Universal joint type flexible intelligent displacement meter

Abstract

The invention relates to the technical field of geotechnical engineering monitoring, and discloses a universal joint type flexible intelligent displacement meter which comprises a measuring chain formed by connecting a plurality of monitoring units in series, and each monitoring unit comprises a rigid segment, a cross universal joint, an angle sensor, a micro-control unit and an accelerometer. The rigid segments are integrated with electronic elements and are connected with the adjacent segments through the cross universal joints to form flexible links capable of adapting to three-dimensional deformation of a soil body; in the working process, the micro-control unit solves the absolute inclination angle of the rigid section through a gravity vector sensed by the accelerometer so as to determine vertical projection; a horizontal projection is deduced by using the relative rotation angle of the cross universal joint measured by the angle sensor; and fusing multi-sensor data through a space vector accumulation algorithm, and reconstructing the three-dimensional space form of the measurement chain section by section. According to the invention, high-precision, automatic and synchronous monitoring of internal settlement and horizontal displacement of the deep and thick covering layer is realized, and the technical problems that a rigid inclinometer cannot adapt to large deformation and the precision of flexible equipment is uncontrollable are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering monitoring, in particular to a universal joint type flexible intelligent displacement meter. BACKGROUND

[0002] In the field of geotechnical engineering such as earth and rockfill dams, slope engineering and deep foundation pits, deformation monitoring inside the soil body is a key means to evaluate the safety and stability of the structure. At present, for the deformation monitoring inside deep overburden or high fill body, the existing technology still has several technical problems to be solved in terms of monitoring dimension, structural adaptability and data transmission stability.

[0003] Firstly, the traditional geotechnical engineering monitoring technology usually implements settlement monitoring and horizontal displacement monitoring as two independent systems. For example, water pipe type settlement meters or electromagnetic type settlement meters are often used to measure vertical settlement, while inclinometer pipes are used in combination with active inclinometers or fixed inclinometer sensors to measure horizontal displacement. This separate monitoring method not only requires drilling multiple holes or excavating multiple trenches at the same monitoring section, increasing construction cost and on-site operation complexity, but also makes it difficult to simultaneously obtain high-precision three-dimensional spatial deformation data at the same physical point. Spatial and temporal asynchronization of data makes it difficult for technical personnel to accurately construct a three-dimensional deformation field inside the soil body, limiting in-depth analysis of the deformation mechanism of complex geotechnical structures.

[0004] Secondly, in terms of mechanical structure of monitoring equipment, the existing inclinometer pipe or settlement pipe mostly uses continuous rigid pipe material (such as PVC pipe or metal pipe). When deep soil body undergoes large shear deformation or non-uniform settlement, due to the bending stiffness of rigid pipe material being much greater than that of the surrounding soil body, the pipe body often cannot deform synchronously with the soil body, easily causing pipe-soil separation or suspension phenomenon. This stiffness mismatch in pipe-soil interaction will result in the monitored displacement being less than the actual displacement of the soil body, affecting the authenticity of the monitoring data. Although there are currently flexible monitoring technologies based on optical fiber sensing, the purely flexible cable structure lacks rigid motion constraints and is prone to local buckling or twisting under complex soil pressure, making it difficult to accurately invert its geometric shape in space only through strain data, resulting in large position cumulative error in long distance measurement.

[0005] In addition, deep geotechnical monitoring often faces the challenge of long-distance signal transmission. Most existing multi-point array sensors use analog signal transmission or centralized data acquisition architecture. When the monitoring depth reaches tens of meters or even hundreds of meters, analog signals are easily affected by electromagnetic interference and signal attenuation during long cable transmission, resulting in a decrease in signal-to-noise ratio. The centralized acquisition architecture needs to transmit a large amount of raw data to the ground host for processing, which not only occupies the bandwidth of the communication bus and reduces the system's patrol rate, but also causes a large amount of data loss or error codes due to local interference in the communication line, making it difficult to meet the requirements of long-term automatic monitoring for data stability and reliability. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a universal joint type flexible intelligent displacement meter, which solves the problem that in the existing geotechnical engineering monitoring technology, under the condition of horizontal or inclined burial, due to the poor deformation transmission of the flexible connection structure or the rigidity structure cannot adapt to large deformation, the internal settlement and horizontal displacement of the monitoring object cannot be synchronously and accurately obtained.

