JP2001090774A - Active vibration resistant device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve quick responsiveness by restraining overshoot. SOLUTION: An active vibration resistant device is provided with an air spring type support leg 5 for supporting a vibration resistant stand 1, a filter 6 for performing filtering by converting output of a vibration sensor 4 into an electric signal and a voltage-current converter 7 for driving a servo valve 41 on the basis of a signal by adding output of a compensator 46 and output of the filter 6, and is provided with a threshold value setting means 48 for designating this side position of a target position decided by a target voltage setting means 10 for designating the target position and a hysteresis comparator 47 for inputting an output signal of a displacement amplifier 8 for converting output of the threshold value setting means and a position sensor 3 into an electric signal, and the compensator 46 for compensating for an output signal of a comparing circuit 9 for comparing the output of the displacement amplifier 8 with output of the target voltage setting means 10 is formed as a variable compensator to be switched to a compensator P and a compensator PI in response to output of the hysteresis comparator 47.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active vibration isolator for suppressing propagation of floor vibration to a vibration isolation table. The present invention
In particular, it is an active vibration isolator suitably used as a constituent unit of a semiconductor exposure apparatus equipped with an exposure XY stage, and is suitably used for an air spring type active vibration isolator using an air spring actuator. Applied.

[0002]

2. Description of the Related Art A group of devices that dislike vibration are mounted on a vibration isolation table. For example, there are an optical microscope and an XY stage for exposure. In particular, in the case of an XY stage for exposure in a step-and-repeat type semiconductor exposure apparatus, the stage must be mounted on an anti-vibration table in which vibration transmitted from the outside is eliminated as much as possible in order to perform appropriate and rapid exposure.
This is because exposure must be performed with the XY stage for exposure completely stopped. In addition, it must be noted that the exposure XY stage has an intermittent motion of step and repeat as an operation mode, and generates a repetitive step vibration, which causes the vibration of the vibration isolation table. It is impossible to start the exposure operation even when such vibrations remain without being settled. Therefore, the vibration isolation table is required to achieve a good balance between vibration isolation for external vibration and vibration suppression performance for forced vibration caused by the motion of the mounted device itself.

In recent years, instead of a step-and-repeat type semiconductor exposure apparatus in which the XY stage is completely stopped and then the silicon wafer mounted on the stage is irradiated with exposure light, the exposure light is scanned while scanning the XY stage. A scan type semiconductor exposure apparatus that irradiates a silicon wafer with light has also appeared. Similarly, it is required that a vibration isolation table used in such an apparatus be well-balanced in terms of vibration isolation of external vibrations and vibration suppression performance against forced vibrations caused by the movement of mounted equipment.

[0004] As is well known, anti-vibration tables are classified into a passive type and an active type. In recent years, there has been a tendency to use active vibration isolators in order to meet the demands for high-precision positioning, high-accuracy scanning, high-speed movement, etc., required for devices mounted on the vibration isolation table. An air spring, a VCM (voice coil motor), a piezoelectric element, and the like are known as actuators used for the actuator. Here, first,
A specific description will be given of an active vibration isolator using an air spring as an actuator.

FIG. 21 shows a configuration of a conventional active vibration isolator using an air spring as an actuator. In the figure,
1 is a vibration isolation table on which precision equipment such as an XY stage is mounted, 2
a to d are air spring actuators including an air spring and a servo valve (not shown) for supplying and discharging air of a working fluid;
Reference numerals 3a to 3d denote position detecting means for measuring displacement in the vertical direction.
Reference numerals a to d denote vibration detecting means for detecting vertical vibration. As the position detecting means 3a to 3d, an eddy current displacement sensor, a capacitance sensor, a position detecting sensor using a photoelectric conversion element or the like can be used, and as the vibration detecting means 4a to 4d, an acceleration sensor or a geophone sensor can be used. . At the four corners of the anti-vibration table 1, the air spring actuators 2 a to d, the position detecting means 3 a to d, the vibration detecting means 4 a to d, and the like are incorporated as main constituent elements.
d is arranged to support the vibration isolation table 1 and the devices mounted thereon. The main components for supporting the vibration isolation table 1 in the horizontal direction are not shown, but are the same as those in the vertical direction described above.

Next, for the air spring type support legs 5a to 5d,
The configuration and operation of the feedback device will be described. Ma
Output of the vibration detecting means 4a to 4d such as an acceleration sensor
Is a gain compensator 6a having an appropriate amplification degree and a time constant.
Servo bar included in the air spring actuator through
Of voltage-current converters 7a to 7d for valve opening and closing
Negative feedback is provided to the previous stage. This acceleration feedback loop
Damping to stabilize the mechanism
I have. Further, the outputs of the position detection means 3a to 3d are displacement amplification
Input to the comparators 9a to 9d through the comparators 8a to 8d.
You. Here, the target voltage input terminals 10a to 10d are set.
A comparison with the voltage is performed to obtain the position deviation signal (e _a , E_b ,
e_c , E_d ). Target voltage input terminals 10a to 10d
Is set on the installation surface of the air spring type support legs 5a to 5d.
Is equivalent to the equilibrium position of the anti-vibration table 1 based on.
Subsequently, the position deviation signal passes through PI compensators 11a to 11d,
This signal and the negative feedback signal of the acceleration feedback loop
The voltage-current converters 7a to 7d are driven by drive signals obtained by adding
Live. Then, the servo valve opens and closes due to opening and closing.
The internal pressure of the air spring is adjusted and the anti-vibration table 1 is connected to the target voltage input terminal.
Can be held at the desired position set in 10a-d without steady-state deviation
Wear. Here, P of the PI compensator is proportional, and I is the integral operation.
Respectively. With air spring actuator
The air spring type support legs 5a to 5d are used for vibration isolation for mounting a heavy object.
Able to support the table.

FIG. 22 shows the structure of the XY stage 12 mounted on the vibration isolation table 1 and performing intense acceleration / deceleration operation. In the figure, 13 is an X stage, 14 is a fine movement stage for finely positioning a silicon wafer 15 mounted on the X stage 13, 16 is a Y stage, and 17YR and 1
7YL is a mover of a linear motor that drives the Y stage 16 (the mover of the X stage 13 is not shown);
Is a coil which is a stator of a linear motor for driving the X stage 13, 19YR and 19YL are coils which are stators of a linear motor arranged on the left and right to drive the Y stage 16, 20 is a stage base, and 21X is X A vermirer for axis measurement, 21Y is a vermira for Y axis measurement.

The air spring type active vibration isolator is characterized by poor response and high load bearing capacity. On the other hand, an active vibration isolator using an electromagnetic actuator typified by a voice coil motor has a quick response but does not have a high supporting load capability. The experimental fact of FIG. 23 is observed based on the features of the air spring type active vibration isolator described above.
FIG. 2A is an example of a position deviation signal of the air spring type active vibration isolator when the XY stage 12 mounted on the vibration isolator is driven in a step-and-repeat manner. This is a position deviation signal in which a sharp swing as a transient phenomenon caused by the step driving of the XY stage is superimposed with a large low-frequency undulation caused by repeating the step driving and reversing its polarity. Such behavior can be confirmed by numerical experiments using an appropriate mathematical model. FIG.
An example of a numerical experiment is shown in (C), and it can be seen that the same tendency as the measured result can be simulated.

Here, the behavior of the position deviation signal is qualitatively interpreted. First, transient phenomena occur at the natural period of the air spring type active vibration isolator by step driving using a pulse-like waveform (hereinafter, referred to as a “bang-bang waveform”) when the XY stage 12 is rapidly accelerated and decelerated at a substantially constant period. Is caused. The convergence of the transient phenomenon to zero takes time, but the next step drive is performed before the position error signal has not completely converged to zero, and the transient phenomenon occurs again. As a result, the convergence becomes insufficient, and step-driving is performed one after another, so that position deviations that cannot be converged accumulate, resulting in a shift of the position deviation signal. It should be noted that the shift of the position deviation signal is caused not only by the above-mentioned poor convergence but also by the moving load of the movable portion of the XY stage 12 moving by step and repeat.

The shift of the position deviation signal means that the main unit including the vibration isolation table deviates from the equilibrium position specified by the target voltage. For example, when the position deviation signal shown in FIG. 23 is a position deviation signal in the X direction, it means that the main unit including the vibration isolation table has gradually moved in the X direction from the initial equilibrium position. . If the position deviation signal is a rotation about the x-axis, it means that the main unit including the vibration isolation table is gradually tilted around the x-axis from the initial equilibrium position.

