CN114332360A - Collaborative three-dimensional mapping method and system - Google Patents
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Abstract
The invention provides a collaborative three-dimensional mapping method and a collaborative three-dimensional mapping system, which comprise the following steps: detecting the visual positioning mark through a cloud end; optimizing pose estimation of the unmanned aerial vehicle visual odometer through the visual positioning mark; optimizing the pose estimation of the unmanned vehicle vision odometer through the vision positioning mark; and completing a local map construction thread and a closed loop detection thread of the ORB-SLAM framework through the cloud. Compared with the prior art, the method is mainly realized based on an ORB-SLAM framework and a cloud end, the unmanned aerial vehicle and the unmanned vehicle realize a tracking thread in the ORB-SLAM, the cloud end realizes a local map construction thread and a closed loop detection thread in the ORB-SLAM, the visual positioning mark is utilized to optimize the pose estimation of the unmanned aerial vehicle visual odometer, the visual positioning mark is utilized to optimize the pose estimation of the unmanned vehicle visual odometer, the problems that the real-time performance of the cooperative SLAM system is difficult to meet and the positioning of the cooperative SLAM system is inaccurate can be solved, and the cooperative three-dimensional mapping system with good robustness, high precision and strong real-time performance can be realized.
Description
Technical Field
The invention relates to the field of collaborative three-dimensional mapping, in particular to a collaborative three-dimensional mapping method and a collaborative three-dimensional mapping system.
Background
In the prior art, a technology of realizing three-dimensional plane construction of multiple robots by adopting a road sign and monocular camera sensor technology exists, but the system in the prior art has poor real-time performance;
the two-dimensional plane mapping of a single robot is realized by adopting a road sign and a cloud architecture, but the system is not suitable for large-scale environment application.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a collaborative three-dimensional mapping method and a collaborative three-dimensional mapping system, and the specific technical scheme is as follows:
a collaborative three-dimensional mapping method comprises the following steps:
detecting the visual positioning mark through a cloud end;
optimizing pose estimation of the unmanned aerial vehicle visual odometer through the visual positioning mark;
optimizing the pose estimation of the unmanned vehicle vision odometer through the vision positioning mark;
and completing a local map construction thread and a closed loop detection thread of the ORB-SLAM framework through the cloud.
In a specific embodiment, the method further comprises the following steps:
collecting environment information, adopting Docker as a cloud container, Kubernetes as a scheduling service of the container, and BRPC and Beego as network frameworks to build a cloud platform, so that a multi-agent end communicates with the cloud end;
the multi-agent comprises the unmanned aerial vehicle and the unmanned vehicle, the unmanned aerial vehicle and the unmanned vehicle form a centralized system structure, a first monocular camera is arranged in the front of the unmanned aerial vehicle, the lens of the first monocular camera faces downwards, a second monocular camera is arranged in the front of the unmanned vehicle, and the lens of the second monocular camera faces forwards;
and (4) selecting at least 2 environmental points, and printing the visual positioning mark.
In a specific embodiment, the method further comprises the following steps:
the environment information comprises image information, and feature points and descriptors are extracted from the image information by adopting an ORB-SLAM algorithm;
obtaining depth through a PnP algorithm to obtain point cloud information;
map initialization is carried out by utilizing the cloud platform, if a map exists on the cloud platform, the image information is matched with the key frame of the cloud end to determine an initial position, and if no map exists on the cloud platform, the image information, the map and other information are used as the start of a cloud platform system map;
estimating the pose of the camera by matching the feature point pairs or a repositioning method;
establishing a relation between the image feature points and the local point cloud map;
and extracting the key frame and uploading the key frame to the cloud according to the judgment condition of the key frame.
In a specific embodiment, the "establishing a relationship between the image feature point and the local point cloud map" specifically includes:
when the local map fails to track due to the principles of shielding or texture missing on the environment and the like, the system adopts the following modes to reposition:
relocating and matching reference frames in a local map on the drone or the drone vehicle;
and carrying out repositioning on the cloud platform according to the information of the current frame.
In a specific embodiment, the "visually positioning mark through cloud detection" specifically includes:
carrying out image edge detection;
screening out the outline edges of the quadrangle;
and decoding the outline edge of the quadrangle and identifying the visual positioning mark.
In a specific embodiment, the "optimizing the pose estimation of the unmanned aerial vehicle visual odometer by the visual positioning mark" specifically includes:
defining coordinate system, defining coordinate system P of unmanned aerial vehicle loading cameraCUnmanned aerial vehicle coordinate system PAVisual positioning mark coordinate system PBAnd a world coordinate system PWSaid world coordinate system PWDefining as the drone first frame;
unmanned aerial vehicle loads camera coordinate system PCThe YOZ plane and the unmanned aerial vehicle coordinate system PAYOZ planes are parallel, and the unmanned aerial vehicle coordinate system P is arrangedAIs at the drone center;
calculating the coordinate system P of the unmanned aerial vehicle loading cameraCTo the world coordinate system PWThe relationship of (1);
calculating the coordinate system P of the unmanned aerial vehicle loading cameraCAnd the visual positioning mark coordinate system PBRelative position and attitude ofAnd
and solving a track error through the relative pose obtained by the visual positioning mark and the relative pose obtained by the visual odometer, and equally dividing the track error on each key frame of the unmanned aerial vehicle, so that the closed loop key frame and the actual error are reduced.
