JP3743054B2 - Marine structure anti-vibration equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vibration reducing device for an offshore structure used to suppress the swinging of offshore structures such as ships, barges, and other floating bodies.
[0002]
[Prior art]
As a conventional vibration reduction device in a ship, as shown in FIG. 4, there is known one in which a movable mass c reciprocates along an arcuate guide b fixed at an appropriate position of a ship a. The design is such that the phase is delayed by about 90 ° in the same cycle as the assumed swing of the ship a, and the passive mass is passively resonated with the swing of the ship a, or is movable. As a hybrid system in which a motor (not shown) is installed in the mass c and reciprocates while being actively controlled, swinging of the ship a is suppressed.
[0003]
[Problems to be solved by the invention]
However, in the case of the passive system in which the movable mass c is resonated passively, the natural period is determined once the design is made. Therefore, the oscillation period of the ship a depends on the loading state of the load and the ocean. If it changes due to wave height, etc., there is a problem that the effect of reducing the vibration is reduced.
[0004]
On the other hand, in the case of a hybrid system in which the movable mass c is reciprocated by actively controlling it, it is possible to cope with a change in the oscillation cycle of the ship a, but the inrush current to the motor is large. Therefore, there was a problem that the power consumption increased.
[0005]
In addition, as shown by a two-dot chain line in the figure, it is necessary to draw the power cable d into the movable mass c in order to supply power. Generally, this type of power cable d draws a curve and has a movable mass c. Since the power cable d is held by the outer skin so as to be pulled in, and follows the movement of the movable mass c while changing the bending position, there is a problem that the deterioration of the power cable d progresses quickly and the life is short. It was.
[0006]
Furthermore, mechanically reciprocating the movable mass c with a motor causes a complicated structure, which causes a problem that a failure is likely to occur and the burden of maintenance work increases.
[0007]
The present invention has been made in view of the above circumstances, and can be adapted to changes in the oscillation cycle of marine structures such as ships, and also requires less power consumption, and the burden of maintenance work is reduced. The purpose is to provide a device for reducing the number of offshore structures.
[0008]
[Means for Solving the Problems]
The present invention comprises a pair of liquid bath which is fixed to the marine structures by storing liquid having conductivity, is formed a bottom portions of the respective liquid bath as a rectangular pipe made of communicating with and two sets of opposing surfaces A communication pipe, a pair of permanent magnets arranged on the outside of one opposing surface of the communication pipe so as to form magnetic lines of force in a direction substantially perpendicular to the flow direction of the communication pipe , and the communication pipe A pair of electrodes respectively disposed inside the other facing surface of the communication pipe so that a direct current can flow in a direction substantially perpendicular to the flow path direction and substantially perpendicular to the direction of the magnetic force lines by the permanent magnet. Oscillating detection means for detecting oscillating of the offshore structure, a flow meter for measuring the flow rate of the liquid flowing through the communication pipe, polarity reversal and current of DC current fed from a power source to the electrodes An inverter that increases or decreases a value and the swing detection means And the flow rate signal from the flow meter, the inverter between the liquid tanks corresponds to the oscillation cycle of the offshore structure and has a phase delay of about 90 °. And a control device for controlling the liquid to apply an appropriate Lorentz force to the liquid.
[0010]
Thus, when the offshore structure is oscillating, the liquid in each liquid tank is passively reciprocally oscillated at a predetermined period (period set at the time of design) while flowing through the communication pipe. At this time, the inverter is controlled by the control device based on the swing signal from the swing detection means and the flow rate signal from the flowmeter, and the swing of the liquid between the liquid tanks is the period of the swing of the offshore structure. The polarity of the direct current supplied from the power source and the increase / decrease of the current value are applied to the electrodes so as to correspond to the phase delay of about 90 °.
