JP2005315298A - Active type vibration isolating device and active type vibration isolating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active type vibration isolating device to work while the behavior of the object mounted likely influencing the vibration isolating performance is taken into consideration. <P>SOLUTION: The active type vibration isolating device 1 to make vibratory isolation of the object mounted 2 is equipped with a table 3 to admit placing of the object 2 and having an elastic vibration mode within the frequency range to be vibratory isolated, a plurality of actuators 11 to drive the table 3, table sensors 13 and 14 to measure the conditional amount of the table 3, and a control part 9 to control the actuators 13 and 14 using the output of the sensors 13 and 14 and on the basis of the conditional equation with the elastic vibration mode of the table 3 taken into consideration, wherein the device further has a sensor 10 for placed object to measure the conditional amount of the object 2, while the control part 9 controls the actuators 11 using the output of the object sensor 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an active vibration isolation device and an active vibration isolation method. More specifically, with regard to active control in the vertical and horizontal three-dimensional directions of a large, lightweight, or thin vibration isolation table, active vibration isolation that takes into account the effects when a load is placed on the vibration isolation table The present invention relates to an apparatus and an active vibration isolation method.

  Conventionally, in mechanical devices such as optical measuring instruments and ultra-precision processing machines, measurement errors and processing accuracy are reduced due to environmental vibration, so these are called vibration isolating machines and methods of vibration isolation or vibration isolation have been taken. I came.

The methods are roughly classified into passive vibration isolation and active vibration isolation.
Passive vibration isolation is a method of reducing vibration transmitted from the ground on a table by supporting a heavy vibration isolation table from a base surface by a support spring and a damper. This method is simple and inexpensive, but the vibration isolation effect does not occur unless it exceeds 1.5 times the natural frequency determined by the mass of the vibration isolation table and the spring constant of the support spring. There is a limit to the vibration, and if the vibration control performance is increased, the vibration isolation performance decreases. For this reason, if the vibration damping performance is lowered, the vibration generated by the machine placed on the vibration isolation table cannot be handled. That is, vibration isolation performance and vibration suppression performance are not compatible. Active vibration isolation is a recently introduced method to solve this problem.

  Active vibration isolation replaces the damper in passive vibration isolation with an actuator that is driven by external energy input, such as an electromagnetic linear motor or pneumatic actuator, and measures the vibration of the ground and the vibration isolation table using a vibration sensor. Is a system in which a control signal is generated by guiding the controller to the controller, and the actuator is controlled based on this signal (see Patent Document 1). Since both the vibration isolation performance and the vibration suppression performance can be improved without contradiction, they have been actively introduced into semiconductor manufacturing apparatuses and the like in which equipment moves on a vibration isolation table.

  Furthermore, in recent years, in the medical and industrial fields where ultra-fine technologies such as nanotechnology and biotechnology are required, environmental vibrations and vibrations generated by other devices impair the required accuracy and performance. Vibration isolation has become an essential fundamental technology.

Japanese Patent No. 2673321

  However, in the existing active vibration isolation methods, the weight is increased to increase the rigidity in order to improve the vibration isolation performance and to prevent the vibration isolation table itself from causing elastic vibration. Such an increase in the weight of the vibration isolation table consumes a large amount of energy for vibration isolation, and is becoming a major obstacle to further increasing the size of the vibration isolation device.

On the other hand, the demand for vibration isolator having a large area is increasing in the market. For example, there is an increasing demand for larger LCD TVs, but an active vibration isolator with a large area is indispensable for the large LCD TV manufacturing process.
There is also a demand to install a plurality of vibration isolators connected as a system or several types of vibration isolators in an active vibration isolator.

  In this way, there is a limit in increasing the rigidity of the vibration isolation table by increasing the size of the vibration isolation table in the future. Therefore, it is necessary to drastically reduce the weight of the vibration isolation table and to control the elastic mode associated therewith. When the vibration isolation table is increased in size and weight as described above, an elastic vibration mode of bending or torsion appears in the vibration isolation target frequency range.

  In addition, when a mounted object is placed on a vibration isolation table having an elastic vibration mode, it is easily affected by the mounted object. Furthermore, the motion and vibration that are relatively generated by the mounted object may cause a reduction in vibration isolation performance. Thus, the robustness of the vibration isolation performance with respect to the load becomes a problem.

