Structural health monitoring system and orientation error compensation method

Abstract

Reduce the detection error of the vibration sensor. [Solution] The structural health monitoring system generates a first band-limited frequency component by limiting the bandwidth of the first frequency component of the nth-order acceleration, generates first time history data approximating the nth-order acceleration, generates first displacement time history data, determines a first point from the distance from the first origin of the nth-order coordinates among the points indicated by the first displacement time history data on the nth-order coordinate plane, derives a first direction which is the direction from the first origin looking towards the first point, generates a second band-limited frequency component by limiting the bandwidth of the second frequency component of the m-th-order acceleration, generates second time history data approximating the m-th-order acceleration, generates second displacement time history data, determines a second point from the distance from the second origin of the m-th-order coordinates among the points indicated by the second displacement time history data on the m-th-order coordinate plane, derives a second direction which is the direction from the second origin looking towards the second point, and determines the amount of azimuth error compensation using the difference between the first direction and the second direction.

Description

Technical Field

[0001] The present invention relates to a structural health monitoring system and an azimuth error compensation method.

Background Art

[0002] A structural health monitoring system (vibration detection system) uses vibration sensors installed on each floor of a building to detect vibrations generated in the building. The structural health monitoring system estimates the structural soundness of the building using the detection results from such vibration sensors. For example, the structural health monitoring system estimates the degree of impact that an earthquake has on the building based on the magnitude of inter-story displacement (magnitude of inter-story deformation angle) between two vertically related floors of the building and changes in the natural vibration (natural frequency) of the building, and estimates the soundness of the building based on this. The detection error of the aforementioned vibration sensors may be related to the estimation accuracy of such a structural health monitoring system. Such vibration sensors are arranged at predetermined positions in alignment with a predetermined direction through installation work, but at that time it is difficult to align the direction of each vibration sensor to the predetermined direction, and there have been proposals to solve this problem.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, there has been a demand to reduce the influence of the detection error of vibration sensors by a simpler method.

[0005] This invention has been made in view of the above circumstances, and the object of this invention is to provide a structural health monitoring system and an orientation error compensation method that can reduce the detection error of vibration sensors that detect the movement of floors in a building. [Means for solving the problem]

[0006] (1) The present invention has been made to solve the above problems, and a structural health monitoring system according to a first aspect of the present invention comprises: an nth-floor acceleration sensor for detecting the acceleration of the nth floor of a building; an mth-floor acceleration sensor for detecting the acceleration of the mth floor of the building; and an angle compensation amount calculation unit for determining the amount of compensation for directional error, wherein the angle compensation amount calculation unit generates a first band-limited frequency component by limiting the bandwidth of the first frequency component from the first frequency component of the acceleration of the nth floor so as to include the natural frequency of the building and not include higher-order components; generates a first time history data approximating the acceleration of the nth floor from the first band-limited frequency component; generates first displacement time history data from the first time history data; and determines a first based on the distance from the first origin of the coordinates of the nth floor among the points indicated by the first displacement time history data on the coordinate plane of the nth floor The structural health monitoring system determines a point, derives a first direction which is the direction from the first origin to the first point, generates a second band-limited frequency component which limits the bandwidth of the second frequency component of the acceleration of the m floor to include the building's natural frequency and not include higher-order components, generates a second time history data which approximates the acceleration of the m floor from the second band-limited frequency component, generates a second displacement time history data from the second time history data, determines a second point on the coordinate plane of the m floor based on the distance from the second origin of the coordinates of the m floor among the points indicated by the second displacement time history data, derives a second direction which is the direction from the second origin to the second point, and determines the amount of compensation for the azimuth error using the difference between the first direction and the second direction. (2) In the structural health monitoring system according to the above embodiment, the angle compensation amount calculation unit sets the first point to the point where the distance from the first origin is maximum, and the second point to the point where the distance from the second origin is maximum. (3) In the structural health monitoring system according to the above embodiment, the nth-order acceleration sensor is mounted on a first housing and outputs components of an orthogonal coordinate system having axes in a direction associated with the reference direction of the first housing, the mth-order acceleration sensor is mounted on a second housing and outputs components of an orthogonal coordinate system having axes in a direction associated with the reference direction of the second housing, and the angle compensation amount calculation unit determines the amount of compensation for the azimuth error caused by the error in the mounting direction of the nth-order acceleration sensor and the mth-order acceleration sensor. (4) A second aspect of the present invention is a method for compensating an orientation error in a structural health monitoring system, comprising: an nth-floor acceleration sensor for detecting the acceleration of the nth floor of a building; an mth-floor acceleration sensor for detecting the acceleration of the mth floor of the building; and an angle compensation amount calculation unit for determining the amount of compensation for orientation error, wherein a first band-limited frequency component is generated from a first frequency component of the acceleration of the nth floor, with the bandwidth of the first frequency component limited to include the natural frequency of the building and not include higher-order components; a first time history data approximating the acceleration of the nth floor is generated from the first band-limited frequency component; first displacement time history data is generated from the first time history data; and a first point is determined on the coordinate plane of the nth floor based on the distance from the first origin of the coordinates of the nth floor among the points indicated by the first displacement time history data. The orientation error compensation method includes: deriving a first direction which is the direction from the first origin to the first point; generating a second band-limited frequency component by limiting the bandwidth of the second frequency component of the acceleration of the m floor so that it includes the natural frequency of the building but does not include higher-order components; generating a second time history data that approximates the acceleration of the m floor from the second band-limited frequency component; generating a second displacement time history data from the second time history data; determining a second point on the coordinate plane of the m floor based on the distance from the second origin of the coordinates of the m floor among the points indicated by the second displacement time history data; deriving a second direction which is the direction from the second origin to the second point; and determining the amount of compensation for the orientation error using the difference between the first direction and the second direction. [Effects of the Invention]

