Bridge vibration and deflection measurement system and method

Abstract

To provide a bridge vibration / deflection measuring system capable of efficiently storing a required line image.SOLUTION: A system for measuring vibration and deflection of a bridge by irradiating a lower surface of the bridge with laser line light and capturing a line image, which is reflected light of the laser line light, by an imaging device includes a ring buffer 20 capable of temporarily storing a predetermined amount of line images, a deflection detection unit that detects whether or not deflection of the bridge exceeds a predetermined value in real time from the line images, and a stop command unit that stops storing the line images in the ring buffer 20 and transmits the line images in the ring buffer to a storage device 21 when it is detected that the deflection exceeds the predetermined value.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a system and method for measuring the vibration and deflection of a bridge using the optical cutting method. [Background technology]

[0002] Deflection and vibration measurements of large infrastructure structures, such as bridges, are used to inspect structures for deterioration and defects. Measuring the overall deflection (displacement) of a bridge is important to ensure the structural integrity of the bridge. Therefore, in order to efficiently measure deflection, Patent Document 1 below discloses a method for performing non-contact deflection measurement without attaching a deflection measurement sensor to the bridge. Patent Document 1 also discloses a method for diffracting slit light reflected from the surface of the measurement object using an optical element that generates a diffraction phenomenon to generate multiple parallel linear diffracted light beams, capturing images of the multiple parallel linear diffracted light beams generated by the optical element, and performing phase analysis on the captured multiple parallel linear diffracted light beams.

[0003] This measurement method is explained using Figures 1 and 2. This is called the light-section method, and as shown in the principle diagram of Figure 1, by irradiating the measurement target with a laser line light (slit light) and photographing it with a camera from a direction different from the direction of irradiation, the photographed line image can be imported into a computer and deflection can be measured.

[0004] Figure 2 is a schematic diagram showing the measurement method for measuring bridge deflection. As shown in Figure 2, a laser line beam is projected onto the underside of the bridge between two girders, and an image of the line is captured by a camera. When deflection occurs on the underside, a change occurs in the line image in accordance with the deflection, and by analyzing this, deflection and vibration can be measured. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7045116 Summary of the Invention [Problem to be solved by the invention]

[0006] When line images are captured by an imaging device such as a camera and stored in a computer, the data is stored, but capturing and saving all line images is not practical due to issues such as storage capacity. The large deflections and vibrations required for analysis occur when heavy vehicles such as trucks pass by, so it is necessary to save line images only in such cases. To achieve this, workers on site monitored the movement of line images on monitors and for impact sounds, and saved line images only when large deflections occurred.

[0007] However, having workers constantly monitor the monitors at the site places a heavy burden on the workers and is problematic in terms of personnel costs.

[0008] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a bridge vibration and deflection measurement system that can efficiently store required line images. [Means for solving the problem]

[0009] In order to solve the above problems, the bridge vibration and deflection measurement system according to the present invention comprises: This system irradiates a laser line light onto the underside of a bridge, captures the line image of the reflected light with an imaging device, and measures the vibration and deflection of the bridge. a ring buffer capable of temporarily storing a predetermined amount of line images; a deflection detection unit that detects in real time from the line image whether the deflection of the bridge exceeds a predetermined value; It is characterized by having a stop command unit that, when it is detected that the deflection exceeds a predetermined value, stops storing the line image in the ring buffer and transmits the line image in the ring buffer to a storage device.

[0010] The operation and effect of the bridge vibration and deflection measurement system with this configuration will be explained below. With this configuration, the captured line image is temporarily stored in a ring buffer. The ring buffer is a memory in which old data is deleted as new data is received and is constantly overwritten with the latest data. On the other hand, it is equipped with a deflection detection unit that detects in real time from the captured line image whether or not the bridge deflection has exceeded a predetermined value. This function can be realized by a computer.

[0011] When it is detected that the deflection has exceeded a predetermined value, the system stops storing line images in the ring buffer and sends the line image data in the ring buffer to the storage device for storage. In other words, line images for analysis are stored only when the deflection has exceeded a predetermined value, so the storage device's capacity can be used without unnecessarily straining. In addition, since deflection detection is performed automatically by the deflection detection unit, there is no need for workers to constantly monitor on-site. As a result, it has been possible to provide a bridge vibration and deflection measurement system that can efficiently store the required line images.

