Guillem Vallicrosa

I-AUV docking and intervention in a subsea panel

While commercially available autonomous underwater vehicles (AUVs) are routinely used in survey missions, a new set of applications exist which clearly demand intervention capabilities: the maintenance of permanent underwater structures as well as the recovery of benthic stations or black-boxes are a few of them. These tasks are addressed nowadays using manned submersibles or work-class remotely operated vehicles (ROVs), equipped with teleoperated arms under human supervision. In the context of the TRITON Spanish funded project, a subsea panel docking and an intervention procedure are proposed. The light-weight intervention AUV (I-AUV) Girona 500 is used to autonomously dock into a subsea panel using a funnel-based docking method for passive accommodation. Once docked, an autonomous fixed-based manipulation system, which uses feedback from a digital camera, is used to turn a valve and plug/unplug a connector. The paper presents the techniques used for the autonomous docking and manipulation as well as how the adapted subsea panel has been designed to facilitate such operations.

Autonomous I-AUV Docking for Fixed-base Manipulation

Abstract While commercially available autonomous underwater vehicles (AUVs) are routinely used in survey missions, a new set of applications exist demanding intervention capabilities. This is the case, for instance, of the maintenance of permanent underwater observatories or submerged oil wells. These tasks, currently undertaken by remotely operated vehicles (ROVs), can be automated using intervention AUVs (I-AUVs) reducing their complexity and costs. The TRITON spanish funded project proposes the use of light I-AUV for autonomous intervention tasks, such as valve turning or connector pluging/unpluging, in adapted sub-sea infrastructures. To this aim, this paper presents the design and implementation of an I-AUV-friendly sub-sea docking panel, as well as the vision-based autonomous docking procedure for the Girona 500 lightweight I-AUV. The panel implements a funnel-based docking method for passive accommodation. It also includes a T valve and a custom designed hot stab connector. Once docked, the I-AUV and the panel become rigid and basic fixed-base manipulation strategies can be used for manipulation.

Online path planning for autonomous underwater vehicles in unknown environments

We present a framework for planning collision-free paths online for autonomous underwater vehicles (AUVs) in unknown environments. It is composed of three main modules (mapping, planning and mission handler) that incrementally explore the environment while solving start-to-goal queries. We use an octree-based representation of the environment and we extend the optimal rapidly-exploring random tree (RRT*) using concepts of anytime algorithms and lazy collision evaluation, thus including the capability to replan paths according to nearby obstacles perceived during the execution of the mission. To validate our approach, we plan paths for the SPARUS-II AUV, a torpedo-shaped vehicle performing autonomous missions in a 2-dimensional workspace. We demonstrate its feasibility with the SPARUS-II AUV in both simulation and real-world in-water trials.

Active Range-Only beacon localization for AUV homing

This paper presents a solution to the 3D Range-Only beacon localization problem using a Sum of Gaussians (SOG) filter together with an Active Localization method, which is based on the minimization of the beacon position uncertainty, in order to ensure the problem observability and a fast convergence. The method is applied to autonomously locate a subsea panel and home to it in order to establish visual contact to later launch a visual servoing based docking task. The method is demonstrated through field experiments in a harbor environment with an Autonomous Underwater Vehicle (AUV) including Ultra-Short Baseline (USBL) ground truth information.

Sum of gaussian single beacon range-only localization for AUV homing☆

Abstract Range-only measurements are extensively used in many Autonomous Underwater Vehicle (AUV) applications. These measurements do not depend on water quality and can be taken from long distances. This paper proposes two methods based on the Sum of Gaussian (SoG) filter, to solve the range-only localization problem for homing. The use of the SoG allows us to combine the benefits of both a Particle Filter (PF) and an Extended Kalman Filter (EKF) approach in a single filter. An Active Localization (AL) method is applied to the SoG to autonomously choose the best waypoints for autonomous convergence. Both the SoG filter and the AL are tested in a real scenario with an Intervention Autonomous Underwater Vehicle (I-AUV) and compared with a vision-based method to confirm localization.

