WO2007125663A1

WO2007125663A1 - Gas spring type vibration isolator and method of controlling the device

Info

Publication number: WO2007125663A1
Application number: PCT/JP2007/052300
Authority: WO
Inventors: Kenji Kawashima; Toshiharu Kagawa
Original assignee: Tokyo Institute Of Technology
Priority date: 2006-04-28
Filing date: 2007-02-02
Publication date: 2007-11-08
Also published as: JP4113960B2; JP2007298102A

Abstract

A vibration oscillator comprises a spool valve and a pressure differentiator. In order to improve the dynamic characteristics of the spool valve in the dead band, the vibration isolator is so controlled that the feedback value of pressure differential value follows a reference model having such a linearity that the relation between an input voltage and an output flow passes through a zero point to compensate the nonlinearity of the spool valve.

Description

Gas panel type vibration isolator and control method of the device

Background art

1. Technical field

The present invention relates to a gas panel type vibration isolator and a vibration isolation method using the vibration isolation device.

And a method for controlling the apparatus.

Rice field

2. Description of related technology.

The gas panel type vibration isolator is used for vibration control of a semiconductor manufacturing apparatus or an inspection apparatus for measuring a semiconductor line width. A conventional gas panel type vibration isolator has a pressure control type valve such as a nozzle flapper type pneumatic servo valve to control the internal pressure of a gas panel such as an air panel, and feeds back the displacement and acceleration of the air panel. Controlled. Alternatively, a method of feeding back the pressure in the air panel has been proposed. For example, Japanese Laid-Open Patent Publication No. 2 005-2 8 2 6 96 discloses a vibration isolation mount device intended to improve pressure control resolution.

Pressure control type valves such as nozzle flapper valves have a high linearity of the valve opening with respect to the input voltage, and when used in a vibration isolator, the pressure in the air spring has a first-order lag relationship with the input 1 Next delay system can be constructed. Therefore, although the pressure control type valve is said to be suitable for pressure control in the air spring of the vibration isolator, there is a problem that running cost is increased due to a large exhaust flow rate.

In order to save energy by suppressing the exhaust flow rate of the vibration isolator, use a flow control type valve with a low exhaust flow rate, such as a spool valve, instead of a pressure control type valve, to suppress the air consumption flow rate. It is possible to do. However, fine pressure control is necessary inside the air spring of the vibration isolator, Building a fine pressure control system using a conventional pressure sensor and flow control valve has been extremely difficult due to problems such as insufficient resolution of the pressure sensor and changes in the equilibrium pressure due to disturbance to the vibration isolator.

Therefore, the applicant of the present application is a pressure differential meter that has been developed and publicly known.

(See Japanese Patent Laid-Open No. 2000-098 991) is proposed to construct a cascade control system. Thereby, even if a flow rate control type valve such as a spool type servo valve is used, the vibration isolation table of the vibration isolation device can be lifted and the exhaust flow rate can be suppressed. Such a configuration and control method are the same as those of the present application. Japanese Patent Application No. 2 0 0 4-3 3 3 6 3 8 by the applicant (Japanese Patent Laid-Open No. 2 0 0 6-1 4 4 8 5 9) It is also described in. The pressure differential meter described in Japanese Patent Laid-Open No. 2 0 0 5-9 8 9 9 1 can measure the pressure change in the container to be measured with low noise and high resolution. Even if it is used, vibration isolation performance equivalent to that of a vibration isolation device using a nozzle flapper valve can be obtained, and energy can be saved by suppressing the exhaust flow rate. However, in a flow control type valve such as a spool valve, the output (flow rate) relative to the input voltage is not linear (linear graph shown in Fig. 9), as shown by the multiple black dot plots in Fig. 9. Specifically, there is a so-called “dead zone” region Z in which the output change with respect to the input change is zero or very small around the origin (input and output are zero). This dead zone is a region that is difficult to control because the change in output is small when the input is greatly changed compared to other regions. In addition, the output fluency of the spool valve when it is used in a vibration isolator is usually included in this dead zone. Therefore, when the spool valve is used, the dead zone is sufficiently compensated for by cascade control using a pressure differential meter. However, the anti-vibration performance remained at the same level as when a pressure-controlled valve was used, and further improvement of the anti-vibration performance was desired. In addition, when the load fluctuation due to environmental changes of the vibration isolator is severe, specifically when the speed of the vibration isolation table cannot be ignored, the cascade control that feeds back the displacement and acceleration may not be sufficient. . Therefore, from this point, a vibration isolation device that uses a flow control valve and has a higher vibration isolation performance than before is desired. Summary of the Invention

