JP2006349053A - Natural frequency variable type vibration control method and vibration control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively control vibration even under situation in which excitation frequency is changed by controlling natural frequency of an additional vibration system by letting it follow excitation frequency. <P>SOLUTION: A vessel 3 storing magnetic fluid 2 is attached to a vibration controlled body 1, and an electromagnet 4 is attached to the vessel 3. A control part 11 obtains vibration frequency of a vibration control body 1 from output of a displacement gage 5 and controls current flowing in the electromagnet 4 by a current control part 12 in accordance with the vibration frequency to control strength of magnetic field applied on the magnetic fluid 2. By applying magnetic field to the magnetic fluid 2, the magnetic fluid 2 in the vessel 3 is attracted and fixed in accordance with strength of magnetic field, and sloshing resonance frequency of the additional vibration system 10 constituted by the magnetic fluid 2 and the vessel 3 is changed. By tuning the sloshing resonance frequency of the additional vibration system 10 with number of vibration frequency of the vibration controlled body 1 detected by the displacement gage 5, vibration of the vibration controlled body 1 is eliminated or reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vibration damping device for suppressing vibration, and uses a magnetic fluid that can be applied to various buildings, vehicles, various industrial devices, and various devices used in a zero-gravity field in outer space. The present invention relates to a vibration damping device.

Vibration control devices for structures such as buildings, vehicles, and various industrial equipment are roughly classified into three types: vibration resistance, vibration isolation, and vibration control devices.
Among them, the vibration damping device eliminates and reduces vibration and breakage of the structure by consuming the vibration energy given to the structure with dampers installed at various places.
The application of a dynamic vibration absorber is effective for damping a structure that receives a periodic excitation force. This is a device that tries to absorb the vibration of the structure by making the damper attached to the structure, that is, the natural frequency of the additional vibration system coincide with the vibration frequency, and forming a semi-resonance point near the vibration frequency of the structure. It is.
Various types such as a weight are used for the additional vibration system, but there are many that use a fluid in consideration of the great merit that there is no mechanical friction and that the vibration control effect is exhibited in two directions.

As a vibration damping device using a fluid, a sloshing damper using a fluid force of a liquid is known. The principle is that by matching the sloshing frequency with the natural frequency of the structure, the liquid in the container absorbs the vibration of the structure as kinetic energy, and the energy is diffused by using the damping due to the resistance of the wall surface etc. It is to let you.
In addition, various types of vibration control devices using the fluid sloshing effect using a magnetic fluid have been proposed (see, for example, Patent Document 1 and Non-Patent Document 1).
A magnetic fluid is a fluid that reacts to a magnetic field, and properties such as viscosity change when a magnetic field is applied. In the following, fluids exhibiting magnetism are collectively referred to as magnetic fluids, and for example, MR (magneto-rheological) fluids are also referred to herein as magnetic fluids.
JP-A-4-209275 Takahashi, Ohira, Sawada, Application of magnetic fluid sloshing to vibration control devices, Proceedings of Annual Meeting of the Japan Society of Mechanical Engineers (IV), No.001-1 (2000), p.267.

The sloshing damper using the fluid force of the liquid described above has the maximum damping effect near the resonance point of the structure by matching the natural frequency (sloshing resonance frequency) of the additional vibration system with the natural frequency of the structure. Designed to be obtained. In general, however, the vibration frequency varies depending on the situation. For example, the frequency of earthquakes is not always the same.
For this reason, the vibration suppression effect decreases as the vibration frequency moves away from the vicinity of the structure resonance point, and cannot be handled under the situation where the vibration frequency is assumed to change significantly.

