Fabricated LiDAR corner reflector of multi-reflecting-surface structure and positioning method of fabricated LiDAR corner reflector

Abstract

The invention belongs to the technical field of deformation monitoring and positioning, and particularly relates to an assembled LiDAR corner reflector of a multi-reflecting-surface structure and a positioning method of the assembled LiDAR corner reflector. The corner reflector comprises a hexagonal top plate, six trapezoidal side plates and a supporting piece, the top edges of the six trapezoidal side plates are connected with one edge of the hexagonal top plate respectively, and the six trapezoidal side plates are connected with one another to form a semi-sphere-like shell; the hexagonal top plate and the six trapezoidal side plates are provided with reflectors and ventilation drainage holes; the hemisphere-like shell is fixed on the supporting piece; according to the invention, the coordinate information of the same position of the target object can be acquired from multiple angles while the high-reflection signal of the corner reflector is acquired from multiple angles, and the corner reflector is adaptive to a mainstream deformation monitoring triangular bracket, is high in universality, is convenient to operate and install, can save the cost, and has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of deformation monitoring and positioning, and particularly relates to an assembled LiDAR corner reflector with a multi-reflecting surface structure and a positioning method thereof. Background Art

[0002] In the field of 3D laser scanning, based on different mounting media, 3D laser scanners can be divided into ground-fixed (TLS), airborne, shipborne, handheld, vehicle-mounted, etc., which are used for data collection between different fields.

[0003] In terms of space, the different acquisition methods between instruments are reflected in their different acquisition angles. For example, when collecting point cloud data on a dangerous rock mass, airborne LiDAR can acquire point cloud data from the top or trailing edge of the rock mass from a top-down perspective. Using TLS, with multiple nodes deployed, can acquire point cloud data from the side of the rock mass from a back-to-front perspective on the same horizontal plane. In terms of time, when different media devices collect data on a single object at different times, it is difficult to ensure that the angles of the data collected over multiple periods are completely consistent.

[0004] For data at different angles, in order to achieve data fitting between different angles, the current solution is to align multi-source data or single-source multi-period data based on a common feature point. However, if the collected data has no feature points or the feature points are not obvious, it will increase the difficulty of subsequent data processing. Therefore, manual intervention is required to provide object feature points by adding targets.

[0005] Currently, mainstream targets have two main functions: first, they provide feature points to facilitate the registration of different point cloud data; second, they provide coordinate information for converting point cloud data from relative to absolute coordinates, or for comparing changes in object position information, such as for deformation monitoring.

[0006] However, in the actual acquisition process, on the one hand, the targets that can achieve effective echo signals from multiple angles are generally three-dimensional, making it difficult to ensure the coordinates of the feature points obtained at different angles are consistent. On the other hand, the targets that can guarantee consistent coordinate calculations are generally flat and regular, making it difficult to ensure effective echoes of laser pulse signals from multiple angles.

[0007] In summary, there is an urgent need for a corner reflector that can enable different laser monitoring equipment to collect effective echo signals of the target at different angles, and the echo signal data collected each time can be accurately calculated to obtain the unique position coordinates of the center of the target base. Summary of the Invention

[0008] In response to the shortcomings of the existing technology, the present invention proposes an assembled LiDAR corner reflector with a multi-reflective surface structure and a positioning method thereof. The corner reflector includes: a hexagonal top plate, six trapezoidal side plates and a support member; the top edges of the six trapezoidal side plates are respectively connected to one side of the hexagonal top plate, and the six trapezoidal side plates are connected to each other to form a hemispherical shell; the hexagonal top plate and the six trapezoidal side plates are all provided with reflective sheets and ventilation and drainage holes; the hemispherical shell is fixed on the support member.

[0009] Preferably, the reflective sheets are circular reflective sheets, and each reflective sheet is located at the center of the board surface.

[0010] Preferably, there are 6 ventilation and drainage holes provided on the hexagonal top plate, and 4 ventilation and drainage holes provided on the trapezoidal side plates, which are arranged symmetrically in a ring shape around the circular reflector.

[0011] Preferably, the hexagonal top plate and the six trapezoidal side plates each form an angle of 135°.

[0012] Preferably, the distance between opposite sides of the hexagonal top plate is equal to the height of the trapezoid on the surface of the trapezoidal side plate.

