阅读说明：本技术 一种基于mems的三维智能土体位移监测装置及方法 (Three-dimensional intelligent soil displacement monitoring device and method based on MEMS ) 是由 吴迪 王金晨 蔺文博 娄万鹏 吴远斌 程峰 黄宇 唐咸远 杨柏 杨彦鑫 于 2021-03-10 设计创作，主要内容包括：本发明公开了一种基于MEMS的三维智能土体位移监测装置及方法,该装置包括数据采集服务器、测斜管、设在测斜管内的N级监测杆、通过固定安装支架锚固在在每级监测杆内部下端的MEMS姿态角度传感器,各MEMS姿态角度传感器通过多级联连接线串联,顶部的MEMS姿态角度传感器通过多级联连接线与USB扩展器连接,USB扩展器通过数据线与数据采集服务器连接；监测杆外的圆周上均匀设有4个水平的伸缩滑动机构。将监测杆分为若干段,并对每一分段建立三维立体坐标系,结合原监测分段位置和MEMS姿态角度传感器获得塌陷后各个监测分段的形变数据,计算得出各个监测分段三维位移,实现对岩溶地区的大范围深层水平位移监测,弥补了对土体内部形变监测的非线性监测需求。(The invention discloses a three-dimensional intelligent soil displacement monitoring device and a method based on MEMS, the device comprises a data acquisition server, an inclinometer pipe, N-level monitoring rods arranged in the inclinometer pipe, and MEMS attitude angle sensors anchored at the lower end in each level of monitoring rods through a fixed mounting bracket, wherein each MEMS attitude angle sensor is connected in series through a multi-cascade connecting wire, the MEMS attitude angle sensor at the top is connected with a USB expander through the multi-cascade connecting wire, and the USB expander is connected with the data acquisition server through a data wire; the circumference outside the monitoring rod is evenly provided with 4 horizontal telescopic sliding mechanisms. The monitoring rod is divided into a plurality of sections, a three-dimensional coordinate system is established for each section, deformation data of each monitoring section after collapse is obtained by combining an original monitoring section position and an MEMS attitude angle sensor, three-dimensional displacement of each monitoring section is obtained through calculation, large-range deep horizontal displacement monitoring of a karst area is achieved, and the nonlinear monitoring requirement for monitoring deformation inside a soil body is met.)

1. A three-dimensional intelligent soil displacement monitoring device based on MEMS is characterized by comprising a data acquisition server, an inclinometer tube vertically embedded in a fourth series covering layer of a point to be monitored, N-stage monitoring rods sequentially connected in series in the inclinometer tube through a connecting assembly, and a fixed mounting bracket fixedly mounted at the lower end in each stage of monitoring rod, wherein MEMS attitude angle sensors are anchored on the fixed mounting bracket and connected in series through a multi-cascade connecting wire;

the circumference outside the monitoring rod is evenly provided with 4 horizontal telescopic sliding mechanisms.

2. The MEMS-based three-dimensional intelligent soil displacement monitoring device of claim 1, wherein each MEMS attitude angle sensor is provided with a unique ID number, and the address of each ID number corresponds to the embedded position depth of the MEMS attitude angle sensor.

3. The MEMS-based three-dimensional intelligent soil displacement monitoring device according to claim 1, wherein the telescopic sliding mechanism comprises a spring, a moving block, a telescopic rod and a pulley, the telescopic direction of the spring is perpendicular to the axial direction of the monitoring rod, the spring is wrapped by a detachable shell, one end of the spring is fixed on the outer surface of the monitoring rod, the other end of the spring is connected with one end of the moving block, the other end of the moving block is connected with one end of the telescopic rod, and the other end of the telescopic rod is connected with the pulley.

4. The MEMS-based three-dimensional intelligent soil displacement monitoring device according to claim 1, wherein the fixed mounting bracket comprises a support frame and a support plate, the lower end of the support frame is fixed at the bottom in the monitoring rod, the support plate is fixed at the upper end of the support frame through a transverse nut, and the MEMS attitude angle sensor is fixed on the support plate through a vertical nut.

5. The MEMS-based three-dimensional intelligent soil displacement monitoring device of claim 1, wherein the top of the monitoring rod at the topmost level is provided with a frame slot for storing a plurality of cascading lines of a certain length.

6. A deep soil displacement monitoring method is characterized by comprising the following steps:

1) dividing N-level monitoring rods buried in a fourth series covering layer of a point to be monitored into N monitoring sections, setting the distance between adjacent sections as a fixed value M, setting the bottom end of the monitoring rod at the bottommost section as an original point (0, 0, 0), and establishing a three-dimensional coordinate system, wherein the three-dimensional space coordinate at the top end of each section is (0, 0, iM), and i is a positive integer value which is greater than 1 and smaller than N in N;

2) the method comprises the following steps that an MEMS attitude angle sensor in a monitoring rod monitors deformation data in deep soil in real time, the deformation data are transmitted to a data acquisition server through a multi-cascade connection line, when karst collapse occurs, the monitoring rod of each monitoring segment displaces in a three-dimensional space along with the soil, whether the monitoring rod displacing in the soil is in a standing state or not is judged through acceleration and an attitude angle acquired by the MEMS attitude angle sensor, calculation is started from the monitoring rod at the lowest stage in the non-standing state, and the three-dimensional space coordinate of the monitoring rod at the upper stage is calculated;

