Large-scale real-scene 3D modeling system and method in digital twin city construction

Abstract

The present invention provides a large-scale real-scene three-dimensional modeling system and method for digital twin city construction. The unmanned aerial vehicle (UAV) has a built-in positioning module, a communication module, and a processor, and the processor executes instructions sent by a ground control end; a camera is installed at the bottom of the UAV, and a movable assembly structure is adopted between the camera and the UAV; a gear ring structure is arranged at the bottom of the UAV, and the camera is fixed on a camera bracket; the outer end of the camera bracket is equipped with a planetary gear that meshes with the gear ring; a connecting column is provided at the bottom of the UAV, and the inner end of the camera bracket is connected to the connecting column through two upper and lower clockwork springs, and the rotation directions of the two clockwork springs are opposite; the UAV flight route is set, images are captured and corresponding position data are recorded, and the images are sequentially exported based on the position data for feature matching and grayscale matching; a white mold is generated according to the building plane and elevation data, and a three-dimensional model is generated through texture mapping.

Description

Technical Field

[0001] The present invention relates to a surveying and mapping method, and in particular to a large-scale three-dimensional real-scene rapid modeling system and method in a digital twin city. Background Art

[0002] The so-called digital twin city is a complex, massive system that interacts and corresponds with the physical world of the city and the virtual space of the network. This system recreates a matching, corresponding twin city in cyberspace, achieving the digitization and virtualization of all urban elements, the real-time visualization of all urban conditions, and the collaborative and intelligent management and decision-making of urban management. Through the construction of digital twin cities, the intelligent application and visualization of urban big data can be realized, further facilitating the transition from digital cities to smart cities.

[0003] The construction of digital twin cities must address the visualization of spatiotemporal information. Three-dimensional scenes easily immerse viewers. Drone oblique photography modeling technology is a recently developed technology. This technology simultaneously captures images from one vertical, four oblique, and five different perspectives, producing rich, high-resolution textures of building tops and side views. This technology not only accurately reflects the terrain but also generates realistic 3D city models through advanced positioning, fusion, and modeling techniques.

[0004] In existing drone oblique photography, rapid turns by the drone cause the five cameras to rotate synchronously. This rapid, rapid turn of the cameras can blur the captured images. Therefore, a new real-scene 3D modeling system is urgently needed to address the blurring of images captured during rapid drone turns and rapidly build models using these images. This is crucial for accurately representing urban data and accelerating the development of digital twin cities. Summary of the Invention

[0005] Therefore, in order to avoid the problem of five cameras rotating synchronously when the drone turns quickly, the cameras turning at a large angle in a very short time, resulting in the captured images becoming blurred, and to realize real-scene three-dimensional modeling, the present invention designs a large-scale real-scene three-dimensional modeling system and method for digital twin city construction.

[0006] The technical solution adopted by the present invention is: a large-scale real-scene 3D modeling system for digital twin city construction, characterized by:

[0007] Includes drone, internal gear plate, suspension bracket, ball, bearing, planetary gear, top column, camera bracket, camera, and spring.

[0008] A cylindrical connecting column extending vertically downward is provided at the bottom center of the casing of the drone.

[0009] The internal gear disc is an oblate cylinder, and an oblate cylindrical transmission cavity is opened downward on the top surface of the oblate cylinder. A circular center hole is opened at the center of the bottom of the transmission cavity. A gear ring is processed around the central axis of the transmission cavity on the vertical cylindrical surface of the transmission cavity; the internal gear disc is screwed on the center of the bottom of the drone, the top surface of the internal gear disc is close to the bottom surface of the drone casing, and the central axis of the internal gear disc is collinear with the central axis of the connecting column.

[0010] The center of the suspension bracket is a cylinder with an outer diameter smaller than the center hole, which is located in the center hole. The bottom surface of the cylinder is lower than the bottom surface of the inner gear disk. Four threaded columns are evenly distributed on the bottom surface of the cylinder around the center axis of the cylinder. A cylindrical connecting cavity is opened downward on the top surface of the cylinder. The center axis of the connecting cavity and the center axis of the connecting column are collinear, and a gap is left between the connecting column and the bottom surface of the connecting cavity; the outer cylindrical surface of the cylinder is close to the top and three horizontal radial support rods are evenly arranged around the center axis of the cylinder. A ball is embedded in the bottom of the outermost end of the support rod and rolls on the bottom surface of the transmission cavity; a thin cylindrical hinge shaft is provided on the top of the outer end of the support rod, and a bearing is mounted on the hinge shaft. A threaded hole is opened downward on the top surface of the hinge shaft.

