JP7288841B2 - SENSOR SYSTEM AND VIBRATION ISOLATION DEVICE INCLUDING THE SENSOR SYSTEM - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a sensor system and a vibration isolator including the sensor system.

As disclosed in Patent Document 1, a so-called conductive velocity sensor (vibration sensor) outputs a signal indicating the jerk when the frequency is lower than the natural frequency of the detection coil, A signal indicating acceleration is output in the vicinity, and a signal indicating velocity is output when the frequency is higher than the natural frequency.

Patent Literature 2 discloses a sensor system to which such a conductive speed sensor is applied. The sensor system disclosed in Patent Document 2 includes a conductive speed sensor (geophone) and a signal processing section (filter chain) into which a signal output from the conductive speed sensor is input.

Here, the signal processing unit according to Patent Document 2 outputs a signal indicating acceleration by performing signal processing on the output signal of the conductive speed sensor. While the eigenfrequency exemplified in the document is 6 Hz, the signal processing section performs signal processing from 0.1 Hz to 100 Hz.

That is, the signal processing unit according to Patent Document 2 outputs a signal indicating acceleration not only near the natural frequency but also at least when it is sufficiently lower than the natural frequency and when it is sufficiently higher than the natural frequency. is configured to

JP-A-2003-66063 U.S. Pat. No. 5,832,806

As described in Patent Document 1, a general conductive speed sensor outputs a signal indicating jerk when the frequency is lower than the natural frequency, and the frequency is higher than the natural frequency. If so, it outputs a signal that indicates the speed.

Therefore, in order to output a signal indicating acceleration, the signal processing unit according to Patent Document 2 integrates the output signal at least for frequencies lower than the natural frequency, and integrates the output signal for frequencies higher than the natural frequency. Differentiate the output signal.

As a result of researching the sensor system disclosed in Patent Document 2, the inventors of the present application newly found that when the signal processing unit according to the document is used, the acceleration is not appropriately output near the natural frequency. rice field.

That is, as described above, the conductive velocity sensor outputs a signal indicating acceleration near the natural frequency. If the signal indicating acceleration is subjected to differentiation or integration processing, conversion that reflects the frequency characteristics unique to the conductive speed sensor will not be performed, and an error will occur in the vicinity of the natural frequency, which is inconvenient. be.

Therefore, in the configuration disclosed in Patent Document 2, as a result of reflecting the error that occurred near the natural frequency, when a signal indicating acceleration is to be output, the gain rises near the natural frequency. , the inventors of the present application have noticed.

As a result of further research, the inventors of the present application have found that there is a common problem when trying to output a signal indicating speed using the above-described sensor system.

That is, when a general conductive speed sensor is used, in order to output a signal indicating speed, the output signal of the conductive speed sensor must be double-integrated at least for frequencies lower than the natural frequency. become.

In this case, near the natural frequency, the signal indicating the acceleration is double-integrated with respect to the output. The inventors of the present application have noticed that

The technology disclosed herein has been made in view of this point, and its purpose is to convert the output signal of a conductive speed sensor into a specific physical quantity within a range that includes the natural frequency. It is in.

The present disclosure relates to sensor systems for detecting acceleration. This sensor system is modeled as a dynamic system having a case, a mass housed in the case and relatively displaceable with respect to the case, and a damper and a spring supporting the mass on the case. a conductive speed sensor that outputs a signal proportional to the relative speed between the mass body and the mass, and a signal that outputs a signal indicating the acceleration of the case by converting the signal output from the conductive speed sensor and a processing unit.

The signal processing unit has a differentiating circuit that differentiates a signal with a frequency higher than the natural frequency of the dynamic system and an integration circuit that integrates a signal with a lower frequency than the natural frequency, which are connected in series. In addition, the signal processing unit is further connected in series with a gain suppression circuit that suppresses the gain at the natural frequency.

According to the knowledge obtained as a result of intensive studies by the inventors of the present application, by suppressing the gain at the natural frequency by the gain suppressing circuit, it is possible to remove the rise in the gain near the natural frequency. As a result, the output signal of the conductive speed sensor is converted into the acceleration of the case within a relatively wide range including the natural frequency (especially the practical range when using the conductive sensor as an acceleration sensor). be able to. By attaching the case to a predetermined detection target (for example, a vibration isolation target), the acceleration of the detection target can be detected through the case.

Further, the transfer function F ₁ (s) of the differentiating circuit is expressed as follows, where s is the Laplace operator and T ₁ is the phase lead time constant:
F ₁ (s)=(1+T ₁ s)/(1+αT ₁ s) where α<1 (A)
and _the transfer function F ₂ (s) of the integration circuit is given by
F ₂ (s)=β(1+T ₂ s)/(1+βT ₂ s) where β>1 (B)
and the natural frequency is ω ₀ , the phase lead time constant, the phase lag time constant and the natural frequency are:
(βT ₂ ) ⁻¹ <ω ₀ <(αT ₁ ) ⁻¹ (C)
satisfies the relationship of

According to the above formula (C), the natural frequency can be set so as to fall within the range in which the integration process and the differentiation process are performed.

Further, the phase lead time constant, the phase lag time constant and the natural frequency are
(β ^0.5 T ₂ ) ⁻¹ <ω ₀ <(α ^0.5 T ₁ ) ⁻¹ (D)
satisfies the relationship of

According to the above formula (D), the frequency at which the phase on the integral side lags the most (the frequency at which the phase reaches its minimum value) is shifted to the frequency at which the phase on the differentiation side reaches its maximum value (the frequency at which the phase reaches its maximum value). ), the natural frequency can be set.

The present disclosure also relates to a sensor system for detecting absolute velocity. This sensor system is modeled as a dynamic system having a case, a mass housed in the case and relatively displaceable with respect to the case, and a damper and a spring supporting the mass on the case. and a conductive speed sensor that outputs a signal proportional to the relative speed between the mass body and the mass body; and a signal that indicates the absolute speed of the case by converting the signal output from the conductive speed sensor. and a signal processing unit.

The signal processing unit has a double integration circuit that double integrates a signal having a frequency smaller than the natural frequency of the dynamic system and a gain suppression circuit that suppresses a gain at the natural frequency, which are connected in series. It becomes

According to the knowledge obtained as a result of intensive studies by the inventors of the present application, by suppressing the gain at the natural frequency by the gain suppressing circuit, it is possible to remove the rise in the gain near the natural frequency. As a result, the output signal of the conductive speed sensor is converted to the absolute speed of the case within a relatively wide range including the natural frequency (especially the practical range for using the conductive sensor as a speed sensor). can do. By attaching the case to a predetermined detection target (for example, a vibration isolation target), the absolute velocity of the detection target can be detected through the case.

Also, the transfer function F ₃ (s) of the double integration circuit is given by the following when the phase delay time constant is T ₃
F ₃ (s)={γ(1+T ₃ s)/(1+γT ₃ s)} ² where γ>1 (E)
is represented by
Assuming that the natural frequency is ω ₀ , the phase delay time constant and the natural frequency are
(γT ₃ ) ⁻¹ < ω ₀ (F)
satisfies the relationship of

According to the above formula (F), it is possible to perform double integration processing on a signal whose frequency is smaller than the natural frequency.