[0012] In the present invention, it is preferable that line images stored within a predetermined time before and after the time point when the command to stop storing is issued be transmitted to the storage device.

[0013] By setting a predetermined time, it is possible to acquire the amount of line image data required for analysis.

[0014] It is preferable that the deflection detection unit according to the present invention uses a template image created based on the line image at the start of measurement, and detects whether the deflection has exceeded a predetermined value by comparing this template image with the line image captured in real time.

[0015] By creating such a template image in advance, it is possible to automatically compare the template image with the line image captured in real time, thereby ensuring reliable detection of deflection.

[0016] In the present invention, a vibration analysis unit that performs vibration analysis from the line image stored in the storage device; a monitor control unit that displays the analyzed results in a graph on a monitor screen; The graph to be displayed preferably has the horizontal axis representing the position of the bridge in the bridge axis direction and the vertical axis representing the frequency of vibration, with the intensity of vibration on the vertical axis being displayed in a manner that can be distinguished by color.

[0017] It is necessary to perform vibration analysis from the saved line image and display the analysis results in an easy-to-understand graph on the monitor screen. The horizontal axis of the graph is the bridge axis direction, i.e., the direction along the line of the line image, which means the position in the bridge axis direction. The vertical axis is frequency, and the necessary information is the frequency and the strength of the vibration. In this invention, by expressing the strength with color, the vibration state can be seen at a glance on a single graph.

[0018] In order to solve the above problems, the bridge vibration and deflection measurement method according to the present invention comprises: A step of irradiating a laser line light onto an underside of a bridge; and a step of capturing a line image of the reflected light by an imaging device and measuring vibration and deflection of the bridge, Temporarily storing a predetermined amount of line images in a ring buffer; detecting in real time from the line image whether the deflection of the bridge exceeds a predetermined value; When it is detected that the deflection exceeds a predetermined value, the method further comprises a step of stopping the storage of the line image in the ring buffer and transmitting the line image in the ring buffer to a storage device.

[0019] The functions and effects of this configuration are as already described. [Brief explanation of the drawings]

[0020] [Figure 1] Diagram explaining the principle of the light-section method [Figure 2] Schematic diagram of measuring bridge deflection using the optical cutting method [Figure 3] Schematic diagram showing the main components of the system [Figure 4] Block diagram showing the main parts of the control system configured within the computer [Figure 5] Diagram explaining the function of a cylindrical lens [Figure 6] Graph showing vibration data measured by a system according to the present invention. [Figure 7] Diagram explaining the parameters required for optical cutting [Figure 8] Diagram explaining the principle of light-section calibration [Figure 9] Diagram explaining the principle of light-section calibration [Figure 10] FIG. 10 is a diagram showing a state when a line image is stored in a storage device. [Figure 11] A diagram explaining the template image for deflection detection [Figure 12] Monitor screen showing the results of vibration analysis [Figure 13] Enlarged view of a portion of the monitor screen showing the results of vibration analysis DETAILED DESCRIPTION OF THE INVENTION

[0021] A preferred embodiment of the bridge vibration and deflection measurement system according to the present invention will be described first. In the present invention, the bridge vibration and deflection measurement uses the light cutting method, the principles of which have already been explained in Figs. 1 and 2.

[0022] FIG. 3 is a schematic diagram showing the main configuration of the system of the present invention, and FIG. 4 is a block diagram showing the main parts of a control system configured within a computer.

[0023] 3, the camera 1 includes an image sensor 10, a photographing lens 11, a diffraction grating 12, and a cylindrical lens 13. Image data such as a line image captured by the camera 1 is sent to a computer 2 such as a personal computer. The line image captured by the computer 2 is branched into two systems for processing.

[0024] The ring buffer 20 is a memory capable of processing image data at high speed and temporarily stores line images. The storage capacity of the ring buffer 20 can be set as appropriate, but in this embodiment it is set to be able to store 20 seconds' worth of line images. The ring buffer 20 is constantly updated with new line image data, with the oldest data being deleted each time the latest line image data is input.

[0025] Meanwhile, the line images captured by computer 2 are constantly monitored by computer 2 to detect deflection. The mechanism for automatically detecting the magnitude of deflection will be described later. When it is detected that the magnitude of deflection is equal to or greater than a predetermined value, the storage of the line images in ring buffer 20 is stopped, and the line images in ring buffer 20 are sent to and stored in storage device 21. Storage device 21 is a large-capacity storage device such as an SSD or HDD. Deflection and vibration analysis is performed using the line images stored there.