[0011] The planetary gears consist of three pieces, which are respectively mounted on three bearings. The planetary gears mesh with the gear teeth on the gear ring of the internal gear plate. The bottom of the top column is screwed into the threaded hole of the hinge shaft to limit the upward movement of the bearing. The top of the top column is embedded with a ball bearing, which rolls on the bottom surface of the drone.

[0012] The top of the camera bracket is a fixing plate with four fixing holes, which are mounted on the threaded columns at the bottom of the suspension bracket and locked with nuts; a vertical cylinder is provided in the center of the bottom surface of the fixing plate, and a horizontal support plate is provided on the bottom end of the vertical cylindrical surface. Four horizontal cylindrical support columns extend outward from the outer cylindrical surface of the vertical cylinder near the bottom end, and the angle between the central axes of adjacent support columns is 90 degrees. The outer end of each support column is provided with a support plate with an angle of 45 degrees to the horizontal plane, and a camera is screwed on the bottom surface of each support plate.

[0013] There are two clockwork springs, which are installed in the connecting cavity of the suspension bracket in sequence. The inner end of the clockwork spring is fixed on the connecting column of the drone, and the outer end is fixed on the inner cylindrical surface of the connecting cavity. One of the clockwork springs rotates clockwise and the other rotates counterclockwise.

[0014] A large-scale real-scene 3D modeling method for digital twin city construction, characterized by:

[0015] Step 1: The drone has a built-in positioning module, communication module, and processor, and the processor executes commands sent by the ground control end. A camera is installed on the bottom of the drone, and a movable assembly structure is used between the camera and the drone. A gear ring structure is arranged on the bottom of the drone, and the camera is fixed to the camera bracket. The outer end of the camera bracket is equipped with a planetary gear that meshes with the gear ring. A connecting column is provided at the bottom of the drone, and the inner end of the camera bracket is connected to the connecting column via two upper and lower springs. The inner end of the spring is fixed to the connecting column, and the outer end is fixed to the inner end of the camera bracket. The two springs rotate in opposite directions.

[0016] Step 2: Set the flight route of the drone. The flight route is set to fly only along the longitude and latitude lines. That is, when the drone flies along the longitude line, the longitude does not change, and when the drone flies along the latitude line, the latitude does not change.

[0017] Step 3: Capture the image and record the corresponding position data. Based on the position data, the image is exported in sequence for feature matching and grayscale matching.

[0018] Step 4: Generate a white model based on the building plan and elevation data and perform an accuracy check , where E is the error, n is the number of monitoring points, and △i is the difference between two measurement points at the same location;

[0019] Step 5: Generate a 3D model through texture mapping.

[0020] The principle of the present invention is as follows: a structure in which the planetary gear and the gear ring of the internal gear plate are meshed is adopted, so that the rotation process of the camera bracket must rely on the meshing transmission of the planetary gear and the gear ring, which requires a certain length of time to prevent the camera from following the sudden rotation of the drone and causing unclear image acquisition; two clockwork springs with opposite rotation directions are used to connect the drone and the suspension bracket to achieve a movable connection between the camera and the drone, and ensure that the camera can eventually return to its original position.

[0021] The large-scale real-scene 3D modeling method for digital twin city construction of the present invention has the following advantages:

[0022] (1) The planetary gear and gear ring meshing transmission structure ensures the duration of the camera's process from lag to reset, and the design is reasonable;

[0023] (2) The flexible connection between the drone and the camera is achieved by using two springs with opposite rotation directions, which smoothly realizes the steering hysteresis and reset action of the camera. This is an ingenious design.

[0024] (3) The flight route of the UAV must be set along the longitude and latitude lines, and the images are exported in sequence according to the position for feature matching and grayscale matching, which greatly enhances the modeling efficiency.

[0025] Therefore, this large-scale real-scene three-dimensional modeling system and method in the construction of digital twin cities can solve the problem of five cameras rotating synchronously when the drone turns quickly, causing the cameras to turn at a large angle in a very short time, resulting in the collected images becoming blurred. It can also realize real-scene three-dimensional rapid modeling, which is of great significance for promoting the accurate expression of urban data information and accelerating the construction of digital twin cities.