Further, the phase delay time constant and the natural frequency are
(γ ^0.5 T ₃ ) ⁻¹ <ω ₀ (G)
satisfies the relationship of

According to the above formula (G), the natural frequency can be set within a range exceeding the frequency at which the phase on the integral side is delayed the most (the frequency at which the phase reaches its minimum value).

Further, the gain suppression _circuit is composed of a notch filter _, and the transfer function F _n (s) of the notch filter is given by
F _n (s)=(s ² +2ζ ₁ ω ₀ s+ω ₀ ² )/(s ² +2ζ ₂ ω ₀ s+ω ₀ ² ) where ζ ₁ <ζ ₂ (H)
may be represented by

Equation (H) above is advantageous in appropriately configuring the gain suppression circuit and thus in detecting the acceleration or absolute acceleration of the case.

A resistor may be connected between the positive and negative terminals of the conductive speed sensor.

The present disclosure also relates to a vibration isolator comprising said sensor system. This vibration isolator includes the sensor system, a vibration isolation object to which the case is attached and which vibrates integrally with the case, an actuator for applying a control force or displacement to the vibration isolation object, and the sensor system. an actuator control unit configured to control the actuator so as to suppress vibration of the object to be vibration-isolated, based on a signal output from the .

As described above, according to the sensor system and the vibration isolator, the output signal of the conductive velocity sensor can be converted into a specific physical quantity within the range including the natural frequency.

FIG. 1 is a schematic diagram illustrating the configuration of the vibration isolator according to the first embodiment. FIG. 2 is a schematic diagram illustrating the configuration of the sensor system according to the first embodiment. FIG. 3 is a diagram illustrating frequency characteristics of a geophone. FIG. 4 is a diagram illustrating frequency characteristics of a phase lead compensator and a phase lag compensator. FIG. 5 is a diagram illustrating frequency characteristics of a gain suppression circuit. FIG. 6 is a diagram illustrating acceleration-frequency characteristics of signals output from the phase lead compensator and the phase lag compensator. FIG. 7 is a diagram illustrating acceleration-frequency characteristics of signals output from the phase lead compensator and the phase lag compensator via the gain suppression circuit. FIG. 8 is a schematic diagram illustrating the configuration of a vibration isolator according to the second embodiment. FIG. 9 is a schematic diagram illustrating the configuration of the sensor system according to the second embodiment. FIG. 10 is a diagram exemplifying the frequency characteristic with respect to the absolute velocity of the signal output from the double integration circuit. FIG. 11 is a diagram exemplifying the frequency characteristic with respect to the absolute velocity of the signal output from the double integration circuit via the gain suppression circuit.

Hereinafter, embodiments of the present disclosure will be described based on the drawings. Note that the following description is an example.

In this specification, a first embodiment of a sensor system 100 for detecting acceleration and a second embodiment of a sensor system 100' for detecting absolute velocity will be described in turn.

<First embodiment>
First, the first embodiment will be explained. In the following description, "first embodiment" may be simply referred to as "this embodiment".

(Overall Configuration of Vibration Isolator)
FIG. 1 is a diagram illustrating the configuration of a vibration isolator A according to the first embodiment. This vibration isolator A is equipped with a device D comprising a semiconductor inspection device, an electron microscope, an optical measuring device, etc., and isolates the device D from vibration.

Specifically, the vibration isolator A includes a vibration isolation table 1 mounted with a device D to isolate it from vibration, a geophone 2 detecting vibration in the vibration isolation table 1, and a detection signal ( and a controller 4 for controlling the actuator 13 in the vibration isolator A based on the signal output from the acceleration conversion circuit 3. and have. The geophone 2 and the acceleration conversion circuit 3 constitute a sensor system 100 which will be described later.

Specifically, the vibration isolation table 1 includes a support table 10 on which the device D is mounted, an elastic member 11 and a damper 12 that support the support table 10 with respect to an installation surface F such as a floor surface, and the support table 10. and an actuator 13 for applying force or displacement. Although omitted in FIG. 1, a plate-like foundation may be provided between the elastic body 11, the damper 12, the actuator 13, and the installation surface F.

Among them, the support base 10 is formed as a rectangular thick plate and forms a so-called platen. The above-described device D is placed on the upper surface of the support table 10 . As a result, the support base 10 and the device D vibrate substantially integrally. Therefore, by attenuating or canceling the shaking that occurs in the support base 10, the device D placed on the support base 10 can be insulated from the vibration. The support table 10 is an example of the "object to be isolated" in this embodiment.

A geophone 2 constituting a sensor system 100 described later, specifically, a case 21 of the geophone 2 is attached to the support base 10 as an object to be vibration-isolated. As a result, the support base 10 according to this embodiment vibrates together with the case 21 .

The elastic body 11 is arranged on the installation surface F and configured to support the support base 10 from below. The elastic body 11 according to this embodiment is composed of a spring element that elastically deforms in the vertical direction. The elastic body 11 made of a spring element receives a load from the device D placed on the support base 10 and the support base 10 itself, and elastically deforms according to the spring constant.

Although only one elastic body 11 is illustrated in FIG. 1, a plurality of elastic bodies 11 may be provided. When a plurality of elastic bodies 11 are provided, for example, they can be arranged so as to support the four corners of the support base 10 from below.

The damper 12 is arranged on the installation surface F and configured to be connected to the support base 10 from below. The damper 12 according to this embodiment consists of a sliding member that expands and contracts while sliding in the vertical direction. The damper 12 made of a sliding member damps vibration according to the damping ratio when the device D placed on the support base 10 and the support base 10 itself vibrate substantially together. Let In addition, the structure using a sliding member as the damper 12 is only an example. For example, when an air spring is used as the elastic body 11 , an orifice provided in the air spring functions as the damper 12 .

Although only one damper 12 is illustrated in FIG. 1, a plurality of dampers 12 may be provided as in the elastic body 11. FIG. When a plurality of dampers 12 are provided, for example, they can be arranged so as to support the four corners of the support base 10 from below.

The actuator 13 is arranged on the installation surface F and configured to be connected to the support base 10 from below. The actuator 13 according to this embodiment is composed of a linear motor that applies a control force to the support base 10 as an object to be vibration-isolated. An actuator 13 made up of a linear motor applies a control force to the support base 10 based on a signal output from the controller 4 .

(Configuration related to control system)
Following the overall configuration of the vibration isolator A, the configuration related to the sensor system 100 will be described below. FIG. 2 is a schematic diagram illustrating the configuration of the sensor system 100 according to the first embodiment, and FIG. 3 is a diagram illustrating frequency characteristics of the geophone 2. As shown in FIG. 4 is a diagram illustrating frequency characteristics of the phase lead compensator 32 and the phase lag compensator 33, and FIG. 5 is a diagram illustrating frequency characteristics of the gain suppressing circuit 34. As shown in FIG.

As described above, the sensor system 100 according to this embodiment includes the geophone 2 attached to a predetermined detection target (the support base 10 in this embodiment), and the acceleration conversion circuit 3 to which the detection signal of the geophone 2 is input. and have. The acceleration conversion circuit 3 converts the detection signal of the geophone 2 into acceleration and inputs it to the controller 4 . The acceleration conversion circuit 3 is an example of the "signal processing section" in this embodiment. Also, the controller 4 is an example of the “actuator control unit” in this embodiment.