[0007] According to the present invention, the detection error of vibration sensors used to detect the movement of building layers can be reduced. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example of a building BL to which the structural health monitoring system 1 of the embodiment is applied. [Figure 2] This figure shows the configuration of the structural health monitoring system 1 in an embodiment. [Figure 3]This figure shows an example of a computer system in an embodiment. [Figure 4] This is a flowchart showing the error compensation procedure for the embodiment. [Figure 5] This diagram illustrates the azimuth error that occurs when the sensor of the embodiment is installed facing the reference direction. [Figure 6] This is a diagram illustrating the compensating process for azimuth errors in the embodiment. [Figure 7] This is a diagram illustrating the compensating process for azimuth errors in the embodiment. [Figure 8] This is a flowchart of the compensating process for the orientation error in the embodiment. [Figure 9] This is a diagram illustrating the characteristics of the bandpass filter in the embodiment. [Modes for carrying out the invention]

[0009] The structural health monitoring system and orientation error compensation method of the embodiment will be described below with reference to the figures. Note that the building shown in the following embodiment is just one example of a structure.

[0010] The structural health monitoring system 1 of this embodiment will be described below with reference to the figures. Figure 1 is a diagram showing an example of a building BL (structure) to which the structural health monitoring system 1 of this embodiment is applied. The structural health monitoring system 1 estimates the soundness of the building BL (structure).

[0011] The building BL shown in Figure 1 is a low-rise building with four above-ground floors, one basement floor, and one penthouse floor. The structural type of building BL is steel frame for the above-ground floors and reinforced concrete for the basement floors, etc. Figure 1(a) shows the floor plan of building BL, and Figure 1(b) shows the structural frame diagram. A predetermined number of dampers may be installed in building BL. The positions and number of dampers shown in the figures are arbitrary and not limited to those shown in the figures; any dampers necessary for building BL may be installed.

[0012] Figure 2 is a diagram showing the configuration of the structural health monitoring system 1 in the embodiment. In Figure 2, the structural health monitoring system 1 receives, via a communication line, data from acceleration sensors S0 to S provided in the building BL n (0 indicates the foundation, and 1 to n indicate the number of floors (k) of the building BL, including the rooftop.) Acceleration data is supplied as vibration data due to earthquakes or the like from each of the sensors. The vibration data due to earthquakes or the like may be based not only on vibrations caused by natural phenomena such as earthquakes and wind, but also on artificial vibrations such as vibrations generated using a shaker.

[0013] The acceleration sensor S0 is provided to measure the acceleration at the foundation portion of the building BL, and the vibration data measured due to earthquakes or the like is output to the structural health monitoring system 1 via the information communication network as acceleration data. For example, when there is no basement floor BF, the acceleration sensor S0 is provided at the foundation or the first floor of the building BL.

[0014] Further, the acceleration sensors S1 to S n Each of the sensors outputs the vibration data measured at the first floor to the n-th floor to the structural health monitoring system 1 via the information communication network as acceleration data.

