JP2003035335A - Positive vibration-free system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a stable and speedy floating action to prevent an interference with an external equipment and the like due to disorder during floating behavior in the vibration-free system which is equipped with a pneumatic actuator and makes a pressure feedback compensation of the actuator. SOLUTION: When detecting a displacement valve of a vibration-free table which is vibration controlled and supported by the supporting mechanism and feeding back a compensation signal which compensates a difference between the detected displacement value and a target value of that of the vibration-free table from a reference position to the pneumatic actuator which applies a driving power to the vibration-free table to control the vibration-free table to be placed in the specified position, decides whether the signal of the difference between the pressure signal of the pressure detecting means to detect the pressure of the actuator and the targeted pressure value should be fed back to the actuator and switch the actuator in a suitable timing.

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 which realizes a smooth position control operation of a vibration isolation table for mounting precision equipment to a predetermined position, and a control method thereof.

[0002]

2. Description of the Related Art As precision equipment such as a semiconductor exposure apparatus is becoming more precise, higher performance of a precision vibration isolation apparatus equipped with such equipment is required. In order to perform appropriate and quick exposure in a semiconductor exposure apparatus, it is necessary to provide a vibration isolation table that eliminates external vibrations such as vibrations from the equipment installation foundation such as a floor. It is required to eliminate the adverse effects on the exposure due to the transmission of these vibrations to the exposure stage. Further, in the semiconductor exposure apparatus, the operation of the exposure XY stage such as step-and-repeat or scan is repeated during its operation. These operations excite the vibration of the vibration isolation table. Therefore, the anti-vibration table achieves a good balance of anti-vibration performance against external vibrations such as vibrations from the installation foundation such as floors and vibration control performance against vibrations generated by the operation of the equipment installed on the anti-vibration table. Required to do. Particularly, in a scan exposure apparatus, since exposure is performed in a state where the exposure stage is performing a scanning operation, it occurs due to the vibration isolation performance against external vibration and the operation of equipment such as the exposure stage mounted on the vibration isolation table. The demand for vibration damping performance against vibration is strict, and even higher-performance vibration isolator is indispensable. In response to such a demand, in recent years, the vibration of the vibration isolation table and the displacement amount with respect to the reference position are detected by a sensor, and the output signal is compensated and fed back to an actuator that applies a control force to the vibration isolation table. A vibration isolation device that actively controls the vibration and position of the vibration isolation table has been put into practical use.

[0003]

An active vibration isolation device using an air spring or the like is used in precision equipment such as a semiconductor exposure device. In these active vibration isolation devices, the vibration isolation table on which precision equipment is mounted needs to quickly shift to a normal (steady state) operation state at the start of operation. In addition, the space between the vibration isolation table and the equipment mounted on the vibration isolation table and the external equipment not mounted on the vibration isolation table is often small. Therefore, it is desired that the vibration isolation table float up to a predetermined target position along a desired path. Since many of the devices mounted on the vibration isolation table assume that the vibration isolation table floats straight up to the target position directly above, the vibration isolation table in those application examples is located directly above the landing position. It is required to levitate linearly to a predetermined target position. Further, in order to prevent interference with an external device that is not mounted on the vibration isolation table, it is necessary to keep the displacement amount during the levitation operation small. In addition, depending on the operation of the precision equipment installed on the vibration isolation table, it may be necessary to smoothly control the position of the vibration isolation table in order to deliver device parts to external equipment not mounted on the vibration isolation table. To be

An air pressure driven actuator is used for position control of the vibration isolation table, and in order to perform more precise control, pressure control for detecting and feeding back air pressure of the air pressure driven actuator is introduced. .
The introduction of pressure control suppresses pressure fluctuations during steady operation and enables highly accurate control. However, if a vibration isolation device with pressure control introduced performs a levitating operation, the posture may be disturbed due to overshoot during levitating depending on the setting state of the control system.

An object of the present invention is to provide an active vibration isolator,
In order to suppress the disturbance of the posture of the floating device due to the introduction of the pressure control, it is to realize a stable and quick floating operation in which the overshoot during the floating is suppressed.

