JP2002235794A - Active vibration resistant device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active vibration resistant device which can perform a high accurate vibration resistant control by inputting a detected vibration signal of a wide range from a minimum value to a maximum value of a detected vibration level to perform arithmetic calculation necessary for the vibration resistant control. SOLUTION: This active vibration resistant device is equipped with an elastic spring floatingly supporting a vibration resistant base a position detection means 22 detecting a floated position of the vibration resistant base, a vibration detection means 21 detecting vibration of the vibration resistant base, an arithmetic processing means 23 performing arithmetic calculation necessary for the vibration resistant control using a detected signal of the position detection means 22 and a detected signal of the vibration detection means 21, and an electromagnetic actuator 18 drive controlling the vibration resistant base, to drive-control the electromagnetic actuator 18 by an output of the arithmetic processing means 23. The device is equipped with a square-root conversion means 26, converts into a square root a vibration detection value detected by the vibration detection means 21. And non-linearly inputs it to the arithmetic processing means 23. In this way, the vibration detected value of a wide range from a detected minimum vibration level to a maximum vibration level can be inputted to the arithmetic processing means 23.

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 equipped with a mechanical device such as an electron microscope which dislikes vibration, and more particularly to an active vibration isolator capable of widely using a detection signal of a vibration sensor for vibration isolation control. The present invention relates to a vibration device.

[0002]

2. Description of the Related Art FIG. 1 is a diagram showing an example of the configuration of an active vibration isolator of this type. As shown in the drawing, the vibration isolator 10 has a vibration isolator base 13 installed on a vibration isolator base 12 installed at a vibration isolator installation location 11, and a plurality of air springs 14 on the vibration isolator base 13. And a plurality of air springs 14 are used to levitate and support the vibration isolation table 15. Anti-vibration table 15
A mechanical device (for example, an electron microscope) 16 that dislikes vibration is mounted on the upper side. Reference numeral 18 denotes an electromagnetic actuator, which is controlled by an anti-vibration control device 20 to eliminate vibration of the anti-vibration table 15. In addition,
19 is a vibration sensor for detecting vibration of the vibration isolation table.

FIG. 2 is a diagram showing the configuration of a conventional anti-vibration control device. The anti-vibration control device 20 is configured to include a vibration detection unit 21, a position detection unit 22, an arithmetic processing unit 23, and a drive control unit 24, as illustrated. Vibration detecting means 21
Detects the vibration of the vibration isolation table 15 from the output of the vibration sensor 19 and inputs the detected vibration value to the arithmetic processing means 23. The position detecting means 22 detects a floating position of the vibration isolation table 15 from an output of a displacement sensor 25 (usually built in the electromagnetic actuator 18) for detecting a displacement of the vibration isolation table 15, and calculates a position detection signal. Input to processing means 23. The arithmetic processing unit 23 performs an operation necessary for vibration isolation control based on the position detection signal of the position detection unit 22 and the vibration detection signal of the vibration detection unit 21, and outputs the vibration isolation control signal to the drive control unit 24. The unit 24 controls the driving of the electromagnetic actuator 18 to eliminate the vibration of the vibration isolation table 15.

[0004] In the active vibration isolator having the above structure,
The vibration detection range of the vibration isolation table 15 needs to be detected over a wide range. Common vibration area of active vibration isolation device and vibration isolation table 1
5 has a numerically extremely large difference between the external vibration region generated by the mechanical device 16 mounted on the device 5 and the range of the vibration detection signal input from the vibration detection means 21 to the arithmetic processing means 23. Conventionally, the input range is determined by suppressing the amplification degree of the vibration sensor 19 so that the vibration can be detected in a wider range. However, the S / N ratio of the detection sensitivity in the normal vibration region becomes poor, There was a limit to the vibration control. FIG. 3 is a diagram illustrating an example of a vibration level of a general vibration sensor and a detection value thereof.

