JPH09112628A - Magnetic levitation vibration resistant device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove vibrations satisfactorily even in vertical direction. SOLUTION: A magnetic levitation vibration resistant device is composed of a table equipped with a flat plate made of a magnetic substance and an electromagnetic actuator 12 which exerts a magnetic attraction force to the flat plate and suspends the table afloat, wherein the arrangement includes a displacement sensor 14 to measure the relative displacement between the surface of flat plate and the magnetic pole face of the electromagnet, an acceleration sensor 13 to measure the absolute acceleration of the table, and a control device 15 to control the energizing current for the electromagnet on the basis of the signals given by the sensors. The control device 15 works according to two control laws, i.e., the control law to be used in controlling the gap between the surface of the flat plate and the magnetic pole face of the elecromagnet and control law to be used in controlling the vibration on the basis of the signal given by the acceleration sensor 13, wherein the stability control for the relative displacement of the table is included in the latter, i.e., the control law for controlling the vibration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic levitation anti-vibration device, and particularly to equipment for causing yield and accuracy problems due to vibration from the installation floor, such as semiconductor manufacturing equipment and electron microscopes. The present invention relates to a high-precision vibration isolation device that insulates.

[0002]

2. Description of the Related Art Conventionally, an anti-vibration device is installed to insulate an anti-vibration device, such as a semiconductor manufacturing apparatus or an electron microscope, which causes a problem in yield and accuracy due to vibration from the installation floor, from the floor vibration. Air springs and anti-vibration rubber were used on the bottom of the anti-vibration base plate. Further, in a vibration isolation table of a type that actively controls the motion of the floor plate, hydraulic or pneumatic cylinders or electromagnetic solenoids are used to eliminate the vibration of the floor plate of the vibration isolation table.

Here, in a passive type vibration isolation table vertically supported by using an air spring or a rubber vibration isolator, a resonance system of a spring and a mass (mass) is formed. Therefore, there is a problem that the vibration isolation effect is obtained at a frequency considerably higher than the resonance frequency, but the vibration isolation effect is completely absent at the frequency below the resonance frequency.

Further, the natural frequency of the building in which the frame of the vibration isolation table is installed in the horizontal direction is lower than the natural frequency in the vertical direction, and the horizontal vibration of the ground is always transmitted. A vibration isolation table for installing a microscope or the like is required to have a horizontal vibration isolation effect.
However, the supporting materials used for air springs and anti-vibration rubber are
Since it generally has a lateral rigidity (horizontal rigidity) larger than the supporting direction, a resonance system is formed in the horizontal direction even when supporting in the vertical direction. Since the natural frequency in the horizontal resonance system is equal to or higher than that in the vertical direction, the vibration isolation effect in the horizontal direction is inferior to that in the vertical direction, and the above requirements cannot be met. .

Therefore, a magnetic levitation type vibration isolation device has been devised (see, for example, Japanese Patent Application Laid-Open No. 2-203040 and Japanese Patent Publication No. 4-74053). The magnetic levitation type vibration isolation device holds a table in a state of being levitated in a space by non-contact supporting a table on which a device dislikes vibration is mounted by an electromagnet actuator. Therefore, of course, the vibration of the installation floor is not directly transmitted to the table, but the magnetic attraction force for holding the table and the table equipped with the vibration eliminator constitute a kind of spring-mass resonance system. Therefore, the relative displacement between the table and the electromagnet pole face,
Although the absolute acceleration on the table is detected and feedback control is performed on the exciting current of the electromagnet, the constant of the spring changes due to the configuration of this control device, resulting in different vibration isolation characteristics.

The inventors of the present invention have described an example of a control device for such a magnetic levitation vibration isolator as follows: Proceedings of the Japan Society of Mechanical Engineers No. 930-39 [199].
July 3rd, "Study on magnetic levitation vibration isolation device" (2nd report, vibration isolation characteristics of 3D vibration isolation device) Kazuhide Watanabe, Yoichi Kanemitsu, Kenichi Yasuno,
Mizuno Takayuki].

In this vibration isolator, the electromagnet actuator for controlling the floating / vibration of the table detects the DC electromagnet that generates a magnetic attraction force in the vertical and horizontal directions, and the relative displacement between the installation floor and the vibration isolation table. It has a built-in displacement sensor. Also, the table has a built-in acceleration sensor,
Detects vertical and horizontal absolute acceleration.