On the other hand, as described in Patent Document 1 and Non-Patent Document 1, there is also known one that uses a magnetic fluid as a liquid and controls the movement of the magnetic liquid in the container by electromagnetic force.
Although the vibration control effect can be expected to be improved to some extent by controlling the movement of the magnetic fluid, even if the movement of the magnetic fluid is controlled as described in Patent Document 1 and Non-Patent Document 2, the additional vibration system The sloshing resonance frequency does not change, and it is not possible to cope with the situation where the excitation frequency changes significantly.
Therefore, it is desired to have a variable natural frequency damping device that can be tuned in such a manner that the natural frequency of the additional vibration system follows the changing vibration frequency.
The present invention has been made to solve the above problems, and its purpose is to follow the natural frequency of the additional vibration system to the excitation frequency in a vibration damping method and apparatus using magnetic fluid for the additional vibration system. It is an object of the present invention to provide a vibration damping method and apparatus capable of performing control and performing effective vibration damping even under a situation where the excitation frequency changes.

The present invention realizes a variable natural frequency damping technology in a fluid damping device using a fluid in an additional vibration system.
In the case of the fluid type vibration damping device, the sloshing phenomenon of the fluid hits the vibration as the additional vibration system. At this time, due to the nature of the sloshing phenomenon, the fluid in the container is divided into an effective mass portion that actually vibrates in the upper portion and an ineffective mass portion that does not actually vibrate in the other lower portions. Since the natural frequency of a certain vibration system depends on the mass and spring constant of the vibration system, the natural frequency (sloshing resonance frequency) in the sloshing phenomenon of fluid can be determined if this effective mass part and ineffective mass part can be controlled. Can be controlled.
In the present invention, a magnetic fluid that is more stable than an electrorheological fluid is used as the fluid in the container. A magnetic fluid is a functional fluid that behaves so that a fluid is attracted and attracted by application of a magnetic field.
If an electromagnet is prepared outside the container and a magnetic field is applied, the magnetic fluid in the container is attracted and fixed according to the magnetic field strength, and any mass is forcibly converted into an invalid mass. As a result, the sloshing resonance frequency of the magnetic fluid as the additional vibration system can be controlled, and the natural frequency of the additional vibration system can be synchronized with the vibration frequency of the vibration force applied to the structure.

Based on the above, the present invention solves the above problems as follows.
(1) A container containing a magnetic fluid is attached to a structure to be damped so that the liquid level of the fluid is substantially parallel to the vibration direction. Then, when a magnetic field is applied to the magnetic fluid, an effective mass portion that sloshing when vibration is applied to the fluid and an ineffective mass portion that is difficult to sloshing are formed, and the magnitude of the magnetic field or the range in which the magnetic field is applied is controlled. By doing so, the size of the ineffective mass portion is controlled, the sloshing resonance frequency of the magnetic fluid is set to a value corresponding to the vibration frequency, and the structure is damped.
(2) A plurality of the above-mentioned containers containing magnetic fluid are provided in the structure, and the magnetic force applying means provided in each container is controlled according to the vibration frequency detected by the detecting means.

In the present invention, the following effects can be obtained.
(1) A magnetic field is applied to the magnetic fluid to control the size of the ineffective mass portion of the magnetic fluid so that the sloshing resonance frequency of the magnetic fluid can be set to a value corresponding to the vibration frequency. The natural frequency of the additional vibration system can be tuned to the vibration frequency given to the filter, which is effective even in an environment where the vibration frequency applied to the structure placed in an environment where the vibration frequency is undefined The structure can be damped.
Moreover, since it also has the merit as a fluid type vibration damping device, there is little mechanical friction and it is effective also for minute vibration. Furthermore, since the magnetic field is controlled by the magnet, mechanical friction does not occur and smooth variable is possible.
(2) Since the magnetic fluid is supplemented by a magnetic field, the magnetic fluid can be applied to a vibration control device in outer space which is a microgravity environment.
(3) By providing a plurality of the above-described containers containing magnetic fluids in the structure and controlling the magnetic field applied to the magnetic fluid stored in each container according to the detected vibration frequency, Damping of structures is also possible.
In addition, by providing multiple containers with different magnetic fluid storage capacities in the structure and varying the variable range of the sloshing resonance frequency of each magnetic fluid, it is possible to widen the variable range of the natural frequency of the additional vibration system. A case where the frequency changes in a wide range can be dealt with.