The geophone 2 is a so-called geophone and consists of a conductive velocity sensor. The geophone 2 can detect motion of a detection target, convert the motion into a voltage, and output the voltage.

More specifically, the geophone 2 includes a case 21, a mass body 22 housed in the case 21 and relatively displaceable with respect to the case 21, and the mass body 22 supported by the case 21 (in particular, relatively displaceable). is modeled as a dynamical system having a damper 23 and a spring 24 (supported by ). The dampers 23 and the springs 24 can be configured using leaf springs for supporting the mass body 22 on the case 21, for example. The geophone 2 so modeled outputs a signal proportional to the relative velocity between the case 21 and the mass 22, as described below.

That is, the geophone 2 configured as a conductive velocity sensor normally includes a coil 25 provided on one of the case 21 and the mass body 22 and a magnet 26 provided on the other of the case 21 and the mass body 22. , will be further provided.

In particular, the geophone 2 according to the present embodiment is fixed to the inner bottom surface of a substantially cylindrical case 21, and includes a magnet 26 having an N pole and an S pole arranged side by side along the longitudinal direction of the case 21, and a mass and a coil 25 wound around the outer peripheral surface of the body 22 and displaced integrally with the mass body 22. When the mass body 22 is displaced relative to the case 21, the magnet 26 The coil 25 reciprocates along the direction in which the N and S poles are arranged. When the coil 25 reciprocates in this manner, the magnet 26 is relatively displaced on the inner peripheral side of the coil 25, and an induced electromotive force is generated by electromagnetic induction. Geophone 2 outputs a voltage corresponding to the induced electromotive force as a detection signal.

Here, the terminals for the geophone 2 to output the detection signal may be, for example, two positive and negative terminals as shown in FIG. In that case, one of the two terminals may be grounded and the other may be connected to the acceleration conversion circuit 3, or both of the two terminals may be connected to the acceleration conversion circuit 3 to form a so-called differential input.

Moreover, as illustrated in FIG. 2, a resistor 27 can be connected between the positive and negative terminals provided on the geophone 2 . In this case, an electromagnetic force is generated by the detection signal output from the geophone 2 flowing through the resistor 27 . This electromagnetic force can attenuate the relative displacement of the mass body 22 with respect to the case 21 . Normally, the damping ratio ζ when the geophone 2 is modeled is determined from the physical properties of the plate springs and the like that constitute the damper 23, but in reality the damping due to the current flowing through the coil 25 also affects.

By providing the geophone 2 with the resistor 27 as in this embodiment, the influence of the resistor 27 can be added to the internal resistance of the coil 25 . Thereby, the damping ratio ζ can be adjusted to a desired value. Note that the provision of the resistor 27 itself is not essential.

When the resistor 27 is connected to the geophone 2, the voltage indicating the detection signal is reduced because the voltage is divided between the internal resistance of the coil 25 and the resistor 27. FIG.

Let ε be the induced electromotive force, B be the magnetic flux density of the magnet 26, l be the coil length of the coil 25, and _vr be the relative velocity of the coil 25. Then, the following equation holds.

ε= _Blvr (1)

Thus, the geophone 2 outputs a detection signal proportional to the relative velocity of the coil 25 with respect to the magnet 26 , that is, the relative velocity between the case 21 and the mass body 22 .

On the other hand, by modeling the geophone 2 as a dynamic system, the relative velocity between the case 21 and the mass body 22 can be associated with the acceleration of the case 21 itself. Therefore, the relationship between the induced electromotive force generated in the geophone 2 and the acceleration of the case 21 itself can be obtained through the relative velocity of the coil 25 . By using the relationship thus obtained, the acceleration of the case 21 itself can be obtained based on the detection signal output from the geophone 2 .

Specifically, the mass of the mass body 22 is m, the damping coefficient of the damper 23 is c, the spring constant of the spring 24 is k, the displacement of the case 21 is _xc , the displacement of the mass body 22 is _xm , Assuming that the relative displacement of the mass body 22 with respect to the case 21 is x _r (=x _m −x _c ), the equation of motion of the mass body 22 is given by the following equation (2).

_mxm ''+ _cxr '+ _kxr =0 (2)

In equation (2), the double prime indicates the second derivative with respect to time, and the single prime indicates the first derivative with respect to time.

By substituting _xm = _xr + _xc in equation (2) and arranging by Laplace transform, the following equation (3) is obtained.

X _r =[(cs+k)·(ms ² +cs+k) ⁻¹ −1]·X _c
=-ms ² (ms ² +cs+k) ^-1 X _c (3)

In equation (3), s is the Laplace operator, _Xc is the Laplace transform of _xc , and _Xr is the Laplace transform of _xr . Furthermore, when the natural frequency of the dynamic system is _ω0 and the damping ratio is ζ, the following equations (4) to (6) are obtained from the above equation (3).

X _r =−s ² ·(s ² +2ζω ₀ s+ω ₀ ² ) ⁻¹ ·X _c (4)
ω ₀ = (k/m) ^0.5 (5)
ζ=c/[2·(mk) ^0.5 ] (6)

As described above, ζ, which indicates the damping ratio, is a magnitude that takes into consideration the mechanical characteristics of the plate springs and the like that constitute the damper 23 and the electrical characteristics that result from the resistor 27 . By providing the resistor 27, the attenuation ratio is increased.

Here, since the relative velocity of the coil 25 with respect to the magnet 26 is equal to the relative velocity of the mass body 22 with respect to the case 21, _vr in Equation (1) can be said to be equal to the time derivative of _xr in Equation (2). . Therefore, if the Laplace transform of _vr is _Vr and the Laplace transform of ε indicating the induced electromotive force is E, the following formula (7) is obtained from the formulas (1) and (4).

E= _BlVr
=−Bls ³ ·(s ² +2ζω ₀ s+w ₀ ² ) ⁻¹ ·X _c (7)

Here, when the absolute velocity of the case 21 itself in the s-space is _A1 , the acceleration is _A2 , and the jerk is _A3 , the following expressions (8) to (10) are obtained from the expression (7).

E=−Bls ² ·(s ² +2ζω ₀ s+ω ₀ ² ) ⁻¹ A ₁ (8)
=-Bls (s ² +2ζω ₀ s+ω ₀ ² ) ⁻¹ A ₂ (9)
=−Bl(s ² +2ζω ₀ s+ω ₀ ² ) ⁻¹ A ₃ (10)

Assuming that the frequency of the dynamic system is ω(=-is), the following equations (11)-(13) are obtained based on each of equations (8)-(10).

E/A ₁ =−Bl ω>>ω ₀ (11)
E/A ₂ =-Bl/(2ζω ₀ ) ω ~ ω ₀ (12)
E/A ₃ =−Bl/ω ₀ ² ω<ω ₀ (13)

For example, formula (11) means that the ratio of the detected signal (induced electromotive force) to the absolute velocity of the case 21 itself is constant when the frequency is sufficiently higher than the natural frequency. (See top of Figure 3). In this case, by calculating the ratio in advance, the absolute velocity of the case 21 itself can be detected based on the detection signal output from the geophone 2 .

