Pier displacement measurement system and method based on remote video monitoring

Abstract

The invention discloses a bridge pier displacement measurement system based on remote video monitoring. The bridge pier displacement measurement system comprises an automatic focusing pan-tilt camera and a target arranged on a bridge pier. The automatic focusing pan-tilt camera comprises an embedded mainboard, an industrial camera, an electric focusing lens, an electric pan-tilt and an encoder. The embedded mainboard is connected with the industrial camera through a network, the embedded mainboard is connected with the electric focusing lens and the electric cradle head through RS485 interfaces, and the electric cradle head is connected with the encoder; the rotation angle of the target relative to the reference position is measured by means of the electric holder, and the space coordinate of the target can be calculated, so that the displacement of the target in the horizontal direction, the vertical direction and the front-back direction is calculated, the measurement of the space displacement of the target is realized, and the measurement of sinking, displacement and inclination of the pier can be realized. The technical problem that in the prior art, a total station and a measuring robot are limited in use is solved.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering monitoring and measurement, and relates to displacement measurement methods, specifically a bridge pier displacement measurement system and method based on remote video monitoring. Background Technology

[0002] In the field of civil engineering, monitoring and measuring construction tunnels and pile foundations in accordance with construction specifications, and promptly detecting abnormalities such as arch subsidence, clearance convergence, and settlement, are important means to ensure construction quality and safety.

[0003] Currently, the main methods for monitoring and measurement are to measure the displacement of various targets using total stations and surveying robots (fully automatic total stations). Manual measurement with a total station is complex, has a limited measurement frequency, and cannot achieve long-term continuous measurement. Surveying robots can achieve automated measurement, but they are expensive and cannot be used on a large scale. For monitoring and measurement that does not require target point coordinate information but only needs to monitor the displacement of the target point, using a total station is not a suitable method.

[0004] Traditional video surveillance measurement systems use fixed-focus lenses, limiting monitoring to specific bridge pier observation points. Beyond this distance, the camera's focal length limitation prevents clear imaging, rendering the system unusable. The clarity of the target image restricts the accuracy of target position measurement. Traditional autofocus methods rely on detecting the sharpness of image edges, which is limited by the complexity of the object's outline, making it difficult to achieve ideal clarity. Video surveillance measurement systems using planar cameras can only acquire the target's horizontal and vertical displacement; therefore, they can only measure bridge pier settlement and displacement.

[0005] Based on the above situation, there is an urgent need for a bridge pier displacement measurement system and method based on remote video monitoring to solve the above-mentioned technical defects. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a bridge pier displacement measurement system and method based on remote video monitoring, so as to solve the technical problem of limited use of total station and measurement robot in the existing technology.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A bridge pier displacement measurement system based on remote video monitoring includes an autofocus pan-tilt camera and a target set on the bridge pier; the autofocus pan-tilt camera includes an embedded motherboard, an industrial camera, an electric focusing lens, an electric pan-tilt head, and an encoder; the embedded motherboard is connected to the industrial camera via a network, and the embedded motherboard is connected to the electric focusing lens and the electric pan-tilt head via an RS485 interface; the encoder is connected to the electric pan-tilt head. The target pattern consists of a circle at the center of the target and four focusing circles at the four corners of the target, with the sides of the rectangle formed by the four focusing circles being equal.

[0009] The distance between the autofocus gimbal camera and the target is less than 100m.

