JP2013249916A - Active vibration isolator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active vibration isolator that exhibits maximally-high vibration insulation performance.SOLUTION: An active vibration isolator comprises: a filter 8 having high-pass filter characteristics for removing a low-frequency component containing an error component of an output signal of a load cell 5 as a power measuring part; a compensator 9 for compensating the low-frequency component removed by the filter 8 on the basis of the acceleration of a body 2 to be supported; and a controller (controller 10, an operator 11 and a gain 12) for creating a drive control signal of an actuator 4 on the basis of an output signal of the filter 8 and an output signal of the compensator 9.

Description

  The present invention relates to an active vibration isolator that suppresses transmission of vibration from a vibration source to a device that dislikes vibration.

  2. Description of the Related Art Conventionally, a vibration isolator is used for precision equipment that dislikes vibration such as a semiconductor manufacturing apparatus in order to suppress transmission of vibration from a vibration source to the precision equipment. A vibration isolator is generally configured by combining an elastic element such as a coil spring and a damping element such as an oil damper, and a vibration isolator composed only of passive elements such as a coil spring or an oil damper is a passive type vibration. Called an isolation device. The vibration isolation performance of a passive vibration isolator is defined by the natural frequency of the vibration isolator itself, which is determined by the mass of the object supported by the isolator and the rigidity of the elastic element. Increases performance. Therefore, when trying to improve the vibration isolation performance of the passive vibration isolation device, it is necessary to reduce the rigidity of the elastic element if the mass of the object to be supported is fixed.

  However, on the other hand, there is a lower limit for the rigidity of the elastic element because the elastic element needs to have high rigidity so that the elastic element does not yield even when the amount of deformation of the elastic element due to the static load of the supporting object increases. It is difficult to make the rigidity lower than a certain level. For this reason, there is a case where a passive type vibration isolator cannot provide sufficient performance for vibration isolation of precision equipment that requires very high vibration isolation performance.

  As a method for improving the vibration isolation performance of the passive vibration isolation device, an active vibration isolation device in which an actuator is added to the passive vibration isolation device is known. For example, in the active vibration isolator disclosed in Patent Document 1, an actuator is added in parallel with the passive vibration isolators, and a coil spring is disposed in parallel with the passive vibration isolators. A load cell for measuring a restoring force generated by the deformation of the spring is provided in series with the coil spring. When operating the device, the load cell detects the restoring force of the coil spring caused by the relative displacement between the supported object and the vibration source, and the actuator is driven and controlled according to the restoring force detected by the load cell. Is increasing.

Japanese Patent No. 4827813

  However, the load cell used as the control input signal of the actuator in the active vibration isolator described in Patent Document 1 does not completely output the output signal even when there is no load, and a certain minute signal is output. There is a zero point offset to be performed. In addition, since the load cell also has a temperature drift characteristic in which the output signal changes according to changes in the ambient temperature environment, the output signal of the restoring force of the coil spring detected by the load cell is subject to zero point offset and temperature drift. The resulting error is included. For this reason, when the actuator is driven and controlled based on a signal including such an error, the vibration insulation performance is deteriorated, and there is a problem that sufficient vibration insulation performance cannot be obtained even with an active vibration insulation device.

  This invention is made | formed in view of the above, Comprising: It aims at providing the vibration insulation apparatus which exhibits the vibration insulation performance as high as possible.

  In order to solve the above-described problems and achieve the object, the present invention provides an active vibration isolator that is installed on a floor and supports a supported object, and is disposed between the floor and the supported object. A passive vibration isolator that is installed to passively reduce vibration from the floor to the supported object, and a first that the passive vibration isolator receives in a direction in which the passive vibration isolator is disposed. A force measuring unit for measuring the force of the load, an acceleration measuring unit for measuring the acceleration of the supported object, and the passive vibration isolator between the floor and the supported object. An actuator that generates a second force in the direction in which it is disposed, and a control signal is supplied to the actuator to drive the actuator so that the first force and the second force cancel each other. An actuator driving device, The actuator driving device includes a high-pass filter that removes a low-frequency component including an error component of the output signal from the output signal of the force measurement unit, and a low-pass filter that is removed by the high-pass filter based on the output signal of the acceleration measurement unit. A compensator that compensates for a frequency component, and a controller that generates a control signal to be supplied to the actuator based on an output signal of the high-pass filter and an output signal of the compensator.