In order to suppress such a phenomenon, there is disclosed a technique of appropriately compensating a drive signal of an XY stage and feeding it forward to an actuator of an active vibration isolator. For example, Japanese Patent Application Laid-Open No. Hei 6-216003, “Stage device” is mentioned. However, the response of the air spring type active vibration isolator is slow, and the feedforward operation causes the response shown in FIG.
The swing of the position deviation signal as in (A) cannot be suppressed. In the case of an active vibration isolator using an electromagnetic actuator such as a voice coil motor, although it has the ability to suppress transient phenomena of the vibration elimination table caused by the step driving of the XY stage, it corrects the shift of the vibration isolation table. Does not have the ability to return to the equilibrium position.

[0012]

Problems to be solved by the air spring type active vibration isolator are summarized as follows. FIG.
Reference numeral 4 denotes a configuration of another conventional air spring type vibration damping device using an air spring as an actuator. In the figure, 2 is an air spring, 3 is a position sensor for measuring the displacement of the vibration isolation table 1, 4 is a vibration sensor for detecting vibration of the vibration isolation table 1, and 41 is air for supplying working air to the air spring 2. And an exhaust servo valve, 42 is a preload means, 43 is an air spring 2 and a preload means 42
And a viscosity element expressing the viscosity of the entire mechanism (not shown). The mechanism combined from these components is called the pneumatic spring support leg 5. The position sensor 3 may be an eddy current displacement sensor, a capacitance sensor, a position detection sensor using a photoelectric conversion element, or the like, and the vibration sensor 4 may be an acceleration sensor or a geophone sensor.

Next, the structure and operation of the feedback device 50 for the air spring type support leg 5 will be described. First,
The output of the vibration sensor 4 typified by an acceleration sensor is negatively fed back to a stage preceding the voltage-current converter 7 for opening and closing the servo valve 41 via a filter 6 having an appropriate amplification factor and a time constant. The mechanism is stabilized by the acceleration feedback loop. That is, damping is provided. Further, the output of the position sensor 3 is input to the comparison circuit 9 through the displacement amplifier 8. Here, the output voltage (equilibrium position target voltage) r _{0 of the} target voltage setting means 10 equivalent to the target position with respect to the installation surface of the air spring type support leg 5 is provided.
And a deviation signal e is obtained. This deviation signal e is PI
The voltage-current converter 7 is driven through the compensator 11.
Then, the air spring 2 is opened and closed by opening and closing the servo valve 41.
The pressure in the chamber is adjusted, and the vibration isolation table 1 is set to the target voltage setting means 10.
Can be held at the desired position set in the above step without a steady-state deviation. Here, P means proportional and I means integral operation.

An air spring type support leg 5 using the air spring 2 as an actuator has a capability of mounting a heavy object on the vibration isolation table 1. However, a high-speed response cannot be expected for an air spring type anti-vibration device including the air spring type support leg 5 and the feedback device 50. However, PI
By using a P compensator instead of the compensator 11,
It is known that high-speed response can be achieved. FIG.
Is an experimental result showing the rising characteristics of the vibration isolation table due to the difference between the P compensator and the PI compensator, that is, the time response until the installed vibration isolation table converges to the target position. The PI compensator converges after a large overshoot occurs, whereas the P compensator converges without overshoot. FIG. 26 shows an experimental result of the target value step response caused by the difference between the PI compensator and the P compensator. FIG.
In the case of the PI compensator, an oscillating response waveform is generated and then converges, but in the case of the P compensator, overshoot and undershoot do not occur. As described above, by using the P compensator instead of the PI compensator, the convergence of the response is improved. However, when the P compensator is used and the positioning target position of the vibration isolation table is changed, or when a disturbance is input,
There is a problem that a small steady-state deviation occurs.
Of course, when a PI compensator is used, no steady-state error occurs.

The above experimental results will be described based on the control block of the vibration isolation table. A control block diagram of the vibration isolation table expressed with one degree of freedom can be expressed as shown in FIG. Using the symbols shown, the transfer function within the broken line including the vibration isolation table and the acceleration feedback loop applied thereto is as follows.

[0016]

(Equation 1)However, the meaning of the symbol in FIG. 27 and the above equation is x:
Displacement of vibration isolation table [m], v _d : Input voltage of the voltage-current converter 7
Pressure [V], r₀ : Target voltage [V], r_s : Position detection voltage
[V], M: mass [kg], C: viscous friction coefficient [N · s]
ec / m], K: spring constant [N / m], k_air : Voltage
From the input of the flow converter 7 to the driving force generated by the air spring 2
Integral gain [(N / V) · sec], k_a : Acceleration
Conversion gain from the sensor 4 to the input of the voltage-current converter 7
[V · sec^Two / M], k_s : Conversion gain for position detection
[V / m], k_p : Gain [V / V] of PI compensator,
T: Time constant [sec] of PI compensator, s: Laplace operation
I am a child.

[0017] from equation (1), it can be seen that the damping is can be granted by k _a. Transfer characteristic from the input of the voltage-current converter 7 for driving the servo valve to the driving force of the air spring is expressed as k _air / s in the figure, the damping is made imparted by acceleration feedback conversion gain k _a This is to utilize this integral characteristic. Also,
From the equation (1), the transfer function of the controlled object including the acceleration feedback still includes an integrator, and according to the teaching of the control theory, it is a type 1 system, so the gain element (P compensator) Even if a closed loop system is constructed with
It can be maintained at the target value without a steady-state deviation. Furthermore, even if a disturbance is input, the position deviation should be able to converge to zero. Actually, the position can be adjusted so as to converge on the target value without a steady-state deviation by the position control system using the P compensator. However, as described above, when the target value is changed or a disturbance is applied, a steady-state deviation actually occurs. This is shown in FIG.
7 due to the deviation from the ideal integral characteristic expressed as k _air / s. The characteristic from the drive input to the servo valve to the force generated by the air spring has a deviation from the integral characteristic in an extremely low frequency range, and generally has a flat gain characteristic.

The problems of the above conventional example are summarized as follows. Conventionally, a PI compensator has been used in a conventional feedback device of an air spring type vibration damping device using an air spring as an actuator. According to the control theory, since the closed loop is of the form 1, it can be held without a steady-state error with respect to the target value input, and the steady-state error can be made to converge to zero even if a disturbance is input. But,
There is a problem that the response is slow and overshoot occurs.

It is a first object of the present invention to provide an air spring type vibration isolator which suppresses these overshoots and improves responsiveness.

As is well known, the air spring type support leg 5 using an air spring as an actuator is capable of supporting a vibration isolation table on which a heavy object is mounted. However, in the case of the active vibration isolator, there is a problem that the characteristic of the closed loop system formed by turning on the feedback device 50 solely determines the vibration isolation / damping performance. Therefore, in order to surpass the anti-vibration / damping performance determined by the closed loop, a feed forward signal is actively injected into the closed loop system. Known materials include, for example, Japanese Patent Laid-Open No. 6-2160.
03 “Stage device”. However, no significant improvement could be expected even if a feedforward signal was injected into the active vibration isolator comprising the air spring type support leg 5 and the feedback device 50. The reason is that it originally has a low response ability.

An active vibration isolator using an air spring as an actuator has a very slow response to both disturbance and target input. As already mentioned, the active vibration damping device has a vibration damping ability to suppress the influence of the operation of the onboard equipment,
There is a need for a balanced implementation of the vibration isolation capability that blocks vibrations transmitted from outside. In particular, there has been a demand for an improvement in vibration suppression performance that suppresses the influence of step-and-repeat driving of precision equipment mounted on a vibration isolation table, for example, an XY stage.

Conventionally, a technique has been disclosed in which a signal of the vibration isolating table is fed forward to a closed loop system in order to suppress shaking and a change in posture of the vibration isolation table due to acceleration / deceleration operation of precision equipment. However, simply feeding forward the signals of the on-board equipment that performs the acceleration / deceleration operation could not quickly suppress the influence of disturbance. A second object of the present invention is to correct a posture change around an equilibrium position of a vibration isolation table.

Referring to FIG. 28, the structure and operation of another conventional active vibration isolator using an air spring as an actuator will be described. In the figure, reference numeral 41 denotes a servo valve for supplying and exhausting air of a working fluid to and from the air spring 2, and reference numeral 3 denotes a vibration isolator 1
Is a position sensor for measuring the displacement of the preload means, 42 is a preload means, and 43 is a viscous element expressing the viscosity of the air spring 2, the preload means 42 and the entire mechanism (not shown). The mechanism combined from these components is called the pneumatic spring support leg 5.