In a specific embodiment, the "calculating the drone loading camera coordinate system PCTo the world coordinate system PWThe relationship of (1) specifically includes:
unmanned aerial vehicle coordinate system PAWith the unmanned aerial vehicle loads camera coordinate system PCIs a parallel relationship, existing:
wherein, PACoordinates, P, representing the coordinate system of the droneCCoordinates representing the drone loading camera coordinate system,is the unmanned aerial vehicle coordinate system PAAnd said does notMan-machine loaded camera coordinate system PCA translation vector therebetween representing a distance of the camera from the center of the drone;
the visual positioning marker coordinate system PBAnd the world coordinate system PWThe relationship between them satisfies:
wherein, PWIs the coordinate of the world coordinate system, PBFor the coordinates of the visual positioning marker coordinate system,for the world coordinate system PWAnd the visual positioning mark coordinate system PBA translation vector therebetween;
angles phi, theta and psi are euler angles, respectively, given said world coordinate system PWTo the unmanned aerial vehicle coordinate system PAIs a rotation matrix ofThe visual positioning marker coordinate system PBTo the unmanned aerial vehicle load camera coordinate system PCIs a rotation matrix ofThen:
c represents cos, s represents sin, and the visual positioning mark coordinate system P can be obtained according to the formulaBAnd the unmanned aerial vehicle loads the camera coordinate system PCThe rotational relationship includes:
and the unmanned aerial vehicle loads the camera coordinate system PCTo the visual positioning marker coordinate system PBThe relational expression of (A) is:
wherein,for the unmanned aerial vehicle to be loaded with a camera coordinate system PCTo the visual positioning marker coordinate system PBThe rotation matrix of (a) is,for the unmanned aerial vehicle to be loaded with a camera coordinate system PCTo the visual positioning marker coordinate system PBThe translation vector of (a);
obtaining the coordinate system P of the unmanned aerial vehicle loading cameraCTo the world coordinate system PWThe relationship of (1) includes:
wherein,is the unmanned aerial vehicle coordinate system PATo the world coordinate system PWThe rotation matrix of (a) is,is the unmanned aerial vehicle coordinate system PATo the world coordinate system PWThe translation vector of (a) is calculated,is the unmanned aerial vehicle coordinate system PATo the unmanned aerial vehicleCamera-mounted coordinate system PCThe translation vector of (2).
In a specific embodiment, the "calculating the drone loading camera coordinate system PCAnd the visual positioning mark coordinate system PBRelative position and attitude ofAndthe method specifically comprises the following steps:
projecting the visual localization markers to a 2D pixel plane of a camera using a camera model, resulting in:
wherein M represents a camera reference matrix, [ u, v,1 ]]Coordinates representing the projection of said visual positioning markers onto a normalized plane, [ XB, YB, ZB]Representing a visual positioning mark in the visual positioning mark coordinate system PBThe coordinates of (a) are (b),representing the visual positioning marker coordinate system PBTo the unmanned aerial vehicle load camera coordinate system PCThe translation vector of (a) is calculated,representing the visual positioning marker coordinate system PBTo the unmanned aerial vehicle load camera coordinate system PCS 1/ZCRepresenting an unknown scale factor, ZCRepresenting the Z-axis coordinate of the visual positioning mark under a camera coordinate system, and obtaining the Z-axis coordinate by adopting a direct linear transformation algorithmAnd
in a specific embodiment, the "optimizing the pose estimation of the unmanned vehicle visual odometer by the visual positioning mark" specifically includes:
defining a coordinate system, defining a coordinate system P of an unmanned vehicle-mounted cameraCVisual positioning mark coordinate system PBAnd a world coordinate system PWSaid world coordinate system PWDefined as the unmanned aerial vehicle first frame, the unmanned aerial vehicle is loaded with a camera coordinate system PCAnd the unmanned vehicle coordinate system PADetermining the relationship of (1);
obtaining the coordinate system P of the unmanned vehicle loading cameraCAnd the world coordinate system PWRelative pose TcwThe visual positioning mark coordinate system PBAnd the unmanned vehicle-mounted camera coordinate system PCRelative pose TbcAnd the visual positioning mark coordinate system PBAnd the world coordinate system PWRelative pose Tbw;
Optimizing the pose and point cloud coordinates of the unmanned vehicle;
defining said visual positioning marker coordinate system PBAnd the unmanned vehicle-mounted camera coordinate system PCThe relative error between each other is:
constructing an optimization objective function:
wherein:
Tcw∈{(Rcw,tcw)|Rcw∈SO3,tcw∈R3}Tbc∈{(Rbc,tbc)|Rbc∈SO3,tbc∈R3}
wherein, SO3Representing three-dimensional special orthogonal groups, tcwRepresenting camera coordinates loaded from the unmanned vehicleIs PCTo the world coordinate system PWTranslation error of tbcRepresenting a coordinate system P from said visual positioning markerBTo the unmanned vehicle-mounted camera coordinate system PCTranslation error of R3Representing a set of radicals of dimension 3, RcwRepresenting camera coordinate system P loaded from said unmanned vehicleCTo the world coordinate system PWTranslation error of RbcRepresenting a coordinate system P from said visual positioning markerBTo the unmanned vehicle-mounted camera coordinate system PCThe rotational error of (a);