Therefore, the present invention maintains a merit that the exhaust flow rate is suppressed by using a flow control type valve, and a gas panel type vibration isolator capable of highly accurate control with higher responsiveness than the conventional one and a control method therefor. The purpose is to provide

In order to achieve the above object, the present invention provides an anti-vibration table, a gas panel that supports the anti-vibration table, a flow control valve that supplies and exhausts air to the gas panel, and the anti-vibration table A position detecting means for detecting the position of the vibration isolator, an acceleration detecting means for detecting the acceleration of the vibration isolation table, and a control device for controlling the flow control valve based on outputs of the position detecting means and the acceleration detecting means. The control device performs cascade control including a position feedback loop that uses the output of the position detection means, and an acceleration feedback loop that uses the output of the acceleration detection means. In addition, the present invention provides a vibration isolator that performs model following control that follows a reference model that compensates for nonlinearity of the flow control valve.

In a preferred embodiment, in the reference model, an output flow rate of the flow control type valve has a linear relationship with an input voltage.

The vibration isolation device may further include a pressure differential meter that detects a pressure change in the gas panel, and in that case, the control device may include a pressure differential measured by the pressure differential meter in the model following control. Value Control is performed to follow the pressure differential value obtained by multiplying the output flow rate of the reference model by a predetermined coefficient.

The vibration isolation device may further include a flow rate detection unit that detects an output flow rate of the flow rate control type valve. In that case, the control device is measured by the flow rate detection unit in the model following control. Control the output flow rate to follow the output flow rate of the reference model.

In a preferred embodiment, the follow-up control includes speed feedback control for feeding back the speed of the vibration isolation table.

In a preferred embodiment, the flow control type valve is a spool valve. According to another aspect of the present invention, an anti-vibration table, a gas panel that supports the anti-vibration table, a flow control valve that supplies and exhausts gas to the gas panel, Position detecting means for detecting a position, acceleration detecting means for detecting the acceleration of the vibration isolation table, and a control device for controlling the flow control valve based on outputs of the position detecting means and the acceleration detecting means; And a cascade control including a position feedback loop using an output of the position detection means and an acceleration feedback loop using an output of the acceleration detection means, and the flow rate There is provided a control method for a vibration isolator characterized by performing model following control that follows a reference model that compensates for nonlinearity of a control valve.

In a preferred embodiment, the follow-up control includes speed feedback control for feeding back the speed of the vibration isolation table. Brief Description of Drawings

The above or other objects, features and advantages of the present invention are as follows. The form will be further clarified by describing with reference to the accompanying drawings.

FIG. 1 is a diagram showing a preferred configuration example of the vibration isolator according to the first embodiment of the present invention.

Fig. 2 is a diagram showing the detailed structure of the pressure differential meter shown in Fig. 1. Fig. 3 is a control block diagram of a conventional vibration isolator using a nozzle flapper valve.

FIG. 4 is a control block diagram of the vibration isolator of the first embodiment, but does not include tracking control.

FIG. 5 is a control block diagram of the vibration isolator according to the first embodiment, including tracking control.

FIG. 6 is a diagram illustrating a preferred configuration example of the vibration isolation device according to the first embodiment of the present invention.

FIG. 7 is a control block diagram of the vibration isolator of the second embodiment, and FIG. 8 shows the acceleration waveform of the vibration isolator during steady operation with the vibration isolator of the first embodiment and the conventional vibration isolator. It is a graph to compare with the vibration device,

Fig. 9 is a graph showing the relationship of the output flow rate to the input voltage in a normal spool valve. Detailed description

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram schematically showing a schematic configuration of a gas panel type vibration isolator 10 according to the first embodiment of the present invention. The vibration isolator 10 is a typical gas spring, an air spring 1 '2 having a buffer tank 1 2 a and a bellows portion 1 2 b, and a vibration isolation table disposed on the air spring 1 2. 1 4 、 Vibration isolation table 14 Position detection means to detect displacement and acceleration of 4 respectively, ie position sensor 1 6 and acceleration detection means, ie acceleration sensor 1 8 To do. The vibration isolator 10 includes an air supply source 2 0 that supplies air to the air panel 1 2, and a flow control valve 2 that controls the flow of air from the air supply source 20 and sends it to the air spring 12. 2 and. A suitable flow control valve is a spool valve. Further, the vibration isolator 10 has a pressure differential meter 24 developed by the same applicant as the present application in order to measure the pressure in the buffer tank portion 12 a of the air bath 12.