FIG. 1 is a diagram showing a configuration of a vibration damping device according to a first embodiment of the present invention, and FIG. 2 is a block diagram showing a functional configuration thereof.
In FIG. 1, reference numeral 1 denotes a controlled body (structure), and a container 3 containing a magnetic fluid 2 is attached on the controlled body 1. When an external excitation force is applied to the controlled body 1 and the controlled body 1 vibrates, the magnetic fluid 2 in the container 3 flows in the magnetic fluid in the container (this phenomenon is referred to as sloshing).
An electromagnet 4 is attached to the lower side of the container 3, and the current flowing through the electromagnet 4 is controlled by the current control unit 12.
The vibration of the controlled body 1 is detected by the displacement meter 5 and given to the control unit 11. The control unit 11 obtains the vibration frequency of the damping body 1 from the output of the displacement meter 5, controls the current flowing through the electromagnet 4 by the current control unit 12 according to the vibration frequency, and applies the magnetic field to the magnetic fluid 2. Control the strength of the.

By applying a magnetic field to the magnetic fluid 2, the magnetic fluid 2 in the container 3 is attracted and fixed according to the magnetic field strength as described above, and a part of the magnetic fluid 2 is forcibly invalid massed according to the strength of the magnetic field. Then, the sloshing resonance frequency of the additional vibration system 10 composed of the magnetic fluid 2, the container 3, and the like changes.
By tuning the sloshing resonance frequency of the additional vibration system 10 to the vibration frequency of the vibration controlled body 1 detected by the displacement meter 5, the vibration of the vibration controlled body 1 can be eliminated or reduced.
In the present invention, since the magnetic field is applied to the magnetic fluid 2 and the sloshing frequency is tuned to the natural frequency of the vibration controlled body, the magnetic field strength may be a constant value. As described in Patent Document 1 and Non-Patent Document 1, it is not necessary to change the strength of the magnetic field at any time according to the motion of the vibration-damped body.
As shown in FIG. 1, the control unit 11 includes, for example, a CPU 7, interface units 7 a and 7 b, and a memory 8. The memory 8 stores programs and data for controlling the additional vibration system 10. Control processing of the additional vibration system 10 in the unit 11 can be realized by software executed by the CPU 7.

FIG. 2 is a block diagram showing a functional configuration of the vibration damping device of the first embodiment.
In the figure, the vibration of the controlled body (structure) 1 detected by the displacement meter 5 is input to the control unit 11. The Fourier analysis unit 11a of the control unit 11 performs a Fourier analysis on the vibration of the controlled body 1 detected by the displacement meter 5, and obtains frequency components f1, f2,... And amplitudes a1, a2,.
The damping frequency selection unit 11b determines a sloshing resonance frequency (hereinafter also referred to as damping frequency) fk of the additional vibration system based on the number of periods and the amplitude obtained by the Fourier analysis unit 11a. For example, the frequency having the largest amplitude among the frequency components obtained by the Fourier analysis unit 11a is set as the vibration suppression frequency fk.
The frequency-magnetic field conversion table 11c stores the sloshing resonance frequency of the additional vibration system with respect to the magnitude of the magnetic field applied to the magnetic fluid, which is obtained in advance through experiments or the like. By referring to the table 11c, for example, FIG. As shown in FIG. 3, the strength of the magnetic field corresponding to the damping frequency fk can be obtained.
The magnetic field calculation unit 11d refers to the table 11c, obtains the magnetic field strength B such that the sloshing resonance frequency of the additional vibration system becomes the vibration suppression frequency fk, and outputs it to the current control unit 12.
The current control unit 12 controls the current flowing through the electromagnet 4 so that the strength of the magnetic field applied to the magnetic fluid 2 becomes B.

