JP5043726B2 - Servo vibration meter - Google Patents

Description

  The present invention relates to a servo-type vibrometer that outputs a vibration speed signal in order to measure vibrations such as earthquakes and shaking of buildings.

  Conventionally, as this type of servo vibrometer, for example, the one described in Patent Document 1 is known.

  FIG. 13 shows the servo vibrometer described in Patent Document 1. In FIG. This servo-type vibrometer 1 includes a pendulum 2, and vibration displacement acting on the pendulum 2 is converted into an electric signal by a displacement detector 3, and this displacement output is supplied to a drive unit 5 via an amplifier 4. It has become so. The pendulum 2 is supported by a support spring 6 and an attenuator 7 is connected to a part thereof.

  The vibration acting on the pendulum 2 is detected by the displacement detector 3 as a displacement of the pendulum 2 as an electrical signal, which is output through the amplifier 4. At the same time, the electrical signal from the amplifier 4 passes through the differentiation circuit 8. Returning to the drive unit 5, the drive unit 5 generates a restoring force corresponding to the magnitude of the differential output of the displacement of the pendulum 2, and generates a force that returns the pendulum 2 to its original position.

  The equation of motion of the pendulum 2 is given by the following equation.

Here, the right side is the sum of the external forces acting on the pendulum 2, the first term on the right side is the braking force of the attenuator 7, the second term is the restoring force of the support spring 6, and the third term is the restoring force by the drive unit 5. The fourth term is the inertial force due to vibration acceleration, x is the displacement of the pendulum 2, y is the displacement of the vibrometer 1, m is the mass of the pendulum 2, k is the spring constant of the support spring 6, and D is the attenuator 7. , A is the gain of the amplifier 4, and A ′ is the gain by the differentiation circuit 8 and the drive unit 5.

  Rewriting the above formula,

となる。ここで、左辺第２項のアンプ４のゲインAを大きく設定すると、上式は、近似的に

It becomes. Here, if the gain A of the amplifier 4 in the second term on the left side is set large, the above equation is approximately

と表すことができ、振子２の変位量xは、振動計１の空間に対する変位yの速度に比例することになる。こうして、アンプ４からの出力を速度信号として得ることができる。

The displacement amount x of the pendulum 2 is proportional to the speed of the displacement y with respect to the space of the vibrometer 1. In this way, the output from the amplifier 4 can be obtained as a speed signal.

Japanese Utility Model Publication No. 6-28698

  However, in the conventional configuration described above, it is necessary to increase the gain of the amplifier 4 in order to detect a speed signal in a wide frequency band. However, since the sensitivity is low for high frequencies, if the gain of the amplifier 4 of the servo loop is further increased to compensate for this, the feedback signal is saturated with respect to a large vibration input. However, there is a problem that a large speed cannot be detected.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a servo-type vibrometer that can obtain a vibration speed signal with high sensitivity in a wide band and can expand a dynamic range.

In order to achieve the above object, the invention according to claim 1 of the present invention is characterized in that a base, a pendulum supported by an elastic member with respect to the base and capable of vibrating, and a relative relationship between the base and the pendulum. A pickup that detects displacement, a torquer that generates a force that returns a pendulum in which relative displacement has occurred toward a neutral point, an output signal from the pickup is input, and a feedback signal to the torquer is output and a vibration speed signal A servo-type vibrometer having a signal processing unit for outputting
The signal processing unit
Discriminating means for discriminating an output signal from the pickup into a high frequency signal and a low frequency signal according to a frequency;
First amplifying means for amplifying a high-frequency signal from the discriminating means to be the feedback signal;
Integrating means for integrating the high frequency signal from the discriminating means into the vibration speed signal;
Differentiating means for differentiating the low-frequency signal from the discriminating means into the feedback signal;
A second amplifying means for amplifying a low-frequency signal from the discriminating means into the vibration speed signal;
It is characterized by having.

  The invention according to claim 2 is characterized in that the discriminating means according to claim 1 comprises a high-pass filter and a low-pass filter.

  According to a third aspect of the present invention, in the second aspect, the cutoff frequency of the high-pass filter and the cutoff frequency of the low-pass filter are substantially the same.

  According to a fourth aspect of the present invention, the signal processing unit according to any one of the first to third aspects outputs a feedback signal to ToruCa as a vibration acceleration signal.

  According to a fifth aspect of the present invention, the signal processing unit according to any one of the first to fourth aspects further includes a low-pass filter that extracts a DC component of an output signal from the pickup, and an output from the low-pass filter. Is added to the feedback signal.