  Therefore, in addition to controlling the elastic vibration mode of the table in the relatively low frequency vibration isolation target frequency range, which has been regarded as difficult so far, the present invention also considers the behavior of the load that affects the vibration isolation performance. An object is to provide an active vibration isolation device and an active vibration isolation method.

In order to solve the above problems, the vibration isolator of the present invention employs the following means.
That is, the vibration isolator according to the present invention includes a table on which a mounted object is placed, an elastic vibration mode within a vibration isolation target frequency range, a plurality of actuators that drive the table, and a state quantity of the table Active vibration isolator comprising: a table sensor that measures the output of the table; and a controller that controls each actuator based on an equation of state in consideration of the elastic vibration mode of the table. The apparatus includes a load sensor for measuring a state quantity of the load, and the control unit controls each actuator using an output of the load sensor.

Since the actuator is controlled based on an equation of state that takes into account the elastic vibration mode of the table, vibration isolation is possible even when the table vibrates elastically, such as a large and lightweight table.
Furthermore, since the actuator is controlled using the output of the mounted object sensor, the vibration isolation performance of the table is not deteriorated by the mounted object.
The “table state quantity” and “mounting object state quantity” are, for example, the displacement, speed, acceleration, and the like of the table and the loading object.
The present invention can be used for vibration isolation of vibration isolators such as semiconductor manufacturing equipment and large liquid crystal television manufacturing equipment, and can also be used as a collective vibration isolator for a plurality of vibration isolators and several types of vibration isolators connected as a system. it can. Furthermore, in the future, it can also be used for a vibration isolation device used in a space station that is particularly required to be lightweight.

  Further, according to the active vibration isolator of the present invention, the mounted object has an elastic vibration mode within a vibration isolation target frequency range, and the control unit corresponds to the highest order of the elastic vibration mode of the table. A state equation that takes into account a lumped parameter model in which the mass is discretized in the mass number and a lumped parameter model in which the mass is discretized in the mass number corresponding to the highest order of the elastic vibration mode of the load. Each of the actuators is controlled based on this.

It is possible to feedback control based on the equation of state by making the table, which is an elastic body made a distributed constant system, discretize the mass to the mass number corresponding to the highest order of the elastic vibration mode and making it a lumped parameter system model. it can. Therefore, even if the table is flexible, the elastic vibration mode is suppressed, and the heel can behave like a rigid table.
In addition, a lumped parameter model that takes into account vibration characteristics is used for mounted objects that have elastic vibration modes, and is incorporated into the state feedback system, allowing vibration isolation considering the elastic vibration of the mounted object. It becomes. Further, by incorporating it into the state feedback system, even if a change occurs in the load or an error occurs in the lumped parameter system model, it is possible to construct a system that is less susceptible to those effects. That is, it is possible to provide an active vibration isolator having high vibration isolation performance.

For the creation of a “lumped parameter system model”, for example, a method of creating a reduced-dimensional physical model devised by one of the present applicants (Kazuto Sado, Shinji Mitsuda, “elasticity by utilizing unobservable / uncontrollable properties” It is preferable to use a method for creating a reduced-dimensional physical model of a structure and a vibration control method ”, Transactions of the Japan Society of Mechanical Engineers, C, Vol. 57, No. 542, pages 3393-3399 (1991). A feature of this method is that a lumped parameter model can be created at any specified location as long as the vibration mode shape and natural frequency are known by the finite element analysis method and the experimental mode analysis method.
Furthermore, by effectively utilizing this feature, the lumped parameter system model may be created with a reduced dimension at the actuator placement location. If such a lumped parameter model is used, an LQ (Linear Quadratic) control theory, which is one of optimal control theories, can be applied. Thereby, an optimum state feedback control system is configured.

  Further, according to the active vibration isolator of the present invention, the active vibration isolator includes a floor sensor that measures a state quantity of the floor on which the table is installed, and the control unit performs feed-forward control using an output of the floor sensor. Each of the actuators is controlled.

In addition to feedback control, a two-degree-of-freedom control system is configured by feed-forwarding the disturbance obtained by the floor sensor. Thereby, disturbance can be positively removed.
The “floor state quantity” is, for example, floor displacement, speed, acceleration, and the like.

  Moreover, according to the active vibration isolator of the present invention, the control unit includes a low-pass filter.