This control system comprises a horizontal direction control system and a vertical direction control system, and is realized by an analog controller. This control system first detects the relative displacement in the vertical direction between the installation floor and the vibration isolation table with a displacement sensor, and feeds back the relative displacement amount to raise the vibration isolation table to a fixed target position. In the horizontal direction, it is supported by the restoring force generated by the vertical control electromagnet. Further, the horizontal / vertical vibration isolation control is performed by detecting the absolute acceleration on the horizontal / vertical vibration isolation table by the acceleration sensor and feeding back the absolute amount.

The vertical control electromagnet supports the anti-vibration table in a non-contact manner by the generated magnetic attraction force fa, and also generates a restoring force fr which is passive and stable in the horizontal direction. This restoring force fr is much smaller than the magnetic force in the suction (vertical) direction, and it means that it is stably supported with weak rigidity in the horizontal direction. Can be shaken.

In the vertical direction, since the magnetic pole surface of the electromagnet located above is attracted and held by the magnetic attraction force to the flat plate, when the relative displacement between them becomes small, the flat plate is attracted to the electromagnet side, When the displacement becomes large, gravity prevails, and the flat plate moves away, forming an unstable system. In order to stabilize this unstable system, the PID controller G
Relative feedback control is performed in (S). Parameter K
The vibration transmissibility of the stabilized control system by setting _P, KI _{, and Kd} is expressed by the transfer function as shown in equation (1).

G (s) = − (k _p + k _d S + k _l / S) (1)

In this transmission system, all floor vibrations are transmitted to the vibration isolation table within the response frequency range of relative displacement. Here, in order to improve the vibration transmissibility, absolute acceleration and absolute velocity feedback G _{av are added} to this relative feedback system.
(S) is added.

G _av (S) = − (k _av S ² + k _vv S) (2) Then, the displacement W (S) of the installation floor and the displacement Z of the table
The transfer function with (S) is as in equation (3), K _av , K
_The vibration transmissibility can be improved by _vv .

[0014]

(Equation 9)

An evaluation test was conducted on the prototyped vibration isolator by microscopic vibration of the floor. 14 and 15 show damping performance against floor vibration. In the horizontal direction, as shown in FIG. 14, floor vibration could be isolated to about 1/10. In the vertical direction, floor vibration could be reduced to about 1/2 to 1/3 by adding an absolute feedback system to the relative system (levitation system) as shown in FIG.

[0016]

However, in the magnetic levitation vibration isolator described above, the vibration isolation performance in the horizontal direction is sufficient, but the vibration isolation performance in the vertical direction is sufficient for the relative (levitation) system. By adding an absolute feedback system based on
It is only 3 and is not always sufficient.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a magnetic levitation vibration isolator capable of sufficiently removing vibration even in the vertical direction.

[0018]

SUMMARY OF THE INVENTION A magnetic levitation vibration isolator according to the present invention comprises a table provided with a flat plate made of a magnetic material, and an electromagnet actuator for applying a magnetic attraction force to the flat plate to suspend and suspend the table. In the floating anti-vibration device,
A displacement sensor that measures the relative displacement between the flat plate surface and the electromagnet magnetic pole surface, an acceleration sensor that measures the absolute acceleration of the table, and a control device that controls the exciting current of the electromagnet based on the signals of these sensors. The control device is divided into a control law for controlling the gap between the flat plate surface and the electromagnet magnetic pole surface based on the signal of the displacement sensor, and a control law for controlling vibration based on the signal of the acceleration sensor.
It is characterized in that stability control of relative displacement of the table is included in a control law for controlling vibration based on a signal of the acceleration sensor.

The control law for controlling the gap between the flat plate surface and the electromagnet magnetic pole surface based on the signal from the displacement sensor is PI.
The control law is (proportional integral) control, and the control law including the stability control of the gap in the control law for controlling the vibration is H∞ (infinity) control.

Further, the control device is characterized by being configured by incorporating PI (proportional integral) control into H∞ (infinity) control.

Further, the magnetic levitation vibration isolator is characterized in that an electromagnet actuator for suspending and suspending the table is combined with an actuator composed of an air spring.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 13, since the vibration isolation table is levitationally supported by the magnetic attraction force of the electromagnet in a non-contact manner, the gap (relative displacement) Z between the electromagnet magnetic pole surface and the table is set to a constant target value. A relative position feedback system is required to position at Z ₀ . This relative position feedback is P
The ID controller 21 performs this control. Here, the integral control (I) is control for reducing the steady error, and the differential control (D) is control for stabilization. The acceleration / velocity controller 22 is for feeding back the absolute acceleration and velocity of the table in the Z direction to attenuate the vibration of the table.