  The invention according to claim 6 is characterized in that the signal processing unit according to claim 5 outputs the output from the low-pass filter as a DC acceleration signal.

  According to a seventh aspect of the present invention, the discriminating means according to any one of the first to sixth aspects includes a first signal discriminating unit connected to the first amplifying means and the differentiating means, and the integrating means. And a second signal discrimination unit connected to the second amplification means.

  The invention according to claim 8 is the first addition in which the signal processing unit according to any one of claims 1 to 7 further adds the outputs of the first amplifying unit and the differentiating unit. Means, and a second adding means for adding the outputs of the integrating means and the second amplifying means.

  According to the present invention, a high frequency signal and a low frequency signal are discriminated according to the frequency of the input vibration, and an appropriate configuration can be obtained for each band. Therefore, a correct vibration speed signal can be obtained with little influence of noise components, and as a result, a high-sensitivity vibration speed signal can be obtained in all bands including the high and low frequencies.

  In the low frequency range, the high-sensitivity speed signal is differentiated by the differentiation means. In the high frequency range, the high-sensitivity acceleration signal is amplified by the first amplification means to create a feedback signal. You can get a range.

Hereinafter, the present invention will be described with reference to the drawings.
FIG. 1 is an overall view showing an embodiment of a servo vibrometer 10 according to the present invention.

  The servo vibrometer 10 includes a mechanism unit 12 and an electric circuit unit 14 as a whole.

  The mechanism unit 12 includes a pendulum 24 connected to the base 20 via a hinge 22 as an elastic member, a torquer 26, and a pickup 28 that detects the displacement of the pendulum 24. The torquer 26 includes a magnet 30 and a torquer coil 32 coupled to the pendulum 24. The pickup 28 can be constituted by, for example, a light emitter and a light receiver that optically detect the displacement of the pendulum 24.

  When vibration input is applied to the pendulum 24 and the relative displacement with respect to the base 20 is made, this displacement is optically detected as a light quantity by the pickup 28 and this light quantity is converted into a voltage. A voltage signal from the pickup 28 is input to the electric circuit unit 14.

  The electric circuit unit 14 includes a signal processing unit 34 and an output resistor 36. A current that causes the relative displacement of the pendulum 24 detected by the pickup 28 from the electric circuit unit 14 to be zero and the pendulum 24 to return to the neutral position flows to the torquer coil 32 and the output resistor 36.

  Considering the equation of motion of the pendulum composed of this mechanism 12, the following is obtained.

ここで、振り子２４の変位である角度をθ、振り子のペンデュロシィティをP、慣性モーメントをJ、ヒンジのバネ定数をk、粘性減衰定数をc、振動入力をFとしている。

Here, the angle which is the displacement of the pendulum 24 is θ, the pendulum pendency is P, the moment of inertia is J, the spring constant of the hinge is k, the viscous damping constant is c, and the vibration input is F.

  When s is a Laplace variable, the pendulum vibration system S (s) is

と表される。この振動系の固有周波数ω₀は

It is expressed. The natural frequency ω ₀ of this vibration system is

である。

It is.

  FIG. 2 shows a block diagram of the servo vibrometer 10 of the present invention.

In FIG. 2, K _p is the gain of the pickup 28. The signal processing unit 34 includes a first signal discrimination unit 40 and a second signal discrimination unit 42 as discrimination means for discriminating an output signal from the pickup 28 into a high frequency signal and a low frequency signal. Each signal discrimination unit is provided with one input end 40a, 42a and two output ends 40b, 40c, 42b, 42c, and a voltage signal from the pickup 28 is input to the input ends 40a, 42a.

  FIG. 3 is a specific block diagram of each signal discriminating unit 40, 42. Each of the signal discrimination units 40 and 42 includes a high-pass filter 44 and a low-pass filter 46, and thereby outputs the output signal of the pickup 28 into a high-frequency signal and a low-frequency signal by frequency. The cut-off frequencies of the high pass filter 44 and the low pass filter 46 are preferably substantially the same.

  A normal first amplifier (first amplifying means) 50 for amplifying the high frequency signal with a predetermined gain G1 is connected to the output terminal 40b from which the high frequency signal is output from the first signal discrimination unit 40. A differential amplifier 52 (differentiating means) for differentiating the low-frequency signal and amplifying it with a gain G2 is connected to the output terminal 40c from which the low-frequency signal is output from the signal discrimination unit 40.

