JP2860623B2 - Control device for anti-vibration table - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for a vibration isolation table, and more particularly to an air spring type or the like suitably used as a constituent unit of a semiconductor manufacturing apparatus for mounting an XY stage for exposure related to semiconductor manufacturing. The present invention relates to a control device for a shaking table.

[0002]

2. Description of the Related Art A group of devices that dislike vibration are mounted on an air spring type vibration isolation table. For example, it is an optical microscope or an XY stage for exposure. In particular, in the case of an exposure XY stage, it is necessary that the exposure XY stage be mounted on a vibration isolation table from which vibrations transmitted from the outside are removed as much as possible in order to perform appropriate and rapid exposure. This is because the exposure must be performed with the exposure XY stage completely stopped. Further, it should be noted that the exposure XY stage is characterized by an intermittent operation of step and repeat, and generates repeated step vibrations, which causes the air spring type vibration isolation table to shake. It is impossible to start the exposure operation even when such vibrations remain without being settled. Therefore,
The air spring type vibration isolation table is required to achieve a good balance between vibration isolation for external vibration and vibration suppression for forced vibration caused by its own operation.

As is well known, an active feedback control for detecting the displacement of the vibration isolation table and driving the vibration isolation table in accordance with the detected amount is introduced into the control device of the air spring type vibration isolation table. FIG. 11 shows a configuration of a control device of a conventional air spring type anti-vibration table that controls the vertical position of the anti-vibration table 8 using four air spring type support legs. Four air spring type support legs 21a
21d are arranged at four corners of the vibration isolation table 8. FIG. 12 shows a configuration of one air spring type support leg. In the figure, 1
Is a servo valve that supplies and exhausts air of the working fluid to and from the air spring 2, 3 is a position sensor that measures the vertical displacement of the support 4, 5 is an acceleration sensor that measures the vertical acceleration of the support 4, 6 is The mechanical springs 7 for preloading are viscous elements expressing the viscosity of the air spring 2, the mechanical spring 6, and the entire mechanism (not shown), and the mechanism composed of these element parts is called an air spring type support leg. As shown in FIG. 11, four air spring type support legs are used to support the vibration isolation table 8 in the vertical direction, and the component part numbers of the legs are denoted by a, b, c, and d. Distinction.

Next, the configuration and operation of the feedback device 15 for the air spring type support leg 21 shown in FIG. 12 will be described. First, the output of the acceleration sensor 5 passes through a low-pass filter 9 having an appropriate amplification factor and time constant, and is negatively fed back to a stage preceding the voltage-current converter 10 for opening and closing the valve of the servo valve 1. The mechanism is stabilized by the acceleration feedback loop. That is, damping can be provided. Further, the output of the position sensor 3 passes through the displacement amplifier 11 and is input to the comparison circuit 12. Here, it is compared with a target voltage 13 equivalent to a target position of the support 4 with respect to the ground, and becomes a deviation signal e. This deviation signal e is output to the PI compensator 14
To excite the voltage-to-current converter 10. Then, the pressure in the air spring 2 is adjusted by opening and closing the servo valve 1, and the support base 4 can be held at a predetermined position without a steady deviation. Here, P means proportional and I means integral operation.

[0005]

When four air spring type support legs are used, generally, four air spring type support legs and feedback devices 15a to 15d for these support legs are shown in FIG. As shown, each has the same configuration as that of FIG. In contrast, FIG.
In the case of 3, the feedback devices 15a to 15c for the air spring type support legs 21a to 21c have the same device configuration as the feedback device 15 of FIG. 12, but only the feedback device for the air spring type support leg d is the feedback device 15a, Unlike 15b and 15c, a pseudo feedback device 15d is configured. That is, the pseudo feedback device 15d is the feedback device 1
5c, the output signal of the PI compensator 14c is taken out, the output signal of the acceleration sensor 5d is added to the signal that is negatively fed back through the low-pass filter 9d, and the voltage-current exchanger 10c is added.
d is driven. The reason for this is that, for cost reduction, the position sensor 3
This is to deal with the removal of d.

More specifically, the air spring type vibration damping table and its control device are large-scale and therefore high in cost. Since it is an industrial device, the demand for cost reduction is not as severe as information devices such as printers and plotters and consumer devices, but it cannot be ignored. In the control device of the air spring type anti-vibration table of FIG. 11, the element parts having a large ratio to the cost are the actuators of the air springs 2 a to 2 d, the servo valves 1 a to 1 d, the position sensors 3 a to 3 d,
These are acceleration sensors 5a to 5d. Among them, the actuators of the air springs 2a to 2d and the servo valves 1a to 1
Since d is a driving means for generating a supporting force of the vibration isolation table 8, it cannot be removed. Therefore, the cost was reduced by removing the position sensor 3d. In this case, since the feedback device 15d based on the measurement value of the position sensor 3d cannot be configured, the structure of the control device is devised, and the displacement amplifier 11d,
Comparison circuit 12d, target voltage 13d, and PI compensator 14d
13, the output of the PI compensator 14c is connected by a signal line 19 and added as an input signal of the voltage-current converter 10d, so that the configuration shown in FIG. 13 is obtained. That is, the signal of the PI compensator 14c for the air spring type support leg 21c is borrowed to drive the air spring type support leg 21d. In this case, if a disturbance that moves the support tables 4c and 4d in the same direction acts on the anti-vibration table 8, control is performed on the air-spring support legs 21c and 21d so as to pull them back in the opposite direction. . However, the supports 4c and 4
When disturbance is applied such that d moves in opposite directions, there is a problem that good vibration suppression performance is not exhibited.

More specifically, the air spring type support leg 21c
And 21d are arranged close to each other, and the anti-vibration table 8 with respect to the vertical axis.
Under the condition that the inclination does not occur frequently, sufficient performance can be realized even with the configuration of the pseudo feedback device 15d shown in FIG. However, the air spring type supporting legs 21c and 21c
When the interval d is large and the rotational movement of the vibration isolation table 8 is frequent, the vibration isolation and vibration suppression performance cannot be realized in an appropriate balance with the device configuration as shown in FIG. The reason can be easily understood by considering the spatial motion of the vibration isolation table 8 as a rigid body. First,
When the whole anti-vibration table 8 is translated in the vertical direction,
Since the displacement of d and the displacement of the support 4c are the same, even if the position sensor for measuring the displacement of the support 4d is removed as shown in FIG. The driving may be performed by borrowing the compensation signal. However, what happens in the case of a rotary motion in which the entire vibration isolation table 8 is inclined with respect to the vertical axis? For example, let us consider a case where some disturbance acts on the anti-vibration table 8, causing a rotational movement in which the support table 4 c moves vertically upward and the support table 4 d moves vertically downward. Each electric signal in the feedback device 15c has an operation of pulling the support 4c downward, and this signal has a polarity opposite to that of the operation that has to drive the support 4d upward. Therefore, as shown in FIG. 13, the operation of guiding the signal in the feedback device 15c into the pseudo feedback device 15d and positioning the support 4d in the vertical direction is performed after the sufficient time has passed, and the vibration isolation table 8 returns to the equilibrium position. However, it is impossible to correct the position and orientation of the vibration isolation table 8 in a short time.

