Concrete dam strain gauge based on mems gyroscope

Abstract

This invention discloses a strain gauge for concrete dams based on a MEMS gyroscope, comprising a strain gauge body with at least X-axis, Y-axis, and Z-axis strain gauges, and further including: a MEMS gyroscope mounted on the upper part of the Z-axis strain gauge for detecting the tilt angle of the strain gauge body; a data acquisition unit for acquiring tilt angle data output by the MEMS gyroscope and strain data output by the strain gauge body; and a data processing unit communicatively connected to the data acquisition unit for receiving the tilt angle data and strain data. By mounting a MEMS gyroscope on the upper part of the Z-axis of the strain gauge body, this invention can accurately calculate the angle between the coordinate system axis of the strain gauge and the design coordinate system axis after embedding it in the dam, effectively correcting the deviation in strain gauge measurement, improving the accuracy and reliability of monitoring data, and overcoming the measurement error problem caused by incorrect embedding methods by construction personnel in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of concrete dam testing technology, and in particular to a concrete dam strain gauge based on a MEMS gyroscope. Background Technology

[0002] To ensure the safe operation of concrete dams, many dams are equipped with numerous stress-strain monitoring instruments to monitor the dam structure's operational status at any time. However, improper installation methods by construction workers and construction interference often cause strain gauges to tilt during installation, resulting in unreliable data from the pentaaxial strain gauges and an inability to guarantee that the calculated stress-strain data reflects the dam's true stress condition. This deviation not only affects the accuracy of data analysis but may also lead to misjudgments of the dam's safety level, thereby impacting dam safety management.

[0003] CN117928643A discloses a method and apparatus for stress-strain analysis of dams based on multi-point combined calculation. This patent involves deploying a stress-strain monitoring system on the dam to collect stress-strain monitoring data; based on this data, determining stress-strain analysis parameters for the dam, including the vertical distribution of stress in the dam foundation, the overall horizontal stress of the dam body, the overall stress in the vertical beam direction, and a comparison of strain amplitude at key locations; and performing stress-strain analysis on the dam based on these parameters. CN117367646A discloses a concrete stress redundancy monitoring system and stress calculation method based on strain gauge sets and rebar gauges. This patent achieves multi-faceted complementary monitoring of concrete stress and strain by embedding strain gauges, stress gauges, and rebar gauges in the concrete structure, collecting data through a low-power data logger, and connecting it to a monitoring and management platform via signal lines.

[0004] However, the aforementioned patent's arrangement of strain gauges and stress-free gauges cannot address the issue of measuring the true strain components when the strain gauges are tilted during installation. This leads to discrepancies between the calculated vertical strain, river-direction strain, and dam axial strain and the actual situation. To solve these problems, there is an urgent need to develop a monitoring technology that can accurately reflect the true strain state inside the dam. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a strain gauge for concrete dams based on MEMS gyroscopes, which can accurately calculate the actual installation angle deviation caused by pouring deflection, and achieve complete decoupling and non-load deformation compensation of X, Y, and Z triaxial strain and shear strain at the three-dimensional strain tensor level, thereby outputting the true local mechanical strain of the dam to determine its safety status.

[0006] To achieve the above-mentioned technical features, the objective of this invention is as follows: In a first aspect, the present invention proposes a strain gauge for concrete dams based on a MEMS gyroscope, comprising a strain gauge body, wherein at least X-axis, Y-axis and Z-axis strain gauges are provided on the strain gauge body, and further comprising: The MEMS gyroscope is mounted on the top of the Z-axis strain gauge and is used to detect the tilt angle of the strain gauge body. The data acquisition unit is used to acquire tilt angle data output by the MEMS gyroscope and strain data output by the strain gauge body. The data processing unit, communicatively connected to the data acquisition unit, is used to receive tilt angle data and strain data, and perform the following steps: The actual installation angle of the strain gauge body in three-dimensional space is calculated based on the tilt angle data; A three-dimensional spatial rotation matrix is ​​constructed based on the actual installation angle. The original strain data output by the strain gauges on the X-axis, Y-axis and Z-axis are spatially decoupled and geometrically corrected to obtain the corrected strain data in the global coordinate system of the dam. Non-load strain elimination analysis is performed on the corrected strain data to obtain the true load strain of the dam, so as to determine the strain safety state of the dam.

[0007] The top of the Z-axis strain gauge is fixedly mounted on a mounting bracket, and the MEMS gyroscope is fixedly mounted on the mounting bracket.

