JP3292505B2 - Active vibration isolator - Google Patents

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, and more particularly to an active vibration isolator capable of improving horizontal vibration isolation performance by injecting a horizontal control force into an object to be controlled.

[0002]

2. Description of the Related Art Conventionally, there has been known a passive vibration isolator that passively controls a control target such as a surface plate on which a precision device supported by an air spring is mounted, using an air spring and a dashpot. .

Recently, an active or semi-active vibration isolator for actively controlling an object to be controlled has been adopted in place of the passive vibration isolator.

In this active vibration isolator, a vibration sensor is mounted on an object to be controlled to detect vibration, energy is injected from the actuator into the vibration isolator by the vibration signal, and the theory of linear feedback control or linear feedforward control is applied. Is used to positively increase the vibration isolation or insulation effect of the vibration isolator.

At present, there are very few active vibration isolators on the market, but when they are classified by focusing on the actuators using them, they are classified into the following two types.

<Electric type> A vibration sensor is mounted on the control object to detect vibration, and the vibration signal is transmitted to a VCM (voice coil coil) via a driver.
Energy is injected into the vibration isolator from an actuator driven by electricity such as a motor) to positively enhance the vibration isolation or insulation effect of the vibration isolator (Japanese Patent Laid-Open No. 60-121340).

<Pneumatic type> A vibration sensor is mounted on the object to be controlled to detect vibration, the vibration signal is converted into an electropneumatic signal by an electropneumatic converter, a servo valve is opened and closed, and air is converted to an air spring. By injecting the air, an air spring is used as an actuator to positively enhance the vibration isolation or insulation effect of the vibration isolator (Japanese Patent Laid-Open No. 2-21311).

In this pneumatic active vibration isolator, a pair of air tanks are connected to each other via an orifice pipe, and only one of the air tanks is connected to a compressor via a servo valve. By outputting a control signal from the control device to the servo valve according to a signal from the attached horizontal vibration sensor,
While the horizontal displacement of the device mounting table is elastically supported in the horizontal direction by air springs connected to each of the pair of air tanks to relieve the vibration, the two air springs are used when the device mounting table vibrates. The actuator expands or contracts to apply a dynamic force to the apparatus mounting table, and displaces the apparatus mounting table in the horizontal direction so as to maintain the apparatus mounting table in an absolute horizontal stationary state.

[0009]

However, in this pneumatic active vibration isolator, it is cumbersome to separately assemble the pair of air tanks and the air springs, and the installation space becomes large, and the pair of air tanks and air springs are increased. Since the tanks are connected to each other through the orifice pipe, a delay occurs between the air spring vibrating systems, and the support balance of the entire vibrating system is lost. Therefore, there is a problem that the horizontal vibration insulating performance is reduced.

[0010]

[Purpose] The present invention has been made in view of the above-mentioned difficulties, and its purpose is to easily install pneumatic means used as an actuator, to reduce the installation space, and to balance the entire vibration system. It is an object of the present invention to provide an active vibration isolator that can support well and improve horizontal vibration isolation performance.

[0011]

In order to achieve this object, an active vibration isolator according to the present invention is mounted on a control object supported by an air spring and detects horizontal vibration to detect horizontal vibration. A horizontal vibration sensor that outputs a signal, and a horizontal relative displacement between the control object and the installation surface of the air spring mounted on one of the control object and the air spring are detected and a horizontal relative displacement signal is output. A horizontal displacement sensor, an adder for adding the vibration signal and the relative displacement signal, and a first electropneumatic analog valve to which an output from the adder is input and compressed air is applied from a pneumatic source. The signal from the second electro-pneumatic analog valve to which the output from the adder is input via the signal inverter and to which compressed air is applied from the pneumatic source, and from the first electro-pneumatic analog valve Driven and controlled object A first horizontal pneumatic actuator for injecting one horizontal control force and a second horizontal pneumatic actuator driven by a signal from the second electropneumatic analog valve to inject the other horizontal control force into the control target The horizontal vibration sensor and the adder are horizontally arranged between the horizontal vibration sensor and the adder through a high-pass filter that cuts a DC component and improves a temperature characteristic because the zero point drifts due to the temperature of the horizontal vibration sensor. An amplifier that generates an acceleration signal amplified from the directional vibration signal, a low-pass filter that cuts high-frequency components to prevent oscillation, an integrator that generates a speed signal from the horizontal vibration signal, and amplifies the speed signal from the integrator Parallel circuit with a low-pass filter that cuts high-frequency components and prevents oscillation, intervenes between the horizontal displacement sensor and the adder. Performs a zero point adjustment so as to generate a ± voltage around a zero point of a voltage of 0 to + several v generated by a horizontal displacement sensor and a preamplifier for amplifying a horizontal relative displacement signal. A series circuit of a subtractor and an amplifier for amplifying the horizontal relative displacement signal from the subtractor is interposed.