In addition, equation (12) means that the ratio of the detection signal to the acceleration of the case 21 itself is constant when the frequency is near the natural frequency (see the central diagram in FIG. 3). ). In this case, the acceleration of the case 21 itself can be detected based on the detection signal output from the geophone 2 . Also, as is clear from Equation (12), the magnitude of the gain at the natural frequency is inversely proportional to the magnitude of the damping ratio. Therefore, by providing the geophone 2 with the resistor 27 as described above, the damping ratio can be amplified, and the magnitude of the gain at the natural frequency can be suppressed. In addition to simply suppressing the magnitude of the gain, it is also possible to gently change the slope of the gain near the natural frequency.

Further, equation (13) means that the ratio of the detection signal to the jerk of the case 21 itself becomes constant when the frequency is sufficiently smaller than the natural frequency (see FIG. 3). (see figure below). In this case, the jerk of the case 21 itself can be detected based on the detection signal output from the geophone 2 .

In this way, the geophone 2 configured as a conductive velocity sensor detects the absolute velocity of the case 21 itself or the acceleration depending on the magnitude relationship between the frequency of the dynamic system and the natural frequency. , jerk can be detected.

Here, the inventors of the present application have searched for a configuration that detects acceleration within a wide range including the natural frequency while using the geophone 2 having the characteristics described above. However, as is clear from the functional form of Equation (9), the value of the ratio of the dielectric electromotive force to the acceleration does not become constant when the frequency deviates from the natural frequency.

That is, the value of the ratio of the dielectric electromotive force to the acceleration draws a curve with the natural frequency as the maximum value. is greater than the natural frequency, it will monotonically decrease as the frequency increases.

Therefore, simply obtaining the value of the ratio is inconvenient for obtaining the acceleration.

Therefore, it is conceivable to integrate the detection signal of the geophone 2 with respect to frequencies lower than the natural frequency, and differentiate the detection signal of the geophone 2 with respect to frequencies higher than the natural frequency.

However, as described above, the geophone 2 will output a signal indicating acceleration near the natural frequency. If a signal indicating acceleration is subjected to differentiation or integration processing, conversion that reflects the frequency characteristics unique to the geophone 2 will not be performed, and an error will occur in the vicinity of the natural frequency, which is inconvenient. .

The inventors of the present application have noticed that the gain rises near the natural frequency when outputting a signal indicating acceleration as a result of reflecting the error that occurred near the natural frequency (the solid line in FIG. 6). see also). In other words, it is not possible to obtain the acceleration near the natural frequency, which is the boundary between the two processes, only by the differentiation process and the integration process.

As a result of extensive studies, the inventors of the present application newly created an acceleration conversion circuit 3 that can obtain the acceleration of the case 21 within a range including the natural frequency.

Specifically, the acceleration conversion circuit 3 as a signal processing unit in this embodiment converts the detection signal output from the geophone 2 to output a signal indicating the acceleration of the case 21 . The acceleration conversion circuit 3 includes a phase lead compensator 32 for differentiating a signal with a higher frequency than the natural frequency of the dynamic system, a phase lag compensator 33 for integrating a signal with a lower frequency than the natural frequency, connected.

In other words, the acceleration of the case 21 itself can be obtained at a frequency that is away from the natural frequency on the high frequency side or on the low frequency side. As a result, the geophone 2 can be used as an acceleration sensor at a frequency that is away from the natural frequency on the higher side or the lower side.

On the other hand, when the frequency is near the natural frequency, there is concern about the increase in gain as described above. Therefore, the acceleration conversion circuit 3 is further connected in series with a gain suppression circuit 34 that suppresses the gain at the natural frequency. As a result, the increase in gain near the natural frequency is removed, and the geophone 2 can be used as an acceleration sensor even at frequencies near the natural frequency.

A specific configuration of the acceleration conversion circuit 3 will be described in order below.

As shown in FIG. 2, the acceleration conversion circuit 3 includes an amplifier 31 that amplifies the detection signal of the geophone 2, a phase lead compensator 32 that receives the amplified detection signal from the amplifier 31, and a phase lead compensator 32 A phase lag compensator 33 to which the detection signal passed through the phase lag compensator 33 is input, a gain suppression circuit 34 to which the detection signal that has passed through the phase lag compensator 33 is input, and a voltage for canceling the offset voltage contained in the detection signal. and an offset circuit 35 for generating .

Among them, the phase lead compensator 32 performs differentiation processing on the detection signal amplified by the amplifier 31 . Specifically, the phase lead compensator 32 performs differentiation processing on a certain frequency range of the detection signal amplified by the amplifier 31 . The phase lead compensator 32 is an example of the "differentiation circuit" in this embodiment.

More specifically, the transfer function F ₁ (s) of the phase lead compensator 32 is expressed as follows, where s is the Laplace operator and T ₁ is the phase lead time constant:
F ₁ (s)=(1+T ₁ s)/(1+αT ₁ s) where α<1 (14)
can be represented by In this case, the breakpoint frequencies of phase lead compensation are (T ₁ ) ⁻¹ and (αT ₁ ) ⁻¹ in order from the low frequency side. As a result, the signal within the band from (T ₁ ) ⁻¹ to (αT ₁ ) ⁻¹ can be differentiated, as illustrated in the upper part of FIG. Signals outside this band are not substantially differentiated. Further, the frequency at which the phase advances to the maximum in phase advance compensation (the frequency at which the phase reaches its maximum value) is (α ^0.5 T ₁ ) ⁻¹ . In the actual phase lead compensator 32, the transfer function F ₁ (s) does not bend at the break point frequency (does not form an obtuse angle) and curves slightly gently.

Also, the phase lag compensator 33 integrates the detection signal differentiated by the phase lead compensator 32 . Specifically, the phase delay compensator 33 performs integration processing on a certain frequency range of the detection signal differentiated by the phase lead compensator 32 . The phase delay compensator 33 is an example of the "integration circuit" in this embodiment.

More specifically, the transfer function F ₂ (s) of the phase lag compensator 33 is given by the following, where T ₂ is the phase lag time constant:
F ₂ (s)=β(1+T ₂ s)/(1+βT ₂ s) where β>1 (15)
can be represented by In this case, the breakpoint frequencies of phase delay compensation are (βT ₂ ) ⁻¹ and (T ₂ ) ⁻¹ in order from the low frequency side. As a result, signals within the band from (βT ₂ ) ⁻¹ to (T ₂ ) ⁻¹ can be integrated, as illustrated in the middle of FIG. Signals outside this band are substantially not integrated. Further, the frequency at which the phase is delayed to the maximum in phase delay compensation (the frequency at which the phase reaches a minimum value) is (β ^0.5 T ₂ ) ⁻¹ . In the actual phase delay compensator 33, the transfer function F ₂ (s) does not bend at the break point frequency (does not form an obtuse angle) and curves slightly gently.