  According to the present invention, since the active vibration isolator can drive the actuator in consideration of the error component of the force measurement unit, it has an effect that it can exhibit as high a vibration isolation performance as possible. .

FIG. 1 is a diagram showing a schematic configuration of an active vibration isolator according to Embodiment 1 of the present invention. FIG. 2 is a diagram illustrating a configuration example of the passive vibration isolator 1. FIG. 3 is a diagram showing the relationship between the breakpoint angular frequency and the vibration transmissibility of the filter provided in the active vibration isolator of Embodiment 1 of the present invention.

  Embodiments of an active vibration isolator according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing an outline of the configuration of a first embodiment of an active vibration isolator according to the present invention. The active vibration isolator according to the first embodiment is configured to be interposed between a supported object 2 on which a precision device that dislikes vibration is mounted and a floor 3 on which a vibration source is present. Is prevented from propagating to a precision instrument mounted on the supported object 2. Examples of precision equipment mounted on the supported object 2 include a semiconductor manufacturing apparatus. Further, examples of the vibration source that applies vibration to the floor 3 include a refrigerator and a rotating machine. Here, the description will be made assuming that the precision device is mounted on the supported object 2, but the active vibration isolation device may be directly connected to the precision device.

  As shown in the figure, the active vibration isolator of Embodiment 1 is disposed so as to connect the supported object 2 and the floor 3 and receives a force in the disposed direction. 1 and a load cell 5 that is connected in series to the passive vibration isolator 1 and measures a force received by the passive vibration isolator 1, and the passive vibration isolator 1 and the load cell 5 The actuator 4 that is arranged in parallel and generates force in the arranged direction and the drive that controls the actuator 4 so that the force received by the passive vibration isolator 1 and the force generated by the actuator 4 cancel each other out. A driver (actuator driving device) 7 is provided.

  The drive driver 7 generates a control signal for driving the actuator 4 based on the output signal of the load cell 5 and the output signal of the acceleration sensor 6 mounted on the supported object 2. More specifically, the drive driver 7 removes the low-frequency fluctuation caused by the zero point offset and the temperature drift included in the output signal of the load cell 5, and the influence of the filter 8 on the output signal of the acceleration sensor 6. The compensator 9 for compensation, the controller 10 for generating the control input to the actuator 4 based on the output signal of the acceleration sensor 6, the output of the filter 8, the output of the compensator 9, and the output of the controller 10 are added or subtracted. An arithmetic unit 11 and a gain 12 for adjusting the magnitude of the output of the arithmetic unit 11 are included. The output of the gain 12 is input to the actuator 4. The drive driver 7 is physically configured by an electric circuit including an arithmetic processing unit such as a microcomputer and an analog integrated circuit.

  The passive vibration isolator 1 is configured by combining an elastic element such as a coil spring and a damping element such as an oil damper, and passively reduces the vibration transmitted from the floor 3 from being transmitted to the supported object 2. Regarding the number of combinations and arrangement methods of the elastic elements and the damping elements included in the passive vibration isolator 1, various configurations are assumed. For example, the most basic configuration may include only one elastic element. In this case, although the structure is very simple, a very large vibration is excited for the vibration having the same frequency as the natural frequency of the passive vibration isolator 1 itself. Other than this, a configuration in which one elastic element and one damping element are arranged in parallel, or an elastic element is connected in series with the damping element, and the elastic element is arranged in parallel with the damping element and the elastic element. The structure etc. to perform are considered. In the following, for ease of understanding, the passive vibration isolator 1 will be described with reference to a configuration in which one elastic element 13 and one damping element 14 are arranged in parallel as shown in FIG. The configuration of the passive vibration isolator 1 is not limited to this. For example, any structure combined with an elastic element or a damping element can be applied to the passive vibration isolation device 1 as long as it aims at vibration isolation.

