JP2005121135A - Magnetic fluid damper device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic fluid damper device for quasi-active damping, capable of dissipating the vibrational energy as a damper for optimum passive damping having highest damping performance among the dampers for passive damping, and quickly attenuating the vibration while saving the energy. <P>SOLUTION: In this magnetic fluid damper device 1, a first chamber 3 and a second chamber 4 in which the magnetic fluid 2 is packed, are connected by a cylinder 5 communicated with two chambers. Bellows as an expandable and contractible material is used for side walls of the first chamber 3 and the second chamber 4. Combined magnets 8a, 8b including permanent magnets in a state of winding coils 7a, 7b are mounted oppositely to each other near an outer side of the cylinder 5 to apply the magnetic field in the direction vertical to the flowing direction of the magnetic fluid 2 flowing in the cylinder 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ferrofluid damper device, and more particularly to a semi-active ferrofluid damper device suitable for damping a structure such as a space structure.

Structure damping methods are roughly classified into active damping and passive damping, and there is a semi-active damping as an intermediate method. The quasi-active damping is a method of actively controlling the characteristics of the structure and the damper so that the passive damping capacity of the structure is maximized. In the case of quasi-active damping, energy is dissipated by a passive mechanism, so the system is always stable compared to active damping, and at the same time, a higher damping effect can be expected compared to passive damping. .
Conventional quasi-active damping dampers are dampers that perform damping by changing the damper characteristics by opening and closing the orifice, or magnetic fluids or electrorheological fluids whose mechanical characteristics change depending on the input magnetic field or voltage. Some of them are used as an internal working fluid and absorb vibration energy quickly by making the damper characteristics variable.
In these conventional semi-active damping dampers, the working fluid when the input to the damper that does not control the damper characteristics is off is intended to improve the damping performance of the damper when the damper characteristics are controlled. Normally, the damper is designed so that the base viscosity of the resin becomes a low value. For this reason, the conventional quasi-active damping damper provides a high damping effect when the damper characteristics are controlled, but when the damper characteristics are not controlled, it is used for passive damping with a low viscosity. As a damper, there is a problem that the vibration damping effect is reduced because energy is dissipated.

AIAA Journal Vol. 35, No.12, 1844-1852 December 1997 Smart Mater. Struct. 11 (2002) 156-162

  Even when the damper characteristic is not controlled, the present invention can dissipate the vibration energy as the optimum passive damping damper with the highest vibration damping performance, while the damper characteristic is controlled. An object of the present invention is to provide a quasi-active damping ferrofluid damper device that can quickly attenuate vibrations while saving energy.

As a result of diligent research to solve the above-mentioned problems, the present inventor uses a magnetic fluid whose mechanical characteristics as a fluid change by an input magnetic field as a working fluid in a damper device, and a device for applying a magnetic field to the magnetic fluid It has been found that the above problems can be solved by using a composite magnet including an electromagnet incorporating a permanent magnet.
That is, the present invention
First and second chambers filled with magnetic fluid;
A magnetic part comprising: a communicating part for communicating the first and second chambers; and a permanent magnet and an electromagnetic coil arranged on the outside and in the vicinity of the magnetic part for applying a magnetic field to the magnetic fluid in the communicating part. A fluid damper device is provided.
The magnetic fluid damper device of the present invention preferably further includes a magnetic flux adjusting block for adjusting the magnetic flux of the permanent magnet toward the electromagnetic coil.
In the magnetic fluid damper device of the present invention, it is preferable that the magnetic flux adjusting block includes two blocks separated from each other with a predetermined interval.

  According to the present invention, when the damper characteristic is not controlled, the vibration energy is dissipated as an optimum passive damping damper, and when the damper characteristic is controlled, the vibration is quickly attenuated with energy saving. A quasi-active damping ferrofluid damper device can be obtained.

  FIG. 1 is a cross-sectional view of an embodiment of a magnetic fluid damper device according to the present invention. In the magnetic fluid damper device 1, a first chamber 3 and a second chamber 4 filled with a magnetic fluid 2 are respectively The two chambers are connected by a cylinder 5 that communicates. Bellows is used as a stretchable material on the side walls of the first chamber 3 and the second chamber 4. In the vicinity of the outside of the cylinder 5, composite magnets 8 a and 8 b including permanent magnets wound with coils 7 a and 7 b for applying a magnetic field perpendicular to the flow direction of the magnetic fluid 2 flowing in the cylinder 5 are opposed to each other. Are arranged.