[0026] Other features and advantages of the present invention will be set forth in the following description or may be learned by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0028] Figure 1 It is a schematic diagram of the top structure of the UAV assembly.

[0029] Figure 2 It is a schematic diagram of the bottom structure of the UAV assembly.

[0030] Figure 3 It is a structural diagram of an internal gear plate, a suspension bracket, a camera bracket, and a camera assembled on the bottom of a drone.

[0031] Figure 4 It is a structural diagram of a camera.

[0032] Figure 5 This is a schematic diagram of the assembly structure of the camera bracket, suspension bracket, and internal gear plate after the camera is removed.

[0033] Figure 6 It is a structural diagram of a camera bracket.

[0034] Figure 7 This is a schematic diagram of the assembly structure after removing the internal gear plate and suspension bracket of the camera bracket.

[0035] Figure 8 This is a schematic diagram of the assembly structure of the suspension bracket and planetary gears in a cutaway state of the internal gear plate.

[0036] Figure 9 It is a structural diagram of the internal gear.

[0037] Figure 10 This is a schematic diagram of the assembly structure of the suspension bracket, ball bearings, planetary gears, and drone after removing the internal gear plate.

[0038] Figure 11 This is a schematic diagram of the assembly structure of the suspension bracket, the spring, and the drone in a cutaway state.

[0039] Figure 12 It is a schematic diagram of the assembly structure of the suspension bracket, clockwork spring, bearing, planetary gear, top column and ball bearing.

[0040] Figure 13 It is a schematic diagram of the assembly structure of the suspension bracket, bearings, planetary gears, top column, and ball bearings.

[0041] Figure 14 It is a schematic diagram of the assembly structure of the top column and ball.

[0042] Figure 15 This is a schematic diagram of the assembly structure of the suspension bracket, bearings, and planetary gears after removing the top column.

[0043] Figure 16 It is a schematic diagram of the bottom structure of the suspension bracket.

[0044] Figure 17 It is a schematic diagram of the top structure of the suspension bracket.

[0045] Figure 18 This is a schematic diagram of the structure of the connecting column at the bottom of the drone.

[0046] Figure 19 It is a flow chart of the modeling method.

[0047] Numbers in the figure: 1-UAV, 101-connecting column, 2-inner gear plate, 201-transmission cavity, 202-center hole, 203-gear ring, 3-suspension bracket, 301-connecting cavity, 302-support rod, 303-hinge shaft, 304-threaded hole, 305-threaded column, 4-ball, 5-bearing, 6-planetary gear, 7-top column, 8-camera bracket, 801-fixing plate, 802-fixing hole, 803-support column, 804-support plate, 9-camera, 10-spring. DETAILED DESCRIPTION

[0048] The following will further describe in detail a large-scale real-scene three-dimensional modeling system and method for digital twin city construction in conjunction with the accompanying drawings and embodiments of the present invention.

[0049] The technical solution adopted by the present invention is a large-scale real-scene 3D modeling system in the construction of digital twin cities. Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 、 Figure 11 、 Figure 12 、 Figure 13 、 Figure 14 、 Figure 15 、 Figure 16 、 Figure 17 、 Figure 18 As shown, it is characterized by:

[0050] The invention comprises a drone 1, an internal gear plate 2, a suspension bracket 3, a ball 4, a bearing 5, a planetary gear 6, a top column 7, a camera bracket 8, a camera 9, and a spring 10.

[0051] A cylindrical connecting column 101 extending vertically downward is provided at the bottom center of the housing of the drone 1 .

[0052] The internal gear disc 2 is an oblate cylinder, and an oblate cylindrical transmission cavity 201 is provided downward on the top surface of the oblate cylinder. A circular center hole 202 is provided at the bottom center of the transmission cavity 201. A gear ring 203 is processed on the vertical cylindrical surface of the transmission cavity 201 around the central axis of the transmission cavity 201; the internal gear disc 2 is screwed to the bottom center of the drone 1, and the top surface of the internal gear disc 2 is close to the bottom surface of the casing of the drone 1, and the central axis of the internal gear disc 2 is collinear with the central axis of the connecting column 101.

