Stable foundation flatness laser measuring instrument and method thereof

Abstract

The invention relates to a stable foundation flatness laser measuring instrument and a method thereof, and belongs to the field of engineering measurement and foundation detection.The method comprises the steps that S1, a disturbance isolation base, a self-stabilizing suspension measuring head and a sensing assembly are arranged; s2, starting an air source connected to the disturbance isolation base, and attenuating and limiting the physical shake of the self-stabilizing suspension measuring head within a low-frequency range; s3, starting work of the sensing assembly, rotating the laser scanner to obtain original polar coordinate data of the surface of the foundation, and capturing attitude data of the self-stabilizing suspension measuring head by the high-frequency inertial measurement unit; and S4, stopping acquisition, constructing an absolute coordinate system taking a gravity vector as an axis based on attitude data, calculating an instantaneous deflection relationship of a scanning plane of the rotary laser scanner, performing elevation reduction on original polar coordinate data, and fitting a least square plane to evaluate the flatness of the foundation. According to the invention, an original observation platform with extremely high stability is provided for the laser scanner and the inertial measurement unit, and the signal-to-noise ratio of measured data is ensured from the physical level.

Description

Technical Field

[0001] This invention relates to the field of engineering surveying and foundation testing, specifically to a stable foundation flatness laser measuring instrument and method. Background Technology

[0002] Currently, the main method for measuring the flatness of the foundation is to use laser scanning equipment that establishes a physical reference benchmark. The equipment is fixed to the area to be measured by a tripod or base, and uses a rotating laser beam to acquire polar coordinate data of the ground surface. A relative coordinate system is established with the physical base of the equipment as the reference, and the plane is fitted by algorithms such as the least squares method to evaluate the flatness of the foundation. In some specific scenarios, basic shock-absorbing pads or software filtering are also used to try to reduce environmental interference. However, most current measurement systems are based on rigid or semi-rigid connections between the equipment and the foundation. The measurement logic depends on the absolute stability of the physical support surface. During operation, the small displacement of the base itself is often ignored or regarded as a systematic error that is difficult to eliminate at the source. However, in related technologies, with the increase in construction intensity at engineering sites, the continuous high-frequency vibration and foundation disturbance generated by heavy machinery operations become unavoidable. Measurement structures based on traditional physical base support will bring some problems or weaknesses, such as the high-frequency vibration of the ground being directly transmitted to the precision probe through the rigid base, causing the measurement reference plane to tilt and shake instantaneously. This results in attitude noise being mixed into the raw data collected by the instrument, making it difficult to obtain high-precision flatness evaluation results through simple physical support in dynamic environments, which urgently needs to be improved. Therefore, a solution is urgently needed to address the problems existing in the current technology.

[0003] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure and therefore does not constitute information about prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a stable foundation flatness laser measurement instrument and method to solve the problems mentioned in the background art. The technical solution of this invention includes: S1. A disturbance isolation base, a self-stabilizing levitation probe, and a sensing component are provided. The self-stabilizing levitation probe is movably supported inside the disturbance isolation base by a spherical air bearing pair. A levitation magnetic array is provided on the swing main shaft of the self-stabilizing levitation probe. A non-contact magnetic orientation limiting unit is provided between the disturbance isolation base and the self-stabilizing levitation probe to provide torsional stiffness around the vertical axis. The sensing component is rigidly fixed to the top of the self-stabilizing levitation probe. S2. Start the air source connected to the disturbance isolation base to form an air film between the spherical air bearing pairs to isolate high-frequency vibration. Utilize the electromagnetic eddy current effect between the suspended magnetic array and the annular damping wall to generate a reverse damping force. At the same time, use the magnetic spring restoring torque generated by the magnetic azimuth limiting unit to counteract the reaction torque generated by the rotation of the rotating laser scanner, thereby attenuating and limiting the physical sway of the self-stabilizing suspended probe to a low-frequency range and keeping the azimuth angle in a quasi-static state. S3. Start the operation of the sensing component, which includes a rotating laser scanner and a high-frequency inertial measurement unit. The rotating laser scanner acquires the raw polar coordinate data of the ground surface, and the high-frequency inertial measurement unit captures the attitude data of the self-stabilizing levitating probe. S4. Stop data acquisition, construct an absolute coordinate system with the gravity vector as the axis based on the attitude data, calculate the instantaneous deflection relationship of the scanning plane of the rotating laser scanner and restore the elevation of the original polar coordinate data, and fit the least squares plane to evaluate the flatness of the foundation.