  The actuator 4 is disposed between the supported object 2 and the floor 3, and is driven and controlled by the drive driver 7 based on output signals from the load cell 5 and the acceleration sensor 6, thereby reducing vibration transmission from the floor 3. Thus, the vibration isolation performance of the passive vibration isolation device 1 is improved. As the actuator 4, an actuator such as a voice coil motor or a piezoelectric actuator is used according to the required specifications and purpose.

The load cell 5 is connected in series with the passive vibration isolator 1 and detects a force acting between the passive vibration isolator 1 and the floor 3. There are several methods for the load cell 5 depending on the measurement principle such as strain gauge type and piezoelectric type, but the load cell 5 can be applied regardless of the method as long as it can be detected from the DC component or low frequency. is there. Further, since the output signal of the load cell 5 is generally a very small signal, when the output signal of the load cell 5 is actually read by the drive driver 7, it is connected between the load cell 5 and the drive driver 7. The output signal is read after the signal is amplified by an amplifier or the like. Specifically, if the rigidity of the elastic element 13 is k, the viscous damping coefficient of the damping element 14 is c, the absolute displacement of the supported object 2 is x _P , and the absolute displacement of the floor 3 is x _B , the load cell 5 detects it. force F _L between passive vibration isolators 1 and the floor 3 to be is expressed by the equation (1).

  Here, the output signal of the load cell 5 has a positive tensile force.

The acceleration sensor 6 is mounted on the supported body 2 detects the acceleration ^d 2 _x P / dt ² caused the supported object 2. The acceleration information detected by the acceleration sensor 6 is output to the drive driver 7.

Filter 8, against the force F _L between the passive vibration isolator 1 and the floor 3 detected by the load cell 5, the filtering process to remove low-frequency variations due to the zero point offset and temperature drift And output the filtered signal to the computing unit 11. Specifically, between the passive vibration isolator 1 and the floor 3 of the output value of the force F _L, to remove low-frequency components caused by the DC error component and temperature drift due to the zero point offset, these A high-pass filter H (ω) is applied to extract signal components that do not contain errors. Here, ω represents the corner frequency of the high-pass filter. However, when subjected to high-pass filter H (omega), filtering the previous force signal F _L is lost even a low-frequency signal necessary for the improvement of natural vibration isolation performance. For this reason, when high vibration isolation performance is targeted in the active vibration isolation device, the filter corner frequency ω is preferably as low as possible.

In general, by setting the lowest possible corner angular frequency omega of the high-pass filter, the signal information necessary for the improvement of the vibration isolation performance which is removed from the force signal F _L at the high-pass filter H (omega) is zero It is expected that desired vibration isolation characteristics can be realized from a low frequency close to the value set at the corner angular frequency ω. However, the present invention for the first time reveals that the value set at the corner angular frequency ω is merely set to a lower corner angular frequency ω, regardless of the filter configuration such as the order of the high-pass filter H (ω). Faced with a new problem that the desired vibration isolation characteristics cannot be realized from a low frequency close to. Hereinafter, in order to facilitate understanding, an example of a first-order high-pass filter represented by Expression (2) will be described as the high-pass filter H (ω). However, the following description for the first-order high-pass filter can be easily extended to a higher-order high-pass filter, and there is no difference in the problem that is the conclusion.

Assuming that the mass of the supported object 2 is m _P and the force of the actuator 4 is F _A , the equation of motion of the supported object 2 is expressed as Equation (3).

From the relationship between Equation (1) and Equation (3), as a force F _A of the actuator 4, when the output power of the same magnitude as the force signal F _L which actuator 4 is detected by the load cell 5, the formula ( As shown in 4), the force applied to the supported object 2 becomes zero, and vibration transmission from the floor 3 to the supported object 2 can be completely insulated.

