Visual navigation has become a standard in robotic applications with the emergence of robust and versatile algorithms. In particular, Visual Odometry (VO) has proven to be the most reliable navigation solution for space missions to estimate an unmanned vehicle's motion and state. Lava Tubes exploration is one of the recent challenges in this field of applied robotics. VO in this scenario requires more robustness to poor lighting conditions while keeping a low computational cost. We propose investigating an indirect bi-monocular VO based on sliding-window optimization in such a context. It focuses on maintaining the sparsity of the problem while keeping the information of the marginalized frames to reduce the computational burden. Different sparse graph topologies are studied to encode information from the past and are evaluated on accuracy and computation load. The best method retained is then compared to state-of-the-art systems on real data under extreme illumination conditions and reaches similar accuracy results at a lower computational cost.

2D SLAM is useful for mobile robots that are constrained to a 2D plane, for example in a warehouse, simplifying calculations in respect to the 3D case. The use of an IMU in such a context can enrich the estimation and make it more robust. In this paper we reformulate the IMU preintegration widely used in 3D problems for the 2D case, making use of Lie Theory. The Lie theory based formalization, first derived for a perfectly horizontal plane, allows us to easily extend it to problems where the plane is not orthogonal to the gravity vector. We implement the theory in a factor graph based estimation library, and carry out experiments to validate it on a mobile platform. Two experiments are carried out; on a horizontal and a sloped environment, and the sensor data is processed using our two 2D methods and a state-of-the-art 3D method.

Localization is the key perceptual process closing the loop of autonomous navigation, allowing self-driving vehicles to operate in a deliberate way. To ensure robust localization, autonomous vehicles have to implement redundant estimation processes, ideally independent in terms of the underlying physics behind sensing principles. This paper presents a stereo radar odometry system, which can be used as such a redundant system, complementary to other odometry estimation processes, providing robustness for long-term operability. The presented work is novel with respect to previously published methods in that it contains: (i) a detailed formulation of the Doppler error and its associated uncertainty; (ii) an observability analysis that gives the minimal conditions to infer a 2D twist from radar readings; and (iii) a numerical analysis for optimal vehicle sensor placement. Experimental results are also detailed that validate the theoretical insights.

We propose a novel method for robotic exploration that evaluates paths that minimize both the joint path and map entropy per meter traveled. The method uses Pose SLAM to update the path estimate, and grows an RRT* tree to generate the set of candidate paths. This action selection mechanism contrasts with previous appoaches in which the action set was built heuristically from a sparse set of candidate actions. The technique favorably compares agains the classical frontier-based exploration and other Active Pose SLAM methods in simulations in a common publicly available dataset.

Industrial environments are rarely static and often their configuration is continuously changing due to the material transfer flow. This is a major challenge for infrastructure free localization systems. In this paper we address this challenge by introducing a localization approach that uses a dual-timescale approach. The proposed approach - Dual-Timescale Normal Distributions Transform Monte Carlo Localization (DT-NDT-MCL) - is a particle filter based localization method, which simultaneously keeps track of the pose using an apriori known static map and a short-term map. The short-term map is continuously updated and uses Normal Distributions Transform Occupancy maps to maintain the current state of the environment. A key novelty of this approach is that it does not have to select an entire timescale map but rather use the best timescale locally. The approach has real-time performance and is evaluated using three datasets with increasing levels of dynamics. We compare our approach against previously proposed NDT-MCL and commonly used SLAM algorithms and show that DT-NDT-MCL outperforms competing algorithms with regards to accuracy in all three test cases.

Abstract — We propose a method for the computation of entropy decrease in C-space. These estimates are then used to evaluate candidate exploratory trajectories in the context of autonomous mobile robot mapping. The method evaluates both map and path entropy reduction and uses such estimates to compute trajectories that maximize coverage whilst min-imizing localization uncertainty, hence reducing map error. Very efficient kernel convolution mechanisms are used to evaluate entropy reduction at each sensor ray, and for each possible robot position and orientation, taking frontiers and obstacles into account. In contrast to most other exploration methods that evaluate entropy reduction at a small number of discrete robot configurations, we do it densely for the entire C-space. The computation of such dense entropy reduction maps opens the window to new exploratory strategies. In this paper we present two such strategies. In the first one we drive exploration through a gradient descent on the entropy decrease field. The second strategy chooses maximal entropy reduction configurations as candidate exploration goals, and plans paths to them using RRT*. Both methods use PoseSLAM as their estimation backbone, and are tested and compared with classical frontier-based exploration in simulations using common publicly available datasets. I.