[0005] Preferably, step S3 is preceded by: Static zero-point calibration is performed, and the data variance of the high-frequency inertial measurement unit is monitored. When the data variance is lower than the set threshold for a continuous period of time, it is determined to be in a quasi-stationary state. If the variance cannot meet the threshold condition within a preset time, the threshold is automatically increased by a preset step size. If the threshold is increased to the preset maximum safety threshold upper limit and still cannot meet the condition, an environmental abnormality alarm is output and the measurement task is stopped. Alternatively, after user confirmation, the data segment with the smallest variance in the current time period is used to calculate the mean of the gyroscope and accelerometer data as the zero bias error and stored.

[0006] Preferably, the elevation restoration of the original polar coordinate data in step S4 includes: Read the pre-stored physical arm length parameter L from the center of the spherical air bearing pair of the self-stabilizing levitation probe to the center of the inertia of the high-frequency inertial measurement unit; Based on the angular velocity and angular acceleration data of the high-frequency inertial measurement unit, and combined with the physical arm length parameter, the instantaneous centripetal acceleration and instantaneous tangential acceleration generated by the swing of the self-stabilizing levitation probe are calculated. The instantaneous centripetal acceleration and instantaneous tangential acceleration are removed from the raw observation data of the high-frequency inertial measurement unit, and the gravitational acceleration vector is extracted to correct the attitude data.

[0007] Preferably, in step S1, the self-stabilizing levitation probe includes a pendulum spindle and a high-density counterweight module disposed at the bottom of the pendulum spindle. The overall center of gravity of the pendulum spindle is located below the rotation center of the spherical air bearing pair. The sensing component, the levitation magnetic array, the rotating end of the spherical air bearing pair, and the high-density counterweight module are distributed sequentially from top to bottom along the axial direction of the pendulum spindle.

[0008] Preferably, in step S1, the annular damping wall is made of copper with a wall thickness of 5 mm, and the levitation magnetic array includes eight neodymium iron boron strong magnets uniformly embedded in the circumference; the magnetic orientation limiting unit includes a radially magnetized magnet disposed on the pendulum main shaft and a fixed magnetic pole disposed on the inner wall of the support housing, the two being arranged in opposite polarities to form a non-contact magnetic orientation recovery structure.

[0009] Preferably, in step S4, for each sampling point, the horizontal arm length of the sampling point relative to the center of the probe is calculated based on the current scanning angle and distance. The horizontal arm length is multiplied by the sine of the projection tilt angle of the self-stabilizing suspended probe in the current scanning azimuth direction to obtain the vertical component error, which is then subtracted from the preliminary elevation data.

[0010] Preferably, in step S1, the disturbance isolation base includes a support housing, and a transverse bearing partition is provided inside the support housing. The stationary end of the spherical air bearing assembly is embedded in the center of the transverse bearing partition.

[0011] A stable foundation flatness laser measuring instrument includes: The disturbance isolation base has a supporting shell and an annular damping wall on its inner wall. The self-stabilizing levitation probe is suspended and supported inside the support housing by a spherical air bearing pair, and the lower end of the self-stabilizing levitation probe is provided with a levitation magnetic array that cooperates with the annular damping wall; The sensing component, coaxially rigidly mounted on top of the self-stabilizing levitation probe, includes a rotating laser scanner and a high-frequency inertial measurement unit located directly below the optical rotation center of the rotating laser scanner.

[0012] Preferably, the top of the support housing is provided with a limiting protective platform, the limiting protective platform having a central opening with an inner diameter smaller than the maximum diameter of the self-stabilizing levitation probe, for mechanically limiting the self-stabilizing levitation probe.