[0007] To achieve the above purpose, the present application is realized by the following technical scheme: a universal joint type flexible intelligent displacement meter, which is based on a motion chain structure alternately connected by rigid segments and cross universal joints, uses the gravity vector and the relative angle to deduce the spatial form, and realizes the three-dimensional measurement of the internal deformation of the soil or structure. The measurement chain is composed of a plurality of monitoring units connected in series; Each monitoring unit includes a rigid segment, a cross universal joint, two angle sensors, a micro control unit and an accelerometer; The rigid segment has a sealed cavity inside for accommodating electronic components, serving as a reference unit for measurement. The center of the cross universal joint is located at the measurement node, and the cross universal joint has two orthogonal rotation axes for connecting adjacent rigid segments and allowing adjacent rigid segments to freely rotate in two orthogonal directions to adapt to the deformation of the external soil body. Two angle sensors are integrated on the two rotation axes of the cross universal joint, respectively, for measuring the rotation angles of the cross universal joint in the pitch direction and the yaw direction, respectively. The micro control unit is fixedly arranged inside the rigid segment. The accelerometer is installed on the micro control unit for sensing the gravitational acceleration and measuring the absolute inclination angle of the rigid segment relative to the gravity direction. The micro control unit is configured to control the angle sensor and the accelerometer to collect, process and store data, and output the displacement data and the original monitoring data after solving through the bus interface.

[0008] Preferably, the micro control unit internally solidifies a displacement calculation algorithm, which is configured to: receive data of two angle sensors and data of the accelerometer, and perform filtering and twist correction operation on the collected data; calculate the absolute inclination angle of the rigid segment based on the gravity acceleration component measured by the accelerometer, and further calculate the height difference between the two ends of the rigid segment in the vertical direction; use the relative rotation angle data measured by two angle sensors, combined with the height difference, to derive the coordinate vector of the measurement node in three-dimensional space.

[0009] Preferably, the cross universal joint is externally sleeved with a flexible hose, two ends of the flexible hose are respectively sealed and connected with the outer wall of the adjacent rigid segment, thereby forming a continuous waterproof protective layer outside the measurement chain to block the entry of external moisture into the internal mechanical structure and circuit. The plurality of micro control units in the measurement chain are connected in series through CAN bus to form a distributed sensing network for data communication and clock synchronization between nodes.

[0010] Preferably, the accelerometer is a three-axis accelerometer, and the installation direction is configured as: the Z axis of the accelerometer is parallel to the center line of the rigid segment, and the plane where the XY axis of the accelerometer is located is perpendicular to the center line. In cooperation therewith, one of the angle sensors is installed on the vertical rotation shaft of the cross universal joint for measuring the deflection angle; the other angle sensor is installed on the horizontal rotation shaft of the cross universal joint for measuring the pitch angle.

[0011] Preferably, the measurement chain is connected with a data acquisition box through a communication cable to form a field monitoring system. The data acquisition box includes a main controller, a communication gateway, a power module, a storage module and a human-computer interaction module. The main controller is used to execute automatic measurement instructions, gather data of each monitoring unit and perform data packaging; the communication gateway is used to upload the packaged data to an external cloud service platform and receive remote instructions; the power module is used to power the data acquisition box and the measurement chain; the storage module is used to locally save monitoring data; the human-computer interaction module is configured with a state indicating lamp and a debugging interface for viewing device state and performing field maintenance.

[0012] Preferably, the micro control unit performs the following steps for calculating the vertical coordinate: obtaining the gravity acceleration components of the accelerometer in three axes; calculating the square root of the sum of squares of the gravity acceleration components in the three axes as the total acceleration module length; calculating the ratio of the Z-axis gravity acceleration component to the total acceleration module length; obtaining the absolute inclination angle by inverse cosine operation on the ratio; calculating the projection length of the rigid segment in the vertical direction according to the known geometric length of the rigid segment and the absolute inclination angle; and accumulating the projection length to the vertical coordinate of the previous measurement node to obtain the vertical coordinate of the current measurement node.

[0013] Preferably, the micro control unit performs the following steps for calculating the horizontal coordinate: defining the center of the cross gimbal as the local coordinate origin; constructing a rotation matrix describing the relative rotation of two adjacent rigid segments according to the deflection angle and the pitch angle measured by the two angle sensors respectively; and deducing the horizontal coordinate of the current measurement node by using the space vector accumulation algorithm based on the rotation matrix, the coordinate vector of the previous measurement node and the length of the rigid segment.