  Considering only the elastic vibration mode that is the object of vibration isolation, higher-order modes outside this elastic vibration mode may cause spillover, or feedforward control may adversely affect outside the vibration isolation object frequency range. In order to avoid this, a low-pass filter is provided.

  In addition, according to the active vibration isolation method of the present invention, the mounted object is placed, and the table has an elastic vibration mode within the vibration isolation target frequency range, and a plurality of actuators that drive the table, In an active vibration isolation method for controlling each actuator based on a state equation in consideration of the elastic vibration mode of the table, using a table sensor for measuring a state quantity of the table and an output of the table sensor The actuators are controlled using state quantities of the mounted objects.

  In addition to controlling the elastic vibration mode of the table within the vibration isolation target frequency range, it is possible to perform vibration isolation in consideration of the behavior of the load that affects the vibration isolation performance.

Hereinafter, embodiments of an active vibration isolation device and an active vibration isolation method of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 shows a side view of the active vibration isolator 1.
The active vibration isolation device 1 includes a vibration isolation table 3 on which a load 2 is placed, a leg 7 that supports the vibration isolation table 3 on a floor 5, and outputs of sensors, and inputs to each actuator. A control unit 9 that outputs a control signal is provided.

  The vibration isolation table 3 is a metal flat plate having a rectangular shape in a plan view, and is a large size and light weight that is thinner than the area. That is, it has a shape having an elastic mode in a range of 30 Hz, preferably 20 Hz or less and below the vibration isolation target frequency.

  The mounted object 2 is an anti-vibration machine such as a semiconductor manufacturing apparatus or a large-sized liquid crystal television manufacturing apparatus, and has an elastic mode in a range equal to or less than a vibration isolation target frequency. The load 2 is provided with a load acceleration sensor 10 used for vibration detection.

  The leg portions 7 are respectively arranged at the four corners of the vibration isolation table 3. Each leg 7 is provided with an actuator device 11 and a plurality of acceleration sensors 13, 14, 15.

The actuator device 11 includes pneumatic actuators 11a and 11b that can generate a control force independently in the three axial directions of the vertical, horizontal X-axis, and horizontal Y-axis.
As the acceleration sensor, table acceleration sensors 13 and 14 used for vibration detection in each axis direction of the vibration isolation table 3 and a floor acceleration sensor 15 for detecting vibration of the floor 5 are provided.

  A mounting plate 17 is provided on the upper portion of the leg portion 7, and a control force is transmitted to the vibration isolation table 3 in three axial directions via the mounting plate 17.

The control unit 9 obtains control signals obtained based on output signals from the acceleration sensor 10 for the mounted object provided in the mounted object 2 and the acceleration sensors 13, 14, and 15 provided in the leg part 7. 11 is output. As described above, the control unit 9 obtains the feedback signal from the onboard acceleration sensor 10 and the table acceleration sensors 13 and 14 and obtains the feedforward signal from the floor acceleration sensor 15.
The control unit 9 includes an A / D converter 20 to which output signals from the acceleration sensors 13, 14, and 15 are input, and a DSP that calculates control signals using the output signals from the A / D converter 20. (Digital Signal Processor) 22, a D / A converter 24 that converts a control signal from the DSP 22 into an analog signal, and an amplifier 26 that amplifies the output of the D / A converter 24.

  The DSP 22 estimates displacement and velocity signals in the respective axial directions from a state estimator provided therein, and calculates a control signal. The calculation of the control signal is performed based on a state equation in consideration of not only the vibration isolation table 3 but also the elastic vibration mode of the load 2. Specifically, as will be described later, this state equation is a lumped parameter model in which the mass is discretized in the same number of mass points as the highest order of the elastic vibration mode within the vibration isolation target frequency range of the vibration isolation table 3. In addition, a lumped parameter model in which the mass is discretized to the same number of mass points as the highest order of the elastic vibration mode within the vibration isolation target frequency range of the load 2 is taken into consideration. In other words, the DSP 22 stores a program in which a control model created by analyzing in advance the elastic vibration mode of the vibration isolation table 3 and the load 2 is described.

Next, the most important control model creation method and control system design algorithm in control system design will be specifically described.
First, the vibration characteristics of the vibration isolation table 3 are obtained by experimental mode analysis. By this experimental mode analysis, the highest order of the elastic vibration mode within the vibration isolation target frequency range is determined. In the following description of the present embodiment, it is assumed that a fifth-order elastic vibration mode is obtained in the vertical direction and a third-order elastic vibration mode in the horizontal direction.