the camera motion not only causes a rotation error Rcw、RbcAnd translation error tcw、tbcSince the scale is also shifted in accordance with the scale, the transform is performed for the scale, and the Sim3 transform algorithm is used, so that:
Scw=(Rcw,tcw,s=1),(Rcw,tcw)=Tcw
Sbc=(Rbc,tbc,s=1),(Rbc,tbc)=Tbc
wherein S iscwRepresenting visual alignment mark points from the world coordinate system PWTo the unmanned vehicle-mounted camera coordinate system PCBy similarity transformation of SbcRepresenting the visual alignment mark point from the visual alignment mark coordinate system PBTo the unmanned vehicle-mounted camera coordinate system PCS denotes the unknown to scale factor;
wherein R isbwRepresenting the visual alignment marker point from the world coordinate system PWTo the visual positioning marker coordinate system PBScrew ofRotation matrix, tbwRepresenting the visual alignment marker point from the world coordinate system PWTo the visual positioning marker coordinate system PBS denotes the unknown to scale factor,representing the optimized rotation matrix, translation vector and scale factor,representing the optimized similarity transformation;
setting the 3D position of the unmanned vehicle before optimization occurs asThe transformed coordinates can be found:
A collaborative three-dimensional mapping system is used for realizing the collaborative three-dimensional mapping method, and comprises the following steps:
the environment preparation module is used for acquiring environment information;
the information processing module is used for extracting the key frame from the acquired environment information by adopting a Tracking thread design idea in an ORB-SLAM algorithm framework;
the detection module is used for detecting the visual positioning mark through the cloud end;
the first optimization module is used for optimizing the pose estimation of the unmanned aerial vehicle visual odometer through the visual positioning mark;
the second optimization module is used for optimizing the pose estimation of the unmanned vehicle vision odometer through the vision positioning mark; and the execution module is used for completing a local map construction thread and a closed loop detection thread of the ORB-SLAM framework through the cloud.
Compared with the prior art, the invention has the following beneficial effects:
the cooperative three-dimensional mapping method and the cooperative three-dimensional mapping system can solve the problems that the real-time performance of the cooperative SLAM system is difficult to meet and the positioning of the cooperative SLAM system is inaccurate, and can realize the cooperative three-dimensional mapping system with good robustness, high precision and strong real-time performance.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a schematic view of an imaging model of a camera in an embodiment;
FIG. 2 is a flowchart illustrating the three-dimensional collaborative mapping method according to an embodiment;
FIG. 3 is a block diagram of the collaborative three-dimensional mapping system according to an embodiment.
Detailed Description
Examples
As shown in fig. 1-2, the present embodiment provides a collaborative three-dimensional mapping method, including:
preparing environment, and collecting environment information;
processing information, namely extracting a key frame from the acquired environment information by adopting a Tracking thread design idea in an ORB-SLAM algorithm framework;
detecting a visual positioning mark through a cloud end, wherein the visual positioning mark is a road sign;
optimizing pose estimation of the unmanned aerial vehicle visual odometer through the visual positioning mark;
optimizing the pose estimation of the unmanned vehicle vision odometer through the vision positioning mark;
and completing a local map construction thread and a closed loop detection thread of the ORB-SLAM framework through the cloud.
Specifically, the cloud executes a Local Mapping thread (Local Mapping thread) and a closed Loop detection thread (Loop cloning thread) in the ORB-SLAM. The Cooperative SLAM (CSLAM) is superior to a single robot in terms of fault tolerance, robustness and execution efficiency, and has an important influence on tasks such as disaster relief, resource detection and space detection in an unknown environment. The data calculation storage in the CSLAM system is large, and most of robot individuals cannot meet the real-time requirement. CSLAM systems usually perform tasks in large-scale environments, and the system errors (pose estimation errors, etc.) accumulated by a large number of calculations cannot be completely eliminated to some extent. Moreover, when there are a large number of repetitive features in the environment, the feature point matching or overlap region matching algorithm may be mismatched to some extent. The accumulated system errors and the mismatching affect the map building precision of the CSLAM system, so that a small number of road signs are arranged in the environment, the robot can optimize the self pose according to the road signs, and the method has important significance for improving the map building precision. Compared with a two-dimensional map, the three-dimensional map has richer information quantity and can better reflect the objective existence form of the real world.