[0013] Preferably, the support member includes a main rod, a connecting member and a plurality of side rods; the main rod connects the hexagonal top plate and the connecting member, and each side rod connects a trapezoidal side plate and the connecting member.

[0014] Furthermore, the connecting member is provided with a plurality of side rod connecting tubes and a main rod connecting tube, the main rod connecting tubes cooperate with the main rod, and the number of the side rod connecting tubes is the same as the number of the side rods and cooperates with the side rods.

[0015] Preferably, the assembled LiDAR corner reflector with a multi-reflecting surface structure further includes a base, the upper portion of the base is connected to the support member, and the lower portion of the base is provided with a threaded hole, which is adapted to fit the surveying tripod bracket.

[0016] A positioning method for an assembled LiDAR corner reflector with a multi-reflecting surface structure, comprising:

[0017] Multiple circular reflectors in the corner reflector can effectively reflect laser pulse signals;

[0018] Collecting laser pulse signals and obtaining the center coordinates of at least three circular reflectors according to the laser pulse signals;

[0019] Use the center coordinates of the circular reflector to calculate the center coordinates of the corner reflector base.

[0020] Furthermore, the formula for calculating the coordinates of the center position of the corner reflector base is:

[0021]

[0022] Among them, (x0, y0, z0) is the coordinate of the center position of the corner reflector base; (x i ,y i ,z i ) is the center coordinate of the i-th circular reflector point cloud.

[0023] The beneficial effects of the present invention are:

[0024] 1. Based on the "6+1" hemispherical shell structure, it can form three or more effective reflective surfaces at different angles above the corner reflector, thereby ensuring that when the airborne LiDAR equipment collects data, it can collect effective corner reflector reflection signals from different angles, significantly improving the data collection efficiency of the airborne LiDAR.

[0025] 2. After collecting reflection signals from at least three circular reflectors on the corner reflector, the coordinates of the center of the corner reflector can be calculated based on the coordinates of the center of any three of the reflectors. If more than three circular reflectors are used, redundant data is used to perform coordinate calculations based on least squares, ensuring the accuracy of the same position coordinate information collected from multiple angles.

[0026] 3. The corner reflector's multi-faceted design is an assembled structure, effectively reducing costs and significantly improving its transportability. It is also compatible with mainstream surveying and mapping tripods, offering high versatility and ease of installation, effectively saving costs.

[0027] 4. Circularly symmetrical ventilation and drainage holes are designed on each side of the corner reflector, effectively enhancing its suitability in field environments. Specifically, these holes effectively reduce the wind resistance of the corner reflector, improving its stability in strong winds. In rainy conditions, the holes also effectively improve the drainage efficiency of the corner reflector's reflective surface structures, preventing water accumulation on the reflective surface from weakening the laser pulse signal reflection intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a front view of the assembled LiDAR corner reflector of the present invention;

[0029] Figure 2 A top view of the assembled LiDAR corner reflector of the present invention;

[0030] Figure 3 A side view of the assembled LiDAR corner reflector of the present invention;

[0031] Figure 4 This is an axonometric view of the assembled LiDAR corner reflector of the present invention;

[0032] Figure 5Schematic diagram of the connection between the assembled LiDAR corner reflector and the tripod in the present invention;

[0033] Figure 6 Schematic diagram of the point cloud positions of the assembled LiDAR corner reflector and circular reflector in the present invention.

[0034] Figure 7 Schematic diagram of the coordinates of the center of the circular reflector and the center point of the corner reflector base in the present invention. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] The present invention proposes an assembled LiDAR corner reflector with a multi-reflecting surface structure and a positioning method thereof. Figure 1 As shown, the corner reflector includes: a hexagonal top plate, six trapezoidal side plates and a support member; the top edges of the six trapezoidal side plates are respectively connected to one side of the hexagonal top plate, and the six trapezoidal side plates are connected to each other to form a hemispherical shell; the hexagonal top plate and the six trapezoidal side plates are all provided with reflective sheets; the hemispherical shell is fixed on the support member.

[0037] In some preferred embodiments of the present invention, Figure 2 As shown, the reflectors are circular, with each reflector located at the center of the panel. The hexagonal top panel forms a 135° angle with each of the six trapezoidal side panels. Preferably, the hexagonal top panel and the trapezoidal side panels are connected by conventional 135° angle brackets. This creates a spherical structure, ensuring that the 3D laser scanner can capture valid reflected signals from the corner reflectors from all angles when collecting data.