3) when the monitoring rod moves, the displacement of the i-level monitoring rod at the bottom in the movement is set to be L, the displacement of the MEMS attitude angle sensor is also set to be L, the displacement L is calculated through secondary integration in a frequency domain, the XY axial angle beta 1 of the i-level monitoring rod at the bottom is obtained according to an electronic compass in the MEMS attitude angle sensor, the L and the beta 1 are used for obtaining the three-dimensional space coordinate of the top end of the monitoring rod at the bottom according to a displacement calculation formula, and therefore the deep displacement of the monitoring rod at the bottom is obtained, and a three-dimensional view is formed;

4) by adopting the method of the step 3), obtaining displacement-time images of the monitoring sections according to the three-dimensional space coordinates of the top end of the first-level i-level monitoring rod in the motion and the three-dimensional space coordinates of the bottom end of the first-level i + 1-level monitoring rod and the time output by the MEMS attitude angle sensor, and calculating from the displacement-time images to the top of the monitoring rod; judging and early warning the soil body displacement by the displacement-time image of the monitoring segment; and meanwhile, the data acquisition server generates a monitoring report according to the deformation data transmitted by the MEMS attitude angle sensor, wherein the monitoring report comprises the triaxial displacement change, the depth displacement direction, the estimated collapse soil cave width, the soil cave forming rate and the soil cave forming direction of each monitoring section.

7. The method of claim 6, wherein the three-dimensional coordinate system is a northeast three-dimensional rectangular coordinate system.

8. The deep soil displacement monitoring method according to claim 6, wherein the deformation data includes roll angle, pitch angle, course angle, acceleration, deformation time, angular velocity, sensor inclination, monitoring rod displacement, and inclination of the monitoring rod in the XY axis plane.

9. A deep soil displacement monitoring method according to claim 6 wherein the monitoring sections are each 0.3 to 3m in length.

10. The deep soil displacement monitoring method according to claim 6, wherein a three-axis accelerometer inside the MEMS attitude angle sensor respectively acquires X, Y, Z three axial accelerations, a three-axis gyroscope inside the MEMS attitude angle sensor acquires angular velocities to obtain an attitude angle, the attitude angle is subjected to MATLAB attitude matrix transformation, and finally the acceleration is subjected to data processing by using a central computer to obtain an inclination angle and a displacement of the sensor at a generated position, specifically as follows:

i, displacement calculation

I-1) calculating an attitude angle: setting angular velocity vectors of 3 square axes of the MEMS gyroscope sensor as w in a navigation coordinate system relative to a geographic coordinate system_tb＝[ψ，γ，θ]^TThen its projection under the navigation coordinate system is:

in the above-mentioned formula (1),respectively representing the angular velocity of X, Y, Z axial directions, and psi, gamma and theta are respectively a heading angle, a roll angle and a pitch angle; substituting psi, gamma and theta in the formula (1) into a four-element method to carry out coordinate transformation;

i-2) four-element method calculation: converting a navigation coordinate system into a geographic coordinate system by a four-element method, then substituting psi, gamma and theta into a composite matrix of the object rotating around three rotating shafts to obtain a Q1 matrix, wherein Q is an orthogonal matrix Q1-Q because a rectangular coordinate system is always kept in the rotation process from the geographic coordinate system to the object coordinate system^TAccording to the angular velocity transmitted by the gyroscope in real time, real-time vector and scalar parameters of four elements can be calculated, and further the real-time attitude angle of the sensor can be calculated;

Q＝λ+P₁i+P₂j+P₃k (2)

in formula (2): λ is a four-element scalar portion; p is a four-element vector part, wherein a scalar part refers to a rotation angle cosine value, and a vector part refers to the direction of the rotating shaft, the rotating shaft and the cosine value in an instantaneous state;

will be provided withSubstituting the formula (2) to obtain:

wherein in formula (3): alpha is the angle of rotation from the b system (carrier coordinate system) to the t system (geographical coordinate system), L_x、m_y、n_zAre all direction cosine values between the rotation axis n and the reference coordinate system axis, the four-element Q describes the angular velocity of the b system of the carrier relative to the t system, and is considered to be formed by one equivalent rotation of the carrier from the b system to the t system, and Q contains all information of this rotation, due to the formula (4):

the normalized four elements are found to be:

i-3) quadratic integration in the frequency domain: the MEMS attitude angle sensor transmits signals acquired by an internal accelerometer and attitude information acquired by an internal gyroscope to a navigation computer through an RS232 interface, uses MATLAB to program, and performs secondary integration on acceleration signals for monitoring the movement track of karst collapse, specifically as follows:

firstly, when an acquired signal is integrated in a frequency domain, discrete Fourier transform and inverse discrete Fourier transform are carried out, acceleration signals are acquired according to time and then Fourier transform is carried out, and the following results are obtained:

one of the sections is set asWhere A is the amplitude, ω is the angular velocity, t is time, and the velocity integral equation is:

the displacement integral formula is:

II, calculating the inclination angle: calculating the inclination angle of the sensor according to an inclination angle measurement principle formula, wherein the method specifically comprises the following steps:

a set of coordinate systems [ X ]₁、Y₁、Z₁]^TThe wire is inclined around the Y axis at an inclination angle theta_yAt an angle of inclination theta about the X axis_xThe coordinate system after twice inclination is [ x, y, z ]]^T，

Is provided with [ X ]₁、Y₁、Z₁]^T＝[0、0、1]^TObtaining by solution:

[ theta ] in formula (12)'_x、θ′_yIs [ x, y, z ]]^T＝[0、0、1]^TIs the angle of inclination of rotation about axis X, Y;

the sensor tilt angle is then:

III, judging the standing state: and (3) judging the state of the monitoring rod moving at the bottom stage, and reducing the error caused by time accumulation in the monitoring process of the sensor, wherein the comprehensive speed of the MEMS is obtained by frequency domain integration in the step I-3, and the attitude change angular speed of the MEMS is obtained in the step I-1, and the judgment is as follows:

1. the MEMS integrated velocity v (t) is less than the threshold value v_S；

2. The angular transformation speed of the MEMS attitude change is less than a certain threshold value w_s；

When the monitoring rod in the lowest stage of movement is less than v_S、w_sWhen the monitoring rod is not moved, v_SAnd w_sThe value of (a) depends on the navigation system parameters carried on the MEMS;

and IV, obtaining included angles between the carrier and the east, west, south and north directions by combining a magnetometer in the MEMS attitude angle sensor according to the displacement obtained in the step I and the inclination angle obtained in the step II, and calculating three-dimensional space displacement coordinate values of the change points of the monitoring rod, wherein the method specifically comprises the following steps: in the established three-dimensional stereo coordinate system, the change point B projects a point B on a three-dimensional plane from the positive direction of the Y axis, namely from the east to the origin O₁By rotating B from CB to B₁I.e. CB₁＝M，CB＝CB₁Expressed as B (0, 0, 2M), B using three-dimensional coordinates₁(X，Y，Z)，B₁The three-dimensional space coordinate calculation process is as follows:

subtracting equation (15) from equation (14):

at this time B₁In the XCY planeProjection of

Angle beta obtained from magnetometer₁The substitution then has:

Y＝Sinβ₁N

X＝Cosβ₁N

then B is₁Three-dimensional space coordinate representation as

Then CB₁Displacement in the X-axis direction is Cos beta₁N, is displaced by Sin beta in the Y-axis direction₁N, is displaced in the Z-axis direction by

And in the depth range of the monitoring hole, obtaining the three-dimensional space coordinates of all the change points through iterative calculation from bottom to top by the three-dimensional model.

Technical Field

The invention relates to the technical field of karst collapse geological disaster prevention, in particular to a three-dimensional intelligent karst collapse monitoring device and method based on MEMS.

Background

The collapse accidents frequently occurring in recent years attract wide social attention, the urban collapse occurs in the regions with concentrated population, and seriously threatens the safety of lives and properties, urban construction and economic development, and the types of the urban collapse include: karst collapse, mining collapse, subway collapse and the like, and for major collapse-prone areas and the peripheries of major projects of karst areas, a proper method is necessary for long-term real-time monitoring, early warning and the like of karst collapse.

The monitoring method of karst collapse can be classified into a direct monitoring method and an indirect monitoring method. The direct monitoring method is a method for judging the ground subsidence by directly monitoring the deformation of the underground soil body, the indirect monitoring method is mainly used for monitoring the dynamic change of the water-air pressure in the karst pipeline system, and the direct monitoring method is used for monitoring and early warning the karst subsidence. As the building foundation in the karst area, the karst collapse prone area and other occasions needing monitoring need to be monitored, the foundation is monitored. The key and difficult point in the field of karst collapse direct monitoring at present lies in deformation monitoring occurring in the soil body, and there are three monitoring modes for soil body deformation monitoring, one is distributed optical fiber sensing technology (BOTDR) based on brillouin scattering, the other is time domain reflection Technology (TDR) which utilizes the variation analysis of the shearing force or tension applied to the local impedance of the electromagnetic wave in the coaxial cable transmission process, and the last is geological radar technology (GPR) which utilizes the ultrahigh frequency electromagnetic wave to detect the distribution of the underground medium, and at present, the devices are mainly applied to linear engineering, such as roads, railways and the like, and have some problems mainly:

firstly, the BOTDR optical fiber sensing technology has high requirements on equipment, optical fibers need to be laid, and in addition, the temperature has great influence on the optical fibers, and a large number of simulation test tests need to be carried out.

And secondly, the TDR time domain reflection technology generates cable signals only under the condition that the TDR cable deforms under the combined action of shearing force, tension or the shearing force and the tension, and the size of the displacement of the mutation point cannot be obtained.

And thirdly, the GPR geological radar technology has large interference of electromagnetic waves around a field on the resolution ratio, limited depth and incapability of realizing real-time monitoring and remote sensing, and has large limitation as a long-term monitoring means because traffic needs to be sealed when the technology is implemented in a road operation stage.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides a three-dimensional intelligent soil displacement monitoring device and method based on MEMS (micro-electromechanical systems), which can realize real-time automatic monitoring and draw a three-dimensional view of a deep soil, are suitable for nonlinear engineering, and are convenient to carry and install.

The technical scheme for realizing the purpose of the invention is as follows:

a three-dimensional intelligent soil displacement monitoring device based on MEMS comprises a data acquisition server, an inclinometer tube vertically embedded in a fourth series covering layer of a point to be monitored, N-stage monitoring rods sequentially connected in series in the inclinometer tube through a connecting assembly, and a fixed mounting bracket fixedly mounted at the lower end in each stage of monitoring rod, wherein MEMS attitude angle sensors are anchored on the fixed mounting bracket and connected in series through a multi-cascade connecting wire, the MEMS attitude angle sensor at the top is connected with a USB expander through the multi-cascade connecting wire, and the USB expander is connected with the data acquisition server through a data line;

according to the MEMS attitude angle sensor, each MEMS attitude angle sensor is provided with a unique ID number, and the address of each ID number corresponds to the position depth embedded in the MEMS attitude angle sensor.

The circumference outside the monitoring rod is evenly provided with 4 horizontal telescopic sliding mechanisms, so that the monitoring rod is always positioned at the central position of the inclinometer pipe in the installation and use processes, the monitoring rod is ensured not to deflect and twist in the inclinometer pipe, and the accuracy of soil displacement detection data is improved.