[0014] Preferably, the gimbal type flexible intelligent displacement meter is further configured to communicate with a cloud service platform. The cloud service platform is configured to receive the monitoring data from the data acquisition box; provide a data visualization interface to display the settlement distribution and horizontal displacement distribution of the measurement chain through a three-dimensional model, and compare historical change data. Further, the cloud service platform is built-in with an intelligent early warning module, which is configured to monitor the displacement amount and displacement rate in real time; and automatically send early warning information to the management personnel when the monitored displacement amount exceeds a preset threshold value and when the monitored displacement rate exceeds a preset threshold value.

[0015] Preferably, the monitoring process of the gimbal type flexible intelligent displacement meter comprises the following steps: S1, during the construction period, laying the measurement chain in the monitoring trench, aligning and fixing the monitoring unit at the head end with the reference point of known coordinates, and then backfilling the monitoring trench so that the measurement chain can displace synchronously with the soil body around the monitoring trench; S2, driving the measurement chain by the data acquisition box to synchronously collect the data of the two angle sensors of all nodes on the chain and the data of the accelerometer; S3, performing the filtering processing on the collected data; calculating the absolute inclination angle by using the gravity acceleration component; calculating the relative included angle of adjacent rigid segments by using the data of the two angle sensors; and fusing the relative included angle data and the absolute inclination angle data to reconstruct the three-dimensional coordinates of each measurement node by space geometry algorithm; S4, receiving the monitoring data through the cloud service platform, generating a monitoring report of the horizontal displacement and the settlement, and triggering an early warning when a deformation anomaly is identified.

[0016] The application uses an accelerometer to obtain an absolute attitude to determine vertical deformation, and uses an angle sensor at a cross universal joint to obtain a relative attitude to determine horizontal deformation, and through fixed-length constraint of a rigid segment and spatial fusion of multi-sensor data, realizes automatic and synchronous monitoring of settlement and horizontal displacement inside a deep overburden layer such as a rock-fill dam.

[0017] The application provides a universal-joint type flexible intelligent displacement meter. 1. The application sets an accelerometer for sensing gravity acceleration in a rigid segment, sets an angle sensor for measuring relative rotation angle at a cross universal joint of a connecting node, uses a gravity vector to calculate vertical settlement, and uses relative rotation angle to deduce horizontal displacement; this multi-sensor fusion mechanism enables the device to synchronously obtain settlement and horizontal displacement of a monitoring object in a single measurement, realizes three-dimensional reconstruction of internal deformation of a soil body, and solves the problem that traditional monitoring devices can usually only measure deformation in a single dimension.

[0018] 2. The application adopts a chain structure with rigid segments and cross universal joints alternately connected in series, uses the free rotation characteristics of the cross universal joints in two orthogonal directions to enable the measurement chain to adaptively bend following shear or non-uniform settlement of surrounding soil body; compared with an integral flexible pipe or a rigid inclinometer pipe, this structure reduces the pipe-soil separation phenomenon caused by excessive pipe body rigidity, ensures consistency between the measurement chain and soil body deformation, and thus improves the authenticity of deformation monitoring data.

[0019] 3. The application independently integrates a micro control unit in each monitoring unit and solidifies a displacement calculation algorithm, and constructs a distributed sensing network based on a CAN bus; each node independently completes data acquisition, filtering and coordinate calculation, and only transmits processed displacement data upward, this distributed computing architecture reduces data load of long-distance communication, avoids the problem that analog signals are easily disturbed in long-distance transmission, and improves data stability of a deep geotechnical monitoring system. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A structural composition diagram of the measurement chain is provided for the application; Figure 2 A geometric principle diagram of angle calculation and spatial coordinate reconstruction is provided for the application; Figure 3 A whole connecting architecture diagram of the universal-joint type flexible intelligent displacement meter is provided for the application; Figure 4The logical flow chart of the displacement calculation algorithm of the present application; Figure 5 The flowchart of the field installation and monitoring method of the present application.

[0021] Wherein, 1, rigid segment; 2, micro control unit; 3, accelerometer; 4, cross universal joint; 5, angle sensor. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the specification of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] Referring to the drawings Figure 1 and the drawings Figure 3 The present application provides a universal joint type flexible intelligent displacement meter, which is mainly used in the field of geotechnical engineering monitoring, and is particularly suitable for settlement and horizontal displacement monitoring in deep overburden of earth-rock dams, slopes, roadbeds and the like. The universal joint type flexible intelligent displacement meter is composed of a measuring chain buried in the soil body, a collection control terminal arranged on the ground surface and a remote monitoring center in structure. The overall structural design enables it to adapt to the working conditions of being horizontally buried or obliquely buried in the dam body, and meets the long-term monitoring requirements of large deformation areas.

