JPH06200978A - Active vibration isolating device - Google Patents

Abstract

PURPOSE:To remarkably reduce the number of used sensors loaded on an object to be controlled, and simply construct the system constitution. CONSTITUTION:This active vibration isolating device is provided with a plurality of vibration sensors comprising sensors selected among an acceleration sensor 13, a speed sensor, and a displacement sensor 14, and in addition to those selected sensors, angular speed sensors 15a, 15b loaded on a controlled object 12 supported by air springs 11, and also provided with an actuator 16 which is driven by vibration signals a, b, c, d containing angular speed signals from the vibration sensors indicating the vibration of the controlled object, and injects controlling force whose direction is opposite to the direction of the vibration into the controlled object.

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 in which the number of sensors mounted on a controlled object is reduced, the system configuration is simplified and the system set is inexpensive. Involve

[0002]

2. Description of the Related Art Conventionally, a passive vibration isolator that uses an air spring and a dashpot to passively control a controlled object such as a surface plate on which precision equipment supported by the air spring is mounted is known. There is. Generally, such a passive vibration isolator is considered as a vertical one-axis (Z-axis) model as follows.

In FIG. 7, when there is a vibration of U = Asinωt on the installation surface which is the foundation or the floor, the equation of motion of this system can be expressed as follows.

[0004]

[Equation 1]

Note that z is the vertical position, m is the mass of the object to be controlled, k is the spring constant of the air spring, and c is the viscous damping constant of the dashpot. Laplace transform equation (1)

[0006]

[Equation 2]

[0007]

[Equation 3]

Where

[0009]

[Equation 4]

[0010]

[Equation 5]

[0011]

[0012]

[Equation 6]

From equation (2), the vibration transmissibility (absolute value of transfer function) τ is

[0014]

[Equation 7]

[0015] FIG. 8 is a graph showing the equation (3). As is clear from FIG. 8, when the damping constant c is small, the vibration isolation effect is large when the normalized frequency (ω / ω _n ) is 1 or more, but the resonance is large. Further, when c becomes large, the resonance approaches 0 dB, but the vibration isolation effect at the normalized frequency of 1 or more becomes small.

In order to eliminate the above conflicting matters, recently, an active or semi-active vibration isolator that actively controls an object to be controlled is being adopted in place of the passive vibration isolator. The active vibration isolator controls the parameters of the vibration isolation system from the outside, has no resonance, and realizes a vibration isolation table having a large vibration isolation effect even if the normalized frequency is 1 or more. This active vibration isolator detects the vibration by mounting a vibration sensor on the controlled object, injects energy from the actuator into the vibration isolator by this vibration signal, and uses the theory of linear feedback control or linear feedforward control. It is intended to positively enhance the vibration isolation or insulation effect of the vibration isolator.

At present, there are very few active vibration isolation devices on the market, but if they are classified by focusing on the actuators using them, they can be classified into the following two types. <Electrical type> A vibration sensor is mounted on the controlled object to detect vibration, and this vibration signal is injected into the vibration isolation device from an actuator driven by electricity such as VcM (voice coil motor) via a driver. However, the vibration isolation or isolation effect of the vibration isolator is positively enhanced (Japanese Patent Laid-Open No. 60-121340).

<Pneumatic type> A vibration sensor is mounted on the controlled object to detect vibration, and this vibration signal is converted into an electro-pneumatic signal by an electro-pneumatic converter, and the servo valve is opened and closed to turn air into an air spring. By injecting, the air spring is used as an actuator to positively enhance the vibration isolation or insulation effect of the vibration isolator (JP-A-2-21311).

FIG. 9 shows a vertical uniaxial model with active control. In this model, a vibration sensor SE is mounted on a controlled object having a mass of m to detect vibration,
This vibration signal is transmitted from a controller Co having an acceleration control gain G _m , a velocity control gain G _c , and a displacement control gain G _k to an electric actuator such as a VCM (voice coil motor) or a servo valve SV shown in the figure, a control air. Active control of feedback is performed by a pneumatic actuator using a spring.

The equation of motion of the system shown in FIG. 9 is

[0021]

[Equation 8]

Here, the feedback signal f represents the feedback control.

[0023]

[Equation 9]

Putting the equation (5),

[0025]

[Equation 10]

Further Laplace transform

[0027]

[Equation 11]

[0028]

[Equation 12]

Where

[0030]

[Equation 13]

[0031]

[Equation 14]

[0032]

[Equation 15]

The vibration transmissibility τ is

[0034]

[Equation 16]

[0035] FIG. 10 is obtained by showing the equation (8). As is apparent from FIG. 10, when the speed control gain G _c in the active vibration isolator is small, that is, when ζ is small, the transmissibility is the same as the damping constant c = 1 of the passive vibration isolator. However, when G _c becomes large, the transmissibility becomes 0 dB or less, and even when the normalized frequency is 1 or less, the vibration isolation effect can be made larger than that of the passive vibration isolator.

