WO2021135422A1 - Method for rapidly calculating tilt deformation of circular mast on the basis of laser point cloud - Google Patents

Abstract

A method for rapidly calculating tilt deformation of a circular mast on the basis of a laser point cloud, the method belonging to the technical field of tilt measurement. The method comprises the following steps: I, selecting a reasonable station and scanning angle of a scanning frame; II, performing grid density segmentation to realize automatic extraction of point cloud data of a circular mast; III, automatically capturing thin-layer data at any altitude from the data extracted in step II; IV, removing abnormal points from each thin-layer point cloud ring in the thin-layer data captured in step III to obtain a point cloud ring satisfying a circle equation; V, automatically fitting the center of the point cloud ring, and fitting the center position of a thin layer at any altitude; and VI, calculating offset occurring to a basis reference center obtained in step V, and then rapidly calculating the tilt rate of the circular mast according to a calculation formula. The method has the beneficial effects of being high in calculation speed, and affordable, automatically achieving tilt deformation measurement at any altitude, and being high in precision.

Description

A fast calculation method for tilting deformation of circular pole tower based on laser point cloud Technical field

The invention relates to a method for quickly calculating the tilt deformation of a circular pole tower based on a laser point cloud, and belongs to the technical field of tilt detection.

Background technique

Electricity is an important energy resource in the world, and its power facilities are an important infrastructure in the world. Therefore, the monitoring and maintenance of power facilities is particularly important, especially the inclination and deformation monitoring of power towers, wind turbine towers, etc. The so-called tilt of the tower is the phenomenon that the center of the tower deviates from the plumb weight due to the uneven top surface of the foundation column. When transmission line towers or wind turbines are located in special geological areas such as goafs or landslides, the upper covering rock may cause ground cracks, rock mass dislocation, collapse, and ground collapse due to local environmental or external forces such as gravity, stress and natural forces. And other geological phenomena, and then major safety accidents such as towers or wind turbines twisting, tilting, or even toppling. The inclination of poles and towers is one of the main threats that affect the stable operation of power transmission lines and wind farms. Therefore, the inclination monitoring of power poles and wind turbine towers is an important content of power detection.

The traditional tilt measurement method is the total station measurement or the plane mirror method. These two tilt measurement methods are not accurate enough and not rigorous enough to fully reflect the tilt and deformation of the power tower and the wind turbine tower. The development of terrestrial 3D laser scanning technology has greatly improved the efficiency, accuracy and data volume of data acquisition, which has made a qualitative leap compared with traditional surveying. Using the principle of laser ranging, the distance values of thousands of target points are acquired at one time, and the position and posture of the launch point are determined by auxiliary measuring equipment, and then the three-dimensional coordinates, reflectivity and texture of the target point are obtained to construct High-precision, high-resolution ground model and real three-dimensional modeling. Compared with traditional measuring instruments, laser scanning can obtain a large amount of point information, which can better characterize the surface model of the object.

Determining the tilting deformation of the poles and towers is of great significance for maintaining the safety of lines and wind turbines, and is an important technical means to ensure the safety of power facilities operation and maintenance and maintain national energy security.

Summary of the invention

The purpose of the present invention is to provide a method for quickly calculating the tilt deformation of a circular pole tower based on a laser point cloud, which has the effects of fast calculation speed, economical application, automatic realization of tilt deformation measurement at any height, and high accuracy.

In order to achieve the above objective, the technical solution adopted by the present invention is:

A method for quickly calculating the tilt and deformation of a circular tower based on a laser point cloud, including the following steps:

1. Choose a reasonable scanning rack site and scanning angle;

2. Automatically extract point cloud data of circular towers;

3. Automatically intercept thin layer data of any height from the data extracted in step 2;

4. Eliminate the abnormal points of each thin layer point cloud ring in the thin layer data intercepted in step 3, and obtain a point cloud ring that satisfies the circle equation;

5. Automatically fit the center of the point cloud ring to fit the center position of a thin layer of any height;

6. Calculation step 5 After obtaining the offset of the reference datum center, calculate the inclination rate of the circular tower according to the calculation formula of inclination rate ρ=d/h, where d is the offset of the cross section center relative to the reference datum center , H is the height.

The further improvement of the technical scheme of the present invention is that in step one, the scanning rack site is empty and the ground object is single; and the scanning angle is 30 degrees.