[0024] The measuring chain, as a core sensing component, is composed of a plurality of monitoring units connected in series. Each monitoring unit includes a rigid segment 1 and a cross universal joint 4 in physical structure. The rigid segment 1 is a tubular member with a predetermined length and rigidity, and forms a closed cavity space inside for accommodating a circuit board. The cross universal joint 4 is located between two adjacent rigid segments 1, and plays a mechanical connection and joint rotation role. The cross universal joint 4 has a horizontal rotation shaft and a vertical rotation shaft, which are perpendicular to each other and intersect at a point, and the intersection point is defined as a measuring node. Through this connection mode, the two adjacent rigid segments 1 can rotate freely in the pitch direction and the left-right deflection direction around the center of the cross universal joint 4, thereby forming a flexible link with multiple degrees of freedom. When the surrounding soil body deforms, the displacement field of the soil body will drive the measuring chain to move cooperatively, changing the spatial posture and position of each rigid segment 1.

[0025] In order to realize the digital reconstruction of the link shape, a micro control unit 2, an accelerometer 3 and an angle sensor 5 are integrated in each monitoring unit. The micro control unit 2 is fixedly installed on a circuit board in the rigid segment 1 as an independent data processing node. The accelerometer 3 is electrically connected to the micro control unit 2, and the physical installation position is in a specific alignment relationship with the geometric center axis of the rigid segment 1, for sensing the component of the gravity acceleration vector in the rigid segment 1 coordinate system. Two angle sensors 5 are respectively installed on two orthogonal rotating shafts of the cross universal joint 4, for directly measuring the relative rotation angle between two adjacent rigid segments 1, including the pitch angle and the yaw angle.

[0026] The data acquisition box is connected with the first end of the measurement chain through a communication cable as a convergence node on site. The data acquisition box is internally integrated with a main controller, a communication gateway, a power module, a storage module and a human-computer interaction module. The power module is responsible for converting external power into the required direct current voltage, and supplying power to the measurement chain underground through the cable. The human-computer interaction module is configured with a state indicating lamp, a display screen and a debugging interface for on-site state monitoring. The main controller communicates with the measurement chain as a whole through an RS-485 bus, sends a synchronous acquisition instruction or reads the calculated displacement data. The communication gateway is configured with a wireless communication module, which sends the packaged monitoring data to the cloud service platform by using a 4G, 5G or NB-IoT network.

[0027] The cloud service platform is deployed on a remote server end and runs a database software and a three-dimensional visualization software. The cloud service platform receives the data stream from the data acquisition box, analyzes and stores the data, and draws the spatial shape curve of the measurement chain in a virtual environment according to the three-dimensional coordinate data of each measurement node uploaded. The cumulative settlement and the horizontal displacement of the monitoring object at any position are calculated by comparing the shape curves at different time points.

[0028] The working principle of the application is based on the segmented space geometric reconstruction technology of multi-sensor fusion. After the displacement meter is powered on and enters the working state, the micro control unit 2 controls the accelerometer 3 and the angle sensor 5 to synchronously collect original data. The gravity vector perceived by the accelerometer 3 provides an absolute attitude reference for each rigid segment 1 relative to the direction of the earth's gravity, thereby establishing the inclination degree of the rigid segment 1 in the vertical plane; the data measured by the angle sensor 5 provides the relative geometric constraint relationship of adjacent segments in the three-dimensional space. The micro control unit 2 determines the vertical coordinate increment by using the absolute inclination angle calculated from the accelerometer 3 data, and constructs a rotation matrix by using the angle sensor 5 data and deduces the vector component in the horizontal direction.

[0029] In this way, the physically connected rigid segments 1 are abstracted as spatial vectors connected end to end, and the projection components of each vector in the spatial coordinate system are accumulated section by section from the reference point with known coordinates, so as to restore the trajectory of the entire measurement chain. The entire monitoring process is automatically completed by the distributed sensing network inside the measurement chain. The micro control units 2 of multiple monitoring units are connected in series through the CAN bus to form a master-slave or peer-to-peer network structure. This architecture allows massive raw sensor data to be transmitted to the ground without being transmitted to the ground, and the filtered, corrected and coordinate component calculation is completed locally by each micro control unit 2. Only the processed coordinate increment data or state feature data is uploaded to the data acquisition box. This edge computing mode significantly reduces the data throughput of the bus and improves the anti-interference ability and real-time performance of the displacement meter during long-distance transmission.