The telescopic sliding mechanism comprises a spring, a moving block, a telescopic rod and a pulley, wherein the telescopic direction of the spring is vertical to the axial direction of the monitoring rod, the spring is wrapped by a detachable shell, one end of the spring is fixed on the outer surface of the monitoring rod, the other end of the spring is connected with one end of the moving block, the other end of the moving block is connected with one end of the telescopic rod, and the other end of the telescopic rod is connected with the pulley.

The fixed mounting support comprises a support frame and a support plate, wherein the lower end of the support frame is fixed at the bottom in the monitoring rod, the support plate is fixed at the upper end of the support frame through a transverse nut, and the MEMS attitude angle sensor is fixed on the support plate through a vertical nut.

The monitoring rod, the top in the monitoring rod of top one-level is equipped with the frame groove for store certain length's many cascade connection line.

A deep soil displacement monitoring method is applied to the three-dimensional intelligent soil displacement monitoring device, and comprises the following steps:

1) dividing N-level monitoring rods buried in a fourth series covering layer of a point to be monitored into N monitoring sections, setting the distance between adjacent sections as a fixed value M, setting the bottom end of the monitoring rod at the bottommost section as an original point (0, 0, 0), and establishing a three-dimensional coordinate system, wherein the three-dimensional space coordinate at the top end of each section is (0, 0, iM), and i is a positive integer value which is greater than 1 and smaller than N in N;

2) the method comprises the following steps that an MEMS attitude angle sensor in a monitoring rod monitors deformation data in deep soil in real time, the deformation data are transmitted to a data acquisition server through a multi-cascade connection line, when karst collapse occurs, the monitoring rod of each monitoring segment displaces in a three-dimensional space along with the soil, whether the monitoring rod displacing in the soil is in a standing state or not is judged through acceleration and an attitude angle acquired by the MEMS attitude angle sensor, calculation is started from the monitoring rod at the lowest stage in the non-standing state, and the three-dimensional space coordinate of the monitoring rod at the upper stage is calculated;

3) when the monitoring rod moves, the displacement of the i-level monitoring rod at the bottom in the movement is set to be L, the displacement of the MEMS attitude angle sensor is also set to be L, the displacement L is calculated through secondary integration in a frequency domain, the XY axial angle beta 1 (figure 8) of the i-level monitoring rod at the bottom is obtained according to an electronic compass in the MEMS attitude angle sensor, the three-dimensional space coordinate of the top end of the i-level monitoring rod at the bottom is obtained by the L and the beta 1 according to a displacement calculation formula, and therefore the deep displacement of the monitoring rod at the bottom is obtained, and a three-dimensional view is formed;

4) by adopting the method of the step 3), obtaining displacement-time images of the monitoring sections according to the three-dimensional space coordinates of the top end of the first-level i-level monitoring rod in the motion and the three-dimensional space coordinates of the bottom end of the first-level i + 1-level monitoring rod and the time output by the MEMS attitude angle sensor, and calculating from the displacement-time images to the top of the monitoring rod; judging and early warning the soil body displacement by the displacement-time image of the monitoring segment; and meanwhile, the data acquisition server generates a monitoring report according to the deformation data transmitted by the MEMS attitude angle sensor, wherein the monitoring report comprises the triaxial displacement change, the depth displacement direction, the estimated collapse soil cave width, the soil cave forming rate and the soil cave forming direction of each monitoring section.

The three-dimensional coordinate system is a north-east-sky three-dimensional rectangular coordinate system.

The deformation data comprises a roll angle, a pitch angle, a course angle, an acceleration, a deformation time, an angular speed, a sensor inclination angle, a monitoring rod displacement and an inclination angle of the monitoring rod on an XY axis plane.

The length of each monitoring segment is 0.3-3 m.

The MEMS attitude angle sensor is characterized in that a three-axis accelerometer inside the MEMS attitude angle sensor respectively acquires X, Y, Z three axial accelerations, a three-axis gyroscope inside the MEMS attitude angle sensor acquires angular velocities to obtain attitude angles, MATLAB (matrix laboratory) is carried out on the attitude angles to carry out attitude matrix transformation, and finally, the acceleration is subjected to data processing by using a central computer to obtain the inclination angle and the displacement of the sensor at the position where the sensor occurs, and the method specifically comprises the following steps:

i, displacement calculation

I-1) calculating an attitude angle: setting angular velocity vectors of 3 square axes of the MEMS gyroscope sensor as w in a navigation coordinate system relative to a geographic coordinate system_tb＝[ψ，γ，θ]^TThen its projection under the navigation coordinate system is:

in the above-mentioned formula (1),respectively representing the angular velocity of X, Y, Z axial directions, and psi, gamma and theta are respectively a heading angle, a roll angle and a pitch angle; substituting psi, gamma and theta in the formula (1) into a four-element method to carry out coordinate transformation;

i-2) four-element method calculation: converting a navigation coordinate system into a geographic coordinate system by a four-element method, then substituting psi, gamma and theta into a composite matrix of the object rotating around three rotating shafts to obtain a Q1 matrix, wherein Q is an orthogonal matrix Q1-Q because a rectangular coordinate system is always kept in the rotation process from the geographic coordinate system to the object coordinate system^TAccording to the angular velocity transmitted by the gyroscope in real time, real-time vector and scalar parameters of four elements can be calculated, and further the real-time attitude angle of the sensor can be calculated;