The further improvement of the technical scheme of the present invention is that: Step 2: The automatic extraction of point cloud data of the circular pole tower includes the following steps:

① The point cloud is automatically screened and reduced by the position coordinates of the scanning station and the approximate height of the tower. Starting from any point cloud, calculate the distance from the position of the scanning station. If the distance is less than the height of the tower, the point cloud is marked as a useful point , Otherwise it is marked as noise;

② Repeat step ① to traverse the point cloud and extract all the useful point clouds in a small range of the circular tower;

③ Perform grid density segmentation on the point cloud within a small range of the circular tower, and set the grid point cloud threshold at the same time. If the number of points in the grid is greater than the threshold, it will be calibrated as a circular tower point cloud;

④ Repeat step ③ until all round tower point clouds are found, and the round tower point cloud data will be automatically obtained.

The further improvement of the technical scheme of the present invention is that in step 3, the circular point cloud data of the height layer of 2mm thickness is automatically intercepted from the position of the pole tower with a height of 2 meters, and the height of each additional 1 meter is automatically intercepted in turn. Ring point cloud data.

The further improvement of the technical scheme of the present invention lies in that the method used in step 5 to fit the center of the point cloud ring is the least squares algorithm.

The further improvement of the technical scheme of the present invention lies in: Step ③The grid size is 0.1m×0.1m, and the threshold value is set to 100.

Due to the adoption of the above technical scheme, the technical effects achieved by the present invention are as follows:

The scanning rack station of the present invention has an open selection point and a single ground object, and it is easy to obtain the point cloud data of the pole and tower.

The invention automatically screens and reduces the data volume of the point cloud data obtained by scanning, and removes the noise point cloud far away from the tower. The point cloud is automatically filtered through the coordinates of the erection position and the approximate height of the tower, and the point cloud in a small range of the circular tower is extracted, and the redundant noise point cloud is filtered out.

The present invention performs grid density segmentation on the point cloud in a small range of the circular pole tower, considering that the number of projection points of the circular pole tower point cloud on the horizontal plane is large, and there is a big difference with the surrounding point data, and the grid point cloud is set Threshold, if the number of points in the grid is greater than the threshold, it will be calibrated as a circular tower point cloud. Through the grid and the threshold, the point cloud can not be missed, the error is reduced, and the data obtained is reliable.

The invention intercepts the annular point cloud data from the bottom elevation plus a position of 2 meters, and eliminates the influence of the bottom information of the tower.

The invention adopts the principle of least squares to perfectly fit the center position of the cross section at any height, so as to realize the rapid acquisition of the inclination rate of the inclination deformation.

The algorithm of the invention is reliable, the calculation speed is fast, the tilt deformation measurement work at any height can be automatically realized, and the tilt rate measurement accuracy is high, and it is economical and applicable.

Description of the drawings

Figure 1 is the technical route of the present invention;

Fig. 2 is a schematic diagram of the central axis of the cross section of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the drawings and specific embodiments:

Measuring the inclination deformation of the pole and tower is of great significance for maintaining the safety of lines and wind turbine operation, and is an important technical means to ensure the safety of power facility operation and maintenance and maintain energy safety. In this embodiment, the present invention uses Leica ScanStation P50 to complete field point cloud data collection. Leica P50 adopts high-precision angle and distance measurement technology, WFD waveform digitization technology, Mixed Pixels technology and HDR image technology. It has a longer range and more powerful performance. Its scanning effective distance exceeds 500 meters. 360-degree panoramic scanning, the scanning rate is as high as 1,000,000 points/sec. The application of multiple technologies reduces the noise in the scanning range, eliminates the phenomenon of object edge smearing, increases the accuracy of the edge range, widens the scanning range, reduces the number of stations, and meets the needs of large scenes, long distances and various scanning tasks. It can well meet the needs of pole tower tilt measurement.

The invention discloses a method for quickly calculating the tilting deformation of a circular pole tower based on a laser point cloud. As shown in Fig. 1 is the technical route of the invention, which includes the following steps:

1. Choose a reasonable scanning frame site and scanning angle; it is particularly important to select a proper scanning frame station position when performing circular pole tower scanning measurements in the field. The principle of selecting the scanning rack station is that the rack site should be as open as possible, and the ground objects should be as simple as possible, so that the point cloud data of the tower can be easily obtained. The distance between the rack site and the circular tower is generally 1/2 or one time the height of the tower. The scanning angle range can be set to 30 degrees according to the height and distance of the tower, and the reflecting prism is controlled to rotate at a uniform speed; for each circular tower, choose two relative erection positions, and try to use the least amount of point cloud data to achieve the panoramic view of the circular tower Scan to reduce redundant noise data outside the circular tower.