Next, the structure and operation of the feedback device 50 for the air spring type support leg 5 will be described. First,
The output of the vibration sensor 4 such as an acceleration sensor is negatively fed back to the front stage of the power amplifier 7 for opening and closing the servo valve 41 via the filter 6 having an appropriate amplification factor and time constant. The mechanism is stabilized by the acceleration feedback loop. That is, damping is provided. Further, the output of the position sensor 3 is input to the comparison circuit 9 through the displacement amplifier 8. Here, a target voltage r ₀ equivalent to a target position with respect to the installation surface of the air spring type support leg 5 is shown.
Is compared with the output voltage of the target voltage setting means 10 to generate a deviation signal e. This deviation signal e is output to the PI compensator 11
To drive the power amplifier 7. Then, the pressure in the air spring 2 is adjusted by opening and closing the servo valve 41, so that the vibration isolation table 1 can be maintained at a desired position set by the target voltage setting means 10 without a steady deviation. Where P is proportional and I is
Means integration operation, respectively. The air spring type supporting leg 5 using the air spring 2 as an actuator has a capability of mounting a heavy object on the vibration isolation table 1.

FIG. 29 shows a more detailed structure of the air spring type support leg 5. In the figure, 2V and 2H are air springs, 3
V and 3H are position sensors, 4V and 4H are acceleration sensors,
1V and 41H are servo valves, and V and H attached to the end of the numbers mean a vertical direction and a horizontal direction, respectively. The problem in the active vibration isolator will be described with reference to FIG. First, generation of local vibration of a mechanism member or the like existing in the support leg can be cited. In addition, a problem that a space occupied by the mechanism member in the support leg is large can be pointed out. The former problem hinders the improvement of the characteristics of the vibration isolation table. This is because, if local vibrations irrelevant to the displacement or acceleration of the support structure are present at the detection site, those vibrations are also taken into the feedback loop, causing so-called spillover. The latter problem may hinder the incorporation of an actuator having physical dimensions absolutely necessary for vibration isolation and vibration suppression. In the case where an incapable actuator must be incorporated in order to comply with the physical shape and dimensional constraints imposed on the support leg, for example, this is an air spring and the equipment mounted on the support leg is subject to acceleration / deceleration movement. When a vibration suppression operation for suppressing the reaction force is required, the actuator is saturated. As a result, not only the damping characteristics but also the anti-vibration performance are deteriorated. FIG. 30 shows a position sensor 3V.
An example of mounting is shown. A target 71 of an eddy current type position sensor 3V is attached to the casing 70, and the position sensor 3V itself is also attached to an attachment jig 72 provided on a member on the support leg installation side. Therefore, it is understood that the local vibration of each mounting jig is easily generated, and the physical space occupied by the detection system becomes large.

The problems of the supporting legs in such an active vibration isolator are as follows. In order to perform active vibration isolation and vibration suppression, the support leg is provided with a position sensor and an acceleration sensor together with the actuator. These sensors are mounted using a mounting jig so as to perform a predetermined function and be mechanically adjustable. However, there is a problem that the vibration of the mounting jig itself irrespective of the movement of the structure on the supporting leg is easily induced. This local vibration becomes an output signal of each sensor and is taken into the feedback loop, so that the control system spills over. That is, an adjustment limit of the vibration isolation and vibration suppression characteristics is generated, which hinders the improvement of those characteristics. Thus, the improvement of the characteristics of, for example, a positioning mechanism mounted on the vibration isolation table has been hindered. Further, the space occupied by each sensor including the mounting jig is large, which hinders the compact design of the support legs.

A third object of the present invention is to provide an active vibration isolator in which the support leg mechanism can be designed to be compact, and the vibration and vibration damping characteristics have high adjustment limits.

[0028]

In order to achieve the first object, according to a first aspect of the present invention, a vibration isolator, an air spring supporting the vibration isolator, and a pressure of the air spring are adjusted. A servo valve, a position sensor for detecting the position of the vibration isolation table, a vibration sensor for detecting the vibration of the vibration isolation table, a preload means for applying a preload to the vibration isolation table, and a viscous element acting on the vibration isolation table. And a displacement amplifier for converting the output of the position sensor into an electric signal, a target voltage setting means for specifying a target position, and a comparison for comparing the output of the displacement amplifier with the output of the target voltage setting means. A compensator for compensating an output signal of the circuit and the comparison circuit, a filter for converting an output of the vibration sensor into an electric signal and performing appropriate filtering, and adding an output of the compensator and an output of the filter. It is provided with a feedback device consisting of a voltage-current converter for driving the servo valve based on the signal. A threshold setting unit that specifies a position before the target position determined by the target voltage setting unit; and a hysteresis comparator that receives an output signal of the displacement amplifier as input.The compensator responds to an output of the hysteresis comparator. And a variable compensator that can be switched between a P compensator and a PI compensator.

In a second aspect of the present invention, in place of the threshold value setting means, an upper limit threshold value setting means and a lower limit threshold value setting means for setting a threshold value before and after a target position determined by the target voltage setting means. In place of the hysteresis comparator, a window comparator for determining the output range of the displacement amplifier by these threshold value setting means is provided, and the variable compensator is switched by the output of the window comparator.

When a position control having a PI compensator in a feedback loop is applied to an air spring having an integral characteristic except for an extremely low frequency range, an overshoot occurs and only a slow response is obtained. Therefore, high-speed positioning by the P compensator is performed from the set position of the vibration isolation table to a position immediately before the target position, and after that, by switching to the PI compensator, overshoot is suppressed and the target position is positioned without a steady deviation. Acts as follows. In other words, it acts so that positioning can be performed with no overshoot and with a shortened positioning time. Similarly, when the current position of the anti-vibration table shifts out of the band sandwiching the target position due to disturbance, the P compensator promptly returns to the vicinity of the target position, and the current position enters the band sandwiching the target position. In this case, the operation is switched to the PI compensator, so that convergence to the target position of the vibration isolation table is performed without a steady-state error.

In order to achieve the second object, according to a third aspect of the present invention, a target value feedforward compensator is newly provided, and a feedforward signal relating to a position is activated via the target value feedforward compensator. It is injected into the feedback device in the dynamic anti-vibration device, thereby improving the positioning response.

In the preferred embodiment of the third aspect, an input terminal for a balanced position target voltage for designating a balanced position of the vibration isolation table, and a stage after the PI compensator, that is, a stage before the voltage-current converter driving the actuator. And a feedforward path is provided for each of the addition terminals provided for. A reference model that specifies a desired response is placed at the front of both feedforward paths.

More specifically, the anti-vibration table is supported by a plurality of air spring type support legs including a position sensor for measuring displacement, a vibration sensor for detecting vibration, and an air spring for providing a driving force. ing. Each pneumatic spring support leg is provided with a feedback device comprising acceleration feedback and position feedback, and injects the desired position value into the feedback device via a newly provided desired value feedforward compensator.

Here, the target value feedforward compensator includes a reference model indicating a desired response, a first feedforward path for adding an output of the reference model to an application terminal of a balanced position target voltage in the feedback device, and PI in feedback device with model output as input
A second feedforward path is provided after the compensator, that is, before the voltage-current converter that generates a driving force for the air spring. Further, the transfer functions of the first and second feedforward paths can be determined such that the target value response of the entire system is a response of the reference model K _m (s) itself. That is, the transfer function of the first feed forward path N _p (s) is 1, the transfer function of the second feed forward path D _p (s) is a denominator polynomial of the transfer function of the controlled object, including the acceleration feedback is there. It is desirable that the transfer function of the reference model K _m (s) is a third-order lag system composed of one real root and a complex root and having negative real roots equal to each other.

Responsiveness of the active vibration isolator as a closed loop
Is dull. According to this aspect, the positioning addition target voltage r_ad
Is the reference model K_m (S) and the first feedforward path
S _p (S) an equilibrium position target voltage with respect to position via
Of the reference model K_m (S) and the second file
Forward path D_p (S) through the air spring
Before the voltage-current converter that drives the actuator
Is feedforward. Addition target voltage r_adGinseng
Via the reference model and the second feedforward path
High frequency by being injected into the feedback device
Acts to compensate for the responsiveness of On the other hand, the addition target voltage
r_adVia the reference model and the first feedforward path
Of the equilibrium position target power in the conventional feedback device
By feeding forward to the pressure input terminal,
Specified r_adIt works to follow.

To achieve the third object, an active vibration isolator according to a fourth aspect of the present invention comprises a vibration isolator, preload means and a viscous element for passively supporting the same, and a vibration isolator. An actuator for applying a driving force to the table, a vibration sensor for detecting vibration of the vibration isolation table, and 2 for detecting a posture of the vibration isolation table
One-dimensional light position detecting means, a filter having an appropriate time constant for filtering the output of the vibration sensor, an electric signal converting means for converting the output of the two-dimensional light position detecting means into an electric signal, and the electric signal converting means PI that compensates for the output of
A compensator; and a power amplifier that adds the output of the filter and the PI compensator to drive the actuator.