In order to consider the elastic vibration mode in the vertical direction, the “reduced physical model creation method” is applied to create a physical model representing the elastic vibration for the controlled object. The reduced-order physical model has a number of mass points equal to the highest order of the elastic vibration mode to be controlled, and these mass points are connected by a spring and a damper. Based on controllability and observability, four modeling points (mass points) in the controlled object are arranged on the actuator device 11 and one central point which is the maximum amplitude point of the fifth-order mode.
The components of each mode are read at these modeling points to create a temporary mode matrix. For example, a mode component φ _ij (where i is a modeling point number and j is a mode number) having a maximum amplitude of 1 at five modeling points in the j-th mode is read for each mode and a temporary mode matrix Φ ′ Create

Since the tentative mode matrix Φ ′ uses eigenmode components of the distributed parameter system as elements of the matrix, the diagonalized mass matrix M cannot be derived from the tentative mode matrix Φ ′. Therefore, an error function ε is defined to satisfy the condition of the lumped parameter system, and a correction vector δΦ is introduced so as to make it zero, and the error function ε is corrected. A correction vector that makes the error function ε zero is obtained by the following equation.

The correction mode matrix Φ is obtained through the procedure for correcting the temporary mode matrix Φ ′ as described above.
Using this modified mode matrix Φ, the following mass matrix M and stiffness matrix K are obtained. Ω is a frequency matrix having the natural frequency of each mode as a diagonal element.
M = (ΦΦ ^T ) ⁻¹ (2)
K = (Φ ^T ) ⁻¹ Ω ² Φ ⁻¹ (3)
here,

If the mass matrix M and the stiffness matrix K are obtained in this way, the equation of motion in the vertical direction is obtained as follows. Here, Z is a vertical state vector. In this embodiment, since it is a matrix of 5 rows × 5 columns, it becomes a 5-mass point system lumped parameter system model.
MZ + KZ = 0 (5)

Similarly in the horizontal direction, a lumped parameter system model with a mass number equal to the highest order of the elastic vibration mode obtained by the experimental mode analysis is created.
However, in the horizontal direction, the vibration isolation table 3 which is a flat plate as in the present embodiment has a flexible vibration in a very high frequency region unlike the vertical direction. There are many cases that only exist. In such a case, the calculation is performed assuming that it is a rigid body.

Similarly, a lumped parameter system model having a mass number equal to the highest order of the elastic vibration mode obtained by the experimental mode analysis is also created for the load 2.

The control object (vibration isolation object) is displayed as a state variable from each model obtained as described above.
The state equation and output equation in the vertical direction are as follows.
X _v = A _v X _v + B _v u _v (6)
Y _v = C _v X _v (7)
Here, _{X v} is the state vector, _{u v} is a control amount _vector, A _{v, B} v is the coefficient matrix of the controlled object.

Similarly, the horizontal state equation and the output equation are expressed as follows using the suffix h.
X _h = A _h X _h + B _h u _h (8)
Y _h = C _h X _h (9)
Here, X _h is a state vector, u _h is a control amount vector, and A _h and B _h are coefficient matrices to be controlled.

Similarly, the state equation and output equation of the load 2 are expressed as follows using the subscript a.
X _a = A _a X _a + B _a u _a (10)
Y _a = C _a X _a (11)
Here, X _a is a state vector, u _a is a controlled variable vector, and A _a and B _a are coefficient matrices to be controlled.

Furthermore, feedforward control (hereinafter referred to as “FF control”) for the purpose of insulating ground disturbance from the floor 5 is applied for positive disturbance elimination. However, the FF control alone does not have the ability to correct the error when the control object including the modeling error changes, and is therefore the optimum control of the state feedback control (hereinafter referred to as “FB control”). Disturbance canceling two-degree-of-freedom control system using FF control in combination with LQ (Linear Quadratic) theory.
FIG. 2 shows a block diagram of this disturbance cancellation type two-degree-of-freedom control system. In the figure, W is a disturbance, _Hf is an FF gain, and _Kc is an FB gain.