Wireless HROV control with compressed visual feedback over an acoustic link

This paper presents the current state of the development of a Wireless HROV (Hybrid Remotely Operated Vehicle HROV), providing feedback of both, camera and telemetry data to the operator, over an acoustic communication link. This experiment is part of the MERBOTS Spanish national project (www.irs.uji.es/merbots). This work has as main objective the design of a bidirectional transport protocol for wireless teleoperation of an underwater robot using high level commands and a progressive image compression algorithm. Preliminary Hardware In the Loop results combining two S2CR 18/34 modems in a scenario with high level of multi-path, a freshwater pool, and the UWSim simulator are presented. Finally, a ROS-based network simulator that is still in an early stage of development is presented. This simulator will be useful for modeling high-level behavior of any communication device, and to improve high level protocols when the real modems are not available.

Realtime AUV Terrain Based Navigation with Octomap in a Natural Environment

This paper addresses the problems of Terrain Based Navigation (TBN) and Occupancy Grid Mapping for an Autonomous Underwater Vehicle (AUV). The two problems are solved using the same tools to make feasible in future works to implement a Simultaneous Localization and Mapping (SLAM). Realtime Occupancy Grid Mapping on the real vehicle Girona500 AUV is achieved by means of the Octomap library. The resulting map is later used for TBN with the parallelized execution of a Particle Filter making also use of the Octomap library to compare multibeam sonar ranges against the known map. The Occupancy Grid Mapping and the Particle filter are implemented as individual nodes in the vehicle’s software architecture in ROS. Tests were carried out in a dataset of a natural environment near the coast. Several parameters involving the Particle Filter (number of particles, number of beams, uncertainty of measurements) are studied. Finally, the results are compared with the dead reckoning obtained by the AUV and the USBL positions obtained from a surface boat.

H-SLAM: Rao-Blackwellized Particle Filter SLAM Using Hilbert Maps

Occupancy Grid maps provide a probabilistic representation of space which is important for a variety of robotic applications like path planning and autonomous manipulation. In this paper, a SLAM (Simultaneous Localization and Mapping) framework capable of obtaining this representation online is presented. The H-SLAM (Hilbert Maps SLAM) is based on Hilbert Map representation and uses a Particle Filter to represent the robot state. Hilbert Maps offer a continuous probabilistic representation with a small memory footprint. We present a series of experimental results carried both in simulation and with real AUVs (Autonomous Underwater Vehicles). These results demonstrate that our approach is able to represent the environment more consistently while capable of running online.

LOON-DOCK: AUV homing and docking for high-bandwidth data transmission

Persistent deployment of underwater assets holds the key to achieve consistent, long-term undersea monitoring. To advance in that direction, the LOON-DOCK project aims to demonstrate remote AUV operation and survey data transmission through the Internet using an underwater docking station. We present a funnel-shaped docking station equipped with a contactless high bandwidth link and the necessary equipment to enable autonomous homing and docking by combining acoustic and optical sensing. The proposed combination, using a range-only localization at far distances and a light beacon localization at short ranges ensures a reliable strategy enabled with low-cost equipment and minimal requirements on both the vehicle and the dock sides. Moreover, remote operation is demonstrated by integrating the system in a unified web interface to control underwater assets, thus allowing a user to operate the AUV remotely through Internet. The full system has been successfully validated with tests conducted in a harbor environment.

A Comparison of G2o Graph SLAM and EKF Pose Based SLAM with Bathymetry Grids

Abstract This paper address the Simultaneous Localization and Mapping (SLAM) problem of an AUV using bathymetric maps. The algorithm compounds swath profiles of the seafloor with DVL navigation(dead-reckoning) to build surface patches (3D point clouds). An initial guess of the location of these point clouds is known a priori by means of the dead-reckoning solution. Whenever there is a significant overlap of two or more point clouds, the corresponding surface patches are registered among themselves using a probabilistic ICP algorithm. The outcome of the registration procedure is a set of constrains defining the relative position of the overlapping surface patches. Next, these constrains are used to optimize a pose graph using the G2o optimizer. The results are compared against our prior EKF-pose-based SLAM solution. Our results suggest that a better performance is achieved using EKF global optimization with respect to the G2o graph-SLAM solution.