A layered simultaneous localization and mapping(SLAM) approach for building spatial hierarchical maps is proposed in situations that obstacles,environmental sensors and robot poses are all unknown in large-scale environments. Firstly,a two-layered environmental model is established,which is composed of a submap layer and a topological node layer. Then the perception information of the environmental sensors is employed to assist the online creation and update of submaps local coordinate framework.While building the topological structure,the coupling summation equation is utilized to compute the relative positions between nodes.Based on the loop-closure detection result,the weighted scan matching algorithm and the relaxation algorithm are introduced to optimize the topological structure,which ensures global consistency of the map. Experimental results validate the feasibility and effectiveness of the approach.
 Dellaert F,Kaess M.Square root SAM:Simultaneous localization and mapping via square root information smoothing[J]. Intemational Journal of Robotics Research,2006,25(12):1181-1203.
 Montemerlo M.FastSLAM:A factored solution to the simultaneous localization and mapping problem with unknown data association[D]. Pittsburgh,PA,USA:Robotics Institute,Carnegie Mellon University,2003.
 Grisetti G,Stachniss C,Burgard W.Improved techniques for grid mapping with Rao-Blackwellized particle filters[J]. IEEE Transactions on Robotics,2007,23(1):34-46.
 Estrada C,Neira J,Tard6s J D.Hierarchical SLAM:Real-time accurate mapping of large environments[J]. IEEE Transactions on Robotics,2005,21(4):588-596.
 Bosse M,Newman P M,Leonard J,et al.An atlas framework for scalable mapping[C]//Intemational Conference on Robotics and Automation.Piscataway,NJ,USA:IEEE,2003:1899-1906.
 Tard6s J D,Neira J,Newman P M,et al.Robust mapping and localization in indoor environments using sonar data[J]. International Journal of Robotics Research,2002,21(4):311-330.
 Clemente L A,Davison A,Reid I,et al.Mapping large loops with a single hand-held camera[M]//Sukhatme G S,Schaal S,Burgard W,et al(Editor).Robotics:Science and Systems.Cambridge,MA,USA:MIT Press,2007.
 Leonard J J,Feder H J S.Decoupled stochastic mapping[R]. Cambridge,MA,USA:MIT Press,2001.
 Ho K L,Newman P M.Loop closure detection in SLAM by combining visual and spatial appearance[J]. Robotics and Autonomous Systems,2006,54(9):740-749.
 Pfister S T,Kreichbaum K L,Roumeliotis S I,et al.Weighted range sensor matching algorithms for mobile robot displacement estimation[C]//IEEE International Conference on Robotics and Automation.Piscataway,NJ,USA:IEEE,2002:1667-1674.
 Schleicher D,Bergasa L M,Ocana M,et al.Real-time hierarchical stereo visual SLAM in large-scale environments[J]. Robotics and Autonomous Systems,2010,58(8):991-1002.
 Lowe D G.Object recognition from local scale-invariant features[C]//Intemational Conference on Computer Vision.Piscataway,NJ,USA:IEEE,1999:1150-1157.
 Liang Z W,Ma X D,Dai X Z.Information-theoretic approaches based on sequential Monte Carlo to collaborative distributed sensors for mobile robot localization[J]. Journal of Intelligent and Robotic Systems,2008,52(2):157-174.
 Ranganathan A,Dellaert F,Bayesian surprise and landmark detection[C]//IEEE International Conference on Robotics and Automation.Piscataway,NJ,USA:IEEE,2009:2017-2023.