In the above embodiment, the displacement meter 5 is used as a means for detecting the vibration of the vibration-damped body. However, an accelerometer can be used instead of the displacement meter 5, and the vibration of the vibration-damped body is important. Any detection means may be used as long as it can be detected.
In the above embodiment, the case where the electromagnet 4 is attached to the lower side of the container and the strength of the magnetic field applied to the electromagnet 4 is controlled has been described. However, for example, a configuration as shown in FIG. FIG. 4A shows the case where the electromagnet 4 is attached to the lower side of the container 3 as described above, but the electromagnet 4 may be attached to the upper side of the container 3 as shown in FIG. As will be described later, when the electromagnet 4 is attached to the lower side, the sloshing resonance frequency increases as the magnetic field is increased. However, when the electromagnet 4 is attached to the upper side, the sloshing resonance frequency decreases as the strength of the magnetic field is increased.

FIG. 4 (c) shows a case where a plurality of electromagnets 4 are provided on the lower side of the container 3, and a plurality of electromagnets A, B, C are attached to the container as shown in FIG. The sloshing resonance frequency can be changed in the same manner even if a current is selectively passed through C to change the range in which the magnetic field is applied.
For example, a current is applied only to the electromagnet A and a magnetic field is applied only by the electromagnet A, a current is applied to the electromagnets A and B, and a magnetic field is applied by the electromagnets A and B, or a current is applied to all the electromagnets A, B, and C. The size of the region to which the magnetic field is applied is changed stepwise, such as by applying a magnetic field. Furthermore, in the above, the magnitude of the current flowing through the electromagnets A, B, and C may be changed.

The above example is an installation example in a place where a gravitational field acts on the earth or the like, but when used in a space such as a microgravity environment, an additional vibration system may be installed as shown in FIG. it can.
When used in a place where gravity works, such as on the earth, as shown in FIGS. 4A to 4C, the liquid surface of the magnetic fluid becomes a plane orthogonal to the direction in which the gravity acts, and additional vibration is generated. As shown in the figure, the vibration damping function by the system works only for vibrations in the horizontal direction with respect to the liquid surface of the magnetic fluid.
On the other hand, since the magnetic fluid is captured by the magnetic field in the cosmic space which is a microgravity environment, the arrangement shown in FIG. 5 is also possible. That is, as shown in the figure, a container containing an electromagnet and a magnetic fluid can be attached to the side surface of the damping body 1 so as to obtain a damping effect against vibrations in the vertical direction.

In order to confirm that the sloshing resonance frequency is changed by applying a magnetic field to the magnetic fluid, the change of the sloshing resonance frequency of the additional vibration system with respect to the strength of the magnetic field was examined using the experimental apparatus shown in FIG.
As shown in FIG. 6A, the experimental apparatus is provided with a vibration table 22 on a base 24, and a container 21 containing a magnetic fluid 25 is attached to the vibration table 22 that is vibrated by an actuator 23. A magnet 26 was placed above or below.
Then, the magnitude of the magnetic field applied to the magnetic fluid 25 is changed by changing the size of the magnet 26, and the level of the liquid surface of the magnetic fluid 25 is changed by the laser displacement meter 27 while vibrating the vibration table 7 by the actuator 23. The displacement was investigated.
Specifically, the excitation frequency of the vibration table 22 is changed, the displacement of the liquid surface of the magnetic fluid 25 is detected by the laser displacement meter 27, the frequency at which the displacement of the liquid surface is maximum is detected, and the magnetic fluid 25 is detected. The sloshing resonance frequency was measured. At this time, the excitation amplitude applied to the container 21 was uniformly 1.5 mm.
The container 21 is a rectangular parallelepiped as shown in FIG. 6B, and the size of the bottom surface is 300 × 20 mm. The magnetic fluid 25 is placed in this container so as to have a depth of 100 m. The magnetic fluid used was a ferricolloid W-40 manufactured by Taiho Industry diluted with water at a volume ratio of 24%.

