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Topological maps based on graphs of planar regions
E. Montijano and C. Sagüés
DIIS-I3A University of Zaragoza (Spain)
IROS - 2009
Topological maps based on graphs of planar regions- IROS-2009
OUTLINE
• MOTIVATION
• SEGMENTATION OF PLANES
• CREATION OF THE TOPOLOGICAL MAPS
• EXPERIMENTAL RESULTS
• CONCLUSIONS
2
• Motivation• Segmentation• Topological Maps• Experimental Results
Topological maps based on graphs of planar regions- IROS-2009
MOTIVATION
3
• Motivation• Segmentation• Topological Maps• Experimental Results
• Visual sensors provide a lot of information
• Information must be arranged• Useful for the robots• Understandable by the humans
• Hierarchical structures with images work well but• Redundant information (features repeated)• Complex structure
• In man-made environments there is abundance of planes• Easy for humans to recognize• Have been used in many robotic applications Navigation [Courbon 08] Camera calibration [Menudet 07]Visual servoing [Lopez-Nicolas 07]
Topological maps based on graphs of planar regions- IROS-2009
4
• Motivation• Segmentation• Topological Maps• Experimental Results
In order to use planar regions from images
• Planar regions must be extracted
TRIPLE MATCHING APPROACH TO EXTRACT ALL THE PLANES SEEN IN A SEQUENCE OF IMAGES
• Planar regions must be sorted
EFFICIENT TOPOLOGICAL MAP CONSTRUCTION BASED ON A GRAPH OF PLANAR REGIONS
CONTRIBUTIONS
Topological maps based on graphs of planar regions- IROS-2009
OUTLINE
5
• MOTIVATION
• SEGMENTATION OF PLANES
• CREATION OF THE TOPOLOGICAL MAPS
• EXPERIMENTAL RESULTS
• CONCLUSIONS
• Segmentation• Topological Maps• Experimental Results• Conclusions
Topological maps based on graphs of planar regions- IROS-2009
TRIPLE MATCHING (I)
6
• Initial extraction of planes in I1 and I2Homographies with DLT+RANSAC
• No information about rotation, translation or calibration
• Features close to each other are chosen as hypotheses
• Segmentation• Topological Maps• Experimental Results• Conclusions
Starting with a sequence of images I1,…, In
• First image where the plane is seen is the reference for the plane
Topological maps based on graphs of planar regions- IROS-2009
• Matches belonging to the plane are chosen
• ω is increased and K reduced
• The homography with respect to the reference image is also computed
• The homography is used to localize more features in the plane
7
• Segmentation• Topological Maps• Experimental Results• Conclusions
TRIPLE MATCHING (II)
For any existing plane:
Topological maps based on graphs of planar regions- IROS-2009
8
• Segmentation• Topological Maps• Experimental Results• Conclusions
• New planes are extracted using the remaining matches
• Process is repeated recursively for all the images
TRIPLE MATCHING (III)
• Planes that are no longer seen are “closed”• They are not considered in the matching process anymore
Topological maps based on graphs of planar regions- IROS-2009
9
• Segmentation• Topological Maps• Experimental Results• Conclusions
• Multi-plane constraints make the process more robust
• Test the eigenvalues of the homologies [Sagüés 06]• Two eigenvalues equal to 1• One eigenvalue different than 1
CONSTRAINTS BETWEEN PLANES
• Test is image-based
Topological maps based on graphs of planar regions- IROS-2009
OUTLINE
10
• MOTIVATION
• SEGMENTATION OF PLANES
• CREATION OF THE TOPOLOGICAL MAPS
• EXPERIMENTAL RESULTS
• CONCLUSIONS
• Segmentation• Topological Maps• Experimental Results• Conclusions
Topological maps based on graphs of planar regions- IROS-2009
• The planes previously extracted are sorted in a hierarchical structure
• A graph, , A is the adjacency matrix of • Vertices represent planes in the sequence• Edges mean co-visibility between planes
•
• The matrix is symmetric• There are no self-loops
GRAPH OF PLANES
11
• Segmentation• Topological Maps• Experimental Results• Conclusions
Topological maps based on graphs of planar regions- IROS-2009
12
• Segmentation• Topological Maps• Experimental Results• Conclusions
ADDITION OF PLANES
• One plane is formally added to the graph
• Each plane is represented by• Identifiers of the images where it appeared (one reference)• Features that belong to the plane• Homographies
• The process is done simultaneously with the extraction
Topological maps based on graphs of planar regions- IROS-2009
13
• Segmentation• Topological Maps• Experimental Results• Conclusions
FUSION OF PLANES
• Planes can leave the field of view and enter again later
• The planes would be twice in the graph
• After the creation of the graph some planes may be fused (loop closure)
• Try to compute homographies between planes not co-visible
• If an homography is computed then both planes are the same,Fusion of the planes is done by
Topological maps based on graphs of planar regions- IROS-2009
14
• Segmentation• Topological Maps• Experimental Results• Conclusions
OVERVIEW OF THE METHOD
Topological maps based on graphs of planar regions- IROS-2009
OUTLINE
15
• MOTIVATION
• SEGMENTATION OF PLANES
• CREATION OF THE TOPOLOGICAL MAPS
• EXPERIMENTAL RESULTS
• CONCLUSIONS
• Segmentation• Topological Maps• Experimental Results• Conclusions
Topological maps based on graphs of planar regions- IROS-2009
EXPERIMENTAL RESULTS
16
• Segmentation• Topological Maps• Experimental Results• Conclusions
• Indoor sequence
Topological maps based on graphs of planar regions- IROS-2009
17
• Segmentation• Topological Maps• Experimental Results• Conclusions
• Outdoor sequence
EXPERIMENTAL RESULTS
Topological maps based on graphs of planar regions- IROS-2009
OUTLINE
18
• MOTIVATION
• SEGMENTATION OF PLANES
• CREATION OF THE TOPOLOGICAL MAPS
• EXPERIMENTAL RESULTS
• CONCLUSIONS
• Segmentation• Topological Maps• Experimental Results• Conclusions
Topological maps based on graphs of planar regions- IROS-2009
CONCLUSIONS
19
• Planar regions are useful for robots and understandable for humans
• New triple matching technique to extract the planar regions from a sequence of images has been proposed
• The planar regions have been sorted in a topological map reducing the size with respect to maps built just from images
• Segmentation• Topological Maps• Experimental Results• Conclusions
Topological maps based on graphs of planar regions- IROS-2009
20
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MORE INFO IN http://webdiis.unizar.es/~edumonti/