However, in practice in order to remove the influence of the zero point offset and temperature drift, it is necessary to apply a high-pass filter H (omega) shown in Equation (2) against the force signal F _L detected by the load cell 5 . The equation of motion when the high-pass filter H (ω) is applied is expressed by Equation (5).

Here, X _P (s) indicates the displacement of the supported object 2 after Laplace conversion, and X _B (s) indicates the displacement of the floor 3 after Laplace conversion. Obtaining Equation (6) Equation (5) by modifying the calculating the transfer rate G of the absolute displacement x _P of the supported object 2 (s) with respect to the absolute displacement x _B of the floor 3.

Based on a specific numerical example, consider the relationship between the transmission rate G (s) shown in Equation (6) and the corner angular frequency ω of the high-pass filter. 1kg mass _{m p} of the supported object 2, 10000 N / m stiffness k of the elastic element 13, a viscous damping coefficient c of the damping element 14 as a 1000 ns / m, the corner angular frequency ω of the high-pass filter 2 [pi × ^{10 -2} FIG. 3 shows changes in the transmission rate G (s) when changed to 2π × 10 ⁻⁴ and 2π × 10 ⁻⁶ [rad / s].

As can be seen from FIG. 3, even when the corner frequency ω of the high-pass filter is set to 2π × 10 ⁻⁶ [rad / s], the frequency at which sufficient vibration isolation is obtained with the transmission rate G (s) is 10 ⁻ It is about ¹ [Hz], and is not about 10 ⁻⁶ [Hz], which is about the same as the corner frequency of the high-pass filter, as generally expected. For this reason, when the corner angular frequency ω of the high-pass filter is set to 2π × 10 ⁻⁶ [rad / s] (10 days or more in a cycle), so low that it is not practically applicable in view of the transient response of the filter 8. However, desired vibration isolation characteristics cannot be obtained from a low frequency close to the value set at the corner angular frequency ω.

  From the above, in order to realize vibration isolation characteristics from a low frequency while eliminating the influence of the zero point offset and temperature drift included in the output signal of the load cell 5, the output signal of the load cell 5 is simply filtered as a configuration. It can be seen that adding 8 is not enough.

  Therefore, the compensator 9 generates a signal for compensating the low-frequency vibration information of the load cell 5 lost by the filter 8 based on the output signal of the acceleration sensor 6, and outputs the signal to the calculator 11. For example, the compensator 9 may be configured by a filter having a reverse characteristic of the filter characteristic of the filter 8. As a filter having the inverse characteristics of the filter 8, a filter in which the denominator and the numerator of the high-pass filter 8 shown in Equation (2) are simply replaced is conceivable. By applying a filter having an inverse characteristic of the filter 8 to the output signal of the acceleration sensor 6 as the compensator 9, only the low frequency vibration information of the load cell 5 lost by the filter 8 is extracted from the output signal of the acceleration sensor 6. be able to. Alternatively, the compensator 9 may be configured to estimate low-frequency vibration information lost in the filter 8 from the difference between the output signal of the load cell 5 subjected to the filter 8 and the output signal of the acceleration sensor 6. In this case as well, the low frequency vibration information of the load cell 5 lost by the filter 8 can be compensated by the compensator 9.

  The controller 10 generates a control signal for reducing the acceleration of the supported object 2 detected by the acceleration sensor 6 based on the output signal of the acceleration sensor 6, and outputs the control signal to the calculator 11. As a configuration of the controller that reduces the acceleration of the supported object 2 and improves the vibration isolation performance, for example, a configuration in which PI control is performed on the output signal of the acceleration sensor 6 is conceivable.

  The computing unit 11 adds or subtracts each signal output from the filter 8, the compensator 9, and the controller 10 according to the sign of each signal, and outputs the result to the gain 12. For example, the computing unit 11 subtracts the output value of the controller 10 and the compensator 9 from the output value of the filter 8, and outputs the value obtained by the subtraction.