[0015] Here, the acceleration sensors are installed on each floor of the building BL as shown in Figure 2. In the case of the building BL in Figure 2, the acceleration sensor S1 is installed on the first floor (Z1), the acceleration sensor S2 is installed on the second floor (Z2), the acceleration sensor S3 is installed on the third floor (Z3), the acceleration sensor S4 is installed on the fourth floor (Z4), and the acceleration sensor S5 is installed on the rooftop (Z5). Further, the acceleration sensor S0 is installed on the basement floor BF (foundation portion) of the building BL. Note that the acceleration sensors do not have to be installed on all floors. In the following description, when the acceleration sensors S o to the acceleration sensor S5 are collectively referred to, they are simply called the acceleration sensor S. The acceleration sensor S is an example of a vibration detection device.

[0016] The structural health monitoring system 1 includes, for example, a computer. The structural health monitoring system 1 includes a deformation degree derivation unit 20, an angle compensation amount calculation unit 30, a building soundness evaluation unit 80, and a storage unit 10. The deformation degree derivation unit 20 acquires the vibrations respectively detected by the acceleration sensors S from each of the acceleration sensors S, and writes and stores them in the storage unit 10 as time-series information. The angle compensation amount calculation unit 30 refers to the time-series information in the storage unit 10 to determine the compensation amount for the azimuth error caused by construction accuracy and the like at the time of installation of the acceleration sensor S. The angle compensation amount calculation unit 30 corrects the acceleration time-series information stored in the storage unit 10 using the azimuth error compensation amount, and adds the corrected acceleration time-series information to the storage unit 10. The deformation degree derivation unit 20 uses the corrected acceleration time-series information to calculate various quantities for building soundness evaluation. For example, the deformation degree derivation unit 20 derives the magnitude of inter-story displacement (magnitude of inter-story deformation angle) of two vertically related stories of the building BL, and the natural vibration (natural frequency) of the building BL. The deformation degree derivation unit 20 writes and stores the derived magnitude of inter-story displacement (magnitude of inter-story deformation angle) and the natural vibration (natural frequency) of the building BL in the storage unit 10 as time-series information.

[0017] The building soundness evaluation unit 80 estimates the soundness of the building BL, for example, after vibration from an earthquake arrives at the building BL, based on the history information of the magnitude of inter-story displacement (magnitude of inter-story deformation angle) and the natural vibration (natural frequency) of the building BL held in the storage unit 10 corresponding to the vibration from the earthquake. The building soundness evaluation unit 80 is an example of a soundness estimation control unit. For details of the processing for estimating the soundness of the building BL, reference may be made to, for example, Japanese Patent Laid-Open No. 2014-016249.

[0018] The structural health monitoring system 1 compensates for the detection error of the acceleration sensor S used in the above-described processing for estimating the soundness of the building BL, thereby improving the accuracy of the processing for estimating the soundness of the building BL. Hereinafter, this will be described in order.

[0019] Figure 4 is a flowchart showing the error compensation procedure of the embodiment. The workers perform installation work including the acceleration sensor S (SS2, system installation). For example, the workers perform a check (individual unit inspection) to ensure that there are no problems with the installation accuracy of the acceleration sensor S during this process. After the installation work is completed, a comprehensive adjustment test and quality inspection of the structural health monitoring system 1 will be conducted (SS4, comprehensive adjustment test). By following these steps, the installation accuracy of the acceleration sensor S is guaranteed to be the same as that confirmed in the individual inspection during the "system installation" described above, and the structural health monitoring system 1 becomes available. At this stage, the judgment accuracy of the structural health monitoring system 1 is equivalent to that of the comparative example. In response to this, this embodiment includes the following step to further improve the judgment accuracy of the structural health monitoring system 1. This step allows the structural health monitoring system 1 to compensate for errors that could not be eliminated during the installation process by using analytical methods to cancel them out. This step involves starting the operation of the structural health monitoring system 1, which has been confirmed to be free of problems in the quality inspection following the comprehensive adjustment test described above (SS5, operation commencement). If an earthquake occurs afterward, the acceleration sensor S detects the acceleration caused by the earthquake's shaking. The structural health monitoring system 1 records the detection result (SS6, earthquake record acquisition). Based on the detection result, the structural health monitoring system 1 detects that an earthquake has occurred at building BL and performs the following processing. For example, the structural health monitoring system 1 performs compensation processing to cancel out the detection error of the acceleration sensor S (SS7, detection error compensation processing). The details of this process will be explained below in order.