Next, the vibration damping effect of the vibration caused by the operation of the device mounted on the anti-vibration table will be considered. In general, the natural frequency of the air spring type support leg 21 as shown in FIG. 12 is set in a low frequency range, and the influence of vibration is eliminated by lowering the external vibration transmissibility in a high frequency range. However, vibration generated by a device mounted on the support leg 21 cannot be effectively removed. This is because the reaction force generated by the operation of driving and stopping the device causes the support base 4 to oscillate in a low frequency range. As shown in FIG. 12, the servo valve 1 is incorporated in the support leg 21. The pressure in the air spring 2 is automatically adjusted by adjusting the throttle in response to the output of the position sensor 3, and the position of the support base 4 is adjusted. The fluctuation has been corrected. However, the support leg 2 shown in FIG.
In the air spring type anti-vibration table using a plurality of 1s, it has been pointed out that the response is extremely poor due to the independent feedback devices of the support legs.

In the control device of the air spring type vibration isolation table,
The supporting legs 21 shown in FIG. 12 are arranged at the four corners of the large anti-vibration table to restrict the horizontal and vertical movement of the anti-vibration table. However, the support leg 21 has its own feedback closed. In other words, the support legs arranged at the four corners of the vibration isolation table have no control relationship with each other, and each is an independent feedback device. However, there is a problem that the rigidity of the vibration isolating table has six degrees of freedom of motion, and these supporting postures cannot be properly controlled if the support legs arranged at the four corners of the vibration isolating table are independently controlled. For example, consider a situation in which a vibration-free table in a power-off state is positioned to a desired position by activating a feedback device. In the configuration of the independent feedback device, an operation in which the posture of the anti-vibration table in the indeterminate posture is changed to the target position and various posture changes are repeated to settle to the final position. Therefore, there has been a problem that it takes a considerable amount of time before the vibration isolation table becomes functional. Also, when driving the equipment mounted on the vibration isolation table, it is performed not only at the limited position on the vibration isolation table but also everywhere on the vibration isolation table. In this case, the driving of the device is a disturbance to the vibration isolation table, which gives the vibration isolation table various types of shaking.
However, if the support legs 21 arranged at the four corners of the vibration isolation table are independently controlled, it has not been possible to accurately suppress various types of shaking that the driving of the device gives to the vibration isolation table. further,
The anti-vibration table must be provided with a balance between the two opposing functions of isolating vibrations from the floor and damping the vibrations generated by the mounted equipment. The vibration damping performance is sacrificed, and there is a problem that the vibration damping performance is impaired if the feedback device is adjusted with emphasis on the vibration damping performance.

As a method for dealing with this problem, for example, Japanese Patent Application Laid-Open No. Hei 4-24811 discloses that the operation of the vibration damping device is started immediately before the equipment on the vibration damping table is accelerated, and that the vibration damping device operates during the period of constant velocity movement. Stop the operation, restart the vibration suppression device just before deceleration,
There has been proposed a configuration of an air spring type anti-vibration table characterized in that the operation is stopped immediately after stopping. However, this device has a disadvantage that it requires two control systems for vibration suppression and vibration isolation.

As a control for the air spring type vibration isolation table, a control method based on state feedback is disclosed in JP-A-3-28910 in addition to the above. However, the state feedback is a control that strongly depends on a physical parameter to be controlled, and is not practical for industrial equipment. On the other hand, the present invention is directed to a control device in which a feedback device including a minor loop of acceleration and a PI compensation loop for position is independently provided for each of the air-spring-type support legs. Therefore, it is a practical technical content for industrial equipment.

SUMMARY OF THE INVENTION The present invention has been made to eliminate or reduce the above-mentioned drawbacks, and a control device capable of suitably controlling the attitude of a vibration isolation table even when one position sensor is removed for cost reduction. The primary purpose is to provide.

According to the present invention, furthermore, various types of shaking which the drive of the equipment mounted on the vibration isolation table gives to the vibration isolation table can be accurately suppressed, and the balance with vibration isolation from the floor is also improved. A second object is to provide a suitable control device.

[0014]

According to a first aspect of the present invention, there is provided a control apparatus for a vibration isolation table according to a first aspect of the present invention. This is for positioning a flat anti-vibration table supporting a place at a vertical target position without a steady deviation, and is provided corresponding to the first to third support legs, and each of the support legs is provided. A first to a third position sensor for detecting a vertical position of the vibration isolation table at a position supported by the first and fourth support legs; A first to a fourth acceleration sensor for detecting a vertical acceleration of the vibration isolating table at a part, and the first to third support legs respectively independently based on outputs of the corresponding position sensor and acceleration sensor. First to third feedback devices for servo-controlling the height of the shaking table support position; Based on the first to third positional deviation output obtained by comparing the output of the first to third position sensors, or the output of the vertical target position signal, said anti-vibration table,
Calculating means for calculating a vertical position or positional deviation at a position supported by the fourth support leg, and a vibration isolation table based on the output from the calculating means and the fourth acceleration sensor 4th servo control of the height of the support position
And a feedback device.

In a preferred embodiment of the present invention, the first to fourth support legs are arranged at four corners of the anti-vibration table in a counterclockwise direction, and correspond to each of the first to third support legs. The position signals, which are the outputs of the position sensors, are sequentially represented by z _a , z _b ,
when a z _c, wherein the calculating means, the position signal z _d corresponding to the fourth supporting leg, formula _{z d = z a -z b +} z c
It is calculated by:

According to a second aspect of the present invention, in order to achieve the second object, a flat anti-vibration table horizontally supported by at least two support legs arranged at positions spaced apart from each other. A position sensor provided for each support leg to detect the vertical position of the anti-vibration table at a position supported by each support leg in order to position the support leg at a vertical target position without a steady deviation. And an acceleration sensor for detecting a vertical acceleration of the anti-vibration table at a position supported by each support leg, and an output of the acceleration sensor provided for each of the support legs and corresponding to each of the support legs. Negative feedback to the previous stage of the voltage-current converter for stabilizing the servo mechanism, and comparing the position sensor output with a target value to obtain a deviation signal and passing it through a compensator, then the voltage-current converter And a feedback device for guiding In the control device, there is provided a mode extraction circuit that calculates a translation deviation signal and a rotation deviation signal of the vibration isolation table based on at least two deviation signals that are comparison outputs of a target value and a position sensor corresponding to each of the support legs, A compensator was replaced with a compensator for the translation error signal and the rotation error signal, and a distribution circuit for redistributing the output of the compensator to each voltage-current converter in the feedback device as a support leg driving signal was provided. It is characterized by:

The translation error signal and the rotation error signal are
For example, in xy coordinates defined in the horizontal plane of the vibration isolation table, either in the x or y direction, or xy
Calculate in both directions. Further, the control device according to the second aspect is a servo valve for adjusting the pressure of the air spring of the support leg through a pseudo-differential circuit having an appropriate time constant by driving a device mounted on the vibration isolation table. A function of suppressing vibration applied to the vibration isolation table by superimposing it on the drive signal can be provided.