  The gain 12 generates a drive control signal for the actuator 4 by integrating the gain with respect to the signal transmitted from the computing unit 11 so as to amplify or reduce the signal information, and outputs the drive control signal to the actuator 4.

  As described above, according to the first embodiment of the present invention, the active vibration isolator has a high-pass filter characteristic that removes a low-frequency component including an error component of the output signal of the load cell 5 as a force measurement unit. The filter 8, the compensator 9 that compensates the low-frequency component removed by the filter 8 based on the acceleration information of the supported object 2, the output signal of the filter 8, and the output signal of the compensator 9 Since the controller (the controller 10, the arithmetic unit 11, and the gain 12) for generating the drive control signal is provided, the actuator 4 can be driven in consideration of the error component of the force measuring unit. become. That is, the active vibration isolation device of Embodiment 1 can exhibit as high a vibration isolation performance as possible.

  The load cell 5 as a force measuring unit includes a zero-point offset (offset error) and a fluctuation component due to temperature drift characteristics as an error component. Since the frequency component is configured to be compensated by the compensator 9, the offset is always offset even when the output signal of the load cell 5 includes an offset signal at no load or when the output signal changes due to changes in the ambient temperature environment. It is possible to obtain high vibration isolation performance from which changes in the output signal due to signals and temperature changes are removed.

Embodiment 2. FIG.
In the first embodiment, the configuration in which the filter 8 is applied to the output signal of the load cell 5 connected in series to the passive vibration isolator 1 and the actuator 4 is driven and controlled using the output signal of the filter 8 has been described. Without being limited to this, instead of the load cell 5, a relative displacement sensor that detects the relative displacement between the supported object 2 and the floor 3 may be used. According to this configuration, the force measuring unit calculates the force that the passive vibration isolator 1 receives from the supported object 2 and the floor 3 based on the output signal of the relative displacement sensor. Hereinafter, a configuration using a relative displacement sensor that detects a relative displacement between the supported object 2 and the floor 3 will be described. Since the configuration other than the configuration using a relative displacement sensor instead of the load cell 5 is the same as that of the first embodiment, the description is omitted.

Equation force F _L between passive vibration isolators 1 and the floor 3 for detecting a load cell 5 shown in (1), the relative displacement x _P -x of the supported object 2 and the floor 3 which is detected by the relative displacement sensor _{Using B} , calculation is performed as in Expression (7).

Here, the estimated value of F _LD is force was calculated from the relative displacement F _L, k _D is the design value of the rigidity of the elastic element 13, the c _D is a design value of the viscous damping coefficient of the damping element 14. If the real value of the stiffness and viscous damping coefficient of the damping element 14 of the elastic element 13 is in very good agreement with the design value, the force F _L to detect the load cell 5 as shown in Equation (1) , The force _FLD calculated from Equation (7) matches. However, in reality, it is very difficult to match the value of the viscous damping coefficient of the damping element 14 between the design value and the actual value with very high accuracy, and the value of the viscous damping coefficient is a value depending on the ambient temperature environment. Therefore, like the output signal of the load cell 5, the force _FLD calculated by the equation (7) has a DC offset error and a low frequency fluctuation error due to a temperature change with respect to the true value force. Therefore, when the configuration according to the second embodiment is not adopted, the vibration isolation performance is deteriorated due to the DC offset error and the low frequency fluctuation error due to the temperature change, similarly to the configuration using the load cell 5.

  Thus, when the force measuring unit is configured using a relative displacement sensor instead of the load cell 5, the output signal of the force measuring unit includes an offset error and a low frequency fluctuation error due to a temperature change as an error component. These error components are removed by the filter 8 as in the first embodiment, and the low-frequency components removed by the filter 8 are compensated by the compensator 9. Therefore, the active vibration isolation device of the second embodiment can exhibit as high a vibration isolation performance as possible as in the first embodiment.

  In addition, when the force measuring unit is configured using a relative displacement sensor, it is not necessary to connect the load cell 5 in series with the passive vibration isolator 1, so that the rigidity of the load cell 5 itself is the elasticity of the passive vibration isolator 1. There is an effect that it is possible to avoid a decrease in insulation performance that occurs when the rigidity of the element 13 is close.