[0006]

SUMMARY OF THE INVENTION An active vibration isolator according to the present invention for achieving the above object comprises an anti-vibration table, a support mechanism for supporting the anti-vibration table for vibration isolation, and an anti-vibration table. Pneumatic drive type actuator for applying control force, displacement detection means for detecting displacement amount of the vibration isolation table with respect to a reference position, pressure detection means for detecting air pressure of the pneumatic drive type actuator, and vibration isolation table for the reference position The target value of the displacement amount and the difference signal between the output signal of the displacement detecting means and feedback to the pneumatic drive actuator, and the pressure target value set to the pressure value at the reference position of the pneumatic drive actuator. And a compensator for compensating the difference signal between the output signals of the pressure detecting means and feeding back to the pneumatically driven actuator, and a switching for switching the compensating method of the compensator. Characterized by comprising a stage. In this active vibration isolation device, it is preferable that a determination means for determining the setting switching timing of the switching means is further provided. The determination means determines the setting switching timing of the switching means based on, for example, the position of the vibration isolation table or the output signal of the pressure detection means.

Further, in the control method for the active vibration isolation device according to the present invention, the displacement amount of the vibration isolation table, which is vibration-isolated and supported by the support mechanism, with respect to the reference position is detected, and the detected displacement amount and the vibration isolation with respect to the reference position are detected. When controlling the vibration isolation table to a predetermined position by feeding back a compensation signal that compensates the difference signal between the displacement amount of the oscillation table and the target value to the pneumatic drive actuator that applies a driving force to the vibration isolation table, It is characterized in that whether or not the difference signal between the pressure signal of the pressure detecting means for detecting the pressure of the actuator and the target pressure value of the actuator is fed back to the pneumatic actuator is switched at an appropriate timing. What is proper timing?
For example, when the vibration isolation table reaches the vicinity of the reference position, or when the air pressure of the actuator exceeds the pressure target value.

[0008]

According to the first active vibration isolator of the present invention, in order to realize the operation in which the overshoot is suppressed in the levitation operation when the compensating method introducing the pressure control is used, the following method is used. The compensation method switching means is used to switch the compensation method at an appropriate timing. In order to suppress the overshoot during ascent when using the compensation method that introduced pressure control, set the compensation method to the state where pressure control is not used at the start of ascent, and after the stable ascent position is reached, the compensation method is set. Switch to the state where pressure control is used. When the compensation method is switched by the above-described method, overshoot due to pressure control during levitation is suppressed, and stable levitation operation is possible.

In addition, the second active vibration isolator according to the present invention is intended to suppress overshoot and realize an operation in a shorter time during the levitation operation when the compensation method introducing the pressure control is used. , According to the method described below
The compensation method switching means is used to switch the compensation method at an appropriate timing. In order to suppress overshoot during levitation when using the compensation method that introduced pressure control, set the compensation method to the state that pressure control is not used at the start of levitation, and the pressure value is the pressure value at the stable levitation position. After the pressure target value set in step 1 is reached, the compensation method is switched to the state in which pressure control is used. When the compensating method is switched by the above-mentioned method to levitate, overshoot due to pressure control during levitating is suppressed, and stable levitating operation becomes possible. Further, the increase in the time required to complete the levitation for the levitation operation when pressure control is not used is small.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 shows the configuration of an active vibration isolator according to the first embodiment of the present invention. In the figure, a vibration isolation table 1 is provided on a device installation foundation 2 such as a floor, and a plurality of vibration isolation mounts 3 for supporting the vibration isolation table 1 against vibrations and applying vertical and horizontal control forces to the vibration isolation table 1. Is placed through. The vibration isolation table 1 is provided with vertical displacement detection means 4 for detecting the vertical displacement amount with respect to the reference position, and horizontal displacement detection means 5 for detecting the horizontal displacement amount with respect to the reference position of the vibration isolation table 1. ing.

The outputs of the vertical displacement detection means 4 and the horizontal displacement detection means 5 are connected to the compensation calculation means 7, and the output of the compensation calculation means 7 is connected to the vibration isolation mount 3. Further, the output of the compensation calculation method switching means 8 is connected to the compensation calculation means 7.

