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Geometric distortion associated with underwater flat port housings considerably affects the accuracy of scene depth and visual pose estimation. To compensate for this, a new solution for the forward projection is proposed based on the refractive camera model and Taylor expansion. This allows for an easy integration of the flat refractive camera model into non-linear optimization problems like bundle...
Underwater structures like oil and gas production systems, ship hulls or the foundations of buildings, piers and offshore wind facilities have to be regularly inspected to evaluate the state of the structure and to plan future interventions for repair and maintenance. These inspections are currently done by remotely operated vehicles (ROVs) or by divers but they are time-consuming, expensive and need...
In this paper we describe a new approach to deal with dynamic distortions of the ambient magnetic field often leading to errors in orientation estimation in confined unmanned underwater vehicles. In such systems, the space to mount magnetometer sensors is strictly limited and the sensors are often in the vicinity of distortion sources like ferromagnetic material, sonar transducers or strong electric...
Currently the inspection of industrial underwater structures is performed by remotely operated vehicles or by divers. Since the number of underwater structures keeps growing, e.g. due to new oil and gas fields or offshore wind farms, the need for a constantly available method to inspect these structures arises. The FlatFish project is an initiative of BG Group Brazil and the Brazilian Institute of...
To control any kind of unmanned underwater vehicle (UUV) it is important to know the dynamic model of the system. Creating the model itself is only the first step, the second is identifying the model's parameters. Due to the nonlinear and coupled characteristics of UUVs this is a complex and operationally demanding task. Several methods to identify the model parameters have been published in recent...
Sensing of environment geometry and texture is a key requirement for mobile robotic systems. In the underwater domain, difficult environmental conditions restrict the applicability of many existing methods for 3D sensing. A new method is proposed, which uses a visible laser line projected onto a monocular camera image to perform 3D scene reconstruction. The method fuses Structured Light with Structure...
This paper presents an evaluation of artificial fiducial markers in underwater environments. Due to the readily availabe code, the ARToolKit, AprilTags and ArUco marker systems are chosen for this purpose. The experiments are conducted in a tank equipped with a 3D gantry robot and a roll-tilt sensor head that allows to move the camera with millimeter precision. The markers are compared with each other...
The aim of this work is to identify the unknown physical parameters of an underwater vehicle in 3 DOF (surge, sway and yaw) using on-board sensors. The identified dynamic model is used for analysing and understanding the vehicle which operates at low speeds. The identification method used here is based on an approach described by Indiveri [1] and similar methods have also been employed by Ridao, et...
This paper presents the conceptual idea and a developed prototype of a docking system for a hovering AUV (Autonomous Underwater Vehicle). The presented docking system passively assists the vehicle's docking procedure by guiding it into a defined position, where it is mechanically locked in place by one of the station's actuators. In its final position the docking system provides an electrical power...
The AUV DAGON was designed as a vehicle for algorithm evaluation and visual mapping. Since its initial launching in early 2010 two years of experiments and experience with the vehicle have passed. This paper will give an overview of the work with the AUV DAGON and highlight the scientific experiments conducted with it, concluding with a “lessons learned” section with important modifications and ideas...
Robotic systems for outdoor applications can play an important role in the future. Tasks like exploration, surveillance or search and rescue missions benefit greatly from increased autonomy of the available systems. Outdoor environments and their high complexity pose a special challenge for existing autonomous behaviour technologies in robots. Some of these challenges in the area of navigation, plan...
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