[0011]
That is, when a direct current is passed between the electrodes through a liquid flowing in the communication pipe in a state where a magnetic field is formed in the communication pipe by a permanent magnet, the direction of the magnetic field is perpendicular to Fleming's left-hand rule. In addition, a Lorentz force is generated in the direction of the flow path of the communication pipe, which is also perpendicular to the direction of DC current flow. At this time, if the polarity of the DC current fed from the power source to the electrode is reversed, the DC current The direction of Lorentz force can be reversed by changing the flow direction, and if the current value is increased or decreased, the magnitude of the Lorentz force can be adjusted as appropriate. By applying a Lorentz force to the liquid in an appropriate direction and magnitude, it becomes possible to promote or suppress the oscillation of the liquid to cope with a change in the oscillation cycle of the offshore structure. It is.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0013]
1 to 3 show an example of an embodiment for carrying out the present invention. As shown in FIG. 1, a pair of liquid tanks 2 and 2 storing a liquid 1 having conductivity such as seawater are marine structures. The liquid tanks 2 and 2 are fixed to both strings, respectively, and the bottoms of the liquid tanks 2 and 2 are communicated with each other by a communication pipe 4 extending in the horizontal direction. An opening 5 for allowing the upper air to freely enter and exit is provided.
[0014]
As shown in FIG. 2, the communication pipe 4 is formed as a rectangular pipe having two sets of opposing surfaces, and opposite magnetic poles are provided on the outer sides of one opposing surface facing the vertical direction of the communication pipe 4. A pair of facing permanent magnets 6 and 6 are arranged to face each other with the communication pipe 4 interposed therebetween, and magnetic lines of force are formed downward in the communication pipe 4 as indicated by an arrow X in FIG. is there.
[0015]
In addition, a pair of electrodes 9 are opposed to each other on the inner side of the other facing surface facing the horizontal direction perpendicular to the flow direction of the communication pipe 4 (left and right direction in FIGS. 1 and 2). Thus, a direct current can be made to flow in the horizontal direction perpendicular to the flow path direction of the communication pipe 4 by using the liquid 1 as an energization medium.
[0016]
As shown in FIG. 3, a DC power supply 7 is connected to the electrodes 9 and 9 via an inverter 8, and the inverter 8 is connected to the electrodes 9 and 9 with a polarity of a DC current fed from the power supply 7. The inversion and increase / decrease of the current value can be performed, and the operation is controlled by a control signal 11 from the control device 10.
[0017]
The control device 10 includes an angular velocity signal 13 (oscillation signal) from an angular velocity meter 12 (oscillation detection means) and a flow rate signal 15 from a flow meter 14 that measures the flow rate of the liquid 1 flowing through the communication pipe 4. And the oscillation of the liquid 1 between the liquid tanks 2 and 2 corresponds to the oscillation cycle of the ship 3 based on the angular velocity signal 13 and the flow rate signal 15, respectively. The inverter 8 is controlled so as to have a phase delay of about 90 °, and an appropriate Lorentz force is applied to the liquid 1.
[0018]
In the present embodiment, the marine structure that is the object of vibration reduction is exemplified as the ship 3, so the existing angular velocity meter 12 provided in the ship 3 is used as the swing detection means. Needless to say, the swing detection means may be provided separately.
[0019]
Thus, when the ship 3 is oscillating, the liquid 1 in each of the liquid tanks 2 and 2 is passively reciprocated at a predetermined period (period set at the time of design) while flowing through the communication pipe 4. At this time, the control device 10 controls the inverter 8 based on the angular velocity signal 13 from the angular velocity meter 12 and the flow rate signal 15 from the flow meter 14, and the fluctuation of the liquid 1 between the liquid tanks 2 and 2 is controlled. The polarity of the direct current fed from the power source 7 and the increase or decrease of the current value are performed on the electrodes 9 and 9 so that the movement corresponds to the oscillation cycle of the ship 3 and has a phase delay of about 90 °. .
[0020]
That is, if a direct current is passed between the electrodes 9 and 9 through the liquid 1 flowing through the communication pipe 4 in a state where a magnetic field is formed in the communication pipe 4 by the permanent magnets 6 and 6, Fleming According to the left-hand rule, a Lorentz force is generated in the direction of the flow path of the communication tube 4 that is perpendicular to the direction of the magnetic field lines and also perpendicular to the direction of direct current flow. If the polarity of the DC current to be fed is reversed, the direction of the Lorentz force can be reversed by changing the flow direction of the DC current, and if the current value is increased or decreased, the magnitude of the Lorentz force is appropriately adjusted. By adjusting the Lorentz force to the liquid 1 flowing through the communication pipe 4 in an appropriate direction and magnitude, the liquid 1 is promoted or suppressed to be oscillated. Change of oscillation cycle of 3 It become possible to correspond to.