In this embodiment, only the elastic vibration mode that is the object of vibration isolation is considered when modeling, and the ignored higher-order modes outside the elastic vibration mode that is the object of vibration isolation may cause spillover or vibration isolation. There is a possibility that the FF control has a deteriorating effect outside the target frequency range. In order to avoid this, a low-pass filter is provided.
In FIG. 2, the subscript f represents the matrix and vector of the low-pass filter, and the subscript c represents the matrix and vector of the anti-vibration table 3 to be anti-vibrated.

The three-dimensional state equation of the extended system including the vibration isolation target and the state equation of the filter is as follows.
X = AX + Bu (12)
Here, X = {X _vf , X _v , X _hf , X _h , X _va , X _a } (13)

The feedback gain K = {K _f , K _c } in FIG. 2 is obtained as follows.
First, a solution P is obtained from the following Riccati equation.
^{PA + A T P-PBR -1} B T P + Q = 0 ····· (14)
Then, it is determined as follows.
_{K = {K f, K c} } = R -1 B T P ····· (15)
Here, K _f is the feedback gain vector according to the filter, K _c is the feedback gain vector according to the controlled object, Q, R is a weighting matrix applied to the state vector control quantity.

Further, H _f is determined so as to cancel the disturbance using the inverse transfer function of the controlled object model. For this purpose, good results cannot be obtained unless the controlled object model is accurately known. However, in the present embodiment, the model can be obtained accurately, so that the effect of disturbance canceling feedforward control can be maximized. In addition, since the feedforward control system can be designed for each mass point, the degree of disturbance cancellation can be adjusted depending on the location.

According to this embodiment, there exist the following effects.
According to the present embodiment, a reduced lumped parameter system model is created for the vibration isolation table 3 and vibration control is performed by state feedback. Therefore, even if the vibration isolation table 3 is flexible, the elastic vibration isolation table 3 is elastic. The vibration mode is suppressed, and the kite can behave like a rigid table.
Furthermore, since a lumped parameter system model that takes vibration characteristics into consideration is used for the mounted object 2 and incorporated in the state feedback system, vibration isolation considering the elastic vibration of the mounted object 2 is possible. Moreover, even if a change occurs in the load 2 or an error occurs in the lumped parameter system model by incorporating it in the state feedback system, it is possible to construct a system that is not easily influenced by those effects. That is, it is possible to provide an active vibration isolator having high vibration isolation performance.

  In the present embodiment, four actuator devices 11 are used. However, when the vibration isolation table 3 is lengthened, the number may be increased to six or eight. Also in this case, a control model is created by performing vibration mode analysis including the actuator device 11.

Examples of the active vibration isolator according to the present invention will be described below.
FIG. 3 shows a conceptual diagram of the appearance and control system configuration of the model vibration isolator used in this embodiment.
The dimensions of the vibration isolation table 3 to be controlled are 600 × 320 × 2 mm aluminum plates. The vibration isolation table 3 has voice coil motors 30 installed as actuators at its four corners, and is supported thereby.
A support spring 32 is arranged in parallel with the voice coil motor 30. Further, eight linear guides 34 and four electromagnetic actuators 36 are provided in the horizontal direction.
The actuators 30 and 36 and the vibration isolation table 3 are supported by a piano wire 38, and can independently move three-dimensionally.
In order to observe the state quantity, laser displacement sensors 38 are arranged in a total of three locations, including four in the vertical direction at the position of the voice coil motor 30, one in the center of the table, and the horizontal direction in the X and Y directions. The displacement relative to the absolute fixed surface can be measured. Further, when the additional object (mounted object) 50 is placed as shown in FIG. 10, a laser displacement sensor for measuring the horizontal displacement of the tip of the additional object is disposed. Note that a vibration detector such as an acceleration sensor may be used instead of the laser displacement sensor.

  A signal from each sensor is sent to the controller through an A / D converter, and a control signal calculated by the controller is sent to each actuator via the D / A converter and a signal amplifier. In this way, the state feedback control system is configured.

On the other hand, the ground disturbance of the floor 5 is detected by the laser displacement sensor 40 on the vibration of the installation surface of the vibration isolation table 3 and sent to the controller 42. The controller 42 constitutes a feedforward control system that cancels ground disturbance based on this sensor signal, and sends it to each actuator as a feedforward signal.
As described above, in the controller 42, a two-degree-of-freedom control system that combines feedback control and feedforward control is configured.