[0012]

According to the active vibration isolator constructed as described above, when the control object is displaced in the horizontal direction at the horizontal stationary reference point of the control object, the internal pressure of the first actuator increases, and The control force in the horizontal direction of the first actuator acts in the horizontal opposite direction, the vibration sensor detects the horizontal displacement of the control target, and the vibration signal is applied to the analog valve, and the first actuator is driven by the analog valve. As a result, the control force in the horizontal direction is injected into the control object, the internal pressure rises, and the control force acts in the horizontal opposite direction, and attempts to return the control object to the horizontal opposite direction. At that time, the internal pressure of the second actuator is reduced, and assists the movement of the first actuator to return to the control object in the horizontal opposite direction. In this way, the horizontal vibration isolation performance of the vibration isolation device is improved overall.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the active vibration isolator according to the present invention will be described below with reference to the drawings.

In FIG. 1, the active vibration isolator includes an air spring 11 on a mounting surface 10 which is a foundation or floor.
A table 12 or an object to be controlled 12 is provided.

The control object 12 has a horizontal vibration sensor 13 which detects horizontal vibration and outputs a horizontal vibration signal S1.

As the horizontal vibration sensor 13, for example, a known acceleration sensor or speed sensor can be adopted. When a speed sensor is used as the horizontal vibration sensor 13, the acceleration signal is obtained by differentiating the speed once. Further, when an acceleration sensor is used as the horizontal vibration sensor 13, the speed signal is obtained by integrating the acceleration once. Here, the controlled object 12 includes not only a vibration-isolated table such as a surface plate, but also precision equipment such as an electron microscope mounted on the table and a stepper which is an IC and LSI manufacturing apparatus. In this case, the horizontal vibration sensor 13 may be mounted on such precision equipment itself.

The air spring 11 used in the active vibration isolator has a piston 11b fixed to an additional tank (not shown) as shown in FIG. 2, and a bellofram 11a covers the piston 11b to cover the chamber. 11c, and the control target 12 is supported by the chamber 11c. According to the air spring 11, the restoring force F of the portion of the chamber 11c through eccentric e against the piston 11b of the control object 12 is ^{F = (π 2/8)} P · D P · e ( where, P: the chamber 11c pressure, D _P: given diameter of the piston 11b), a force that returns the displaced original acts by the restoring force of the air spring 11 in response to horizontal displacement of the controlled object 12.

The active vibration isolator is driven by a horizontal vibration signal S1 to inject first and second horizontal control forces FA and FB into the control object 12 in opposite directions. Pneumatic actuators 15a, 15b
And The first and second horizontal pneumatic actuators 15a and 15b are provided with an operation piece 1 provided on the control object 12.
It is provided between 2a and the support pieces 10a and 10b provided on the installation surface 10, respectively, and is opposed to the operation piece 12a. As the horizontal pneumatic actuator 15, an air spring, a pneumatic cylinder or the like is employed.

Further, a vibration signal S from the vibration sensor 13
A control circuit C for processing 1 to generate a control signal, a pneumatic analog valve drive circuit Da for generating a drive signal based on a control signal from the control circuit C, and a pneumatic analog valve drive circuit Db via a signal inverter 28; Pneumatic analog valve drive circuit Da,
Db for supplying and discharging air to the first and second horizontal pneumatic actuators 15a and 15b according to a drive signal from Db.
Second analog pneumatic valves 17a, 17b are provided. As the first and second analog valves 17a and 17b, servo valves and electropneumatic proportional valves can be employed. This first,
Air compressed from a pneumatic source such as a compressor (not shown) is applied to the second electropneumatic analog valves 17a and 17b.