[0010] A method for measuring bridge pier displacement based on remote video monitoring, using the aforementioned bridge pier displacement measurement system based on remote video monitoring, specifically includes the following steps: S1. Establish an image coordinate system with the center of the camera image as the origin, the horizontal direction as the x-axis, and the vertical direction as the y-axis; adjust the focal length f of the industrial camera to obtain a clear image of the target pattern; adjust the motorized pan-tilt head to make the center of the target in the industrial camera coincide with the center of the camera image, and position the target center in the image coordinate system. As a reference position; S2, Based on the image coordinate system, establish a camera coordinate system with the line connecting the industrial camera and the target as the z-axis, and obtain the target coordinates in the camera coordinate system as follows: The distance from the target to the industrial camera is calculated according to formula (1). That is, the coordinates of the target are obtained as ; (1) in: f is the camera focal length, in mm; H is the diameter of the target, in mm; h represents the imaging height of the target in the industrial camera, in mm; S3: The industrial camera acquires real-time images of the target's current position and detects the target's center position in the image coordinate system. The distance from the current target to the industrial camera is calculated. That is, to obtain the current target's coordinates in the camera coordinate system. ; (2) in: f is the camera focal length, in mm; H is the diameter of the target, in mm; h represents the imaging height of the target in the industrial camera, in mm; S4, Determine position relative to the reference position Check if the piers overlap. If so, the bridge piers have not shifted. If not, adjust the motorized pan-tilt head to align with the reference position in the industrial camera. Move to location The encoder is used to obtain the rotation angle of the motorized pan-tilt head on the x-axis. and rotation angle on the y-axis ; S5, calculate the position according to the following formula. and The coordinate difference is , and This means obtaining the displacement of the target, which in turn means obtaining the displacement of the bridge pier.

[0011]

[0012] .

[0013] In S1, adjusting the focal length f of the industrial camera to obtain a clear image of the target pattern specifically involves: s1, Detect the distance between the centers of the four focusing circles , , and The standard deviation is calculated as follows. ;

[0014] s2, calculate the ratio of the standard deviation to the mean using the following formula. Determine the ratio If the value is less than 0.01, it indicates that the camera image is clear; otherwise, the camera image is not clear.

[0015] .

[0016] Compared with the prior art, the beneficial technical effects of this invention are: (I) This invention uses an electric gimbal to measure the rotation angle of the target relative to the reference position, and can calculate the spatial coordinates of the target, thereby calculating the displacement of the target in the horizontal, vertical and forward and backward directions, realizing the measurement of the target's spatial displacement, and can realize the measurement of bridge pier sinking, displacement and tilting, solving the technical problem of limited use of total station and measuring robot in the prior art.

[0017] (II) A special target pattern is used. The focus is accurately determined by whether the center distance of the focus circles of the target pattern is equal. This can achieve clear imaging of the target pattern and ensure the accuracy of displacement measurement of the bridge pier observation point.

[0018] (III) Compared with the traditional total station measurement method, the present invention achieves full automation and continuity of the measurement process by using an autofocus gimbal camera. It can perform unattended, real-time synchronous monitoring of multiple targets through video measurement, completely eliminating the limitations of manual aiming and discrete sampling. It enriches the information dimension and intuitiveness of the measurement, and provides corresponding visual image evidence while outputting accurate quantitative data. It supports quantitative analysis and scenario-based diagnosis of bridge pier displacement. In the fields of bridge pier health monitoring and construction safety, it provides a new solution for building a low-cost, high-efficiency, and visualized wide-area intelligent monitoring network, and solves the technical problem of limited use of total stations and measurement robots in the prior art.

[0019] (IV) The use of an autofocus gimbal camera can measure the displacement of the target within a 100-meter range, thus allowing for the measurement of bridge piers within a 100-meter range. Attached Figure Description

[0020] Figure 1 This is a structural block diagram of the autofocus gimbal camera in this invention; Figure 2 This is a schematic diagram of the autofocus gimbal camera and the target arrangement on the bridge pier in this invention. Figure 3 This refers to the target pattern in this invention; Figure 4 This is a schematic diagram of the camera spatial coordinate system in this invention; Figure 5 This is a schematic diagram of the camera imaging principle in this invention; Figure 6 This is a schematic diagram of the camera planar coordinate system in this invention. The labels in the diagram mean: 1-target; 2-bridge pier; 3-autofocus gimbal camera.

[0021] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0022] It should be noted that, unless otherwise specified, all components in this invention are those known in the art.

[0023] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0024] This invention provides a bridge pier displacement measurement system based on remote video monitoring, including an autofocus pan-tilt camera and a target set on the bridge pier; the autofocus pan-tilt camera includes an embedded motherboard, an industrial camera, an electric focusing lens, an electric pan-tilt head, and an encoder; the embedded motherboard is connected to the industrial camera via a network, and the embedded motherboard is connected to the electric focusing lens and the electric pan-tilt head via an RS485 interface, and the encoder is connected to the electric pan-tilt head. The target pattern consists of a circle at the center of the target and four focusing circles at the four corners of the target, with the sides of the rectangle formed by the four focusing circles being equal.