Further, the vibration isolator 10 has a control device 26 that performs feedback control, which will be described later, and the control device 26 has an appropriate amplification degree and time constant. A comparator 30, a PI compensator 3 2, and an I compensator 3 4. As shown in the figure, the output of the acceleration sensor 1 8 passes through the filter 2 8 b and is used to adjust the valve opening of the spool valve 2 2. The output of the position sensor 16 is compared with the set displacement in the comparator 30 through the filter 28a, and the result, that is, the deviation signal passes through the PI compensator 32 to adjust the valve opening of the spool valve. used. Furthermore, the output of the pressure differential meter 24 is used for adjusting the valve opening of the spool valve through the filter 28 c and the I compensator 34, which will be described later.

The basic structure of the pressure differentiator 2 is the same as that described in Japanese Patent Laid-Open No. 2 0 0 5-9 8 9 9 1. For example, as shown in FIG. 2, an isothermal pressure vessel 2 4 a Measured air spring 1 2 Buffer tank part 1 2 of the tank 1 2 a and the isothermal pressure vessel 2 4 a are connected to the communication path (in the example shown, multiple slits) 2 4 b and the isothermal pressure vessel 2 4 c and a differential pressure gauge (diaphragm type differential pressure gauge in the illustrated example) 2 4 c for detecting the pressure difference between the inside of the buffer tank 1 2 a and the inside of the buffer tank 1 2 a. By using the pressure differential meter 2 4, the pressure differential value in the buffer tank 1 2 a can be obtained with low noise and high resolution. An example in which a pressure differential meter is applied to an air panel type vibration isolator is shown in Japanese Patent Application No. 2 0 0 4-3 It is also described in the specification of 3 3 6 3 8 (Japanese Patent Laid-Open No. 2 0 06-1 4 4 8 5 9).

Next, a control method of the vibration isolator 10 will be described. First, for comparison, a control block diagram of an air spring type vibration isolator using a conventional nozzle flapper type suppo valve is shown in FIG. In a pressure control type valve such as a nozzle flapper valve, the pressure P in the air panel has a first-order lag relationship with the input voltage u, and the pressure P and the vibration isolation table displacement X are as shown in Fig. 3. Have a relationship. As can be seen from Fig. 3, the displacement X and acceleration d ² x / dt ² of the vibration isolation table are measured using a displacement meter and an accelerometer, respectively, and for displacement X, PI control with respect to the target value, acceleration d ² x / dt ^{For 2} , the feedback control is performed by the signal multiplied by the acceleration feedback gain Ka. K and T are the nozzle flapper output gain and time constant, respectively, and m, A, k and b are the mass of the load on the air panel, the cross-sectional area of the part in the air panel that supports the load, and the air Panel spring constant and viscosity coefficient.

Next, FIG. 4 shows a spool valve proposed by the applicant of the present application in Japanese Patent Application No. 2 0 0 4-3 3 3 6 3 8 (Japanese Patent Laid-Open No. 2 0 0 6 1 4 4 8 5 9). And a control block diagram of an air panel vibration isolator using a pressure differential meter. 4 differs from FIG. 3 in the part surrounded by a broken line, and the other parts may be the same as in FIG. R, 0 and V are the gas constant, the absolute temperature of the gas and the volume of the air panel, respectively. The feature of Fig. 4 is that it has a pressure differential feedback loop in addition to the conventional acceleration and position feedback loop. However, in this control, the output flow rate G with respect to the input voltage u is linearly approximated (multiplied by the proportional gain ν ν), and the above-mentioned “dead zone” of the spool valve is not taken into consideration. Therefore, although a vibration isolator equivalent to that using a nozzle flapper valve can be obtained by using a pressure differential meter, It is difficult to obtain sufficiently fast dynamic characteristics when the speed of the vehicle cannot be ignored.