[0008] The data acquisition unit includes a data acquisition module and a communication module. The tilt angle data acquired by the data acquisition module includes angular velocity data output by the MEMS gyroscope and acceleration data output by the built-in accelerometer of the MEMS gyroscope. The communication module uses a hydraulic cable to connect the data acquisition unit to an external data processing unit. The data processing unit also includes a data storage module for storing the acquired raw data and corrected strain data.

[0009] The steps of the data processing unit in calculating the actual installation angle based on the tilt angle data include: Based on the adaptive complementary filtering algorithm, the angular velocity data and acceleration data are fused through time iteration to eliminate dynamic vibration noise and zero-point drift, and the real-time pitch angle and real-time roll angle of the strain gauge body are calculated.

[0010] The steps of the data processing unit to correct the original strain data according to the actual installation angle include: Obtain the global coordinate system of the dam and the local measurement coordinate system of the strain gauge body; A three-dimensional spatial rotation matrix is ​​constructed using the actual installation angle to determine the projection direction cosines of the strain gauges on the X, Y, and Z axes in the global coordinate system. Based on the principle of three-dimensional principal strain projection, a set of directional projection equations consisting of three projection equations is established. A 3×3 dimension transformation decoupling matrix is ​​constructed through matrix processing, and the shear strain disturbance compensation term caused by spatial shear strain is extracted. The original strain data is input into the decoupled correction model composed of the transformation decoupling matrix and the shear strain disturbance compensation term. The true normal strain in the global coordinate system of the corresponding dam is obtained by matrix inversion operation, which is used as the corrected strain data.

[0011] The shear strain disturbance compensation term is calculated using an adaptive feedback approximation iterative method, and its initial value is determined based on the shear stress scaling factor of the pre-stored dam finite element model.

[0012] Before spatial decoupling and geometric correction, the original strain data is first calculated using temperature compensation to eliminate spurious strains caused by the difference in thermal shrinkage between the strain gauge material and the dam concrete.

[0013] The steps of the data processing unit to perform non-load strain elimination analysis on the corrected strain data include: subtracting the autogenous shrinkage strain, drying shrinkage strain, and creep cumulative strain of the dam concrete from the corrected strain data to obtain the true load strain of the dam.

[0014] The steps by which the data processing unit determines the strain safety status of the dam include: Calculate the ratio of the actual load strain to the tensile strength of the concrete at the current age, and construct a dam safety status assessment index based on the static elastic modulus. The dam safety status assessment index is compared with a preset safety threshold, and the corresponding normal, early warning or alarm status signal is output.

[0015] Compared with the prior art, the beneficial effects of the present invention include: 1. This invention, by installing a MEMS gyroscope on the upper part of the Z-axis of the strain gauge body, can accurately calculate the angle between the coordinate system axis of the strain gauge and the design coordinate system axis after it is embedded in the dam. This effectively corrects the deviation of the strain gauge measurement, improves the accuracy and reliability of the monitoring data, and overcomes the measurement error problem caused by incorrect installation methods by construction personnel in the prior art. By combining the MEMS gyroscope with the strain gauge, precise monitoring of the actual strain state inside the dam is achieved, comprehensively reflecting the overall operating status of the dam, avoiding misjudgment of safety due to measurement deviation, and improving the accuracy of dam safety management.

[0016] 2. This invention rigidly integrates a MEMS gyroscope with a concrete strain gauge. The correction algorithm used is based on three-dimensional tensor space projection, which can decouple the shear strain interference and normal strain penetration caused by the three-dimensional tilt of space online, thereby improving the strain monitoring accuracy in complex stress concentration areas, such as the dam toe and the area around the gallery. At the same time, in conjunction with the non-load deformation factor stripping algorithm, it can achieve accurate expression of the actual stress deformation mode of the dam. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the design principle of the present invention.

[0019] Figure 2 This is a logic block diagram of step one in embodiment 2 of the present invention.

[0020] Figure 3 This is a logic block diagram of step two in Embodiment 2 of the present invention.

[0021] Figure 4 This is a logic block diagram of step three in embodiment 2 of the present invention.

[0022] Figure 5 This is a logic block diagram of step four in Embodiment 2 of the present invention.

[0023] In the picture: 1. Z-axis strain gauge, 2. Strain gauge body, 3. Hydraulic cable, 4. MEMS gyroscope, 5. Fixed anchor bolt, 6. Mounting bracket. Detailed Implementation

[0024] To more clearly illustrate the purpose, technical solution, and beneficial effects of this application, a further detailed description of this application is provided below in conjunction with illustrations and specific embodiments. It should be specifically noted that the specific embodiments described below are only for illustrating the technical content of this application and do not constitute a limitation on the scope of protection of this application.