Embodiment 3 FIG.
In the first and second embodiments, the configuration in which the compensator 9 and the controller 10 are applied to the output signal of the acceleration sensor 6 mounted on the supported object 2 has been described. A configuration in which acceleration information of the supported object 2 is detected using a single sensor or a plurality of sensors may be used. Specifically, supported information calculated by second-order time differentiation of information detected by an acceleration sensor mounted on the floor 3 and relative displacement between the supported object 2 detected by the relative displacement sensor and the floor 3. The acceleration information of the supported object 2 may be calculated from the relative acceleration information between the object 2 and the floor 3. Alternatively, instead of using a relative displacement sensor, the relative speed between the supported object 2 and the floor 3 detected by a relative speed sensor such as a geophone is differentiated by the first floor time, whereby the supported object 2 and the floor 3 can be differentiated. The relative acceleration information may be obtained. In this way, an acceleration sensor 6 is not mounted on the supported object 2 but an output signal equivalent to that obtained when the acceleration sensor 6 is mounted on the supported object 2 is obtained. When it is difficult to mount the sensor 6, there is an effect that the degree of freedom of sensor arrangement is increased at the time of design. In addition, when a precision device that dislikes minute heat generation is mounted on the supported object 2, there is an effect that it is possible to exclude the influence of heat generated by the acceleration sensor 6 on the precision device.

  As described above, the active vibration isolator according to the present invention is suitable for application to an active vibration isolator that suppresses transmission of vibration from a vibration source to a device that dislikes vibration.

DESCRIPTION OF SYMBOLS 1 Passive type vibration isolator 2 Supported object 3 Floor 4 Actuator 5 Load cell 6 Acceleration sensor 7 Drive driver 8 Filter 9 Compensator 10 Controller 11 Calculator 12 Gain 13 Elastic element 14 Damping element

Claims (4)

An active vibration isolator installed on the floor and supporting a supported object,
A passive vibration isolator disposed between the floor and the supported object to passively reduce vibration from the floor to the supported object;
A force measuring unit that measures a first force received by the passive vibration isolator in a direction in which the passive vibration isolator is disposed;
An acceleration measuring unit for measuring the acceleration of the supported object;
An actuator disposed in parallel with the passive vibration isolator between the floor and the supported object, and generating a second force in the disposed direction;
An actuator driving device for supplying a control signal to the actuator to drive the actuator so that the first force and the second force cancel each other;
With
The actuator driving device includes:
A high-pass filter for removing a low-frequency component including an error component of the output signal from the output signal of the force measuring unit;
A compensator that compensates for a low-frequency component removed by the high-pass filter based on an output signal of the acceleration measurement unit;
A controller that generates a control signal to be supplied to the actuator based on an output signal of the high-pass filter and an output signal of the compensator;
An active vibration isolator comprising: The force measuring unit is a load cell,
The error component of the output signal of the force measuring unit is a fluctuation component caused by an offset error or temperature drift characteristic of the load cell.
The active vibration isolator according to claim 1. The force measuring unit includes a relative displacement sensor that measures a relative displacement between the supported object and the floor, and a stiffness and a viscous damping coefficient of the passive vibration isolator used when calculating the first force. The first force is calculated based on the design value of and the output signal of the relative displacement sensor,
The error component of the output signal of the force measuring unit is a DC error between the design value of the stiffness and the viscous damping coefficient of the passive vibration isolator and the actual value of each, or a fluctuation component of the viscous damping coefficient due to a temperature change. is there,
The active vibration isolator according to claim 1. The acceleration measuring unit includes a relative displacement sensor that measures a relative displacement between the supported object and the floor, or a relative speed sensor that measures a relative speed between the supported object and the floor, Calculating an acceleration of the supported object based on an output signal of a displacement sensor or the relative velocity sensor;
The active vibration isolator according to any one of claims 1 to 3, wherein

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