[0026] The data processing time of the ring buffer 20 is faster than that of the storage device 21, so it has the capacity to process a large amount of images, 150 frames per second, as will be described later. The data processing time of the storage device 21 is slower by comparison, but this is after the storage of line images has been stopped, so the slow processing time does not have any impact.

[0027] In FIG. 4, the computer 2 is equipped with a control unit 3. The control unit 3 shows its main functions. The control unit 3 is composed of software and the like according to the functions. The image monitoring unit 30 constantly monitors the magnitude of deflection from the line image. The template storage unit 31 stores template images used to detect the magnitude of deflection. The threshold setting unit 32 presets a threshold value for determining whether or not to save the line image. The deflection detection unit 33 detects whether or not the detected deflection exceeds the threshold value.

[0028] When the deflection detection unit 33 detects a deflection equal to or greater than a predetermined value, the stop command unit 34 stops storing the line images in the ring buffer 20 and transmits the line images in the ring buffer 20 to the storage device 21. At that time, the stop command unit 34 also has a function of stopping storing the line images in the ring buffer 20 after a predetermined time delay. The vibration analysis unit 35 performs a vibration analysis of the bridge based on the line images stored in the storage device 21. The monitor control unit 36 ​​causes the display monitor 22 to display the analysis results, etc.

[0029] Figure 5 is a diagram explaining the function of the cylindrical lens 13 attached to the camera 1. The cylindrical lens 13 is a lens with a curved surface that is line-symmetrical with respect to a certain axis. Its attachment direction is shown in (a) as a vertical direction and in (b) as a horizontal direction (the bridge axis direction). In (a), the field of view of the photographing lens remains unchanged regardless of the presence of the cylindrical lens, but in (b), the field of view changes to expand.

[0030] A laser line of light is projected onto the underside of the bridge between girders (one span), and a cylindrical lens is used so that the projection is as long as possible in the direction of the bridge axis. What is required for vibration measurement is the movement (deflection) of the line image in the vertical direction. Therefore, accuracy is ensured in the vertical direction by using the settings shown in (a), and as accuracy (resolution) is not required in the direction of the bridge axis, a cylindrical lens is used to widen the field of view. Furthermore, while using a cylindrical lens will cause the image to become out of focus in the direction of the bridge axis, it will not cause the line image in the vertical direction to become out of focus. Note that optical elements with the same functions as a cylindrical lens can also be used.

[0031] When the vibrations caused by a vehicle passing over a bridge are viewed in a line image, the line image moves vertically, but the amount of movement is minute. This requires high resolution in the vertical direction. On the other hand, it is unlikely that the vibration behavior of the bridge will change significantly in units of 1 mm in the horizontal direction. In other words, the required resolution in the horizontal and vertical directions is more than 10 times higher.

[0032] In the case of a normal camera that does not use a cylindrical lens, the size of each pixel on the image sensor is the same in both the vertical and horizontal directions. Therefore, when trying to meet the required vertical resolution, the horizontal field of view becomes narrow. This means that multiple devices (cameras, irradiation devices, etc.) must be prepared to measure the vibration of one span (between bridge girders), which makes the work more time-consuming. The more cameras are used, the larger the amount of image data becomes, making the work more complicated.

[0033] Therefore, a camera using a cylindrical lens as described above is prepared. This allows data for one span to be acquired with a single camera setting. As a result, measurement accuracy can be maintained while also contributing to shortening work time.

[0034] FIG. 6 is a graph showing vibration data measured by the system according to the present invention. The horizontal axis represents time, 20 seconds. The vertical axis represents the magnitude of deflection. The threshold value for deflection is set to 2 mm, and data is displayed for 10 seconds before and after the point at which the deflection exceeds 2 mm. This graph shows the change in deflection over time at a certain point in the bridge axis direction (for example, the center position in the line direction of the line image). In this embodiment, a total of 20 seconds of line images are stored in the storage device 21, but this setting can be changed as appropriate.

[0035] In Figure 6, the arrow in the graph indicates the point at which the threshold was exceeded. Data is displayed for 10 seconds before and after that point.