[0013] This invention provides a stable foundation flatness laser measurement instrument and method, which has the following improvements and advantages compared with the prior art: 1. This invention constructs a non-contact support structure using spherical air bearing pairs. The tiny gaps in the air film effectively isolate high-frequency mechanical vibrations from the foundation, preventing them from being transmitted to the core measurement components. Simultaneously, the electromagnetic eddy current effect generated by the levitation magnetic array and the copper annular damping wall provides a reverse damping force for the probe, rapidly attenuating and limiting the physical sway of the probe to a low-frequency range. This dual passive stabilization mechanism of high-frequency air-bearing isolation and low-frequency electromagnetic damping solves the problem of traditional contact measurement being susceptible to environmental interference, providing a highly stable original observation platform for laser scanners and inertial measurement units, and ensuring the signal-to-noise ratio of the measurement data from a physical perspective. 2. This invention eliminates the cumbersome process of precision mechanical leveling required by traditional measuring equipment. It utilizes a high-frequency inertial measurement unit to capture the probe's attitude in real time and constructs an absolute coordinate system based on the gravity vector. By calculating the instantaneous deflection relationship of the scanning plane of the rotating laser scanner, the system can perform attitude correction and elevation restoration of the original polar coordinate data in real time during the dynamic process of the probe's slight swaying or tilting. This algorithm-based soft compensation mechanism allows the instrument to complete high-precision operations without being in an absolutely static state, greatly reducing the dependence on the stability of the measurement environment and improving the adaptability and efficiency of on-site operations. 3. To address the non-gravitational acceleration interference generated during probe oscillation, this invention introduces a physical arm length parameter and uses an algorithm to accurately calculate the instantaneous centripetal and tangential accelerations caused by probe oscillation. During the data processing stage, the system removes these dynamic components from the raw observation data of the inertial measurement unit, thereby extracting a pure gravitational acceleration vector for attitude calculation. Combined with the correction of vertical component errors for the horizontal arm length and tilt angle, this method effectively eliminates system errors introduced by sensor installation position and dynamic oscillation, ensuring micron-level restoration accuracy in foundation flatness assessment. 4. This invention adopts a pendulum spindle design with a lowered center of gravity, utilizing physical gravity to achieve natural reset and passive self-stabilization of the probe. The structure is simple and does not require a complex motor drive mechanism, reducing the failure rate. At the same time, with the adaptive static zero-point calibration strategy, the system can automatically determine the quasi-stationary state by monitoring the variance of the data and dynamically adjust the judgment threshold according to the environmental noise level, thereby accurately calculating the zero bias error of the gyroscope and accelerometer. This hardware and software combination design not only ensures data consistency during long-term operation, but also gives the instrument the ability to quickly enter the optimal working state in construction sites with different vibration intensities. Attached Figure Description

[0014] The present invention will be further explained below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the instrument's overall external structure; Figure 2This is a schematic diagram of the instrument's cross-sectional structure; Figure 3 This is a schematic diagram of the connection structure between the self-stabilizing levitation probe and the sensing component; Figure 4 This is a schematic diagram of the process flow of the method of the present invention.

[0015] In the figure: 100, disturbance isolation base; 110, support shell; 120, annular damping wall; 130, limit protection platform; 200, self-stabilizing levitation probe; 210, pendulum spindle; 220, levitation magnetic array; 230, spherical air bearing pair; 300, sensing component; 310, rotating laser scanner; 320, high-frequency inertial measurement unit. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. Example 1

[0017] Please see Figure 1-4 A method for laser measurement of stable foundation flatness, comprising: S1. A disturbance isolation base 100, a self-stabilizing levitation probe 200, and a sensing component 300 are provided. The self-stabilizing levitation probe 200 is movably supported inside the disturbance isolation base 100 by a spherical air bearing pair 230. A levitation magnetic array 220 is provided at the lower part of the self-stabilizing levitation probe 200. A non-contact magnetic orientation limiting unit 240 is provided between the disturbance isolation base 100 and the self-stabilizing levitation probe 200 to provide torsional stiffness around the vertical axis. The sensing component 300 is rigidly fixed to the top of the self-stabilizing levitation probe 200. S2. Start the air source connected to the disturbance isolation base 100 to form an air film between the spherical air bearing pairs 230 to isolate high-frequency vibration. Utilize the electromagnetic eddy current effect between the levitation magnetic array 220 and the annular damping wall 120 to generate a reverse damping force. At the same time, use the magnetic spring restoring torque generated by the magnetic azimuth limiting unit 240 to counteract the reaction torque generated by the rotation of the rotating laser scanner 310, thereby attenuating and limiting the physical sway of the self-stabilizing levitation probe 200 to the low-frequency range and keeping the azimuth angle in a quasi-static state. S3. Start the operation of the sensing component 300, which includes a rotating laser scanner 310 and a high-frequency inertial measurement unit 320. The rotating laser scanner 310 acquires the original polar coordinate data of the ground surface, and the high-frequency inertial measurement unit 320 captures the attitude data of the self-stabilizing levitation probe 200. S4. Stop data acquisition, construct an absolute coordinate system with the gravity vector as the axis based on the attitude data, calculate the instantaneous deflection relationship of the scanning plane of the rotating laser scanner 310 and restore the elevation of the original polar coordinate data, and fit the least squares plane to evaluate the flatness of the foundation.