Further, in a third aspect of the present invention, the outputs of the first to third position sensors or the first to third position deviation outputs obtained by comparing these outputs with a vertical target position signal. A motion mode extraction circuit that outputs first to third motion mode deviation signals corresponding to a vertical translational motion to be taken by the anti-vibration table and a rotational motion about two different axes, based on A PI compensator for performing PI compensation on a third motion mode deviation signal, and first to fourth corresponding to displacement amounts to be taken by the first to fourth support legs based on an output of the PI compensator. And a motion mode distribution circuit that outputs a fourth displacement signal. The first to fourth displacement signals are output based on the first to fourth displacement signals and a detection signal negatively fed back from the first to fourth acceleration sensors. A drive signal is output to the supporting leg of the vehicle.

The supporting legs are of an air spring type,
Alternatively, a device using a voice coil motor as an actuator can be used.

[0020]

According to the first aspect of the present invention, three support legs having both a position sensor and an acceleration sensor and one anti-vibration leg having only an acceleration sensor and removing the position sensor are formed in a flat plate shape. In order to position the vibration isolation table at the vertical target position without a steady deviation, each feedback device for the three vibration isolation legs and the position sensor having only the acceleration sensor are arranged at the four corners of the vibration isolation table. A control device for the anti-vibration table includes a feedback device with a position signal restoration circuit for one of the anti-vibration legs. The control device of the vibration isolating table including the feedback device with the position signal restoring circuit has an effect that the position signal of the removed part can be restored despite the position sensor being removed, and the signal is directly measured by the position measurement value. And a feedback loop can be formed.

In the conventional control apparatus for a vibration isolation table, a feedback device is incorporated for each of a plurality of supporting legs that support the vibration isolation table, and there is no mutual relationship. In other words, only the local position of the support leg installation is individually feedback-controlled, and there is no function of suppressing and controlling the macro posture change of the entire vibration isolation table. With respect to such an apparatus configuration, in the second embodiment of the present invention, the posture change of the entire vibration isolation table is detected, optimal compensation is applied for each motion mode, and finally the driving force is applied to the actuator of each support leg. Distribute,
The control device of the anti-vibration table is provided. More specifically, it is as follows.

First, the signal of the acceleration sensor for detecting the acceleration of the vibration isolation table is negatively fed back to the stage preceding the voltage / current converter for driving the servo valve of the supporting leg, thereby stabilizing the mechanism. Two support legs are prepared and arranged while maintaining a spatial positional relationship for correcting a horizontal posture. Next, a deviation signal is obtained by comparing the output of the position sensor provided on each support leg with a target value. The two deviation signals are guided to a mode extraction circuit to obtain respective deviation signals representing the translation and rotation of the vibration isolation table. Subsequently, the translation deviation signal and the rotation deviation signal are guided to a compensator most suitable for each motion control, and the signal is shaped. Finally, their compensator outputs are directed to a distribution circuit. There, a signal distribution for driving the actuators of the two support legs is made based on the outputs of the two compensators.

According to the third aspect of the present invention, according to the control apparatus for the vibration isolation table with the decoupling circuit, even if one position sensor in the four air spring type vibration isolation legs is removed for cost reduction. , Three types of motion modes indicating one type of translational motion and two types of circuit motion are extracted from the outputs of the three position sensors, individually compensated for them, and finally 3 or 3 Since drive commands are given to the four actuators, decoupling of each motion mode is achieved. Therefore, the cost can be reduced and the vibration damping performance can be increased as compared with the conventional case.

[0024]

Embodiment 1 FIG. 1 shows a configuration of a control device of an air spring type vibration isolation table with a position signal restoration circuit according to a first embodiment of the present invention. 13 showing a control device of a conventional air spring type anti-vibration table is that a feedback device 17 with a position signal restoration circuit is provided instead of the pseudo feedback device 15d. This feedback device 1 with a position signal restoring circuit
7, corresponding to the removal of the position sensor, feedback devices 15a, 15b,
The position signal is restored by using the position signals z _a , z _b , and z _c in the position signal 15c as inputs to the position signal restoration circuit 16. This circuit output is a position signal z equivalent to the vertical displacement of the support 4d.
_d, and the position error signal e _d guides the signal z _d to the comparison circuit 12d is obtained. Further, the position error signal _ed is P
The output signal is guided to the I compensator 14d, and the output signal and the output of the low-pass filter 9d are added to excite the voltage-current converter 10d. Here, the position signal restoration circuit 1
The specific circuit configuration of No. 6 is simple. As an example, this can be realized using two operational amplifiers and several resistors as shown in FIG. As shown in the figure, the input signals to the position signal restoration circuit 16 are z _a , z _b , and z _c , and the input resistance and the feedback resistance of each operational amplifier are the same. At this time, the output z _d of the position signal restoration circuit 16 is given by the following equation (1).

[0025]

(Equation 1) The fact that the position error signal can be reproduced as if the position sensor is present by the calculation of Equation 1 despite the removal of the position sensor of the air spring type support leg 21d will be described below.

First, the air spring type support leg 21 as viewed from above
The coordinates of a to 21d are determined as shown in FIG. Here, the displacement Z in the vertical direction is determined from the same reference plane and is represented by z _a to z _d . In addition, vertical translational motion, rotational motion about the x axis, y
The modes of the rotational movement around the axis are defined as z _g , zθ _x , and zθ _y as distances from the reference plane. At this time, z _a ~
z _d is _z g, zθ _x, can be expressed as equation 2 by using the z [theta] _y.

[0027]

(Equation 2) Equation 3 is obtained by performing matrix notation.

[0028]

(Equation 3) Since the vibration isolation table 8 is a rigid flat plate, a position z at an arbitrary in-plane position (x, y) can be determined based on three position measurement values. In Equation 3, since the position measurement values z _a , z _b , and z _c can be obtained, the missing value z _d can be restored by Expression 1 using these three position measurement values.