[0030] Referring to the accompanying drawings Figure 1 and the accompanying drawings Figure 3 The main support structure of the monitoring unit is composed of rigid segments 1. The rigid segments 1 are made of high-strength stainless steel or hard aluminum alloy materials in a circular tube structure to ensure that they do not bend and deform when subjected to external soil pressure. Inside the rigid segments 1, a sealed cavity is formed by precise mechanical processing. The sealed cavity is used to install the PCB circuit board carrying electronic components and the power management circuit. The two ends are sealed by end caps with O-shaped sealing rings. The center or edge of the end cap is reserved with a sealed wire hole or airtight connector. The communication and power supply cables pass through the wire hole to realize electrical series connection between adjacent monitoring units while maintaining the sealing of the cavity. The end cap is airtight packaged by screw locking or adhesive process, with a protection level of IP68 standard, to prevent internal circuit short circuit or corrosion caused by underground water infiltration.

[0031] The mechanical connection between the two adjacent rigid segments 1 is achieved through the cross universal joint 4. The connection node has two independent rotational degrees of freedom: one is the pitch rotation freedom around the horizontal axis, and the other is the yaw rotation freedom around the vertical axis.

[0032] Two angle sensors 5 are integrated in the mechanical structure at the two orthogonal rotation axes of the cross universal joint 4. This integrated manner allows the angle sensor 5 to directly pick up the angular change of the rigid segment 1 relative to the cross axis rotation, and the measurement of the two dimensions does not interfere with each other.

[0033] In order to protect the precision cross universal joint 4 and the exposed communication and power supply cables from the external environment, a section of flexible hose is sleeved outside the cross universal joint 4. The flexible hose is made of corrosion-resistant, aging-resistant and good elastic rubber or polyurethane material, such as EPDM bellows. The inner diameter of the flexible hose is slightly larger than the maximum outer contour diameter of the cross universal joint 4, leaving enough space for the universal joint to rotate full angle without interference. The length of the flexible hose covers the entire node area, and its two ends extend to the outer wall of the rigid segment 1 on both sides, and are circumferentially fastened and sealed by stainless steel throat clamps or cold shrink sleeves. In this way, the flexible hose and the rigid segments 1 on both sides form a continuous, closed tubular shell, which not only ensures the flexible bending capability of the measurement chain at the joint, but also realizes the waterproof and silt protection of the entire chain.

[0034] In actual working conditions, this structure of alternating connection of rigid segments 1 and cross universal joints 4 forms a multi-degree-of-freedom chain-type articulated structure. When the surrounding soil body shears and settles, the displacement of the soil body is transmitted to the rigid segment 1 through the contact pressure. Since the bending stiffness of the rigid segment 1 itself is much larger than the rotational stiffness at the connection, the continuous deformation of the soil body is discretized into the spatial rigid body displacement of each rigid segment 1 and the rotation around the cross universal joint 4. This structural design enables the device to adapt to large deformation conditions of deep soil body, avoids the pipe-soil separation phenomenon of traditional rigid inclinometer due to excessive rigidity, and also avoids the signal drift problem caused by stretching and twisting of completely flexible sensing cable, ensuring the accuracy of mechanical deformation transmission.

[0035] The micro control unit 2 is fixedly installed inside the rigid segment 1, and a low-power, high-performance embedded microprocessor is selected, such as a single-chip microcomputer based on ARM Cortex-M core. The micro control unit 2 is integrated with a multi-channel analog-to-digital converter, a serial peripheral interface and a controller area network controller. The micro control unit 2 is connected to the accelerometer 3 and the angle sensor 5 through a circuit, and is configured to control data acquisition of the sensors, perform preliminary data processing and storage, and interact with external devices through a communication interface.

[0036] The accelerometer 3 selects a high-precision micro-electro-mechanical system three-axis accelerometer 3 chip, which is installed on the circuit board where the micro control unit 2 is located. According to the definition of the measurement coordinate system, the Z axis of the accelerometer 3 (i.e. the main sensitive axis for sensing the gravitational acceleration) is parallel to the central axis of the rigid segment 1, and the plane where the X and Y axes are perpendicular to the central axis of the rigid segment 1. When the rigid segment 1 is inclined, the ratio of the Z axis component of the accelerometer 3 to the total modulus of the gravitational acceleration changes, and this change is used to represent the absolute inclination angle of the rigid segment 1.