[0020] Figure 5 is a diagram illustrating the azimuth error that occurs when the sensor of the embodiment is installed facing the reference direction. As shown in Figure 5, sensors capable of detecting vibrations in the X-axis and Y-axis directions are placed on each floor of the building. On each floor, the X and Y axes are determined, oriented toward a common orientation (reference direction). This direction serves as the reference direction when determining the orientation in which sensors are installed.

[0021] For example, the X-axis can be defined along the axial direction of the building, and the Y-axis can be defined perpendicular to the axial direction. The directions of the X and Y axes described above are just examples, and they can be set in any direction as appropriate without being limited to these.

[0022] As described above, even if the reference direction is specified in the design, azimuth errors may occur during the installation process when mounting the sensor facing the reference direction. Furthermore, when determining the X-axis and Y-axis directions toward a common orientation (reference direction) on each floor by marking out lines, orientation errors may occur due to the marking-out process.

[0023] Such directional errors caused by marking out and installation work occur on each floor, affecting the accuracy of the relative displacement analysis using time history information of vibrations between floors. Even when taking care to avoid directional errors caused by marking out and installation work, it is impossible to completely eliminate these directional errors.

[0024] For example, ideally, when installing a sensor, the sensor's x-axis direction and y-axis direction should coincide with the building's x-axis direction and y-axis direction, respectively. For example, assuming the sensor is installed without any directional error, vibrations in the building's Y-axis direction will be detected as a component of vibrations in the sensor's Y-axis direction, but not as a component of vibrations in the sensor's X-axis direction. The same applies to vibrations in the building's X-axis direction.

[0025] However, if an azimuth error occurs during sensor installation, the sensor's x-axis and y-axis directions will not coincide with the building's x-axis and y-axis directions. Therefore, even if the building only shakes in the Y-axis direction and not in the X-axis direction, the sensors on each floor will detect a component of vibration in the X-axis direction that is caused by the directional error, and the vibration component in the Y-axis direction will be affected by the directional error more than the value that should be detected under ideal conditions.

[0026] Therefore, in this embodiment, a correction process is performed on the vibration data to cancel out the effects of the above-mentioned azimuth error. This correction process will be explained in more detail below.

[0027] Figure 6 is a diagram illustrating the compensating process for azimuth errors in the embodiment. Figure 8 is a flowchart of the direction error compensation process in the embodiment.

[0028] (STEP 0: Earthquake detection) At the stage after the acceleration sensor S is installed in building BL and before the azimuth error has been adjusted (Figure 6(a)), the occurrence of an earthquake exceeding a predetermined magnitude is detected. The results of the vibration detection caused by this earthquake are used in the azimuth error compensation process shown below.

[0029] (STEP 1: Acquisition of acceleration data) Each floor's acceleration sensor S outputs, for example, instantaneous values ​​of acceleration in the sensor's x-axis direction and sensor's y-axis direction. At this stage, the output of each acceleration sensor S includes an azimuth error. The structural health monitoring system 1 acquires the acceleration detection results from each acceleration sensor S as time history information.

[0030] (STEP 2: Preprocessing for peak search) The median of the time history information for the detected acceleration may contain a DC component (offset). When this DC component is present, and when this DC component tends to change gradually (trend), it becomes difficult to distinguish it from changes in frequency components that are close to DC. Therefore, the angle compensation amount calculation unit 30 may perform any or all of the following calculations in order to reduce errors caused by the influence of a specific calculation method.

[0031] (1) Baseline correction processing using the least squares method This calculation removes the DC component and the frequency component (trend) that is close to DC from the time history information of the acceleration. (2) For the data of the time history information of acceleration over the target period, a window function corresponding to the number of data points of a predetermined time length is used to emphasize the periodic changes within the target period and smooth the changes at the ends of the target period. For example, a Parzen window may be used as this window function. (3) The Discrete Fourier Transform (FFT) operation is suitable for application to 2^n time history information. If the number of time history data is less than this number of data, data with a value of 0 is added after the time history data so that the number of time history data is 2^n, thereby supplementing the missing data. The angle compensation amount calculation unit 30 may perform the above processing prior to the Fourier transform processing described later.

[0032] (STEP 3: Fourier transform processing of acceleration time history information) The angle compensation amount calculation unit 30 performs a Fourier transform (complex Fourier transform) on the time history data of acceleration that has undergone the above preprocessing for each of the sensor X-axis component and sensor Y-axis component of the acceleration sensor S on each floor (Figure 6(b)).