In a preferred embodiment according to the fourth aspect, the two-dimensional light position detecting means is a pair of a light emitting element and a four-division photodiode. Alternatively, the two-dimensional light position detecting means may be a pair of a light emitting element and a PSD. In order to extract the output of the above-described two-dimensional optical position detecting means as an electric signal, the apparatus has a current-voltage conversion unit and an operation unit. In order to improve the noise resistance of the electric signal, the light emitting element is an oscillator. A multiplier driven by the driven light emitting element drive circuit and multiplying the output of the same oscillator by the electrical output of the arithmetic unit and a low-pass filter for filtering the output of the multiplier are provided. Synchronous detection is performed by the electric signal conversion means.

The two-dimensional position sensor can be functioned by detecting the change in the light spot irradiation position on the four-division photodiode light receiving surface. Each of the supporting legs in the conventional active vibration isolator has one vertical and one horizontal.
Although a position sensor and an acceleration sensor are provided, a two-dimensional position sensor constituted by a pair of a light emitting element and a four-division photodiode can be replaced with two position sensors provided in the support legs. Further, the conventional position sensor has a cylindrical shape and a large physical dimension, but the two-dimensional position sensor has a flat shape and can be mounted rigidly.

[0039]

Embodiments of the present invention will be described below. FIG.
As is clear from the actual measurement result of (A) and the numerical experiment results of FIGS. (B) and (C), when observing the position deviation signal during step-and-repeat, the transient phenomena waveform caused by the step driving and The shift caused by the continuous driving and the moving load is superimposed. In the first embodiment, a device configuration for suppressing the latter phenomenon by changing a compensator for position feedback is provided.

Embodiment 1 FIG. 1 shows a configuration of an air spring type active vibration isolator according to a first embodiment of the present invention. In the apparatus shown in FIG. 1, when a step-and-repeat drive is received, a motion mode in which an offset easily occurs is selected, and a compensator for compensating the motion mode deviation signal is changed from a conventional PI compensator to a PI ² compensator. ing. Here, it is well known that P of the PI compensator means proportional, and I means integral operation, and is generally a compensator having a transfer function of the following equation.

[0041]

(Equation 2) However, k ₁ is a proportional gain, k ₂ is the integral gain.

The compensator referred to as PI ² is a compensator having a transfer function obtained by adding one integrator to equation (1) as shown in the following equation.

[0043]

(Equation 3) According to experimental facts, the offset is superimposed on the motion mode deviation signal, especially for rotation around the X and Y axes. The reason is that during step and repeat drive, X
This is because the positioning position of the Y stage 12 moves sequentially, which predominantly acts to tilt the vibration isolation table 1.

The operation will be described below with reference to FIG.
You. First, the outputs of the position detecting means 3a to 3d are supplied to the displacement amplifier 8
are converted into electric signals by the comparators 9a to 9d.
Input. In addition to the target voltage input terminals 10a-d
Voltage and the outputs of the displacement amplifiers 8a to 8d
Deviation signal (e_a , E_b , E_c , E_d Get) Then
These positional deviation signals are used for operations such as translation and rotation of the vibration isolation table 1.
Motion mode deviation signal (S_z , Sθ_x ,
Sθ_y ) Is led to the exercise mode extracting means 22 for extracting
You. Where S_z Represents the translational movement in the Z-axis direction, Sθ_x Is X
The rotational movement around the axis is expressed by Sθ_y Indicates rotational movement about the Y axis
This is a motion mode deviation signal. Motion mode deviation signal (S
_z , Sθ_x , Sθ_y ) Is the stabilization compensation for the position loop
Input to the device 23. More specifically, S_z Against
The PI compensator 24Z_x And Sθ_y P for
I^Two Compensators 24X and 24Y are prepared, and a compensation signal
(C_z, Cθ_x , Cθ_y ) Has been generated. Meanwhile, vibration
The electric signals output from the detecting means 4a to 4d are related to the acceleration.
Movement mode extracting means 25 for extracting a running mode signal
Led to (a_z , Aθ_x , Aθ_y ) Is output. This
Where a_z Is the translation in the Z-axis direction, aθ_x Is the rotation around the X axis
Roll over, aθ_yIs the acceleration related to the rotation around the Y axis.
These are the respective motion mode signals. (A_z , Aθ_x , Aθ
_y ) Is a gain supplement that has both gain and filtering functions.
Guided to the compensators 26Z, 26X, 26Y,
Negative feedback signal (A_z , Aθ_x , Aθ_y ). (A
_z , Aθ _x , Aθ_y ) Is the compensation signal (C_z , Cθ_x , Cθ
_y ) And the driving signal D for each motion mode_z , Dθ_x ,
Dθ_y ). (D_z , Dθ_x , Dθ_y ) Is spatial
Air spring actuator in each air spring type support leg
Motion mode for generating drive signals for the etas 2a to 2d
Input to the distribution means 27, and
The output is air spring activated via voltage-current converters 7a-d.
Are applied to the heaters 2a to 2d.

For the air spring type active vibration isolator, parameters are adjusted to satisfy both the performance of vibration isolation and vibration suppression. It simply changing compensators position feedback loop from the PI to PI ² is breaking the conventional parameter adjustment condition. This is because it is a simple act of adding one integrator to the control loop, but its influence on stability is great. That is, in the active vibration isolator of FIG. 1 having a feedback loop for each motion mode, all of the position compensators for the motion mode are PI to P.
Replacing with I ² breaks the state of parameter adjustment for vibration damping performance in the conventional device, and thus needs to be adjusted again. However, the motion mode in which an offset occurs in the position error signal in the step-and-repeat drive is X
Only in the rotational motion mode around the axis and around the Y axis,
Almost no translation occurs in the axial direction. Therefore, as in the present embodiment, the change from the PI compensator to the PI ² compensator is inserted only in the motion mode in which the offset in question occurs, and the parameter readjustment becomes small. Alternatively, since the PI ² compensator is selectively inserted, the deviation from the performance in the conventional parameter adjustment is small,
It can be done with almost no adjustment.

Numerical experiments showing the effectiveness of Example 1 are given in FIG. FIG. 3A shows a step-and-repeat drive signal, and FIG. 3B shows a position deviation signal. In (B), the dashed line indicates the response when the compensators 24X and 24Y are PI compensators, and the solid line indicates the PI when the conventional PI compensator is used.
The response when ^two compensators are used is shown. After five successive bang-bang waveforms of step driving, five steps of inverted step driving are input. It can be seen that in the latter driving, that is, as the step-and-repeat driving progresses, the offset of the position error signal is removed and the signal approaches the bipolar signal. Therefore,
If this is a position deviation signal in the rotational motion mode, it can be seen that the inclination of the main unit is corrected according to the progress of the step-and-repeat drive and approaches the equilibrium position. Therefore, if this is a position deviation signal in the rotational motion mode, it indicates that the inclination of the main unit is corrected in accordance with the progress of the step-and-repeat drive, and the asymptotic position is approached.

[0047]Example 2 In the apparatus of FIG. 1, the motion mode deviation around the X axis and the Y axis
PI only for signals ^Two A compensator was used. Of course, the Z axis
PI for translation^Two Using a compensator,
Instead of PI compensator for all motion modes^Two compensation
The use of a vessel is also within the scope of the present invention. FIG.
In the position and acceleration signals are movements such as translation and rotation
The control loop is configured based on the mode.
Conventional air spring type with independent control loop for each axis
For an active anti-vibration device, PI instead of PI compensator^Two compensation
The use of a vessel is also within the scope of the present invention. Each axis Germany
FIG. 3 shows an apparatus configuration having a vertical control loop. Of FIG.
The PI compensators 11a to 11d are provided in the stabilizing compensator 23 of FIG.
And the contents are PI^Two Compensators 23a to 23d
You.

In the case where a PI ² compensator is formed by adding one integrator to the PI compensator, if necessary, phase recovery means such as phase lead compensation may be simultaneously provided in the PI ² compensator to ensure stability. Incorporation is not impeded.

Embodiment 3 Embodiment 3 focuses on the fact that the polarity of a substantially constant offset is also inverted in a cycle in which the polarity of the time series of the drive pattern is inverted, and the voltage applied to the target voltage input terminals 10a to 10d is changed. Give the operated device configuration. That is, the correction voltage for correcting the offset of the position deviation signal generated during the step-and-repeat driving is superimposed on the target voltage for positioning the vibration isolation table 1 at a desired position. For example, consider a case where the Y stage 16 performs step and repeat in the Y axis direction. Referring to FIG. 4, when the continuous step drive is performed on the near side of the drawing, the vibration isolation table 1 rotates around the X axis. The position detecting means 3a and 3b detect the approach (subsidence) of the anti-vibration table 1, and 3c and 3d detect the reverse (floating). In addition, since the amount of rotation as a low frequency component during the period in which the bang-bang step driving is continuous is substantially constant, a larger driving force is applied to the air spring actuators 2a and 2b, and conversely, the air spring actuators 2c and 2d are driven. By performing the operation of releasing the force, the offset of the position deviation signal can be canceled.