FIG. 2 is a cross-sectional view of an example of a composite magnet used in the ferrofluid damper device of the present invention. The composite magnet 8 includes a permanent magnet 9, and the magnetic force generated by the permanent magnet 9 is applied to the composite magnets 8a and 8b. It passes through and acts on the magnetic fluid 2 in the cylinder 5 of the magnetic fluid damper device 1. In addition, coils 7a and 7b are wound in the vicinity of the composite magnets 8a and 8b. Further, on the side surface of the permanent magnet 9, a magnetic pole generated between the composite magnets 8a and 8b generated by the permanent magnet 9 is provided. A magnetic flux adjusting block 10 for adjusting the magnitude of the magnetic flux density at the center (point O) 13 is attached. The magnetic flux adjusting block 10 has two blocks 12 a and 12 b that are separated from each other by a predetermined gap 11.
When no current is applied to the coils 7 a and 7 b, if the magnetic flux adjusting block 10 is not attached to the side surface of the permanent magnet 9, the magnetic flux density at the point O is a constant magnitude determined by the magnetic force of the permanent magnet 9. Will be kept. When the magnetic flux adjusting block 10 is attached, a part of the magnetic flux from the permanent magnet 9 toward the composite magnets 8a and 8b can be directed toward the magnetic flux adjusting block 10. At this time, the block 12a and the block 12b By appropriately changing the size of the gap 11 between them, the magnetic flux density value at the point O can be changed. Further, the magnetic flux density at the point O formed by the combination of the permanent magnet 9 and the magnetic flux adjusting block 10 can be canceled by applying a current to the coils 7a and 7b to generate a magnetic force in the opposite direction. it can.

  FIG. 3 shows the case where various magnetic flux adjusting blocks 10 having different sizes of the gap 11 are used in the composite magnet 8 configured as described above without applying current to the coils 7a and 7b, and further, the coil 7a. , 7b shows a magnetic flux density distribution in the vicinity of point O when a current is applied. From FIG. 3, it can be seen that the magnetic flux density formed at the point O by the combination of the permanent magnet 9 and the magnetic flux adjusting block 10 without applying current can be canceled to almost 0 mT by applying current to the coils 7a and 7b. .

  FIG. 4 is a diagram showing the results of a repeated tensile / compression test of the damper at a constant speed, in order to understand the damper characteristics of the magnetic fluid damper device 1 configured as described above. From FIG. 4, when the magnetic flux density formed at the point O by the combination of the permanent magnet 9 and the magnetic flux adjusting block 10 is 40 mT, the relationship between the load applied to the damper and the extension of the damper shows a large hysteresis. Understand. On the other hand, when the 40 mT magnetic flux density is canceled by applying a current of 0.81 A to the coils 7a and 7b, the hysteresis becomes extremely small, which is almost the same as when the composite magnet is not used (0 mT). I understand.

FIG. 5 shows an approximate model of the magnetic fluid damper. As shown in FIG. 5, the mathematical model that can approximate the characteristics of the magnetic fluid damper includes two spring elements (k ₁ , k ₂ ) and a variable viscous element ( It consists of a dashpot element, c) and a coulomb friction element (f). In this embodiment, k ₁ corresponds to the axial rigidity of the bellows, and k ₂ corresponds to the volume rigidity of the magnetic fluid 2 in the magnetic fluid damper device 1. Further, c and f are due to the characteristics of the magnetic fluid 2 and are variable depending on the input of the magnetic field. From the linear optimal control theory, the optimal control amount for the elongation rate of the dashpot element in the mathematical model can be obtained. In this control, the input magnetic field is changed so that the elongation of the dashpot element is as large as possible, and the friction value and the viscosity value are positively switched. For example, when the elongation rate of the dashpot element is going to move away from the optimum value, the friction value and the viscosity value are increased to suppress the elongation of the dashpot. Decrease the value and viscosity so that the dashpot grows freely.

FIG. 6 is a block diagram showing an example of damping of a structure using the magnetic fluid damper device according to the present invention. Here, a cantilever truss 15 having a tip mass 14 and a total length of 3.4 m is used as the damping structure, and the magnetic fluid damper device 1 is disposed at the root of the truss 15. When vibration occurs in the truss 15, switching of the applied current to the coils 7a and 7b of the magnetic fluid damper device 1 is switched on (on-) based on an on-off switching determination conditional expression that is made up of a control law derived from the optimal linear control theory. Vibration control is performed by performing off control.
Measurement amounts necessary to realize this control include the load (p) applied to the magnetic fluid damper device 1, the elongation rate (d) of the magnetic fluid damper device 1, and the displacement amount (u) of the tip of the truss 15. These are measured by a load cell, an eddy current type displacement sensor and a laser displacement sensor, respectively. The value measured from each sensor is sent to the A / D board. An input on / off to the composite magnet is determined by a switching judgment conditional expression derived from the control side in the processor, and the judgment signal is sent to the switch board to switch the input magnetic field on / off to the magnetic fluid damper device 1. Do. In FIG. 6, a DC power source I is for driving a relay, and a DC power source II is for applying a current to the composite magnet.

