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Publications

Publications by Alfredo Martins

2019

Modeling and Control of Underwater Mine Explorer Robot UX-1

Authors
Suarez Fernandez, RAS; Grande, D; Martins, A; Bascetta, L; Dominguez, S; Rossi, C;

Publication
IEEE ACCESS

Abstract
This paper presents the design and experimental assessment of the control system for the UX-1 robot, a novel spherical underwater vehicle for flooded mine tunnel exploration. Propulsion and maneuvering are based on an innovative manifold system. First, the overall design concepts of the robot are presented. Then, a theoretical six degree-of-freedom (DOF) dynamic model of the system is derived. Based on the dynamic model, two control systems have been developed and tested, one based on the principle of nonlinear state feedback linearization and another based on a finite horizon linear quadratic regulator (LQR). A series of experimental tests have been carried out in a controlled environment to experimentally identify the complex parameters of the dynamic model. Furthermore, the two proposed controllers have been tested in underwater path tracking experiments designed to simulate navigation in mine tunnel environments. The experimental results demonstrated the effectiveness of both the proposed controllers and showed that the state feedback linearization controller outperforms the finite horizon LQR controller in terms of robustness and response time, while the LQR appears to be superior in terms of fall time.

2018

UXNEX N AUV perception system design and characterization

Authors
Martins, A; Almeida, J; Almeida, C; Silva, E;

Publication
2018 IEEE/OES AUTONOMOUS UNDERWATER VEHICLE WORKSHOP (AUV)

Abstract
This paper presents the perception system designed for the underwater mine exploration UNEXMIN robot. This autonomous underwater vehicle was designed in the context of the European 112020 ENEXIVIIN project to explore flooded underground mines The presented work addresses the sensor choice and placement options, the characterization of the system with results obtained in test tank and on field missions in mines. The perception software and computational architecture is also discussed with details on its distributed features. This perception system is comprised of one multibeam imaging/profiling sonar, one mechanically scanning sonar, digital cameras and a set of custom developed laser based structured light systems. The presented results from the Kaatiala mine (Finland) field trials and the Idrija mine tests (Slovenia) are discussed and allow for the performance analysis of the system.

2019

Real-Time LiDAR-based Power Lines Detection for Unmanned Aerial Vehicles

Authors
Azevedo, F; Dias, A; Almeida, J; Oliveira, A; Ferreira, A; Santos, T; Martins, A; Silva, E;

Publication
2019 19TH IEEE INTERNATIONAL CONFERENCE ON AUTONOMOUS ROBOT SYSTEMS AND COMPETITIONS (ICARSC 2019)

Abstract
The growing dependence of modern-day societies on electricity increases the importance of effective monitoring and maintenance of power lines. Endowing UAVs with the appropriate sensors for inspecting power lines, the costs and risks associated with the traditional foot patrol and helicopter-based inspections can be reduced. However, this implies the development of algorithms to make the inspection process reliable and autonomous. Visual methods are usually applied to locate the power lines and their components, but poor light conditions or a background rich in edges may compromise their results. To overcome those limitations, we propose to address the problem of power line detection and modeling based on LiDAR. A novel approach to the power line detection was developed, the PL2DM -Power Line LiDAR-based Detection and Modeling. It is based in a scan-by-scan adaptive neighbor minimalist comparison for all the points in a point cloud. The power line final model is obtained by matching and grouping several line segments, using their collinearity properties. Horizontally, the power lines are modeled as a straight line, and vertically as a catenary curve. The algorithm was validated with a real dataset, showing promising results both in terms of outputs and processing time, adding real-time object-based perception capabilities for other layers of processing.

2018

3D path planning methods for unmanned aerial vehicles in search and rescue scenarios

Authors
Dias, A; Fernandes, T; Almeida, J; Martins, A; Silva, E;

Publication
Human-Centric Robotics- Proceedings of the 20th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, CLAWAR 2017

Abstract
3D path planning with unmanned aerial vehicles in search and rescue scenarios is an important research area, due to the ability to explore damage areas that could be inaccessible for vehicles like ground robots. This paper presents two innovative real-time path planning algorithms based on PRM (Probabilistic Road Map) able to be implemented in UAV’s denoted by Grid Path Planning Roadmap Planning (GPRM) and the Particle Probabilistic Roadmap (PPRM). With the requirement of being implemented in a real search and rescue scenario like the EuRathlon competition, the GPRM method will produce a roadmap building step with obstacles inside a predefined grid while PPRM will follow a different approach by introducing an associated probability to each computed path in order to support the next sampling step path planning iteration. Both methods were evaluated and compared with the well known 3D path planning PRM in a search and rescue earthquake simulation environment developed in MORSE (Modular Open Robots Simulation Engine). © 2018 by World Scientific Publishing Co. Pte. Ltd.

2019

In situ real-time Zooplankton Detection and Classification

Authors
Geraldes, P; Barbosa, J; Martins, A; Dias, A; Magalhaes, C; Ramos, S; Silva, E;

Publication
OCEANS 2019 - MARSEILLE

Abstract
Zooplankton plays a key -role on Earth's ecosystem, emerging in the oceans and rivers in great quantities and diversity, making it an important and rather common topic on scientific studies. Given the numbers of different species it is not only necessary to study their numbers but also their classification. In this paper a possible solution for the zooplankton in situ detection and classification problem in real-time is proposed using a portable deep learning approach based on Convolutional Neural Networks deployed on INESC TEC's MarinEye system. For detection a Single Shot Detection model with MobileNet was used, and ZooplanktoNet for classification. System portability is guaranteed with the use of MovidiusTMNeural Compute Stick as the deep learning motor.

2019

Low Cost Underwater Acoustic Positioning System with a Simplified DoA Algorithm

Authors
Guedes, P; Viana, N; Silva, J; Amaral, G; Ferreira, H; Dias, A; Almeida, JM; Martins, A; Silva, EP;

Publication
OCEANS 2019 MTS/IEEE SEATTLE

Abstract
For the context of a mobile tracking system, an underwater acoustic positioning system was developed, using three hydrophones to compute the direction of an acoustic source relative to an Autonomous Surface Vehicle (ASV). The paper presents an algorithm for the Direction of Arrival (DoA) of an acoustic source, which allows to estimate its position. Preliminary results will be shown in this paper relative to the detection and identification (ID) of the acoustic sources, as well as an analysis of the proposed algorithm. The solution allows the position estimation of an acoustic source, which can be used in tracking solutions. The system can be applied in an ASV or fixed buoys, as long as the baseline's hydrophones are at equal angular distances. The main objective is to track targets with the DoA algorithm as well to estimate their position, improving what was done in [1].

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