[0037] Two angle sensors 5 are directly integrated on two orthogonal rotation axes of the cross universal joint 4. One of the angle sensors 5 is installed on the vertical rotation axis of the cross universal joint 4 for measuring the deflection angle in the horizontal plane; the other angle sensor 5 is installed on the horizontal rotation axis (i.e. the direction perpendicular to the axis of the rigid segment 1 and perpendicular to the vertical rotation axis) of the cross universal joint 4 for measuring the pitch angle in the vertical plane. The angle sensors 5 transmit the collected analog voltage signals or digital coded signals to the micro control unit 2 through cables, and the micro control unit 2 labels the two signals as deflection angle data and pitch angle data according to the physical installation position.

[0038] In terms of communication networking, the multiple micro control units 2 inside the measurement chain are connected in series using the CAN bus communication protocol to form a distributed sensing network. The communication cable passes through the internal cavity of the rigid segment 1 and has a redundant length of bending section reserved when passing through the cross universal joint 4 to avoid breaking the cable when the joint rotates. As a whole, the measurement chain converts the CAN bus signal into an RS-485 bus signal at the head end through a protocol conversion circuit, thereby realizing long-distance data transmission.

[0039] The data acquisition box includes a main controller, a communication gateway, a power module, a storage module and a human-computer interaction module. The main controller is connected with the measurement chain through the RS-485 bus interface and is configured to send automatic measurement instructions to the measurement chain and gather sensor data uploaded by each monitoring unit. The communication gateway is connected with the main controller and is internally provided with a wireless communication module, which is configured to upload the data encapsulated by the main controller to the cloud service platform through a wireless network and receive remote instructions from the cloud service platform. The power module converts the input power and simultaneously supplies power to each module in the data acquisition box and the measurement chain underground. The storage module is used to locally and cyclically save monitoring data. The human-computer interaction module includes a state indicator lamp, a display screen and a debugging interface arranged on the surface of the box.

[0040] Referring to Figs. 1 and 2, Figure 2 and Figs. 3 and 4, Figure 4 the displacement solving process mainly includes four core steps of data preprocessing, vertical coordinate solving, horizontal coordinate solving and spatial position reconstruction.

[0041] In the data preprocessing stage, the system first filters the collected original data to eliminate random errors caused by environmental vibration or electronic noise. The micro control unit 2 uses a sliding average filtering algorithm to establish a first-in-first-out (FIFO) data buffer with a preset length. For the acceleration original data collected by the accelerometer 3 and the angle original data collected by the angle sensor 5, the algorithm continuously reads sampling values (for example, ), and the arithmetic mean thereof is calculated as the current effective measurement value. In addition, the sliding average filtering algorithm also contains a twist correction link, by reading the installation error compensation parameters preset in the memory, the zero point deviation of the angle sensor 5 is corrected, and the output angle value is ensured to be the true rotation angle relative to the mechanical zero position.

[0042] The vertical coordinate calculation relies on the perception of the gravity vector by the three-axis accelerometer 3. The following coordinate system is defined in this embodiment: let the axis be the river direction, the axis be the transverse river direction, and the axis be the vertical direction. The head node (node 0) of the measurement chain is fixed, and its coordinates are . The rigid segment 1 in the first monitoring unit is defined as the first rigid segment 1, and the end of the first rigid segment 1 (i.e. the center of the cross universal joint 4) is defined as the first node, whose spatial coordinates are denoted as .

[0043] The geometric length of the rigid segment 1 is set to be a unit length (i.e. ). The three axial gravity acceleration components sensed by the accelerometer 3 inside the first rigid segment 1 are defined as , and . Among them, the Z axis of the accelerometer 3 is parallel to the center line of the rigid segment 1, and the XY axis is perpendicular to the center line of the rigid segment 1.

[0044] Based on the gravity acceleration components, the absolute inclination of the first rigid segment 1 is first calculated. The absolute inclination combines the component distribution of the gravity vector on each axis, and the calculation formula is as follows: ; wherein: denotes the absolute inclination of the first rigid segment 1; denotes the vertical coordinate of the first node; denotes the vertical coordinate of the first node; , and denote the X, Y, and Z axial gravity acceleration components sensed by the accelerometer 3 inside the first rigid segment 1; denotes the total modulus of the gravity acceleration at the current position; It represents the magnitude of the component of gravitational acceleration in the plane perpendicular to the axis of rigid segment 1.

[0045] Based on the above inclination angle relationship, the first The vertical coordinates of each node Through the previous node (the first) The vertical coordinates of the nodes The result is obtained by cumulative calculation, that is .