If the position sensors 3a, 3b, 3c are set on the same reference plane, z _a , z indicating the absolute position
_b, and _{z c,} the position error signal _{e a, e b,} 1 pair and _{e c} 1
Corresponding to Therefore, Equation 4 is obtained.

[0030]

(Equation 4) Now, one performance of the control device of the air spring type anti-vibration table with the position signal restoration circuit shown in FIG. 1 will be clarified by comparison. FIG. 4 shows a state in which the anti-vibration table 8 in the stationary state is positioned to the target position, that is, the air-spring-type support legs 21 after power is turned on.
a, 21b, the position deviation signal e _a of the vibration isolating table support position.
shows the start-up characteristics of e _b. FIG (a) is the case of the conventional controller shown in FIG. 13, FIG. (B) is the case of the control apparatus according to the present invention shown in FIG. 1, the position error signal e _a from the time of each power-on , _Eb converge. As is clear from FIG. 4, it is understood that the use of the control device according to the present invention has improved the stabilization.

Although not shown, according to the control device of the air spring type vibration isolating table with the position signal restoring circuit of FIG. 1, the in-plane rotation of the vibration isolating table 8 adopts the configuration of the control device of FIG. It can be suppressed better than the case.

Modification of the First Embodiment In the first embodiment, in the control device of the air spring type anti-vibration table using the air spring as an actuator, the position signals of the parts from which the position sensors have been removed for cost reduction are obtained at three positions. The control device restores the signal by calculating the signal, and uses the signal to perform feedback as if a position sensor exists. Therefore, the present invention is not limited to a control device for an active vibration isolation table using an air spring as an actuator. For example, application to a control device of an active vibration isolation table using a voice coil motor as an actuator also falls within the scope of the present invention.

In the feedback device 17 with a position signal restoring circuit in FIG. 1, the inputs to the position signal restoring circuit 16 are displacement amplifiers 11a and 11a which indicate the absolute value of the position.
b, 11c. However, the input to the 16 may be a position deviation signal _{e a, e b, e c} . The control device configuration in this case is as shown in FIG. In the figure, there is provided a feedback device 17 'with a position deviation signal restoring circuit which directly leads the output signal of the position deviation signal restoring circuit 16' to the PI compensator 14d. However, the circuit configuration of the position error signal restoration circuit 16 'is
Is the same as In the case where the apparatus configuration shown in FIG. 5 is adopted, it is necessary to apply an offset voltage to the voltage-current exchanger 10d to steadily supply a current, for example, in order to apply a steady driving force to the air spring type support leg 21d. There is.

Further, in FIGS. 1 and 5, in the mechanism in which the air spring type support legs 21a to 21d are arranged in this order counterclockwise at the four corners of the anti-vibration table 8, the position sensor of the air spring type support legs 21d is removed. FIG. 9 shows a control device to cope with the case where the operation is performed. Of course, when any one of the position sensors of the air spring type support legs 21a to 21d is removed, the position signal may be restored so as to satisfy the equation (1).

In each of the embodiments shown in FIGS. 1 and 2, the control system is constituted by an analog operation circuit, but a part or all of them may be replaced by a digital operation device such as an electronic computer. .

Embodiment 2 FIG. 6 shows a configuration of a control device of an air spring type vibration damping table according to a second embodiment of the present invention. Although not shown, devices such as an exposure XY stage are mounted on the anti-vibration table 8. In the figure, the vibration isolation table 8 has four support legs 21a,
21b, 21c and 21d, the vertical z direction and the horizontal x direction
And support in the y-direction. However, for simplicity of description, only the case where control in the horizontal y-axis direction is performed using the support legs 21a and 21b will be described.

The operation will now be described. The outputs of the acceleration sensors 5a and 5b pass through the low-pass filters 9a and 9b and are negatively fed back to the previous stage of the voltage-current converters 10a and 10b to stabilize the mechanism of each support leg. Position sensor 5a,
The output of 5b is converted into an electric signal by displacement amplifiers 11a and 11b and guided to comparison circuits 12a and 12b. These signals target voltage 13a, 13b and the compared error signal e _a, a e _b. The deviation signal e _a, e _b is the anti-vibration table 8
Are input to a mode extraction circuit 22 that calculates a translation error signal T in the y-axis direction and a rotation error signal R about the z-axis. Translation
Rotation deviation signal T, R compensation signal c _T is guided to the compensator 14a, 14b, the c _R. These compensation signals c _T , c
_R is guided to the distribution circuit 23. Here, the compensation outputs as the translational and rotational components are output to the actuators 24a and 24a.
An operation of distributing to b is performed. However, servo valve 1
The actuator including the air spring 2 is referred to as an actuator.

Although not described, the support leg 21 for supporting in the x-axis direction is used in the vibration damping device for the air spring type vibration damping table of this embodiment.
Needless to say, c and 21d are also vibration damping devices having a feedback provided with a mode extraction circuit 22 and a distribution circuit 23 as shown in FIG. In the case where there is no mode extraction circuit 22 and distribution circuit 23 shown in the drawing, the outputs of the comparison circuits 12a and 12b are not input to the compensators 14a and 14b, and the outputs of the compensators 14a and 14b are low-pass filters 8a and 8b. 11 and 12 are added to the outputs of the voltage-current amplifiers 9a and 9b, respectively, as described above with reference to FIGS. 11 and 12, independent feedback is applied to each support leg 21. This is the conventional air spring. It will also be apparent that the configuration of the control device of the vibration damping table is provided.

Now, the performance of the control device of the air spring type anti-vibration table shown in FIG. 6 will be shown in comparison. FIG. 7 shows a case in which a signal application terminal (not shown) is newly provided at the previous stage of the voltage-current converters 10a and 10b, and a step signal for causing the anti-vibration table 8 to rotate around the z-axis is given. Indicates the output of the mode extraction circuit 22. That is, the state of the translation error signal T and the rotation error signal R are shown. The performance when independent feedback is applied to each support leg is shown in FIG.
Also appear significantly. On the other hand, in FIG. 6B showing the performance of the control device of the air spring type vibration damping table of the present embodiment in which the mode extracting circuit 22 and the distribution circuit 23 are inserted, the appearance of the translation error signal T is almost negligible. However, it can be seen that the amplitude of the rotation deviation signal R is also significantly suppressed. Also, the half cycle of the step-like electric signal to the signal application terminal is 5 [sec], but the response waveform T,
R has not converged within this period. However, in FIG. 4B, convergence to zero is achieved within this period.

FIG. 8 shows the response when the anti-vibration table 8 is step-driven so as to translate in the y-axis direction. This case is also the same as FIG. That is, both the translation error signal T and the rotation error signal R shown in FIG. 9B are smaller in amplitude suppression and response than the response (a) when independent feedback is performed for each support leg. The settability has been improved. Therefore, the superiority of the control device of the air spring type anti-vibration table of the present embodiment is excellently shown.