FIG. 5 is a diagram showing a control block of the vibration isolator 10 according to the first embodiment of the present invention using a spool valve and a pressure differential meter. FIG. 5 differs from FIG. 3 or FIG. 4 in the portion surrounded by the alternate long and short dash line, and the other portions may be the same as in FIG. 3 or FIG. The feature of the first embodiment is that, in addition to having a pressure differential value feedback loop as in FIG. 4, the reference model following control is performed in the feedback of the pressure differential value.

As shown in the broken line in FIG. 5, the output flow rate G with respect to the input voltage u of the spool valve 2 2 exhibits non-linearity, in other words, the output change with respect to the input change does not substantially exist or there is a minute “dead zone”. . Therefore, in the present invention, in order to improve the dynamic characteristics of the spool valve in this dead zone, the feedback value (signal) of the pressure differential value The relationship between the input voltage and the output flow rate has a linearity that passes through the zero point ( Reference model G re This is controlled to follow the value multiplied by a predetermined coefficient to compensate for the nonlinearity of the spool valve. A suitable reference model G ref is a model that satisfies G = KV · u, for example, a linear graph shown in FIG. In this way, the fine pressure fluctuation in the buffer tank 1 2 a of the air spring 1 2 is detected by a high-resolution pressure differential meter, and the feedback value of the tracking control system is applied to the obtained value (signal). Therefore, highly accurate and highly responsive pressure control can be realized, and as a result, a vibration isolator having high vibration isolation performance can be obtained while suppressing the exhaust gas flow rate. K _ad , _Kadl, and T _ad are the proportional gain, integral gain, and time constant of the tracking control, respectively.

Further, as shown in FIG. 5, in the first embodiment, the value (signal) obtained by multiplying the vibration isolation table speed dx / dt by a coefficient is used as a feedback value differential pressure value. Can be incorporated into a group. In this way, since feedback control can be performed based on the result including the speed fluctuation, high vibration isolation performance can be obtained even when the speed of the vibration isolation table cannot be ignored. The speed signal can be obtained by integrating the acceleration signal, differentiating the displacement signal, or by a speed sensor (not shown) provided separately.

Next, a second embodiment of the vibration isolator according to the present invention will be described. In the first embodiment described above, the differential value of the pressure in the air panel is measured using a pressure differential meter and the pressure differential value is fed back. In the second embodiment described below, the pressure differential meter is used. The output flow rate of the spool valve is used for feedback instead of the pressure differential value. The gas panel type vibration isolator 10 0 ′ according to the second embodiment shown in FIG. 6 has a flow rate of the spool valve 2 2 instead of the pressure differential meter 2 4 of the vibration isolator 10 according to the first embodiment. It has a flow meter 3 6 to measure The other components of the vibration isolator 1 0 ′ shown in FIG. 6 may be the same as those of the first vibration isolator 1 0, and thus description thereof is omitted.

FIG. 7 is a control block diagram of the second vibration isolator 1 0 ′. Here, the flow rate G measured by the flow meter 36 is compared with the flow rate model G re e i having ideal linearity as the reference model described above. Except that the value to be compared is replaced with the flow rate from the pressure differential value, the other concepts may be the same as described with reference to FIG. Therefore, in the second embodiment, control is performed to control the flow rate G to suppress the displacement and acceleration changes of the vibration isolation table 14 to a minimum. As the flow meter 3 6, for example, there is a highly responsive flow meter capable of measuring the flow rate of an unsteady flow fluid as described in Japanese Patent Laid-Open No. 2000-077 3 27. I like it.

Also in this case, speed feedback of the vibration isolation table 14 can be performed. Next, examples of the present invention will be described. This example relates to a vibration isolator using a spool valve and a pressure differential meter corresponding to the first embodiment described above. The main specifications of the vibration isolator were as follows.

Effective pressure receiving area of the air panel (A):

^{7 2. 4 X 1 0 - 4} [m 2] Load weight (m): 8 7 [kg ]

Air spring volume (V): 1. 7 X 1 0— ³ [m ³ ]

In the experiment, an air spring with a stroke of about 2 mm was used to float the vibration isolation table at a predetermined displacement (1.4 mm in this case), and the stability of the acceleration signal of the vibration isolation table was improved by the conventional nozzle flapper valve. Compared with the vibration isolator using. We also compared the steady exhaust flow rates of the spool valve and the nozzle flapper valve. Note that the pressure in the air panel during the experiment was approximately 270 kPa (abs).

