Computation of the optimal relative pose between overlapping grid maps through discrepancy minimization

Grid maps are a common environment representation in mobile robotics. Many Simultaneous Localization and Mapping (SLAM) solutions divide the global map into submaps, forming some kind of graph or tree to represent the structure of the environment, while the metric details are captured in the submaps. This work presents a novel algorithm that is able to compute a physically feasible relative pose between two overlapping grid maps. Our algorithm can be used for correspondence search (data association), but also for integrating negative information in a unified way. This paper proposes a discrepancy measure between two overlapping grid maps and its application in a quasi Newton optimization algorithm, with the hypothesis that minimizing such discrepancy could provide useful information for SLAM. Experimental evidence is provided showing the high potential of the algorithm

Building maps of large environments using splines and geometric analysis

Recently, a novel solution to the Simultaneous Localization and Map building (SLAM) problem for complex indoor environments was presented, using a set of splines for describing the geometries detected by a laser range finder mounted on a mobile platform. In this paper, a method for exploiting the geometric information underlying in these maps in the data association process is described. The proposed approach uses graphs of relations between simple features extracted from the environment, and a bit encoded implementation for obtaining a maximum clique that relates observations with previously visited areas. This information is used to update the relative positions of a collage of submaps of limited size

A JOINT EFFORT OF SPEEDED-UP ROBUST FEATURES ALGORITHM AND A DISPARITY-BASED MODEL FOR 3D INDOOR MAPPING USING RGB-D DATA

In this paper, we present a method for 3D mapping of indoor environments using RGB-D data. The contribution of our proposed method is two-fold. First, our method exploits a joint effort of the speed-up robust features (SURF) algorithm and a disparity-to-plane model for a coarse-to-fine registration procedure. Once the coarse-to-fine registration task accumulates errors, the same features can appear in two different locations of the map. This is known as the loop closure problem. Then, the variance-covariance matrix that describes the uncertainty of transformation parameters (3D rotation and 3D translation) for view-based loop closure detection followed by a graph-based optimization are proposed to achieve a 3D consistent indoor map. To demonstrate and evaluate the effectiveness of the proposed method, experimental datasets obtained in three indoor environments with different levels of details are used. The experimental results shown that the proposed framework can create 3D indoor maps with an error of 11,97 cm into object space that corresponds to a positional imprecision around 1,5% at the distance of 9 m travelled by sensor

A bayesian approach to simultaneously recover camera pose and non-rigid shape from monocular images

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In this paper we bring the tools of the Simultaneous Localization and Map Building (SLAM) problem from a rigid to a deformable domain and use them to simultaneously recover the 3D shape of non-rigid surfaces and the sequence of poses of a moving camera. Under the assumption that the surface shape may be represented as a weighted sum of deformation modes, we show that the problem of estimating the modal weights along with the camera poses, can be probabilistically formulated as a maximum a posteriori estimate and solved using an iterative least squares optimization. In addition, the probabilistic formulation we propose is very general and allows introducing different constraints without requiring any extra complexity. As a proof of concept, we show that local inextensibility constraints that prevent the surface from stretching can be easily integrated. An extensive evaluation on synthetic and real data, demonstrates that our method has several advantages over current non-rigid shape from motion approaches. In particular, we show that our solution is robust to large amounts of noise and outliers and that it does not need to track points over the whole sequence nor to use an initialization close from the ground truth.Peer ReviewedPostprint (author's final draft

Qualitative localization using vision and odometry for path following in topo-metric maps

International audienceWe address the problem of navigation in topo- metric maps created by using odometry data and visual loop- closure detection. Based on our previous work [6], we present an optimized version of our loop-closure detection algorithm that makes it possible to create consistent topo-metric maps in real-time while the robot is teleoperated. Using such a map, the proposed navigation algorithm performs qualitative localization using the same loop-closure detection framework and the odometry data. This qualitative position is used to support robot guidance to follow a predicted path in the topo-metric map compensating the odometry drift. Compared to purely visual servoing approaches for similar tasks, our path-following algorithm is real-time, light (not more than two images per seconds are processed), and robust as odometry is still available to navigate even if vision information is absent for a short time. The approach has been validated experimentally with a Pioneer P3DX robot in indoor environments with embedded and remote computations

A tree parameterization for efficiently computing maximum likelihood maps using gradient descent

In 2006, Olson et al. presented a novel approach toaddress the graph-based simultaneous localization and mappingproblem by applying stochastic gradient descent to minimizethe error introduced by constraints. Together with multi-levelrelaxation, this is one of the most robust and efficient maximumlikelihood techniques published so far. In this paper, wepresent an extension of Olson's algorithm. It applies a novelparameterization of the nodes in the graph that significantlyimproves the performance and enables us to cope with arbitrarynetwork topologies. The latter allows us to bound the complexityof the algorithm to the size of the mapped area and not tothe length of the trajectory as it is the case with both previousapproaches. We implemented our technique and compared it tomulti-level relaxation and Olson's algorithm. As we demonstratein simulated and in real world experiments, our approachconverges faster than the other approaches and yields accuratemaps of the environment

Map point optimization in keyframe-based SLAM using covisibbility graph and information fusion

SLAM (do inglês Simultaneous Localization and Mapping) Monocular baseado em Keyframes é uma das principais abordagens de SLAM Visuais, usado para estimar o movimento da câmera juntamente com a reconstrução do mapa sobre frames selecionados. Estas técnicas representam o ambiente por pontos no mapa localizados em um espaço tri-dimensional, que podem ser reconhecidos e localizados no frame. Contudo, estas técnicas não podem decidir quando um ponto do mapa se torna um outlier ou uma informação obsoleta e que pode ser descartada, ou combinar pontos do mapa que correspondem ao mesmo ponto tri-dimensional. Neste trabalho, apresentamos um método robusto para manter um mapa refinado. Esta abordagem usa o grafo de covisibilidade e um algoritmo baseado na fusão de informações para construir um mapa probabilístico, que explicitamente modela medidas de outlier. Além disso, incorporamos um mecanismo de poda para reduzir informações redundantes e remover outliers. Desta forma, nossa abordagem gerencia a redução do tamanho do mapa, mantendo informações essenciais do ambiente. Finalmente, a fim de avaliar a performance do nosso método, ele foi incorporado ao sistema do ORB-SLAM e foi medido a acurácia alcançada em datasets publicamente disponíveis que contêm sequências de imagens de ambientes internos gravados com uma câmera monocular de mão.Keyframe-based monocular SLAM (Simultaneous Localization and Mapping) is one of the main visual SLAM approaches, used to estimate the camera motion together with the map reconstruction over selected frames. These techniques based on keyframes represent the environment by map points located in the three-dimensional space that can be recognized and located in the frames. However, many of these techniques cannot combine map points corresponding to the same three-dimensional point or detect when a map point becomes outlier and an obsolete information. In this work, we present a robust method to maintain a refined map that uses the covisibility graph and an algorithm based on information fusion to build a probabilistic map, which explicitly models outlier measurements. In addition, we incorporate a pruning mechanism to reduce redundant information and remove outliers. In this way our approach manages the map size maintaining essential information of the environment. Finally, in order to evaluate the performance of our method, we incorporate it into an ORB-SLAM system and measure the accuracy achieved on publicly available benchmark datasets which contain indoor images sequences recorded with a hand-held monocular camera