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This paper explores the impact that landmark parametrization has in the performance of monocular, EKFbased, 6-DOF simultaneous localization and mapping (SLAM) in the context of undelayed landmark initialization.Undelayed initialization in monocular SLAM challenges EKF because of the combination of non-linearity with the large uncertainty associated with the unmeasured degrees of freedom. In the EKF context, the goal of a good landmark parametrization is to improve the model's linearity as much Electronic supplementary material The online version of this article (as possible, improving the filter consistency, achieving robuster and more accurate localization and mapping.This work compares the performances of eight different landmark parametrizations: three for points and five for straight lines. It highlights and justifies the keys for satisfactory operation: the use of parameters behaving proportionally to inverse-distance, and landmark anchoring. A unified EKF-SLAM framework is formulated as a benchmark for points and lines that is independent of the parametrization used. The paper also defines a generalized linearity index suited for the EKF, and uses it to compute and compare the degrees of linearity of each parametrization. Finally, all eight parametrizations are benchmarked employing analytical tools (the linearity index) and statistical tools (based on Monte Carlo error and consistency analyses), with simulations and real imagery data, using the standard and the robocentric EKF-SLAM formulations.

Most solutions to the SLAM problem in robotics have utilized Range and Bearing sensors as the provided perception data is easy to incorporate, allowing immediate landmark initialization. This is not the case when using Bearing-Only information because the distance to the perceived landmarks is not directly provided. A whole estimate of a landmark position will only be possible via a set of measurements taken from different points of view. The vast majority of contributions to this problem utilize a parallel task to get this estimate, and hence the landmark initialization is delayed. We give a new insight to the problem and present a method to avoid this delay by initializing the whole ray that defines the direction of the landmark. We utilize a minimal and computationally efficient form to represent this ray and a new strategy for the subsequent updates. Simulations have been carried out to validate the proposed algorithms.

Abstract-This article presents a bearing only 3D SLAM algorithm which has the same complexity and optimality as the usual extended kalman filter used in classical SLAM. We especially focus on the landmark initialization process, which relies on visual point features tracked in the sequence of acquired images: a probabilistic approach to estimate their parameters is presented. This induces a particular structure of the filter architecture, in which are memorized a set of past robot poses. Simulations are made to compare the influence of some parameters required by our approach, and results with an indoor robot and an airship are presented.

The challenge in the DARPA Learning Applied to Ground Robots (LAGR) project is to autonomously navigate a small robot using stereo vision as the main sensor. At the end of three years, the system we developed outperformed all 9 other teams in final blind tests over previously-unseen terrain. In this paper we describe the system, as well as the two learning techniques that led to this success: online path learning and map reuse.

This paper addresses the problem of autonomous servoing an unmanned redundant aerial manipulator using computer vision. The over-actuation of the system is exploited by means of a hierarchical control law which allows to prioritize several tasks during flight. We propose a safety related primary task to avoid possible collisions. As a secondary task we present an uncalibrated image-based visual servo strategy to drive the arm end-effector to a desired position and orientation using a camera attached to it. In contrast to previous visual-servo approaches, a known value of camera focal length is not strictly required. To further improve flight behavior we hierarchically add one task to reduce dynamic effects by vertically aligning the arm center of gravity to the multirotor gravitational vector, and another one that keeps the arm close to a desired configuration of high manipulability and avoiding arm joint limits. The performance of the hierarchical control law, with and without activation of each of the tasks, is shown in simulations and in real experiments confirming the viability of such prioritized control scheme for aerial manipulation

This article presents a new open-source C++ implementation to solve the SLAM problem, which is focused on genericity, versatility and high execution speed. It is based on an original object oriented architecture, that allows the combination of numerous sensors and landmark types, and the integration of various approaches proposed in the literature. The system capacities are illustrated by the presentation of an inertial/vision SLAM approach, for which several improvements over existing methods have been introduced, and that copes with very high dynamic motions. Results with a hand-held camera are presented.Comment: 10 page

This paper presents 6-DOF monocular EKF-SLAM with undelayed initialization using linear landmarks with extensible endpoints, based on the Plücker parametrization. A careful analysis of the properties of the Plücker coordinates, defined in the projective space P 5 , permits their direct usage for undelayed initialization. Immediately after detection of a segment in the image, a Plücker line is incorporated in the map. A single Gaussian pdf includes inside its 2-sigma region all possible lines given the observed segment, from arbitrarily close up to the infinity range, and in any orientation. The lines converge to stable 3D configurations as the moving camera gathers observations from new viewpoints. The line's endpoints, maintained out of the map, are constantly retro-projected from the image onto the line's local reference frame. An extendingonly policy is defined to update them. We validate the method via Monte Carlo simulations and with real imagery data.