A more specific description will be given with reference to FIG. In the drawing, the description of the portions denoted by the same reference numerals as those of the other drawings described above is omitted. In FIG. 4, reference numeral 28 denotes a laser interferometer for measuring the position of the XY stage 12 in the Y-axis direction. The emitted light beam is applied to the Y-axis measuring vermirrer 21Y, and the movement amount of the Y stage 16 is measured. This signal becomes a position signal through the position detecting means 29 and is compared with the value of the position target terminal 30 to the Y stage 16 to become a position deviation signal. The position deviation signal is guided to a compensator 31 typified by a PID compensator, and the output signal drives a power amplifier 32 that supplies current to stators 19YR and 19YL of a linear motor that drives the Y stage 16 for positioning. X stage 1
The control system for No. 3 has the same configuration as the control system for the Y stage 16 described above. The step-and-repeat command to the Y stage 16 to be applied to the position target terminal 30 is supplied from the profiler 33. It should be noted that the step-and-repeat drive pattern 34 is known in advance. In the present embodiment, the known driving pattern 34
Thus, a correction voltage pattern 35 having a half cycle of a period in which the bang-bang step driving is continuous is generated. The correction voltage pattern 35 is guided to a distributor 36, and its output is added to target voltage input terminals 10a to 10d for applying voltages of target voltage setting means 37a to 37d. The distributor 36 generates a correction voltage having an appropriate amplitude and polarity for each axis.

As described above, the polarity of the offset superimposed on the position deviation signal in the air spring type active vibration isolator is uniquely determined by the driving direction of the XY stage 12 with respect to the vibration isolation table 1, and the magnitude thereof is also substantially constant. ing. Therefore, the target voltage input terminals 10a to 10d are provided only during the period in which the time series of the bang-bang step drive signal having the same polarity is input.
Then, in addition to the target voltage for positioning the anti-vibration table 1 at a desired position, a constant correction voltage sufficient for removing the offset is superimposed. In the case of the third embodiment,
The stabilizing compensator 23 does not necessarily have to be a PI ² compensator, but may be a PI compensator as in the prior art.

A numerical experiment showing the effectiveness of the third embodiment is given in FIG. In the figure, (A) shows a step-and-repeat drive signal, (B) shows a correction voltage and its application timing,
(C) shows a position deviation signal depending on the presence or absence of the correction voltage.
In (C), the one-dot chain line shows the case without the correction voltage, and the solid line shows the response when the correction voltage is superimposed on the target voltage input terminals 10a to 10d. It can be seen that the large swell of the position deviation signal is flattened by the application of the correction voltage. That is, when the position deviation signal is that of the rotational motion of the vibration isolation table 1, the vibration isolation table can always be positioned around the equilibrium posture specified by the target voltage without causing a bias in the inclination. It is.

Embodiment 4 FIG. 6 shows the configuration of an air spring type vibration damping device according to a fourth embodiment of the present invention. 24, the same elements as those in FIG. 24 are denoted by the same reference numerals, and only new elements will be described in comparison with FIG. In FIG. 6, reference numeral 46 denotes a variable compensator capable of switching from a PI compensator to a P compensator and vice versa, and 47 denotes a control signal for controlling opening and closing of an electronic switch 49 based on a voltage set by a threshold value setting means 48. This is a hysteresis comparator that generates CNT, and is a conventional feedback device 50.
The feedback device 50A is configured in combination with the above components.

First, the input / output characteristics of the variable compensator 46 will be clarified. When the electronic switch 49 controlled by the CNT is turned off using the symbols shown in the figure, the PI compensator is obtained as in the following equation.

[0055]

(Equation 4) When the electronic switch 49 controlled by the CNT is on, the P compensator is obtained as in the following equation.

[0056]

(Equation 5) Here, the opening and closing of the electronic switch 49 is controlled by the hysteresis comparator 47. The inputs to the hysteresis comparator 47 are both the output voltage of the displacement amplifier 8 and the voltage set by the threshold value setting means 48. When the output signal of the displacement amplifier 8 exists within a section from the initial power-up position to a target position determined by the threshold value setting means 48 before the final target position determined by the target voltage setting means 10, the electronic switch 49 is used. Is turned on to form a P compensator, and when the output of the displacement amplifier 8 exists in the other area, the electronic switch 49 is turned off to operate as a PI compensator.

According to the above configuration, the position control system is operated by the P compensator from the installation surface of the vibration isolation table 1 to just before the final target position, and the position control system is controlled by the PI compensator from there to the final target position. Works. In other words, the vibration isolation table is quickly started up from the installation surface of the vibration isolation table to just before the final target position, and the PI compensator operates near the target position to reduce the steady-state deviation to zero.

Numerical results showing the effectiveness of the present invention are shown in FIG.
Shown in The dashed line in the drawing indicates the response waveform when the conventional control configuration shown in FIG. 24 is used, and the solid line indicates the response waveform when the parameter setting for shortening the rise time is performed in this embodiment.
According to this embodiment, it is possible to provide a response in which the peak value of the overshoot is almost constant and only the rise time is fast. Next, the results of a second numerical experiment showing the effectiveness of the present invention are given in FIG. The dashed-dotted line in the drawing shows the response waveform when the control configuration of FIG. 24 is used, and the solid line shows the response waveform when the parameter setting for suppressing the peak value and shortening the rise time is performed in the present embodiment. According to the present embodiment, the peak amount of overshoot is suppressed as compared with the related art, and at the same time, the rise time can be shortened. The suppression of the amount of overshoot is important from the viewpoint of ensuring performance required for a structure (not shown) mounted on the vibration isolation table 1 or for avoiding mechanical collision. In this case, the maximum displacement amount is often defined, and there is an effect that the vibration isolation table can be positioned with the displacement suppressed to a value less than that.

Embodiment 5 In FIG. 6, in order to improve the rising characteristics of the vibration isolation table,
That is, the electronic switch 49 was turned on and the variable compensator 46 was operated as a P compensator in a section from the initial position of the start-up to the threshold value provided before the final target position for high-speed positioning. In other sections, the variable compensator 46 is set to PI
By operating as a compensator, convergence to the final target position was achieved without any steady-state error.

However, in order to improve the responsiveness to disturbance input, the variable compensator 46 is operated as a PI compensator when the position detection signal falls within the range between the upper limit and the lower limit with the target position in between. When the position detection signal exists in the area, the variable compensator 46 may be operated as a P compensator. The feedback is from the standpoint that importance is placed on the action of bringing the steady-state deviation to zero near the target position, and that the quick response is emphasized when other position signals are present. Therefore, the vibration isolator of the fifth embodiment is configured as shown in FIG. In the figure, 51 is an upper limit threshold value setting means, 52 is a lower limit threshold value setting means, and 53 is a window comparator. If the output of the displacement amplifier 8 is within the range determined by the threshold value setting means 51 and 52, the output of the window comparator 53 operates to turn off the electronic switch 49, and the output of the displacement amplifier 8 is out of the range. When an output is present, it operates to turn on the electronic switch 49 and a conventional feedback device 50.
The feedback device 50 </ b> B is configured together with the components described above.

For the sake of simple explanation, the air spring type support leg 5 in FIGS. 6 and 9 is illustrated about one axis in the vertical direction. However, the same device configuration is used in the horizontal direction. In addition, it goes without saying that an apparatus configuration in which a plurality of air spring type support legs 5 are arranged in the vertical and horizontal directions and a flat surface plate or the like is installed on each anti-vibration table also belongs to the scope of the present invention. . In the embodiments of FIGS. 6 and 9, the control system is realized by an analog arithmetic circuit, but a part or all of the control system may be replaced by a digital arithmetic device such as an electronic computer.

Embodiment 6 FIG. 10 shows the configuration of an active vibration isolator according to a sixth embodiment of the present invention. A feature of the conventional active vibration isolator shown in FIG. 24 is that a target value feedforward compensator is newly provided.

[0063] In FIG. 10, 66 first feed forward path connected to added to the input terminal of the equilibrium position target voltage r _o on the position, 67 is a voltage-current converter 7
The second feed forward path connected to adding the pre-stage, 68 is a reference model which receives the first and second feed both to a connected and adding the target value r _ad the forward path, the 66-68 Thus, the target value feedforward compensator 69 is configured. Here, the equilibrium position target voltage r _o is literally voltage vibration isolation base 1 designates an equilibrium position for operation, adds the target voltage r _ad positioning the anti-vibration table 1 about the equilibrium position specified by r _o Command voltage to perform the operation.