[0018] To address the problem that existing foundation flatness measurements are easily affected by vibrations from heavy machinery at construction sites, leading to instability of the reference surface, a measurement logic based on a combination of physical isolation and digital compensation is proposed. The disturbance isolation base 100 serves as the basic support architecture of the entire system, and the physical environment constructed inside it provides a prerequisite for high-precision measurement. The self-stabilizing suspended probe 200 utilizes the low-friction characteristics of the spherical air bearing pair 230 to achieve physical contact decoupling inside the disturbance isolation base 100. When there is high-frequency vibration in the external foundation, the air film shear stiffness of the spherical air bearing pair 230 is extremely low, making it difficult for the high-frequency angular vibration and horizontal shear displacement of the base to be transmitted to the probe. This effectively decouples the influence of foundation tilt on the probe attitude and realizes the first level of physical filtering. The combination of the levitation magnetic array 220 and the annular damping wall 120 solves the problem of slow convergence of low-frequency swaying caused by insufficient damping in the simple air-bearing support system. When the self-stabilizing levitation probe 200 oscillates at low frequency, the magnetic lines of force cut the copper wall to generate eddy currents, generating a force that hinders relative motion, thereby rapidly attenuating the kinetic energy of the probe and keeping it in a quasi-vertical state. The sensing component 300 operates in this stable environment. The rotating laser scanner 310, for example, uses an industrial-grade lidar from Velodyne or Hokuyo series to collect spatial geometric data, while the high-frequency inertial measurement unit 320, for example, uses a high-precision microelectromechanical system inertial measurement unit from ADI or Murata to synchronously record the minute attitude changes remaining on the probe. During the data processing stage, the system abandons the traditional approach of using the physical base plane as a reference benchmark and instead utilizes the constancy of the gravity vector. By calculating the tilt relationship of the probe relative to the absolute gravity vertical through attitude data, the unstable scanning plane is projected onto the absolute horizontal coordinate system, thereby restoring the true undulation of the foundation surface. This method can reduce the impact of environmental vibration on the flatness assessment results from the source.

[0019] The steps preceding S3 include: Static zero-point calibration is performed, and the data variance of the high-frequency inertial measurement unit 320 is monitored. When the data variance is lower than the set threshold for a continuous period of time, it is determined to be in a quasi-stationary state. If the variance cannot meet the threshold condition within a preset time, the threshold is automatically increased by a preset step size. If the threshold is increased to the preset maximum safety threshold upper limit and still cannot meet the condition, an environmental abnormality alarm is output and the measurement task is stopped. Alternatively, after user confirmation, the data segment with the smallest variance in the current time period is used to calculate the mean of the gyroscope and accelerometer data as the zero bias error and stored.

[0020] As a sensitive microelectromechanical system, the high-frequency inertial measurement unit 320 has a zero-point drift characteristic that varies with temperature or start-up time, which directly affects the accuracy of subsequent attitude calculation. Before the high-frequency inertial measurement unit 320 is put into operation, a relatively static reference state needs to be confirmed. By continuously monitoring the statistical characteristics of the output data, namely the variance value, it can be determined whether the self-stabilizing levitation probe 200 has achieved mechanical equilibrium through physical damping. When the data variance meets the quasi-stationary condition, the system assumes that the non-zero value output by the sensor is mainly composed of the zero bias error of the device itself; collect the gyroscope angular velocity data and accelerometer force data during this period, extract the constant error component through arithmetic average calculation and store it; In subsequent dynamic measurement processes, the real-time acquired data will be subtracted from the stored zero-bias error, thereby eliminating the inherent systematic bias of the sensor, ensuring the quality of the initial data for attitude calculation, and providing a reliable data foundation for constructing an accurate absolute coordinate system.

[0021] Step S4 involves restoring the elevation of the original polar coordinate data, including: Read the pre-stored physical arm length parameter L from the center of the spherical air bearing pair 230 of the self-stabilizing levitation probe 200 to the center of inertia of the high-frequency inertial measurement unit 320; Based on the angular velocity and angular acceleration data of the high-frequency inertial measurement unit 320, combined with the physical arm length parameter, the instantaneous centripetal acceleration and instantaneous tangential acceleration generated by the swing of the self-stabilizing levitation probe 200 are calculated. Instantaneous centripetal acceleration and instantaneous tangential acceleration are removed from the raw observation data of the high-frequency inertial measurement unit 320, and the gravitational acceleration vector is extracted to correct the attitude data.