[0038] In some preferred embodiments of the present invention, the distance between opposite sides of the hexagonal top plate is equal to the height of the trapezoids on the trapezoidal side plates. This ensures that the center of each circular reflector installed on each surface is the same distance from the center of the hemispherical structure. This facilitates the calculation of the coordinates of the center of the hemispherical structure when the coordinates of the centers of three or more circular reflectors are known.

[0039] In some preferred embodiments of the present invention, Figure 3 、 Figure 4As shown, the support member includes a main rod, a connector, and multiple side rods. The main rod connects the hexagonal top plate to the connector, while each side rod connects a trapezoidal side plate to the connector. Preferably, there are three side rods. The connector is equipped with multiple side rod connecting tubes and a main rod connecting tube, which mate with the main rod. The number of side rod connecting tubes is the same as the number of side rods and mates with the side rods. This structure ensures the stability of the corner reflector, making it suitable for use in extreme weather conditions, and it is easy to install and disassemble.

[0040] In some preferred embodiments of the present invention, Figure 4 、 Figure 5 As shown, the corner reflector also includes a base, the upper part of the base is connected to the support, and the lower part of the base is provided with a threaded hole, which is suitable for mainstream surveying and mapping tripod brackets for easy installation and use.

[0041] In some preferred embodiments of the present invention, Figure 1 、 Figure 2 As shown, each panel of the corner reflector also includes ventilation and drainage holes arranged symmetrically in a ring shape, which can improve the adaptability of the corner reflector under strong winds and rain conditions and ensure the stable operation of the corner reflector under extreme weather conditions.

[0042] The above design ensures that the corner reflector can collect high-reflection signals from multiple angles and obtain the coordinate information of the same position of the corner reflector from different angles.

[0043] The present invention also provides a positioning method for an assembled LiDAR corner reflector based on a multi-reflecting surface structure, comprising:

[0044] The corner reflector has multiple circular reflectors that receive the laser pulse signal emitted by the 3D laser scanner. Specifically:

[0045] The 3D laser scanner obtains the laser signal reflected by the corner reflector and saves it as point cloud data;

[0046] Based on the characteristic that the reflectivity of corner reflectors to laser pulse signals is generally greater than that of other surface objects, the point cloud data is segmented according to the reflectivity values. Only the point cloud sets of multi-faceted circular reflectors are segmented, and point cloud sets of three to seven circular reflectors can be collected at the same time. Circular reflectors can obtain high-density laser data, and the centroid of the laser point cloud coincides with its geometric center point. Figure 6 As shown in the figure, the red dot represents the laser point cloud, and the black dot represents the geometric center of the circular reflector. Based on this, the centroid coordinates of the point cloud are calculated, which are equivalent to the coordinates of the geometric center of the circular reflector. The calculation formula is as follows:

[0047]

[0048] Among them, (x i ,yi ,z i ) is the centroid coordinate of the circular reflector point cloud, that is, the center position coordinate, N is the number of circular reflector point clouds, (x j ,y j ,z j ) is the coordinate of a laser point in the circular reflector.

[0049] The center coordinates of the corner reflector base can be calculated using the center coordinates of the circular reflector. The position relationship is as follows: Figure 7 As shown, specifically:

[0050] Substitute the coordinates of the centers of all circular reflectors obtained in the corner reflector into the sphere solution formula:

[0051] (x i -x0) 2 +(y i -y0) 2 +(z i -z0) 2 =R 2

[0052] Among them, (x0, y0, z0) is the coordinate of the center of the sphere to be determined, that is, the coordinate of the center position of the target, (x i ,y i ,z i ) are the solved coordinates of the center of the circular reflector.

[0053] The above formula can be transformed into:

[0054]

[0055] Construct a system of equations to solve for the center of the sphere:

[0056]

[0057] Based on the least squares method, the above equation is transformed into a matrix equation:

[0058]

[0059] In short:

[0060] AX=B

[0061] Among them, A is the coefficient matrix, X is B is a constant vector.

[0062] The deformation can be obtained:

[0063] X=(A T A) -1 A T B

[0064] Solving the first three components of X can obtain the coordinates of the center position of the corner reflector base (x0, y0, z0).