[0033] (STEP 4: Searching for the peak frequency of the building's response characteristics) The angle compensation amount calculation unit 30 searches for the frequency that indicates the peak of the building's response characteristics. The frequency that indicates the peak of the response characteristics is simply called the peak frequency or the peak frequency of the response characteristics. For example, the angle compensation amount calculation unit 30 estimates the response characteristics of the building based on the results of the Fourier transform processing of the time history information of the displacement, and searches for the frequency (peak frequency) at which the response characteristics (gain) peak within those response characteristics. More specifically, (1) Based on the (top-level Fourier spectrum) and (bottom-level Fourier spectrum), calculate the response characteristics (transfer function) of each frequency component. (2) Based on the natural frequency of the building (estimated primary natural frequency of the building) obtained in advance from design information, microtremor measurement results, etc., an arbitrary frequency band width including that natural frequency is set. (3) Within this arbitrary range, the point (peak frequency) where the above response characteristic (transfer function) peaks is determined to be the building's primary natural frequency. The angle compensation amount calculation unit 30 performs the above processing on the time history data of the sensor's X-axis component and the time history data of the sensor's Y-axis component, respectively.

[0034] (STEP 5: Preprocessing for displacement calculation) As described above (STEP 2), the median of the time history information of the detected acceleration may contain a DC component (offset). When this DC component is present, and when this DC component tends to change gradually (trend), it becomes difficult to distinguish it from changes in frequency components that are close to DC. Furthermore, in this embodiment, the displacement is calculated using the time history information of the acceleration in a later processing step. The DC component of the acceleration detection error affects the displacement calculation result. Therefore, the angle compensation amount calculation unit 30 may perform the following calculations to reduce errors caused by the influence of a specific calculation method.

[0035] (1) Baseline correction processing using the least squares method This calculation removes the DC component and frequency components (trends) that are close to DC. (2) The Discrete Fourier Transform (FFT) operation is suitable for application to 2^n time history information. If the number of time history data is less than this number of data, data with a value of 0 is added after the time history data so that the number of time history data is 2^n, thereby filling in the missing data. The angle compensation amount calculation unit 30 may perform the above processing prior to the Fourier transform processing for deriving the frequency component of the displacement, which will be described later. The angle compensation amount calculation unit 30 performs the above processing on the time history data of the sensor's X-axis component and the time history data of the sensor's Y-axis component, respectively.

[0036] (STEP 6: Fourier transform processing of acceleration time history information) The angle compensation amount calculation unit 30 performs a Fourier transform (complex Fourier transform) on the time history data of acceleration data that has undergone the above preprocessing, for each of the sensor X-axis component and sensor Y-axis component of the acceleration sensor S on each floor. In the case of the STEP2-4 processing described above, the process is configured to apply a window function in STEP2 to enhance the peaks in the resulting spectrum. In STEP 5-6, the application of a window function is omitted to reduce the characteristic changes in the frequency range being analyzed.

[0037] (STEP 7: Bandpass filtering) The angle compensation calculation unit 30 performs band limiting on the spectrum obtained from the Fourier transform processing in STEP 6, using a bandpass filter with predetermined bandpass characteristics, to suppress frequencies outside the range of the first-order mode component of the oscillation (Figure 6(c)). Specifically, the band limiting calculation is performed by multiplying the above spectral value by the bandpass characteristic value.

[0038] (STEP 8: Inverse Fourier Transform) The angle compensation amount calculation unit 30 performs an inverse Fourier transform on the spectrum containing the first-order mode component of the oscillation from the calculation result of STEP 7. For example, the inverse Fourier transform processing of the angle compensation amount calculation unit 30 reconstructs time history information of acceleration in the sensor's y-axis direction from the spectrum containing the first-mode component of vibration in the sensor's y-axis direction. In this time history information of acceleration, higher-order frequency components are removed, and the main component becomes the intrinsic frequency component of acceleration in the sensor's y-axis direction. The angle compensation amount calculation unit 30 performs the same operation for the sensor x-axis direction. Furthermore, if the angle compensation amount calculation unit 30 interpolates "zero points" in the process of STEP 5 (2) above, it excludes the range in which "zero points" were interpolated in the process of STEP 5 (2) above from the following processes based on the result of the inverse Fourier transform.

[0039] (STEP 9: Integral calculation to obtain estimated displacement) The angle compensation amount calculation unit 30 obtains time history information of displacement in each axis direction by integrating the time history information of acceleration in each axis direction from the calculation result of STEP 8. For example, the angle compensation amount calculation unit 30 performs this complex inverse Fourier transform and integration process on the acceleration spectrum of the sensor's vibration in the y-axis direction to reconstruct the time history information of the sensor's displacement in the y-axis direction. Similarly, by performing this complex inverse Fourier transform and integration process on the acceleration spectrum of the sensor's vibration in the x-axis direction, the time history information of the sensor's displacement in the x-axis direction is reconstructed.