Specifically, the visual positioning marking technology, namely the road sign technology can assist the camera laser radar sensor in realizing more accurate positioning and map building, the cloud architecture technology can transfer complex operation in the multi-robot SLAM technology to the cloud end for realization, the problem that the multi-robot computing and storing resources are limited is solved, map environment information of a three-dimensional plane is richer, and functions of navigation, obstacle avoidance and the like of the unmanned aerial vehicle are facilitated.
Preferably, a spacious place is selected to be marked with a road sign (AprilTag code) in a large-scale unknown environment, a monocular camera is loaded on an unmanned aerial vehicle and an unmanned vehicle, the monocular camera is used for collecting environment information in real time in the process of multi-agent traveling, an ORB-SLAM framework is used for collaborative three-dimensional mapping, the AprilTag code is used for optimizing ORB-SLAM pose estimation, a cloud platform is built by Docker + Kubernets + BRPC + Beego technology, tasks with large calculation amount and high storage requirement are deployed at the cloud end, and a multi-agent end is used for tracking and repositioning.
Preferably, in this embodiment, by combining the road sign aprilat + cloud architecture + multiple robots + SLAM three-dimensional mapping technology, unmanned cooperative three-dimensional mapping is realized, the problems that the real-time performance of the cooperative SLAM system is difficult to meet and the positioning of the cooperative SLAM system is inaccurate can be solved, and the unmanned cooperative three-dimensional mapping system with good robustness, high precision and strong real-time performance can be realized.
In this embodiment, "collecting environmental information" specifically includes:
the cloud platform is built by adopting Docker + Kubernets + BRPC + Beego technology, so that the multi-agent end is communicated with a cloud end, specifically, Docker is used as a cloud end container, Kubernets is used as scheduling service of the container, BRPC and Beego are used as network frameworks to build the cloud platform, and the multi-agent end is communicated with the cloud end;
the multi-agent comprises an unmanned aerial vehicle and an unmanned vehicle, and the unmanned aerial vehicle and the unmanned vehicle form a centralized system structure;
and (3) selecting at least 2 environment points, and marking a visual positioning mark, namely, an AprilTag code.
In this embodiment, "unmanned aerial vehicle and unmanned vehicle constitute centralized architecture" specifically includes:
unmanned aerial vehicle place ahead position is equipped with first monocular camera and the camera lens of first monocular camera down, and unmanned vehicles position is equipped with second monocular camera and the camera lens of second monocular camera forward.
In this embodiment, "information processing" specifically includes:
the environment information comprises image information, and feature points and descriptors are extracted from the image information by adopting an ORB-SLAM algorithm;
obtaining depth through a PnP algorithm to obtain point cloud information;
carrying out map initialization by using a cloud platform, matching image information with a key frame of a cloud end to determine an initial position if the cloud platform has a map, and taking the image information, the map and other information as the start of a cloud platform system map if the cloud platform does not have the map;
estimating the pose of the camera by matching the feature point pairs or a repositioning method;
establishing a relation between the image feature points and the local point cloud map;
and extracting the key frame and uploading the key frame to the cloud according to the judgment condition of the key frame.
In this embodiment, the "establishing a relationship between the image feature points and the local point cloud map" specifically includes:
when the local map fails to track due to the principles of shielding or texture missing on the environment and the like, the system adopts the following modes to reposition:
repositioning and matching reference frames in a local map on the drone or drone vehicle;
and carrying out repositioning on the cloud platform through the information of the current frame.
In this embodiment, the "visual positioning mark is detected through the cloud" specifically includes:
carrying out image edge detection;
screening out the outline edges of the quadrangle;
the contour edge of the quadrangle is decoded to identify the visual positioning mark, i.e. identify the road sign (AprilTag).
In this embodiment, the "optimizing the pose estimation of the unmanned aerial vehicle visual odometer by the visual positioning mark" specifically includes:
defining coordinate system, defining coordinate system P of unmanned aerial vehicle loading cameraCUnmanned aerial vehicle coordinate system PAVisual positioning mark coordinate system PBAnd a world coordinate system PWWorld coordinate system PWDefining as a first frame of the drone;
unmanned aerial vehicle loads camera coordinate system PCYOZ plane and unmanned aerial vehicle coordinate system PAYOZ planes are parallel, and an unmanned aerial vehicle coordinate system P is arrangedAThe origin of (a) is at the center of the unmanned aerial vehicle;
calculating a coordinate system P of a camera loaded by the unmanned aerial vehicleCTo the world coordinate system PWThe relationship of (1);
calculating a coordinate system P of a camera loaded by the unmanned aerial vehicleCAnd a visual alignment mark coordinate system PBRelative position and attitude ofAnd
the trajectory error is solved through the visual positioning mark, namely the relative pose obtained through the road sign (AprilTag) and the relative pose obtained through the visual odometer, and is equally divided on each key frame of the unmanned aerial vehicle, so that the closed loop key frame and the actual error are reduced.
