Publication type: Conferences

Vessel maintenance entails periodic visual inspections of internal and external parts of the hull in order to detect the typical defective situations affecting metallic structures, such as cracks, coating breakdown, corrosion, etc. The main goal of the EU-FP7 project MINOAS is the automation of the inspection process, currently undertaken by human surveyors, by means of a fleet of robotic agents. This paper overviews a Micro Aerial Vehicle (MAV) to be used as part of this fleet, and describes the control software approach that has been adopted, with special emphasis on self-localization and obstacle avoidance. Experimental results in this regard are included and discussed at the end of the paper.

In this paper different cascaded and multilevel topologies are compared for regenerative braking systems using supercapacitors (SC). It shows that the multilevel buck derived topology can beneficiate from both reduced voltage across the inductor and increased frequency to reduce the output inductance, even if there is the need for an input LC filter to reduce harmonic content in the SC. Also, the proposed control scheme is able to control the energy flow between SC and the DC bus, balancing the voltage in the SC banks. Experimental results verify the performance of the proposed converter and its control algorithm.

A visual odometer can estimate robot motion by tracking a set of invariant keypoints over a sequence of camera frames, at a computational cost that is roughly linear in the number of extracted keypoints. The leading literature suggests to extract all keypoints with a response value—e.g., a Laplacian or Hessian determinant—above a given threshold. We find that the number of image keypoints that pass a given threshold is highly variable between images, which is impractical for real time systems where motion needs to be estimated in constant time. Here we propose to extract a constant number of keypoints that have the highest response for their respective frame. To find the optimal number of extracted keypoints, we define a range of thresholds on odometer performance, and study how the number of image pairs for which a visual odometer passes the thresholds depends on the number of extracted keypoints. We find that the shapes of the resulting graphs are relatively invariant to the chosen threshold values and that for all threshold values the region where good odometer performance is balanced with computational efficiency is relatively small. We conclude that if odometer performance has to be weighed against computational cost, there is relatively little room for trade, and that a robust optimum can quickly and easily be found.

This paper proposes a novel approach to perform underwater Simultaneous Localization and Mapping (SLAM) using a Mechanically Scanned Imaging Sonar (MSIS). This approach starts by processing the MSIS data in order to obtain range scans while taking into account the robot motion. Then, the relative motions between consecutively gathered scans are stored in the state vector. Thus, the whole sequence of robot motions between gathered scans is used to perform SLAM using an Extended Kalman Filter (EKF). One of the novelties is that this sequence is not represented with respect to a world- fixed coordinate frame, but with respect to a coordinate frame locked to the robot. Thanks to this, EKF linearization errors are reduced. The experimental results in underwater environments validate the proposal comparing the new robocentric approach to the world-centric trajectory method.

Vessel maintenance entails periodic visual inspections of internal and external parts of the vessel hull in order to detect the typical defective situations affecting metallic structures, such as cracks, coating breakdown, corrosion, etc. The main goal of the EU-FP7 project MINOAS is the automation of the inspection process, currently undertaken by human surveyors, by means of a fleet of robotic agents. This paper overviews a UAV to be used as part of this fleet, and succinctly describes its control architecture as well as a self-localization solution for this vehicle. Promising experimental results are discussed in the experimental results section.