Next, the control model creation method and the control system design algorithm in this embodiment will be described in detail.
Regarding the vibration characteristics of the vibration isolation table 3, the results obtained by the experimental mode analysis are shown in FIG. 4 in the vertical direction and in FIG. 5 in the horizontal direction. In the vertical direction, the primary mode corresponds to the bouncing mode, the secondary mode corresponds to the pitching mode, the tertiary mode corresponds to the rolling mode, the quaternary mode corresponds to the primary twist mode, and the fifth mode corresponds to the primary bending mode. It can be seen that the rigid body mode and the elastic mode are combined.
On the other hand, in the horizontal direction, the primary mode is a sliding mode in the X direction, the secondary mode is a sliding mode in the Y direction, and the tertiary mode is a yawing mode, which is a rigid body mode.
As described above, in this embodiment, the vertical fifth mode and the horizontal third mode are the control target modes.

   Then, after creating a temporary mode matrix Φ ′ as shown in Equation (1), a correction mode matrix Φ is obtained through a procedure for correcting the temporary mode matrix to obtain a mass matrix M and a stiffness matrix K (Equation ( 2) and formula (3)).

  Using the mass matrix M and the stiffness matrix K, the equation of motion in the vertical direction is obtained as in equation (5). In this embodiment, since the matrix has 5 rows and 5 columns, a 5-mass system lumped parameter system model is created as shown in FIG. In the figure, each actuator 11 is attached to mass points 1 to 4.

  In the horizontal direction, unlike the vertical direction, the flexible vibration is in a very high frequency range, so only the rigid body mode exists in the low frequency range to be controlled. Therefore, in this embodiment, it is regarded as a rigid body. FIG. 7 shows a conceptual diagram of the horizontal model and the parameters at this time.

In order to verify the validity of each model created as described above, the frequency response between the simulation result and the actual measurement was compared.
FIG. 8 shows the frequency response in the Z direction of the material point 1 when the material point 1 is vertically vibrated, and FIG. 9 shows the frequency response in the X direction when the material point 1 is vibrated in the X direction. The thick solid line is the actual measurement value, and the thin broken line is the simulation value. Each response is in good agreement with both the actual measurement and the simulation, indicating that the accuracy of the created model is high.

The controlled object is displayed as a state variable from each obtained model. Equations (6) and (7) are obtained in consideration of the drive coefficient, back electromotive force, inductance, and resistance of the actuator to be used.
The coefficient matrices A _v and B _v and each vector used in the equation (6) can be expressed as follows.

Here, I is a unit matrix, O is a zero matrix, and A ₁₃ , A ₃₁ , and A ₃₃ are coefficient matrices that affect each other between the actuator and the table. L _vi , I _i , and u _i are the inductance, control current, and control amount of the i-th actuator, respectively.

Similarly, the state equation in the horizontal direction is expressed as equations (8) and (9). Each vector and coefficient matrix at this time can be expressed as follows.

  Considering the fact that there are many flexible bodies that have vibration modes in the low frequency range such as optical microscopes, what is actually mounted on the vibration isolation table 3 is 0 Hz to 20 Hz, which is the vibration isolation range of the vibration isolation table 3. The one with the elastic mode in the low frequency range up to is adopted. In this embodiment, a flat plate 50 that is regarded as a mounted object is installed on the vibration isolation table 3. The dimension of the flat plate is an aluminum plate of 250 × 50 × 1 mm, and the mass is 81.5 g. The flat plate 50 was fixed to the center portion of the vibration isolation table 3. The appearance at the time of fixation is shown in FIG.

In FIG. 11, the result by the experiment mode analysis of the flat plate which is an addition is shown.
From the figure, it can be seen that the primary bending mode is within the vibration isolation target frequency range. The mounted object has a degree of freedom only in the X direction. Using the reduced-dimensional physical model creation method in the X direction, the horizontal model of the vibration isolation table 3 was expanded to create a concentrated physical model of a two-mass system. . FIG. 12 shows a conceptual diagram of the model and each parameter when the appendage is mounted.

In this embodiment, the adduct has one degree of freedom in the X direction. Expressions (8) and (9), which are state variable displays in the horizontal direction, can be expressed as expressions (10) and (11) in an expanded form.
Here, each vector and matrix can be expressed as follows.

In this equation (23), state variables x _a and x _a are newly added to equation (20). This is a variable that represents the vibration velocity and displacement in the X direction of the appendage. By incorporating these variables into the control system design, the vibration of the appendage is taken into account. Although only the X direction is considered in this embodiment, the Y and Z directions can be considered in the same manner.

