JP2007298102A - Gas spring type vibration resistant device and control method for the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas spring type vibration resistant device capable of conducting precision control of which response is higher than a conventional one while maintaining a strong point to restrict an exhaust flow rate by using a flow control type valve and a control method for the device. <P>SOLUTION: In the vibration resistant device with a spool valve and a pressure differential meter, nonlinearity of the spool valve is compensated by conducting control so that a feedback value of the pressure differentiation value follows a normative model Gref in which relation of an input voltage and an output flow rate has linearity including a zero point in order to improve dynamic characteristics of the spool valve in its dead zone. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gas spring type vibration isolation device, a vibration isolation method using the vibration isolation device, and a control method of the device.

  The gas spring vibration isolator is used for vibration control of a semiconductor manufacturing apparatus or an inspection apparatus that measures the line width of a semiconductor. A conventional gas spring 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 spring such as an air spring, and controls the displacement and acceleration of the air spring by feedback. Is done. Or the method of feeding back the pressure in an air spring is also proposed. For example, Patent Document 1 discloses an anti-vibration mount device intended to improve pressure control resolution.

  A pressure control type valve such as a nozzle flapper valve has 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 is in a first order lag relationship with respect to the input. A 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 a running cost is required 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 reduce the air consumption flow rate. It is possible to do. However, fine pressure control is required in the air spring of the vibration isolator, and the construction of the micro pressure control system using the conventional pressure sensor and the flow control type valve is not sufficient for the resolution of the pressure sensor or the vibration isolator. It was very difficult because of problems such as changes in equilibrium pressure due to disturbance to

Therefore, the applicant of the present application has proposed to construct a cascade control system using a pressure differential meter (see Patent Document 2) that has been developed and is publicly known. 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 a control method are also described in Japanese Patent Application No. 2004-333638 by the same applicant as the present application.
JP 2005-282696 A JP 2005-98991 A

  Since the pressure differential meter described in Patent Document 2 can measure a pressure change in a container to be measured with low noise and high resolution, a vibration isolator using a nozzle flapper valve even when a spool valve is used. Equivalent vibration isolation performance can be obtained, and energy saving can be achieved by suppressing the exhaust flow rate. However, in a flow control type valve such as a spool valve, in general, as shown by a plurality of black dot plots in FIG. 9, the output (flow rate) with respect to the input voltage is not linear (linear graph shown in FIG. 9). Specifically, there is a region Z called a “dead zone” in which the output change with respect to the input change is zero or small before and after the origin (input and output are zero). This dead zone is an area that is difficult to control because the output does not change much even if the input is greatly changed. In addition, the output flow rate of the spool valve when used in a vibration isolator is usually included in this dead zone, so when using a spool valve, cascade control using a pressure differential meter cannot sufficiently compensate the dead zone, The anti-vibration performance is almost the same as when using a pressure control type valve, and further improvement of the anti-vibration performance has been desired.

  Further, when the load fluctuation due to the environmental change 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 isolator that uses a flow control valve and has a higher vibration isolation performance than the conventional one is desired.

  Accordingly, the present invention provides a gas spring type vibration isolator capable of highly accurate control with higher response than the conventional one and a control method thereof while maintaining the advantage of suppressing the exhaust flow rate using a flow control type valve. The purpose is to do.

  In order to achieve the above object, the invention according to claim 1 includes a vibration isolation table, a gas spring that supports the vibration isolation table, a flow control valve that supplies and exhausts air to and from the gas spring, Position detection means for detecting the position of the vibration isolation table, acceleration detection means for detecting the acceleration of the vibration isolation table, and the flow control valve based on the output of the position detection means and the acceleration detection means. A vibration isolator having a control device, wherein 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, Provided is a vibration isolation device that performs model following control that follows a reference model that compensates for nonlinearity of the flow control valve.

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

  A third aspect of the present invention is the vibration isolator according to the second aspect, further comprising a pressure differential meter that detects a pressure change in the gas spring, and the control device includes the model following control, There is provided a vibration isolator that performs control to cause a pressure differential value measured by a pressure differential meter to follow a pressure differential value obtained by multiplying an output flow rate of the reference model by a predetermined coefficient.

  According to a fourth aspect of the present invention, the vibration isolator according to the second aspect further includes flow rate detection means for detecting an output flow rate of the flow rate control type valve, and the control device is configured to perform the model following control, An anti-vibration device is provided that performs control to cause the output flow rate measured by the flow rate detection means to follow the output flow rate of the reference model.

  According to a fifth aspect of the present invention, in the vibration isolation device according to any one of the first to fourth aspects, the follow-up control includes a speed feedback control that feeds back a speed of the vibration isolation table. I will provide a.

  A sixth aspect of the present invention provides the vibration isolation device according to any one of the first to fifth aspects, wherein the flow control valve is a spool valve.

  The invention according to claim 7 detects the position of the vibration isolation table, the gas spring that supports the vibration isolation table, the flow control valve that supplies and exhausts the gas spring, and the position of the vibration isolation table And a control device that controls the flow control valve based on the output of the position detection means and the acceleration detection means. A control method for an apparatus, wherein 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 is performed, and nonlinearity of the flow control type valve is compensated Provided is a method for controlling a vibration isolation device, wherein model follow-up control is performed to follow a reference model.