Next, an apparatus configuration for eliminating a trade-off between vibration isolation and vibration suppression performance will be described. FIG. 9 shows the support leg 2 shown in FIG.
1 shows a servo block diagram. Using the symbols shown in the figure, displacement x, target value r _o , disturbance f _dis and auxiliary input V
The relationship between _FFs is as follows:

[0042]

(Equation 5) The meanings of the symbols used are shown below. x [m]: displacement r _o [V]: target value f _dis [N]: disturbance V _FF [V]: auxiliary input M [Kg]: Mass C [Nsec / m]: viscous friction coefficient K [N / m : stiffness coefficient K _I [Nsec / V]: voltage-current amplifier and integral gain K _a, including servo valve characteristic [Vsec ² / m]: acceleration feedback gain T '[sec]: the time constant of the PI compensator [delta] [V / V]: Positional gain s: Laplace operator Here, the portions shown within the dotted lines in the figure include the servo valve and the mechanical characteristics, and the transfer function is given by the following equation.

[0043]

(Equation 6) Next, when turning on the acceleration feedback, the transfer function from V _c to the displacement x is expressed by the following equation.

[0044]

(Equation 7) Accordingly, the acceleration feedback gain K _a is seen to have a function to stabilize the whole mechanism working to increase the viscosity term. In the present embodiment, the mechanism parameters M, K,
The acceleration feedback is applied to the support leg 21 having C, and the transfer function expressed by the above equation is regarded as a control target again.

As shown in equation (1), V _FF is the disturbance f
A voltage applied to an auxiliary input terminal for reducing or eliminating the influence of _dis on the displacement x. Here, the signal waveform of the auxiliary input V _FF is if it is devised, it becomes possible to cancel the second term by the equation third term. Now, since the disturbance f _dis is caused by driving the mounted device on the vibration isolation table 8 in FIG. 6, its waveform generally has a bang-bang shape. This is because the mounted device is positioned after rapid acceleration / deceleration.
Since the bang-bang waveform is represented by superposition of step waveforms, it is assumed here that the disturbance f _dis is a step waveform. Further, since the device mounted on the vibration isolation table 8 is driven by an actuator such as a DC servo motor, if the disturbance f _dis cannot be directly measured, the disturbance f
_dis is regarded as the electric signal itself when the actuator is driven, and can be used as an input of the auxiliary input _VFF . However, the orders of the numerator polynomials of the second and third terms of Equation 1 are 2 and 1, respectively, and the step-like disturbance f
_{When dis} is applied, if the step-like voltage _VFF is applied, the influence of f _dis on the displacement x including the dynamics cannot be removed. Therefore, the input signal is V _FF ′
= SV _FF is again input as the third term of Equation (1). However, the use of a differentiator is not preferable because it amplifies high frequency noise. In reality, a pseudo-differentiator is formed by adding a low-pass filter having an appropriate time constant T. That is, the following equation is used.

[0046]

(Equation 8) Here, a comparison between the response of the displacement x when the auxiliary input _VFF shown in the third term of the above equation is added in the presence of the disturbance _{fdis and} the absence of the input is shown. FIG. 10A shows the auxiliary input V
In the case of _FF ≠ 0, (b) shows respectively the case of _{V FF} = 0. Obviously, the displacement x in FIG. 3A is well suppressed. Therefore, a drive signal of a device mounted on the vibration isolation table 8 supported by the air spring type support leg is applied to a stage preceding the voltage-current converter driving the servo valve through an appropriate pseudo-differential circuit. Can be said to be effective.

Modifications of Embodiment 2 The present invention can be variously modified without departing from the gist thereof. The modification will be described below. In the second embodiment, a feedback configuration in which two support legs 21 are used to effectively suppress horizontal translation and rotational movement in a horizontal plane has been described. This feedback configuration is effective even with only one pair. Needless to say, when two pairs are prepared and used one by one in the orthogonal direction, all the movements in the horizontal direction can be controlled. At this time, the remaining degrees of freedom to be controlled are a total of three degrees of freedom of vertical translation and tilt from the vertical axis, that is, tilting. Although the feedback device configuration for this exercise mode is not shown,
This can be easily realized by extending. That is, the mode extraction circuit 22 and the distribution circuit 23 shown in FIG. 6 are both two-input two-output arithmetic circuits. However, in a feedback device that vertically supports the vibration isolation table 8, at least three-input three-output arithmetic is performed. The mode extraction circuit and the mode distribution circuit may be used. Further, in the case of realizing the control taking the flexibility of the vibration isolation table 8 into consideration, a four-input four-output mode extraction circuit and a mode distribution circuit are provided.

Embodiment 3 FIG. 14 shows the configuration of a decoupling control device for an air spring type vibration damping table according to a third embodiment of the present invention. The difference from the control device of the conventional air spring type anti-vibration table shown in FIG. 11 is that the displacement amplifier 11d, the comparison circuit 12d, the target voltage 13d, the PI compensator correspond to the removal of the position sensor 3d for cost reduction. 14d is also removed, and a new motion mode extraction circuit 16
And the motion mode distribution circuit 17 are inserted. A control device in which the motion mode extraction circuit 16 and the motion mode distribution circuit 17 are inserted in the feedback device is called a decoupling control device. Here, the mode extraction circuit 16 is a three-input, three-output arithmetic circuit, and the mode distribution circuit is a three-input, four-output arithmetic circuit, and is expressed by equations (9) and (10) using the symbols shown.

[0049]

(Equation 9)

[0050]

(Equation 10) First, the operation will be described. Air spring type support legs 21a-2
The motion modes of the rigid flat vibration isolator 8 supported by the four 1d are two types: a vertical translational motion and a rotational motion about two orthogonal axes provided in a horizontal plane. The vertical position signal of the rigid vibration isolation table 8 is transmitted to the position sensors 3a and 3a.
Since measurement is performed using b and 3c, three types of motion modes of the vibration isolation table 8 can be extracted using the measured values at three locations. A circuit exercise mode extraction circuit 26 having this function, the comparing circuit 12a, 12b, the position deviation signal which is the output signal of 12c _{e a,} e b, the equation (9) to _{e c} as input motion mode extraction circuit 26 When applying operation, the output motion mode deviation signal z [theta] _x representing the rotational motion and motion mode deviation signal z _g representing the _translation, the z [theta] _y. Subsequently, the motion mode deviation signals z _g , zθ _x , and zθ _y are respectively output to the PI compensator 1.
4a, 14b, and 14c. In the control device of the conventional air spring type anti-vibration table shown in FIG. 11, a function of individually matching the outputs of the position sensors 3a to 3d with the target voltages 13a to 13d is imposed on the PI compensators 14a to 14d. . However, the PI compensators 14a and 14 shown in FIG.
b, 14c is motion mode deviation signal _z g, z [theta] _x, z [theta]
A function for making each of the _y values to be zero is set.