[0046] After completing the vertical coordinates After the calculation, the three-dimensional spatial coordinates are reconstructed segment by segment using data from angle sensor 5 combined with spatial geometric algorithms. The intersection point of the universal joint 4 is set as the origin of the local coordinate system. When two adjacent rigid segments 1 rotate relative to each other, the rotation is decomposed into: the previous segment (the first segment) 1) The deflection angle of a rigid segment rotating about the vertical axis (Z-axis) and the next section (the first) 1) The pitch angle of rotation of a rigid segment about the horizontal axis (X-axis) .

[0047] Definition of the first The centerline direction vector of rigid segment 1 Its expression is: ; in: , The first rigid segment 1 and the first The river-direction coordinates of rigid segment 1; , The first rigid segment 1 and the first The vertical coordinates of rigid segment 1; Representing the The projection component of a rigid segment 1 in the transverse direction.

[0048] Let the spatial angle between two adjacent rigid segments 1 be . Based on the vector dot product formula and rotation transformation relationship, the direction vectors of two adjacent segments... and The following equation must be satisfied: ; in: Indicates the first rigid segment 1 and the first The spatial angle between the rigid segments 1; Indicates the first The deflection angle data measured by the universal joint 4 in the monitoring unit; Indicates the first Pitch angle data measured by the universal joint 4 in the monitoring unit; Indicates the first The centerline direction vector of rigid segment 1; Indicates the first The centerline direction vector of rigid segment 1.

[0049] In order to solve the... The coordinates of each node along the river Define the following intermediate variables and increment symbols: remember For the first The projected length of rigid segment 1 in the X-axis direction: .

[0050] remember For the first The projected length of rigid segment 1 in the Z-axis direction: .

[0051] remember For the first The projected length of rigid segment 1 in the Z-axis direction (this value has been obtained through the vertical calculation step): .

[0052] Define auxiliary calculation variables and : ; ; in: For the first The projection components of rigid segment 1 in the transverse direction; It is an intermediate calculation parameter that combines the cosine value of the spatial angle with the product of the vertical increment, and is a dimensionless intermediate variable.

[0053] Based on the above variables, the first The coordinates of each node along the river The following recursive formula can be used to solve the problem: .

[0054] The formula utilizes the downstream coordinates of the previous node. Given the current geometric constraints, the downstream coordinates of the next node are calculated. By accumulating the coordinates segment by segment from the reference point using the above algorithm, the microcontroller unit 2 can calculate the three-dimensional coordinates of each measurement node relative to the reference point in real time. When changes in the monitoring environment lead to alterations in the measurement chain configuration, the coordinates of each node are updated accordingly. By comparing the current coordinate sequence with the baseline coordinate sequence at the time of initial installation, the cumulative displacement of each point in the longitudinal, transverse, and vertical directions can be determined, thereby achieving synchronous monitoring of soil settlement and horizontal displacement.

Claims

1. A universal joint type flexible intelligent displacement gauge, characterized in that, The measurement chain comprises multiple monitoring units connected in series, each monitoring unit comprising: Rigid segment (1), the interior of which forms a sealed cavity for accommodating electronic components; A universal joint (4) with its center located at the measuring node has two orthogonal shafts for connecting adjacent rigid segments (1) and enabling the adjacent rigid segments (1) to rotate freely in two orthogonal directions. Two angle sensors (5) are integrated into the two shafts of the universal joint (4) respectively, and are used to measure the pitch angle and yaw angle of the universal joint (4); The microcontroller unit (2) is fixedly disposed inside the rigid segment (1); An accelerometer (3), which is mounted on the microcontroller unit (2), is used to sense gravitational acceleration and measure the absolute tilt angle of the rigid segment (1); The microcontroller unit (2) is configured to control the data acquisition, data processing and storage of the angle sensor (5) and the accelerometer (3), and output the calculated displacement data and raw monitoring data through the bus interface.

2. The universal joint type flexible intelligent displacement gauge according to claim 1, characterized in that, The microcontroller unit (2) has a displacement calculation algorithm embedded inside, and the displacement calculation algorithm is configured as follows: The system receives data from the two angle sensors (5) and the accelerometer (3), and performs filtering and torsional correction processing on the collected data. The absolute tilt angle and the height difference between the two ends of the rigid segment (1) are calculated using the data from the accelerometer (3); By combining the data from the two angle sensors (5) with the height difference, the coordinate vector of the measuring node in three-dimensional space is reconstructed.