[0065] The corner reflector designed by the present invention adopts a "6+1" structure, which is composed of a hexagonal top plate and six trapezoidal side plates to form a hemispherical shell structure. The top plate and the side plates form an angle of 135°, which ensures that at least three or more panels can be observed from each angle above the corner reflector. A circular reflector is attached to the middle of the panel surface, so that the three-dimensional laser scanner can obtain the reflection signals of three or more circular reflectors from each angle. By calculating the center point coordinates of the multi-faceted circular reflector point cloud, the center point coordinates of the hemispherical structure base are solved based on the least squares method, thereby achieving the purpose of obtaining the coordinate information of the same position from multiple angles; the present invention solves the problem that when the airborne LiDAR collects data on the target, it is impossible to obtain the effective reflection signal of the traditional target due to the large observation angle. And by optimizing the design of the multi-reflecting surface structure, the problem of large observation accuracy error of the traditional target due to the single reflecting surface signal is solved. The prefabricated structural design solves the problems of high production cost and difficult transportation and installation of traditional targets. The design of annular symmetrical ventilation and drainage holes solves the problem of traditional targets instability induced by wind resistance and weakened laser pulse signal reflection intensity caused by water accumulation in extreme weather conditions.

[0066] The above embodiments further illustrate the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above embodiments are only preferred implementation plans of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An assembled LiDAR corner reflector with a multi-reflection surface structure, characterized in that: include: A hexagonal top plate, six trapezoidal side plates and a support member; the top edges of the six trapezoidal side plates are respectively connected to one side of the hexagonal top plate, and the six trapezoidal side plates are connected to each other to form a hemispherical shell; the hexagonal top plate and the six trapezoidal side plates are all provided with reflective sheets and ventilation and drainage holes; the hemispherical shell is fixed on the support member.

2. The assembled LiDAR corner reflector with a multi-reflection surface structure according to claim 1, characterized in that: The reflective sheets are circular reflective sheets, and each reflective sheet is located at the center of the board surface.

3. The assembled LiDAR corner reflector with a multi-reflecting surface structure according to claim 1, characterized in that: There are 6 ventilation and drainage holes on the hexagonal top plate and 4 ventilation and drainage holes on the trapezoidal side plates, all of which are arranged symmetrically in a ring around the circular reflector.

4. The assembled LiDAR corner reflector with a multi-reflection surface structure according to claim 1, characterized in that: The hexagonal top plate and each of the six trapezoidal side plates form an angle of 135 degrees.

5. The assembled LiDAR corner reflector with a multi-reflection surface structure according to claim 1, characterized in that: The distance between opposite sides of the hexagonal top plate is equal to the height of the trapezoid on the surface of the trapezoidal side plate.

6. The assembled LiDAR corner reflector with a multi-reflection surface structure according to claim 1, characterized in that: The support member includes a main rod, a connecting member and a plurality of side rods; the main rod connects the hexagonal top plate and the connecting member, and each side rod connects a trapezoidal side plate and the connecting member.

7. The assembled LiDAR corner reflector with a multi-reflection surface structure according to claim 6, characterized in that: The connecting piece is provided with a plurality of side rod connecting tubes and a main rod connecting tube, the main rod connecting tubes cooperate with the main rod, and the number of the side rod connecting tubes is the same as the number of the side rods and cooperates with the side rods.

8. The assembled LiDAR corner reflector with a multi-reflection surface structure according to claim 1, characterized in that: It also includes a base, the upper part of the base is connected to the support, and the lower part of the base is provided with a threaded hole, which is suitable for the surveying and mapping tripod bracket.

9. A positioning method for an assembled LiDAR corner reflector based on the multi-reflection surface structure according to any one of claims 1 to 8, characterized in that: include: The multiple circular reflectors of the corner reflector reflect the laser pulse signal; Collecting laser pulse signals and obtaining the center coordinates of at least three circular reflectors according to the laser pulse signals; Use the center coordinates of the circular reflector to calculate the center coordinates of the corner reflector base.

10. The positioning method of the assembled LiDAR corner reflector with a multi-reflection surface structure according to claim 9, characterized in that: The formula for calculating the center coordinates of the corner reflector base is: Among them, (x0, y0, z0) is the coordinate of the center position of the corner reflector base; (x i ,y i ,z i ) is the center coordinate of the i-th circular reflector.

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