The anti-vibration mount 3 includes a vertical actuator that applies a vertical control force to the anti-vibration base 1, a horizontal actuator that applies a horizontal control force to the anti-vibration base 1, and an anti-vibration base 1 which are not shown. It is composed of vertical support means for supporting the vibration isolation in the vertical direction and horizontal support means for supporting the vibration isolation table 1 in the horizontal direction. The vertical and horizontal actuators use pneumatically driven actuators that control the internal pressure of the air spring by means of valves that regulate the supply and exhaust of air to it. An electromagnetically driven linear motor such as a voice coil motor, a magnetic levitation suction actuator, or the like can be used together with the actuator of the vibration isolation mount 3. The pneumatic actuators used as the vertical actuator and the horizontal actuator can also be used as the vertical support means and the horizontal support means, respectively.

The pneumatic actuator is equipped with a pressure detecting means 6 for detecting the amount of fluctuation of the pneumatic pressure. The output of the pressure detection means 6 is connected to the compensation calculation means 7. The floating state determination means 9 is a vertical displacement detection means 4
Also, it is connected to the output of the horizontal displacement detecting means 5, and the floating state is determined based on the output value. The output of the floating state determination means 9 is connected to the compensation calculation method switching means 8, and the compensation calculation method switching means 8 switches the compensation calculation method in the compensation calculation means 7 according to the output signal.

In this embodiment, in order to levitate the vibration isolation table 1 for mounting precision equipment from the apparatus installation foundation 2 to a predetermined position for vibration isolation, the vibration isolation table 1 is displaced vertically and horizontally with respect to the reference position. The amount of displacement is detected by the vertical displacement detection means 4 and the horizontal displacement detection means 5, respectively, and the target value of the displacement amount of the vibration isolation table 1 with respect to the reference position and the detection signals of the vertical displacement detection means 4 and the horizontal displacement detection means 5 are detected. The difference signal is compensated by the compensation calculation means 7 and fed back to the actuator of the vibration isolation mount 3.

A pneumatically driven actuator is used as the actuator of the vibration isolation mount 3, but if there is an illegal fluctuation in the air pressure of the actuator during stable levitation (when it is in a stable state when it is levitated), vibration isolation is performed. The precision equipment (main body device) mounted on the table 1 is adversely affected such as being deformed. Therefore, pressure feedback of the air pressure of the actuator is performed in order to suppress the air pressure fluctuation of the actuator during stable levitation. The air pressure of the actuator is detected by the pressure detecting means 6
Is detected by the compensation calculation means 7 to compensate the difference signal between the pressure target value set as the pressure value in a state of stable floating at the reference position and the detection signal of the pressure detection means 6, and the actuator of the vibration isolation mount 3 is compensated. provide feedback. In this embodiment, pressure feedback is performed for each leg.

FIG. 2 shows a control block diagram of this embodiment.
In this embodiment, the state in which the above-mentioned pressure feedback is performed in the compensation calculation means 7 is called a pressure control state, and the state in which it is not performed is called a pressure non-control state. When the levitation operation is performed in the pressure controlled state, the overshoot may be larger than that in the non-pressure-controlled levitation due to the mismatch between the levitation position and the pressure. Therefore, the compensation calculation method switching unit 8 switches the compensation method of the compensation calculation unit 7 from the time when the levitation starts until the stable levitation is achieved, thereby suppressing overshoot during levitation. First, the compensation calculation means 7 is set to a pressure non-controlled state by the compensation calculation method switching means 8 at the start of ascent, and the ascent starts. After the difference signal between the vertical displacement detection means 4 and the vertical levitation target value converges within a predetermined value and the levitation state determination means 9 detects that it is in the vicinity of the stable levitation position, the compensation calculation method switching means 8 performs compensation calculation. Switch means 7 to the pressure controlled state.