First, the principle of the present invention will be described step by step with reference to a block diagram of a closed loop for positioning the active vibration isolator. The symbols are defined in advance. In the following, M: mass of the vibration isolation table [kg], C: viscous friction coefficient [N
Sec / m], K: spring constant [N / m], k _air : conversion gain [N / m] as an integral characteristic from the input of the voltage-current converter 7 to the force generated by the air spring 2 via the servo valve. V · sec], k _a : acceleration feedback gain [V · sec ² / m], k _s : position detection gain [V / sec]
m], k _p : position gain of PI compensator [-], k _i : P
Integral gain of I compensator [1 / sec], x: Displacement of vibration isolation table [m], _ro : Equilibrium position target voltage [V], N _p
(S): transfer function of the first feed forward path _{[-], D p (s} ): transfer function of the second feed forward path _{[-], K m (s} ): reference model transfer function [-] , R _ad : addition target voltage [V], s: Laplace operator.

FIG. 11A is a control block diagram of one axis of the air spring type active vibration isolator shown in FIG. The transfer function G (s) from the input of the voltage-current converter 7 for driving the servo valve 41 to the displacement x of the vibration isolation table 1 is expressed by the following equation (6).

[0066]

(Equation 6) As described above, the physical meaning of the acceleration feedback is to provide damping to the controlled object. From a simple calculation, the transfer function G _p ′ (s) of the controlled object including the acceleration feedback, that is, the transfer function of the portion surrounded by the broken line in FIG. 11A is given by the equation (7), and FIG. 11B is obtained.

[0067]

(Equation 7) Now, the present invention injects a feed-forward signal to the input terminal and the PI compensator subsequent equilibrium position target voltage r _o. More specifically, as shown in FIG. 12, the output of the first feedforward path N _p (s) is provided at the input terminal of r _o , and the second feed forward path D _p (s) is provided downstream of the PI compensator. Are added, and N _p (s) and D _p
Both (s) are connected to the output of the reference model K _m (s) that receives the addition target voltage _rad as an input. At this time, the relationship from _rad to x can be obtained from a simple calculation as follows.

[0068]

(Equation 8) However, the transfer function of the PI compensator 11 is set to the equation (9).

[0069]

(Equation 9) At this time, D _p (s) and N _p (s) are selected as in equations (10) and (11), respectively.

[0070]

(Equation 10) Then, the transfer function from _rad to x is as follows.

[0071]

[Equation 11]

That is, it is understood that k _s is the position detection gain, and that the response from _rad can be specified by the transfer function K _m (s) of the reference model. here,
One desirable form of K _m (s) is a third-order lag system consisting of one real root and a pair of complex roots. The pole arrangement in which no overshoot occurs in the response is as shown in FIG. In the figure, the mark x indicates the position of the pole. As shown, if three negative real roots are arranged equally, no overshoot occurs. Using the symbols shown, the transfer function at this time is as shown in equation (13).

[0073]

(Equation 12) In implementing the target value feedforward compensator 69, the reference model K _m (s) 68 is divided into the first feedforward path N _p (s) 66 and the second feedforward path D _p (s) 67. To In other words, in practice the first feedforward path _{N p (s) K m (} s), to achieve the second feed forward path _{D p (s) K m (} s).

FIG. 14 shows the results of numerical experiments showing the effectiveness of this embodiment. In the figure, the dashed line does not have a target value feedforward compensator 69, the response in the case of applying the step-like target value r _o, the solid line from r _ad includes a target value feedforward compensator 69 The response when the same target value is applied is shown. From the comparison of the response curves, it can be seen that the insertion of the target value feedforward compensator 69 provides a quicker response. Moreover, no overshoot occurs in the response. This is only because the inventor has specified the reference model K _m (s) of the third-order lag characteristic in which all negative real roots are the same in order to obtain a response without overshoot.

FIG. 15 shows a step response (solid line) when the target value feedforward compensator 69 is inserted and the servo valve 41 is saturated. However, the response without the compensator (dot-dash line)
Means that the target value is the same but the servo valve 41 is not saturated. The reason why the servo valve is saturated when the target value feedforward compensator 69 is inserted is as follows (10) and (1).
As is apparent from the expression 2), the transfer function of D _p (s) · K _m (s) is due to the differentiability. From the figure, when saturation of the servo valve is caused, the reference model K _m
The response without overshoot specified in (s) cannot be realized. In fact, a large overshoot is caused. However, the input of _rad with the target value feedforward compensator 69 suppresses the amplitude of the response and improves the stabilization as compared to the case where there is no rad. That is, the effectiveness of the insertion of the target value feedforward compensator 69 according to the present embodiment is not denied.

Embodiment 7 Prior to the detailed description of this embodiment, the principle of position detection by a photodiode will be described. For the sake of simplicity, the case of a two-segment photodiode is assumed. FIG. 16 is a diagram showing the principle of detection as a position sensor using a two-part photodiode. In the figure, 73 is a two-division photodiode, A and B are light receiving areas, and 74 is a light spot. Further, in the circuit network constituted by the operational amplifiers, a portion indicated by 75 is a current-voltage converter for converting the current flowing in the light receiving areas A and B into a voltage output, and 76 is an arithmetic unit. Here, the output (A−B) of the calculation unit 76 is the amount of movement of the light spot in the y-axis direction, and the output (A + B) is the total amount of light incident on the two-division photodiode 73. In the case shown in the figure, the light spot 74 is located on the left side with respect to the two division lines, and the output (A-
B) is positive. As is apparent, the output (AB) is zero when the light spot 74 is located exactly on the dividing line, and the output (AB) is obtained when the light spot 74 is located on the right side of the dividing line.
Becomes negative. That is, it functions as a position sensor in the one-dimensional y-axis direction. 77 is a two-part photodiode 73
, And screw holes for attachment are provided at the four corners.

Next, consider a four-division photodiode.
FIG. 17 shows a principle diagram of a position sensor using the photodiode 78. The detection operation is the same as in FIG. In the case of the four-division photodiode 78, the output ｛(a
+ B)-(c + d)} is in the z-axis direction and the output {(a + d)-
(B + c)｝ detects the position of the light spot 74 in the y-axis direction. That is, it functions as a two-dimensional position sensor in the yz plane. Further, the total amount of light incident on the light receiving surface of the four-division photodiode 78 can be monitored by the output (a + b + c + d). The causes of the change in the total amount of light include (1) a decrease in power due to the life of the light emitting element, (2) entry of a foreign substance into the optical path,
(3) Relative attitude change of the light emitting and light receiving elements can be considered. Regardless of the cause, it can be used as a signal effective for self-diagnosis of the two-dimensional position sensor. From the above description, 4
It has been found that one pair of light-emitting elements (not shown) that generate the split photodiode 78 and the light spot 74 functions as a two-dimensional light position detecting means.

In this embodiment, the above-described two-dimensional light position detecting means is used for an active vibration isolator. The advantages of applying this means to an active vibration isolator can be summarized as follows. FIG.
As shown in FIG.
Has a flat shape, and can be rigidly attached to a portion requiring position detection. That is, it is possible to adopt a structure in which mechanical vibration due to insufficient mounting rigidity is unlikely to occur. As described with reference to FIGS. 28 to 30, the vibration caused by the attachment of the sensor naturally enters the feedback loop of the active vibration isolator. As a result, it is difficult to arbitrarily shape the frequency characteristics of the closed loop system within the adjustable range, and it is difficult to improve the vibration isolation / damping characteristics. However, according to the present embodiment, the two-dimensional light position detecting means having a flat shape can be rigidly mounted, so that no local vibration is generated. The output of the four-division photodiode 78 ｛(a + b) −
(C + d)} and {(a + d)-(b + c)} become zero when the light spot is located at the light receiving surface equilibrium point. Of course, the position of the light receiving surface or the light emitting element can be mechanically adjusted so that these output signals become zero at the floating equilibrium position of the vibration isolation table. At this time, the control loop has a zero-reference structure, and the target voltage setting means 10 that requires a stable constant voltage source in the conventional device becomes unnecessary. That is, the circuit configuration is simplified.

Based on the above description, FIG. 18 shows the configuration of an active vibration isolator according to the seventh embodiment of the present invention. In the figure, a flat quadrant split photodiode 78 is rigidly mounted on the surface of the support leg outer cylinder 79. A light emitting element 80 is provided on the fixed side of the support leg, and irradiates a light spot on the light receiving surface of the four-division photodiode 78. 75
And 76 are a current-voltage conversion unit and a calculation unit as described above. The arithmetic unit 76 outputs three signals, that is, a vertical displacement of the support leg outer cylinder 79, a displacement in a direction perpendicular to the paper surface, and a total amount of light incident on the light receiving surface of the four-division photodiode 78. In order to further improve the noise resistance of the electric signal, the light emitting element 80 is driven by a light emitting element driving circuit 89 driven by an oscillator 88, and a multiplier 90 for multiplying the output of the oscillator 88 by the electric output of the arithmetic unit 76; The output is provided with a low-pass filter 91 for filtering, and is synchronously detected. As a result, the current-voltage conversion unit 75, the operation unit 76, the oscillator 88, the light emitting element driving circuit 89, and the multiplier 90 constitute an electric signal conversion unit.