The output terminal 42b of the high frequency signal from the second signal discrimination unit 42 is output, the integrating amplifier (integrating means) 54 for amplifying and integrating the high-frequency signal with a predetermined gain A ₁ is connected, a second signal to the output terminal 42c of the discrimination unit 42 the low frequency signal is output, the second amplifier 56 (second amplifier means) for amplifying said low frequency signal by a gain a ₂ is connected.

The outputs of the first amplifier 50 and the differential amplifier 52 are added at the first addition point 60 (adding means) and connected to the feedback loop 62. The feedback loop 62, feedback amplifier 64 which amplifies the gain G ₄ is provided. Here, the feedback amplifier 64 includes the ToruCa 26.

  The outputs of the integrating amplifier 54 and the second amplifier 56 are added at a second addition point 68 (adding means) to become a vibration speed signal output terminal 70. The signal from the first addition point 60 is a vibration acceleration signal output end 72.

  The operation of the servo vibrometer 10 configured as described above will be described.

  Considering the high-frequency component of the vibration input now, the high-frequency signal from the pickup 28 that detects the displacement of the pendulum 24 of the vibration system S (s) passes through the high-pass filter of the first signal discrimination unit 40, and the first Returned through the amplifier 50. Further, the signal passes through the high-pass filter of the second signal discrimination unit 42, passes through the integrating amplifier 54, and is output to the vibration speed signal output terminal 70. That is, the servo vibrometer represented by the block diagram of FIG. 2 is equivalent to the block diagram shown in FIG.

  Here, the equation of motion of FIG. 4 is as follows.

  The transfer function G (s) in Fig. 4 is

で表される。サーボ型としたことでこの振動系の固有周波数ω₃は

It is represented by By adopting the servo type, the natural frequency ω ₃ of this vibration system is

となり、サーボ型にする前に比べて固有周波数が大きくなり、この分だけ帯域を広くすることができる。この伝達関数G(s)のゲインと周波数の関係を図５に示す。

Thus, the natural frequency is larger than before the servo type, and the band can be widened accordingly. FIG. 5 shows the relationship between the gain and frequency of this transfer function G (s).

At a frequency smaller than ω ₃ , since the term of the pendulum displacement θ becomes dominant in the equation (4), the fact that the pendulum displacement is proportional to the acceleration of the vibration input is used. That is,

である。ここで、ｙは振動計の変位である。

It is. Here, y is the displacement of the vibrometer.

  Therefore, the output from the integrating amplifier 54 obtained by integrating the output signal from the pickup 28 is supplied to the first addition point 60 as a vibration speed signal. The output from the first amplifier 50 is supplied to the second addition point 68 as a vibration acceleration signal.

  Next, considering the low frequency component of the vibration input, the low frequency signal from the pickup 28 that detects the displacement of the pendulum 24 of the vibration system S (s) passes through the low-pass filter of the first signal discrimination unit 40. The feedback is made through the differential amplifier 52. Further, the signal passes through the low-pass filter of the second signal discrimination unit 42, passes through the second amplifier 56, and is output to the vibration speed signal output terminal 70. That is, the servo vibrometer represented by the block diagram of FIG. 2 is equivalent to the block diagram shown in FIG.

  Here, the equation of motion of FIG. 6 is as follows.

  The transfer function G (s) in FIG.

で表される。この系の固有周波数は変化しないが、減衰係数比ζが元々の振動系の減衰係数比ζ₀と比べて大きくなり、ダンピングされる。

It is represented by The natural frequency of the system is not changed, the damping coefficient ratio zeta becomes larger than the original and the damping coefficient ratio zeta ₀ of the vibration system is dumping.

In this case, since the speed term of the pendulum becomes dominant near the natural frequency, the fact that the pendulum speed is proportional to the acceleration of the vibration input, that is, the displacement of the pendulum is proportional to the speed of the vibration input is used. From equation (9), the band that is proportional to the velocity signal only in the vicinity of the natural frequency is expanded by the amount damped around the natural frequency (for example, the range is from ω ₁ to ω ₄ ). The relationship between the gain and frequency of this transfer function G (s) is shown in FIG.

  Therefore, the output from the second amplifier 56 obtained by amplifying the output signal from the pickup 28 is supplied to the first addition point 60 as a vibration speed signal. The output from the differential amplifier 52 is supplied to the second addition point 68 as a vibration acceleration signal.