In this embodiment, an acceleration sensor is used as the vibration sensor 13. As shown in FIG. 3, an acceleration vibration signal S1 from the vibration sensor 13 is supplied to a control circuit C,
The high-pass filter 18 of the pneumatic analog valve drive circuits Da and Db is input to the high-pass filter 18, and the output of the high-pass filter 18 is connected to the amplifier 19 and the amplifier 21 via the integrator 20. This high-pass filter 18 is used to cut the DC component and improve the temperature characteristics because the zero point of the acceleration sensor drifts depending on the temperature. The integrator 20 is used to generate a speed signal from the acceleration vibration signal S1. The amplified acceleration signal and speed signal from the amplifiers 19 and 21 are input to low-pass filters 22 and 23, respectively. These low-pass filters 22 and 23 are used to cut high-frequency components and prevent oscillation.

On the other hand, as shown in FIG. 1, the non-contact horizontal direction between the control object 12 and the installation surface 10 of the air spring 11 detects the horizontal relative displacement and outputs a horizontal relative displacement signal S2. The displacement sensor 14 is mounted on either the control target 12 or the air spring 11 (mounted on the air spring 11 in the illustrated example). This horizontal displacement sensor 14
For example, eddy current element, differential transformer, LE
D, a laser element or the like can be adopted. As shown in FIG. 3, the horizontal relative displacement signal S2 is input to a preamplifier 24, and the preamplifier 24
It is connected to the. Since the non-contact horizontal displacement sensor 14 generally generates a voltage of 0 to several volts, the subtracter 25 is used to adjust the zero point so that a ± voltage is generated at the zero point. .

As shown in FIG. 3, the low-pass filter 2
Acceleration signal, velocity signal and amplifier 26 from 2, 23
Is input to the adder 27 and the adder 2
The output of 7 is connected to a first pneumatic analog valve 17a and to a second pneumatic analog valve 17b via a signal inverter 28. First and second electropneumatic analog valves 17a, 1
7b are applied to first and second pneumatic actuators 15a and 15b in the horizontal direction, respectively, and the first and second pneumatic actuators 15a and 15b are driven to control the object 12 to be controlled. Are injected with horizontal control forces FA and FB opposite to each other.

FIG. 4 shows the arrangement of each component in the active vibration isolator described above. Air springs 11 that support the control target 12 in the vertical direction are installed at each corner of the control target 12. Since the horizontal direction for detecting vibration is two-dimensional, the horizontal vibration sensor 13 is provided at the center of the control target 12 in the X and Y directions. Horizontal displacement sensors 14 are also provided in the X and Y directions, respectively, facing the control target 12. The first and second pneumatic actuators 15a and 15b in the horizontal direction are provided in the X and Y directions, respectively. First and second electropneumatic analog valves 17a, 17b
Is installed near the first and second pneumatic actuators 15a and 15b.

Thus, control systems from the horizontal vibration sensor 13 and the horizontal displacement sensor 14 to the first and second pneumatic actuators 15a and 15b are also provided in the X and Y directions, respectively.

The vertical vibration isolation control of the control object 12 is performed by using a vertical vibration sensor 30, a vertical displacement sensor 31, and an electropneumatic analog valve 32 as in the horizontal control system described above. The vertical level can be controlled by a mechanical valve (JP-A-57-732).
No. 48), the internal pressure of the air spring 11 can be controlled.

In the active vibration isolator constructed as shown in FIGS. 1 to 3, a mounting surface 1 which is a foundation or a floor is provided.
A horizontal vibration sensor 13 which is an acceleration sensor mounted on a control target 12 supported by an air spring 11
Thus, the horizontal vibration of the control target 12 is detected.
The detected horizontal vibration signal S1 is transmitted to the control circuit C,
The signal is input to the high-pass filter 18 of the pneumatic analog valve drive circuits Da and Db. The high-pass filter 18 cuts the DC component because the zero point drifts due to the temperature of the acceleration sensor, and improves the temperature characteristics. High Pass Filter 18
Is input to an integrator 20 to generate a speed signal, and an amplified acceleration signal and a speed signal are obtained from the amplifiers 19 and 21, respectively. Amplifier 19 and Amplifier 21
The amplified acceleration signal and speed signal are input to low-pass filters 22 and 23, respectively, to cut high-frequency components and prevent oscillation.