In this embodiment, "calculate the coordinate system P of the camera loaded by the droneCTo the world coordinate system PWThe relationship of (1) specifically includes:
unmanned aerial vehicle coordinate system PAWith unmanned aerial vehicle loading camera coordinate system PCIs a parallel relationship, existing:
wherein, PACoordinates representing the coordinate system of the drone, PCCoordinates representing the drone loading camera coordinate system,for unmanned aerial vehicle coordinate system PAWith unmanned aerial vehicle loading camera coordinate system PCA translation vector therebetween, representing the distance of the camera from the center of the drone;
visual positioning marker coordinate system PBWith the world coordinate system PWThe relationship between them satisfies:
wherein, PWAs coordinates of the world coordinate system, PBFor visual positioning of the coordinates of the coordinate system of the markers,as a world coordinate system PWAnd a visual alignment mark coordinate system PBA translation vector therebetween;
the angles phi, theta and psi are Euler angles, respectively, given a world coordinate system PWTo unmanned aerial vehicle coordinate system PAIs a rotation matrix ofVisual positioning marker coordinate system PBLoading of camera coordinate System P to unmanned aerial vehicleCIs a rotation matrix ofThen:
c represents cos, s represents sin, and the visual positioning mark coordinate system P can be obtained according to the formulaBAnd unmanned aerial vehicle loads camera coordinate system PCThe rotational relationship includes:
and unmanned aerial vehicle loads camera coordinate system PCTo the visual alignment marker coordinate system PBThe relational expression of (A) is:
wherein,loading a camera coordinate system P for an unmanned aerial vehicleCTo the visual positioning markCoordinate system PBThe rotation matrix of (a) is,loading a camera coordinate system P for an unmanned aerial vehicleCTo the visual alignment marker coordinate system PBThe translation vector of (a);
then obtaining a coordinate system P of the unmanned aerial vehicle loading cameraCTo the world coordinate system PWThe relationship of (1) includes:
wherein,for unmanned aerial vehicle coordinate system PATo the world coordinate system PWThe rotation matrix of (a) is,for unmanned aerial vehicle coordinate system PATo the world coordinate system PWThe translation vector of (a) is calculated,for unmanned aerial vehicle coordinate system PALoading of camera coordinate System P to unmanned aerial vehicleCThe translation vector of (2). WhereinAndis unknown.
In this embodiment, "calculate the coordinate system P of the camera loaded by the droneCAnd a visual alignment mark coordinate system PBRelative position and attitude ofAndthe method specifically comprises the following steps:
projecting the visual localization markers onto the 2D pixel plane of the camera using the camera model yields:
wherein M represents a camera reference matrix, [ u, v,1 ]]Coordinates representing the projection of the visual alignment marks onto the normalized plane, [ XB, YB, ZB]Representing the visual alignment mark in a visual alignment mark coordinate system PBThe coordinates of (a) are (b),representing a visual positioning marker coordinate system PBLoading of camera coordinate System P to unmanned aerial vehicleCThe translation vector of (a) is calculated,representing a visual positioning marker coordinate system PBLoading of camera coordinate System P to unmanned aerial vehicleCS 1/ZCRepresenting an unknown scale factor, ZCRepresenting the Z-axis coordinate of the visual positioning mark in a camera coordinate system, and calculating by adopting a DLT (Direct Linear Transform) algorithmAnd
in this embodiment, the "optimizing the pose estimation of the unmanned vehicle vision odometer by the vision positioning mark" specifically includes:
defining a coordinate system, defining a coordinate system P of an unmanned vehicle-mounted cameraCVisual positioning mark coordinate system PBAnd a world coordinate system PWWorld coordinate system PWDefined as the first frame of the unmanned plane, unmanned vehicle-mounted camera coordinate system PCAnd unmanned vehicle coordinate system PADetermining the relationship of (1);
obtaining a coordinate system P of the unmanned vehicle loading cameraCSit with the worldMarker system PWRelative pose TcwVisual positioning mark coordinate system PBAnd unmanned vehicle-mounted camera coordinate system PCRelative pose TbcAnd a visual positioning marker coordinate system PBWith the world coordinate system PWRelative pose Tbw;
Optimizing the pose and point cloud coordinates of the unmanned vehicle;
defining a visual alignment marker coordinate system PBAnd unmanned vehicle-mounted camera coordinate system PCThe relative error between each other is:
constructing an optimization objective function:
wherein:
Tcw∈{(Rcw,tcw)|Rcw∈SO3,tcw∈R3}Tbc∈{(Rbc,tbc)|Rbc∈SO3,tbc∈R3}
wherein, SO3Representing three-dimensional special orthogonal groups, tcwRepresenting camera coordinate system P loaded from unmanned vehicleCTo the world coordinate system PWTranslation error of tbcRepresenting a coordinate system P for positioning a marker from visionBUnmanned vehicle-mounted camera coordinate system PCTranslation error of R3Representing a set of radicals of dimension 3, RcwRepresenting camera coordinate system P loaded from unmanned vehicleCTo the world coordinate system PWTranslation error of RbcRepresenting a coordinate system P for positioning a marker from visionBUnmanned vehicle-mounted camera coordinate system PCThe rotational error of (a);