  According to the vibration isolation device or the control method thereof according to the present invention, the exhaust flow rate can be significantly reduced by using a flow rate control type valve, and by applying a control system that follows the reference model, The non-linearity of the flow control type valve can be compensated. Therefore, it is possible to obtain a vibration isolator having a low running cost and a high vibration isolation performance.

  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, the 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, it becomes possible to perform highly accurate control even when the speed of the vibration isolation table cannot be ignored.

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 spring vibration isolator 10 according to a first embodiment of the present invention. The vibration isolator 10 is a typical gas spring, an air spring 12 having a buffer tank 12a and a bellows portion 12b, a vibration isolator 14 disposed on the air spring 12, and displacement and acceleration of the vibration isolator 14. Position detecting means, ie, position sensor 16 and acceleration detecting means, ie, acceleration sensor 18. Further, the vibration isolator 10 includes an air supply source 20 that supplies air to the air spring 12 and a flow rate control type valve 22 that controls the flow rate of air from the air supply source 20 and sends it to the air spring 12. A suitable flow control valve includes 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 spring 12.

  The vibration isolator 10 includes a control device 26 that performs feedback control, which will be described later. The control device 26 includes filters 28a, 28b, and 28c having appropriate amplification degrees and time constants, a comparator 30, a PI compensator 32, and I compensator 34 is provided. As shown in the figure, the output of the acceleration sensor 18 is used to adjust the valve opening degree of the spool valve 22 through the filter 28b. The output of the position sensor 16 is compared with the set displacement by the comparator 30 through the filter 28a, and the result, that is, the deviation signal is passed through the PI compensator 32 and used for adjusting the valve opening of the spool valve. Further, the output of the pressure differential meter 24 is used for adjusting the valve opening degree of the spool valve through the filter 28c and the I compensator 34, which will be described later.

  The basic structure of the pressure differential meter 24 is the same as that described in Patent Document 2. For example, as shown in FIG. 2, an isothermal pressure vessel 24a, a buffer tank portion 12a of the air spring 12 to be measured, A conduction path (a plurality of slits in the illustrated example) 24b communicating with the isothermal pressure vessel 24a, and a differential pressure gauge (a diaphragm type differential pressure meter in the illustrated example) for detecting a pressure difference between the isothermal pressure vessel 24a and the buffer tank 12a. ) 24c. By using the pressure differential meter 24, the pressure differential value in the buffer tank 12a can be obtained with low noise and high resolution. An example in which a pressure differential meter is applied to an air spring type vibration isolator is also described in Japanese Patent Application No. 2004-333638 by the same applicant as the present application.

Next, a control method of the vibration isolator 10 will be described. First, for comparison, a control block diagram of an air spring vibration isolator using a conventional nozzle flapper type servo valve is shown in FIG. In a pressure control type valve such as a nozzle flapper valve, the pressure P in the air spring has a first-order lag relationship with respect to the input voltage u, and the relationship between the pressure P and the vibration isolation table displacement x is as shown in FIG. Have 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 the displacement x, PI control with respect to the target value, acceleration d ² x / dt ^{For 2} , feedback control is performed using a 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 spring, the cross-sectional area of the portion in the air spring that supports the load, and the air spring, respectively. Spring constant and viscosity coefficient.

  Next, FIG. 4 is a control block diagram of an air spring type vibration isolator using a spool valve and a pressure differential meter proposed by the present applicant in Japanese Patent Application No. 2004-333638. 4 differs from FIG. 3 in the portion surrounded by a broken line, and the other portions may be the same as those in FIG. R, θ, and V are a gas constant, an absolute gas temperature, and an air spring volume, 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 Kv), and the above-described “dead zone” of the spool valve is not taken into consideration. Therefore, although the vibration isolator equivalent to the vibration isolator using the nozzle flapper valve can be obtained by using the pressure differential meter, it is difficult to obtain sufficiently fast dynamic characteristics when the speed of the vibration isolator 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. 5 is different from FIG. 3 or FIG. 4 in a portion surrounded by an alternate long and short dash line, and other portions may be the same as those in FIG. 3 or FIG. A feature of the first embodiment is that, in addition to having a pressure differential value feedback loop as in FIG. 4, reference model following control is performed in feedback of the pressure differential value.

As shown in the broken line portion of FIG. 5, the output flow rate G with respect to the input voltage u of the spool valve 22 exhibits non-linearity. In other words, there is a “dead zone” in which the output change with respect to the input change is substantially or blunt. 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 has a linearity in which the relationship between the input voltage and the output flow rate passes through the zero point ( Control is performed so as to follow a value obtained by multiplying the reference model Gref (multiplied by the proportional gain Kv) by a predetermined coefficient to compensate for the non-linearity of the spool valve. A suitable reference model Gref is a model that satisfies G = Kv · u, for example, as a linear graph shown in FIG. As described above, the fine pressure fluctuation in the buffer tank 12a of the air spring 12 is detected by a high-resolution pressure differential meter, and the obtained value (signal) is subjected to feedback processing of the tracking control system, thereby achieving high accuracy. In addition, 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. Note that K _ad , K _adl, and T _ad are the proportional gain, integral gain, and filter time constant of follow-up control, respectively.