Q＝λ+P₁i+P₂j+P₃k (2)

in formula (2): λ is a four-element scalar portion; p is a four-element vector part, wherein a scalar part refers to a rotation angle cosine value, and a vector part refers to the direction of the rotating shaft, the rotating shaft and the cosine value in an instantaneous state;

will be provided withSubstituting the formula (2) to obtain:

wherein in formula (3): alpha is the angle of rotation from the b system (carrier coordinate system) to the t system (geographical coordinate system), L_x、m_y、n_zAre all direction cosine values between the rotation axis n and the reference coordinate system axis, the four-element Q describes the angular velocity of the b system of the carrier relative to the t system, and is considered to be formed by one equivalent rotation of the carrier from the b system to the t system, and Q contains all information of this rotation, due to the formula (4):

the normalized four elements are found to be:

i-3) quadratic integration in the frequency domain: the MEMS attitude angle sensor transmits signals acquired by an internal accelerometer and attitude information acquired by an internal gyroscope to a navigation computer through an RS232 interface, uses MATLAB to program, and performs secondary integration on acceleration signals for monitoring the movement track of karst collapse, specifically as follows:

firstly, when an acquired signal is integrated in a frequency domain, discrete Fourier transform and inverse discrete Fourier transform are carried out, acceleration signals are acquired according to time and then Fourier transform is carried out, and the following results are obtained:

one of the sections is set asWhere A is the amplitude, ω is the angular velocity, t is time, and the velocity integral equation is:

the displacement integral formula is:

II, calculating the inclination angle: calculating the inclination angle of the sensor according to an inclination angle measurement principle formula, wherein the method specifically comprises the following steps:

a set of coordinate systems [ X ]₁、Y₁、Z₁]^TThe wire is inclined around the Y axis at an inclination angle theta_yAt an angle of inclination theta about the X axis_xThe coordinate system after twice inclination is [ x, y, z ]]^T，

Is provided with [ X ]₁、Y₁、Z₁]^T＝[0、0、1]^TObtaining by solution:

[ theta ] in formula (12)'_x、θ′_yIs [ x, y, z ]]^T＝[0、0、1]^TIs the angle of inclination of rotation about axis X, Y;

the sensor tilt angle is then:

III, judging the standing state: and (3) judging the state of the monitoring rod moving at the bottom stage, and reducing the error caused by time accumulation in the monitoring process of the sensor, wherein the comprehensive speed of the MEMS is obtained by frequency domain integration in the step I-3, and the attitude change angular speed of the MEMS is obtained in the step I-1, and the judgment is as follows:

1. the MEMS integrated velocity v (t) is less than the threshold value v_S；

2. The angular transformation speed of the MEMS attitude change is less than a certain threshold value w_s；

When the monitoring rod in the lowest stage of movement is less than v_S、w_sWhen the monitoring rod is not moved, v_SAnd w_sThe value of (a) depends on the navigation system parameters carried on the MEMS;

and IV, obtaining included angles between the carrier and the east, west, south and north directions by combining a magnetometer in the MEMS attitude angle sensor according to the displacement obtained in the step I and the inclination angle obtained in the step II, and calculating three-dimensional space displacement coordinate values of the change points of the monitoring rod, wherein the method specifically comprises the following steps: in the established three-dimensional stereo coordinate system, the change point B projects a point B on a three-dimensional plane from the positive direction of the Y axis, namely from the east to the origin O₁By rotating B from CB to B₁I.e. CB₁＝M，CB＝CB₁Expressed as B (0, 0, 2M), B using three-dimensional coordinates₁(X，Y，Z)，B₁The three-dimensional space coordinate calculation process is as follows:

subtracting equation (15) from equation (14):

at this time B₁Projection in the XCY plane

Angle beta obtained from magnetometer₁The substitution (as shown in fig. 8) is:

Y＝Sinβ₁N

X＝Cosβ₁N

then B is₁Three-dimensional space coordinate representation as

Then CB₁Displacement in the X-axis direction is Cos beta₁N, is displaced by Sin beta in the Y-axis direction₁N, is displaced in the Z-axis direction by

And in the depth range of the monitoring hole, obtaining the three-dimensional space coordinates of all the change points through iterative calculation from bottom to top by the three-dimensional model.

Compared with the prior art, the method has the following advantages:

1. the sensor for measuring the inclination angle and the acceleration adopts the MEMS attitude angle sensor, so that the sensor is more intelligent in data acquisition, is simple to bury in a soil body, is low in price and high in precision, and avoids laying an optical cable in a large area and blocking traffic monitoring.

2. The connecting line of the MEMS attitude angle sensor is a multi-cascade connecting line, and can be directly connected to a data acquisition server, so that the continuous acquisition of data is realized, the measurement can be uninterrupted, and the engineering accident caused by intermittent measurement is avoided.

3. According to the deep soil displacement monitoring method, the monitoring rod is divided into a plurality of sections, a three-dimensional stereo coordinate system is established for each section, deformation data of each monitoring section after collapse is obtained by combining the position of the original monitoring section and an MEMS attitude angle sensor, and three-dimensional displacement of each monitoring section is calculated, so that large-range deep horizontal displacement monitoring of a karst area is realized, and the nonlinear monitoring requirement on deformation monitoring inside a soil body is met. In addition, the forming position of the collapsed soil cave can be judged more accurately by analyzing the change of the horizontal displacement of each monitoring section along with time and depth.

4. According to the invention, by arranging a plurality of row monitoring units, the overall situation of the whole monitoring area can be judged; the device can be applied to nonlinear engineering, can carry out three-dimensional monitoring on deep collapse cavities, forms a three-dimensional space view and more comprehensively masters the displacement change of deep soil in a karst collapse area.