In addition, in order for the phase lead compensator 32 to differentiate a signal with a higher frequency than the natural frequency and for the phase lag compensator 33 to integrate a signal with a lower frequency than the natural frequency, the lower part of FIG. As exemplified in , the phase lead time constant, phase lag time constant and natural frequency are
(βT ₂ ) ⁻¹ <ω ₀ <(αT ₁ ) ⁻¹ (16)
It is required to satisfy the relationship of In particular, the phase lead time constant, phase lag time constant and natural frequency according to this embodiment are
(β ^0.5 T ₂ ) ⁻¹ <ω ₀ <(α ^0.5 T ₁ ) ⁻¹ (17)
is set to satisfy the relationship of

Also, the gain suppression circuit 34 is configured by a notch filter. _The transfer function F _n (s) _of this notch filter is given by
F _n (s)=(s ² +2ζ ₁ ω ₀ s+ω ₀ ² )/(s ² +2ζ ₂ ω ₀ s+ω ₀ ² ) where ζ ₁ <ζ ₂ (18)
can be represented by

The damping ratios ζ ₁ and ζ ₂ of the notch filters are such that the gain of the signal output from the geophone 2 and passed through the phase lead compensator 32 , the phase lag compensator 33 and the gain suppression circuit 34 is It is set so as to be approximately constant.

Preferably, the half width of gain suppression circuit 34 as a notch filter is narrower than the band in which phase lead compensator 32 and phase lag compensator 33 respectively perform differentiation and integration. That is, assuming that the half width of the gain suppression circuit 34 is 2Δω, as illustrated in FIG.
(βT ₂ ) ⁻¹ <ω ₀ −Δω<ω ₀ <ω ₀ +Δω<(αT ₁ ) ⁻¹ (19)
It is preferable to satisfy the relationship of

Also, in general, there is a possibility that an offset voltage will be generated due to the fact that the gain of the amplifier 31 is high and the detection signal has passed through the phase lead compensator 32, the phase lag compensator 33 and the gain suppression circuit 34. be. In order to solve this problem, it is conceivable to provide a high-pass filter, for example, but the high-pass filter advances the phase at frequencies below its cutoff frequency, so it is not desirable from the viewpoint of stable control. Therefore, the DC voltage generated in the offset circuit 35 cancels out the offset voltage in the detection signal output from the gain suppression circuit 34 . This makes it possible to avoid the influence of the offset voltage while stabilizing the control.

A detection signal output from the acceleration conversion circuit 3 in the sensor system 100 indicates the acceleration of the case 21 within a relatively wide range including the natural frequency. This detection signal is input to the controller 4 as an actuator control section. Based on the detection signal output from the sensor system 100, the controller 4 controls the actuator 13 so as to suppress the vibration of the support table 10 as an object to be vibration-isolated.

A specific configuration of the controller 4 will be described in order below.

As shown in FIG. 2, the controller 4 according to this embodiment includes an amplifier 41 that amplifies the signal output from the acceleration conversion circuit 3, and an A/D converter 42 that converts the signal amplified by the amplifier 41 into a digital signal. , an integrator 43 to which the signal converted by the A/D converter 42 is input, a gain multiplier 44 that determines the feedback operation amount of the actuator 13 based on the signal processed by the integrator 43, and a digital signal as It has a D/A converter 45 that converts the determined feedback manipulated variable into an analog signal again, and an amplifier 46 that amplifies the feedback manipulated variable converted by the D/A converter 45 .

Specifically, the A/D converter 42 is a so-called analog-to-digital converter, and performs sampling processing on the detection signal amplified by the amplifier 41 to convert the detection signal into a digital signal.

Also, the integrator 43 and the gain multiplier 44 integrate the detection signal indicating the acceleration of the support base 10 and then multiply it by the gain Gc to generate a digital signal indicating the feedback manipulated variable.

The D/A converter 45 is a so-called digital-analog converter that processes the feedback manipulated variable generated by the integrator 43 and the gain multiplier 44 to convert it into an analog signal.

The controller 4 inputs the feedback manipulated variable thus converted into an analog signal to the actuator 13 to operate the actuator 13 . As a result, the actuator 13 applies a control force to the support base 10 that corresponds to the feedback operation amount. The control force thus applied is proportional to the absolute velocity of the support base 10 and functions as a skyhook damper in the vibration isolator A. Thereby, the vibration of the support base 10 can be suppressed.

(Specific example of sensor system)
FIG. 6 is a diagram illustrating acceleration-frequency characteristics of signals output from the phase lead compensator 32 and the phase lag compensator 33. FIG. 4 is a diagram exemplifying a frequency characteristic of a signal output via a suppression circuit 34 with respect to acceleration; FIG. Here, ω ₀ in FIGS. 6 and 7 refers to the natural frequency of geophone 2 .

FIG. 6 illustrates the effects of the phase lead compensator 32 and the phase lag compensator 33 on the detection signal of the geophone 2 . Here, as shown by the two-dot chain line in FIG. 6, the frequency characteristics of the detection signal before filtering (the detection signal before passing through the phase lead compensator 32 and the phase lag compensator 33) are the same as those in the center diagram of FIG. Similarly, draw a mountain-like curve that becomes maximum at the natural frequency.

On the other hand, as shown by the dashed line in FIG. 6, the frequency characteristic of the analog filter composed of the phase lead compensator 32 and the phase lag compensator 33 follows the functional form of the transfer function F ₁ (s) and the transfer function F ₂ (s). , draws a valley-like curve that is minimized at the natural frequency.

In the example shown in FIG. 6, when the frequency is smaller than the breakpoint frequency (=(βT ₂ ) ⁻¹ ) on the low-frequency side in phase delay compensation (in the example shown in the figure, the magnitude of the frequency is the natural vibration ω ₀ ), and when the frequency is greater than the breakpoint frequency (=(αT ₁ ) ⁻¹ ) on the high-frequency side in phase lead compensation (in the example shown in the figure, the frequency is is about 100 times the natural frequency _ω0 ), the frequency characteristic of the analog filter becomes substantially constant with respect to the increase and decrease of the frequency.

Also, in the example shown in FIG. 6, the phase lead time constant, the phase lag time constant and the natural frequency are
(T ₁ ) ⁻¹ =(T ₂ ) ⁻¹ =ω ₀ (20)
is set to satisfy the relationship of By setting in this way, the breakpoint frequency (=(T ₂ ) ⁻¹ ) on the high side in phase delay compensation and the breakpoint frequency (=(T 1 ⁾ ₋₁ ) on the low side in phase lead compensation ¹ ) and the natural frequency (=ω ₀ ) match.

Then, the detection signal output from the geophone 2 and passed through the phase lead compensator 32 and the phase lag compensator _{33 is} , as shown by the solid line in FIG. At frequencies farther away from each other, the line becomes substantially constant with respect to the increase and decrease of the frequency. In this case, the ratio between the detection signal that has passed through the phase lead compensator 32 and the phase lag compensator 33 and the case 21 in the geophone 2 and the acceleration of the support base 10 to which the case 21 is attached becomes constant. It becomes possible to use the device 2 as an acceleration sensor.

However, in the detection signal that has passed through the phase lead compensator 32 and the phase lag compensator 33, the gain rises at frequencies near the natural frequency. In this case, the geophone 2 cannot be used as an acceleration sensor. As already explained, the gain swell problem can be solved by the gain suppression circuit 34 configured as a notch filter.

FIG. 7 illustrates the effects of the phase lead compensator 32, the phase lag compensator 33, and the gain suppression circuit 34 on the detection signal of the geophone 2. FIG. Specifically, as indicated by the relatively narrow two-dot chain line in FIG. 7, the frequency characteristic of the gain suppression circuit 34 is such that the gain is suppressed in the vicinity of the natural frequency. Draw a curved line.