2. Automatically extract point cloud data of circular towers;

First, the point cloud data obtained by scanning is automatically screened and reduced, and the noise point cloud far away from the tower is removed. The point cloud is automatically filtered through the coordinates of the erection position and the approximate height of the tower, and the point cloud in a small range of the circular tower is extracted, and the redundant noise point cloud is filtered out. Then the grid density segmentation is performed on the point cloud in a small area of the circular tower. Considering that the number of projection points of the circular tower point cloud on the horizontal plane is large, and there is a big difference with the surrounding point data, the grid point cloud threshold can be set , If the number of points in the grid is greater than the threshold, it will be calibrated as a circular tower point cloud.

The specific operation steps of step two are as follows:

① The point cloud is automatically screened and reduced by the position coordinates of the scanning station and the approximate height of the tower. Starting from any point cloud, calculate the distance from the position of the scanning station. If the distance is less than the height of the tower, the point cloud is marked as a useful point , Otherwise it is marked as noise;

② Repeat step ① to traverse the point cloud and extract all the useful point clouds in a small range of the circular tower;

③The projection density of the point cloud of the circular tower or wind turbine tower on the horizontal plane is very large, which is quite different from the surrounding points. Combined with the scanning characteristics of P50, the grid density of the point cloud in a small range of the circular tower is divided, and the point cloud is set at the same time. Fixed grid point cloud threshold, if the number of points in the grid is greater than the threshold, it will be calibrated as a circular tower point cloud;

④ Repeat step ③ until all round tower point clouds are found, and the round tower point cloud data will be automatically obtained.

3. Automatically intercept thin layer data of any height from the data extracted in step 2;

For the point cloud data of a circular pole tower or wind turbine tower, first obtain the bottom point cloud elevation information, considering that the base height of the bottom of the pole tower is generally about 1 meter. In order to eliminate the influence of the bottom information of the pole tower, the present invention adds a position of 2 meters from the bottom elevation. According to the tower height value H±1mm of this height, the ring point cloud data of 2mm thickness of the height layer will be automatically intercepted; for each increase in height by 1 meter, the ring point cloud data of the height layer of 2mm thickness will be automatically intercepted in turn.

At the same time, the sampling interval setting can also be adjusted manually according to the inclination of the circular tower and wind turbine tower. When the inclination is serious and complicated, the sampling interval can be set smaller so that the inclination curve can accurately reflect the circular tower and wind turbine tower. The inclination state of the tube, rather than a partial, rough, and incomplete reflection of the inclination state of the tower and wind turbine, cannot fully and accurately reflect the problem.

4. Eliminate the abnormal points of each thin layer point cloud ring in the thin layer data intercepted in step 3, and obtain a point cloud ring that satisfies the circle equation;

The cross section of each height of the circular tower body is a circle. When the scanner obtains the point cloud data of the tower body, the points on the surface of the tower body are scanned as the reflection source, so the cross section of the tower body point cloud is a circle. The present invention first selects three points with a certain interval from each thin layer point cloud ring, and roughly determines the circle equation of the point cloud ring. The points on the point cloud ring should basically satisfy the circle equation, with only a few abnormal points. Not on the circular trajectory. If a point deviates from the circle trajectory, it is calibrated as an abnormal point and eliminated, and a point cloud ring that satisfies the circle equation is obtained.

5. Aiming at the thin point cloud ring after removing the abnormal points, in order to accurately simulate the inclination of the circular tower or wind turbine tower, the least squares algorithm is used to fit the point cloud ring of the circular tower or wind turbine tower. Accurately obtain the center coordinates of each point cloud ring, and obtain the tilt and deformation information of each layer relative to the bottom layer;

The specific approach is as follows:

When fitting the center of the point cloud ring, first assume that these points {(x ₁ , y ₁ ), (x ₂ , y ₂ ),..., (x _i , y _i )} satisfy the equation:

(xx _c ) ² +(yy _c ) ² ＝R ² ①

(X _c , y _c ) are the coordinates of the center of the fitting circle, and R is the radius of the fitting circle (unit: m).