5. The invention can utilize the advantages of high measurement precision, good intelligent degree and real-time measurement of the MEMS attitude angle sensor, and realize intelligent and automatic monitoring of the karst collapse area by measuring the three-dimensional inclination angle and displacement change of the deep soil body in the karst area, thereby avoiding the occurrence of karst collapse and having wide engineering application prospect.

Drawings

FIG. 1 is a schematic structural diagram of a three-dimensional intelligent soil displacement monitoring device based on MEMS;

FIG. 2 is a schematic view of the top-most monitoring bar;

FIG. 3 is a top view of FIG. 2;

FIG. 4 is a north-east-sky coordinate system for use with the present invention

FIG. 5 is a schematic view of the method of the present invention

FIG. 6 is a schematic diagram of coordinate system transformation during attitude angle output according to the present invention

FIG. 7 is a schematic diagram of three-dimensional space calculation of a monitoring rod in motion

FIG. 8 is a schematic view of the angles of a gyroscope and magnetometer according to the present invention.

In the figure: the system comprises a USB expander (1), a USB expander (2), a data acquisition server (3), a multi-cascade connecting line (4), a telescopic sliding mechanism (5), a monitoring rod (6), an MEMS attitude angle sensor (7), a fixed mounting bracket (8), a connecting assembly (9), a frame groove (10), a detachable shell (11), a moving block (12), a telescopic rod (13), a pulley (14), a spring (15), a supporting plate (16), a supporting frame (17), a vertical nut (18) and a transverse nut.

Detailed Description

The invention will be further elucidated with reference to the drawings and examples, without however being limited thereto.

Example (b):

as shown in fig. 1, 2 and 3:

a three-dimensional intelligent soil displacement monitoring device based on MEMS comprises a data acquisition server 2, an inclinometer tube vertically embedded in a fourth series covering layer of a point to be monitored, N-stage monitoring rods 5 sequentially connected in series in the inclinometer tube through connecting components 7, and a fixed mounting bracket 7 fixedly mounted at the lower end in each stage of monitoring rod 5, wherein MEMS attitude angle sensors 6 are anchored on the fixed mounting bracket, each MEMS attitude angle sensor 6 is connected in series through a multi-cascade connecting wire 3, the topmost MEMS attitude angle sensor 6 is connected with a USB expander 1 through the multi-cascade connecting wire 3, and the USB expander 1 is connected with the data acquisition server 2 through a data line;

in the MEMS attitude angle sensor 6, each MEMS attitude angle sensor 6 is provided with a unique ID number, and the address of each ID number corresponds to the position depth embedded in the MEMS attitude angle sensor 6.

The circumference outside the monitoring rod 5 is evenly provided with 4 horizontal telescopic sliding mechanisms 4, so that the monitoring rod is always positioned at the central position of the inclinometer pipe in the installation and use processes, the monitoring rod 5 is ensured not to deflect and twist in the inclinometer pipe, and the accuracy of soil displacement detection data is improved.

The telescopic sliding mechanism 4 comprises a spring 14, a moving block 11, a telescopic rod 12 and a pulley 13, wherein the telescopic direction of the spring 14 is vertical to the axial direction of the monitoring rod 5, the spring 14 is wrapped by a detachable shell 10, one end of the spring 14 is fixed on the outer surface of the monitoring rod 5, the other end of the spring is connected with one end of the moving block 11, the other end of the moving block 11 is connected with one end of the telescopic rod 12, and the other end of the telescopic rod 2 is connected with the pulley 13.

The fixed mounting support 4 comprises a support frame 16 and a support plate 15, the lower end of the support frame 16 is fixed at the bottom in the monitoring rod 5, the support plate 15 is fixed at the upper end of the support frame 16 through a transverse nut 18, and the MEMS attitude angle sensor 6 is fixed on the support plate 15 through a vertical nut 17.

The monitoring rod 5, the top in the monitoring rod 5 of the top one-level is equipped with the frame groove 9 for the many cascade connection line of certain length of storage.

In this embodiment:

the monitoring rod can be made of UPVC material, the UPVC has strong corrosion resistance, acid and strong base resistance, can not rust and scale, and has light weight and very convenient installation and construction;

the material of the frame groove can be wood or UPVC;

the material of the support frame and the support plate can be plastic or wood.

A deep soil displacement monitoring method is applied to the three-dimensional intelligent soil displacement monitoring device, and comprises the following steps:

1) dividing N-level monitoring rods buried in a fourth series covering layer of a point to be monitored into N monitoring sections, setting the distance between adjacent sections as a fixed value M, setting the bottom end of the monitoring rod at the bottommost section as an original point (0, 0, 0), and establishing a three-dimensional coordinate system, wherein the three-dimensional space coordinate at the top end of each section is (0, 0, iM), and i is a positive integer value which is greater than 1 and smaller than N in N;

2) the method comprises the following steps that an MEMS attitude angle sensor in a monitoring rod monitors deformation data in deep soil in real time, the deformation data are transmitted to a data acquisition server through a multi-cascade connection line, when karst collapse occurs, the monitoring rod of each monitoring segment displaces in a three-dimensional space along with the soil, whether the monitoring rod displacing in the soil is in a standing state or not is judged through acceleration and an attitude angle acquired by the MEMS attitude angle sensor, calculation is started from the monitoring rod at the lowest stage in the non-standing state, and the three-dimensional space coordinate of the monitoring rod at the upper stage is calculated;

3) when the monitoring rod moves, the displacement of the i-level monitoring rod at the bottom in the movement is set to be L, the displacement of the MEMS attitude angle sensor is also set to be L, the displacement L is calculated through secondary integration in a frequency domain, the XY axial angle beta 1 of the i-level monitoring rod at the bottom is obtained according to an electronic compass in the MEMS attitude angle sensor, the L and the beta 1 are used for obtaining the three-dimensional space coordinate of the top end of the monitoring rod at the bottom according to a displacement calculation formula, and therefore the deep displacement of the monitoring rod at the bottom is obtained, and a three-dimensional view is formed;

