JP4259327B2 - Magnetic measurement method for ships - Google Patents

Description

  The present invention relates to a ship's magnetic measurement method necessary for performing a ship's magnetic reduction process.

Generally, a ship emits a ship's magnetic field. The hull magnetism, as shown in FIG. 7, the hull structure, VM (vertical component of ship's magnetization: vertical), LM (longitudinal comp on ent of ship's magnetization: stern direction), AM (athwardship It is distributed in three orthogonal components of component of ship's management.

Further, each of the magnetism PM (perm a nent ship's magnetization : permanent magnet) and IM: constructed from (induced ship's magnetization induced magnetism) and magnetostatic emanating from the hull magnetism, the vertical component of a permanent magnetic PVM, stern direction component PLM, consists of a left-right outboard direction PAM, induced magnetism in the vertical direction component IVM, stern direction component ILM, the port and starboard direction component IAM.

Such hull magnetism is desirable to be small in order to avoid thunder and the like while navigating a ship. Therefore, the ship is provided with a degaussing coil, and a predetermined current for canceling the ship magnetism is applied to the degaussing coil to demagnetize it. In order to perform this type of demagnetization, it is necessary to measure the ship's hull magnetism. As a method for measuring the magnetic field of a ship, conventionally, a method has been used in which a plurality of magnetic sensors are arranged in a row on the sea floor and the ship's magnetic force is measured by navigating or mooring the ship over the magnetic sensor. (For example, refer to Patent Document 1).
JP 60-182706 A

  The conventional ship magnetic field measurement method described above cannot separate the stern direction permanent magnetic PLM and the vertical direction magnetic VM for measuring the magnetic field under the ship. The magnetic field obtained by this ship magnetic field measurement method is defined as an M coil. When the LP coil is energized and demagnetized, for example, the fore-and-aft permanent magnetic PLM is demagnetized by the M (vertical) coil and the vertical magnetic VM is demagnetized by the LP (horizontal) coil. This means that demagnetized parts are demagnetized, that is, they are magnetized, and there is a problem that the degree of magnetic reduction of a ship is not the best when viewed from a distance. .

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a method for measuring the magnetic field of a ship that can measure the ship's stern direction permanent magnetic PLM and the perpendicular magnetic VM separately.

The method for measuring a magnetic field of a ship according to the present invention measures the three-axis magnetic field on the left and right sides of the ship and the three-axis magnetic field below the bottom of the ship, with the bow of the ship facing north and south. The value obtained by adding the measured value Hx of the right three-axis magnetic field and the measured value Hx of the left three-axis magnetic field when the bow is facing in the north direction and dividing by 2 is calculated as the stern direction magnetism LM _N The value obtained by adding the measured value Hx of the right three-axis magnetic field and the measured value Hx of the left three-axis magnetic field when the bow is facing in the south direction and dividing by 2 is obtained. A value obtained by subtracting the LM _S from the LM _N and dividing by 2 is defined as a magnetic LM _S, and a value obtained by dividing the LM _S by a permanent magnetic PLM in the fore and aft direction. , PL calculated from the left and right triaxial magnetic fields A dipole value is determined so that an error from the M waveform (Hx, Hy) is minimized, and a PLM waveform (Hx, Hy) below the ship bottom is calculated from the multi-dipole value, and the PLM waveform (Hx, Hy) is calculated. ) Is subtracted from the waveform of the measured value PLM + VM of the three-axis magnetic field under the ship bottom so that the PLM and the perpendicular magnetic VM are separated .

  In the ship magnetic measurement method according to the present invention, the three-axis magnetic fields on both the left and right sides are measured by a magnetic measuring device fixed to the left and right sides of the ship, and the three-axis magnetic field below the bottom of the ship is a magnetic sensor fixedly installed on the sea floor. It can be measured in rows.

  In the ship magnetic measurement method according to the present invention, the three-axis magnetic fields on both the left and right sides are mounted on the vehicle by using the mounted vehicle and guiding the vehicle from the measured ship to travel around the measured ship. It can also be measured with an axial magnetic field sensor.

  Further, in the ship magnetic measurement method of the present invention, a three-axis magnetic field is connected in cascade, suspended on a measurement buoy, the measurement buoy with the three-axis magnetic field sensor is suspended in water, and the ship to be measured is run in the vicinity. Thus, the three-axis magnetic field on the left and right sides can be measured.

  In the ship magnetic field measurement method of the present invention, the three-axis magnetic fields on both the left and right sides may be measured by a magnetic sensor located on the side of the ship in the magnetic sensor group fixedly installed on the seabed.