Next, the operation will be described. FIG. 3 shows a levitation operation waveform of a conventional example in which the surface is levitated in a pressure non-controlled state, that is, pressure control is not performed. Start ascending at t1. At t2, the target value is exceeded and overshoot occurs. Then, at t3, it converges on the target flying position DT1. The displacement waveform of the vibration isolation table at this time is as shown by D1, and the air pressure value of the actuator of the vibration isolation mount 3 is P1.
It changes like.

FIG. 4 shows a levitating operation waveform in the case of levitating by a conventional method by a compensation method introducing pressure control. In this conventional method, the compensating method is in the pressure control state during the levitation from the start of the levitation. Start ascending at t4. At t5, the target value is exceeded and overshoot occurs. Then, at t6, the floating target position DT2
Converge to. The displacement waveform of the vibration isolation table becomes as shown by D2, and the air pressure value of the actuator of the vibration isolation mount 3 changes as shown by P2. In this way, when levitation is performed by the conventional method that introduces pressure control, a large overshoot may occur compared to levitation by the conventional compensation method that does not introduce pressure control, which causes the vibration isolation table during levitation. There is a case where the posture of No. 1 is disturbed and the possibility of contact with an external device or the like not mounted on the vibration isolation table increases.

It is necessary to minimize the possibility of contact with external equipment in order to eliminate adverse effects on the vibration isolator and the main body mounted on the vibration isolation table of the vibration isolator. So first
In this embodiment, in order to obtain the levitating motion waveform with suppressed overshoot, the compensation calculation method switching means 8 and the flying state determination means 9 are used to switch the control method at appropriate timing according to the method described below. Do. By dividing the levitation operation into two stages, overshoot during levitation when pressure control is introduced is suppressed. The stages of the levitation operation to be set are two stages, that is, a stage of levitating to a predetermined position in the pressure non-controlled state, and a stage of switching to the pressure controlled state at the predetermined position and stabilizing the posture of the vibration isolation table 1.

FIG. 5 shows a levitating operation waveform when the levitating method of this embodiment is applied. Start ascending at t7. At the start of floating, the compensation calculation method switching means 8 sets the compensation calculation method of the compensation calculation means 7 to the pressure non-controlled state. The operation waveform during levitation is the same as the levitation operation waveform when the pressure control shown in FIG. 1 is not introduced. At t8, the flying state determination means 9 determines convergence to the vicinity of the stable flying position, and then the flying state determination means 9 outputs a compensation method switching permission signal to the compensation calculation method switching means 8. Upon receiving the compensation method switching permission signal, the compensation calculation method switching means 8 switches the compensation method of the compensation calculation means 7 to the pressure control state. At t9, it converges to the levitation target position DT3, the posture of the vibration isolation table 1 is stabilized, and levitation is completed. The displacement waveform of the vibration isolation table becomes as shown by D3, and the air pressure value of the actuator of the vibration isolation mount 3 changes as shown by P3. Disturbance of the posture due to the switching of the compensation method is smaller than that of the levitation overshoot in the pressure control state. As a result, the levitating operation waveform D3 becomes stable with suppressed overshoot. In this way, in the levitation operation, the initial levitation operation is performed in the pressure non-controlled state, and the pressure control state is switched to the stable levitation position, whereby the levitation operation with suppressed overshoot is possible. Further, since the pressure control is performed at the stable floating position, more precise position control is performed.

[Second Embodiment] Next, a second embodiment according to the present invention will be described. FIG. 6 shows the configuration of an active vibration isolator according to the second embodiment of the present invention. In the figure, a vibration isolation table 1 is provided on a device installation foundation 2 such as a floor, and a plurality of vibration isolation mounts 3 for supporting the vibration isolation table 1 against vibrations and applying vertical and horizontal control forces to the vibration isolation table 1. Is placed through. The vibration isolation table 1 is provided with vertical displacement detection means 4 for detecting the vertical displacement amount with respect to the reference position, and horizontal displacement detection means 5 for detecting the horizontal displacement amount with respect to the reference position of the vibration isolation table 1. ing.