  Further, as shown in FIG. 5, in the first embodiment, a value (signal) obtained by multiplying the vibration dampening table speed dx / dt by a coefficient can be incorporated into the feedback loop of the pressure differential value. 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 from integration of an acceleration signal, differentiation of a displacement signal, or 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 spring 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. A gas spring vibration isolator 10 ′ according to the second embodiment shown in FIG. 6 is a flow meter that measures the flow rate of the spool valve 22 instead of the pressure differential meter 24 of the vibration isolator 10 according to the first embodiment. 36. The other components of the vibration isolator 10 ′ shown in FIG. 6 may be the same as those of the first vibration isolator 10, and thus the description thereof is omitted.

  FIG. 7 is a control block diagram of the second vibration isolator 10 ′. Here, the flow rate G measured by the flow meter 36 is compared with the flow rate model Gref 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 concept may be the same as that described with reference to FIG. Therefore, in the second embodiment, control is performed so that the flow rate G is controlled to minimize the displacement of the vibration isolation table 14 and the change in acceleration. Note that the flow meter 36 is preferably a highly responsive flow meter capable of measuring the flow rate of an unsteady flow fluid as described in, for example, Japanese Patent Application Laid-Open No. 2004-77327.

  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 (A) of the portion in the air spring: 72.4 × 10 ⁻⁴ [m ² ]
Load weight (m): 87 [kg]
Air spring volume (V): 1.7 × 10 ⁻³ [m ³ ]

  In the experiment, an air spring with a stroke of about 2 mm was used, the vibration isolator was floated at a predetermined displacement (here, 1.4 mm), and the stability of the acceleration signal of the vibration isolator was removed using a conventional nozzle flapper valve. Compared with shaker. A comparison of the steady exhaust flow rates of the spool valve and the nozzle flapper valve was also performed. The pressure in the air spring during the experiment was about 270 kPa (abs).

  As a result of the experiment under the above conditions, the steady exhaust flow rate was 0.75 Nl / min in the vibration isolator according to the first embodiment. As a comparison, in the case of the vibration isolator using the nozzle flapper valve for the same air spring, the steady exhaust flow rate was 16.7 Nl / min, so it can be seen that the consumption flow rate can be greatly reduced to about 1/22.

  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. . A solid line L1 indicates the former acceleration waveform, and a broken line L2 indicates 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.

It is a figure which shows the suitable structural example of the vibration isolator of 1st Embodiment which concerns on this invention. It is a figure which shows the detailed structure of the pressure differential meter shown in FIG. It is a control block diagram of the conventional vibration isolator using a nozzle flapper valve. It is a control block diagram of the vibration isolator of the first embodiment, but does not include follow-up control. It is a control block diagram of the vibration isolator of 1st Embodiment, and is a figure including follow-up control. It is a figure which shows the suitable structural example of the vibration isolator of 1st Embodiment which concerns on this invention. It is a control block diagram of the vibration isolator of 2nd Embodiment. It is a graph which compares the acceleration waveform of the vibration isolator at the time of steady operation with the vibration isolator of 1st Embodiment, and the conventional vibration isolator. It is a graph which shows the relationship of the output flow volume with respect to input voltage in the normal spool valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Vibration isolator 12 Air spring 14 Vibration isolator 16 Position sensor 18 Acceleration sensor 20 Air supply source 22 Spool valve 24 Pressure differential meter 26 Controller 36 Flow meter

Claims (7)

A vibration isolation table, a gas spring 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 the position of the vibration isolation table, and the vibration isolation table An anti-vibration device comprising: an acceleration detection means for detecting the acceleration of the 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,
The control device performs cascade control including a position feedback loop using the output of the position detection unit and an acceleration feedback loop using the output of the acceleration detection unit, and compensates for nonlinearity of the flow control type valve A vibration isolator that performs model follow-up control to follow the vibration.   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.   A pressure differential meter that detects a pressure change in the gas spring; and the control device is configured to set a pressure differential value measured by the pressure differential meter to an output flow rate of the reference model in the model following control. The vibration isolation device according to claim 2, wherein control is performed to follow a pressure differential value multiplied by a coefficient of.   The flow control type valve further includes a flow rate detection unit that detects an output flow rate of the flow rate control type valve, and the control device causes the output flow rate measured by the flow rate detection unit to follow the output flow rate of the reference model in the model following control. The vibration isolator according to claim 2, which performs control.   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.   The control method according to claim 1, wherein the flow control valve is a spool valve. A vibration isolation table, a gas spring 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 the position of the vibration isolation table, and the vibration isolation table A control method for a vibration isolator comprising: an acceleration detection means for detecting an acceleration of a table; and a control device for controlling the flow control valve based on outputs of the position detection means and the acceleration detection means,
Model following that 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, and follows a reference model that compensates for the nonlinearity of the flow control valve A method for controlling a vibration isolator, comprising performing control.

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