JP5652760B2 - Acceleration sensor characteristic evaluation device - Google Patents

Description

  The present invention relates to a characteristic evaluation device for an acceleration sensor used as a displacement measuring means, for example.

  Designation that the interlaminar deformation angle representing the relative deformation of the building itself is within 1/200 in addition to the designation of load, allowable stress level, rigidity, and eccentricity by the Building Standards Act as the earthquake resistance standard for buildings. Is provided. Since the value of each interlaminar deformation angle is calculated from the characteristics of the building members at the design stage, changes due to the conditions of enforcement and external conditions after construction are not considered. Therefore, in order to determine whether a building affected by an earthquake or secular change satisfies the earthquake resistance standard, the value of each inter-layer deformation angle of the actual building itself, not the building at the design stage. Need to be calculated.

  That is, when the building vibrates due to an earthquake or the like, it is necessary to calculate the value of each interlayer deformation angle as the deformation behavior of the building. This inter-layer deformation angle is a value obtained from each horizontal displacement of the floor and ceiling of a certain level and the height of that level. Therefore, it is necessary to measure the displacement of the floor and ceiling of each level.

  There is a displacement amount sensor that requires an absolute reference plane or reference position to directly measure the displacement.

  However, unlike a laboratory system, it is difficult to obtain an absolute reference plane or reference position in an actual building. As a result, it is not possible to directly measure the displacement of each level of a building using a displacement sensor. Not right.

  On the other hand, in recent years, an acceleration sensor that obtains a displacement by integrating a measured value two-dimensionally has been attracting attention as an indirect measure of the displacement of each level of a building. Particularly in high-rise buildings and the like, since there is no practical means for measuring the effect of an earthquake or the like, the practical use of a displacement measuring device using an acceleration sensor that can be automatically measured is expected.

  FIG. 7 is a diagram schematically showing a building in which an acceleration sensor is installed as a seismometer. As shown in FIG. 7, in order to obtain the response characteristic with respect to the vibration of each level of the building, it is necessary to provide one to several acceleration sensors 701 to 709 in each level. 7 shows the output waveforms of the acceleration sensors 701 to 709 when an earthquake propagates, and is supplied to the control circuit (computer) 710 and used to calculate the interlayer deformation angle of each layer. In this case, the number of acceleration sensors is not so high in a low-rise building, but the number of acceleration sensors is high in several tens and several hundreds in a high-rise building. As a result, an acceleration sensor that is inexpensive in terms of manufacturing cost is used. However, since the accuracy of each product of an inexpensive acceleration sensor product group is not actually guaranteed, variation in the measurement accuracy of the acceleration sensor becomes a problem. In particular, a low-frequency component that is considered to cause a large loss to a high-rise building has a large contribution to displacement, but has a small acceleration amplitude, and thus is easily affected by noise. Therefore, if the measurement accuracy of the acceleration sensor varies, the accuracy of the displacement obtained by second-order integration of the low-frequency component further varies.

  In general, in order to obtain the displacement by integrating the measured value of the acceleration sensor by the second order, it is necessary to perform the baseline correction processing because the baseline of the acceleration sensor is unstable, etc. Perform second-order integration after performing appropriate bandpass filtering. Therefore, the displacement obtained by second-order integration of the output of the acceleration sensor without performing these processes increases the accumulation error and becomes a value greatly different from the actual displacement. For example, the motion trajectory obtained by simple second-order integration when a constant circular motion with a constant velocity of 5 cm in radius and a period of 10 seconds is given to an acceleration sensor is as shown in FIG. It will deviate greatly.

  Thus, it is necessary to evaluate and correct the individual characteristics of each acceleration sensor of the product group, that is, the measurement accuracy.

  FIG. 9 is a plan view showing a conventional acceleration sensor characteristic evaluation apparatus (see: p. 14 to p. 15 of Non-Patent Document 1). In FIG. 9, (B) shows a state in which the state (A) is rotated by approximately 90 °.

  In FIG. 9, a large rotating table 901 and a small rotating table 902 are provided for low-frequency two-axis excitation, and the rotating shaft A2 of the small rotating table 902 is shifted with respect to the rotating shaft A1 of the large rotating table 901. . An acceleration sensor 903 is fixed on the small turntable 902.