  As described above, by adding at the first addition point 60 and the second addition point 68, respectively, a high frequency signal and a low frequency signal are combined, and a vibration speed signal is output from the output terminal 70. A vibration acceleration signal is output from the end 72.

Highpass and ₂ the cutoff frequency omega of the low-pass filter signal discrimination unit, omega ₁ the cut-off frequency of the low frequency of FIG. 7, the cutoff frequency of the high band of Figure 5 when the omega _3, a first summing point The input of 60 is shown in FIG. The horizontal axis is the frequency, and the vertical axis is the gain of the vibration acceleration signal.

  The output of the first addition point 60 is the combined signal as shown in FIG. The horizontal axis is the frequency, and the vertical axis is the gain of the vibration acceleration signal. The same applies to the second addition point 68. In this case, the vertical axis in FIGS. 8 and 9 is the gain of the vibration speed.

The cutoff frequency ω ₂ of the high-pass filter 44 and the low-pass filter 46 of the signal discrimination unit is ideally ω = 1 where the displacement amount of acceleration and velocity is the same, but the natural frequency ω ₀ of the actual vibration system and the servo amplifier It should be determined with reference to the realizable gain range.

  In this embodiment, the following effects can be obtained.

  When the displacement detected by the pickup is proportional to the acceleration of the vibration input, the higher the frequency, the greater the displacement, so the sensitivity is greater. Since the configuration shown in FIG. 4 is applied to the high frequency signal, the acceleration can be detected with high sensitivity, and a correct velocity signal can be obtained by integrating it.

  On the other hand, for the low-frequency signal, the configuration shown in FIG. 4 has a high noise component due to low sensitivity, and when integrating the signal from the pickup 28 by the integrating amplifier 54 to obtain a speed signal, The components are also integrated, making it difficult to obtain a correct speed signal.

  However, the low-frequency signal has the configuration shown in FIG. 6, and the vibration speed signal can be obtained with high sensitivity by making the displacement detected by the pickup proportional to the speed of the vibration input.

  In this way, the high frequency signal and the low frequency signal are discriminated according to the frequency of the input vibration, and by adopting a configuration suitable for each, it is possible to obtain an advantageous configuration in each band, and relatively reduce the noise component. The correct vibration speed signal is obtained with little influence, and as a result, a high-sensitivity vibration speed signal is obtained in the entire band including the high and low frequencies.

  Since the high-speed velocity signal is differentiated in the low frequency range and the feedback signal is generated using the high-sensitivity acceleration signal in the high frequency range, the limitation of the servo loop gain is relaxed and a large dynamic range can be obtained.

  FIG. 10 is a block diagram showing a second embodiment of the servo vibrometer of the present invention. The same members as those of the previous embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this example, the signal processing unit 34 has one signal discrimination unit 48. The signal discriminating unit 48 is provided with one input end 48a and two output ends 48b, 48c, and a voltage signal from the pickup 28 is input to the input end 48a. A first amplifier 50 and an integrating amplifier 54 are connected to an output terminal 48b from which a high frequency signal is output from the signal discrimination unit 48, and a differential amplifier is connected to an output terminal 48c from which the low frequency signal is output from the signal discrimination unit 48. 52 and the second amplifier 56 are connected.

  Even with such a configuration, the same operations and effects as in the first embodiment can be obtained.

  FIG. 11 is a block diagram showing a third embodiment of the servo vibrometer of the present invention. The same members as those of the previous embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this example, in the configuration of the first embodiment, the signal processing unit 34 further includes a DC feedback unit 80. The DC feedback unit 80 includes a low-pass filter 82 to which a voltage signal from the pickup 28 is input and an integrating amplifier 84. The signal from the DC feedback unit 80 becomes a DC acceleration signal output terminal 74.

  This DC feedback unit 80 extracts and integrates only the DC component from the pickup output, and feeds it back. The output from the DC feedback unit 80 is applied to the first addition point 60. By doing so, even if the pendulum 24 is inclined, the position of the pendulum 24 is correctly constrained to the zero point of the pickup. Since the output from the DC feedback unit 80 is proportional to the DC acceleration, a DC acceleration signal is output from the output end 74.

The input of the first addition point 60 is as shown in FIG. The horizontal axis is the frequency, and the vertical axis is the gain of the acceleration signal. The cut-off frequency of the low-pass filter 82 of the DC feedback unit 80 is preferably equal to or smaller than the low-frequency cut-off frequency ω _{1 in} FIGS.