Also in the present embodiment, feedforward control (hereinafter referred to as “FF control”) for the purpose of insulating ground motion disturbance is applied as in the above-described embodiment.
And it is a disturbance cancellation type 2 degree-of-freedom control system using FF control in combination with LQ theory (see FIG. 2).

Also in this example, as in the above-described embodiment, a low-pass filter is employed, the cutoff frequency is set to 30 Hz, and the filter attenuation factor ξ = 0.7.
The expanded three-dimensional state equation including the controlled object and the state equation (A _f , B _f , C _f ) of the filter is expressed as equations (12) and (13).
Here, the coefficient matrices A, B, and C are expressed as follows.

Then, the feedback gain K = {K _f , K _c } is obtained using equations (14) and (15).

  Using the control model and control system described above, a control experiment was conducted to investigate the effect of this example. The experimental method is a case where a ground vibration disturbance is assumed and sweep excitation is performed from a vibration test apparatus, and a case where a random noise input of 0 to 20 Hz is adopted assuming an actual fine vibration.

13 to 15 show frequency response characteristics of vibration transmissibility during sweep excitation.
In FIGS. 13 and 14, as a comparative example of the present embodiment, a state equation (equations (6) to (9)) that does not consider the influence of the additive in a state where the additive is not placed is used. It is shown.
FIG. 15 shows, as a comparative example of the present embodiment, a state equation (equations (6) to (9)) that does not consider the influence of the additive when the additive is placed. ing.
The vertical axis indicates the vibration transmissibility as a gain dB value. Since the ratio of the table displacement (or acceleration) to the disturbance displacement (or acceleration) applied to the vibration isolation table by 0 dB is 1, the vibration isolation effect appears at 1 or less. The smaller the dB value, the greater the vibration isolation effect. It is shown that.

FIG. 13 shows the vibration isolation effect in the vertical direction, in which the thick solid line is uncontrolled, the thin broken line is the state FB control only, and the thin solid line is the two-degree-of-freedom control with the FF control added. Five vibration modes were included in the range of 20 Hz at the time of non-control, but only one peak appeared in the vicinity of 10 Hz by the state FB control, as if exhibiting vibration characteristics of a one-degree-of-freedom vibration system. This indicates that the table is a rigid table by the state FB control although it is originally a flexible table. However, in the state FB control, even if vibration control can be performed, the vibration transmissibility cannot be lowered. This can be done by adding FF control.
Thus, by combining the two controls, the vibration transmissibility is reduced by about −20 to −10 dB, and further reduction is possible.
FIG. 14 shows the vibration isolation effect in the horizontal direction, and the same vibration isolation effect as in the vertical direction is obtained.
FIG. 15 is an example in which the vibration of the appendage deteriorates the vibration isolation performance. Although the natural frequency of the appendage was 12 Hz (see FIG. 11), since the influence of this vibration was not taken into account, the vibration transmissibility increased in the vicinity of 12 Hz, which significantly deteriorated the vibration isolation performance.

Comparative examples of time calendar responses to random noise are shown in FIGS.
FIG. 16 shows the response measured at the mass point 1 (see FIG. 6) at the time of vertical vibration, using the two-degree-of-freedom control similar to FIG. FIG. 17 also shows the response measured in the X direction during vibration in the X direction using the two-degree-of-freedom control similar to that in FIG. In each figure, the upper stage is the ground motion disturbance input, the middle stage is the non-control, and the lower stage is the time calendar response when the state FB control and the FF control are combined. In each case, the vibration transmitted to the table is reduced to 1/10 or less by the combination of the FB control and the FF control.
As described above, as shown in FIGS. 13, 14, 16, and 17, in a state where no additional object is placed, a good vibration isolation effect can be obtained by using the two-degree-of-freedom control. However, as shown in FIG. 15, in the state where the additive is placed, a desired vibration isolation effect cannot be exhibited due to the influence of the additive.

Next, experimental results of this example are shown.
The state FB control system incorporating the vibration of the appendage is designed using the equations (10) and (11). Since the vibration of the additive is well controlled by the FB control, the vibration transmissibility is further reduced by the FF control.
FIG. 18 shows the result of the time calendar response. At the time of non-control, the vibration of the vibration isolation table is increased more than the disturbance input due to the influence of the vibration of the additional material, but the influence of the vibration of the additional material is removed by the two-degree-of-freedom control.