3. The universal joint type flexible intelligent displacement gauge according to claim 1, characterized in that, The universal joint (4) is fitted with a flexible hose, and the two ends of the flexible hose are respectively sealed to the outer wall of the adjacent rigid segment (1) to form a continuous waterproof protective layer. The multiple microcontrollers (2) in the measurement chain are connected in series via a CAN bus to form a distributed sensing network.

4. The universal joint type flexible intelligent displacement gauge according to claim 1, characterized in that, The accelerometer (3) is a triaxial accelerometer (3). The Z-axis of the accelerometer (3) is parallel to the center line of the rigid segment (1), and the plane containing the XY axis of the accelerometer (3) is perpendicular to the center line. One of the angle sensors (5) is mounted on the vertical shaft of the universal joint (4), and the other angle sensor (5) is mounted on the horizontal shaft of the universal joint (4).

5. A universal joint type flexible intelligent displacement gauge according to claim 2, characterized in that, The measurement chain is connected to the data acquisition box via a communication cable. The data acquisition box includes: The main controller is used to execute automatic measurement commands, collect data from each of the monitoring units, and perform data encapsulation. A communication gateway is used to upload encapsulated data to an external cloud service platform and receive remote commands. A power module for supplying power to the data acquisition box and the measurement chain; The storage module is used to store monitoring data locally; The human-computer interaction module includes status indicator lights and a debugging interface.

6. A universal joint type flexible intelligent displacement gauge according to claim 2, characterized in that, The microcontroller unit (2) is configured to calculate the vertical coordinates, and the calculation of the vertical coordinates specifically involves: Obtain the gravitational acceleration components of the accelerometer (3) in three axes; The square root of the sum of the squares of the gravitational acceleration components along the three axes is taken as the total acceleration modulus. Calculate the ratio of the Z-axis gravitational acceleration component to the total acceleration modulus; The absolute tilt angle is obtained by performing an inverse cosine operation on the ratio. The projected length of the rigid segment (1) in the vertical direction is calculated based on the length of the rigid segment (1) and the absolute tilt angle; The projected length is added to the vertical coordinate of the previous measurement node to obtain the vertical coordinate of the current measurement node.

7. A universal joint type flexible intelligent displacement gauge according to claim 2, characterized in that, The microcontroller unit (2) is configured to calculate horizontal coordinates, and the calculation of horizontal coordinates specifically involves: The center of the universal joint (4) is defined as the origin; Based on the deflection angle and pitch angle measured by the two angle sensors (5) respectively, a rotation matrix describing the relative rotation of two adjacent rigid segments (1) is constructed; Based on the rotation matrix, the coordinate vector of the previous measurement node, and the length of the rigid segment (1), the horizontal coordinates of the current measurement node are derived using a spatial vector accumulation algorithm.

8. A universal joint type flexible intelligent displacement gauge according to claim 5, characterized in that, The universal joint-type flexible intelligent displacement gauge is also configured to communicate with a cloud service platform, which is configured as follows: Receive the monitoring data from the data acquisition box; Provides a data visualization interface to display the settlement distribution and horizontal displacement distribution of the measurement chain through a 3D model; Compare with historical change data.

9. A universal joint type flexible intelligent displacement gauge according to claim 8, characterized in that, The cloud service platform has a built-in intelligent early warning module, which is configured as follows: Real-time monitoring of displacement and displacement rate; When the detected displacement exceeds a preset threshold, or when the detected displacement rate exceeds a preset threshold, an early warning message is automatically sent to the management personnel.

10. A universal joint type flexible intelligent displacement gauge according to claim 8, characterized in that, The universal joint flexible intelligent displacement gauge is configured to perform the following monitoring steps: S1. During the construction period, the measuring chain is laid in the monitoring trench, the monitoring unit at the first end is aligned and fixed with the reference point of known coordinates, and the monitoring trench is backfilled. The measuring chain deforms together with the monitoring trench. S2. Drive the measurement chain through the data acquisition box to synchronously acquire data from the two angle sensors (5) and the accelerometer (3); S3. Perform the filtering process on the collected data; calculate the absolute tilt angle using the gravitational acceleration component; calculate the relative angle between adjacent rigid segments (1) using the data from the two angle sensors (5); fuse the relative angle data and the absolute tilt angle data, and reconstruct the three-dimensional coordinates of each measurement node segment by segment using a spatial geometry algorithm; S4. Receive the monitoring data through the cloud service platform, generate monitoring reports on the horizontal displacement and settlement through the cloud service platform, and trigger an early warning when abnormal deformation is detected.

Images