  In the first and second embodiments, since only the vibration component is included in the feedback signal, the position of the pendulum may become indefinite due to an input other than the vibration component. However, according to the third embodiment, the position of the pendulum 24 is correctly constrained to the zero point of the pickup by including a DC component in the feedback signal. Further, since the signal output from the DC acceleration signal output terminal 74 is proportional to the DC acceleration, it is possible to detect a change in the attitude of the vibrometer by taking out the DC acceleration. Therefore, even if the vibration meter is tilted from the initial position and the detection axis of the pendulum is shifted, the inclination is detected by a signal from the DC acceleration signal output end 74, and converted into a speed signal on the correct detection axis by calculation.・ Can be calibrated.

1 is an overall view showing an embodiment of a servo vibrometer according to the present invention. It is a block diagram showing 1st Embodiment of the servo-type vibrometer of this invention. It is a detailed block diagram of a signal discrimination unit. It is an equivalent block diagram of the servo vibrometer of the present invention for high frequency vibration input. 5 is a graph showing the relationship between the gain and frequency of the transfer function G (s) in FIG. It is an equivalent block diagram of the servo vibrometer of the present invention with respect to a low frequency vibration input. 7 is a graph showing the relationship between the gain and frequency of the transfer function G (s) in FIG. 6. It is a graph showing the frequency band of the signal before adding at the 1st addition point. It is a graph showing the frequency band of the signal synthesize | combined by the 1st addition point. It is a block diagram showing 2nd Embodiment of the servo-type vibrometer of this invention. It is a block diagram showing 3rd Embodiment of the servo-type vibrometer of this invention. It is a graph showing the frequency band of the signal before adding in a 1st addition point in FIG. It is an example of composition of the conventional servo type vibration meter.

Explanation of symbols

10 Servo-type Vibrometer 20 Base 22 Hinge (elastic member)
24 Pendulum 26 ToruCa 28 Pickup 34 Signal Processing Unit 40 First Signal Discrimination Unit (Discrimination Unit)
42 Second signal discrimination unit (discrimination means)
48 Signal discrimination unit (discrimination means)
44 High-pass filter 46 Low-pass filter 50 First amplifier (first amplification means)
52 Differential amplifier (differential means)
54 Integration amplifier (integration means)
56 Second amplifier (second amplification means)
60 First addition point (addition means)
68 Second addition point (addition means)
82 Low-pass filter

Claims (8)

The base, the pendulum supported by the elastic member with respect to the base and capable of vibrating, the pickup for detecting the relative displacement between the base and the pendulum, and the pendulum with the relative displacement at the neutral point In a servo vibrometer having a torquer that generates a force to return to, and a signal processing unit that outputs an output signal from the pickup and outputs a feedback signal to the torquer and outputs a vibration speed signal,
The signal processing unit
Discriminating means for discriminating an output signal from the pickup into a high frequency signal and a low frequency signal according to a frequency;
First amplifying means for amplifying a high-frequency signal from the discriminating means to be the feedback signal;
Integrating means for integrating the high frequency signal from the discriminating means into the vibration speed signal;
Differentiating means for differentiating the low-frequency signal from the discriminating means into the feedback signal;
A second amplifying means for amplifying a low-frequency signal from the discriminating means into the vibration speed signal;
Servo-type vibrometer characterized by comprising:   2. The servo vibrometer according to claim 1, wherein the discriminating means includes a high pass filter and a low pass filter.   The servo-type vibrometer according to claim 2, wherein a cutoff frequency of the high-pass filter and a cutoff frequency of the low-pass filter are substantially the same.   4. The servo vibrometer according to claim 1, wherein the signal processing unit outputs a feedback signal to ToruCa as a vibration acceleration signal. 5.   5. The signal processing unit according to claim 1, further comprising a low-pass filter that extracts a direct current component of an output signal from the pickup, and adds an output from the low-pass filter to the feedback signal. The servo vibrometer according to item 1.   6. The servo vibrometer according to claim 5, wherein the signal processing unit outputs an output from the low-pass filter as a DC acceleration signal.   The discrimination means comprises a first signal discrimination unit connected to the first amplification means and the differentiation means, and a second signal discrimination unit connected to the integration means and the second amplification means. The servo vibrometer according to any one of claims 1 to 6.   The signal processing unit further adds a first adding means for adding outputs of the first amplifying means and the differentiating means, and adds outputs of the integrating means and the second amplifying means. The servo vibrometer according to claim 1, further comprising: 2 addition means.

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