The output (a + b)-(c + d) is a displacement in the vertical direction. A signal whose output has passed through the multiplier 90 and the low-pass filter 91 is guided to the PI compensator 11V.
A negative feedback signal obtained by guiding an output signal of a vibration sensor (not shown) to the filter 6V and an output signal of the PI compensator 11V are added to form a drive signal, and the power amplifier 7V is excited to drive the servo valve 41V. ing. Finally, the internal pressure of the vertical air spring 2V is adjusted to control the position. Similarly, the output (a + d)-(b + c) is a displacement in the horizontal direction, and a signal obtained by passing this output through the multiplier 90 and the low-pass filter 91 is guided to the PI compensator 11H, and the output signal of the vibration sensor (not shown) is output. To the filter 6H to add a negative feedback signal and an output signal of the PI compensator 11H to form a drive signal.
1H is being driven. Finally, the horizontal air spring 2
The position is controlled by adjusting the internal pressure of H. The output (a +
b + c + d) is the total amount of light incident on the light receiving surface, and the signal passing through the multiplier 90 and the low-pass filter 89 is input to a system controller (not shown). As already mentioned,
The decrease in the total light amount occurs when an abnormal change in the posture of the support leg occurs in addition to the decrease in the light amount of the light receiving element 80 itself. Therefore, it is used as a judgment signal to stop the position control of the supporting leg by monitoring the total light amount and detecting a decrease with respect to the reference value.

Embodiment 8 The light-emitting and light-receiving elements are required to have electrical wiring that facilitates initial mechanical adjustment and maintenance. In the case of FIG. 18, the light emitting element 80 and the quadrant photodiode 78 or the PSD
The two-dimensional light position detecting means comprising a pair of the light receiving elements are arranged to face each other. However, two-dimensional position detection is also possible by bending a light beam with a mirror or the like to facilitate initial mechanical adjustment and electrical maintenance. Therefore,
An eighth embodiment of the present invention is given in FIG. In the figure, a light beam 86 emitted from a light emitting element 80 is guided to a four-division photodiode 78, which is one of the light receiving elements, by a bending mirror 87 mounted on the back surface of a support leg outer cylinder 79. When the support leg outer cylinder 79 moves by L in the vertical direction together with the supported structure 81, the bending mirror 87 also moves in the vertical direction, and the position where the light beam 86 reaches the four-division photodiode 78 is also shifted in the vertical direction. When the support leg outer cylinder 79 moves in a direction perpendicular to the plane of the paper, the reflection surface of the folding mirror 87 extends in a direction perpendicular to the plane of the paper, so that a shift in the same direction can be detected.

In addition to the four-division photodiode 78, a PSD (Positive) is used as a two-dimensional position detecting device.
On Sensitive Device) sensors are known. The operation principle will be described with a one-dimensional PSD.
FIG. 20 shows a schematic cross-sectional structure of a one-dimensional PSD. This element is composed of a high-resistance semiconductor substrate 82 and a p-layer 8 formed on the surface thereof.
3 and an n-layer 84.
The pn junction on the surface has a photoelectric effect. Referring to FIG.
It is assumed that the incident light 85 is applied to a position at a distance x from the center of the PSD. Current i flowing from the irradiation position to electrodes IL and IR
_a, i _b is in the following relationship with the L and X.

[0083]

(Equation 13) The distance X can easily be expressed as:

[0084]

[Equation 14] Accordingly, the current i _a, i _b can be calculated distance X is by performing the calculation of the above equation by measuring. The detection principle of the two-dimensional PSD is the same as that of the one-dimensional PSD. Electrodes are provided at positions orthogonal to each other in the light receiving surface, and the two-dimensional position of the plane can be detected by performing the operation of Expression (15) with each pair of electrodes. Therefore, if the four-division photodiode 78 in FIG. 18 or FIG. 19 is replaced with a PSD, it can easily function as the air spring type support leg 5. Embodiments 7 and 8 show an example in which the two-dimensional optical position detecting means is applied to the air spring support leg 5 in the active vibration isolator using an air spring as an actuator. However, it is needless to say that the actuator is not limited to the air spring, but may be an electromagnetic actuator or a piezoelectric element.

[0085]

According to the first and second aspects of the present invention, the following effects can be obtained. (1) Using the fact that the transfer characteristic from the input to the servo valve to the driving force of the air spring is almost an integral characteristic excluding the extremely low frequency range, the P vibration compensator can be used to quickly position the vibration isolation table. Can be. Since the switching from the P compensator to the PI compensator is performed in the vicinity of the target position, there is an effect that the vibration isolation table can be positioned without a steady deviation. (2) According to the configuration of the feedback device of the present invention, the amount of overshoot can be suppressed. Since the maximum displacement amount is specified for the structure (not shown) supported by the vibration isolation table, there is an effect that the vibration isolation table can be positioned with the displacement suppressed below the specified value.

According to the third aspect of the present invention, the following effects can be obtained. (1) K _m , D is simply determined without deteriorating the vibration isolation / damping performance provided by the closed loop adjustment of the active vibration isolation device.
_p, can be improved target value response simply by adding N _p. (2) In addition, the amplitude characteristic indicating the presence or absence of overshoot and the time scale indicating convergence can be arbitrarily specified by the reference model K _m (s). (3) The target value feed-forward compensator can be realized by any means of an analog electronic circuit or software, but the cost increase due to it is insignificant. Above all, the advantage that the addition of the feedforward compensator does not require any parameter readjustment as a closed loop system is superior. (4) Input r to the target value feedforward compensator
_{The ad} can be used for purposes such as correcting the tilt of the vibration isolation table generated by the step and repeat.

According to the fourth aspect of the present invention, the following effects can be obtained. (1) Conventionally, a position sensor and an acceleration sensor are provided in the vertical and horizontal directions, respectively, in a support leg of an active vibration isolator. That is, the position sensor and the acceleration sensor are each 2
Each was equipped in the support leg. According to the fourth aspect of the present invention, a two-dimensional light position detecting means can be constituted by a pair of one light emitting element and one four-division photodiode, so that the space occupied by the vertical / horizontal position sensor is reduced. This has the effect of being able to significantly reduce. (2) Further, the four-division photodiode as the light receiving element has a flat shape, and can be rigidly mounted on a portion requiring position measurement without using a mounting jig. Therefore, occurrence of local vibration can be avoided, and unnecessary signals are not introduced into the feedback loop. As a result, there is an effect that the vibration isolation and vibration damping characteristics can be easily adjusted electrically. (3) Normally, a group of precision instruments is mounted on the active anti-vibration device, and the performance that these must achieve largely depends on the anti-vibration / vibration performance of the anti-vibration table. According to the fourth aspect,
Since the performance of the anti-vibration table is improved, there is an effect that the inherent capability of the precision instrument group is not impaired. (4) Output (AB) in two-segment photodiode
Or the output 、 ４ (a + b) − (c
+ D)} and {(a + d)-(b + c)} become zero when the light spot is located at the equilibrium point of the light receiving surface. The position of the light receiving surface or the light emitting element can be adjusted so that these output signals become zero at the floating equilibrium position of the vibration isolation table. At this time, the control loop has a structure of zero reference input, and the target voltage setting means 10 in the conventional device becomes unnecessary. That is, there is an effect that the circuit configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an air spring type active vibration isolator according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing the results of a numerical experiment showing the effectiveness of the apparatus of FIG.

FIG. 3 is a configuration diagram of an air spring type active vibration isolator according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of an air spring type active vibration isolator according to a third embodiment of the present invention.

FIG. 5 is a waveform chart showing a result of a numerical experiment showing an effect of the apparatus of FIG. 4;

FIG. 6 is an air spring type vibration damping device according to a fourth embodiment of the present invention.

7 is a waveform chart showing the results of a numerical experiment showing the effectiveness of the device of FIG.

FIG. 8 is a waveform chart showing the results of numerical experiments showing the effectiveness of the device of FIG. 9;

FIG. 9 is a configuration diagram of an air spring type vibration damping device according to a fifth embodiment of the present invention.

FIG. 10 is a configuration diagram of an active vibration isolation device according to a sixth embodiment of the present invention.

FIG. 11 is a control block diagram of the active vibration isolator of FIG. 24;

12 is a control block diagram of the active vibration isolator of FIG.

FIG. 13 is a diagram showing a pole arrangement of a reference model K _m (s) in FIG. 10;

FIG. 14 is a waveform diagram comparing step responses (without saturation) with and without a target value feedforward compensator.