The experimental results are shown in FIGS. 7 (a) and 7 (b). 7A, when the magnet 26 is disposed on the lower side of the container 21 and a magnetic field is applied from the lower side of the magnetic fluid 25, FIG. The result at the time of applying a magnetic field from the upper side of 25 is shown.
7A and 7B, the horizontal axis indicates the strength of the magnetic field applied to the magnetic fluid 25 by the magnet, and the vertical axis indicates the sloshing resonance frequency.
As is clear from FIG. 7A, the sloshing resonance frequency is increased to a maximum of nearly 0.5 Hz by applying a magnetic field as compared with the state without a magnetic field.
In addition, when the magnetic field is applied from above the magnetic fluid 25 as shown in FIG. 7B, the sloshing resonance frequency is lowered by applying the magnetic field as compared to the state without the magnetic field.
From the above experimental results, it was confirmed that the sloshing resonance frequency can be controlled by applying a magnetic field to the magnetic fluid and changing its strength.

FIG. 8 is a view showing a second embodiment of the present invention when the present invention is applied to a relatively large vibration-damped body (structure).
When the vibration-damped body is relatively large, as shown in FIG. 7, a plurality of additional vibration systems 10 including a container containing a magnetic fluid, an electromagnet, and the like are distributed and arranged on the vibration-damped body 1. Is desirable.
FIG. 8 shows a case where three sets of additional vibration systems 10 having the same fluctuation range of the sloshing resonance frequency are provided on the vibration-damped body 1. The functional configuration of the control unit 11 is the same as that shown in FIG. 2, and the current control units 12a, 12b, and 12c are controlled by the output of the control unit 11, and the magnetic field generated by the electromagnet provided in the additional vibration system 10 is controlled. Control strength in parallel.
If comprised in this way, even if the to-be-damped body 1 is comparatively large, the vibration of the to-be-damped body 1 can be erased or reduced. In addition, since the additional vibration system is dispersedly arranged on the vibration-damped body 1, the load of the additional vibration system applied to the vibration-damped body 1 can be dispersed.

FIG. 9 is a diagram showing a configuration of a vibration damping device according to a third embodiment of the present invention in which a plurality of additional vibration systems 10a, 10b, and 10c having different fluctuation ranges of the sloshing resonance frequency are provided in the vibration-damped body 1.
Each additional vibration system 10a, 10b, 10c is configured such that the sloshing resonance frequency becomes a different value by adjusting the size of the container, the amount of the magnetic fluid, and the like. Although the sloshing resonance frequency of each additional vibration system 10a, 10b, 10c changes according to the strength of the magnetic field applied to the magnetic fluid in each container, the fluctuation range is set as follows, for example.
The fluctuation range of the sloshing resonance frequency of the additional vibration system 10a: f1 to f2 (f1 <f2)
The fluctuation range of the sloshing resonance frequency of the additional vibration system 10b: f3 to f4 (f3 <f4)
The fluctuation range of the sloshing resonance frequency of the additional vibration system 10c: f5 to f6 (f5 <f6)
・ F1 <f3 ≦ f2, f3 <f5 ≦ f4

That is, by selectively exciting the electromagnet 4 of the additional vibration system 10a, 10b, 10c and setting the strength of the magnetic field to a predetermined value, the sloshing resonance frequency of the additional vibration system 10a, 10b, or 10c is f1. Can be tuned to any frequency within ~ f6.
When the vibration meter 1 detects the vibration frequency of the vibration-damped body 1, the control unit 11 selects one of the additional vibration systems 10a to 10c via the current control units 12a, 12b, and 12c according to the detected vibration frequency. The electromagnet is excited to apply a magnetic field to the magnetic fluid, and the sloshing resonance frequency of the additional vibration systems 10a to 10c is controlled to be tuned to the above frequency.
Thereby, if the vibration frequency is within the fluctuation range f1 to f6 of the sloshing frequency of the additional vibration systems 10a to 10c, the vibration of the controlled body 1 can be eliminated or reduced.