[0053] The center of the suspension bracket 3 is a cylinder with an outer diameter smaller than the center hole 202, which is located in the center hole 202. The bottom surface of the cylinder is lower than the bottom surface of the inner gear disk 2. Four threaded columns 305 are evenly distributed on the bottom surface of the cylinder around the center axis of the cylinder. A cylindrical connecting cavity 301 is opened downward on the top surface of the cylinder. The center axis of the connecting cavity 301 and the center axis of the connecting column 101 are collinear, and a gap is left between the connecting column 101 and the bottom surface of the connecting cavity 301; the outer cylindrical surface of the cylinder is close to the top and is evenly provided with three horizontal radial support rods 302 around the center axis of the cylinder. The bottom of the outermost end of the support rod 302 is embedded with a ball 4, which rolls on the bottom surface of the transmission cavity 201; the top of the outer end of the support rod 302 is provided with a thin cylindrical hinge shaft 303, and the hinge shaft 303 is fitted with a bearing 5, and the top surface of the hinge shaft 303 is provided with a threaded hole 304 downward.

[0054] The planetary gear 6 consists of three pieces, which are respectively mounted on three bearings 5. The planetary gear 6 is engaged with the gear teeth on the gear ring 203 of the internal gear plate 2; the bottom of the top column 7 is screwed into the threaded hole 304 of the hinge shaft 303 to limit the upward movement of the bearing 5. The top of the top column 7 is embedded with a ball 4, which rolls on the bottom surface of the drone 1.

[0055] The top of the camera bracket 8 is a fixing plate 801, which is provided with four fixing holes 802. The fixing holes 802 are mounted on the threaded columns 305 at the bottom of the suspension bracket 3 and are locked with nuts. A vertical cylinder is provided in the center of the bottom surface of the fixing plate 801, and a horizontal support plate 804 is provided on the bottom end of the vertical cylindrical surface. Four horizontal cylindrical support columns 803 extend outward from the outer cylindrical surface of the vertical cylinder near the bottom end, and the angle between the central axes of adjacent support columns 803 is 90 degrees. The outer end of each support column 803 is provided with a support plate 804 that is at an angle of 45 degrees to the horizontal plane, and a camera 9 is screwed on the bottom surface of each support plate 804.

[0056] The clockwork spring 10 consists of two pieces, which are installed in the connecting cavity 301 of the suspension bracket 3 in sequence. The inner end of the clockwork spring 10 is fixed to the connecting column 101 of the drone 1, and the outer end is fixed to the inner cylindrical surface of the connecting cavity 301. One of the clockwork springs 10 rotates clockwise and the other rotates counterclockwise.

[0057] A large-scale real-scene 3D modeling method for digital twin city construction, such as Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 、 Figure 11 、 Figure 12 、 Figure 13 、 Figure 14 、 Figure 15 、 Figure 16 、 Figure 17 、 Figure 18 、 Figure 19 As shown, it is characterized by:

[0058] Step 1: UAV 1 has a built-in positioning module, communication module, and processor, and the processor executes commands sent by the ground control terminal; a camera 9 is installed on the bottom of UAV 1, and a movable assembly structure is used between camera 9 and UAV 1. A gear ring 203 structure is arranged on the bottom of UAV 1, and camera 9 is fixed to camera bracket 8. The outer end of camera bracket 8 is equipped with a planetary gear 6 that meshes with gear ring 203; a connecting column 101 is provided on the bottom of UAV 1, and the inner end of camera bracket 8 is connected to the connecting column 101 via two upper and lower springs 10. The inner end of spring 10 is fixed to the connecting column 101, and the outer end is fixed to the inner end of camera bracket 8. The two springs 10 have opposite rotation directions.

[0059] Step 2: Set the flight route of UAV 1. The flight route is set to fly only along the longitude and latitude lines. That is, when UAV 1 flies along the longitude line, the longitude does not change, and when UAV flies along the latitude line, the latitude does not change.

[0060] Step 3: Capture the image and record the corresponding position data. Based on the position data, the image is exported in sequence for feature matching and grayscale matching.

[0061] Step 4: Generate a white model based on the building plan and elevation data and perform an accuracy check: , where E is the error, n is the number of monitoring points, and △i is the difference between two measurement points at the same location;

[0062] Step 5: Generate a 3D model through texture mapping.

[0063] The present invention adopts a structure in which the planetary gear 6 and the gear ring 203 of the internal gear plate 2 are meshed, so that the rotation process of the camera bracket 8 must rely on the meshing transmission of the planetary gear 6 and the gear ring 203, which requires a certain amount of time to prevent the camera 9 from following the sudden rotation of the drone 1 and causing unclear image acquisition; two clockwork springs 10 with opposite rotation directions are used to connect the drone 1 and the suspension bracket 3 to achieve a movable connection between the camera 9 and the drone 1, and ensure that the camera 9 can eventually return to its original position.