[0022] During the micro-oscillation process, the self-stabilized levitation probe 200 does not rotate around the center of the high-frequency inertial measurement unit 320, but rather around the center of the spherical air bearing assembly 230 below. In this calculation model, the center of the spherical air bearing assembly 230 is set as the kinematically absolutely fixed point. Since the air film thickness of the air bearing is only on the micrometer level and its stiffness is extremely high, the translational displacement caused by the change in air film thickness is ignored, and the motion of the probe is strictly regarded as a fixed-point rotation around the center of the sphere. This structural characteristic causes the acceleration sensed by the sensor to include not only the gravitational component, but also the inertial acceleration caused by the motion. The physical arm length parameter calibrates the spatial distance between the rotation center and the measurement center, and is a key geometric constraint for kinematic decoupling; The angular velocity data output by the high-frequency inertial measurement unit 320 reflects the rotation speed of the probe. Differentiating it yields the angular acceleration data. Using the principle of rigid body kinematics, the square of the angular velocity multiplied by the physical arm length parameter yields the instantaneous centripetal acceleration generated by the probe rotation. At the same time, the angular acceleration multiplied by the physical arm length parameter yields the instantaneous tangential acceleration generated by the probe's variable speed oscillation. The raw observation data of the accelerometer of the high-frequency inertial measurement unit 320 includes the projection of gravitational acceleration in the sensor coordinate system, as well as the aforementioned motion acceleration; in order to obtain the pure gravity vector direction as an absolutely perpendicular reference, the calculated instantaneous centripetal acceleration and instantaneous tangential acceleration must be subtracted from the raw observation data. After the above decoupling process, the system can separate the acceleration component caused solely by gravity. This component is then used in conjunction with the Kalman filter algorithm to correct the attitude angle. The specific filtering logic is as follows: Independent filtering models are established for the X and Y axes respectively. For any single axis, a state vector is established. ,in, This is the true tilt angle. Establish dynamic zero bias for the gyroscope; establish observation vector ,in, The tilt angle is calculated from the gravitational acceleration components; the observation equation is established. Among them, the observation matrix , To observe noise; During the time update phase, the prior tilt angle for the next moment is calculated using gyroscope integration. Simultaneously predict the prior error covariance matrix. The formula is Where A is the state transition matrix, defined as , Where is the sampling time interval, and Q is the process noise covariance matrix; During the measurement update phase, the tilt angle calculated using the accelerometer is... The prior estimates are corrected by calculating the Kalman gain. The calculation formula is: ,in To observe noise The covariance, i.e., the variance of accelerometer measurement noise, is used to update the state estimate. ; In the state transition equation, the angle at the next time step is obtained by expanding the state transition matrix A. The calculation logic is as follows: ;

[0023] in, The angular velocity measured by the gyroscope. The sampling time interval is defined as follows: This iterative process utilizes both the high-frequency dynamic response of the gyroscope and the long-term stability of the gravity vector to suppress drift; it eliminates the interference of dynamic oscillation on the determination of the horizontal reference and ensures the accuracy of the construction of the virtual horizontal plane in dynamic environments.

[0024] In step S1, the self-stabilizing levitation probe 200 includes a pendulum spindle 210 and a high-density counterweight module disposed at the bottom of the pendulum spindle 210. The overall center of gravity of the pendulum spindle 210 is located below the rotation center of the spherical air bearing pair 230. The sensing component 300, the levitation magnetic array 220, the rotating end of the spherical air bearing pair 230 and the high-density counterweight module are distributed from top to bottom along the axial direction of the pendulum spindle 210.

[0025] The pendulum spindle 210 serves as the core carrier, and its physical design directly determines the system's resetting capability. The pendulum spindle 210 adopts a design with a lowered center of gravity by adding a high-density counterweight module at the bottom, ensuring that the overall center of gravity of the self-stabilizing suspended probe 200 is always located below the vertical line of the center of the spherical air bearing pair 230, making it mechanically equivalent to a physical pendulum; under the action of gravity, when the air bearing eliminates the frictional torque, this structure has the physical characteristic of naturally finding and pointing towards the center of the earth, providing the instrument with automatic leveling capability without the need for electric drive; The sensing component 300 is located at the top, which facilitates obtaining a wide scanning field of view; the rotating end of the spherical air bearing pair 230 is located in the middle, serving as the fulcrum for the entire swing motion; the levitation magnetic array 220 is located at the bottom, using a long lever arm to amplify the effect of the damping torque; this axial distribution structure optimizes the dynamic response of the system, enabling the probe to quickly return to steady state after being disturbed by relying on the gravity recovery torque and the electromagnetic damping torque at the bottom.

[0026] In step S1, the annular damping wall 120 is made of copper with a wall thickness of 5 mm. The levitation magnetic array 220 includes eight neodymium iron boron strong magnets uniformly embedded in the circumference. The magnetic orientation limiting unit 240 includes a radially magnetized magnet disposed on the pendulum main shaft 210 and a fixed magnetic pole disposed on the inner wall of the support housing 110. The two are arranged in opposite polarities to form a non-contact magnetic orientation recovery structure.