[0025] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0026] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection via an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] Example 1: like Figure 1 As shown, this embodiment provides a strain gauge for a concrete dam based on a MEMS gyroscope, including a strain gauge body 2, on which at least X-axis, Y-axis and Z-axis strain gauges 1 are provided, and further includes: MEMS gyroscope 4 is mounted on the upper part of Z-axis strain gauge 1 and is used to detect the tilt angle of strain gauge body 2. The data acquisition unit is used to acquire tilt angle data output by MEMS gyroscope 4 and strain data output by strain gauge body 2; The data processing unit, which is communicatively connected to the data acquisition unit, is used to receive tilt angle data and strain data, and to perform the following steps: The actual installation angle of the strain gauge body 2 in three-dimensional space was calculated based on the tilt angle data. A three-dimensional spatial rotation matrix is ​​constructed based on the actual installation angle. The original strain data output by strain gauge 1 on the X-axis, Y-axis and Z-axis are spatially decoupled and geometrically corrected to obtain the corrected strain data in the corresponding global coordinate system of the dam. Non-load strain elimination analysis is performed on the corrected strain data to obtain the true load strain of the dam, so as to determine the strain safety state of the dam.

[0028] The top of the Z-axis strain gauge 1 is fixedly equipped with a mounting bracket 6, and the MEMS gyroscope 4 is fixedly mounted on the mounting bracket 6.

[0029] A fixed anchor rod 5 is fixedly installed at the bottom of the strain gauge body 2. The fixed anchor rod 5 is used to embed and fix the strain gauge body into the dam.

[0030] The data acquisition unit includes a data acquisition module and a communication module. The tilt angle data acquired by the data acquisition module includes angular velocity data output by MEMS gyroscope 4 and acceleration data output by the built-in accelerometer of MEMS gyroscope 4. The communication module uses a hydraulic cable 3 to connect the data acquisition unit to the external data processing unit. The data processing unit also includes a data storage module for storing the acquired raw data and corrected strain data.

[0031] Example 2: Based on Example 1, this example also proposes an implementation method for strain gauges used in concrete dams. This method mainly involves a data processing unit performing calculations and analysis on the collected data. The specific steps are as follows: Step 1: Raw data acquisition and dynamic filtering fusion.

[0032] Due to various vibration interferences during the concrete pouring process and the operation of the dam, and the zero-point drift of the MEMS gyroscope 4 during long-term operation, this invention first obtains a high-precision tilt angle through a filtering algorithm.

[0033] The data acquisition unit acquires the angular velocity vector output by MEMS gyroscope 4. and the acceleration vector output by the built-in triaxial accelerometer .

[0034] The data processing unit uses an adaptive complementary filtering algorithm to calculate the strain gauge readings in real time. The actual tilt angle at any given moment, including the pitch angle. and roll angle .

[0035] The specific iterative formula is as follows: (1) (2) In the formula: Indicates the current data sampling time; () indicates the previous adjacent sampling time; Indicates the data collection period; , These represent the actual installation pitch angle and the actual installation roll angle calculated at the current moment, respectively. , They represent the corresponding Constantly detects the local coordinate system shaft and The rotational angular velocity of the shaft; , , They represent the corresponding The gravitational acceleration components detected at any given time along three orthogonal axes; This represents the adaptive filtering weighting coefficient, whose value is dynamically adjusted according to the vibration variance of the accelerometer to balance the high-frequency dynamic response and low-frequency drift elimination.

[0036] While calculating the angle, raw physical quantities are collected, such as the natural vibration frequency of the vibrating wire strain gauge. and the temperature value at the current measuring point Preliminary physical conversion and initial temperature compensation are performed using formula (3): (3) In the formula, Corresponding to X-axis, Y-axis, or Z-axis measurement channels; This represents the original measured strain after initial compensation; This indicates the factory physical sensitivity coefficient of the corresponding channel sensor; and These represent the currently measured frequency value and the frequency value under the initial reference state, respectively. and : These represent the current temperature and the reference temperature at the initial stage of installation, respectively; This represents the coefficient of linear expansion of the steel sleeve of the strain gauge; This represents the coefficient of linear expansion of the dam concrete surrounding the measuring point.