The outputs of the displacement detection means 4 and 5 are connected to the compensation calculation means 7, and the output of the compensation calculation means 7 is the vibration isolation mount 3.
It is connected to the. Further, the output of the compensation calculation method switching means 8 is connected to the compensation calculation means 7. The anti-vibration mount 3 includes a vertical actuator that applies a vertical control force to the anti-vibration table 1, a horizontal actuator that applies a horizontal control force to the anti-vibration table 1, and an anti-vibration table 1 that are not shown in the vertical direction. It is composed of vertical support means for vibration-proof support and horizontal support means for vibration-proof support of the vibration isolation table 1 in the horizontal direction.

As the vertical actuator and the horizontal actuator, a pneumatically driven actuator is used which controls the internal pressure of the air spring by means of a valve that regulates the supply and exhaust of air to and from it. Further, a combination of an electromagnetically driven linear motor such as a voice coil motor and a magnetic levitation suction actuator can be used. The pneumatic drive type actuator used as the vertical actuator and the horizontal actuator can also be used as the vertical support means and the horizontal support means.

The pneumatic actuator is equipped with pressure detection means 6 for detecting the amount of fluctuation of the pneumatic pressure. The output of the pressure detection means 6 is connected to the compensation calculation means 7 and the floating state determination means 9. The floating state determination means 9 determines the floating state based on the output value of the pressure detection means 6. The output of the floating state determination means 9 is connected to the compensation calculation method switching means 8, and the compensation calculation method switching means 8 switches the compensation calculation method to the compensation calculation means 7 according to the output value.

In this embodiment, in order to suppress the overshoot when the surface is floated in the pressure control state, the step of ascending to a predetermined pressure in the pressure non-control state and the switching to the pressure control state after reaching the predetermined pressure are performed. The levitation operation is divided into two stages, that is, the stage until the shaking table 1 stably floats. The transition of the levitation operation stage is performed by switching the compensation method of the compensation calculation means 7 by the compensation calculation method switching means 8 from the time when the levitation starts until the stable floating position is reached. At the start of floating, the compensation calculation method switching means 8 sets the compensation calculation means 7 in the pressure non-controlled state and starts floating. After the floating state determination means 9 detects that the output signal of the pressure detection means exceeds the target pressure value, the compensation calculation method switching means 8 causes the compensation calculation means 7 to operate.
To the pressure control state.

FIG. 7 shows a levitating operation waveform in the levitating method of this embodiment. The floating operation starts at t10. At the start of floating, the compensation calculation method switching means 8 sets the compensation calculation method of the compensation calculation means 7 to the pressure non-controlled state. Therefore, the operation waveform until the air pressure of the pneumatic actuator reaches the pressure target value and the compensation method of the compensation calculation means 7 is switched to the pressure control state is the same as the levitation operation waveform when pressure control is not introduced (FIG. 3). . Floating state determination means 9 at t11
Exceeds the pressure target value and outputs a switching permission signal to the compensation calculation method switching means 8. The compensation calculation method switching means 8 switches the compensation calculation means 7 to the pressure control state. t
At 12, the vibration levitation target position DT4 is converged, the vibration isolation table 1 converges to the stable levitation position, and the levitation is completed. The displacement waveform of the vibration isolation table 1 is D4
The air pressure value of the actuator of the vibration isolation mount 3 changes as shown in P4. Disturbance of the posture due to the switching of the compensation method is smaller than that of the floating overshoot in the pressure control state shown in FIG. As a result, the levitation operation waveform D4 from the levitation start position becomes stable with overshoot suppressed. Since the switching is performed without waiting for the position to converge, the time required to reach stable levitation can be shortened as compared with the case of FIG. As described above, by switching the compensation method to suppress the overshoot during the levitation, the levitation operation can be performed without disturbing the posture of the apparatus.

[0027]

As described above, the active anti-vibration device according to the present invention is in the levitating state in order to realize the operation in which the overshoot is suppressed in the levitating operation when the compensation method introducing the pressure control is used. Switch the compensation method.
By switching the compensation method in the above-mentioned manner, the disturbance of the posture of the main body during floating that occurs when pressure control is introduced is reduced, and adverse effects due to impact on the equipment such as contact with external equipment are avoided. It will be possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an active vibration isolation device according to a first embodiment of the present invention.

