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robotics.PoseGraph

Create 2-D pose graph

Description

A PoseGraph object stores information for a 2-D pose graph representation. A pose graph contains nodes connected by edges, with edge constraints that define the relative pose between nodes and the uncertainty on that measurement. The optimizePoseGraph function modifies the nodes to account for the uncertainty and improve the overall graph.

For 3-D pose graphs, see PoseGraph3D.

To construct a pose graph iteratively, use addRelativePose to add a node and connect it to an existing node with specified edge constraints. Specify the uncertainty of the measurement using an information matrix. Adding an edge between two existing nodes creates a loop closure in the graph.

LidarSLAM (lidar-based simultaneous localization and mapping) is built around the optimization of a 2-D pose graph.

Creation

Syntax

poseGraph = robotics.PoseGraph
poseGraph = robotics.PoseGraph('MaxNumEdges',maxEdges,'MaxNumNodes',maxNodes)

Description

example

poseGraph = robotics.PoseGraph creates a 2-D pose graph object. Add poses using addRelativePose to construct a pose graph iteratively.

poseGraph = robotics.PoseGraph('MaxNumEdges',maxEdges,'MaxNumNodes',maxNodes) specifies an upper bound on the number of edges and nodes allowed in the pose graph when generating code. This limit is only required when generating code.

Properties

expand all

This property is read-only.

Number of nodes in pose graph, specified as a positive integer. Each node represents a pose in the pose graph as an [x y theta] vector with an xy-position and orientation angle, theta. To specify relative poses between nodes, use addRelativePose. To get a list of all nodes, use nodes.

This property is read-only.

Number of edges in pose graph, specified as a nonnegative integer. Each edge connects two nodes in the pose graph. Loop closure edges are included.

This property is read-only.

Number of loop closures in pose graph, specified as a nonnegative integer. To get the edge IDs of the loop closures, use the LoopClosureEdgeIDs property.

This property is read-only.

Loop closure edges IDs, specified as a vector of edge IDs.

Object Functions

addRelativePoseAdd relative pose to pose graph
edgesEdges in pose graph
edgeConstraintsEdge constraints in pose graph
findEdgeIDFind edge ID of edge
nodesPoses of nodes in pose graph
optimizePoseGraphOptimize nodes in pose graph
removeEdgesRemove loop closure edges from graph
showPlot pose graph

Examples

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Optimize a pose graph based on the nodes and edge constraints. The pose graph used in this example is from the Intel Research Lab Dataset and was generated from collecting wheel odometry and a laser range finder sensor information in an indoor lab.

Load the Intel data set that contains a 2-D pose graph. Inspect the robotics.PoseGraph object to view the number of nodes and loop closures.

load intel-2d-posegraph.mat pg
disp(pg)
  PoseGraph with properties:

               NumNodes: 1228
               NumEdges: 1483
    NumLoopClosureEdges: 256
     LoopClosureEdgeIDs: [1x256 double]

Plot the pose graph with IDs off. Red lines indicate loop closures identified in the dataset.

title('Original Pose Graph')
show(pg,'IDs','off');

Optimize the pose graph. Nodes are adjusted based on the edge constraints and loop closures. Plot the optimized pose graph to see the adjustment of the nodes with loop closures.

updatedPG = optimizePoseGraph(pg);
figure
title('Updated Pose Graph')
show(updatedPG,'IDs','off');

References

[1] Grisetti, G., R. Kummerle, C. Stachniss, and W. Burgard. "A Tutorial on Graph-Based SLAM." IEEE Intelligent Transportation Systems Magazine. Vol. 2, No. 4, 2010, pp. 31–43. doi:10.1109/mits.2010.939925.

Extended Capabilities

Introduced in R2018a