In FIG. 9, the angular velocities ω ₁ and ω ₂ of the rotary tables 901 and 902 are opposite and are both constant,
ω ₁ = ω ₂
It is. Therefore, the angle of the measurement axis M (for example, the X axis) of the acceleration sensor 903 is constant regardless of the direction of the centrifugal force F. As a result, the acceleration sensor 903 can perform a uniform circular motion while maintaining an angular posture with respect to the outside world, and thus, the acceleration sensor 903 can simultaneously measure two axes.

ISO 16063-1: Methods for the calibration of vibration and shock transducers Part 1, Basic concepts, 1998

However, in the acceleration sensor characteristic evaluation apparatus of Figure 9, a large rotary table 901, the moment of inertia and the friction force of the small rotary table 902 changes depending on the phase, this results in a very short time, the wobbling is, omega ₁ = omega ₂ does not hold. Therefore, the angle of the measurement axis M (for example, the X axis) of the acceleration sensor 903 is not constant during a very short time. As a result, in a very short time, the acceleration sensor 903 cannot maintain an angular posture with respect to the outside world and cannot perform a constant velocity circular motion, thereby making it impossible to simultaneously measure the acceleration sensor 903 with high accuracy. There is. Further, since the known circular motion displacement of the acceleration sensor 903 as a reference value determined by the rotation of the two rotary tables 901 and 902 is not guaranteed due to fluctuation, there is a problem that the measured value of the acceleration sensor 903 cannot be corrected. Furthermore, since the moment of inertia changes depending on the phase, there is a problem that it is difficult to control the acceleration with high accuracy.

  Accordingly, the present invention makes the moment of inertia and the frictional force independent of the phase, and enables a constant speed circular motion with a high degree of accuracy while keeping the acceleration sensor in an angular posture with respect to the outside world even in a very short time. Simultaneous measurement of two axes is possible, and a known displacement of the acceleration sensor is guaranteed, and the measurement value of the acceleration sensor can be corrected.

In order to solve the above-described problems, an acceleration sensor characteristic evaluation apparatus according to the present invention includes a table for fixing an acceleration sensor, and three links that are connected to the table and have the same length and are infinitely rotatable and parallel. And a single rotating plate provided on one of these three links, and a single drive motor for rotating the rotating plate to synchronously drive the three links. . As a result, the table performs a circular motion with the length of the link as a radius.

  Moreover, the counterweight according to the mass of the acceleration sensor and the table was provided in each link on the opposite side to the table. This prevents the load from being biased during rotation. Further, the center of mass of the acceleration sensor and the table, the center of mass of each link, and the center of mass of the counterweight coincide with each other in the height direction of the apparatus. Thereby, almost no torque is required when the device is rotated at any inclination.

  According to the present invention, since the moment of inertia and the frictional force do not depend on the phase, even in a very short time, the accelerometer can perform a constant velocity circular motion while maintaining an angular posture with respect to the outside world, so that two axes with high accuracy can be obtained. Simultaneous measurement is possible. The measured value of the acceleration sensor can be corrected by guaranteeing the known displacement of the acceleration sensor whose radius is the length of the link.

It is a figure which shows the principle of the acceleration sensor characteristic evaluation apparatus which concerns on this invention. It is a perspective view which shows embodiment of the acceleration sensor characteristic evaluation apparatus which concerns on this invention. It is a fragmentary sectional view of the acceleration sensor characteristic evaluation apparatus of FIG. 4 is a flowchart showing the operation of the control circuit of FIG. 3. FIG. 4 is a timing diagram illustrating an example of an X-axis acceleration signal and a Y-axis acceleration signal of the acceleration sensor in FIG. 3. It is a graph which shows the locus | trajectory of the X-axis displacement and Y-axis displacement calculated from the X-axis acceleration signal and Y-axis acceleration signal of FIG. It is a figure which shows the example of the building which provided the acceleration sensor as a seismometer. It is a graph which shows the locus | trajectory of the X-axis displacement and Y-axis displacement calculated from the measured value of the acceleration sensor of FIG. It is a top view which shows the conventional acceleration sensor characteristic evaluation apparatus.

  FIG. 1 is a diagram showing the principle of an acceleration sensor characteristic evaluation apparatus according to the present invention.