Next, the PI compensators 14a, 14b, 14c
Are the motion mode compensation signals c _g , cθ _x ,
the cθ _y. These signals are compensation signals for one type of translational motion and two types of rotational motion, which are motion modes of the vibration isolation table 8. Moreover, this signal becomes the input of the motion mode distributing circuit 27, the output signal _s a according to operation of the equation 10 _formula, s _b, s c, the _{s d.} These signals are supplied to voltage / current amplifiers 10a, 10b, 10 for adjusting the pressure of the air springs 2a, 2b, 2c, 2d of the four air spring type support legs.
c, input signals to 10d. However, as described above, the outputs of the acceleration sensors 5a, 5b, 5c, and 5d pass through the low-pass filters 9a, 9b, 9c, and 9d in order to provide appropriate diping to the mechanism of the air-spring support leg. Negative feedback is provided to the input stages of the converters 10a, 10b, 10c, and 10d.

After all, when four air springs 2a, 2b, 2c and 2d as actuators are arranged at the four corners of the vibration isolation table 8 and three position sensors 3a, 3b and 3c are provided, the position deviation signals _{e a, e b,} translation from _{e c} 1
After extracting the seeds and the two kinds of rotational movements, applying PI compensation to them, and using the three compensation signal outputs, the four air springs 2a, 2a,
The decoupling control device is configured to distribute a compensation output signal to generate a driving force to 2b, 2c, and 2d.

The motion mode extraction circuit 26 expressed by the equation (9) and the motion mode distribution circuit 2 expressed by the equation (10)
7 can be easily realized by using an operational amplifier and several resistors. For example, the exercise mode extraction circuit 26 in FIG.
The exercise mode distribution circuit 27 may be configured as shown in FIG. Exercise mode extraction circuit 26 and exercise mode distribution circuit 27
However, the reason why they can be expressed as Expressions 9 and 10 is as follows. First, the coordinates of the four air spring type support legs as viewed from the upper surface are determined as shown in FIG. Here, the displacement z of the anti-vibration table 8 for the vertically supported object is determined from the same reference plane.
and _{a ~z d.} In addition, the motion modes of the vertical translation, the rotation about the x axis, and the rotation about the y axis are defined as g, θ _x , and θ _y as distances from the reference plane. At this time,
z _a to z _d is g, θ _x, can be expressed as equation (11) using the theta _y.

[0054]

[Equation 11] Equation 12 is obtained by performing matrix notation.

[0055]

(Equation 12) The above equation means that the displacements z _a , z _b , z _c , and z _{d of the} four parts are obtained by the calculation using the motion modes g, θ _x , and θ _y as inputs. Therefore, the realization of this operation is the motion mode distribution circuit 27 shown in Expression 10.

[0056] Furthermore, since not be acquired displacement z _d by removal position sensor 3d, it becomes the number 13 from equation equation (12), to obtain the number 14 expression when obtaining an inverse matrix.

[0057]

(Equation 13)

[0058]

[Equation 14] Equation 14 shows that the motion modes g, θ _x , and θ _y can be calculated by calculations using three displacements z _a , z _b , and z _c as inputs. Equation 9 shows the result of this calculation. The exercise mode extraction circuit 26.

Finally, one performance of the air spring type vibration isolation table shown in FIG. 14 will be clarified by comparison. FIG. 19B is a graph showing a response when a disturbance is applied to the vibration isolation table 8 in a steady state by applying an electric signal. Assuming that the rectangular waves having a frequency of 0.02 [Hz] applied to the voltage-current converters 10a and 10d and 10b and 10c have opposite phases to each other, FIG.
The convergence state of the motion mode deviation signals z _g , zθ _x , and zθ _y when a step-like disturbance is applied around the y-axis is shown with reference to FIG. For comparison, FIG. 10A shows the convergence of the motion mode deviation signal when the above-described step-like disturbance is applied when the conventional control method is adopted.
However, the conventional control method means a displacement amplifier 11d and a comparison circuit 12d in accordance with the removal of the position sensor 3d in FIG.
13, the target voltage 13d and the PI compensator 14d are also removed, and instead, the output of the PI compensator 14c is connected by a signal line 19 and the input of the voltage-current converter 10d is shown in FIG.

According to FIGS. 19 (a) and (b), a step-like disturbance is applied around the y-axis, so that the motion mode deviation signal zθ _y is predominant in any case. FIG. 13B shows that the excitation of the amplitude is suppressed. Excitation of the non-predominant modes z _g and zθ _x is also better suppressed when decoupling is performed. Therefore, according to the decoupling control device of the air spring type anti-vibration table of the present embodiment, it is possible to reduce the cost by removing the position sensor 3d and to improve the settability with respect to the disturbance to the anti-vibration table 8. be able to.

Embodiment 4 FIG. 15 shows a configuration of a decoupling control device according to a fourth embodiment of the present invention. In the third embodiment, in a control device of an air spring type anti-vibration footrest using an air spring as an actuator, three types of motion modes are extracted from three position sensor signals, and after these are individually compensated. The compensation signal is distributed so as to generate a driving force for the four air springs. That is, the exercise mode extraction circuit 26 has a configuration of 3 inputs and 3 outputs, and the exercise mode distribution circuit 27 has a configuration of 3 inputs and 4 outputs.

However, the motion mode distribution circuit 27
May be a three-input three-output exercise mode distribution circuit 27 'as shown in FIG. In the figure, decoupling control is configured so that the three air-spring-type support legs 21a to 21c operate cooperatively, and control for the remaining air-spring-type support legs 21d is the same as that of the decoupling control. Is an independent feedback device. This will be described more specifically below.

As shown in FIG. 15, the feedback devices for the three air spring type support legs 21a to 21c include:
A three-input three-output exercise mode extraction circuit 26 and a three-input three-output exercise mode distribution circuit 27 'are inserted. In the feedback device of the remaining air spring type support leg 21d, a position signal restoring circuit 18 for newly calculating the vertical displacement of the support base 4d from the outputs of the displacement amplifiers 11a to 11c is newly prepared. Here, a specific circuit of the position signal restoration circuit 18 can be easily realized by using two operational amplifiers and several resistors.

In each of the embodiments shown in FIGS. 14 and 15, the control system is constituted by an analog operation circuit, but a part or all of the control system may be replaced by a digital operation device such as an electronic computer. . Further, the present invention is a control device in which the motion mode extraction circuit 26 and the motion mode distribution circuit 27 are inserted into the feedback device to make it non-interfering, so that the active removal using the air springs 2a to 2d as actuators is achieved. It is not limited to the shaking table control device.
For example, application to a control device of an active vibration isolation table using a voice coil motor as an actuator also falls within the scope of the present invention.