[0036]

In this active vibration isolator, considering only one axis in the vertical direction (Z axis) shown in FIG. 9 in order to simplify the explanation, the configuration is as shown in FIG.
As shown in FIG. 1, a controlled object such as a surface plate is supported by air springs AM at four corners, and the controlled object is equipped with an acceleration sensor, a displacement sensor, and a servo valve in each air spring AM section. Each block is connected to the controller Co via a connector box. The control system is shown in FIG. In FIG. 12, 3
The gains G _m , G _c and G _k (FIG. 9) of the individual amplifiers are equal to the gains G _m , G _c and G _k of Equation 6, respectively. Also, the displacement z-
u is the acceleration obtained from the displacement sensor

[0037]

[Outer 1]

Is obtained from the acceleration sensor, and

[0039]

[Outside 2]

Is obtained by integrating the acceleration signal from the acceleration sensor with an integrator. These displacement signals, acceleration signals,
The speed signal is amplified by an amplifier having gains G _m , G _c , and G _k , compared with a reference voltage by an adder, and a servo valve is opened / closed to supply or exhaust air to a control air spring to control an object to be controlled. It is intended to positively enhance the vibration isolation or insulation effect of.

However, as is apparent from FIG. 11, even if the control is performed only on one axis (Z axis) in the vertical direction, the control system has four channels (CH) in consideration of the inclination of the controlled object such as the surface plate. You will need it. However,
These displacement sensors and acceleration sensors are extremely expensive and have a drawback that they hinder the popularization of active vibration isolation devices.

[0042]

[Object] The present invention has been made in view of the above drawbacks, and an object thereof is to significantly reduce the number of sensors mounted on a controlled object, simplify the system configuration, and make the system set inexpensive. An active vibration isolator is provided.

[0043]

In order to achieve this object, an active vibration isolator according to the present invention comprises an acceleration sensor, a speed sensor, and a control object supported by an air spring.
It is equipped with a plurality of vibration sensors consisting of a displacement sensor and an angular velocity sensor, and is driven by a vibration signal including the angular velocity signal from the vibration sensor that indicates the vibration of the controlled object And an actuator for injecting a direction control force.

[0044]

With regard to the operation model of the active vibration isolator constructed as described above, assuming that the arbitrary actual vibration in the XX'-axis cross section is the vibration of the controlled object from the reference position to the fluctuation position, this vibration Is X-axis direction vibration, rotational vibration, Z
It can be broken down into axial vibrations. Here, since the X-axis direction vibration is extremely small, if omitted, this arbitrary actual vibration can be detected by the acceleration sensor, the displacement sensor, and the angular velocity sensor located at the center of the controlled object. The same thing can be said on the YY 'axis section. That is, with two angular velocity sensors, one displacement sensor, and one acceleration sensor, it is possible to detect vibration of an arbitrary cross section on a control target such as a surface plate. The actuator is driven by the vibration signal including the angular velocity signals from these sensors, and the control force in the direction opposite to the vibration is injected into the controlled object. Therefore, by using the angular velocity sensor as a sensor, the number of sensors mounted on the controlled object is greatly reduced, the system configuration is simplified, the system set is inexpensive, and the vibration isolation performance of the vibration isolator is reduced. Is greatly improved.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of an active vibration isolator according to the present invention will be described below with reference to the drawings. For the sake of convenience of explanation, an active vibration isolator applied only to one axis (Z axis) in the vertical direction will be described. In FIG. 1, this vertical uniaxial (Z-axis) active vibration isolator includes a vibration isolation table or a control target 12 supported by an air spring 11 on an installation surface 10 which is a foundation or a floor. There is. The controlled object 12 includes an acceleration sensor 13, a displacement sensor 14,
A plurality of vibration sensors including an angular velocity sensor 15a in the XX 'axis direction and an angular velocity sensor 15b in the YY' axis direction are mounted.

As shown in FIG. 2, one set of the acceleration sensor 13 and the displacement sensor 14 is provided in the central portion of the controlled object 12, and the angular velocity sensor 15a and the angular velocity sensor 15b are also provided in the central portion of the controlled object 12 XX '. They are mounted in the axial direction and the YY 'axial direction, respectively. As the acceleration sensor 13,
For example, a known acceleration sensor or speed sensor can be adopted. When a speed sensor is used as the acceleration sensor 13, the acceleration signal is obtained by differentiating the speed once. When an acceleration sensor is used as the acceleration sensor 13, the velocity signal is obtained by integrating the acceleration once.

