitivity directivity, and can detect a direct current component such as geomagnetism. It is not limited to this. There is no particular limitation on the control means for always directing the magnetic sensor for detecting the vertical component of the magnetic field in the vertical direction. For example, even if the magnetic sensor is suspended from the robot by a universal joint and the posture of the robot changes, a means for constantly orienting the magnetic sensor in the vertical direction or a means by a gyro may be used. The posture of the underwater swimming type robot may be controlled.

[0013]

The magnetic sensor for detecting the vertical component of the magnetic field generated by the current flowing through the submarine cable and the horizontal component perpendicular to each other detects the magnetic field produced by the alternating current flowing through the submarine cable by vector decomposition into three components. Since it can be installed in one place to detect the magnetic field components in three directions, it can be downsized and the influence of tidal current can be minimized. ~ (6)
As understood from the equation, the position of the submarine cable can be detected without being affected by the height of the robot from the seabed. That is, the angle θ shown in FIG. 6A can be obtained from the following equation (4).

[0014] Further, as understood from FIG. 10, the horizontal angle φ between the traveling direction of the robot 7 of the magnetic field H at the observation point P and the submarine cable 1
Is

[0015] It is represented by. Here, hx is the robot 7 having the horizontal component Hy.
Is a component in the traveling direction, and hy represents a component of a horizontal component Hy orthogonal to this, and the laying direction of the cable 1 seen from the robot 7 can be known from this equation (5). Furthermore, H
The relationship between y and hy is shown in Fig. 10.

[0016] The angle θ can be calculated by substituting equation (6) into equation (4).
Can be asked. That is, in FIG. 6A, if θ is substantially zero, the robot 7 is located directly above the submarine cable, and if θ> 0, the robot 7 is located away from the right side of the submarine cable, and θ <0. If so, it can be seen that the robot 7 is located on the left side of the submarine cable and apart from it. In FIG. 6A, the magnetic field strength H observed by the robot 7 is the height Z from the submarine cable of the robot 7.
Although it depends on the altitude Z, since both equations (4) and (5) are dimensionless values represented by a ratio, they are not affected by the altitude Z.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail by way of an embodiment with reference to the accompanying drawings. As shown in FIG. 1, the magnetic sensor 4 used in this embodiment includes three magnetic sensors 4x, 4y, 4z (only the coil portion is shown) such as a fluxgate type magnetic sensor and a robot (not shown in FIG. 1). The magnetic sensor 4x matches the maximum sensitivity direction with the x-axis, the magnetic sensor 4y matches the maximum sensitivity direction with the y-axis, and the magnetic sensor 4z vertically downwards. They are attached so that they are aligned with the z-axis facing each other and close to each other. Therefore, the detection unit of the magnetic sensor 4 is downsized, and the robot can be downsized. FIG. 2 shows the relationship between the sensitivity h of the flux gate type magnetic sensor and the relative angle Ω of the magnetic field.

The magnetic sensor container 4a containing the three magnetic sensors 4x, 4y, 4z is suspended from the robot 7 via a universal joint 8 composed of a gimbal mechanism or the like. Therefore, even if the robot 7 rolls or pitches and the posture changes to some extent, the magnetic sensor container 4a can always be oriented in a prescribed direction. Next, the outline of the signal processing means 9 used in this embodiment will be described with reference to FIG. That is, the signal processing means 9 includes a filter block 9a, a signal amplification block 9b, and a calculation block 9.
Each block of c is provided.

The filter block 9a has a band
Pass filters BFx, BFy, BFz and low-frequency pass type low-pass filters
Filter LF_E,LF₂Is equipped with a bandpass filter
BFx, BFy, BFz are magnetic sensors 4x, 4y, and
Signal i output by 4z_X, I _y, I_ZCable track
The frequency components used for king are discriminated and selectively passed.
It is a filter. Also, low-pass filter LF_E,LF₂
Are signals output by the magnetic sensors 4x and 4y, respectively.
i_X, I_yGeomagnetic component i consisting of the low frequency component of_1,i ₂To
It is configured to selectively pass.

