Gabriel Oliver-Codina

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.

Optical Sensors and Methods for Underwater 3D Reconstruction

This paper presents a survey on optical sensors and methods for 3D reconstruction in underwater environments. The techniques to obtain range data have been listed and explained, together with the different sensor hardware that makes them possible. The literature has been reviewed, and a classification has been proposed for the existing solutions. New developments, commercial solutions and previous reviews in this topic have also been gathered and considered.

Underwater Laser-based Structured Light System for one-shot 3D reconstruction

A Laser-based Structured Light System (LbSLS) has been designed to perform underwater close-range 3D reconstructions even with high turbidity conditions and outperform conventional systems. The system uses a camera and a 532 nm green laser projector. The optical technique used is based on the projection of a pattern obtained placing a Diffractive Optical Element (DOE) in front of the laser beam. In the experiments described in this manuscript, the DOE used diffracts the laser beam in 25 parallel lines providing enough information in a single camera frame to perform a 3D reconstruction.

Inertial Sensor Self-Calibration in a Visually-Aided Navigation Approach for a Micro-AUV

This paper presents a new solution for underwater observation, image recording, mapping and 3D reconstruction in shallow waters. The platform, designed as a research and testing tool, is based on a small underwater robot equipped with a MEMS-based IMU, two stereo cameras and a pressure sensor. The data given by the sensors are fused, adjusted and corrected in a multiplicative error state Kalman filter (MESKF), which returns a single vector with the pose and twist of the vehicle and the biases of the inertial sensors (the accelerometer and the gyroscope). The inclusion of these biases in the state vector permits their self-calibration and stabilization, improving the estimates of the robot orientation. Experiments in controlled underwater scenarios and in the sea have demonstrated a satisfactory performance and the capacity of the vehicle to operate in real environments and in real time.

Global image signature for visual loop-closure detection

This work details a new method for loop-closure detection based on using multiple orthogonal projections to generate a global signature for each image of a video sequence. The new multi-projection function permits the detection of images corresponding to the same scene, but taken from different points of view. The signature generation process preserves enough information for robust loop-closure detection, although it transforms each image to a simple and compact representation. Thanks to these characteristics, a real-time operation is possible, even for long sequences with thousands of images. In addition, it has proved to work on very different scenarios without the need to change the parameters or to perform an onffline training stage, which makes it very independent on the environment and camera configuration. Results of an extensive set of experiments of the algorithm on several datasets, both indoors and outdoors and including underwater scenarios, are presented. Furthermore, an implementation, named HALOC, is available at a public repository as a C++ library for its use under the BSD license.

One-shot underwater 3D reconstruction

A one-shot sensor for underwater 3D reconstruction is presented and tested underwater in a water tank. The system is composed of a RGB CCD camera and a 532 nm green laser with a Diffractive Optical Element attached to it. The laser projects a pattern of parallel lines into the scene. The deformed pattern obtained in the camera frame is then processed to obtain a non-dense 3D point cloud that can be later used for autonomous manipulation and grasping, or for detailed mapping of textureless objects or scenarios.

I-AUV Docking and Panel Intervention at Sea

The use of commercially available autonomous underwater vehicles (AUVs) has increased during the last fifteen years. While they are mainly used for routine survey missions, there is a set of applications that nowadays can be only addressed by manned submersibles or work-class remotely operated vehicles (ROVs) equipped with teleoperated arms: the intervention applications. To allow these heavy vehicles controlled by human operators to perform intervention tasks, underwater structures like observatory facilities, subsea panels or oil-well Christmas trees have been adapted, making them more robust and easier to operate. The TRITON Spanish founded project proposes the use of a light-weight intervention AUV (I-AUV) to carry out intervention applications simplifying the adaptation of these underwater structures and drastically reducing the operational cost. To prove this concept, the Girona 500 I-AUV is used to autonomously dock into an adapted subsea panel and once docked perform an intervention composed of turning a valve and plugging in/unplugging a connector. The techniques used for the autonomous docking and manipulation as well as the design of an adapted subsea panel with a funnel-based docking system are presented in this article together with the results achieved in a water tank and at sea.

Evaluating the impact of sewage discharges on the marine environment with a lightweight AUV

Environmental studies that use small Autonomous Underwater Vehicles (AUVs) can survey wider and deeper areas, compared to traditional methods, at a reasonable cost. Thanks to the precise vehicle navigation systems, the data collected can be accurately geolocalized. Besides, lightweight vehicles can be deployed from the shore or from small boats and programmed by means of user-friendly graphical interfaces, thus reducing and simplifying the need of human resources and infrastructures. Based on such a technology, this paper presents a framework to assess the environmental impact of a marine sewage outfall set in the Bay of Palma (Mallorca, Spain). We report the results of the analysis of the images recorded in the course of six missions conducted with an AUV. The plan was designed after a microbiological analysis detected the presence of cyanobacteria in a sample of sand and water collected by scuba divers close to the sewer pipe mouth.