By passing the detection signal of the geophone 2 through the phase lead compensator 32 and the phase lag compensator 33 as well as the gain suppression circuit 34, the gain rise near the natural frequency is removed. As shown by the solid line in FIG. 7, the signal output from the gain suppression circuit 34 becomes a substantially constant straight line with respect to increases and decreases in the frequency over a relatively wide band including the natural frequency. As a result, the geophone 2 can be used as an acceleration sensor within the range including the natural frequency.

(Effect of the sensor system according to the first embodiment)
As described above, by suppressing the gain at the natural frequency by the gain suppressing circuit 34, as shown in FIG. 7, the rise of the gain near the natural frequency can be removed. Thereby, the output signal of the geophone 2 can be converted into the acceleration of the case 21 within a relatively wide range including the natural frequency. By attaching the case 21 to a predetermined detection target (for example, a vibration isolation target), the acceleration of the detection target can be detected through the case 21 .

In addition, in this embodiment, by providing the resistor 27 in the geophone 2, the magnitude of the gain at the natural frequency (especially the magnitude of the maximum value in the central diagram of FIG. 3) is suppressed, and the natural frequency It is configured to gently change the slope of the gain in the vicinity. By configuring in this way, damping can be applied to the motion of the mass body 22, and collision between the mass body 22 and the case 21 can be suppressed when a relatively large vibration occurs.

In addition, by gently changing the slope of the gain, the magnitude of the output from the geophone 2 can be suppressed. As a result, the output does not become excessively large when vibration near the natural frequency is input. This is advantageous in protecting the electric circuit.

<Second embodiment>
Next, a second embodiment will be described. In the following description, "second embodiment" may be simply referred to as "this embodiment". It should be noted that the description of the configuration common to the first embodiment will be omitted as appropriate.

(Overall Configuration of Vibration Isolator)
FIG. 8 is a diagram illustrating the configuration of a vibration isolator A' according to the second embodiment. This vibration isolator A' is for isolating the device D from vibrations, as in the first embodiment.

The vibration isolation table 1 includes a support table 10 on which the device D is mounted, an elastic body 11 and a damper 12 that support the support table 10, and an actuator 13 that applies a control force or a displacement force to the support table 10. there is

Of these, the support base 10 as a vibration isolation object is attached with the geophone 2 forming the sensor system 100' in the second embodiment, specifically, the case 21 of the geophone 2. As shown in FIG. As a result, the support base 10 according to this embodiment vibrates integrally with the device D and the case 21 .

Further, the actuator 13 according to the second embodiment is composed of a linear motor that applies a control force to the support base 10 as in the first embodiment. An actuator 13 made up of a linear motor applies a control force to the support base 10 based on a signal output from the controller 4'.

(Configuration related to control system)
Following the overall configuration of the vibration isolator A', the configuration related to the sensor system 100' will be described. FIG. 9 is a schematic diagram illustrating the configuration of a sensor system 100' according to the second embodiment.

Specifically, the sensor system 100' according to the second embodiment is configured to convert the detection signal of the geophone 2 attached to a predetermined detection target (support base 10 in the present embodiment) and the geophone 2. and a velocity conversion circuit 3' configured to detect the absolute velocity of the object to be detected.

The configuration of the geophone 2 is similar to that of the first embodiment. For example, as shown in the above formula (11), when the frequency is sufficiently greater than the natural frequency, the absolute velocity of the case 21 itself is detected based on the detection signal output from the geophone 2. be able to. Also, similarly to the first embodiment, a resistor 27 can be connected between the positive and negative terminals provided on the geophone 2 .

Here, the inventors of the present application have searched for a configuration that detects the absolute velocity within a wide range including the natural frequency while using the geophone 2 having the characteristics described above. However, as is clear from the functional form of equation (8), the value of the ratio of the induced electromotive force to the absolute velocity is not constant when the frequency is smaller than the natural frequency.

In other words, the value of the ratio of the dielectric electromotive force to the absolute velocity becomes almost constant as the frequency increases when the frequency is greater than the natural frequency, but when the frequency is smaller than the natural frequency, It increases monotonously as it increases.

Therefore, simply obtaining the value of the ratio is inconvenient for obtaining the absolute velocity.

Therefore, it is conceivable to double-integrate the detection signal of the geophone 2 for frequencies lower than the natural frequency.

However, as described above, the geophone 2 will output a signal indicating acceleration near the natural frequency. If a signal indicating acceleration is subjected to double integration processing, conversion that reflects the frequency characteristics unique to the geophone 2 will not be performed, and an error will occur near the natural frequency, which is inconvenient. .

The inventors of the present application have noticed that, as a result of reflecting the error that occurred near the natural frequency, when trying to output a signal indicating the absolute velocity, the gain rises near the natural frequency (see FIG. 10). See also solid line). That is, the absolute velocity cannot be obtained in the vicinity of the natural frequency, which is the boundary of the process, only by the double integration process.

As a result of extensive studies, the inventors of the present application newly created a velocity conversion circuit 3' that can obtain the absolute velocity of the case 21 within a range including the natural frequency.

Specifically, the speed conversion circuit 3 ′ as a signal processing unit in this embodiment converts the detection signal output from the geophone 2 to output a signal indicating the absolute speed of the case 21 . The velocity conversion circuit 3' includes a double integration circuit 33' that double integrates a signal whose frequency is smaller than the natural frequency of the dynamic system, a gain suppression circuit 34' that suppresses the gain at the natural frequency, are connected in series.

Among them, the double integration circuit 33' performs double integration processing on the detection signal output from the geophone 2 (specifically, the detection signal amplified by the amplification circuit 31' described later). Specifically, the double integrator circuit 33' consists of a two-stage phase lag compensator that exhibits double integration characteristics for a given frequency range in the detected signal.

More specifically, the transfer function F ₃ (s) of the double integrator circuit 33′ is given by the following when the phase delay time constant is T ₃
F ₃ (s)={γ(1+T ₃ s)/(1+γT ₃ s)} ² where γ>1 (21)
can be represented by In this case, the breakpoint frequencies of double integration are (γT ₃ ) ⁻¹ and (T ₃ ) ⁻¹ in order from the low frequency side. This allows double integration of signals within the band from (γT ₃ ) ⁻¹ to (T ₃ ) ⁻¹ . Signals outside this band are substantially not integrated. Further, the frequency at which the phase lags the most in the double integration (the frequency at which the phase reaches its minimum value) is (γ ^0.5 T ₃ ) ⁻¹ . In the actual double integrator circuit 33', the transfer function _F3 (s) does not bend at the break point frequency, but rather gently curves.

Also, in order for the double integration circuit 33' to integrate a signal whose frequency is smaller than the natural frequency, the phase delay time constant and the natural frequency must be
(γT ₃ ) ⁻¹ <ω ₀ (22)
It is required to satisfy the relationship of In particular, the phase lag time constant and natural frequency according to this embodiment are
(γ ^0.5 T ₃ ) ⁻¹ <ω ₀ (23)
is set to satisfy the relationship of

Also, the gain suppression circuit 34' is configured by a notch filter. _The transfer function F _n (s) of _this notch filter is given by
F _n (s)=(s ² +2ζ ₁ ω ₀ s+ω ₀ ² )/(s ² +2ζ ₂ ω ₀ s+ω ₀ ² ) where ζ ₁ <ζ ₂ (24)
can be represented by

The damping ratios ζ ₁ and ζ ₂ of the notch filters are such that the gain of the signal output from the geophone 2 and passed through the double integration circuit 33 ′ and the gain suppression circuit 34 ′ becomes substantially constant with respect to increases and decreases in the frequency. is set to

After multiplying the detection signal represented by equation (8) by the transfer function F ₃ (s) represented by equation (21), the transfer function F _n (s) represented by equation (24) By multiplying by , it is possible to remove the rise in the gain near the natural frequency. This allows the geophone 2 to be used as a velocity sensor even at frequencies near the natural frequency.