FIG. 7 is a diagram showing a time history of the damping effect when various dampers are used, and the vertical axis represents the tip displacement u (mm) of the truss and the input magnetic flux density (mT) to the damper in FIG. FIG. 7A shows the time of the damping effect when the magnetic fluid damper device according to the present invention is used, and FIG. 7B shows the time of the damping effect when the conventional semi-active damping magnetic fluid damper using the electromagnet is used. Shows history. Further, in FIG. 7A, when a passive damper that does not employ a composite magnet is used (0 mT), the magnetic flux density formed at the point O is 40 mT due to the combination of the permanent magnet 9 and the magnetic flux adjusting block 10. The case where such a passive damper is configured is shown for comparison.
From FIG. 7 (a), it can be seen that in the magnetic fluid damper device according to the present invention, by controlling the damper characteristics, displacement attenuation much faster than that of the passive damper can be obtained. Further, comparing FIG. 7 (a) and FIG. 7 (b), a quasi-active damping magnetic fluid damper (FIG. 7) using only a conventional electromagnet that obtains a certain magnetic flux density when a current is applied to the electromagnet. 7 (b)), the ferrofluid damper device (FIG. 7 (a)) according to the present invention is an energy-saving type that can efficiently perform vibration suppression by simply applying a small current to the coil. I understand that.

FIG. 8 is a diagram showing a performance comparison between a passive damping damper in which the input magnetic field to the damper is maintained at a constant value and a semi-active damping damper using the magnetic fluid damper device of the present invention. In FIG. 8, the vertical axis U is a value obtained by integrating the absolute value of the displacement amount u of the truss tip in the example of damping of the structure shown in FIG. 6 for 20 seconds. The lower the U value, the higher the damping effect. Is obtained.
In the case of a passive damping damper, the lowest U value is obtained when the input magnetic field to the damper is kept constant at 25 mT. In this case, the optimum passive damper can obtain the highest damping effect. I understand that. On the other hand, in the magnetic fluid damper device of the present invention which is a semi-active damping damper, when the damper performance is controlled, a U value lower than that of the optimum passive damper is obtained and a high damping effect is obtained. I understand that.
The conventional semi-active damping damper is designed so that the base viscosity of the working fluid is low when the damper performance is not controlled in order to improve the damping performance when the damper performance is controlled. It was normal to do. For this reason, in the conventional semi-active damping damper, when the on-off switching device fails or when the damper is not operated, the energy is dissipated by a passive damper having a low viscosity (corresponding to the case of 0 mT in FIG. 8). Therefore, the damping effect as a passive damper cannot be expected. On the other hand, in the ferrofluid damper device of the present invention, for example, if the input magnetic field to the damper is set to 25 mT of the optimum passive damper, the optimum passive damper can be used even when the above problem occurs. Vibration energy can be absorbed. Further, when the damper performance is controlled in the magnetic fluid damper device of the present invention, vibration damping much faster than that of the optimum passive damper can be obtained.

As an application example of the present invention, it can be considered that the magnetic fluid damper device according to the present invention is used for damping a space structure that requires fail-safe and energy saving. In such a utilization mode, the magnetic fluid damper device of the present invention absorbs vibration energy as an optimum passive damper even when the damper device cannot be controlled on the orbit in outer space. Has the advantage of being able to.
As another application example of the present invention, it can be considered to be used for vibration control of a structure on the ground such as a building or a suspension of a car. In such a use mode, the ferrofluid damper device of the present invention acts as an optimum passive damper for low-level vibrations, and controls the damper device for high-level vibrations to speed up the vibrations. It has the advantage that it can be attenuated.

It is sectional drawing of one Example of the magnetic fluid damper apparatus by this invention. It is sectional drawing of an example of the composite magnet used for the magnetic fluid damper apparatus of this invention. It is a figure which shows magnetic flux density distribution in the point O vicinity. It is a figure which shows the result of the tension | pulling / compression repetition test of a damper. It is a figure which shows the approximation model of a magnetic fluid damper apparatus. It is a block diagram which shows an example of the vibration suppression of the structure using the magnetic fluid damper apparatus by this invention. (A) is a figure which shows the time history of the vibration suppression effect at the time of using the magnetic fluid damper apparatus by this invention, (b) uses the magnetic fluid damper for semi-active vibration suppression using only the conventional electromagnet. It is a figure which shows the time log | history of the vibration suppression effect at the time of doing. It is a figure which shows the performance comparison of the damper for passive vibrations with which the input magnetic field to a damper was maintained at the constant value, and the damper for quasi-active vibrations using the magnetic fluid damper apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic fluid damper apparatus 2 Magnetic fluid 3 1st chamber 4 2nd chamber 5 Cylinder 6 Bellows 7a, 7b Coils 8a, 8b Composite magnet 9 Permanent magnet 10 Magnetic flux adjustment block 11 Gap 12a, 12b Block 13 Center of magnetic pole ( Point O)
14 Tip mass 15 Cantilever truss

Claims (3)

First and second chambers filled with magnetic fluid;
A communication part that communicates the first and second chambers, and a permanent magnet and an electromagnetic coil that are arranged outside and in the vicinity of the communication part to apply a magnetic field to the magnetic fluid in the communication part. A magnetic fluid damper device.   The magnetic fluid damper device according to claim 1, further comprising a magnetic flux adjusting block for adjusting a magnetic flux of the permanent magnet toward the electromagnetic coil.   The magnetic fluid damper device according to claim 2, wherein the magnetic flux adjusting block includes two blocks separated from each other by a predetermined interval.

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