[0040] For example, the angle compensation amount calculation unit 30 may perform this integral calculation in the following procedure. (1) Perform an integral operation on the time history information of acceleration to obtain the time history information of velocity. (2) Baseline correction processing is performed on the time history information of the speed using the least squares method. This calculation removes the DC component and frequency components (trends) that are close to DC. (3) The time history information of the velocity after baseline correction processing is integrated to obtain the time history information of the displacement. (4) A bandpass filter with a predetermined frequency characteristic is applied to the time history information of the displacement to limit the bandwidth. By applying this bandpass filter, DC components and frequency components close to DC (trends) are removed. The frequency characteristics of this bandpass filter will be described later.

[0041] (STEP 10: Process to convert to polar coordinates) The time history information of the displacement in each axis direction from the calculation results of STEP 9 is denoted as displacement ndx(t) and ndy(t). The angle compensation amount calculation unit 30 converts these Cartesian coordinate system displacements ndx(t) and ndy(t) to polar coordinates (distance nr(t), angle nθ(t)) using, for example, the following equation (Figure 7(d)). Note that "n" indicates the floor on which the acceleration sensor S is located. The same applies hereafter.

[0042] nr(t) = √(ndx(t)) 2+ndy(t) 2 ) nθ(t) = cos(ndx(t) / nr(t))

[0043] The angle compensation amount calculation unit 30 performs the above calculation for each acceleration sensor S on each floor.

[0044] (STEP 11: Process to detect the angle of the point that is the maximum distance from the origin in polar coordinates) The angle compensation calculation unit 30 detects the point where the distance nr(t) is maximized from the time-series information of the displacement, which is shown as a pair of distance nr(t) and angle nθ(t) in polar coordinates as a result of the calculation in STEP 10, and detects the angle nθ(t) that point makes with the x-axis. This detected angle is denoted as nθmax. The angle compensation amount calculation unit 30 performs the above calculation for each acceleration sensor S on each floor.

[0045] (STEP 12: Process to calculate the orientation error of the acceleration sensors S on the upper and lower floors) The angle compensation amount calculation unit 30 uses the calculation result from STEP 11 to calculate the azimuth error Δnθ of the acceleration sensors S on the upper and lower floors using the azimuth errors of the acceleration sensors S on the two adjacent floors (for example, the nth floor and the (n-1)th floor).

[0046] Δnθ = nθmax - n-1θmax

[0047] The resulting azimuth error Δnθ is the relative angle between the nth floor and the (n-1)th floor acceleration sensor S. For example, the angle compensation calculation unit 30 uses the angle θ(t) of the ground floor as a reference and sequentially adds the azimuth error Δnθ of each floor. For example, Figure 7(e) shows an example of a memory area that stores the angle θ(t) of the acceleration sensor S on each floor. As shown here, if the angle θ(t) of the acceleration sensor S on the ground floor is 45 degrees with respect to the building's X-axis direction, then the orientation error Δ1θ between the ground floor (1st floor) and the 2nd floor will be 44.5 degrees, which is the ground floor angle of 45 degrees plus (-0.5) degrees. By repeating this process up to the acceleration sensor S on the top floor or rooftop, an angle that compensates for the orientation error of the acceleration sensor S on each floor can be obtained (Figure 7(f)). It is preferable to use the acceleration sensor S on the ground floor or in the underground foundation as the reference. It is expected that the detection result of the reference acceleration sensor S will be close to the vibration at the installation location of the building BL.

[0048] The above process corrects the azimuth error included in the detection result of the acceleration sensor S so that it is reduced.

[0049] Referring to Figure 9, an example of the characteristics of the bandpass filter in this embodiment will be described. Figure 9 is a diagram illustrating the characteristics of the bandpass filter of the embodiment. Figure 9 shows the transfer characteristics of the bandpass filter of the embodiment. The passband gain of this filter is normalized to 1. This passband includes the searched first natural frequency f and is positioned on the frequency axis f(x) with respect to the first natural frequency f. The lower frequency limit of the passband is denoted by fl1, and the upper frequency limit is denoted by fu1. fl1 and fu1 may be defined using the following equations.