A specific configuration of the control system in the vibration isolator A' according to the second embodiment will be described in detail below.

As shown in FIG. 8, the vibration isolator A' according to the present embodiment converts the detection signal (output signal) output from the geophone 2, thereby outputting a signal indicating the absolute velocity of the case 21. It has a conversion circuit 3' and a controller 4' that controls the actuator 13 in the vibration isolator A' based on a signal output from the speed conversion circuit 3'.

As shown in FIG. 9, the velocity conversion circuit 3' includes an amplifier 31' for amplifying the detection signal of the geophone 2, and the aforementioned double integration circuit 33' to which the detection signal amplified by the amplifier 31' is input. , the gain suppression circuit 34' to which the detection signal passed through the double integration circuit 33' is input, and the offset circuit 35' to generate a voltage for canceling the offset voltage contained in the detection signal. are doing.

A detection signal output from the speed conversion circuit 3' in the sensor system 100' indicates the absolute speed of the case 21 within a relatively wide range including the natural frequency. This detection signal is input to a controller 4' as an actuator control section. The controller 4' controls the actuator 13 based on the detection signal output from the sensor system 100' so as to suppress the vibration of the support base 10 as the object to be vibration-isolated.

Specifically, as shown in FIG. 9, the controller 4' according to the second embodiment includes an amplifier 41' that amplifies the detection signal output from the speed conversion circuit 3', and into a digital signal, a gain multiplier 44' that determines the feedback operation amount of the actuator 13 based on the signal converted by the A/D converter 42', and a digital signal determined as It has a D/A converter 45' that converts the feedback manipulated variable back into an analog signal, and an amplifier 46' that amplifies the feedback manipulated variable converted by the D/A converter 45'.

Among them, the gain multiplier 44' multiplies the detection signal indicating the absolute velocity of the support base 10 by the gain Gc to generate a digital signal indicating the feedback manipulated variable.

The controller 4 ′ inputs to the actuator 13 the feedback manipulated variable converted into an analog signal by the D/A converter 45 ′, and operates the actuator 13 . As a result, the actuator 13 applies a control force to the support base 10 that corresponds to the feedback operation amount. The control force thus applied is proportional to the absolute velocity of the support base 10, and functions as a skyhook damper in the vibration isolator A'. Thereby, the vibration of the support base 10 can be suppressed.

(Specific example of sensor system)
FIG. 10 is a diagram illustrating the frequency characteristic of the signal output from the double integration circuit 33' with respect to the absolute velocity, and FIG. FIG. 4 is a diagram illustrating frequency characteristics of a signal with respect to absolute velocity; Here, ω ₀ in FIGS. 10 and 11 refers to the natural frequency of geophone 2 .

FIG. 10 illustrates the influence of the double integration circuit 33' on the detection signal of the geophone 2. FIG. Here, as shown by the two-dot chain line in FIG. 10, the frequency characteristic of the detection signal before filtering (the detection signal before passing through the double integration circuit 33') is similar to the upper diagram of FIG. It monotonously decreases as the frequency becomes smaller than the number _ω0 , and becomes substantially constant when the frequency is larger than the natural frequency _ω0 .

On the other hand, as shown by the dashed line in FIG. 10, the frequency characteristic of the analog filter composed of the double integration circuit 33' has a frequency lower than the natural frequency ω ₀ in accordance with the functional form of the transfer function F ₃ (s). , and becomes substantially constant when the natural frequency ω is greater than ₀ .

In addition, when the frequency is smaller than the breakpoint frequency (=(γT ₃ ) ⁻¹ ) on the low-frequency side in the double integral (in the figure, the magnitude of the frequency is about 1% of the natural frequency ω ₀ ), the frequency characteristic of the analog filter is substantially constant with respect to the increase and decrease of the frequency.

Also, in the example shown in FIG. 10, the phase delay time constant and the natural frequency are
(T ₃ ) ⁻¹ =ω ₀ (25)
is set to satisfy the relationship of By setting in this way, the breakpoint frequency (=(T ₃ ) ⁻¹ ) on the high-frequency side in the double integration and the natural frequency (=ω ₀ ) match.

Then, the detection signal output from the geophone 2 and passed through the double integration circuit 33' is, as shown by the solid line in _FIG . In terms of number, it becomes a substantially constant straight line with respect to the increase and decrease of the frequency. In this case, the ratio between the detection signal that has passed through the double integration circuit 33' and the speed of the case 21 in the geophone 2 and the speed of the support base 10 to which the case 21 is attached becomes constant, and the geophone 2 is used as a speed sensor. can be used as

However, in the detection signal that has passed through the double integration circuit 33', the gain rises at frequencies near the natural frequency _ω0 . In this case, the geophone 2 cannot be used as a velocity sensor. As already explained, the problem of gain swelling can be solved by gain suppression circuit 34' configured as a notch filter.

FIG. 11 illustrates the effects of the double integration circuit 33 ′ and the gain suppression circuit 34 ′ on the detection signal of the geophone 2 . Specifically, as indicated by _the relatively narrow two-dot chain line in FIG _. Draw a valley-like curve that becomes the minimum at .

By passing the detection signal of the geophone 2 through the gain suppression circuit 34' in addition to the double integration circuit 33', the rise in gain near the natural frequency _ω0 is removed. As shown by the solid line in FIG. 11, the signal output from the gain suppression circuit 34' becomes a substantially constant straight line with respect to increases and decreases in the frequency over a relatively wide band including the natural frequency. As a result, the geophone 2 can be used as a velocity sensor within the range including the natural frequency.

(Effect of the sensor system according to the second embodiment)
As described above, by suppressing the gain at the natural frequency by the gain suppressing circuit 34', it is possible to remove the rise in the gain near the natural frequency as shown in FIG. Thereby, the output signal of the geophone 2 can be converted into the absolute velocity of the case 21 within a relatively wide range including the natural frequency. By attaching the case 21 to a predetermined detection target (for example, a vibration isolation target), the absolute velocity of the detection target can be detected via the case 21 .

In addition, in this embodiment, by providing the resistor 27 in the geophone 2, the magnitude of the gain at the natural frequency (especially the magnitude of the maximum value in the central diagram of FIG. 3) is suppressed, and the natural frequency It is configured to gently change the slope of the gain in the vicinity. By configuring in this way, damping can be applied to the motion of the mass body 22, and collision between the mass body 22 and the case 21 can be suppressed when a relatively large vibration occurs.

In addition, by gently changing the slope of the gain, the magnitude of the output from the geophone 2 can be suppressed. As a result, the output does not become excessively large when vibration near the natural frequency is input. This is advantageous in protecting the electric circuit.