For all points of the data source, the least squares fitting is performed, and the equation is as follows:

_{(X c} , y _c ) when f takes the minimum value is the center coordinate of the fitted thin-layer point cloud, that is, f=min. Make

The establishment of equation ② requires that the three variables _{x c} , y _{c and R satisfy:}

Suppose g(x,y)=(xx _c ) ² +(yy _c ) ² -R ²

by

inferred

∑g(x _i ,y _i )=0, (R≠0)

by

inferred

∑x _i g(x _i ,y _i )=0

by

inferred:

∑y _i g(x _i ,y _i )=0

_{Finally, the coordinates (x c} , y _c ) of the center of the thin layer of the point cloud of the fitting tower are derived:

among them

6. Calculation Step 5 After obtaining the offset of the reference datum center, quickly calculate the inclination rate of the circular pole tower according to the calculation formula.

The inclination rate expresses the relative relationship. In an ideal state, the center of any cross section of the target should form a central axis, as shown in Figure 2. At the same time, a reference datum needs to be set when calculating the inclination rate, in accordance with the "Building Deformation Measurement Code" , When calculating the inclination rate of the tower body, the center of the cross section at the bottom end of the tower body is set as the reference datum, the offset of the center of the cross section of different height h relative to the reference datum center is d, and the inclination rate of this height is :

ρ=d/h Unit: m

The key to calculating the inclination rate of the circular pole tower and the wind turbine tower is to calculate the center position of the cross section at any height. Step 5 of the present invention adopts the principle of least squares to perfectly fit the center position of the cross section at any height, so as to realize the tilt deformation. Obtain the tilt rate quickly.

The algorithm of the present invention is reliable, the calculation speed is fast, can automatically realize the tilt deformation measurement work at any height, and the tilt rate measurement accuracy is high at the same time,

The examples of this specific implementation manner are all preferred examples of the present invention, and do not limit the scope of protection of the present invention accordingly. Therefore: all equivalent changes made in accordance with the structure, shape, principle, etc. of the present invention should be covered Within the protection scope of the present invention.

Claims (6)

1. A method for quickly calculating the tilt deformation of a circular tower based on a laser point cloud, which is characterized in that it includes the following steps:

   1. Choose a reasonable scanning rack site and scanning angle;

   2. Automatically extract point cloud data of circular towers;

   3. Automatically intercept thin layer data of any height from the data extracted in step 2;

   4. Eliminate the abnormal points of each thin layer point cloud ring in the thin layer data intercepted in step 3, and obtain a point cloud ring that satisfies the circle equation;

   5. Automatically fit the center of the point cloud ring to fit the center position of a thin layer of any height;

   6. Calculation step 5 After obtaining the offset of the reference datum center, calculate the inclination rate of the circular tower according to the calculation formula of inclination rate ρ=d/h, where d is the offset of the cross section center relative to the reference datum center , H is the height.
2. The method for quickly calculating the tilt deformation of a circular tower based on a laser point cloud according to claim 1, characterized in that: in step 1, the scanning frame site is empty and the ground object is single; and the scanning angle is 30 degrees.
3. The method for quickly calculating the tilt deformation of a circular tower based on a laser point cloud according to claim 1, characterized in that: Step 2: The automatic extraction of the point cloud data of the circular tower includes the following steps:

   ① The point cloud is automatically screened and reduced by the position coordinates of the scanning station and the approximate height of the tower. Starting from any point cloud, calculate the distance from the position of the scanning station. If the distance is less than the height of the tower, the point cloud is marked as a useful point , Otherwise it is marked as noise;

   ② Repeat step ① to traverse the point cloud and extract all the useful point clouds in a small range of the circular tower;

   ③ Perform grid density segmentation on the point cloud within a small range of the circular tower, and set the grid point cloud threshold at the same time. If the number of points in the grid is greater than the threshold, it will be calibrated as a circular tower point cloud;

   ④ Repeat step ③ until all round tower point clouds are found, and the round tower point cloud data will be automatically obtained.
4. The method for quickly calculating the tilt deformation of a circular tower based on a laser point cloud according to claim 1, characterized in that: in step 3, the ring-shaped point cloud data with a thickness of 2mm in the height layer is automatically intercepted from the position of the tower with a height of 2 meters At the same time, every time the height increases by 1 meter, the ring point cloud data with the thickness of 2mm in the height layer will be automatically intercepted.
5. The method for quickly calculating the tilt deformation of a circular tower based on a laser point cloud according to claim 1, wherein the method used in step 5 to fit the center of the point cloud ring is a least squares algorithm.
6. According to claim 3, a method for quickly calculating the tilt deformation of a circular tower based on a laser point cloud, characterized in that: step ③, the grid size is 0.1m×0.1m, and the threshold is set to 100.

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