According to the invention, the bow based on the left and right three-axis magnetic field measurements Hx when facing north calculates the stern direction magnetic LM _N, the left and right when the bow is facing south direction Calculate the stern direction magnetic LM _S based on the measured value Hx of the three-axis magnetic field, subtract LM _S from LM _N and divide by 2 to calculate the stern direction permanent magnetic PLM. Modeling, calculating the PLM waveform under the ship bottom, and subtracting this calculated PLM waveform from the measured PLM + VM waveform of the 3-axis magnetic field under the ship bottom separates the PLM and the vertical magnetic VM. By using the obtained stern direction permanent magnetism PLM and perpendicular direction magnetism VM individually for demagnetization, it is possible to contribute to making the magnetic reduction of the ship suitable.

  Hereinafter, the present invention will be described in more detail with reference to embodiments. FIG. 1 is a view showing the arrangement of a three-axis magnetic sensor for explaining an embodiment of the present invention. In FIG. 1, a three-axis magnetic sensor 2 is arranged on the right side of the ship 1 to be measured, a three-axis magnetic sensor 3 is arranged on the left side of the ship 1 to be measured, and three axes are arranged on the sea floor under the keel of the ship 1 to be measured. A magnetic sensor 4 is arranged. Here, the triaxial magnetic sensors 2 and 3 are measured as continuous points by a vehicle to be described later, for example.

  FIG. 2 shows an example in which the magnetic field from the measured ship 1 is measured by the left and right three-axis magnetic sensors 2 and 3 with the bow of the measured ship 1 directed in the N (north) direction. In FIG. 2, the solid line waveform a1 shown on the left side shows the Hx component measured by the three-axis sensor 3 of the bow-direction magnetic LM of the ship 1 to be measured, and the broken line waveform b1 shown on the left side of the ship 1 is The Hx component by the three-axis sensor 3 of the left and right saddle direction magnetic AM is shown. The solid line waveform a2 shown on the right side shows the Hx component measured by the three-axis sensor 2 of the stern direction magnetic LM of the ship 1 to be measured, and the broken line waveform b2 shown on the right side shows the left and right side of the ship 1 to be measured. The Hx component measured by the three-axis sensor 2 of the directional magnetic AM is shown.

  In FIG. 2, the left waveform a1 and the right waveform a2 of the stern direction magnetism LM are the same polarity waveforms, and the left waveform b1 and the right waveform b2 of the left and right direction magnetism AM are waveforms having opposite polarities. Therefore, the LM component is obtained by adding the Hx component of the triaxial sensor 2 and the Hx component of the triaxial sensor 3 and dividing by 2, and the Hx component of the triaxial magnetic sensor 2 is obtained from the Hx component of the triaxial magnetic sensor 2. By subtracting the component and dividing by 2, the AM component is obtained. Thereby, the fore-and-aft direction magnetism LM and the left-and-right direction magnetism AM can be separated.

  Next, FIG. 3 shows an example in which the magnetic field from the measured ship 1 is measured by the left and right three-axis magnetic sensors 2 and 3 with the bow of the measured ship 1 directed in the S (south) direction. In FIG. 3, a solid line waveform a <b> 1 shown on the left side shows the Hx component measured by the three-axis sensor 3 of the bow direction magnetic LM of the ship 1 to be measured, and a broken line waveform b <b> 1 shown on the left side of the ship 1 is The Hx component by the three-axis sensor 3 of the left and right saddle direction magnetic AM is shown. The solid line waveform a2 shown on the right side shows the Hx component measured by the three-axis sensor 2 of the stern direction magnetic LM of the ship 1 to be measured, and the broken line waveform b2 shown on the right side shows the left and right side of the ship 1 to be measured. The Hx component measured by the three-axis sensor 2 of the directional magnetic AM is shown.

  In FIG. 3, the left waveform a1 and the right waveform a2 of the forehead direction magnetic LM are of the same polarity, and the left waveform b1 and the right waveform b2 of the left and right direction magnetism AM are waveforms of opposite polarity. Therefore, the LM component is obtained by adding the Hx component of the triaxial sensor 2 and the Hx component of the triaxial sensor 3 and dividing by 2, and the Hx component of the triaxial magnetic sensor 2 is obtained from the Hx component of the triaxial magnetic sensor 2. By subtracting the component and dividing by 2, the AM component is obtained. Thereby, the fore-and-aft direction magnetism LM and the left-and-right direction magnetism AM can be separated.

  In FIG. 3, since the directions of PLM and ILM are opposite, the stern direction magnetic LM is smaller than in the case of FIG. 2 (in the case of FIG. 2, PLM and ILM are in the same direction). Therefore, by adding the stern direction magnetic LM obtained by the method of FIG. 2 and the stern direction magnetic LM obtained by the method of FIG. 3 and dividing by 2, or subtracting and dividing by 2, the PLM and An ILM is obtained and the PLM can be isolated.