FIG. 15 is a waveform diagram comparing step responses (with and without saturation) depending on the presence or absence of a target feedforward compensator.

FIG. 16 is a detection principle diagram of a position sensor using a two-segment photodiode.

FIG. 17 is a detection principle diagram of a position sensor using a four-division photodiode.

FIG. 18 is a configuration diagram of an active vibration isolation device according to a seventh embodiment of the present invention.

FIG. 19 is a configuration diagram of an active vibration isolation device according to an eighth embodiment of the present invention.

FIG. 20 is a sectional view of a one-dimensional PSD.

FIG. 21 is a view showing a conventional air spring type active vibration isolator.

FIG. 22 is a diagram showing the structure of an XY stage.

FIG. 23 shows an actual measurement result and a numerical experiment showing an example of a position deviation signal during step-and-repeat driving.

FIG. 24 is a diagram showing a configuration of another conventional air spring type vibration damping device using an air spring as an actuator.

FIG. 25 is a waveform chart showing rising characteristics due to differences in compensators.

FIG. 26 is a target value step response waveform diagram due to differences in compensators.

FIG. 27 is a control block diagram of a vibration isolation table in the apparatus of FIG. 24.

FIG. 28 is a view showing a configuration of still another conventional active vibration isolator using an air spring as an actuator.

FIG. 29 is a structural view of an air spring type support leg in FIG. 28.

30 is a diagram showing attachment of a position sensor to the support leg of FIG. 29.

[Explanation of symbols]

1: anti-vibration table, 2, 2a-d, 2V, 2H: air spring actuator, 3, 3a-d: position detecting means, 4, 4a-
d: vibration detection means, 5, 5a-d: air spring type support legs,
6, 6a-d, 6V, 6H: gain compensator or filter, 7, 7a-d, 7V, 7H: voltage-current converter or power amplifier, 8, 8a-d: displacement amplifier, 9, 9a-
d: comparison circuit, 10, 10a-d: target voltage input terminal or balanced position target voltage setting means, 11, 11a-d, 1
1V, 11H: PI compensator, 12: XY stage, 1
3: X stage, 14: fine movement stage, 15: silicon wafer, 16: Y stage, 17YR, 17YL: mover of linear motor, 18X: coil as a stator of linear motor, 19YR, 19YL: stator of linear motor , 20: Stage base, 21X: Vermira for X-axis measurement, 21Y: Vermira for Y-axis measurement, 22:
Exercise mode extracting means, 23: Stabilizing compensator, 23a-
d: PI ² compensator, 24Z: PI compensator, 24X, 24
Y: PI ² compensator, 25: motion mode extracting means, 26
Z, 26X, 26Y: gain compensator, 27: motion mode distribution means, 28: laser interferometer, 29: position detection means,
30: position target terminal, 31: PID compensator, 32: power amplifier, 33: profiler, 34: drive pattern, 3
5: Correction voltage pattern, 36: Distributor, 37a-d:
Target voltage setting means, 41, 41V, 41H: Servo valve, 42: Preload means, 43: Viscous element, 46: Variable compensator, 47: Hysteresis comparator, 48: Threshold value setting means, 49: Electronic switch, 50, 50A , 50B:
Feedback device, 51: upper limit threshold value setting means, 5
2: lower limit threshold value setting means, 53: window comparator, 66: first feedforward path, 67: second feedforward path
Feed forward path, 68: reference model, 69:
Target value feed-forward compensator, 73: two-segment photodiode, A, B: two-segment photodiode light receiving area, a, b, c, d: four-segment photodiode light receiving area, 74: light spot, 75: current Voltage converter, 76:
Arithmetic operation unit, 77: holder, 78: four-division photodiode, 79: support leg outer cylinder, 80: light emitting element, 81: supported structure, 82: resistive semiconductor substrate, 83: p layer, 84: n
Layer: 85: incident light, 86: light beam, 87: bending mirror, 88: oscillator, 89: light emitting element drive circuit, 90: multiplier, 91: low-pass filter.

Claims (9)

[Claims] 1. A vibration isolation table, an air spring supporting the vibration isolation table, a servo valve for adjusting the pressure of the air spring, a position sensor for detecting a position of the vibration isolation table, and a vibration of the vibration isolation table. An air spring type support leg comprising a vibration sensor to detect and a preload means for applying a preload to the vibration isolation table and a viscous element acting on the vibration isolation table, a displacement amplifier for converting an output of the position sensor into an electric signal, A target voltage setting means for specifying a target position; a comparison circuit for comparing the output of the displacement amplifier with the output of the target voltage setting means; a compensator for compensating an output signal of the comparison circuit; A filter that converts the output of the sensor into an electric signal and performs appropriate filtering; and a voltage-current converter that drives the servo valve based on a signal obtained by adding the output of the compensator and the output of the filter. In the vibration damping device, a threshold value setting unit that specifies a position before the target position determined by the target voltage setting unit, and a hysteresis comparator that receives the threshold value setting unit and an output signal of the displacement amplifier as inputs An active vibration isolator, wherein the compensator is a variable compensator that is switched between a P compensator and a PI compensator in response to an output of the hysteresis comparator. 2. A vibration isolator, an air spring supporting the vibration isolator, a servo valve for adjusting a pressure of the air spring, a position sensor for detecting a position of the vibration isolator, and a vibration of the vibration isolator. An air spring type support leg comprising a vibration sensor to detect and a preload means for applying a preload to the vibration isolation table and a viscous element acting on the vibration isolation table, a displacement amplifier for converting an output of the position sensor into an electric signal, A target voltage setting means for specifying a target position; a comparison circuit for comparing the output of the displacement amplifier with the output of the target voltage setting means; a compensator for compensating an output signal of the comparison circuit; A filter that converts the output of the sensor into an electric signal and performs appropriate filtering; and a voltage-current converter that drives the servo valve based on a signal obtained by adding the output of the compensator and the output of the filter. An upper limit threshold value setting means and a lower limit threshold value setting means for setting a threshold value before and after a target position determined by the target voltage setting means, and an output range of the displacement amplifier by these threshold value setting means. An active vibration isolator comprising: a window compensator for determining whether or not a voltage is high, and wherein the compensator is a variable compensator that can be switched between a P compensator and a PI compensator in response to an output of the window comparator. 3. An air spring type support leg comprising a position sensor for measuring the displacement of the supported object, a vibration sensor for measuring the vibration of the supported object, and an air spring for applying a driving force to the supported object. An anti-vibration table supported by the air-spring-type support legs; a feedback device that performs acceleration feedback and position feedback for each of the air-spring-type support legs to stably position the anti-vibration table; And a target value feed-forward compensator for feed-forward inputting the signal of (i). 4. The target value feedforward compensator receives a reference model K _m (s) indicating a desired response, and receives an output of the reference model K _m (s) as an input and calculates a balance position target voltage in the feedback device. A first feed-forward path N _p (s) leading to an input terminal, a second feed-forward path D _p (s) that takes an output of the reference model as an input and adds the output to a subsequent stage of a PI compensator in the feedback device, The active vibration isolator according to claim 3, further comprising: 5. The first feed-forward path N _p
The transfer function of (s) is 1, the transfer function of the second feedforward path D _p (s) is a denominator polynomial of the transfer function of the controlled object including acceleration feedback, and the reference model K _m (s ) Is composed of one real root and a pair of complex roots, and the negative real roots are equal to each other.
The active vibration isolator according to claim 3 or 4, wherein the active vibration isolator is a second-order delay system. 6. An anti-vibration table, a preload means and a viscous element for passively supporting the anti-vibration table, an actuator for urging a driving force to the anti-vibration table, and a vibration of the anti-vibration table. A vibration sensor for detecting, a two-dimensional light position detecting means for detecting a position in the two-axis direction of the vibration isolation table, an electric signal converting means for converting an output of the two-dimensional light position detecting means into an electric signal, A filter having an appropriate time constant for filtering the output of the sensor, a PI compensator for compensating the output of the electric signal conversion means, and driving the actuator with a signal obtained by adding the output of the filter and the PI compensator. An active vibration isolator, comprising: a power amplifier. 7. The active vibration isolator according to claim 6, wherein said two-dimensional light position detecting means comprises a pair of a light emitting element and a four-division photodiode. 8. The active vibration isolator according to claim 6, wherein said two-dimensional light position detecting means comprises a pair of a light emitting element and a PSD. 9. A current-voltage conversion unit for converting a current flowing through a light receiving element of the two-dimensional light position detection unit into a voltage, and a two-dimensional position based on an output of the current-voltage conversion unit. A light emitting element driving circuit driven by an output of the oscillator to drive a light emitting element of the two-dimensional optical position detecting means; 7. The active vibration isolator according to claim 6, further comprising a multiplier for multiplying an output of the unit and an output of the oscillator.