FIG. 2 is a control block diagram by the compensation calculation means and the compensation calculation switching method conversion means of FIG.

FIG. 3 is a diagram showing an operating state in the case of levitating in the same pressure non-controlled state as in the first conventional example in which pressure control is not performed.

FIG. 4 is a diagram showing an operating state in the case of levitating in the same pressure control state as the second conventional example in which pressure control is introduced.

FIG. 5 is a diagram showing an operation state in the case of levitating by the method of switching the compensation method by the apparatus of FIG.

FIG. 6 is a configuration diagram of an active vibration isolator according to a second embodiment of the present invention.

FIG. 7 is a diagram showing an operation state in the case of levitating by the method of switching the compensation method by the apparatus of FIG.

[Explanation of symbols]

1: Vibration isolation table, 2: Device installation foundation, 3: Vibration isolation mount,
4: Vertical displacement detection means, 5: Horizontal displacement detection means, 6: Pressure detection means, 7: Compensation calculation means, 8: Compensation method switching means, 9: Floating state determination means, t1, t4, t7, t1
0: Ascent start time, t2, t5: Final target position arrival time, t3, t6, t9, t12: Final target position convergence time, t8, t11: Compensation method switching time, DT1 to DT
4: Final target value, D1 to D4: Levitating motion displacement waveform, P1
-P4: Levitating pressure waveform.

Claims (9)

[Claims] 1. An anti-vibration table, a support mechanism for supporting the anti-vibration table in a vibration-proof manner, a pneumatic drive actuator for applying a control force to the anti-vibration table, and a displacement amount of the anti-vibration table with respect to a reference position. Displacement detecting means, pressure detecting means for detecting the pressure of the pneumatically driven actuator, and a difference signal between a target value of the displacement amount of the vibration isolation table with respect to a reference position and an output signal of the displacement detecting means to compensate the difference signal. It feeds back to the pneumatic drive actuator, and compensates the difference signal between the pressure target value set to the pressure value at the reference position of the vibration isolation table and the output signal of the pressure detecting means and feeds back to the pneumatic drive actuator. An active vibration isolator comprising a compensator and a compensation method switching means for switching a compensation method of the compensator. 2. The active vibration isolation according to claim 1, wherein the compensation method switching means switches the compensation method of the compensator between a compensation method including pressure feedback and a compensation method not including pressure feedback. apparatus. 3. A vibration detecting means for detecting the vibration of the vibration isolation table, and a compensator for compensating a detection signal from the vibration detecting means and feeding back to the actuator. The active vibration isolator according to 1. 4. A levitation determination means for determining the position of the vibration isolation table or the air pressure of the pneumatically driven actuator is further provided, and the compensation method switching means is based on the output of the levitation determination means. The active vibration isolator according to any one of claims 1 to 3, wherein a compensation method is switched. 5. A displacement amount of a vibration isolation table, which is vibration-isolated and supported by a support mechanism, with respect to a reference position is detected, and a difference signal between the detected displacement amount and a target value of the displacement amount of the vibration isolation table with respect to the reference position is detected. A pressure signal of a pressure detecting means for detecting the pressure of the actuator when controlling the vibration isolation table to a predetermined position by feeding back the compensated compensation signal to the pneumatically driven actuator that applies a driving force to the vibration isolation table; A control method for an active vibration isolator, comprising switching whether or not a difference signal from a target pressure value is fed back to the actuator at an appropriate timing. 6. The posture of the vibration isolation table during levitation by performing the switching so as to suppress an increase in overshoot during levitation due to introduction of pressure control for feeding back the difference signal to the pneumatically driven actuator. The control method according to claim 5, wherein the disturbance of 7. The control method according to claim 5, wherein the switching timing is determined based on the position of the vibration isolation table or the air pressure of the pneumatically driven actuator. 8. The control method according to claim 7, wherein the switching is performed when the floating position of the vibration isolation table converges near the reference position. 9. The control method according to claim 7, wherein the switching is performed when the pressure of the pneumatically driven actuator exceeds a target pressure value.