<<Other embodiments>>
In the first and second embodiments, the actuator 13 made up of a linear motor was exemplified, but the configuration of the actuator 13 is not limited to this. For example, actuators made of piezoelectric elements may be used. In this case, the actuator composed of the piezoelectric element can suppress the vibration of the vibration isolation object by applying displacement to the vibration isolation object (displacing the vibration isolation object). In this case, an elastic body such as rubber can be connected in series with the actuator. By connecting the elastic body in series with the actuator, the displacement applied to the vibration isolation object can be converted into force, and the converted force can be applied to the vibration isolation object.

Also, in the first embodiment, the actuator 13 made of an air spring may be used instead of the linear motor. In that case, the controller 4 will control the servovalve of the air spring. The air spring integrates the feedback operation amount. Therefore, when the actuator 13 made of an air spring is used, the integrator 43 becomes unnecessary even in the first embodiment.

Further, in the first and second embodiments, the geophone 2 provided with the magnet 26 supported by the case 21 and the coil 25 displaced integrally with the mass body 22 is used as an example of the conductive velocity sensor. Although disclosed, the configuration of the geophone 2 is not limited to this. For example, the geophone 2 configured such that the coil 25 is fixed to the case 21 and the magnet 26 moves integrally with the mass body 22 may be used.

Further, in the first embodiment, the circuit configuration is such that the phase lead compensator 32 as a differentiating circuit, the phase lag compensator 33 as an integrating circuit, and the gain suppressing circuit 34 as a notch filter are connected in this order. Although exemplified, the order of connecting each circuit can be freely changed. Similarly, also in the second embodiment, the order of connecting the circuits can be changed.

Also, in the first embodiment, the A/D converter 42 is arranged in the controller 4, but the place where the A/D converter 42 is connected can be freely changed. For example, an A/D converter 42 may be arranged between the amplifier 31 and the phase lead compensator 32 in the acceleration conversion circuit 3 . When arranged in this way, the phase lead compensator 32, the phase lag compensator 33, and the gain suppression circuit 34 each process a digital signal. That is, the acceleration conversion circuit 3 as a signal processing section can output not only analog signals but also digital signals. Similarly, in the second embodiment as well, the location where the A/D converter 42' is connected can be changed.

Further, the direction of acceleration detected by the sensor system 100 according to the first embodiment is not particularly limited. When suppressing vibration in the vertical direction as in the first embodiment, the sensor system 100 preferably detects acceleration in the vertical direction. Alternatively, when suppressing vibration in the horizontal direction, sensor system 100 preferably detects acceleration in the horizontal direction. In the latter case, the geophone 2 is oriented horizontally and will generate control forces along the horizontal direction. When the geophone 2 is oriented horizontally, the actuator 13 is also installed along the horizontal direction. At the same time, the vertical elastic body 11 and the damper 12 exert elastic force and damping force in the horizontal direction, respectively. The same applies to the direction of the absolute velocity detected by the sensor system 100' according to the second embodiment.

A, A' Vibration isolation device 1 Vibration isolation table 10 Support table (vibration isolation object)
13 Actuator 2 geophone (conductive speed sensor)
21 case 22 mass body 23 damper 24 spring 25 coil 26 magnet 3 acceleration conversion circuit (signal processing unit)
3' speed conversion circuit (signal processing unit)
32 phase lead compensator (differential circuit)
33 phase lag compensator (integrator circuit)
33' double integration circuit 34, 34' gain suppression circuit 4, 4' controller 100, 100' sensor system

Claims (9)

A sensor system for detecting acceleration, comprising:
It is modeled as a dynamic system having a case, a mass housed in the case and relatively displaceable with respect to the case, and a damper and a spring that support the mass on the case. a conductive speed sensor that outputs a signal proportional to the relative speed between
a signal processing unit that outputs a signal indicating the acceleration of the case by converting the signal output from the conductive speed sensor,
The signal processing unit is
a differentiating circuit that differentiates a signal having a frequency higher than the natural frequency of the dynamic system;
and an integrating circuit that integrates a signal having a frequency smaller than the natural frequency, and
The sensor system, wherein the signal processing unit is further connected in series with a gain suppression circuit for suppressing gain at the natural frequency. The sensor system of claim 1, wherein
The transfer function F ₁ (s) of the differentiation circuit is given by the Laplace operator as s and the phase lead time constant as T ₁ :
F ₁ (s)=(1+T ₁ s)/(1+αT ₁ s) where α<1 (A)
is represented by
The transfer function F ₂ (s) of the integration circuit is given by the following when the phase delay time constant is T ₂
F ₂ (s)=β(1+T ₂ s)/(1+βT ₂ s) where β>1 (B)
is represented by
Assuming that the natural frequency is _ω0 , the phase lead time constant, the phase lag time constant and the natural frequency are
(βT ₂ ) ⁻¹ <ω ₀ <(αT ₁ ) ⁻¹ (C)
A sensor system characterized by satisfying the relationship of In the sensor system according to claim 2,
The phase lead time constant, the phase lag time constant and the natural frequency are
(β ^0.5 T ₂ ) ⁻¹ <ω ₀ <(α ^0.5 T ₁ ) ⁻¹ (D)
A sensor system characterized by satisfying the relationship of A sensor system for detecting absolute velocity, comprising:
It is modeled as a dynamic system having a case, a mass housed in the case and relatively displaceable with respect to the case, and a damper and a spring that support the mass on the case. a conductive speed sensor that outputs a signal proportional to the relative speed between
a signal processing unit that outputs a signal indicating the absolute speed of the case by converting a signal output from the conductive speed sensor,
The signal processing unit is
a double integration circuit that double integrates a signal having a frequency smaller than the natural frequency of the dynamic system;
and a gain suppression circuit that suppresses the gain at the natural frequency, and a sensor system connected in series. In the sensor system according to claim 4,
The transfer function F ₃ (s) of the double integration circuit is given by the following when the phase delay time constant is T ₃
F ₃ (s)={γ(1+T ₃ s)/(1+γT ₃ s)} ² where γ>1 (E)
is represented by
Assuming that the natural frequency is ω ₀ , the phase delay time constant and the natural frequency are
(γT ₃ ) ⁻¹ < ω ₀ (F)
A sensor system characterized by satisfying the relationship of In the sensor system according to claim 5,
The phase delay time constant and the natural frequency are
(γ ^0.5 T ₃ ) ⁻¹ <ω ₀ (G)
A sensor system characterized by satisfying the relationship of In the sensor system according to any one of claims 1 to 6,
The gain suppression circuit is configured by a notch filter,
_The transfer function F _n (s) _of the notch filter is given by
F _n (s)=(s ² +2ζ ₁ ω ₀ s+ω ₀ ² )/(s ² +2ζ ₂ ω ₀ s+ω ₀ ² ) where ζ ₁ <ζ ₂ (H)
A sensor system characterized by being represented by: In the sensor system according to any one of claims 1 to 7,
A sensor system, wherein a resistor is connected between positive and negative terminals of the conductive speed sensor. a sensor system according to any one of claims 1 to 8;
a vibration isolating object to which the case is attached and which vibrates integrally with the case;
an actuator that applies a control force or displacement to the object to be isolated;
and an actuator control section that controls the actuator so as to suppress vibration of the object to be vibration-isolated based on a signal output from the sensor system.

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