  As shown in FIG. 1, links 3-1, 3-2 and 3-3 having the same length r are connected to each vertex of a regular triangular table 2 for fixing the acceleration sensor 1. The links 3-1, 3-2 and 3-3 are parallel to each other, and can rotate infinitely with respect to the rotation axes 4-1, 4-2 and 4-3 as indicated by arrows R 1, R 2 and R 3. is there. Therefore, if the bias of the bearing is ignored, the moment of inertia and the frictional force of the table 2 are constant without depending on the phase, and the table 2, that is, the acceleration sensor 1 holds the posture with respect to the outside world, and the arrow R0 As shown, complete constant velocity circular motion with the radius r of the link 3-1, 3-2, 3-3 is possible. As a result, the acceleration sensor 1 is simultaneously subjected to sinusoidal vibrations in the X direction and the Y direction, so that the acceleration sensor 1 can perform two-axis simultaneous measurement. Further, since the known displacement of the acceleration sensor 1 is guaranteed by a perfect circle whose radius is the length r of the links 3-1, 3-2 and 3-3, the measurement value of the acceleration sensor 1 can be corrected. .

The X-axis acceleration signal S _X and the Y-axis acceleration signal S _Y of the acceleration sensor 1 are supplied to a control circuit (computer) 10. As a result, the control circuit 10 accelerates from the X-axis acceleration signal S _X and the Y-axis acceleration signal S _Y. The X-axis displacement X and Y-axis displacement Y of the sensor 1 are calculated. If necessary, a correction value is calculated for the reference perfect circle.

  FIG. 2 is a perspective view showing an embodiment of the acceleration sensor characteristic evaluation apparatus according to the present invention. FIG. 3 is a partial sectional view of the acceleration sensor characteristic evaluation apparatus of FIG. FIG.

  As shown in FIGS. 2 and 3, the links 3-1, 3-2 and 3-3 are fixed by screws between the two support plates 5-1 and 5-2. The support plates 5-1 and 5-2 are supported by four support columns 6-1, 6-2, 6-3, and 6-4. Each of the links 3-1, 3-2 and 3-3 is represented by the distance between the rotary shafts 4-1, 4-2 and 4-3 and the holding shafts 8-1, 8-2 and 8-3 of the table 2. They have the same length r and can rotate infinitely in synchronization with r as the radius. As a result, when the links 3-1, 3-2 and 3-3 are synchronously rotated with the radius r, the table 2, that is, the acceleration sensor 1 also moves circularly with the radius r.

  In order to prevent the load from being biased during rotation, the links 3-1, 3-2, 3-3 have counterweights 7-1, 7-1 ′, 7-2, 7-2 ′, 7-3 and 7-3 ′ are provided to balance the mass. For example, in the link 3-2, C is the center of mass of the counterweights 7-2 and 7-2 ′, T is the center of mass of the entire counter 3-2 excluding the counterweights 7-2 and 7-2 ′, and S Is the center of mass of 1/3 of both the acceleration sensor 1 and the table 2. “1/3” is a value corresponding to the number of links. If the number of links is n, 1/3 becomes 1 / n. In this case, the weights of the counter weights 7-2 and 7-2 'are determined so that 1/3 of the mass of both the acceleration sensor 1 and the table 2 is applied to the holding shaft 8-2. As a result, even if the links 3-1, 3-2, and 3-3 rotate, the counter weights 7-1, 7-1 ', 7-2, 7-2', 7-3, and 7-3 ' Since the center of mass of each included link 3-1, 3-2, 3-3 is on the rotating shaft 4-1, 4-2, 4-3 of each link 3-1, 3-2, 3-3, Centrifugal force, that is, translational force is not generated on the rotating shafts 4-1, 4-2, and 4-3, and thus stable rotation can be obtained.

  Since the table 2 and the links 3-1, 3-2, 3-3 are a combination of three parallel link structures, if only one of the links 3-1, 3-2, 3-3 is driven and rotated, 3 The three links 3-1, 3-2, and 3-3 are driven to rotate synchronously. 2 and 3, only the link 3-3 is driven by the drive motor 9 via the rotating plate 9a.

  Further, assuming that the apparatus is placed vertically and the acceleration sensor 1 always operates while receiving gravitational acceleration g, the respective mass centers C, T, and S are made to coincide in the height direction of the apparatus. Therefore, almost no torque is required when the apparatus is rotated at any inclination, and a very smooth rotation can be expected, and the apparatus can be miniaturized.

  Next, the operation of the control circuit 10 of FIG. 2 will be described with reference to the flowchart of FIG.