[0064] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A large-scale real-scene 3D modeling system for digital twin city construction, characterized by: It includes a drone (1), an internal gear plate (2), a suspension bracket (3), a ball bearing (4), a bearing (5), a planetary gear (6), a top column (7), a camera bracket (8), a camera (9), and a spring (10); A cylindrical connecting column (101) extending vertically downward is provided at the bottom center of the housing of the drone (1); The inner gear disc (2) is an oblate cylinder, and an oblate cylindrical transmission cavity (201) is provided downward on the top surface of the oblate cylinder. A circular center hole (202) is provided at the center of the bottom of the transmission cavity (201). A gear ring (203) is processed on the vertical cylindrical surface of the transmission cavity (201) around the center axis of the transmission cavity (201); the inner gear disc (2) is screwed to the center of the bottom of the drone (1), the top surface of the inner gear disc (2) is close to the bottom surface of the casing of the drone (1), and the center axis of the inner gear disc (2) is collinear with the center axis of the connecting column (101); The center of the suspension bracket (3) is a cylinder with an outer diameter smaller than the center hole (202), which is located in the center hole (202). The bottom surface of the cylinder is lower than the bottom surface of the inner gear plate (2). Four threaded columns (305) are evenly distributed on the bottom surface of the cylinder around the center axis of the cylinder. A cylindrical connecting cavity (301) is opened downward on the top surface of the cylinder. The center axis of the connecting cavity (301) and the center axis of the connecting column (101) are collinear. The connecting column (101) and the bottom surface of the connecting cavity (301) are aligned. There is a gap between them; three horizontal radial support rods (302) are evenly arranged on the outer cylindrical surface of the cylinder near the top and around the central axis of the cylinder, and the bottom of the outermost end of the support rod (302) is embedded with a ball (4) that rolls on the bottom surface of the transmission cavity (201); a thin cylindrical hinge shaft (303) is provided at the top of the outer end of the support rod (302), and a bearing (5) is mounted on the hinge shaft (303), and a threaded hole (304) is opened downward on the top surface of the hinge shaft (303); The planetary gear (6) has three pieces, which are respectively mounted on three bearings (5). The planetary gear (6) is meshed with the gear teeth on the gear ring (203) of the internal gear plate (2). The bottom of the top column (7) is screwed into the threaded hole (304) of the hinge shaft (303) to limit the upward movement of the bearing (5). The top of the top column (7) is embedded with a ball (4) to roll on the bottom surface of the drone (1). The top of the camera bracket (8) is a fixing plate (801), and four fixing holes (802) are opened on the fixing plate (801), and the fixing holes (802) are mounted on the threaded columns (305) at the bottom of the suspension bracket (3) and locked with nuts; a vertical cylinder is provided in the center of the bottom surface of the fixing plate (801), and a horizontal support plate (804) is provided at the bottom end of the vertical cylindrical surface. Four horizontal cylindrical support columns (803) extend outward from the outer cylindrical surface of the vertical cylinder near the bottom end, and the angle between the central axes of adjacent support columns (803) is 90 degrees. The outer end of each support column (803) is provided with a support plate (804) with an angle of 45 degrees to the horizontal plane, and a camera (9) is screwed on the bottom surface of each support plate (804); The spring spring (10) comprises two pieces, which are sequentially installed in the connecting cavity (301) of the suspension bracket (3) from top to bottom. The inner end of the spring spring (10) is fixed on the connecting column (101) of the drone (1), and the outer end is fixed on the inner cylindrical surface of the connecting cavity (301). One of the spring springs (10) rotates clockwise, while the other rotates counterclockwise. The drone (1) has a built-in positioning module, a communication module, and a processor, and the processor executes the instructions sent by the ground control terminal; the flight route of the drone (1) is set, and the flight route is set to fly only along the longitude and latitude, that is, when the drone (1) flies along the longitude, the longitude does not change, and when the drone flies along the latitude, the latitude does not change; the image is captured and the corresponding position data is recorded, and the image is sequentially exported based on the position data for feature matching and grayscale matching; a white model is generated based on the building plane and elevation data, and an accuracy check is performed: , where E is the error, n is the number of monitoring points, and △i is the difference between two measurement points at the same location; a three-dimensional model is generated through texture mapping.

Images