the camera motion not only causes a rotation error Rcw、RbcAnd translation error tcw、tbcAlso accompanied by a drift in dimensionSo a scale-directed transformation is performed and the Sim3 transformation algorithm is used, so:
Scw=(Rcw,tcw,s=1),(Rcw,tcw)=Tcw
Sbc=(Rbc,tbc,s=1),(Rbc,tbc)=Tbc
the Sim3 transformation algorithm is to solve similarity transformation by using 3 pairs of matching points, and further solve a rotation matrix, a translation vector and a scale between two coordinate systems; scwRepresenting visual alignment mark points from the world coordinate system PWUnmanned vehicle-mounted camera coordinate system PCBy similarity transformation of SbcCoordinate system P of secondary visual positioning mark representing visual positioning mark pointBUnmanned vehicle-mounted camera coordinate system PCS denotes the unknown to scale factor;
wherein R isbwRepresenting visual alignment mark points from the world coordinate system PWTo the visual alignment marker coordinate system PBRotation matrix of tbwRepresenting visual alignment mark points from the world coordinate system PWTo the visual alignment marker coordinate system PBS denotes the unknown to scale factor,representing the optimized rotation matrix, translation vector and scale factor,representing the optimized similarity transformation;
setting unmanned vehicles before optimization occursThe 3D position isThe transformed coordinates can be found:
As shown in fig. 3, a collaborative three-dimensional mapping system for implementing the collaborative three-dimensional mapping method includes:
the environment preparation module is used for acquiring environment information;
the information processing module is used for extracting the key frame from the acquired environment information by adopting a Tracking thread design idea in an ORB-SLAM algorithm framework;
a detection module for detecting a visual positioning mark, namely, a landmark (aprilat), through a cloud;
the first optimization module is used for optimizing the pose estimation of the unmanned aerial vehicle visual odometer through the visual positioning mark;
the second optimization module is used for optimizing the pose estimation of the unmanned vehicle vision odometer through the vision positioning mark;
and the execution module is used for completing a local map construction thread and a closed loop detection thread of the ORB-SLAM framework through the cloud.
Compared with the prior art, the cooperative three-dimensional mapping method and the cooperative three-dimensional mapping system provided by the embodiment combine the road sign AprilTag, the cloud architecture, the multiple robots and the SLAM three-dimensional mapping technology to realize unmanned cooperative three-dimensional mapping, can solve the problems that the cooperative SLAM system is difficult to meet in real time and the cooperative SLAM system is inaccurate in positioning, and can realize the cooperative three-dimensional mapping system with good robustness, high precision and strong real-time performance.
Those skilled in the art will appreciate that the figures are merely schematic representations of one preferred implementation scenario and that the blocks or flow diagrams in the figures are not necessarily required to practice the present invention.
Those skilled in the art will appreciate that the modules in the devices in the implementation scenario may be distributed in the devices in the implementation scenario according to the description of the implementation scenario, or may be located in one or more devices different from the present implementation scenario with corresponding changes. The modules of the implementation scenario may be combined into one module, or may be further split into a plurality of sub-modules.
The above-mentioned invention numbers are merely for description and do not represent the merits of the implementation scenarios.
The above disclosure is only a few specific implementation scenarios of the present invention, however, the present invention is not limited thereto, and any variations that can be made by those skilled in the art are intended to fall within the scope of the present invention.
Claims (10)
1. A collaborative three-dimensional mapping method is characterized by comprising the following steps:
detecting the visual positioning mark through a cloud end;
optimizing pose estimation of the unmanned aerial vehicle visual odometer through the visual positioning mark;
optimizing the pose estimation of the unmanned vehicle vision odometer through the vision positioning mark;
and completing a local map construction thread and a closed loop detection thread of the ORB-SLAM framework through the cloud.
2. The collaborative three-dimensional mapping method according to claim 1, further comprising:
collecting environment information, adopting Docker as a cloud container, Kubernetes as a scheduling service of the container, and BRPC and Beego as network frameworks to build a cloud platform, so that a multi-agent end communicates with the cloud end;
the multi-agent comprises the unmanned aerial vehicle and the unmanned vehicle, the unmanned aerial vehicle and the unmanned vehicle form a centralized system structure, a first monocular camera is arranged in the front of the unmanned aerial vehicle, the lens of the first monocular camera faces downwards, a second monocular camera is arranged in the front of the unmanned vehicle, and the lens of the second monocular camera faces forwards;
and (4) selecting at least 2 environmental points, and printing the visual positioning mark.