FIG. 10 is a block diagram showing a functional configuration of the vibration damping device of the third embodiment.
In the figure, the vibration of the controlled body (structure) 1 detected by the displacement meter 5 is input to the control unit 11. The Fourier analysis unit 11a of the control unit 11 performs a Fourier analysis on the vibration of the controlled body 1 detected by the displacement meter 5, and obtains frequency components f1, f2,... And amplitudes a1, a2,.
The damping frequency selection unit 11b determines the damping frequency fk of the additional vibration system based on the number of periods and the amplitude obtained by the Fourier analysis unit 11a. For example, the frequency having the largest amplitude among the frequency components obtained by the Fourier analysis unit 11a as described above is set as the vibration suppression frequency fk.

In the frequency-magnetic field conversion tables 11c-1, 11c-2, and 11c-3, correspondence data of the sloshing resonance frequency of the additional vibration system with respect to the magnitude of the magnetic field applied to the magnetic fluid obtained in advance by experiments or the like is stored. . For example, as shown in FIG. 11, the magnetic field strength for setting the sloshing resonance frequency to an arbitrary value between f1 and f2 is registered in the table 11c-1, and the sloshing resonance frequency is registered in the table 11c-2. The strength of the magnetic field for setting an arbitrary value between f3-f4 is registered, and the strength of the magnetic field for setting the sloshing resonance frequency to an arbitrary value between f5-f6 is registered in the table 11c-2. Is registered.
When the magnetic field calculation units 11d-1, 11d-2, and 11d-3 are given a vibration suppression frequency fk, the above-described frequency-magnetic field conversion tables 11c-1, 11c-2, and 11c-3 are referred to above. When the frequency fk is within the frequency range stored in the table, the strength of the magnetic field is output to the current control unit of the additional vibration system.

For example, when the vibration suppression frequency fk is within the range of f1-f2, the magnetic field calculation unit 11d-2 has the magnetic field strength B1 such that the sloshing resonance frequency of the additional vibration system 10a becomes the vibration suppression frequency fk. Is output to the current control unit 12a of the additional vibration system 10a.
The current control unit 12a controls the current flowing through the electromagnet 4 so that the strength of the magnetic field applied to the magnetic fluid 2 of the additional vibration system 10a is B1. As a result, the sloshing frequency of the additional vibration system 10a is synchronized with the vibration suppression frequency fk, and the vibration of the vibration controlled body 1 is eliminated or suppressed.
In the above embodiment, three sets of additional resonance systems are provided. However, the number of additional vibration systems may be appropriately selected according to the frequency range to be tuned, and the range of the sloshing resonance frequency of the additional vibration system can be broadened. If desired, three or more additional resonance systems having different sloshing resonance frequencies may be provided.
By configuring as in the present embodiment, even when the vibration frequency applied to the controlled body varies over a wide range, the sloshing resonance frequency of the additional vibration system can be tuned to this frequency.

FIG. 12 is a diagram showing a specific configuration example of the vibration damping device of the present invention. FIG. 12A shows the case where the electromagnet 4 is provided below the magnetic fluid 2, and FIG. The example of a structure at the time of providing in the upper side of the magnetic fluid 2 is shown.
As shown in the figure, a magnetic fluid 2 is accommodated in a cylindrical container 3, and an electromagnet 4 is provided below or above the magnetic fluid 2. A computer center 30 is provided below the container, and the displacement meter 5, the control unit 11, the current control unit 12, and the like are stored in the computer center 30.
By setting it as the said structure, a damping device can be comprised compactly, and since the container is cylindrical, the same damping effect can be acquired irrespective of a vibration direction.

