00001 /* 00002 * Copyright 2016 The Cartographer Authors 00003 * 00004 * Licensed under the Apache License, Version 2.0 (the "License"); 00005 * you may not use this file except in compliance with the License. 00006 * You may obtain a copy of the License at 00007 * 00008 * http://www.apache.org/licenses/LICENSE-2.0 00009 * 00010 * Unless required by applicable law or agreed to in writing, software 00011 * distributed under the License is distributed on an "AS IS" BASIS, 00012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 00013 * See the License for the specific language governing permissions and 00014 * limitations under the License. 00015 */ 00016 00017 #ifndef CARTOGRAPHER_MAPPING_INTERNAL_2D_SCAN_MATCHING_REAL_TIME_CORRELATIVE_SCAN_MATCHER_2D_H_ 00018 #define CARTOGRAPHER_MAPPING_INTERNAL_2D_SCAN_MATCHING_REAL_TIME_CORRELATIVE_SCAN_MATCHER_2D_H_ 00019 00020 // This is an implementation of the algorithm described in "Real-Time 00021 // Correlative Scan Matching" by Olson. 00022 // 00023 // The correlative scan matching algorithm is exhaustively evaluating the scan 00024 // matching search space. As described by the paper, the basic steps are: 00025 // 00026 // 1) Evaluate the probability p(z|xi, m) over the entire 3D search window using 00027 // the low-resolution table. 00028 // 2) Find the best voxel in the low-resolution 3D space that has not already 00029 // been considered. Denote this value as Li. If Li < Hbest, terminate: Hbest is 00030 // the best scan matching alignment. 00031 // 3) Evaluate the search volume inside voxel i using the high resolution table. 00032 // Suppose the log-likelihood of this voxel is Hi. Note that Hi <= Li since the 00033 // low-resolution map overestimates the log likelihoods. If Hi > Hbest, set 00034 // Hbest = Hi. 00035 // 00036 // This can be made even faster by transforming the scan exactly once over some 00037 // discretized range. 00038 00039 #include <iostream> 00040 #include <memory> 00041 #include <vector> 00042 00043 #include "Eigen/Core" 00044 #include "cartographer/mapping/2d/grid_2d.h" 00045 #include "cartographer/mapping/internal/2d/scan_matching/correlative_scan_matcher_2d.h" 00046 #include "cartographer/mapping/proto/scan_matching/real_time_correlative_scan_matcher_options.pb.h" 00047 00048 namespace cartographer { 00049 namespace mapping { 00050 namespace scan_matching { 00051 00052 // An implementation of "Real-Time Correlative Scan Matching" by Olson. 00053 class RealTimeCorrelativeScanMatcher2D { 00054 public: 00055 explicit RealTimeCorrelativeScanMatcher2D( 00056 const proto::RealTimeCorrelativeScanMatcherOptions& options); 00057 00058 RealTimeCorrelativeScanMatcher2D(const RealTimeCorrelativeScanMatcher2D&) = 00059 delete; 00060 RealTimeCorrelativeScanMatcher2D& operator=( 00061 const RealTimeCorrelativeScanMatcher2D&) = delete; 00062 00063 // Aligns 'point_cloud' within the 'grid' given an 00064 // 'initial_pose_estimate' then updates 'pose_estimate' with the result and 00065 // returns the score. 00066 double Match(const transform::Rigid2d& initial_pose_estimate, 00067 const sensor::PointCloud& point_cloud, const Grid2D& grid, 00068 transform::Rigid2d* pose_estimate) const; 00069 00070 // Computes the score for each Candidate2D in a collection. The cost is 00071 // computed as the sum of probabilities or normalized TSD values, different 00072 // from the Ceres CostFunctions: http://ceres-solver.org/modeling.html 00073 // 00074 // Visible for testing. 00075 void ScoreCandidates(const Grid2D& grid, 00076 const std::vector<DiscreteScan2D>& discrete_scans, 00077 const SearchParameters& search_parameters, 00078 std::vector<Candidate2D>* candidates) const; 00079 00080 private: 00081 std::vector<Candidate2D> GenerateExhaustiveSearchCandidates( 00082 const SearchParameters& search_parameters) const; 00083 00084 const proto::RealTimeCorrelativeScanMatcherOptions options_; 00085 }; 00086 00087 } // namespace scan_matching 00088 } // namespace mapping 00089 } // namespace cartographer 00090 00091 #endif // CARTOGRAPHER_MAPPING_INTERNAL_2D_SCAN_MATCHING_REAL_TIME_CORRELATIVE_SCAN_MATCHER_2D_H_