The displacement sensor 14 detects the relative displacement in the vertical direction between the controlled object 12 and the installation surface 10 of the air spring 11. A non-contact type sensor can be used as the displacement sensor 14, and for example, an eddy current element, a differential transformer, an LED, a laser element, or the like can be adopted. As the angular velocity sensor 15a and the angular velocity sensor 15b, a gyro such as a known vibration gyro, optical fiber gyro, or mechanical gyro can be adopted.

Here, the controlled object 12 includes not only a table to be isolated such as a surface plate but also precision equipment such as an electron microscope, an IC, and a stepper which is a manufacturing device of LSI mounted on the table. In this case, the acceleration sensor 13, the displacement sensor 14, the angular velocity sensor 15a, the angular velocity sensor 15
b may be mounted on such precision equipment itself. Also,
This active vibration isolator is driven via the controller Co by the vibration signals a, b, c, d including the angular velocity signals from these vibration sensors indicating the vibration of the controlled object 12, and the controlled object 12 receives the vibration. An actuator 16 for injecting a reverse control force is provided.

In the illustrated example, the actuator 16 supplies and exhausts air to and from the air spring 11 that supports the controlled object 12 and the controller Co, and applies a control force to the controlled object 12 in the direction opposite to its vibration. Servo valve 17 for injection. This servo valve 17
The air compressed by an air pressure source such as a compressor (not shown) is applied to. As the servo valve 17, an electro-pneumatic proportional valve, a pneumatic analog valve, or the like can be adopted. As the actuator 16, in addition to the air spring,
A pneumatic actuator such as a pneumatic cylinder is adopted, and an electric actuator such as a VCM (voice coil motor) that is driven by electricity can also be used.

As shown in FIG. 2, the controlled object 12 is supported by one air spring (AM) 11 at each of the four corners, and one servo valve 17 corresponds to each air spring (AM) 11. Is provided. Regarding the operation model of the active vibration isolator shown in FIG. 2, in order to briefly explain the operation, an arbitrary actual vibration in the XX′-axis cross section of FIG. 2 is controlled by the controlled object 12 as shown in FIG. Reference position 1
Assuming that the vibration has occurred from 2a to the fluctuation position 12b,
This vibration is X-axis direction vibration (Fig. 3 (b)) rotational vibration (Fig. 3).
(C)) and z-direction vibration (FIG. 3 (d)). Here, since the X-axis direction vibration is extremely small, if omitted, this arbitrary actual vibration can be detected by the acceleration sensor, the displacement sensor, and the angular velocity sensor located in the center of FIG. The same thing can be said on the YY 'axis section. That is, two angular velocity sensors, one displacement sensor, and one acceleration sensor can detect the vibration of an arbitrary cross section on the controlled object 12 such as a surface plate.

Next, a control system including the controller Co constructed with respect to the active vibration isolator constructed as described above will be described with reference to FIG. 3. The acceleration sensor 13 indicating the vibration of the controlled object 12 and the displacement Sensor 1
4, XX′-axis angular velocity sensor 15a, YY ′
Of the axial angular velocity sensor 15b, the vibration signal b from the displacement sensor 14 is amplified by the amplifier 32 having a gain G _k as the displacement z-u, and the vibration signal a from the acceleration sensor 13 has a DC component in the DC cut filter 20. Cut,
High-frequency components are cut by the low-pass filter 26 via the branch point 23, and the acceleration

[0052]

[Outside 3]

Is amplified by an amplifier 33 having a gain G _m, and is integrated by an integrator 27 via the branch point 23 to obtain the speed.

[0054]

[Outside 4]

Is amplified by an amplifier 34 having a gain G _c . Signals from these amplifiers 32, 33 and 34 are added by the summing point _{41 G m z + G c z} + G k (z-u)
Is output to the addition point 44. The DC component of the vibration signal c from the angular velocity sensor 15a in the X-X'-axis direction is cut by the DC cut filter 21 and is differentiated by the differentiator 28 via the branch point 24 to obtain the angular acceleration.

[0056]

[Outside 5]

Is amplified by an amplifier 35 having a gain m, is integrated by an integrator 29 via a branch point 24, is amplified by an amplifier 36 having a gain m as an angle ∫ω _x dt, and is further passed through a branch point 24 to an angular velocity ω. gain m as _x
Is amplified by the amplifier 37 having These amplifiers 3
The signals from 5, 36 and 37 are added at the addition point 42 and mω
It is output to the addition point 44 as _x + mω _x + m∫ω _x dt.