[0065]

As described above, according to the control apparatus of the vibration isolating table with the position signal restoring circuit of the present invention, for example, one position sensor in four air spring type vibration isolating legs is eliminated for cost reduction. Even if it is, it is possible to realize an operation as if the control is applied based on the measurement output of the actual position sensor,
This has the effect. Conventionally, the control of the air-spring-type support leg from which the position sensor has been removed is performed by extracting a compensation signal from the feedback device of the adjacent air-spring-type support leg and generating a driving force using the signal. The adjustment work for stabilizing the support of the vibration isolation table 8 by the four vibration isolation legs is complicated and requires skill. However, according to the control device according to the first embodiment of the present invention as shown in FIG. 1 or FIG. 5, there is an effect that the burden of the adjustment work is reduced.

Further, when some disturbance acts on the vibration isolation table 8 and tilts with respect to the vertical axis, according to the present invention, as described in the section of the prior art, this motion mode can be suppressed well. effective.

Further, in the control apparatus for the vibration isolation table according to the second aspect of the present invention, the motion mode of the rigid body is calculated using the output of the position sensor installed at each point of the vibration isolation table. This is a device configuration in which compensation is applied and finally the compensation output is distributed to actuators installed at each point of the vibration isolation table, and there is an effect that the attitude change of the vibration isolation table can be quickly controlled. In the conventional vibration damping device, many local points of the vibration isolation table are controlled, but they are not aware of the spatial motion. On the other hand, in the vibration damping device for a vibration damping table of the present invention, it can be said that the motion of the vibration damping table as a rigid object is macroscopically controlled.

In addition, not only the exposure XY stage but also various other devices are mounted on the vibration isolation table. Therefore, the anti-vibration table, which has an eccentricity and has an asymmetric load with respect to the installation of the support legs, is statically and stably supported, and then removes the vibration transmitted from the floor and It must exert the function of damping the dynamic vibration generated by the device. In the conventional vibration damping device that provides feedback for each support leg, it is very complicated to adjust the static balance of the anti-vibration table, which is eccentric and asymmetric. This is because the adjustment of one support leg interferes with the other, for example, prompting the readjustment of another support leg. However, in the vibration damping device of the air spring type vibration damping table of the present invention, the structure is such that the motion mode of the vibration damping table is controlled, and the mutual interference is originally embedded in the feedback device. is there. Therefore, the adjustment is performed not on each support leg but on the exercise mode, and dynamic adjustment as well as static adjustment becomes extremely simple.
This has the effect. Thus, the start-up of the device is shortened, and the operation of the expensive device is facilitated.

In addition to a passive vibration damping device, a control device of an air spring type vibration damping table provided with a feedback device, not to mention a vibration damping performance against vibration from the floor, and a device mounted with a vibration damping table. Although there is a trade-off between the vibration suppression performances of the vibrations that occur, the present invention has an effect that the vibration suppression performance can be satisfied without deteriorating the vibration isolation performance.

Further, according to the control apparatus of the vibration isolating table with the decoupling circuit of the present invention, even if one position sensor among the four air spring type vibration isolating legs is removed for cost reduction, three position sensors are removed. Three types of motion modes are extracted from the sensor output, individually compensated for them, and finally four types are obtained from the three types of compensation signals.
Since a drive command is given to the actuator at the location, there is an effect that the cost can be reduced and the vibration damping performance can be improved as compared with the conventional case.

Further, in the conventional apparatus, as described above, the adjustment work for stabilizing the support of the vibration isolating table 8 by the four air spring type vibration isolating legs is complicated and requires skill, and the position sensor is completely equipped. However, since the feedback devices 15a to 15d of the supporting legs are independent of each other, the parameter adjustment of the feedback device for one leg has a great influence on the stabilization of the other air-spring type supporting legs, and therefore, in this case, Adjustment work was also complicated and required skill. However, according to the control device of the present invention shown in FIG. 14 and FIG. 15, since the stabilization can be achieved for each exercise mode, there is an effect that the burden of the adjustment work is reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a control device of an air spring type anti-vibration table with a position signal restoration circuit according to one embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific example of a position signal restoration circuit.

FIG. 3 is a diagram showing coordinates of four air spring type support legs as viewed from above.

FIG. 4 is a waveform diagram of a position deviation signal at the time of startup.

FIG. 5 is a configuration diagram of a control device of an air spring type anti-vibration table with a position error signal restoration circuit according to another embodiment of the present invention.

FIG. 6 is a configuration diagram of a vibration damping device of the air spring type vibration damping table of the present invention.

FIG. 7 is a response waveform diagram of the mode extraction circuit when a step-like rotational motion is excited.

FIG. 8 is a response waveform diagram of the mode extraction circuit when a step-like translational motion is excited.

FIG. 9 is a servo block diagram of a support leg.

FIG. 10 shows a difference in response waveform depending on the presence or absence of a voltage to an auxiliary input terminal.

FIG. 11 is a configuration diagram of a control device of a conventional air spring type vibration isolation table.

FIG. 12 is a configuration of a support leg constituting an air spring type vibration isolation table.

FIG. 13 is a configuration diagram of a control device of a conventional air spring type vibration isolation table.

FIG. 14 is a configuration diagram of a decoupling control device for an air spring type anti-vibration table according to a third embodiment of the present invention.

FIG. 15 is a configuration diagram of a decoupling control device of an air spring type anti-vibration table according to a fourth embodiment of the present invention.

FIG. 16 is a diagram showing coordinates of four air-spring support legs as viewed from above.

FIG. 17 is a circuit diagram of a motion mode extraction circuit in the device of FIG.

18 is a circuit diagram of a motion mode distribution circuit in the device of FIG.

19 is a graph showing how the motion mode deviation signal converges when a step-like rotational disturbance is applied around the y-axis in the apparatus shown in FIG.