[0025] In the above technical solution, by using an electric gimbal to measure the rotation angle of the target relative to the reference position, the spatial coordinates of the target can be calculated, thereby calculating the displacement of the target in the horizontal, vertical, and forward / backward directions, realizing the measurement of the target's spatial displacement, and enabling the measurement of bridge pier settlement, displacement, and tilt, thus solving the technical problem of the limited measurement range of total stations and measuring robots in the existing technology.

[0026] See Figure 1 The connection relationships between various components in a bridge pier displacement measurement system based on remote video monitoring are presented. The embedded motherboard is used for target image storage and target spatial coordinate calculation; the industrial camera is used for target image acquisition; the motorized zoom lens can be controlled by software to zoom and focus, enabling remote shooting of the target; and the motorized pan-tilt head is used to adjust the horizontal and vertical shooting angle of the camera.

[0027] See Figure 2 An autofocus gimbal camera is fixed near the bridge pier, and the target is fixed on the bridge pier to ensure that the target can be observed by the video system.

[0028] See Figure 3 The pattern of the target in this scheme is given.

[0029] When an autofocus gimbal camera photographs a target, with the camera position remaining constant, the size of the target image is inversely proportional to the shooting distance; that is, the farther the distance, the smaller the target image. If the focal length of the autofocus gimbal camera and the target image size are known, the distance between the target and the camera can be calculated from the target image size.

[0030] The distance between the autofocus gimbal camera and the target is less than 100m.

[0031] In the above technical solution, the maximum working distance of the autofocus gimbal camera is 100m, and the distance between the gimbal camera and the target is limited to less than 100m.

[0032] Furthermore, a method for measuring bridge pier displacement based on remote video monitoring is presented. This method, based on a bridge pier displacement measurement system using remote video monitoring, specifically includes the following steps: S1. Establish an image coordinate system with the center of the camera image as the origin, the horizontal direction as the x-axis, and the vertical direction as the y-axis; adjust the focal length f of the industrial camera to obtain a clear image of the target pattern; adjust the motorized pan-tilt head to make the center of the target in the industrial camera coincide with the center of the camera image, and position the target center in the image coordinate system. As a reference position; S2, Based on the image coordinate system, establish a camera coordinate system with the line connecting the industrial camera and the target as the z-axis, and obtain the target coordinates in the camera coordinate system as follows: The distance from the target to the industrial camera is calculated according to formula (1). That is, the coordinates of the target are obtained. ; (1) in: f is the camera focal length, in mm; H is the diameter of the target, in mm; h represents the imaging height of the target in the industrial camera, in mm; S3: The industrial camera acquires real-time images of the target's current position and detects the target's center position in the image coordinate system. The distance from the current target to the industrial camera is calculated. That is, to obtain the current target's coordinates in the camera coordinate system. ; (2) in: f is the camera focal length, in mm; H is the diameter of the target, in mm; h represents the imaging height of the target in the industrial camera, in mm; S4, Determine position relative to the reference position Check if the piers overlap. If so, the piers have not shifted. If not, adjust the motorized pan-tilt head to align with the reference position in the industrial camera. Move to location The encoder is used to obtain the rotation angle of the motorized pan-tilt head on the x-axis. and rotation angle on the y-axis ; S5, calculate the position according to the following formula. and The coordinate difference is , and This means obtaining the displacement of the target, which in turn means obtaining the displacement of the bridge pier.

[0033]

[0034] .

[0035] In the above technical solution, the camera can achieve clear imaging within a certain object distance range by adjusting the focus; the motorized gimbal has two degrees of freedom, x (horizontal) and y (vertical), and the encoder can obtain the relative angle value of the gimbal rotation respectively.

[0036] Using the origin of the image coordinate system as the origin, a camera coordinate system is established according to the right-hand rule, defining the direction of the line connecting the target center and the camera center as the z-axis. For a given target, the pan-tilt angle is adjusted so that the target center is located at the center of the camera frame. At this point, the angle between the target center and the x-axis (horizontal direction) and y-axis (vertical direction) is 0. With the camera position fixed, when the bridge pier shifts (i.e., the target position moves), the target center's position in the camera frame shifts. The pan-tilt is moved to bring the target center back to the center of the camera frame, and the horizontal and vertical angular movements of the pan-tilt are recorded during this process. Given the distance between the target and the camera, the target's rotation angle relative to its initial position, and the target's initial position, the target's current spatial coordinates can be calculated. Knowing the target's spatial coordinates allows for the calculation of the target's displacement relative to its initial position, enabling the monitoring and measurement of the target's position.