[0027] The annular damping wall 120 is made of copper, which has extremely high electrical conductivity, a prerequisite for achieving efficient electromagnetic induction. The 5 mm wall thickness design ensures structural strength while providing sufficient conductor volume for induced eddy current flow, avoiding insufficient eddy current loss due to excessive resistance. The eight neodymium iron boron strong magnets in the levitation magnetic array 220 provide a high-intensity constant magnetic field; when the levitation magnetic array 220 moves relative to the stationary annular damping wall 120 as the probe swings, the high-intensity magnetic lines of force cross the good conductor copper wall. According to Lenz's law, an induced current, i.e., an eddy current, will be generated inside the annular damping wall 120. The magnetic field of the eddy current is opposite to the direction of change of the original magnetic field, thus generating a viscous resistance. The magnitude of this resistance is directly proportional to the relative motion speed, i.e., the faster the swing, the greater the resistance. When the probe is stationary, the resistance disappears. This non-contact speed proportional damping mechanism can dissipate the mechanical vibration energy of the system very quickly without introducing solid friction.

[0028] In step S4, for each sampling point, the horizontal arm length of the sampling point relative to the center of the probe is calculated based on the current scanning angle and distance. The horizontal arm length is multiplied by the sine of the projection tilt angle of the self-stabilized suspended probe 200 in the current scanning azimuth direction to obtain the vertical component error, which is then subtracted from the preliminary elevation data.

[0029] When the rotating laser scanner 310 is scanning, due to the slight wobbling of the probe itself, the laser beam emitted by it does not rotate strictly on the horizontal plane, which causes the elevation data of the measurement point to be mixed with the instrument's own attitude error. For any laser sampling point, the system calculates the projected length of the point in the horizontal direction from the center of the instrument, i.e., the horizontal arm length, by using its polar coordinate distance and the current scanning angle. When the self-stabilizing suspended probe 200 has a tilt angle, the length of the horizontal arm will amplify the elevation deviation caused by the tilt, just like a lever. The product of the length of the horizontal arm and the sine of the tilt angle quantifies the false displacement of the measurement point in the vertical direction caused by the instrument tilt, i.e., the vertical component error. During the data restoration phase, the system subtracts the vertical component error from the original converted Cartesian coordinate system elevation data. By performing this geometric correction on tens of thousands of point cloud data, the influence of instrument attitude changes on topographic measurement can be isolated. If more rigorous three-dimensional spatial correction is required, the above subtraction correction can be replaced by coordinate rotation transformation. Let the coordinates of a point acquired by the rotating laser scanner 310 in the instrument coordinate system be... ; Roll angle obtained from attitude calculation and pitch angle Construct rotation matrix Corrected absolute coordinates The calculation logic is as follows: ;

[0030] Wherein, rotation matrix Composed of rotational components about the X and Y axes, it can be expressed as follows under small-angle approximation conditions: ; By performing inverse matrix transformation, the local coordinates that move with the probe are projected onto an absolute coordinate system perpendicular to gravity, thus restoring the true unevenness of the foundation surface and ensuring the objectivity of the flatness assessment index.

[0031] In step S1, the disturbance isolation base 100 includes a support housing 110, and a transverse bearing partition is provided inside the support housing 110. The stationary end of the spherical air bearing pair 230 is embedded in the center of the transverse bearing partition.

[0032] The supporting shell 110 forms the external skeleton of the instrument, serving as a protective and load-bearing structure; The transverse load-bearing baffle is not only a reinforcing rib to enhance the rigidity of the shell, but also the installation benchmark for precision air flotation components; The stationary end of the spherical air bearing assembly 230, i.e. the ball socket, is firmly embedded in the center of the partition plate, capable of bearing the entire load from above. This embedded structural design ensures a rigid connection between the air bearing center and the base, allowing the leveling action at the bottom of the base to be accurately transmitted to the air bearing support surface, while also providing a solid foundation for the arrangement of the internal air passages. Through this structural layout, it is ensured that the core air bearing support system can obtain stable mechanical support in complex construction environments, maintaining the normal formation of the micron-level air film. Example 2

[0033] Please see Figure 1-3 A stable foundation flatness laser measuring instrument, comprising: The disturbance isolation base 100 has a supporting shell 110 and an annular damping wall 120 disposed on the inner wall. The self-stabilizing levitation probe 200 is suspended and supported inside the support housing 110 by a spherical air bearing pair 230. The lower end of the self-stabilizing levitation probe 200 is provided with a levitation magnetic array 220 that cooperates with the annular damping wall 120. The sensing component 300 is coaxially rigidly mounted on top of the self-stabilizing levitation probe 200, and includes a rotating laser scanner 310 and a high-frequency inertial measurement unit 320 located directly below the optical rotation center of the rotating laser scanner 310.