[Explanation of symbols]

1, 1a, 1b, 1c, 1d: servo valve, 2, 2
a, 2b, 2c, 2d: air spring, 3, 3a, 3b, 3
c, 3d: position sensor, 4, 4a, 4b, 4c, 4d:
Support, 5, 5a, 5b, 5c, 5d: acceleration sensor,
6, 6a, 6b, 6c, 6d: mechanical spring for preload, 7, 7
a, 7b, 7c, 7d: viscous element, 8: anti-vibration table, 9, 9
a, 9b, 9c, 9d: low-pass filter, 10, 10
a, 10b, 10c, 10d: voltage-current converter, 11,
11a, 11b, 11c: displacement amplifier, 12, 12a,
12b, 12c, 12d: comparison circuit, 13, 13a, 1
3b, 13c, 13d: target voltage, 14, 14a, 14
b, 14c, 14d: PI compensator, 15, 15a, 15
b, 15c: feedback device, 15d: pseudo feedback device, 16: position signal restoration circuit, 16 ': position deviation signal restoration circuit, 17: feedback device with position signal restoration circuit, 17': feedback device with position deviation signal restoration circuit , 21, 21a, 21b, 21c, 21
d: support leg, 22: mode extraction circuit, 23: distribution circuit,
24a, 24b: _{actuator, e, e a, e b} , e
_{c, e d:} deviation signal, T: translational deviation signal, R: rotary deviation _signal, c T, _{c R:} compensation signal, 26: motion mode extracting circuit, 27: motion mode distributing circuit, 27 ': 3 Input 3 Output Motion mode distribution circuit, 18: position signal restoration circuit, 1
9: Signal line.

Claims (9)

(57) [Claims] 1. A control device for positioning a plate-shaped anti-vibration table supported at four positions by first to fourth four support legs at a vertical target position without a steady deviation, First to third position sensors provided corresponding to first to third support legs, respectively, for detecting vertical positions of the anti-vibration table at positions supported by the respective support legs; First to fourth acceleration sensors which are provided corresponding to the first to fourth support legs, respectively, and detect vertical accelerations of the vibration isolating table at positions supported by the respective support legs, and corresponding position sensors. And first to third feedback devices that independently control the height of the vibration-isolation table support position of the first to third support legs based on the output of the acceleration sensor and the first to third position sensors. Output, or compare these outputs with the vertical target position signal. Calculating means for calculating a vertical position or a positional deviation of the vibration isolation table at a position supported by the fourth support leg based on the first to third positional deviation outputs; And a fourth feedback device that servo-controls the height of the vibration-isolation table support position of the fourth support leg based on the output of the acceleration sensor of (4). 2. An output of a position sensor corresponding to each of the first to third support legs, wherein the first to fourth support legs are arranged counterclockwise at four corners of the vibration isolation table. When the position signals are sequentially represented as z _a , z _b , and z _c ,
The position signal z _d corresponding to the fourth support leg is calculated by the formula z _d
2. The control device for a vibration isolation table according to claim 1, wherein the calculation is performed by: = z _a −z _b + z _c . 3. A flat anti-vibration table horizontally supported by at least two support legs arranged at positions spatially separated from each other in order to position the target at a vertical target position without a steady deviation. A position sensor that is provided correspondingly and detects a vertical position of the anti-vibration table at a position supported by each support leg; and a support sensor that is provided corresponding to each support leg and that supports the anti-vibration table. An acceleration sensor for detecting the vertical acceleration at the support portion by the support leg, and a servo mechanism provided negatively to the output of the acceleration sensor to the preceding stage of the voltage-current converter for driving the support leg. A feedback device for stabilizing and comparing the output of the position sensor with a target value to obtain a deviation signal, passing the deviation signal through a compensator, and then guiding the deviation signal to the voltage-current converter. Target value corresponding to A mode extraction circuit for calculating a translation error signal and a rotation error signal of the vibration isolation table based on at least two error signals which are comparison outputs of the position sensor; and the compensator compensates for the translation error signal and the rotation error signal. And a distributing circuit for redistributing the compensator output to each voltage-current converter in the feedback device as a supporting leg drive signal. 4. The apparatus according to claim 1, wherein the translation error signal and the rotation error signal are at xy coordinates defined in a horizontal plane of the vibration isolation table.
4. The control apparatus according to claim 3, wherein the calculation is performed in one of the x and y directions or in both the xy directions. 5. A drive signal for a device mounted on the vibration isolation table is guided through a pseudo-differential circuit having an appropriate time constant to an auxiliary input terminal provided in a preceding stage of the voltage-current converter to drive the device. 4. The control device for a vibration isolation table according to claim 3, wherein the vibrations applied to the vibration isolation table are suppressed. 6. A control device for positioning a plate-shaped anti-vibration table supported at four positions by first to fourth four support legs at a vertical target position without a steady-state deviation, wherein: First to third position sensors provided corresponding to first to third support legs, respectively, for detecting vertical positions of the anti-vibration table at positions supported by the respective support legs; First to fourth acceleration sensors that are provided corresponding to the first to fourth support legs and detect vertical acceleration of the anti-vibration table at the portions supported by the respective support legs; Based on the output of the third position sensor or the first to third position deviation outputs obtained by comparing these outputs with the vertical target position signal, the vertical translational movement to be taken by the vibration isolation table and the different Outputs first to third motion mode deviation signals corresponding to rotational motion about an axis A motion mode extracting circuit, a PI compensator that performs PI compensation on the first to third motion mode deviation signals, and a first to a fourth support leg based on an output of the PI compensator. A motion mode distribution circuit that outputs first to fourth displacement signals corresponding to displacement amounts to be taken; a detection signal negatively fed back from the first to fourth displacement signals and the first to fourth acceleration sensors Based on the first to fourth
Means for outputting a drive signal for driving the support leg of the vibration isolation table. 7. A control device for positioning a plate-shaped anti-vibration table supported at four positions by first to fourth four support legs at a vertical target position without a steady-state deviation, wherein: First to third position sensors provided corresponding to first to third support legs, respectively, for detecting vertical positions of the anti-vibration table at positions supported by the respective support legs; First to fourth acceleration sensors that are provided corresponding to the first to fourth support legs and detect vertical acceleration of the anti-vibration table at the portions supported by the respective support legs; Based on the output of the third position sensor or the first to third position deviation outputs obtained by comparing these outputs with the vertical target position signal, the vertical translational movement to be taken by the vibration isolation table and the different Outputs first to third motion mode deviation signals corresponding to rotational motion about an axis A motion mode extracting circuit, a PI compensator for performing PI compensation on the first to third motion mode deviation signals, and a first to a third support leg based on an output of the PI compensator. A motion mode distribution circuit that outputs first to third displacement signals corresponding to displacement amounts to be taken; and a fourth support leg of the vibration isolation table based on an output of the first to third position sensors. A position signal restoring circuit for outputting a position signal corresponding to a position in the vertical direction at the supporting portion, and an output of the position signal restoring circuit, or a fourth position deviation obtained by comparing this output with a vertical target position signal A PI compensator that performs PI compensation on the output and outputs a fourth displacement signal; and a first compensator and a detection signal that are negatively fed back from the first to fourth acceleration sensors. Based on the first to fourth
Means for outputting a drive signal for driving the support leg of the vibration isolation table. 8. The control device for an anti-vibration table according to claim 1, wherein said support leg is of an air spring type. 9. The control apparatus for a vibration isolation table according to claim 1, wherein said support leg uses a voice coil motor as an actuator.