On the other hand, the non-contact displacement sensor 14 detects a horizontal relative displacement between the control object 12 and the installation surface 10 of the air spring 11, and outputs a horizontal relative displacement signal S2. The horizontal relative displacement signal S2 is input to a preamplifier 24, and the output of the preamplifier 24 is input to a subtractor 25. Generally, the non-contact displacement sensor 14
Since a voltage of + several volts is generated, zero point adjustment is performed so as to generate ± voltage at the zero point. The output of the subtractor 25 is input to the amplifier 26. Low-pass filter 22,
The acceleration signal, the speed signal and the relative displacement signal from the amplifier 26 are input to an adder 27. The output of the adder 27 is a first pneumatic analog valve 17a and a signal inverter 2
8 are applied to the second pneumatic analog valve 17b. First and second pneumatic analog valves 17a, 17b
Is opened and closed, and air is sucked and exhausted by the first and second horizontal pneumatic actuators 15a and 15b, so that the control object 12 exerts horizontal control forces FA and FB in mutually opposite directions.
Is injected.

The horizontal force F of the air spring 11 at the horizontal stationary reference point on the control object 12 (FIG. 2)
Is F = 0, and the horizontal control forces FA, FB of the first and second horizontal pneumatic actuators 15a, 15b are:
FA = FB.

Now, when the control object 12 is displaced rightward in FIG. 1, the air spring 11 moves according to its eccentricity e to the chamber 1 constituted by the bellofram 11a (FIG. 2).
When the control object 12 is displaced rightward, the internal pressure of the second pneumatic actuator 15b increases, and the second pneumatic actuator 1
The horizontal control force FA of 5b acts leftward, the vibration sensor 13 detects the rightward displacement of the control object 12, and the acceleration vibration signal S1 is transmitted to the control circuit C and the pneumatic analog valve drive circuit D. The DC component is input to the high-pass filter 18 to cut the DC component and improve the temperature characteristics so that the zero point does not drift due to the temperature. This is input to the integrator 20 to generate a speed signal. A signal and a speed signal are obtained, respectively, and input to the low-pass filters 22 and 23. The high-frequency components are cut to prevent oscillation. These acceleration signal and speed signal are input to the adder 27, and the output of the adder 27 is The voltage is applied to the first electropneumatic analog valve 17a, the valve is opened, and the first
Air is sucked into the pneumatic actuator 15a, and the internal pressure of the first pneumatic actuator 15a in the horizontal direction increases.
A is injected and the control force FA acts leftward, and the control object 1
2 moves to the left.

On the other hand, the output of the adder 27 is the signal inverter 2
The second horizontal pneumatic actuator 15b is closed by applying a voltage to the second electropneumatic analog valve 17b through the second horizontal pneumatic actuator 15b, and air is exhausted from the second horizontal pneumatic actuator 15b. As the internal pressure of 15b decreases, the control force FB in the horizontal direction decreases, which helps the control object 12 to move leftward with the control force FA.

The non-contact displacement sensor 14 also detects the rightward displacement of the controlled object 12 and outputs a horizontal relative displacement signal S.
Outputs 2. The horizontal relative displacement signal S2 is input to a preamplifier 24, and the output of the preamplifier 24 is input to a subtractor 25. The subtracter 25 is generally a non-contact displacement sensor 1
No. 4 generates a voltage of 0 to several volts, so that the zero point is adjusted so as to generate a voltage of ± from the zero point. The output of the subtractor 25 is input to the amplifier 26. The relative displacement signal from the amplifier 26 is input to the adder 27. Adder 27
Is applied to the first and second horizontal pneumatic actuators 15a and 15b as described above, and the control target 1
2, the control force FA in the horizontal direction is injected into the control force FA described above, and the control object 12 attempts to displace to the left. The control system from the non-contact displacement sensor 14 to the amplifier 26 can be omitted depending on the application.

When the control object 12 is displaced leftward beyond the horizontal stationary reference point, the first and second horizontal pneumatic actuators 15a, 15
The control forces FA and FB in the horizontal direction b act in opposite directions.

FIG. 5A shows the frequency-horizontal vibration transfer function characteristics obtained by the conventional vibration isolator, and for comparison, the frequency-horizontal direction transfer function obtained by the active vibration isolator according to the present invention. FIG. 5B shows the vibration transfer function characteristics. In each case, the vertical level was controlled by controlling the internal pressure of an air spring by a mechanical valve (Japanese Patent Laid-Open No. 57-73248). FIG.
As is clear from (a) and (b), according to the active vibration isolator of the present invention, horizontal vibration isolation is greatly improved at low frequencies.