However, the stabilizing control for the relative displacement control is the differential control of the displacement value Z, which is the same kind of control as the differential and double differential control of the displacement amount Z of the controller 22 for vibration damping. They had a correlation with each other. Therefore, for example, when the optimum parameter is used in the stabilization control, the damping is insufficient in the vibration damping control, and when the optimum parameter is used in the vibration damping control, there is a problem that the stability is impaired. Therefore, in the prior art, no matter how many times the selection of various parameters was repeated, the stability in the vertical direction and the sufficient vibration suppressing effect were not obtained.

According to the present invention, as shown in FIG. 12, the stabilization (derivative) control is removed from the control of the relative displacement system, and the gap (relative displacement Z) is calculated by PI (proportional integral) based on the signal of the displacement sensor. ) It is controlled by control. Then, H ∞ in which stabilization control is included in the control law for controlling the vibration
It is controlled. As a result, since the differential control is unified, the problem that a correlation occurs between the two control rules as in the prior art is solved, and the parameters can be set independently in the proportional, integral and differential systems. Therefore,
According to the controller of the present invention, sufficient stability in the vertical direction can be achieved while ensuring stability.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of the vibration isolator of the first embodiment. As shown in FIG. 1, the vibration isolation device is composed of a vibration isolation table 11 equipped with a vibration isolation device, four electromagnet actuators 12, and a controller (not shown). Further, an acceleration sensor 13 for detecting vibration on the vibration isolation table 11 is attached to the vibration isolation table 11.

FIG. 2 shows the control system. The controller is a digital controller 15 equipped with a DSP,
An A / D converter 16 and a D / A converter 17 are mounted. This control system detects a relative displacement signal from a displacement sensor built in each electromagnet actuator and an absolute acceleration signal from an acceleration sensor attached to a vibration isolation table, inputs the signal to a DSP 18 via an A / D converter 16, and after calculation. , The D / A converter 17 and the power amplifier 19 to excite the electromagnet to float the vibration isolation table and perform vibration isolation control.

The electromagnet actuator 12 detects a DC electromagnet that generates a magnetic attraction force in the vertical and horizontal directions for performing levitation and vibration isolation control of the vibration isolation table, and a relative displacement between the installation floor and the vibration isolation table. It has a built-in displacement sensor. Four vertical control electromagnets have the ability to support a considerable weight of the payload.

FIG. 3 shows a model of the vibration isolation device. This figure shows a balanced state in which the vibration isolation table 11 is supported by four electromagnet actuators. Here, the action direction of the force of each electromagnet is made to coincide with the direction of the coordinate axis, and the action point of the force is in the x and y planes (horizontal plane including the center of gravity). The symbols used are as follows.

G: center of gravity, F _xi , F _yi , F _zxi (i = 1 to 4): control force of each actuator, Mα, Mβ, Mγ: control force moment, K _{xi ,} K _yi (i = 1 to 4) ): Spring constant due to horizontal magnetic restoring force of each vertical electromagnet, C _{xi ,} C _yi (i = 1 to 4): Attenuation coefficient due to horizontal magnetic restoring force of each vertical electromagnet, x, y, z: Removal Vibration table displacement, α, β, γ: Rotational displacement of vibration isolation table, u, v, w: Displacement of installation floor, ε, η, ζ: Rotational displacement of installation floor.

This anti-vibration device model is assumed to be an ideal rigid body with completely uncoupled support, and the control system can be designed independently for each degree of freedom. Therefore, the model satisfies the following conditions. (1) The coordinate axis is made to coincide with the principal axis of inertia of the apparatus, and the inertia coupling term is eliminated. (2) The elastic center and the elastic main shaft due to the horizontal magnetic restoring force of the four vertical electromagnets are aligned with the center of gravity and the inertial main shaft of the device.

From the above, the equation of motion of the vibration isolator becomes equation (4). Here, m is mass, Iα, Iβ, Iγ are moments of inertia around each axis, K _x , K _y , K γ are spring constants due to magnetic restoring force of the vertical electromagnet, C _x , C _y , C γ.
Is the damping coefficient due to the magnetic restoring force of the vertical electromagnet.