Band pass filters BFx, BFy, BFz
And the respective signals i _X , which are output from the low-pass filters LF _{1 and} LF ₂ ,
i _y , i _Z , i ₁ , and i ₂ are amplified by the signal amplification block 9b, and then the computation block 9c applies the equations (4) and (5) and the equation (4) for the geomagnetic component. The calculation is performed to calculate the horizontal angle θ, the vertical angle φ, and the geomagnetic azimuth β indicating the posture of the robot 7 with respect to the submarine cable 1. These angle signals θ, φ, β are used for the cable tracking control of the robot 7, and the signals i _X , i _y , i _{Z are used.}
The ground fault point S can be known by detecting the position where is disappeared.

[0021]

As described above, the cable tracking device of the present invention uses the magnetic sensor having the sensitivity directivity and detects the vertical component and the two horizontal components of the magnetic field generated by the alternating current flowing through the cable. Since the cable position is calculated, even if a plurality of magnetic sensors that detect the magnetic field components in the three directions are arranged close to each other, the occurrence of a cable position detection error can be prevented.
Therefore, the magnetic sensor can be miniaturized, and the influence of the tidal current on the magnetic sensor and the underwater swimming robot equipped with the magnetic sensor can be minimized. Therefore, it is possible to remarkably improve the work efficiency and the detection accuracy of the confirmation of the laying position of the submarine cable and the search of the ground fault point due to the accident of the submarine cable.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating an outline of a sensitivity directional magnetic sensor used in an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the magnetic field of the magnetic sensor shown in FIG. 1 and the relative angle of the sensitivity directivity of the magnetic sensor.

FIG. 3 is an explanatory diagram showing a state in which the magnetic sensor shown in FIG. 1 is attached to a robot.

FIG. 4 is a block circuit diagram showing an outline of signal processing means used in the embodiment.

FIG. 5 is an explanatory diagram of a conventional cable tracking method.

6A is an explanatory view of a state of a magnetic field generated at the time of cable tracking according to a cross section taken along line VI-VI of FIG. 5, and B is a graph showing a relationship between a horizontal direction component of the magnetic field and a horizontal distance from the cable. , C are graphs showing the relationship between the vertical component of the magnetic field and the horizontal distance from the cable.

FIG. 7 is a plan view of FIG. 5 showing a trajectory along which a magnetic sensor travels.

FIG. 8 is a plan view showing an outline of an underwater swimming type robot used for conventional cable tracking.

9 is a vertical cross-sectional view illustrating the relationship between the vertical direction component of the magnetic field detected by the underwater swimming robot of FIG. 8 and the robot position.

FIG. 10 is a plan view of FIG. 9.

[Explanation of symbols]

1 Submarine Cable (Electric Cable) 2 Ground Electrode 3 AC Power Supply 5 Mother Ship 4 Magnetic Sensor 4x Magnetic Sensor 4y Magnetic Sensor 4z Magnetic Sensor 6 Seabed 7 Robot 8 Universal Joint 9 Signal Processing Means 9a Filter Block 9b Signal Amplification Block 9c Computation Block BFx Band Pass filter BFy Band pass filter BFz Band pass filter H Magnetic field Hx Horizontal component Hy Horizontal component Hz Vertical component S Ground fault point β Geomagnetic direction θ angle φ angle

Claims (1)

[Claims] 1. A magnetic sensor for detecting a magnetic field generated by a current flowing through an electric cable buried in the seabed, and an underwater swimming robot equipped with the magnetic sensor, wherein the magnetic sensor comprises a plurality of sensitivity directional magnetic sensors. And a means for orienting the magnetic detection part for detecting the vertical component of the magnetic field in the vertical component detection direction, the magnetic detection part being attached in the three directions of the vertical component of the magnetic field and the horizontal component in two directions. , A cable tracking device provided with signal processing means for calculating the direction of the cable with respect to the robot from the signal output from each magnetic sensor.