[0005] In an active vibration isolator, the vibration level that one actually wants to control is usually 0.0005 m / s ^{2 to} 0.
Is a 01M / s ^2, the mechanical device 16 which is mounted on anti-vibration table 15, for generating a vibration of about 0.5 m / s ² back and forth, for the anti-vibration control about 0.0005 m / s ² It is necessary to detect a vibration in a region of about 0.5 m / s ² , which is normalized to 1: 1000. That is, the dynamic range is 1000. If the input signal is not more than 20 mV, the operational amplifier is difficult to operate. Therefore, when the detected vibration signal is small, a method of amplifying the detected vibration signal in the vibration detecting means 21 and adjusting the signal level used commonly is implemented. If it is amplified, it will be amplified with noise, and not only will the S / N ratio be reduced,
The output characteristics of an operational amplifier, which is an electronic component element used for a signal amplifying means, cannot be output beyond the power supply voltage of the operational amplifier and saturates, so that the degree of signal amplification is limited.

FIG. 4 is a diagram showing input / output characteristics of a general operational amplifier having a 10-fold amplification factor in which 10 V is output with respect to 1 V input. In FIG. 4, A indicates an ideal output of the operational amplifier, and B indicates an operational amplifier output when a power supply of ± 15 V is used. When the minimum vibration level and the maximum vibration level of the vibration to be controlled are extreme, and when the detection is performed with emphasis on the minimum value, the amplification degree of the operational amplifier is increased by 100 times, and
Although it can be set arbitrarily to 000 times, the maximum value is also amplified at the same time, so that the range of the detected vibration level is limited.

The detected vibration signals corresponding to 0.0005 m / s ² and 0.5 m / s ² are 0.00025 V and 0.25 V from FIG. In this case, by using the amplification factor of 100 times, the detected vibration signal of the minimum vibration level becomes 25 mV and reaches the operational amplifier operating region, but the detected vibration signal of the maximum vibration level reaches 25 V and the operational amplifier reaches 10 V as described above. Output, the maximum vibration level is greatly reduced and the dynamic range is 40
It becomes smaller to zero. Further, even if the amplification degree and the vibration level range are adjusted, the dynamic range is limited to about 500, and the range of the vibration level that can be input is narrower than the target vibration control range of the active vibration isolation device. It was a problem.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is required for vibration isolation control by inputting a wide range of detected vibration signals from the minimum value to the maximum value of the detected vibration level. It is an object of the present invention to provide an active vibration isolation device that can perform various calculations and perform high-precision vibration isolation control.

[0009]

According to a first aspect of the present invention, there is provided an elastic spring for levitating and supporting a vibration isolation table, and a displacement detecting means for detecting a floating position of the vibration isolation table. Vibration detection means for detecting vibration of the vibration isolation table, arithmetic processing means for performing calculations required for vibration isolation control based on a detection signal of the displacement detection means and a detection signal of the vibration detection means, and drive control of the vibration isolation table. In an active vibration isolator that includes an electromagnetic actuator and drives and controls the electromagnetic actuator based on the output of the arithmetic processing unit, a small signal detected by the vibration detecting unit is input to the arithmetic processing unit in a wide range without amplifying the small signal. A vibration detection signal input means is provided.

As described above, by providing the vibration detection signal input means for inputting a wide range to the arithmetic processing means without particularly amplifying the minute signal detected by the vibration detection means,
Calculation for obtaining a vibration isolation control signal using the maximum vibration level from the detected minimum vibration level becomes possible, and accurate vibration isolation control from the fine vibration level to the strong vibration level becomes possible.

According to a second aspect of the present invention, in the vibration damping apparatus according to the first aspect, the vibration detection signal input means includes a square root conversion means, and converts a vibration detection value detected by the vibration detection means into a square root conversion. And a non-linear input to the arithmetic processing means.

As described above, the vibration detection value detected by the vibration detecting means is square-root-converted, so that a wide range of detected vibration values from the detected minimum vibration level to the maximum vibration level can be input to the arithmetic processing means. .

According to a third aspect of the present invention, in the vibration damping apparatus according to the first aspect, a level ratio of a dynamic range of the vibration detection signal input means is 500 or more.

By setting the level ratio of the dynamic range of the vibration detection signal input means to 500 or more as described above, it is possible to cover from the normal vibration area of the active vibration isolator to the disturbance vibration area of the mechanical device mounted on the vibration isolator. Vibration control can be performed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The main body of the vibration isolator according to the present invention is shown in FIG.
And the description thereof is omitted. FIG.
FIG. 2 is a diagram showing a configuration of an anti-vibration control device of the active anti-vibration device according to the present invention. As shown in the figure, the anti-vibration control device 20 includes a vibration detection unit 21, a square root conversion unit 26, an A / D conversion unit 27, a position detection unit 22, an arithmetic processing unit 23,
This configuration includes an / A conversion unit 28 and a drive control unit 24.