[0021]
For example, as shown in FIG. 2, when the direction of the magnetic lines of force of the permanent magnets 6 and 6 is downward as indicated by an arrow X, the rear electrode 9 is directed toward the front electrode 9 as indicated by an arrow Y. When a direct current is applied, a Lorentz force is generated toward the right side as indicated by an arrow Z. When a direct current is applied in a direction opposite to the arrow Y, a Lorentz force is generated toward the left side, which is the opposite direction of the arrow Z. .
[0022]
Therefore, according to the above-described embodiment, even if the rocking cycle of the ship 3 changes depending on the loaded state of the cargo, the wave height of the ocean, etc., the rocking of the liquid 1 between the liquid tanks 2 and 2 Therefore, the maximum vibration reduction effect can always be obtained.
[0023]
Further, the rocking of the liquid 1 between the liquid tanks 2 and 2 is basically passively performed by the rocking of the ship 3, and this is promoted or suppressed by the Lorentz force to thereby rotate the rocking period of the ship 3. The power required to generate the Lorentz force is negligible and does not require a large inrush current as in the case of using a motor. The amount can be greatly reduced.
[0024]
In addition, since a mechanically movable part is not required and the structure can be extremely simple, it can be used continuously over a long period of time, and the burden of maintenance work can be significantly reduced.
[0025]
Note that the marine structure vibration reducing device of the present invention is not limited to the above-described embodiment, and the arrangement relationship between the permanent magnets and the electrodes may be the reverse arrangement of the illustrated example, and the communication pipe Is not necessarily a rectangular tube, the liquid is not limited to seawater, the marine structure may be other than a ship, and other various modifications may be made without departing from the scope of the present invention. Of course.
[0026]
【The invention's effect】
According to the above-described apparatus for reducing a marine structure of the present invention, various excellent effects as described below can be obtained.
[0027]
(I) Even if the rocking cycle of the offshore structure changes, control is performed so that the rocking of the liquid between the liquid tanks corresponds to the rocking cycle of the offshore structure and has a phase delay of about 90 °. Can always obtain the maximum vibration reduction effect.
[0028]
(II) The oscillation of the liquid between the liquid tanks is basically carried out passively by the oscillation of the offshore structure, and this is promoted or suppressed by the Lorentz force, and the oscillation cycle of the offshore structure is reduced. Since it is only adapted to changes, the power required to generate the Lorentz force is negligible, and it does not require a large inrush current as in the case of using a motor, etc. Can be greatly reduced.
[0029]
(III) Since a mechanically movable part is not required and the structure can be extremely simple, it can be used continuously over a long period of time, and the burden of maintenance work can be significantly reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an embodiment of the present invention.
FIG. 2 is a perspective view showing details of the communication pipe of FIG. 1;
FIG. 3 is a conceptual diagram showing a control system in an example of an embodiment of the present invention.
FIG. 4 is a schematic view showing a conventional example.
[Explanation of symbols]
1 Liquid 2 Liquid tank 3 Ship (marine structure)
4 Communication pipe 6 Permanent magnet 7 Power supply 8 Inverter 9 Electrode 10 Controller 12 Angular velocity meter (swing detection means)
13 Angular velocity signal (oscillation signal)
14 Flow meter 15 Flow signal

Claims (1)

A pair of liquid bath which is fixed to the marine structures by storing liquid having conductivity, a communicating tube formed as a rectangular pipe made of communicating with and two sets of opposing surfaces of the bottom portions of the respective liquid bath, A pair of permanent magnets arranged on the outside of one opposing surface of the communication pipe so as to form magnetic lines of force in a direction substantially perpendicular to the flow path direction of the communication pipe, and in the flow path direction of the communication pipe A pair of electrodes respectively disposed on the inner side of the other opposing surface of the communication pipe so as to allow a direct current to flow in a direction substantially perpendicular to the direction of the magnetic lines of force by the permanent magnet, and the ocean Swing detection means for detecting the swing of the structure, a flow meter for measuring the flow rate of the liquid flowing through the communication pipe, polarity inversion of the direct current supplied from the power source to the electrodes, and increase / decrease of the current value An inverter to perform and a swing signal from the swing detection means And the inverter is controlled based on the flow rate signal from the flowmeter so that the oscillation of the liquid between the liquid tanks corresponds to the oscillation cycle of the offshore structure and has a phase delay of about 90 °. An anti-sway device for an offshore structure, comprising: a control device that applies an appropriate Lorentz force to a liquid.

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