[0033]

(Equation 1)

When the control force vector F is linearized near the equilibrium state, the equation (5) is obtained. Here, I is a control current, and K _v and K _c are constants for the displacement and the current, respectively.

[0035]

(Equation 2)

The model of the apparatus was assumed to be a 6-degree-of-freedom system independent from the previous section, and the control system was designed. Here, vertical control for achieving stable levitation of the vibration isolation device and vibration isolation control at the same time will be described. The control system in the vertical direction has 1 translational degree of freedom and 2 rotational degrees of freedom according to the equation of motion. In this design, H∞ (infinity) control theory with robustness was applied, and it was designed independently for each of the three degrees of freedom. Signals actually detected by each sensor (relative displacement, absolute acceleration)
The control current to each electromagnet is coordinate-converted inside the controller to enable control for each degree of freedom. Below, translation 1
The control system design of the degree of freedom is described.

When the control object having the vertical translation 1 degree of freedom is expressed in the state space, the equations (6) and (7) are obtained. Here, z is the absolute displacement in the vertical direction. Also, the magnetic attraction force in the vertical direction is
Since solid wood is used, there is a phase delay due to the generation of eddy currents. This characteristic K _a (S) is represented by the state equation of equations (8) and (9). Further, Af, Bf, and Cf are constants when they are approximated by first-order delay.

[0038]

(Equation 3)

Further, the controller designed here must simultaneously achieve the levitation control and the vibration isolation device. Therefore, it is necessary to feed back both the relative displacement between the vibration isolation table and the installation floor and the absolute acceleration on the vibration isolation table. Therefore, this time, we have included a relative displacement feedback system in the generalized plant in advance. This relative feedback system controller includes a PI (proportional, integral) controller Kr required for levitation positioning in the center of the air gap of the electromagnet.
(S). The PI controller Kr (S) is expressed by the formula (1
It is represented by 0) and (11). Therefore, the operation input u is expressed by the equation (12).
Becomes

[0040]

(Equation 4)

FIG. 4 shows the generalized plant created. The disturbance applied to the system is floor vibration w ₁ and acceleration sensor noise w ₂
And Here, d ₁ and d ₂ multiplied by the weighting factors K _l and K _n for the disturbance are directly added to the system.

[0042]

(Equation 5)

Further, the absolute amount (displacement, velocity, acceleration) and relative displacement on the vibration isolation table were selected as control amounts. The operation input (control current) was also evaluated to be appropriately small. These can be summarized as formula (14). The weighting coefficient for each control amount and operation input is given by a scalar. here,
By evaluating all the absolute quantities (acceleration, velocity, displacement), the weighting is equivalent to that of introducing frequency weighting. This leads to a reduction in the dimension of the controller. The output y is the absolute acceleration detected by the acceleration sensor and is given by Expression (15). From the above, the generalized plant shown in FIG. 4 can be derived. Here, K _as is the acceleration sensor and K _ds is the gain of the displacement sensor. Therefore, the state space model of the generalized plant is expressed by equations (16) and (17).
(18)

[0044]

(Equation 6)

An H∞ controller is designed for the expansion system including the PI controller that feeds back the relative displacement created in the previous section. From the state space model of the generalized plant, the transfer function can be expressed as equation (19).

[0046]

(Equation 7)

When the feedback control system is constructed by defining the control law for this expanded system as u = K (s) y, the closed loop transfer function from w to z is given by equation (24). φ = G ₁₁ + G ₁₂ K (I−G ₂₂ K) ⁻¹ G ₂₁ (24) Here, G (s) is internally stabilized and the controller K (s) satisfying the inequality (25) is obtained.

[0048]

(Equation 8)

In obtaining the controller, in order to stabilize the magnetic levitation system and obtain good vibration isolation performance, each weighting factor and γ are set so that the sensitivity from the disturbance d ₁ to the absolute displacement z becomes as low as possible to a low frequency. Was selected and repeated calculation was performed. FIG. 5 shows the frequency characteristics of the designed H ∞ controller and PI controller.

Further, FIG. 6 shows the step response, and FIG. 7 shows the disturbance d.
The sensitivity from ₁ to the controlled variable z, that is, the vibration transmissibility is shown.
From these figures, it can be seen that stable levitation is possible and a good vibration transmissibility is obtained. A controller with a two-degree-of-freedom system was designed in the same way.