FIG. 19 shows a time calendar response to random noise. It can also be seen from the figure that the effect of the additive is removed by the two degree of freedom control.
As can be seen from FIG. 18 and FIG. 19 in comparison with FIG. 15, not only the vibration isolation table but also the additional object can be controlled by incorporating the additional object itself into the model.

Next, FIG. 20 shows a time calendar response when a 1 mm displacement is given to the appendage and released, assuming that the appendage itself is directly input as a disturbance. In the same figure, the time calendar response of non-control from the top, control of only the vibration isolation table, and control in consideration of additional items is shown. From the figure, it can be seen that the vibrations converge quickly when the additionals are taken into account.
As described above, it was confirmed that the control performance can be guaranteed even in an irregular state that cannot be dealt with only by the vibration isolator such as an input directly to the appendage itself.

It is the side view which showed the vibration isolator which concerns on embodiment of this invention. It is a block diagram of 2 degree-of-freedom control concerning an embodiment of the present invention. It is the perspective view which showed the vibration isolator which concerns on the Example of this invention. It is the figure which showed the vibration mode form of the perpendicular direction of a vibration isolation table. It is the figure which showed the vibration mode form of the horizontal direction of a vibration isolation table. It is the figure which showed the 5-mass point concentrated constant system model of the perpendicular direction. It is the figure which showed the model of the perpendicular direction. It is the figure which showed the frequency response by the simulation by the 5-mass point lumped parameter system model of a perpendicular direction, and measurement. It is the figure which showed the frequency response by the simulation by the model of a horizontal x-axis direction, and measurement. It is the perspective view which showed the state which mounted the additional material on the vibration isolation table. It is the figure which showed the vibration mode form of the appendage. It is the figure which showed the horizontal direction model of the vibration isolation table containing an appendage. It is the figure which showed the frequency response in the vertical direction of a comparative example. It is the figure which showed the frequency response in the horizontal direction of a comparative example. It is the figure which showed the frequency response in the horizontal direction at the time of mounting an appendage in a comparative example. It is the figure which showed the time history response in the vertical direction of a comparative example. It is the figure which showed the time history response in the horizontal direction of a comparative example. It is the figure which showed the frequency response by a present Example which considered the vibration of the appendage. It is the figure which showed the time history response which considered the vibration of the appendage. It is the figure which showed the time history response when a disturbance is added to an appendage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anti-vibration device 3 Anti-vibration table 5 Floor 9 Control part 10 Acceleration sensor 11 for mounted objects Actuator devices 13 and 14 Acceleration sensor 15 for tables 15 Acceleration sensor for floors

Claims (5)

A table on which the mounted object is placed and has an elastic vibration mode within the vibration isolation target frequency range;
A plurality of actuators for driving the table;
A table sensor for measuring the state quantity of the table;
A controller for controlling each actuator based on an equation of state in consideration of the elastic vibration mode of the table, using the output of the table sensor;
In an active vibration isolator with
A load sensor for measuring a state quantity of the load;
The active vibration isolator, wherein the control unit controls each of the actuators using an output of the mounted object sensor. The mounted object has an elastic vibration mode within a vibration isolation target frequency range,
The control unit includes a lumped parameter model in which mass is discretized to a mass number corresponding to the highest order of the elastic vibration mode of the table, and a mass number corresponding to the highest order of the elastic vibration mode of the mounted object. 2. The active vibration isolator according to claim 1, wherein each of the actuators is controlled based on a state equation in consideration of a lumped parameter model in which the mass is discretized. A floor sensor for measuring a state quantity of the floor on which the table is installed;
The active vibration isolator according to claim 1, wherein the control unit controls each actuator by feedforward control using an output of the floor sensor.   The active vibration isolation device according to claim 1, wherein the control unit includes a low-pass filter. A table on which the mounted object is placed and has an elastic vibration mode within the vibration isolation target frequency range;
A plurality of actuators for driving the table,
A table sensor for measuring the state quantity of the table;
In the active vibration isolation method that uses the output of the table sensor and controls each actuator based on a state equation that takes into account the elastic vibration mode of the table,
An active vibration isolation method, wherein each actuator is controlled using a state quantity of the mounted object.

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