[0034] The device integrates mechanical vibration isolation and precision measurement functions; The disturbance isolation base 100, through its rigid structure and the conductive properties of the annular damping wall 120, constitutes a stationary reference frame and an energy dissipator; an external air source, such as a portable high-pressure nitrogen cylinder or a small silent air compressor, is connected to the base through a preset air path to provide fluid power for the system operation. The self-stabilizing levitation probe 200 achieves frictionless levitation using a spherical air bearing pair 230. This bearing pair can be made of porous graphite or a metal air bearing with a specific throttling orifice design to ensure the homogenization effect of the air film. The non-contact engagement between the levitation magnetic array 220 and the damping wall enables the probe to obtain viscous damping characteristics similar to those of a liquid in the levitation state. The rotating laser scanner 310 in the sensing component 300 is responsible for acquiring the environmental profile. Its data transmission is sent to an external host computer through a wireless module such as Wi-Fi 6 or a dedicated data transmission radio integrated inside the self-stabilizing levitation probe 200. The high-frequency inertial measurement unit 320 IMU is installed close to the laser emission center to minimize the measurement error caused by the lever arm effect. The system also includes a controller, such as an embedded microcontroller or FPGA chip based on an ARM Cortex-M7 core, which is responsible for synchronously acquiring laser and IMU data. Considering that the sampling frequency of the rotating laser scanner 310 is usually 10-20Hz and that of the inertial measurement unit is usually greater than 200Hz, the controller uses timestamp alignment and linear interpolation to fuse the data. The timing of the measurement beam emitted by the lidar Using this as a reference, find two adjacent moments in the time series data of the inertial measurement unit. and satisfy Linear interpolation is performed on the attitude data at these two moments to calculate the time. The corresponding instantaneous attitude ensures that the time synchronization accuracy of geometric correction is better than 1 millisecond; and the above-mentioned kinematic decoupling and Kalman filtering algorithm are executed; through the integration of this hardware architecture, the device can independently complete the high-precision flatness measurement task on vibrating foundations without the need for traditional expensive active vibration isolation tables.

[0035] The top of the support housing 110 is provided with a limiting protective platform 130. The limiting protective platform 130 has a central opening with an inner diameter smaller than the maximum diameter of the self-stabilizing levitation probe 200, which is used to mechanically limit the self-stabilizing levitation probe 200.

[0036] The self-stabilizing levitation probe 200 relies solely on the air film and gravity to maintain balance during operation, which is a non-rigid connection state. The limit protection platform 130, as a safety protection mechanism, is installed at the top of the support housing 110; the size of its central opening is precisely calculated to allow the probe to swing freely within the normal working range, for example, within ±5 degrees, without interference. When the device tipps over during transport, or encounters an extreme impact exceeding the air-bearing capacity at the measurement site, the swing amplitude of the self-stabilizing suspended probe 200 will exceed the normal range; at this time, the outer wall of the probe will directly contact the inner edge of the limiting and protective platform 130. This mechanical contact limits further tilting or disengagement of the probe, preventing damage to the precision spherical air bearing assembly 230 due to excessive misalignment, and also avoiding damage to the expensive sensing component 300 from drops, thus improving the robustness and safety of the device in field applications.

[0037] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method of stable laser surveying of ground planarity, characterized in that, The method comprises the following steps: S1, a disturbance isolation base (100), a self-stable suspension probe (200) and a sensing assembly (300) are arranged, wherein the self-stable suspension probe (200) is movably supported in the disturbance isolation base (100) by a spherical air bearing pair (230), a suspension magnetic array (220) is arranged on a swing main shaft (210) of the self-stable suspension probe (200), an annular damping wall (120) is arranged on an inner wall of the disturbance isolation base (100), a non-contact magnetic azimuth limiting unit (240) is arranged between the disturbance isolation base (100) and the self-stable suspension probe (200) to provide torsional stiffness around the vertical axis, and the sensing assembly (300) is rigidly connected to the top of the self-stable suspension probe (200); S2, a gas source connected to the disturbance isolation base (100) is started to form a gas film between the spherical air bearing pair (230) to isolate high-frequency vibration, reverse damping force is generated by electromagnetic eddy current effect between the suspension magnetic array (220) and the annular damping wall (120), and a magnetic spring restoring torque generated by the magnetic azimuth limiting unit (240) is used to offset the reaction torque generated by the rotation of the rotary laser scanner (310), so that the physical shaking of the self-stable suspension probe (200) is attenuated and limited in a low-frequency range and the azimuth angle is kept in a quasi-static state; S3, the sensing assembly (300) is started to work, wherein the sensing assembly (300) comprises a rotary laser scanner (310) and a high-frequency inertial measurement unit (320), the rotary laser scanner (310) acquires original polar coordinate data of the ground surface, and the high-frequency inertial measurement unit (320) captures attitude data of the self-stable suspension probe (200); S4, stopping collecting, constructing an absolute coordinate system with the gravity vector as the axis based on the attitude data, calculating the instantaneous deflection relationship of the scanning plane of the rotary laser scanner (310) and restoring the original polar coordinate data in height, and fitting a least square plane to evaluate the flatness of the foundation.