The designed controller with three degrees of freedom was realized by a digital controller and an evaluation test was conducted. The controller of each degree of freedom was a 2-input 1-output controller by combining the H ∞ controller and the PI controller. FIG. 8 shows the response characteristics when the vibration isolation table floats. Further, FIG. 9 shows the vibration transmissibility of acceleration on the installation floor and the vibration isolation table in the equilibrium state, and FIG. 10 shows the time history waveform. From these results, performance close to that of simulation was obtained, and stable levitation was achieved while floor vibration was reduced to 1 /
It was possible to isolate the vibration to 10. Further, FIG. 11 shows the impact response characteristics when a disturbance is directly applied to the vibration isolation table, and it was possible to converge instantly.

Although the above-mentioned embodiment is directed to the case where the vibration isolation table is floated from the actuator by using the electromagnet actuator in a non-contact manner, even if the air spring actuator is used in combination with the electromagnet actuator,
The gist of the present invention can be similarly applied.

FIG. 16 shows an elevation view of a vibration isolator according to the second embodiment of the present invention, and FIG. 17 shows a plan view thereof. On the vibration isolation table 30, mechanical devices such as an electron microscope and a semiconductor manufacturing device, which are not sensitive to vibration, are mounted. The vibration isolation table 30 is vertically supported by air springs 31 at its four corners. The air spring 31 has one end fixed to the shared base 12 fixed on the installation floor. An acceleration sensor 33 that detects accelerations in the X, Y, and Z directions is provided on the vibration isolation table.

The air spring 31 positions the table 30 in the vertical direction in response to a signal from a displacement sensor (not shown) by a control device (not shown) for controlling the pressure, and controls the weight of the vibration isolation table and the mechanical devices mounted on the table. Mostly supportive. The displacement sensor is built in the vertical electromagnet actuator 35, and detects the relative displacement of the vibration isolation table 10 by detecting the gap between the installation floor side and the vibration isolation table side. The vibration detected by the acceleration sensor 33 is
By controlling the exciting current of the electromagnet actuator 35, the magnetic attraction force exerted on the magnetic body facing the electromagnet magnetic poles is controlled, thereby controlling the vibration on the vibration isolation table in the horizontal and vertical directions.

In this embodiment, the coil springs 36 for horizontal positioning are provided at six positions in the X, Y and θ directions as shown in the figure. And this spring element is X, Y,
By providing the vibration isolation table 30 in the θ direction, the vibration isolation table 30 is placed at a position balanced by the spring force in the center of the electromagnet gap in the horizontal direction.
Is positioned.

FIG. 18 shows an example of a control device for vertical control of a magnetic levitation vibration eliminator which also uses an air spring. The signal from the displacement sensor 38 is a PI (proportional integral) controller 3
9 is input to perform positioning control. The signal from the acceleration sensor 33 is input to the H∞ controller 40, and vibration isolation control is performed. This control device uses H∞ for control and P
It is configured by incorporating I (proportional and integral) control,
The H ∞ control is configured to include positioning stability control. Therefore, after ensuring the stability of positioning,
Sufficient vertical vibration isolation performance is achieved. Air spring 31
The controller 42 adjusts the air pressure from the air pressure source 43 according to the set value.

The vibration isolator of the second embodiment is an air spring,
Since most of the load of the machine mounted on the vibration isolation table is supported, the capacity of the electromagnet actuator is set to 1 as an example.
It can be reduced to / 10 or less. Regarding the positioning accuracy of the table positioning, since the PI control is performed by the electromagnet actuator, the positioning can be performed with an accuracy of several μm.
High-speed alignment is possible.

The control system shown in FIG. 19 is a modification of the control system shown in FIG. The signal from the displacement sensor 38 is input to a PI (proportional integral) controller 39, and the output thereof controls the air pressure by the air pressure controller 42 to position the vibration isolation table in the vertical direction. The signal from the acceleration sensor 33 is input to the H∞ controller 40, and the output thereof is input to the electromagnet actuator 41 via the power amplifier 44 to perform vibration isolation control. The H ∞ control of this embodiment is also configured to include the positioning stability control by the air spring, and while ensuring the positioning stability, sufficient vertical vibration isolation performance is achieved. .

According to this control system, since the positioning is performed only by the air spring, the capacity of the electromagnet actuator can be further reduced. However, since the positioning is performed by adjusting the pressure of the air spring, the positioning accuracy is lower than that of the electromagnet actuator,
There is also a problem that the response is slow.