As a result of experiments under the above conditions, the steady-state exhaust flow rate was 0.75 N 1 / min in the vibration isolator according to the first embodiment. For comparison, in the case of a vibration isolation device using a nozzle flapper valve for the same air panel, the steady exhaust flow rate was 16.7 N1 / min, so the consumption flow rate can be significantly reduced to approximately 1/22. You can see that

FIG. 8 is a graph comparing acceleration waveforms of the vibration isolation table during steady operation between the vibration isolation device using the spool valve and the vibration isolation device using the nozzle flapper valve according to the first embodiment of the present invention. . The solid line L 1 shows the former acceleration waveform, and the broken line L 2 shows the latter acceleration waveform. As can be seen from FIG. 8, in the vibration isolator according to the first embodiment, the fluctuation range of the acceleration is generally smaller than that using the conventional nozzle flapper valve, and exhibits excellent vibration isolation performance. I understand that.

According to the vibration isolator or the control method thereof according to the present invention, the flow control type valve The exhaust flow rate can be remarkably reduced using conventional and the non-linearity of the flow control type valve can be compensated by applying a control system that follows the reference model. Therefore, a vibration isolator having a low running cost and a high vibration isolation performance can be obtained. The follow-up control is advantageously performed on the pressure differential value in the air spring detected using a pressure differential meter capable of high resolution measurement. Alternatively, follow-up control can be performed on the output flow rate of the flow control type valve.

In addition, by incorporating the speed feedback of the vibration isolation table into the follow-up control, high-precision control can be performed even when the speed of the vibration isolation table cannot be ignored.

Although the present invention has been described with reference to particular embodiments selected for illustration, it should be understood that many modifications may be made by those skilled in the art without departing from the basic concept and scope of the invention. it is obvious.

Claims

1. a vibration isolation table, a gas panel that supports the vibration isolation table, a flow control valve that supplies and exhausts air to the gas spring, a position detection unit that detects a position of the vibration isolation table, Based on an acceleration detection means for detecting the acceleration of the vibration isolation table, and the outputs of the position detection means and the acceleration detection means.

A vibration isolator having a control device for controlling the flow control valve;

The control device surrounds cascade control including a position feedback loop using an output of the position detection means and an acceleration feedback loop using an output of the acceleration detection means, and nonlinearity of the flow control type valve A vibration isolator that performs model following control to follow a reference model that compensates for noise.

2. The vibration isolation device according to claim 1, wherein in the reference model, an output flow rate of the flow control type valve has a linear relationship with an input voltage.

3. It further has a pressure differential meter for detecting a pressure change in the gas panel, and the control device uses the pressure differential value measured by the pressure differential meter in the model following control as an output flow rate of the reference model. The vibration isolator according to claim 2, wherein control is performed to follow a pressure differential value obtained by multiplying a predetermined coefficient by.

4. Further comprising a flow rate detecting means for detecting an output flow rate of the flow rate control type valve, wherein the control device uses the output flow rate measured by the flow rate detecting means in the model following control as an output flow rate of the reference model. The vibration isolation device according to claim 2, wherein control is performed to follow the vibration.

5. The vibration isolation device according to claim 1, wherein the follow-up control includes speed feedback control that feeds back a speed of the vibration isolation table.

6. The control of claim 1, wherein the flow control valve is a spool valve. Your method.

7. a vibration isolation table, a gas panel that supports the vibration isolation table, a flow control valve that supplies and exhausts air to the gas panel, a position detection unit that detects a position of the vibration isolation table, A method for controlling a vibration isolator comprising: an acceleration detection means for detecting an acceleration of a vibration isolation table; and a control device for controlling the flow control valve based on the output of the position detection means and the acceleration detection means. And

Cascade control including a position feedback loop that uses the output of the position detection means and an acceleration feedback buckle that uses the output of the acceleration detection stage and compensates for the nonlinearity of the flow control valve A method for controlling a vibration isolator characterized by performing model following control to follow a reference model to be performed.

8. The control method according to claim 7, wherein in the reference model, an output flow rate of the flow control type valve has a linear relationship with an input voltage.

9. The control method according to claim 7, wherein the follow-up control includes speed feedback control that feeds back a speed of the vibration isolation table.