[0037] Step 2: Calculate the cosine matrix of the actual installation direction.

[0038] Define the global geospatial coordinate system of the dam as follows: ,in The axis extends vertically upwards along the height of the dam. The axis moves horizontally forward along the river. The axis is along the dam axis. The local measurement coordinate system of the strain gauge is defined as follows: .

[0039] Based on the actual installation angle calculated in step one and A three-dimensional rotation matrix, namely the direction cosine matrix, is constructed to transform the strain gauge's local coordinate system to the dam's global coordinate system. : (4) In the formula, each matrix element ,in This represents the direction cosine of the local coordinate axis relative to the global coordinate axis.

[0040] Therefore, it can be determined that, under actual installation conditions, the three-dimensional projection vectors of the actual axes of the X-axis, Y-axis, and Z-axis strain gauges in the global coordinate system of the dam are as follows: The actual direction vector of the X-axis strain gauge: ; The actual direction vector of the Y-axis strain gauge: ; The actual direction vector of the Z-axis strain gauge: .

[0041] Step 3: Spatial three-dimensional strain correction decoupling calculation.

[0042] The true three-dimensional symmetric strain tensor of the dam body at this measuring point is defined as follows: : (5) In the formula, diagonal elements , , Representing the true positive strain in the global direction of the dam, the off-diagonal elements , , These represent shear strain, respectively.

[0043] According to the elastic strain projection theory, the initial compensation strain in each axis actually measured by the sensor , and The projection relationship with the actual direction vector is as follows: (6) (7) (8) Since this scheme has at least three orthogonal measurement channels (X-axis, Y-axis, and Z-axis), a closed matrix solution equation can be established. Under the global coordinates of the dam, matrix operations are used to merge and reconstruct equations 6, 7, and 8, deriving the true normal strain decoupling correction calculation equation: (9) In the formula, , , These represent the dam obtained after the correction and decoupling in the global coordinate system. Axial, Axial and True normal strain in the axial direction; The transformation decoupling matrix is ​​composed of the squared cosine terms of the directions calculated from the actual installation angles. The matrix has the following structural equation: (10) Represents the transformation decoupling matrix The inverse matrix; The vector representing the spatial shear strain disturbance compensation term is defined as follows: (11) in, , , This is the initial value for shear strain evaluation established based on the pre-stored local principal stress ratios at the measuring points in the elastic finite element calculation model of the dam. In each iteration, this value is obtained by inputting the value calculated at the previous time step. , , Perform a feedback-based approximation until the correction value converges. If high-precision shear term correction is not required, it can be applied during the rough calculation. Let it be the zero vector.

[0044] Step 4: Dam strain state analysis and assessment.

[0045] After obtaining the true normal strain after high-precision geometric correction, it is necessary to further filter out the non-mechanical strain of the concrete to determine the load-bearing safety state.

[0046] Based on the volumetric changes of the dam and the evolution characteristics of concrete materials, the actual load-mechanical strain of the dam in a specific direction is calculated using a data processing unit. ,by Taking the direction of the principal force on the shaft as an example: (12) In the formula, This represents the actual load strain of the dam under its own weight and water load. This represents the true Z-direction normal strain value after spatial correction in step three; This represents the amount of autogenous volume shrinkage deformation that occurs in concrete as it matures over time. This indicates the amount of shrinkage deformation of concrete during drying and heat recovery. This indicates that the dam concrete material at the start of loading is... The calculation time is The creep function corresponding to the time; Indicates loading age The elastic modulus of concrete at that moment.

[0047] Using the effective mechanical stress obtained after multiple noise reduction processes, a dam safety status assessment index is defined: (13) In the formula, This represents the static elastic modulus of the concrete dam at the current moment; This represents the standard tensile strength design value corresponding to the concrete age at the calculation time.

[0048] The data processing unit performs multi-level health diagnosis classification of the dam based on the calculated DI index, for example: like The system determines that the dam is in a completely healthy and safe state and outputs a normal diagnostic status. like If it is determined that the dam material has developed microcracks and deteriorated or that there is excessive stress concentration, an early warning signal will be output and a manual on-site inspection will be instructed. like If a high risk of fracture or cracking is detected in the dam body, an alarm signal is immediately output and the safety emergency plan is automatically activated.