[0037] In S1, adjusting the focal length f of the industrial camera to obtain a clear image of the target pattern specifically involves: s1, Detect the distance between the centers of the four focusing circles , , and The standard deviation is calculated as follows. ;

[0038] s2, calculate the ratio of the standard deviation to the mean using the following formula. Determine the ratio If the value is less than 0.01, it indicates that the camera image is clear; otherwise, the camera image is not clear.

[0039] .

[0040]

[0041] .

[0042] In the above technical solution, a special target pattern is used. The focus is accurately determined by whether the center distance of the focusing circles of the target pattern is equal, which can achieve clear imaging of the target pattern and ensure the accuracy of displacement measurement of the bridge pier observation point.

Claims

1. A bridge pier displacement measurement system based on remote video monitoring, comprising an autofocus pan-tilt camera and a target mounted on the bridge pier; characterized in that, The autofocus gimbal camera includes an embedded motherboard, an industrial camera, a motorized focusing lens, a motorized gimbal, and an encoder; the embedded motherboard is connected to the industrial camera via a network, and the embedded motherboard is connected to the motorized focusing lens and the motorized gimbal via an RS485 interface; the encoder is connected to the motorized gimbal. The target pattern consists of a circle at the center of the target and four focusing circles at the four corners of the target, with the sides of the rectangle formed by the four focusing circles being equal.

2. The bridge pier displacement measurement system based on remote video monitoring as described in claim 1, characterized in that, The distance between the autofocus gimbal camera and the target is less than 100m.

3. A method for measuring bridge pier displacement based on remote video monitoring, based on the bridge pier displacement measurement system based on remote video monitoring as described in claim 1 or 2, characterized in that, Specifically, the following steps are included: S1. Establish an image coordinate system with the center of the camera image as the origin, the horizontal direction as the x-axis, and the vertical direction as the y-axis; adjust the focal length f of the industrial camera to obtain a clear image of the target pattern; adjust the motorized pan-tilt head to make the center of the target in the industrial camera coincide with the center of the camera image, and position the target center in the image coordinate system. As a reference position; S2, Based on the image coordinate system, establish a camera coordinate system with the line connecting the industrial camera and the target as the z-axis, and obtain the target coordinates in the camera coordinate system as follows: The distance from the target to the industrial camera is calculated according to formula (1). That is, the coordinates of the target are obtained as ; （1） in: f is the camera focal length, in mm; H is the diameter of the target, in mm; h represents the imaging height of the target in the industrial camera, in mm; S3: The industrial camera acquires real-time images of the target's current position and detects the target's center position in the image coordinate system. The distance from the current target to the industrial camera is calculated. That is, to obtain the current target's coordinates in the camera coordinate system. ; （2） in: f is the camera focal length, in mm; H is the diameter of the target, in mm; h represents the imaging height of the target in the industrial camera, in mm; S4, Determine position relative to the reference position Check if the piers overlap. If so, the bridge piers have not shifted. If not, adjust the motorized pan-tilt head to align with the reference position in the industrial camera. Move to location The encoder is used to obtain the rotation angle of the motorized pan-tilt head on the x-axis. and rotation angle on the y-axis ; S5, calculate the position according to the following formula. and The coordinate difference is , and This means obtaining the displacement of the target, which in turn means obtaining the displacement of the bridge pier. 。 4. The method for measuring bridge pier displacement based on remote video monitoring as described in claim 3, characterized in that, In S1, adjusting the focal length f of the industrial camera to obtain a clear image of the target pattern specifically involves: s1, Detect the distance between the centers of the four focusing circles , , and The standard deviation is calculated as follows. ; s2, calculate the ratio of the standard deviation to the mean using the following formula. Determine the ratio If the value is less than 0.01, it indicates that the camera image is clear; otherwise, the camera image is not clear. 。

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