[0060]

As described above, according to the magnetic levitation vibration isolator of the present invention, the vibration isolation performance in the vertical direction can be remarkably improved by combining the H∞ controller with the PI controller.

[Brief description of the drawings]

FIG. 1 is a plan view and an elevation view showing the structure of a magnetic levitation vibration isolator.

FIG. 2 is an explanatory diagram showing a feedback control system.

FIG. 3 is an explanatory diagram showing a model of a vibration isolation device.

FIG. 4 is a block diagram of a control system according to an embodiment of the present invention.

FIG. 5 is a diagram showing frequency characteristics of an H∞ controller and a PI controller according to an embodiment of the present invention.

FIG. 6 is a diagram showing step responses of the H∞ controller and the PI controller according to the embodiment of the present invention.

FIG. 7 is a diagram showing vibration transmissibility of an H∞ controller and a PI controller according to an embodiment of the present invention.

FIG. 8 is a diagram showing response characteristics when the table of the embodiment of the present invention is floating.

FIG. 9 is a diagram showing vibration transmissibility of acceleration on the installation floor and on the table according to the embodiment of the present invention.

FIG. 10 is a diagram showing the vibration states (acceleration) on the installation floor and the table according to the embodiment of the present invention.

FIG. 11 is a diagram showing impact characteristics when a disturbance is directly applied to the table according to the embodiment of the present invention.

FIG. 12 is an explanatory view showing the concept of the control device of the magnetic levitation vibration isolator of the present invention.

FIG. 13 is an explanatory diagram showing the concept of a control device of a conventional magnetic levitation vibration isolator.

FIG. 14 is a diagram showing a conventional vibration situation (acceleration) on a horizontally installed floor and on a table.

FIG. 15 is a diagram showing a conventional vibration situation (acceleration) on a vertically installed floor and on a table.

FIG. 16 is an elevation view of a magnetic levitation vibration isolator that also uses an air spring according to a second embodiment of the present invention.

17 is a plan view of the vibration isolation device shown in FIG.

FIG. 18 is an explanatory view showing the concept and the control device of the magnetic levitation vibration isolator together with the air spring shown in FIGS. 16 and 17;

FIG. 19 is an explanatory view showing the concept of a control device of another embodiment of the magnetic levitation vibration isolator which also uses an air spring.

[Explanation of symbols]

 11 Vibration Isolation Table 12 Electromagnet Actuator 13 Acceleration Sensor 14 Displacement Sensor 15 Control Device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naohide Haga 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa Inside the EBARA Research Institute, Inc. (72) Inventor Kenichi Yasuno 2-chome, Tobita, Chofu-shi, Tokyo 19 No. 1 Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Takayuki Mizuno 2-19-1 Tobita-cho, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Laboratory (72) Inventor Ryota Katamura Toita, Chofu-shi, Tokyo 2 No. 19-1 Kashima Construction Co., Ltd. Technical Research Center

Claims (4)

[Claims] 1. A table provided with a flat plate made of a magnetic material,
In a magnetic levitation vibration isolator comprising an electromagnet actuator that applies a magnetic attraction force to the flat plate to suspend and suspend the table, a displacement sensor that measures relative displacement between the flat plate surface and an electromagnet magnetic pole surface, and an absolute table An acceleration sensor for measuring acceleration and a control device for controlling an exciting current of the electromagnet based on signals of these sensors are provided, and the control device is provided between the flat plate surface and the electromagnet magnetic pole face based on a signal of the displacement sensor. The control law for controlling the gap and the control law for controlling the vibration based on the signal of the acceleration sensor are divided into the control law for controlling the vibration based on the signal of the acceleration sensor to control the stability of the relative displacement of the table. Magnetic levitation vibration isolator characterized by being included. 2. The control law for controlling the gap between the flat plate surface and the electromagnet magnetic pole surface based on the signal of the displacement sensor is PI.
2. The magnetic levitation according to claim 1, wherein the control law is (proportional integral) control, and the control law including the stability control of the gap in the control law for controlling the vibration is H∞ (infinity) control. Vibration isolation device. 3. The magnetic levitation vibration isolator according to claim 1, wherein the control device is configured by incorporating PI (proportional integral) control into H∞ (infinity) control. . 4. The magnetic levitation vibration isolator according to claim 1, wherein an actuator composed of an air spring is used in combination with an electromagnet actuator for suspending and suspending the table. The magnetic levitation isolation device described.