[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims. Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A strain gauge for concrete dams based on a MEMS gyroscope, comprising a strain gauge body (2), wherein at least X-axis, Y-axis and Z-axis strain gauges (1) are provided on the strain gauge body (2), characterized in that, Also includes: MEMS gyroscope (4) is installed on the upper part of Z-axis strain gauge (1) to detect the tilt angle of strain gauge body (2); The data acquisition unit is used to acquire the tilt angle data output by the MEMS gyroscope (4) and the strain data output by the strain gauge body (2); The data processing unit, communicatively connected to the data acquisition unit, is used to receive tilt angle data and strain data, and perform the following steps: The actual installation angle of the strain gauge body (2) in three-dimensional space is calculated based on the tilt angle data; Based on the actual installation angle, a three-dimensional spatial rotation matrix is ​​constructed, and the original strain data output by the X-axis, Y-axis and Z-axis strain gauges (1) are spatially decoupled and geometrically corrected to obtain the corrected strain data in the corresponding global coordinate system of the dam. Non-load strain elimination analysis is performed on the corrected strain data to obtain the true load strain of the dam, so as to determine the strain safety state of the dam.

2. The strain gauge for concrete dams based on MEMS gyroscope according to claim 1, characterized in that: The top of the Z-axis strain gauge (1) is fixedly provided with a mounting bracket (6), and the MEMS gyroscope (4) is fixedly installed on the mounting bracket (6).

3. The strain gauge for concrete dams based on MEMS gyroscope according to claim 1, characterized in that: The data acquisition unit includes a data acquisition module and a communication module. The tilt angle data acquired by the data acquisition module includes angular velocity data output by the MEMS gyroscope (4) and acceleration data output by the built-in accelerometer of the MEMS gyroscope (4). The communication module uses a hydraulic cable (3) to connect the data acquisition unit to the external data processing unit.

4. The strain gauge for concrete dams based on MEMS gyroscope according to claim 1, characterized in that: The data processing unit also includes a data storage module for storing the acquired raw data and corrected strain data.

5. The strain gauge for concrete dams based on a MEMS gyroscope according to claim 3, characterized in that: The steps of the data processing unit in calculating the actual installation angle based on the tilt angle data include: Based on the adaptive complementary filtering algorithm, the angular velocity data and acceleration data are fused by time iteration to eliminate dynamic vibration noise and zero drift, and the real-time pitch angle and real-time roll angle of the strain gauge body (2) are calculated.

6. The strain gauge for concrete dams based on MEMS gyroscope according to claim 1, characterized in that: The steps of the data processing unit to correct the original strain data according to the actual installation angle include: Obtain the global coordinate system of the dam and the local measurement coordinate system of the strain gauge body (2); A three-dimensional spatial rotation matrix is ​​constructed using the actual installation angle to determine the projection direction cosines of the X-axis, Y-axis and Z-axis strain gauges (1) in the global coordinate system; Based on the principle of three-dimensional principal strain projection, a set of directional projection equations consisting of three projection equations is established. A 3×3 dimension transformation decoupling matrix is ​​constructed through matrix processing, and the shear strain disturbance compensation term caused by spatial shear strain is extracted. The original strain data is input into the decoupled correction model composed of the transformation decoupling matrix and the shear strain disturbance compensation term. The true normal strain in the global coordinate system of the corresponding dam is obtained by matrix inversion operation, which is used as the corrected strain data.

7. The strain gauge for concrete dams based on a MEMS gyroscope according to claim 6, characterized in that; The shear strain disturbance compensation term is calculated using an adaptive feedback approximation iterative method, and its initial value is determined based on the shear stress scaling factor of the pre-stored dam finite element model.

8. The strain gauge for concrete dams based on MEMS gyroscope according to claim 1, characterized in that: Before spatial decoupling and geometric correction, the original strain data is first calculated using temperature compensation to eliminate spurious strains caused by the difference in thermal shrinkage between the strain gauge material and the dam concrete.

9. The strain gauge for concrete dams based on a MEMS gyroscope according to claim 1, characterized in that, The steps of the data processing unit to perform non-load strain elimination analysis on the corrected strain data include: subtracting the autogenous shrinkage strain, drying shrinkage strain, and creep cumulative strain of the dam concrete from the corrected strain data to obtain the true load strain of the dam.

10. The strain gauge for concrete dams based on a MEMS gyroscope according to claim 9, characterized in that, The steps by which the data processing unit determines the strain safety status of the dam include: Calculate the ratio of the actual load strain to the tensile strength of the concrete at the current age, and construct a dam safety status assessment index based on the static elastic modulus. The dam safety status assessment index is compared with a preset safety threshold, and the corresponding normal, early warning or alarm status signal is output.

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