The vibration detecting means 21 detects the vibration of the vibration isolation table 15 from the output of the vibration sensor 19, and inputs the detected vibration value to the square root conversion means 26. The square root conversion means 26 converts the vibration detection value into a square root, and the square root converted vibration value is A
The signal is A / D converted by the / D conversion means 27 and input to the arithmetic processing means 23. The position detecting means 22 detects a floating position of the vibration isolation table 15 from an output of a displacement sensor 25 (usually built in the electromagnetic actuator 18) for detecting a displacement of the vibration isolation table 15, and calculates a position detection signal. Input to processing means 23.

Although the vibration sensor 19 is mounted on the lower side of the vibration isolation table 15 as shown in FIG. 1, it may be mounted on the upper or side surface of the mechanical device 16 as shown in FIG. Thereby, the amplitude of the vibration sensor 19 is increased as compared with the case where the vibration sensor 19 is attached to the lower side of the vibration isolation table 15, and it is possible to detect a finer vibration. Further, the vibration sensor 19 may be directly attached to a device inside the mechanical device 16, for example, an electron microscope. When the stage is mounted on the stage on which the inspection object is mounted, the stage is the place where vibration is most desired to be suppressed, so that effective vibration control can be performed. Further, the vibration sensor 19 may be attached to a portion of the electron microscope where vibration is largest. This allows accurate detection without amplifying the minute vibration of the device itself. For example, it is attached at a point farthest away from the anti-vibration table 15 of the electron microscope in the vertical direction.

Further, the vibration sensor 19 can be used alone or in plural. When a plurality of vibration sensors 19 are used, when one of the vibration sensors 19 used breaks down, another vibration sensor 19 can be switched by a switch. In addition, the detection signals of the respective vibration sensors 19 can be averaged and processed.

As will be described in detail later, the arithmetic processing means 23
A power conversion means 23-1;
The vibration value is square-converted from the square root-converted vibration detection value input through the A / D conversion means 27 and returned to the original vibration detection value. The arithmetic processing means 23 calculates the vibration detection value
An operation necessary for anti-vibration control is performed based on the position detection signal of the position detection unit 22, D / A converted via the D / A conversion unit 28, and output to the drive control unit 24. The drive control unit 24 controls the drive of the electromagnetic actuator 18 to remove the vibration of the vibration isolation table 15.

As shown in FIG. 1 of the anti-vibration apparatus 10, a mechanical device 16 is mounted on the anti-vibration table, weighs about 1 t, and is heavy, so that most of the weight is reduced by the air spring 14 which is an elastic spring. Support and set the micro vibration level to the electromagnetic actuator 1
The vibration of the vibration damping table 15 is removed by the control by the control unit 8.
Since the voltage signal detected by the vibration sensor 19 is detected according to the vibration level, the detected vibration value detected by the vibration detecting means 21 is an electric signal having a positive or negative sign.
The square root conversion means 26 may be an absolute value conversion, or a square root conversion means for converting a single pole of a positive or negative sign into a square root. Further, since the vibration detection signal detected by the vibration sensor 19 includes unnecessary noise,
Is provided with an integrating circuit and the like for removing the unnecessary noise.

FIG. 6 is a graph showing the detected value of the vibration sensor of FIG. 3 and the square root of the detected value of the vibration sensor, wherein C is the detected value of the vibration sensor, and D is the square root of the detected value of the vibration sensor. Show. For example, if the minimum value of the detection value C of the vibration sensor is 0.0001 m / s ² and the maximum value is 0.5 m / s ² , the normalized value is 1: 5000. When this is square root transformed, the minimum value is 0.01 m / s ² and the maximum value is 0.707
1 m / s ² , which is normalized to 1: 70.71.
That is, 5000 of the dynamic range is suppressed to 70.71 by square root conversion.

As described above, the vibration detection value of the vibration sensor 19 detected by the vibration detecting means 21 is square-root-converted by the square-root converting means 26 and non-linearly input, thereby narrowing the ratio between the minimum value and the maximum value. To avoid restrictions on the use of operational amplifiers and the like that constitute the above.