[0036] In this embodiment, the camera 1 captures 150 frames of line images per second, so when measuring vibration, 20 seconds x 150 = 3000 frames of line images are captured and vibration analysis is performed. The movement of a certain point on the line image can be analyzed from 3000 frames of data to perform frequency analysis.

[0037] A typical camera captures 30 or 60 frames of images per second, but for vibration analysis, this number of frames is insufficient, so 150 frames of images are captured. In this respect, too, the amount of image data to be captured by the computer increases, so it is necessary to record line images efficiently so as not to strain the storage capacity of the storage device 21.

[0038] Figure 7 is a diagram explaining the parameters required for optical sectioning. In optical sectioning, a laser line light is projected onto the underside of the bridge, and camera 1 is installed at a position away from the light. In other words, a line image is captured from an oblique direction. The deflection and vibration of the bridge are measured from this line image. However, although the laser line light is projected perpendicularly onto the underside of the bridge, it may not be possible to adjust it this way depending on the situation at the site. The same applies to the placement of camera 1.

[0039] In order to accurately measure the magnitude of deflection from the captured line image, the positioning and installation angle (lens direction) of the laser line light projection device and camera 1 are involved, so data on their positional relationship is required and must be entered into a computer, which is cumbersome. Therefore, efficient calibration is required.

[0040] 8 and 9 are diagrams explaining the principle of calibration. FIG. 8 shows the state in which the camera 1 and the illumination device are placed on the underside of a bridge. The bridge axis is perpendicular to the paper. FIG. 9 shows a captured line image. Consider the case in which the underside of the bridge is lowered a predetermined distance (for example, 10 mm) in this state. In this case, the line image does not necessarily move down 10 mm in a parallel manner.

[0041] This is because the center of the line image is close to the camera, but the left and right sides are far away, and there are also differences in the camera's posture, the posture of the lighting equipment, and subtle irregularities in the underside of the bridge. Therefore, by calibrating using a 10 mm movement of the underside of the bridge, the vertical displacement amount at a specific position in the bridge axis direction can be found through proportional calculation. In other words, by storing in advance the displacement (number of pixels) on the line image in two different situations along with the height of the underside of the bridge, it is possible to calculate the actual accurate vertical displacement amount (deflection).

[0042] In reality, it is not possible to move the underside of the bridge, so it is sufficient to move the camera and illumination device by 10 mm. For example, by installing the camera and illumination device on a common base and moving the base vertically, it is possible to create a state equivalent to moving the underside of the bridge vertically.

[0043] Fig. 10 is a conceptual diagram showing a state when a line image is stored in the storage device 21. Fig. 11 is a diagram for explaining a template image for detecting deflection.

[0044] Figure 11 shows the monitor screen. There is a start button 40 on the screen; pressing this starts measurement. An area 41 is provided for setting the threshold value, and the threshold value is input. If the threshold value for deflection detection is set to 2 mm, a corresponding value is input. The recording time can be set in area 42 based on the storage capacity of the ring buffer; in this embodiment, this is set to 20 seconds.

[0045] There is provided an area 43 for setting a template for detecting deflection, where the coordinates, width and height of the template can be set.

[0046] The captured line image is displayed on the monitor screen. A line L is displayed horizontally, and the installed template image T is shown in a rectangular frame. A portion of the line image is included in this rectangular frame as a horizontal line. The coordinates (coordinates of the upper left corner of the rectangular area) and size of the set template image are fixed. This template image is saved in the template storage unit 31.

[0047] This template image is compared (matching process) with the line image that is captured in real time. The line image captured in real time moves up and down depending on the situation. The amount of this movement (number of pixels) is measured in real time. When this amount of movement exceeds a set threshold, the storage of the line image in the ring buffer is stopped after a predetermined time has elapsed from that point. At that time, it also has a function to stop the storage of the line image in the ring buffer 20 after a predetermined time delay.

[0048] As conceptually shown in Figure 10, storage is stopped 10 seconds after the point in time when the movement amount exceeds the threshold, which is half the specified recording time (20 seconds in this embodiment). In other words, line images for 10 seconds before and after the point in time when the threshold is exceeded are stored in the ring buffer, and these 20 seconds of line images are sent to a storage device and saved. After being sent to the storage device, the image data in the ring buffer is discarded. Vibration analysis is performed using these 20 seconds of line images stored in the storage device.