3. The collaborative three-dimensional mapping method according to claim 2, further comprising:
the environment information comprises image information, and feature points and descriptors are extracted from the image information by adopting an ORB-SLAM algorithm;
obtaining depth through a PnP algorithm to obtain point cloud information;
map initialization is carried out by utilizing the cloud platform, if a map exists on the cloud platform, the image information is matched with the key frame of the cloud end to determine an initial position, and if no map exists on the cloud platform, the image information, the map and other information are used as the start of a cloud platform system map;
estimating the pose of the camera by matching the feature point pairs or a repositioning method;
establishing a relation between the image feature points and the local point cloud map;
and extracting the key frame and uploading the key frame to the cloud according to the judgment condition of the key frame.
4. The collaborative three-dimensional mapping method according to claim 3, wherein the establishing of the relationship between the image feature points and the local point cloud map specifically comprises:
when the local map fails to track due to the principles of shielding or texture missing on the environment and the like, the system adopts the following modes to reposition:
relocating and matching reference frames in a local map on the drone or the drone vehicle;
and carrying out repositioning on the cloud platform according to the information of the current frame.
5. The collaborative three-dimensional mapping method according to claim 1, wherein the "visual positioning mark through cloud detection" specifically includes:
carrying out image edge detection;
screening out the outline edges of the quadrangle;
and decoding the outline edge of the quadrangle and identifying the visual positioning mark.
6. The collaborative three-dimensional mapping method according to claim 1, wherein the optimizing the pose estimation of the unmanned aerial vehicle visual odometer by the visual positioning markers specifically comprises:
defining coordinate system, defining coordinate system P of unmanned aerial vehicle loading cameraCUnmanned aerial vehicle coordinate system PAVisual positioning mark coordinate system PBAnd a world coordinate system PWSaid world coordinate system PWDefining as the drone first frame;
unmanned aerial vehicle loads camera coordinate system PCThe YOZ plane and the unmanned aerial vehicle coordinate system PAYOZ planes are parallel, and the unmanned aerial vehicle coordinate system P is arrangedAIs at the drone center;
calculating the coordinate system P of the unmanned aerial vehicle loading cameraCTo the world coordinate system PWThe relationship of (1);
calculating the coordinate system P of the unmanned aerial vehicle loading cameraCAnd the visual positioning mark coordinate system PBRelative position and attitude ofAnd
and solving a track error through the relative pose obtained by the visual positioning mark and the relative pose obtained by the visual odometer, and equally dividing the track error on each key frame of the unmanned aerial vehicle, so that the closed loop key frame and the actual error are reduced.
7. The collaborative three-dimensional mapping method according to claim 6, wherein the "calculating the UAV" is performedLoad camera coordinate system PCTo the world coordinate system PWThe relationship of (1) specifically includes:
unmanned aerial vehicle coordinate system PAWith the unmanned aerial vehicle loads camera coordinate system PCIs a parallel relationship, existing:
wherein, PACoordinates, P, representing the coordinate system of the droneCCoordinates representing the drone loading camera coordinate system,is the unmanned aerial vehicle coordinate system PAWith the unmanned aerial vehicle loads camera coordinate system PCA translation vector therebetween representing a distance of the camera from the center of the drone;
the visual positioning marker coordinate system PBAnd the world coordinate system PWThe relationship between them satisfies:
wherein, PWIs the coordinate of the world coordinate system, PBFor the coordinates of the visual positioning marker coordinate system,for the world coordinate system PWAnd the visual positioning mark coordinate system PBA translation vector therebetween;
angles phi, theta and psi are euler angles, respectively, given said world coordinate system PWTo the unmanned aerial vehicle coordinate system PAIs a rotation matrix ofThe visual positioning marker coordinate system PBTo the unmanned aerial vehicle load camera coordinate system PCIs a rotation matrix ofThen:
c represents cos, s represents sin, and the visual positioning mark coordinate system P can be obtained according to the formulaBAnd the unmanned aerial vehicle loads the camera coordinate system PCThe rotational relationship includes:
and the unmanned aerial vehicle loads the camera coordinate system PCTo the visual positioning marker coordinate system PBThe relational expression of (A) is:
wherein,for the unmanned aerial vehicle to be loaded with a camera coordinate system PCTo the visual positioning marker coordinate system PBThe rotation matrix of (a) is,for the unmanned aerial vehicle to be loaded with a camera coordinate system PCTo the visual positioning marker coordinate system PBThe translation vector of (a);
obtaining the coordinates of the unmanned aerial vehicle loading cameraIs PCTo the world coordinate system PWThe relationship of (1) includes:
wherein,is the unmanned aerial vehicle coordinate system PATo the world coordinate system PWThe rotation matrix of (a) is,is the unmanned aerial vehicle coordinate system PATo the world coordinate system PWThe translation vector of (a) is calculated,is the unmanned aerial vehicle coordinate system PATo the unmanned aerial vehicle load camera coordinate system PCThe translation vector of (2).