The square root conversion means 26 has a dedicated analog I
Using C, the vibration detection value detected by the vibration detection means 21 is square-root transformed. Since the range from the minimum value to the maximum value of the square root transformed detection value of the vibration is narrower than the range from the minimum value to the maximum value of the detection value of the vibration input linearly as described above, without particularly increasing the signal amplification, The S / N ratio also becomes good.
For example, the signal range is wide, but the input range is narrow,
A / D conversion means 2 using a CPU as arithmetic processing means 23
When the input is performed by A / D conversion in step 7, it is convenient.

The square root converted vibration detection signal from the square root converter 26, which has been A / D converted by the A / D converter 27, cannot be used as it is as a control signal for the vibration isolation table. ) 23 or square conversion, or output to the D / A conversion means 28, and when performing analog conversion by the D / A conversion means 28, square conversion processing is performed by a dedicated analog IC and converted to linear input.

In the above embodiment, the air spring 14 is used as the elastic spring of the active vibration isolator, but most of the weight of the mechanical device 16 mounted on the vibration isolator 15 can be supported. Naturally, an elastic spring other than the air spring may be used.

[0026]

As described above, according to the invention described in each claim, the following excellent effects can be obtained.

According to the first aspect of the present invention, the vibration detection signal input means is provided for inputting a wide range to the arithmetic processing means without particularly amplifying the minute signal detected by the vibration detection means. The calculation for obtaining the vibration isolation control signal using the maximum vibration level from the minimum vibration level can be performed, and the vibration isolation control with high accuracy from the fine vibration level to the strong vibration level can be performed.

According to the second aspect of the present invention, since the vibration detection value detected by the vibration detection means is subjected to the square root conversion, the vibration detection value in a wide range from the minimum vibration level to the maximum vibration level detected is calculated. Can be input, and the calculation to obtain the anti-vibration control signal using the detected minimum vibration level to the maximum vibration level becomes possible, and accurate vibration control from the fine vibration level to the strong vibration level is possible. Becomes

According to the third aspect of the present invention, the level ratio of the dynamic range of the vibration detection signal input means is set to 500.
With the above, vibration isolation control covering from the normal vibration area of the active vibration isolation device to the disturbance vibration area of the mechanical device mounted on the vibration isolation table can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of an active vibration isolation device.

FIG. 2 is a diagram illustrating a configuration example of a conventional anti-vibration control device of an active anti-vibration device.

FIG. 3 is a diagram illustrating an example of a vibration level of a general vibration sensor and a detection value thereof.

FIG. 4 is a diagram showing input / output characteristics of a general operational amplifier.

FIG. 5 is a diagram illustrating a configuration example of a vibration isolation control device of the active vibration isolation device according to the present invention.

FIG. 6 is a graph showing a detection value of the vibration sensor of FIG. 3 and a square root of a detection value of the vibration sensor.

7 is a diagram showing a case where the mounting position of the vibration sensor of the active vibration isolator shown in FIG. 1 is changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vibration isolation device 11 Vibration isolation device installation place 12 Vibration isolation stand 13 Vibration isolation base 14 Air spring 15 Vibration isolation table 16 Machine device 18 Electromagnetic actuator 19 Vibration sensor 20 Vibration control device 21 Vibration detection means 22 Position detection means 23 Arithmetic processing unit 23-1 Square conversion unit 24 Drive control unit 25 Displacement sensor 26 Square root conversion unit 27 A / D conversion unit 28 D / A conversion unit

Claims (3)

[Claims] An elastic spring that floats and supports the anti-vibration table; displacement detection means for detecting a floating position of the anti-vibration table; vibration detection means for detecting vibration of the anti-vibration table; An arithmetic processing unit for performing an operation necessary for vibration isolation control based on a detection signal and a detection signal of the vibration detection unit; and an electromagnetic actuator for driving and controlling the vibration isolation table, wherein the electromagnetic actuator is driven by an output of the arithmetic processing unit. An active vibration isolator that drives and controls the vibration detection signal input means for inputting a wide range to the arithmetic processing means without particularly amplifying the small signal detected by the vibration detection means. Anti-vibration device. 2. The vibration isolator according to claim 1, wherein the vibration detection signal input means includes a square root conversion means, and performs a square root conversion of the vibration detection value detected by the vibration detection means, and performs the arithmetic processing. An active anti-vibration apparatus characterized in that a non-linear input is made to the means. 3. The active vibration isolator according to claim 1, wherein a level ratio of a dynamic range of said vibration detection signal input means is 500 or more.