4) by adopting the method of the step 3), obtaining displacement-time images of the monitoring sections according to the three-dimensional space coordinates of the top end of the first-level i-level monitoring rod in the motion and the three-dimensional space coordinates of the bottom end of the first-level i + 1-level monitoring rod and the time output by the MEMS attitude angle sensor, and calculating from the displacement-time images to the top of the monitoring rod; judging and early warning the soil body displacement by the displacement-time image of the monitoring segment; and meanwhile, the data acquisition server generates a monitoring report according to the deformation data transmitted by the MEMS attitude angle sensor, wherein the monitoring report comprises the triaxial displacement change, the depth displacement direction, the estimated collapse soil cave width, the soil cave forming rate and the soil cave forming direction of each monitoring section.

The three-dimensional coordinate system is a north-east-sky three-dimensional rectangular coordinate system, as shown in fig. 4; establishing a calculation model by using a three-dimensional rectangular space coordinate system of a northeast sky (t system), wherein O is a coordinate system observation point, a Z axis is a rectangular coordinate system formed by taking the upward direction as the positive direction (the sky direction), a Y axis is the positive direction (the east direction), the X axis is the north direction (the north direction), and the bottom end of a monitoring rod at the bottommost section is set as an origin (0, 0, 0); specifically, when the karst collapse occurs, as shown in fig. 8, the coordinate change of the B point can be regarded as the result of the rotation combination of three, i.e., roll of the B point through an angle Ψ, pitch of an angle γ, and pitch change of an angle θ, the tilt angle of the MEMS gyroscope sensor can be obtained through the three rotation combinations, and the length L between the BBs 1 can be obtained through quadratic integration in the frequency domain, as shown in the following formula (10), and the three-dimensional trajectory of the monitoring rod can be obtained through three-dimensional coordinate calculation.

The deformation data comprises a roll angle, a pitch angle, a course angle, an acceleration, a deformation time, an angular speed, a sensor inclination angle, a monitoring rod displacement and an inclination angle of the monitoring rod on an XY axis plane.

The length of each monitoring segment is 0.3-3 m.

The MEMS attitude angle sensor, whose internal triaxial accelerometer respectively collects X, Y, Z three axial accelerations, and whose internal triaxial gyroscope collects angular velocities to obtain attitude angles, performs MATLAB on the attitude angles to perform attitude matrix transformation, and finally performs data processing on the accelerations by using a central computer to obtain the inclination and displacement of the sensor at the occurring position, as shown in fig. 5, specifically as follows:

i, displacement calculation

I-1) calculating an attitude angle: setting angular velocity vectors of 3 square axes of the MEMS gyroscope sensor as w in a navigation coordinate system relative to a geographic coordinate system_tb＝[ψ，γ，θ]^TThen its projection under the navigation coordinate system is:

in the above-mentioned formula (1),respectively representing the angular velocity of X, Y, Z axial directions, and psi, gamma and theta are respectively a heading angle, a roll angle and a pitch angle; substituting psi, gamma and theta in the formula (1) into a four-element method to carry out coordinate transformation;

i-2) four-element method calculation: converting a navigation coordinate system into a geographic coordinate system by a four-element method, then substituting psi, gamma and theta into a composite matrix of an object rotating around three rotating shafts to obtain a Q1 matrix, wherein Q is an orthogonal moment because a rectangular coordinate system is always kept in the rotation process from the geographic coordinate system to the object coordinate systemQ1 ═ Q^TAccording to the angular velocity transmitted by the gyroscope in real time, real-time vector and scalar parameters of four elements can be calculated, and further the real-time attitude angle of the sensor can be calculated;

Q＝λ+P₁i+P₂j+P₃k (2)

in formula (2): λ is a four-element scalar portion; p is a four-element vector part, wherein a scalar part refers to a rotation angle cosine value, and a vector part refers to the direction of the rotating shaft, the rotating shaft and the cosine value in an instantaneous state;

will be provided withSubstituting the formula (2) to obtain:

wherein in formula (3): α is the angle from b (carrier coordinate system) to t (geographic coordinate system), L is shown in FIG. 6_x、m_y、n_zAre all direction cosine values between the rotation axis n and the reference coordinate system axis, the four-element Q describes the angular velocity of the b system of the carrier relative to the t system, and is considered to be formed by one equivalent rotation of the carrier from the b system to the t system, and Q contains all information of this rotation, due to the formula (4):

the normalized four elements are found to be:

i-3) quadratic integration in the frequency domain: the MEMS attitude angle sensor transmits signals acquired by an internal accelerometer and attitude information acquired by an internal gyroscope to a navigation computer through an RS232 interface, uses MATLAB to program, and performs secondary integration on acceleration signals for monitoring the movement track of karst collapse, specifically as follows:

firstly, when an acquired signal is integrated in a frequency domain, discrete Fourier transform and inverse discrete Fourier transform are carried out, acceleration signals are acquired according to time and then Fourier transform is carried out, and the following results are obtained:

one of the sections is set asWhere A is the amplitude, ω is the angular velocity, t is time, and the velocity integral equation is:

the displacement integral formula is:

II, calculating the inclination angle: calculating the inclination angle of the sensor according to an inclination angle measurement principle formula, wherein the method specifically comprises the following steps:

a set of coordinate systems [ X ]₁、Y₁、Z₁]^TThe wire is inclined around the Y axis at an inclination angle theta_yAt an angle of inclination theta about the X axis_xThe coordinate system after twice inclination is [ x, y, z ]]^T，