First, in step 401, the drive motor 9 shown in FIGS. 2 and 3 is operated to excite the table 2, that is, the acceleration sensor 1 at, for example, 0.1 Hz. In this state, the digital X-axis acceleration signal S _X and Y-axis acceleration signal S _Y of the acceleration sensor 1 shown in FIG. 5 are captured at a sampling rate of 20 Hz, for example, and stored.

Next, in step 402, an offset correction process is performed by subtracting the average value of the X-axis acceleration signal S _X and Y-axis acceleration signal S _{Y taken} in step 401 from the entire data.

  Next, in step 403, baseline correction processing is performed.

  Next, in step 404, bandpass filtering processing is performed. For example, set the high-frequency cut frequency to 1 Hz to remove noise caused by machine processing accuracy, mounting accuracy, etc., and set the low-frequency cut frequency to 0.09 Hz to remove components below the excitation frequency of 0.1 Hz to eliminate accumulation errors. .

Next, in step 405, X-axis displacement X and Y-axis displacement Y are calculated by second-order integration of the X-axis acceleration signal S _X and the Y-axis acceleration signal S _Y , and the displacement locus shown in FIG. obtain.

Finally, in step 406, the displacement trajectory created in step 405 is corrected by comparing it with a known perfect circular trajectory whose radius is the length r of the links 3-1, 3-2, 3-3 of the device. Calculate the value. For example, in FIG. 6, the maximum amplitude of the X-direction displacement X is shifted by about 10% from the maximum amplitude of the known perfect circular locus, and the maximum amplitude of the Y-direction displacement Y is 20% from the maximum amplitude of the known perfect circular locus. There is a deviation. In this case, the correction value α _X for the X-direction displacement X is set to 1 / 0.9, and the correction value α _Y for the Y-direction displacement Y is set to 1 / 0.8. The correction values α _X and α _Y depend on the sensitivity of the main axis (X axis) of the acceleration sensor 1, the sensitivity of the sub axis (Y axis), the calculation error of the second order integration, the mounting angle of the acceleration sensor 1, and the like.

  The X-direction displacement X and the Y-direction displacement Y in the above-described steps 405 and 406 include a phase shift, but if the excitation in step 401 is not frequency-dependent, as described above, the X-direction displacements X and Y The sensitivity of the acceleration sensor 1 can be measured by obtaining each maximum amplitude of the directional displacement Y and comparing it with each maximum amplitude of a known perfect circular locus. However, when the excitation in step 401 according to the present invention is frequency-dependent, the phase is synchronized with the output of a rotary encoder (not shown) provided on the rotary plate 9a or the like to adjust the phase. The direction displacement X and the Y direction displacement Y can be obtained, and the sensitivity of the acceleration sensor 1 at the frequency can be measured.

  In the above-described embodiment, the number of links 3-1, 3-2, and 3-3 is set to 3 in consideration of control stability, processing accuracy, etc., but the number of links is 2 or 4 or more. May be. The acceleration sensor 1 is, for example, an inexpensive capacitive acceleration sensor, but the present invention can also be applied to other acceleration sensors.

1: Acceleration sensor 2: Tables 3-1, 3-2, 3-3: Links 4-1, 4-2, 4-3: Rotating shaft 5-1, 5-2: Support plates 6-1, 6 2, 6-3, 6-4: support columns 7-1, 7-1 ′, 7-2, 7-2 ′, 7-3, 7-3 ′: counterweights 8-1, 8-2, 8 -3: holding shaft 9: drive motor 9a: rotating plate 10: control circuit
S _X : X-axis acceleration signal
S _Y : Y-axis acceleration signal

Claims (3)

A table for fixing the acceleration sensor;
Three links that are connected to the table and have the same length and are infinitely rotatable and parallel;
A single rotating plate provided on one of the three links;
An acceleration sensor characteristic evaluation apparatus comprising: a single drive motor for rotating the rotating plate to synchronously drive the three links .   Furthermore, the acceleration sensor characteristic evaluation apparatus of Claim 1 which provided the counterweight according to the mass of the said acceleration sensor and the said table in each said link on the opposite side to this table. The acceleration sensor characteristic evaluation apparatus according to claim 2, wherein a mass center of the acceleration sensor and the table, a mass center of each link, and a mass center of the counterweight coincide with each other in a height direction of the apparatus.

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