[0050] fl1 = f / n fu1 = f × n

[0051] The upper frequency limit of the low-frequency cutoff is denoted by fl2, and the lower frequency limit of the high-frequency cutoff is denoted by fu2. fl2 and fu2 may be defined using the following formulas.

[0052] fl² = f / 1.25 fu² = f × 1.25

[0053] The gain from fl2 to fl2 is defined using the following formula.

[0054] 1 / 2×(1-cos((f(x)-fl2) / (fl1-fl2)×n)

[0055] The gain from fu1 to fu2 is defined using the following equation.

[0056] 1 / 2×(1-cos(1-(f(x)-fl2) / (fl1-fl2)×n)

[0057] Note that n in the above formula is a coefficient and can be set to any value. The value of n applied to Figure 9 is an example where n is greater than 0 and less than 1.25.

[0058] The transfer function shown in Figure 9 is just one example and may be modified as appropriate without altering the essence of the invention.

[0059] The structural health monitoring system 1 of the above embodiment generates a first band-limited frequency component by limiting the bandwidth of the first frequency component of the nth-order acceleration, generates first time history data approximating the nth-order acceleration, generates first displacement time history data, determines a first point from the points indicated by the first displacement time history data on the nth-order coordinate plane based on the distance from the first origin of the nth-order coordinates, and derives a first direction which is the direction from the first origin looking towards the first point. The structural health monitoring system 1 generates a second band-limited frequency component by limiting the bandwidth of the second frequency component of the m-th-order acceleration, generates second time history data approximating the m-th-order acceleration, generates second displacement time history data, determines a second point from the points indicated by the second displacement time history data on the m-th-order coordinate plane based on the distance from the second origin of the m-th-order coordinates, and derives a second direction which is the direction from the second origin looking towards the second point. The structural health monitoring system 1 determines the amount of azimuth error compensation using the difference in angle between the first direction and the second direction described above. This makes it possible to reduce the detection error of vibration sensors that detect movement in the layers of a building.

[0060] The embodiments of the present invention have been described above, but the structural health monitoring system 1 has a computer system (Figure 3) inside. The series of processes related to the above-described process are stored in the form of a program on a computer-readable storage medium, and the above process is performed when the computer (CPU 1A) reads and executes this program. Here, the computer-readable storage medium refers to a magnetic disk, magneto-optical disk, CD-ROM, DVD-ROM, semiconductor memory (1B), etc. Alternatively, this computer program may be distributed to a computer via a communication line through a communication interface 1D, and the computer that receives this distribution executes the program. Furthermore, the term "computer system" here includes an OS, etc. Information from the acceleration sensor S may also be collected via the communication interface 1D.

[0061] Although one embodiment of the present invention has been described above, the embodiments of the present invention are not limited to those described above. Embodiments of the present invention can be, for example, obtained by modifying the above embodiments as follows.

[0062] (Note) (1) The structural health monitoring system of the embodiment is An nth-floor accelerometer that detects the acceleration of the nth floor of a building, The m-th floor acceleration sensor detects the acceleration of the m-th floor of the building, An angle compensation amount calculation unit that determines the amount of compensation for azimuth error, Equipped with, The angle compensation amount calculation unit, A first band-limited frequency component is generated by limiting the bandwidth of the first frequency component from the first frequency component of the acceleration of the nth floor so that it includes the natural frequency of the building but does not include higher-order components. The first time history data approximating the nth-order acceleration is generated from the first band-limited frequency component. First displacement time history data is generated from the first time history data, A first point is determined on the nth-order coordinate plane based on the distance from the first origin of the nth-order coordinates from among the points indicated by the first displacement time history data, and a first direction is derived which is the direction from the first origin to the first point. The angle compensation amount calculation unit, A second band-limited frequency component is generated by limiting the bandwidth of the second frequency component from the second frequency component of the acceleration of the mth floor so that it includes the natural frequency of the building but does not include higher-order components. The second time history data approximating the m-th-order acceleration is generated from the second band-limiting frequency component. A second displacement time history data is generated from the second time history data. A second point is determined from among the points indicated by the second displacement time history data on the m-th coordinate plane based on its distance from the second origin of the m-th coordinate system, and a second direction is derived which is the direction from the second origin to the second point. The angle compensation amount calculation unit, The amount of compensation for the azimuth error is determined using the difference between the first direction and the second direction. This is a structural health monitoring system. (2) In the structural health monitoring system described in (1) above, The angle compensation amount calculation unit, Let the first point be the point that is the maximum distance from the first origin, The second point should be the point that is the maximum distance from the second origin. (3) In the structural health monitoring system described in (1) and (2) above, The nth-order accelerometer is, It is mounted in the first enclosure, Output the components of a Cartesian coordinate system having axes in the direction associated with the reference direction of the first housing. The aforementioned m-th-order acceleration sensor is It is mounted in the second enclosure, Output the components of a Cartesian coordinate system having axes in the direction associated with the reference direction of the second housing, The angle compensation amount calculation unit, It is preferable to determine the amount of compensation for the azimuth error caused by the error in the installation direction of the nth-order acceleration sensor and the mth-order acceleration sensor. [Explanation of Symbols]