8. The collaborative three-dimensional mapping method according to claim 6, wherein said "calculating said drone loading camera coordinate system PCAnd the visual positioning mark coordinate system PBRelative position and attitude ofAndthe method specifically comprises the following steps:
projecting the visual localization markers to a 2D pixel plane of a camera using a camera model, resulting in:
wherein M represents the camera internal reference momentMatrix, [ u, v,1 ]]Coordinates representing the projection of said visual positioning markers onto a normalized plane, [ XB, YB, ZB]Representing a visual positioning mark in the visual positioning mark coordinate system PBThe coordinates of (a) are (b),representing the visual positioning marker coordinate system PBTo the unmanned aerial vehicle load camera coordinate system PCThe translation vector of (a) is calculated,representing the visual positioning marker coordinate system PBTo the unmanned aerial vehicle load camera coordinate system PCS 1/ZCRepresenting an unknown scale factor, ZCRepresenting the Z-axis coordinate of the visual positioning mark under a camera coordinate system, and obtaining the Z-axis coordinate by adopting a direct linear transformation algorithmAnd
9. the collaborative three-dimensional mapping method according to claim 1, wherein the optimizing pose estimation of the unmanned vehicle visual odometer by the visual positioning markers specifically comprises:
defining a coordinate system, defining a coordinate system P of an unmanned vehicle-mounted cameraCVisual positioning mark coordinate system PBAnd a world coordinate system PWSaid world coordinate system PWDefined as the unmanned aerial vehicle first frame, the unmanned aerial vehicle is loaded with a camera coordinate system PCAnd the unmanned vehicle coordinate system PADetermining the relationship of (1);
obtaining the coordinate system P of the unmanned vehicle loading cameraCAnd the world coordinate system PWRelative pose TcwThe visual positioning mark coordinate system PBAnd the unmanned vehicle-mounted camera coordinate system PCRelative positionPosture TbcAnd the visual positioning mark coordinate system PBAnd the world coordinate system PWRelative pose Tbw;
Optimizing the pose and point cloud coordinates of the unmanned vehicle;
defining said visual positioning marker coordinate system PBAnd the unmanned vehicle-mounted camera coordinate system PCThe relative error between each other is:
constructing an optimization objective function:
wherein:
Tcw∈{(Rcw,tcw)|Rcw∈SO3,tcw∈R3} Tbc∈{(Rbc,tbc)|Rbc∈SO3,tbc∈R3}
wherein, SO3Representing three-dimensional special orthogonal groups, tcwRepresenting camera coordinate system P loaded from said unmanned vehicleCTo the world coordinate system PWTranslation error of tbcRepresenting a coordinate system P from said visual positioning markerBTo the unmanned vehicle-mounted camera coordinate system PCTranslation error of R3Representing a set of radicals of dimension 3, RcwRepresenting camera coordinate system P loaded from said unmanned vehicleCTo the world coordinate system PWTranslation error of RbcRepresenting a coordinate system P from said visual positioning markerBTo the unmanned vehicle-mounted camera coordinate system PCThe rotational error of (a);
the camera motion not only causes a rotation error Rcw、RbcAnd translation error tcw、tbcSince the scale shift is also accompanied, the scale conversion is performed and Sim is used3 transformation algorithm, therefore:
Scw=(Rcw,tcw,s=1),(Rcw,tcw)=Tcw
Sbc=(Rbc,tbc,s=1),(Rbc,tbc)=Tbc
wherein S iscwRepresenting visual alignment mark points from the world coordinate system PWTo the unmanned vehicle-mounted camera coordinate system PCBy similarity transformation of SbcRepresenting the visual alignment mark point from the visual alignment mark coordinate system PBTo the unmanned vehicle-mounted camera coordinate system PCS denotes the unknown to scale factor;
wherein R isbwRepresenting the visual alignment marker point from the world coordinate system PWTo the visual positioning marker coordinate system PBRotation matrix of tbwRepresenting the visual alignment marker point from the world coordinate system PWTo the visual positioning marker coordinate system PBS denotes the unknown to scale factor,representing the optimized rotation matrix, translation vector and scale factor,representing the optimized similarity transformation;
setting the 3D position of the unmanned vehicle before optimization occurs asThe transformed coordinates can be found:
10. A collaborative three-dimensional mapping system for implementing the collaborative three-dimensional mapping method according to any one of claims 1 to 9, comprising:
the environment preparation module is used for acquiring environment information;
the information processing module is used for extracting the key frame from the acquired environment information by adopting a Tracking thread design idea in an ORB-SLAM algorithm framework;
the detection module is used for detecting the visual positioning mark through the cloud end;
the first optimization module is used for optimizing the pose estimation of the unmanned aerial vehicle visual odometer through the visual positioning mark;
the second optimization module is used for optimizing the pose estimation of the unmanned vehicle vision odometer through the vision positioning mark;
and the execution module is used for completing a local map construction thread and a closed loop detection thread of the ORB-SLAM framework through the cloud.
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