In the above example, the control method uses the three signals of the absolute acceleration, the absolute speed, and the relative displacement as the feedback control signal. However, the displacement signal is changed according to the intended use for obtaining the desired vibration isolation effect. Absolute displacement may be used, or control may be performed using two signals selected from the group consisting of displacement and velocity or displacement and acceleration.

In the above example, one or both of the high-pass filter and the low-pass filter can be omitted depending on the situation. Further, the preamplifier provided in the non-contact displacement sensor in the above example can be omitted.

[0036]

As is clear from the above description, according to the active vibration isolator of the present invention, it is easy to assemble the actuator, the installation space is reduced, and the entire vibration system is balanced. It can be supported to improve horizontal vibration isolation performance.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an active vibration isolator according to an embodiment of the present invention.

FIG. 2 is an explanatory view of an air spring used in the active vibration isolator according to the present invention.

FIG. 3 is a block diagram showing a horizontal control system of the active vibration isolator according to the present invention.

FIG. 4 is a diagram showing an arrangement of each component in the active vibration isolator according to the present invention.

FIG. 5A is a graph showing frequency-horizontal vibration transfer function characteristics obtained by a conventional vibration isolator.
FIG. 5B is a graph showing frequency-horizontal vibration transfer function characteristics obtained by the active vibration isolator according to the present invention.

[Explanation of symbols]

 Reference Signs List 10: Installation surface of air spring 11: Air spring 12: Control object 13: Horizontal vibration sensor 14: Horizontal displacement sensor 15a: First horizontal pneumatic actuator 15b: No. 2 horizontal pneumatic actuators 17a ... first electropneumatic analog valve 17b ... second electropneumatic analog valve 18 ... high pass filter 19 ... amplifier 20 ... integrator 21 ... amplifier 22 ... Low-pass filter 23 Low-pass filter 24 Preamplifier 25 Subtractor 26 Amplifier 27 Adder 28 Signal inverter S1 Horizontal vibration signal S2 Horizontal relative displacement signal FA: Control force in one horizontal direction FB: Control force in the other horizontal direction

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16F 15/02-15/08

Claims (1)

(57) [Claims] A control pair supported by an air spring (11).
Equipped with an elephant (12) to detect horizontal vibration
Horizontal vibration sensor that outputs a vibration signal (S1) in the horizontal direction
(13) and any one of the control object and the air spring
The mounting surface of the control object and the air spring (1
0) to detect the horizontal relative displacement during the horizontal
Horizontal displacement sensor (1) that outputs displacement signal (S2)
4) and adding the vibration signal and the relative displacement signal.
And an output from the adder (27).
First electricity to which compressed air is applied from a pneumatic source
The output from the pneumatic analog valve (17a) and the adder is
The pressure input from the pneumatic source through the signal inverter (28)
Second electropneumatic analog to which compressed air is applied
A valve (17b) and said first electropneumatic analog valve
Driven in response to a signal,
First horizontal pneumatic actuator for injecting control force (FA)
Eta (15a) and the second electropneumatic analog valve
Driven by these signals, and the other
Second horizontal pneumatic actuator for injecting a heading control force (FB)
A tutor (15b), wherein the horizontal vibration sensor and the adder are disposed between the horizontal vibration sensor and the adder.
Horizontal vibration sensor drifts zero point due to temperature
The DC component to improve the temperature characteristics
The vibration signal in the horizontal direction is transmitted through a filter (18).
Amplifier (19) that generates an amplified acceleration signal from the
Low-pass filter that cuts frequency components and prevents oscillation
(22) and generating a speed signal from the horizontal vibration signal.
An integrator (20) for increasing the speed signal from the integrator
Amplifier (21) that cuts high frequency components to prevent oscillation
Parallel circuit with the low-pass filter (23)
Between the horizontal displacement sensor and the adder,
Preamplifier for amplifying horizontal relative displacement signal (24)
And 0 to + several v generated by the horizontal displacement sensor.
Zero point so that ± voltage is generated at the zero point of pressure
A subtractor (25) for adjusting, and a horizontal
In series with an amplifier ( 26) that amplifies the relative displacement signal in the direction
An active vibration isolator characterized by having a circuit interposed .