[0063] 1. Structural Health Monitoring System 10 Storage section 20 Deformation degree derivation section 30 Angle compensation amount calculation unit 80 Building Integrity Assessment Department S Acceleration sensor (vibration detection device) BL Building

Claims

1. An nth-floor accelerometer that detects the acceleration of the nth floor of a building, The m-th floor acceleration sensor detects the acceleration of the m-th floor of the building, An angle compensation amount calculation unit that determines the amount of compensation for azimuth error, Equipped with, The angle compensation amount calculation unit, A first band-limited frequency component is generated by limiting the bandwidth of the first frequency component from the first frequency component of the nth-order acceleration so that it includes the natural frequency of the building but does not include higher-order components. The first time history data approximating the nth-order acceleration is generated from the first band-limited frequency component. First displacement time history data is generated from the first time history data, A first point is determined from among the points indicated by the first displacement time history data on the nth-order coordinate plane based on its distance from the first origin of the nth-order coordinates, and a first direction is derived which is the direction from the first origin to the first point. The angle compensation amount calculation unit, A second band-limited frequency component is generated by limiting the bandwidth of the second frequency component from the m-th floor acceleration so that it includes the building's natural frequency and does not include higher-order components. The second time history data approximating the m-th-order acceleration is generated from the second band-limiting frequency component. A second displacement time history data is generated from the second time history data. A second point is determined from among the points indicated by the second displacement time history data on the m-th coordinate plane based on its distance from the second origin of the m-th coordinate system, and a second direction is derived which is the direction from the second origin to the second point. The angle compensation amount calculation unit, The amount of compensation for the azimuth error is determined using the difference between the first direction and the second direction. Structural health monitoring system.

2. The angle compensation amount calculation unit, Let the first point be the point that is the maximum distance from the first origin, Let the second point be the point where the distance from the second origin is maximized. The structural health monitoring system according to claim 1.

3. The nth-order accelerometer is, It is mounted in the first enclosure, Output the components of a Cartesian coordinate system having axes in a direction associated with the reference direction of the first housing, The m-th accelerometer is, It is mounted in the second enclosure, Output the components of a Cartesian coordinate system having axes in the direction associated with the reference direction of the second housing, The angle compensation amount calculation unit, The amount of compensation for the azimuth error caused by the error in the installation direction of the nth-th accelerometer and the mth-th accelerometer is determined. The structural health monitoring system according to claim 1.

4. An nth-floor accelerometer that detects the acceleration of the nth floor of a building, The m-th floor acceleration sensor detects the acceleration of the m-th floor of the building, An angle compensation amount calculation unit that determines the amount of compensation for azimuth error, A method for compensating for orientation errors in a structural health monitoring system, comprising: A first band-limited frequency component is generated by limiting the bandwidth of the first frequency component from the first frequency component of the nth-order acceleration so that it includes the natural frequency of the building but does not include higher-order components. The first time history data approximating the nth-order acceleration is generated from the first band-limited frequency component. First displacement time history data is generated from the first time history data, The first point is determined from among the points indicated by the first displacement time history data on the nth-order coordinate plane based on its distance from the first origin of the nth-order coordinates, and the first direction is derived which is the direction from the first origin to the first point. A second band-limited frequency component is generated by limiting the bandwidth of the second frequency component from the m-th floor acceleration so that it includes the building's natural frequency and does not include higher-order components. The second time history data approximating the m-th-order acceleration is generated from the second band-limiting frequency component. A second displacement time history data is generated from the second time history data. The process involves determining a second point from among the points indicated by the second displacement time history data on the m-th coordinate plane based on its distance from the second origin of the m-th coordinate system, and deriving a second direction which is the direction from the second origin towards the second point. The amount of compensation for the azimuth error is determined using the difference between the first direction and the second direction. A method for compensating for azimuth errors, including the method itself.

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