[0049] Figure 12 is a monitor screen showing the results of vibration analysis. Area 100 is an area where a line image is displayed, with horizontal lines displayed. Area 101 is an area where the vibration analysis results are displayed, and Figure 13 is an enlarged view of this area. Area 102 is an area for setting parameters when displaying the analysis results. Area 103 is a graph showing the vibration state at a specific position in the bridge axis direction, and is the same type as that shown in Figure 6.

[0050] This graph shows the analysis results at the position indicated by P in areas 100 and 101, and by shifting the position of P left or right with a mouse or other device, it is possible to display a graph of the analysis results at a different position (the relationship between frequency (horizontal axis) and its component value (vertical axis)). Note that the component value is calculated so that it becomes 1 when integrated over all frequencies.

[0051] In Figure 13, the horizontal axis represents the position in the bridge axis direction, and the vertical axis represents the frequency of vibration, with the strength of vibration on the vertical axis being identified by color. For convenience, the figure is displayed in monochrome (shade), but in reality it is displayed in color. The relationship between strength and color can be set as desired; for example, the greater the strength (component value) of the vibration, the brighter the color. By displaying the graph in this way, it is easy to check the position, frequency, and strength on the same graph.

[0052] While a normal graph displays a two-dimensional graph showing the relationship between position and intensity, and the relationship between frequency and the intensity of that component, the present invention can display the three-dimensional elements of position, frequency, and intensity on a single two-dimensional graph.Frequency analysis can be displayed in a list on the horizontal axis, allowing for more advanced information to be obtained.

[0053] <Another embodiment> The laser light to be irradiated onto the underside of the bridge can be of an appropriate color, such as green or red, which provides good contrast depending on the condition of the underside. The same goes for the intensity (brightness) of the laser light.

[0054] The timing for restarting storage in the ring buffer after stopping storage in the ring buffer and saving the line image in the storage device can be determined as appropriate. For example, storage may be restarted automatically after a predetermined time has elapsed, or may be started manually by an operator. [Explanation of symbols]

[0055] 1 camera 13 Cylindrical Lens 2. Computer 20 Ring Buffer 21 Storage device 30 Image Monitoring Department 31 Template memory section 32 Threshold setting section 33 Deflection detection unit 34 Stop Command 35 Vibration Analysis Department 36 Monitor control section

Claims

1. This system irradiates a laser line light onto the underside of a bridge, captures the line image of the reflected light with an imaging device, and measures the vibration and deflection of the bridge. a ring buffer capable of temporarily storing a predetermined amount of line images; a deflection detection unit that detects in real time from the line image whether the deflection of the bridge exceeds a predetermined value; A bridge vibration and deflection measurement system characterized by comprising a stop command unit that, when it is detected that the deflection exceeds a predetermined value, stops storing line images in the ring buffer and transmits the line images in the ring buffer to a memory device.

2. The bridge vibration and deflection measurement system according to claim 1, characterized in that line images stored within a predetermined time before and after the time when the command to stop storage is issued are transmitted to the storage device.

3. The bridge vibration and deflection measurement system described in claim 1 or 2, characterized in that the deflection detection unit uses a template image created based on the line image at the start of measurement, and detects whether the deflection has exceeded a predetermined value by comparing this template image with the line image captured in real time.

4. a vibration analysis unit that performs vibration analysis based on the line image stored in the storage device; a monitor control unit that displays the analyzed results in a graph on a monitor screen; The bridge vibration and deflection measurement system according to claim 1 or 2, characterized in that the graph displayed has the horizontal axis representing the position of the bridge in the bridge axis direction and the vertical axis representing the frequency of vibration, and the vertical axis is displayed so that the strength of vibration can be identified by color.

5. A step of irradiating a laser line light onto an underside of a bridge; and a step of capturing a line image of the reflected light by an imaging device and measuring vibration and deflection of the bridge, Temporarily storing a predetermined amount of line images in a ring buffer; detecting in real time from the line image whether the deflection of the bridge exceeds a predetermined value; A method for measuring vibration and deflection of a bridge, characterized by comprising the steps of: when it is detected that the deflection exceeds a predetermined value, stopping the storage of line images in the ring buffer and transmitting the line images in the ring buffer to a storage device.

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