Is provided with [ X ]₁、Y₁、Z₁]^T＝[0、0、1]^TObtaining by solution:

[ theta ] in formula (12)'_x、θ′_yIs [ x, y, z ]]^T＝[0、0、1]^TIs the angle of inclination of rotation about axis X, Y;

the sensor tilt angle is then:

III, judging the state of the static base: and (3) judging the state of the detection rod moving at the bottom stage, and reducing the error caused by time accumulation in the monitoring process of the sensor, wherein the MEMS comprehensive speed is obtained by frequency domain integration in the step I-3, and the MEMS attitude change angular speed is obtained in the step I-1, and the judgment is as follows:

1. the MEMS integrated velocity v (t) is less than the threshold value v_S；

2. The angular transformation speed of the MEMS attitude change is less than a certain threshold value w_s；

When the monitoring rod in the lowest stage of movement is less than v_S、w_sWhen the monitoring rod is not moved, v_SAnd w_sThe value of (a) depends on the navigation system parameters carried on the MEMS;

and IV, obtaining included angles between the carrier and the east, west, south and north directions by combining a magnetometer in the MEMS attitude angle sensor according to the displacement obtained in the step I and the inclination angle obtained in the step II, and calculating three-dimensional space displacement coordinate values of the change points of the monitoring rod, wherein the method specifically comprises the following steps: in the established three-dimensional stereo coordinate system, the change point B projects a point B on a three-dimensional plane from the positive direction of the Y axis, namely from the east to the origin O₁By rotating B from CB to B₁I.e. CB₁＝M，CB＝CB₁Expressed as B (0, 0, 2M), B using three-dimensional coordinates₁(X, Y, Z) as shown in FIG. 7, B₁The three-dimensional space coordinate calculation process is as follows:

subtracting equation (15) from equation (14):

at this time B₁Projection in the XCY plane

Angle beta obtained from magnetometer₁The substitution (as shown in fig. 8) is:

Y＝Sinβ₁N

X＝Cosβ₁N

then B is₁Three-dimensional space coordinate representation as

Then CB₁Displacement in the X-axis direction is Cos beta₁N, is displaced by Sin beta in the Y-axis direction₁N, is displaced in the Z-axis direction by

And in the depth range of the monitoring hole, obtaining the three-dimensional space coordinates of all the change points through iterative calculation from bottom to top by the three-dimensional model.

As shown in FIG. 8, since the attitude angle sensors are positioned in one-to-one correspondence when buried, when the monitoring lever is moved to B₁When the displacement of the sensor is set to be L, the calculation of the displacement L can be calculated by the formula (10) through secondary integration in a frequency domain, and the movement of the monitoring rod from B to B can be obtained according to an electronic compass arranged on the monitoring rod₁Angle beta in XY axial direction₁According to the displacement calculation formula, B can be obtained₁From the three-dimensional space coordinates of the monitoring rod to B₁To form a three-dimensional view.

According to B₁The three-dimensional space coordinate is the three-dimensional space coordinate of the upper stage A1 to obtain A₁B₁And the three-dimensional motion track of the monitoring rod is calculated from the three-dimensional motion track to the top of the monitoring rod.

And drawing a three-axis displacement and time curve of each monitoring section according to the three-dimensional space coordinates of each monitoring section, wherein the time can be before the displacement of the monitoring rod is changed violently when the monitoring section sinks, and calculating a monitoring report form, wherein the monitoring report form can comprise three-axis displacement change, depth displacement direction, estimated sinking soil cave width, soil cave forming rate and soil cave forming direction.

According to the deep soil displacement monitoring method, the monitoring rod is divided into a plurality of sections, a three-dimensional stereo coordinate system is established for each section, deformation data of the deep soil is obtained by combining the monitoring rod and the monitoring sections, three-dimensional changes of each monitoring section are obtained through calculation, large-range deep horizontal displacement monitoring of a karst area is achieved, and the nonlinear monitoring requirement for monitoring deformation inside the soil is met. In addition, the forming position of the collapsed soil cave can be judged more accurately by analyzing the change of the displacement of each monitoring section along with the time and the depth.

In engineering implementation, a monitoring rod of the monitoring device is vertically embedded in a monitored foundation, the monitoring rod keeps an upright state, and the value of an MEMS attitude angle sensor is in a zero setting state and keeps upright; as shown in fig. 1-2, when a deep soil body forms a soil cave through erosion, sand particle leakage and weak soil loss, the surrounding monitoring rods are inclined and displaced due to the loss and peeling of the soil body below or nearby, and the internal MEMS attitude angle sensor is changed along with the deflection of the monitoring rods. At the moment, the inclination angle, the acceleration and the serial number are sent to the data acquisition server by the multi-cascade connection line connected with the MEMS attitude angle sensor.

After receiving collapse data sent by the MEMS attitude angle sensor, the server firstly reads the serial number of the MEMS attitude angle sensor to obtain the specific position of a monitoring place, secondly carries out secondary integration by utilizing a frequency domain integration method through the accelerated speed collected by the MEMS attitude angle sensor, and carries out secondary integrationAnd the data can be subjected to noise reduction processing in a time-sharing manner, so that the integration precision is improved. Then, the inclination angle theta of the three-dimensional view of the MEMS sensor and the plane projection inclination angle beta of the magnetometer are used₁And calculating the displacement L to obtain the three-dimensional displacement track of the monitoring rod, forming a 3D visual displacement diagram, and monitoring and early warning the collapse of the karst area visually through the displacement diagram.