FIG. 13 is a diagram showing an application example of the vibration damping device of the present invention.
FIG. 2A shows a case where the vibration damping device of the present invention is applied to vibration suppression of a pedestrian bridge, and FIG. 3 shows a case where three sets of vibration damping devices are installed on the pedestrian bridge.
In the case of a relatively large structure such as a pedestrian bridge, vibrations that are effectively applied to the pedestrian bridge by installing a plurality of vibration control devices as shown in FIG. Can be erased or suppressed.
FIG. 2B shows a case where the vibration damping device of the present invention is installed on a steel tower such as a power transmission tower. By installing the vibration damping device of the present invention near the top of the steel tower as shown in FIG. It is possible to eliminate or suppress the shaking of the steel tower due to wind or the like.
FIG. 5C shows a case where the vibration damping device of the present invention is installed on a work table for mounting a measuring instrument sensitive to vibration or performing fine processing that is easily affected by vibration. As shown in the figure, by installing the vibration damping device of the present invention on a workbench, vibrations of the workbench due to external force or the like can be eliminated and suppressed.
Although FIGS. 8, 9, and 13 show the case where the electromagnet is disposed below the magnetic fluid, the electromagnet may be provided above the magnetic fluid as described above.

It is a figure which shows the structure of the damping device of 1st Example of this invention. It is a block diagram which shows the function structure of the damping device of 1st Example of this invention. In a 1st Example, it is a figure explaining the method of calculating | requiring the intensity | strength of the magnetic field corresponding to a damping frequency with a frequency-magnetic field conversion table. It is a figure which shows the example of arrangement | positioning of an electromagnet. It is a figure which shows the example of arrangement | positioning of the electromagnet when using it in the space etc. which are microgravity environment. It is a figure which shows the structure of the experimental apparatus used when the change of sloshing resonance frequency was investigated. It is a figure which shows the experimental result by the experimental apparatus of FIG. It is a figure which shows the 2nd Example of this invention. It is a figure which shows the 3rd Example of this invention. It is a block diagram which shows the function structure of the damping device of a 3rd Example. In a 3rd Example, it is a figure explaining the method of calculating | requiring the intensity | strength of the magnetic field corresponding to a damping frequency with a frequency-magnetic field conversion table. It is a figure which shows the specific structural example of the damping device of this invention. It is a figure which shows the example of application of the damping device of this invention.

Explanation of symbols

1 Damped body (structure)
2 Magnetic fluid 3 Container 4 Electromagnet 5 Displacement meter 6 CPU
7a, 7b Interface 8 Memory 10 Additional vibration system 11 Control unit 11a Fourier analysis unit 11b Damping frequency selection unit 11c Damping frequency-magnetic field conversion table 11d Magnetic field calculation unit 12 Current control unit

Claims (3)

A vibration damping method for a structure placed in an environment where the vibration frequency is indefinite,
Attach a container containing magnetic fluid to the above structure so that the fluid level is substantially parallel to the vibration direction,
Applying a magnetic field to the fluid showing the magnetism to form an effective mass part that sloshing when vibration is applied to the fluid and an ineffective mass part that is difficult to sloshing to control the magnitude of the magnetic field or the range in which the magnetic field is applied By controlling the size of the ineffective mass portion, the sloshing resonance of the fluid is controlled by setting the sloshing resonance frequency of the fluid exhibiting magnetism to a value corresponding to the vibration frequency. Frequency variable vibration control method. A vibration suppression control device that suppresses a structure disposed in an environment with an indefinite vibration frequency,
A container that is attached to the structure and contains a fluid representing a magnetic body so that the liquid level is substantially parallel to the vibration direction; and a detection means that detects a vibration frequency applied to the structure;
A magnetic field applying means for applying a magnetic field to the fluid containing the magnetic material, and forming an effective mass portion that sloshing when vibration is applied to the fluid, and an ineffective mass portion that does not sloshing;
By controlling the magnitude of the magnetic field applied by the magnetic field applying means or the range of applying the magnetic field according to the vibration frequency detected by the detecting means, the size of the ineffective mass portion of the fluid is controlled, And a control means for setting the sloshing resonance frequency of the fluid containing the magnetic material to a value corresponding to the vibration frequency. A plurality of the above-mentioned containers containing a fluid exhibiting magnetism are provided in the structure,
3. The natural frequency variable vibration damping control device according to claim 2, wherein magnetic force applying means provided in each container is controlled in accordance with the vibration frequency detected by the detecting means.

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