2. The method of claim 1, wherein, The step S3 further comprises the following steps: static zero position calibration is performed, the data variance of the high-frequency inertial measurement unit (320) is monitored, when the data variance is lower than a set threshold value for a continuous period of time, it is determined that the state is quasi-static, if the threshold value cannot meet the threshold condition within a preset time, the threshold value is automatically increased by a preset step, if the threshold value is increased to a preset maximum safe threshold upper limit and still cannot meet the condition, an environmental abnormality alarm is output and the measurement task is stopped, or the section data with the smallest variance in the current period is used to calculate the mean value of the gyroscope and accelerometer data as the zero bias error for storage after the user confirms.

3. The method of claim 1, wherein, In the step S4, the original polar coordinate data is restored in height, which comprises the following steps: a physical arm length parameter L of the spherical center of the spherical air bearing pair (230) of the self-stable suspension probe (200) to the inertial center of the high-frequency inertial measurement unit (320) is read; based on the angular velocity and angular acceleration data of the high-frequency inertial measurement unit (320) and in combination with the physical arm length parameter, instantaneous centripetal acceleration and instantaneous tangential acceleration generated by the swing of the self-stable suspension probe (200) are calculated. The instantaneous centripetal acceleration and the instantaneous tangential acceleration are removed from the raw observation data of the high-frequency inertial measurement unit (320) to extract a gravity acceleration vector to correct the attitude data.

4. The method of claim 3, wherein the method further comprises: In the step S1, the self-stable suspension probe (200) includes a pendulum main shaft (210) and a high-density counterweight module arranged at the bottom end of the pendulum main shaft (210), the overall gravity center of the pendulum main shaft (210) is located below the rotation center of the spherical air bearing pair (230), the sensing assembly (300), the suspension magnetic array (220), the rotating end of the spherical air bearing pair (230) and the high-density counterweight module are sequentially distributed from top to bottom along the axial direction of the pendulum main shaft (210).

5. The method of claim 3, wherein the method further comprises: In the step S1, the annular damping wall (120) is made of red copper and has a wall thickness of 5 mm, and the suspension magnetic array (220) includes eight pieces of neodymium-iron-boron strong magnets uniformly embedded in the circumferential direction; the magnetic azimuth limiting unit (240) includes a diametrically magnetized magnet arranged on the pendulum main shaft (210) and a fixed magnetic pole arranged on the inner wall of the support shell (110), and the two are arranged in opposite poles to form a non-contact magnetic azimuth recovery structure.

6. The method of claim 3, wherein the method further comprises: In the step S4, for each sampling point, the horizontal arm length of the sampling point relative to the probe center is calculated according to the current scanning angle and distance, the horizontal arm length is multiplied by the sine value of the projection inclination angle of the self-stable suspension probe (200) in the current scanning azimuth angle direction to obtain the vertical component error and subtract it from the preliminary elevation data.

7. The method of claim 3, wherein the method further comprises: In the step S1, the disturbance isolation base (100) includes a support shell (110), and a transverse bearing partition plate is arranged inside the support shell (110), and the stationary end of the spherical air bearing pair (230) is embedded in the center of the transverse bearing partition plate.

8. A stable ground plane laser leveling instrument for use in a stable ground plane laser leveling method according to any one of claims 1 to 7, characterized in that, It comprises: a disturbance isolation base (100) having a support shell (110) and an annular damping wall (120) arranged on the inner wall; a self-stable suspension probe (200) suspended and supported inside the support shell (110) by a spherical air bearing pair (230), the self-stable suspension probe (200) being provided at the lower end with a suspension magnetic array (220) cooperating with the annular damping wall (120); a sensing assembly (300) coaxially rigidly mounted on the top of the self-stable suspension probe (200) and comprising a rotary laser scanner (310) and a high-frequency inertial measurement unit (320) located directly below the optical rotation center of the rotary laser scanner (310).

9. A stable grade planeness laser measuring instrument according to claim 8, characterized in that The support shell (110) is provided at the top with a limiting protection table (130) having a central hole and an inner hole diameter smaller than the maximum diameter of the self-stable suspension probe (200) for mechanically limiting the self-stable suspension probe (200).

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