  Moreover, since VM + PLM is obtained for Hz (Hx) by the triaxial magnetic sensor 4 under the keel, the PLM calculated from the outputs of the left and right triaxial magnetic field sensors 2 and 3 is modeled and converted into a waveform under the keel. , VM and PLM can be separated.

  In the above embodiment, a specific installation example of the three-axis sensors 2, 3, 4 will be described. FIG. 4 shows a case where the three-axis magnetic sensor 4 is installed as a sensor array on the sea floor. The ship 1 to be measured passes between the three-axis magnets 2 and 3 to perform measurement. This method is highly feasible in terms of configuration, and the three-axis magnetic sensors 2 and 3 are the navigation targets of the ship to be measured.

  In the embodiment shown in FIG. 4, the three-axis magnetic sensors 2 and 3 are floated by buoys. Alternatively, the three-axis magnetic sensors 2 and 3 may be installed on the sea floor directly under the buoys. good. That is, the three-axis magnetic sensors 2 and 3 for measuring the magnetism on both the left and right sides of the ship are arranged at the left and right ends of the three-axis magnetic sensor array 4 installed on the seabed. Since it is provided on the side of the ship, the horizontal component can be separated, and if the water depth << side distance, it is sufficiently practical.

  In FIG. 5, a three-axis magnetic sensor is mounted on the underwater vehicle 5, and the vehicle 5 is guided from the ship 1 to be measured for measurement. This method does not require a sensor installation process and can be expected to shorten the measurement time. Further, the ship 1 to be measured can perform measurement without sailing. In FIG. 6, a plurality of three-axis magnetic sensors 2 (3) are hung on a measurement buoy 6, thrown, and floated in the sea. The measurement is performed by the ship to be measured running in the vicinity of the measurement buoy 6. This method can shorten the sensor installation process time.

  Next, the hull magnetic field measurement system used in the above embodiment will be described. FIG. 8 is a block diagram showing the configuration of the hull magnetic field measurement system. This hull magnetic field measurement system is composed of a data processing device 10, three-axis magnetic sensors 2, 3, 4 connected to the data processing device 10, and a bow direction sensor 11. The data processing apparatus 10 includes a sensor I / F 12, a CPU 13, a memory 14, a display unit 15, and a storage unit 16. The hardware configuration itself is not particularly different from a well-known data processing apparatus. The data processing device 10 is installed on a ship or on land. The triaxial sensors 2, 3, and 4 are those shown in FIG. The bow direction sensor 11 is a sensor that detects whether the bow of the ship 1 to be measured is facing the N (north) direction or the S (south) direction. The bow direction sensor 11 may be omitted as the measurer inputs the direction.

  With reference to the flowchart shown in FIG. 9, the processing operation when measuring the hull magnetic field by this hull magnetic field measurement system will be described. After the process starts, first, in step ST1, it is determined by the bow direction sensor 11 whether the bow direction of the ship 1 to be measured is facing N. When it is confirmed that the bow is facing N, the process proceeds to step ST2. In step ST2, the magnetic field is measured by the three-axis magnetic sensors 2, 3, and 4 with the bow of the ship 1 to be measured facing in the N direction. Next, in step ST3, each measured value is stored in the memory 14. Next, the process proceeds to step ST4.

  In step ST4, it is determined whether or not the bow of the ship 1 to be measured is facing the S direction. When the direction of the ship to be measured is changed and turned to the S direction, the process proceeds to step ST5. In step ST5, the magnetic field is measured by the three-axis magnetic sensors 2, 3, and 4 with the bow of the ship 1 to be measured oriented in the S direction. Next, in step ST6, each measured value is stored in the memory 14. Subsequently, the process proceeds to step ST7.

In step ST7, the measured values Hx of the triaxial magnetic sensor 2 and the measured values Hx of the triaxial magnetic sensor 3 when the bow is directed in the N direction are read from the memory 14, added, and divided by two. calculated, and the calculated and obtained value as stern direction magnetic LM _N, stored in the memory 14. Next, the process proceeds to step ST8. In step ST8, each measurement value Hx of the three-axis magnetic sensor 3 read out from the memory 14 is subtracted from each measurement value Hx of the three-axis magnetic sensor 3, and divided by two. as-direction magnetic AM _N, and stores in the memory 14. Subsequently, the process proceeds to step ST9.

In step ST9, each measured value Hx of the triaxial magnetic sensor 2 and the measured value Hx of the triaxial magnetic sensor 3 when the bow is directed in the S direction are read from the memory 14, added, and divided by two. calculated, and the calculated and obtained value as stern direction magnetic LM _S, stored in the memory 14. Next, the process proceeds to step ST10. In step ST10, each measurement value Hx of the triaxial magnetic sensor 3 measured in the bow direction S read from the memory 14 is subtracted from each measurement value Hx of the triaxial magnetic sensor 3, and divided by 2. the value obtained as a lateral outboard direction magnetic AM _S, stored in the memory 14. Next, the process proceeds to step ST11.