The DC component of the vibration signal d from the angular velocity sensor 15b in the Y-Y'-axis direction is cut by the DC cut filter 22 and is differentiated by the differentiator 30 via the branch point 25 to obtain the angular acceleration.

[0059]

[Outside 6]

Is amplified by an amplifier 38 having a gain n, is integrated by an integrator 31 via a branch point 25, is amplified by an amplifier 39 having a gain n as an angle ∫ω _Y dt, and is further passed through a branch point 25 to an angular velocity ω. Gain n as _Y
Is amplified by an amplifier 40 having These amplifiers 3
The signals from 8, 39 and 40 are added at the addition point 43 and nω
_Y + nω _Y + n∫ω _Y dt is output to the addition point 44.

By the way, the feedback signal f'corresponding to the feedback signal f of the prior art (equation (6)) is as follows.

[0062]

[Equation 17]

In the equation (10), since the amplitude of vibration is extremely small, if all the rotational terms are approximated by only the z-axis direction component like z, z, (z-u),

[0064]

[Equation 18]

Therefore, the equation (10) can be approximated as follows.

[0066]

[Formula 19]

Therefore, the equation becomes the same as the equation (6) and becomes equal to the feedback signal f of the prior art. That is, the control system of the present system exhibits the same operation as in the prior art. In this way, the feedback signal f ′ of G _m 'z + G _c ' z + G _R 'is output from the addition point 44 of the controller Co to drive the servo valve 17 of the actuator 16 to supply or exhaust air to the air spring 11. By doing so, the control force in the direction opposite to the vibration is injected into the controlled object 12.

In this way, the controlled object 12 → acceleration sensor 13, displacement sensor 14, angular velocity sensor 15a in the XX ′ axis direction, angular velocity sensor 15b in the YY ′ axis direction →
A feedback loop is formed from the controller Co to the servo valve 17 of the actuator 16 to the controlled object 12. The control system of this feedback loop has channels 1CH to 4CH for the air spring 11.
(Fig. 2).

In the active vibration isolator shown in FIG. 2, the controller shown in FIG. 4 was constructed, and as a result of the experiment, the transfer function shown in FIG. 5 was obtained. For reference, the transfer function obtained as a result of applying the system according to the above embodiment to the passive vibration isolator is shown in FIG. As is apparent from both figures, the active vibration isolator according to the present invention has a significantly improved vibration isolation compared to the passive vibration isolator.

[0070]

As is apparent from the above description, according to the active vibration isolator of the present invention, an acceleration sensor, a speed sensor,
It is equipped with a plurality of vibration sensors consisting of a displacement sensor and an angular velocity sensor, and is driven by a vibration signal including the angular velocity signal from the vibration sensor that indicates the vibration of the controlled object By providing the actuator for injecting the control force of the direction, the number of sensors mounted on the controlled object can be significantly reduced, the system configuration can be simplified, and the system set can be inexpensive.

[Brief description of drawings]

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

FIG. 2 is a layout view of an air spring, a sensor, and an actuator used for a controlled object of the active vibration isolator according to the present invention.

3 (a), (b), (c) and (d) are operation explanatory views of a controlled object of the active vibration isolator according to the present invention.

FIG. 4 is a block diagram showing a control system constructed for an active vibration isolator according to the present invention.

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

FIG. 6 is a graph showing frequency-vibration transfer function characteristics obtained by a conventional passive vibration isolation device.

FIG. 7 is an explanatory diagram of a conventional passive vibration isolator.

FIG. 8 is a graph showing frequency-vibration transfer function characteristics obtained by a conventional passive vibration isolation device.

FIG. 9 is an explanatory diagram of a conventional active vibration isolator.

FIG. 10 is a graph showing frequency-vibration transfer function characteristics obtained by a conventional active vibration isolator.

FIG. 11 is a layout view of an air spring, a sensor, and an actuator used as a control target object of a conventional active vibration isolator.

FIG. 12 is a block diagram showing a control system constructed for a conventional active vibration isolator.

[Explanation of symbols]

 11 ... Air spring 12 ... Controlled object 13 ... Acceleration sensor 14 ... Displacement sensor 15a, 15b ... Angular velocity sensor (vibration sensor) 16 ... Actuator (17 ... Servo valve) a, b, c, d ... Vibration signal including angular velocity signal

Claims (1)

[Claims] 1. A controlled object supported by an air spring,
A plurality of vibration sensors including an acceleration sensor, a velocity sensor, and a displacement sensor, and an angular velocity sensor are mounted, and driven by a vibration signal including an angular velocity signal from the vibration sensor, which indicates the vibration of the controlled object. An active vibration isolator, comprising: an actuator for injecting a control force in a direction opposite to the vibration to the controlled object.