In step ST11, LM _N and LM _S stored in the memory 14 are read out, added together, divided by 2, and the calculated ILM (inductive magnetism in the stern direction) is stored in the memory 14. . Next, the process proceeds to step ST12. In step ST 12, the LM _S is subtracted from the LM _N read from the memory 14, divided by 2, and stores the calculated-obtained PLM (stern direction of the permanent magnetic).

  Next, in order to separate PLM and VM (vertical magnetism), a multi-dipole model consisting of a plurality of dipoles is assumed per ship 1, and the error from the left and right PLM waveforms (Hx, Hy) is minimized. The dipole value is determined so that From this multi-dipole value, a PLM waveform (Hx, Hy) below the ship bottom is calculated and subtracted from the measured PLM + VM remaining waveform to separate the PLM and VM remaining.

It is a figure which shows arrangement | positioning of the triaxial magnetic sensor explaining one Embodiment of this invention. It is a figure explaining the magnetic measurement waveform at the time of turning the bow of a to-be-measured ship to the north in the embodiment. It is a figure explaining the magnetic measurement waveform at the time of turning the bow of a to-be-measured ship to the south in the embodiment. It is a figure explaining one of the specific examples of the triaxial magnetic sensor of right-and-left installation used in the embodiment. It is a figure explaining the other specific example of the triaxial magnetic sensor of right-and-left installation used in the embodiment. It is a figure which shows the other specific example of the triaxial magnetic sensor of right-and-left installation used in the embodiment. It is a figure explaining the hull magnetism emitted from a ship. It is a block diagram which shows the structure of the hull magnetic field measurement system used by the said embodiment. It is a flowchart for demonstrating the measurement process of the hull magnetic field measurement system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ship to be measured 2 Triaxial magnetic sensor for right 3 Triaxial magnetic sensor for left 4 Triaxial magnetic sensor for ship bottom 5 Underwater vehicle 6 Measurement buoy 10 Data processor 11 Bow direction sensor 12 Sensor I / F
13 CPU
14 memory 15 display unit 16 recording unit

Claims (5)

With the bow of the ship facing north and south , measure the three-axis magnetic field on the left and right sides of the ship and the three-axis magnetic field below the bottom of the ship , respectively . the value obtained by dividing by 2 by adding the measured values Hx three-axis magnetic field measurements Hx and the left of the right three-axis magnetic field and stern direction magnetic LM _N, the bow is facing south direction the value obtained by dividing by adding to 2 the measured values Hx measurements Hx and left three-axis magnetic field of the right three-axis magnetic field and stern direction magnetic LM _S when you are, the from the LM _N The value obtained by subtracting LM _S and dividing by 2 is defined as the stern direction permanent magnetic PLM, assuming a multi-dipole model consisting of a plurality of dipoles per ship, and calculated from the left and right triaxial magnetic fields. Error with PLM waveform (Hx, Hy) The dipole value is determined so as to be small, the PLM waveform (Hx, Hy) below the ship bottom is calculated from the multi-dipole value, and the PLM waveform (Hx, Hy) is measured for the three-axis magnetic field below the ship bottom. A ship magnetic measurement method, characterized in that the PLM and the perpendicular magnetic VM are separated by subtracting from the waveform of the value PLM + VM .   The three-axis magnetic field on both the left and right sides is measured with a magnetic measuring device that is fixed to the left and right sides of the ship, and the three-axis magnetic field under the bottom of the ship is measured with a group of magnetic sensors fixedly installed on the sea floor. The ship magnetic field measuring method according to claim 1.   The three-axis magnetic field on both the left and right sides is measured by a magnetic sensor located laterally with respect to the ship in the group of magnetic sensor arrays fixedly installed on the sea floor, and the three-axis magnetic field below the ship bottom is fixedly installed on the sea floor. 3. The ship magnetic measurement method according to claim 2, wherein the measurement is performed by a magnetic sensor array group.   The three-axis magnetic field on both the left and right sides is measured by using a mounted vehicle, guiding the vehicle from the ship to be measured, and traveling the vehicle around the ship to be measured, using the mounted three-axis magnetic field sensor. The ship magnetic field measuring method according to claim 1.   A 3-axis magnetic field is connected in cascade, suspended on a measurement buoy, a measurement buoy with this 3-axis magnetic field sensor is suspended in water, and the vessel to be measured is run in the vicinity to measure the 3-axis magnetic field on the left and right sides. The ship magnetic field measuring method according to claim 1, wherein:

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