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Publications

2015

Towards Active Course Marks for Autonomous Sailing Competitions

Authors
Ferreira, P; Malheiro, B; Guedes, P; Silva, M;

Publication
Robotic Sailing 2014

Abstract
This paper describes the environmental monitoring / regatta beacon buoy under development at the Laboratory of Autonomous Systems (LSA) of the Polytechnic Institute of Porto. On the one hand, environmentalmonitoring of open water bodies in real or deferred time is essential to assess and make sensible decisions and, on the other hand, the broadcast in real time of position, water and wind related parameters allows autonomous boats to optimise their regatta performance. This proposal, rather than restraining the boats autonomy, fosters the development of intelligent behaviour by allowing the boats to focus on regatta strategy and tactics. The Nautical and Telemetric Application (NAUTA) buoy is a dual mode reconfigurable system that includes communications, control, data logging, sensing, storage and power subsystems. In environmental monitoring mode, the buoy gathers and stores data from several underwater and above water sensors and, in regatta mode, the buoy becomes an active course mark for the autonomous sailing boats in the vicinity. During a race, the buoy broadcasts its position, together with the wind and the water current local conditions, allowing autonomous boats to navigate towards and round the mark successfully. This project started with the specification of the requirements of the dual mode operation, followed by the design and building of the buoy structure. The research is currently focussed on the development of the modular, reconfigurable, open source-based control system. The NAUTA buoy is innovative, extensible and optimises the on board platform resources.

2015

Multifunctional Control of an NPC Converter for the Grid Integration of Renewable Energy Sources

Authors
Pouresmaeil, E; Shaker, HR; Jorgensen, BN; Shokridehaki, M; Rodrigues, EMG; Catalao, JPS;

Publication
2015 IEEE EINDHOVEN POWERTECH

Abstract
This paper presents a control method based on dynamic model of three-level neutral-point-clamped (NPC) voltage source converter (VSC) for integration of renewable energy sources (RESs) into the power grid. The proposed control method can provide continuous injection of active power besides the compensation of all reactive power and harmonic current components of loads through integration of RESs into the grid. Simulation results confirm a reduced total harmonic distortion (THD), increased power factor of the grid, and injection of maximum power of RESs to the grid. The proposed model is developed in Matlab/Simulink environment and emphasis is given to the challenges met during the modeling.

2015

Stability Analysis for Operation of DG Units in Smart Grids

Authors
Pouresmaeil, E; Shaker, HR; Mehrasa, M; Shokridehaki, MA; Rodrigues, EMG; Catalao, JPS;

Publication
2015 IEEE 5TH INTERNATIONAL CONFERENCE ON POWER ENGINEERING, ENERGY AND ELECTRICAL DRIVES (POWERENG)

Abstract
This paper presents a multifunction control strategy for the stable operation of Distributed Generation (DG) units during grid integration. The proposed control model is based on Direct Lyapunov Control (DLC) theory and provides a stable region for the appropriate operation of DG units during grid integration. Using DLC technique in DG technology can provide the continuous injection of maximum active power in fundamental frequency from the DG source to the grid, compensating all reactive power and harmonic current components of grid-connected loads through the integration of DG link into the grid. Application of this concept can guarantee to reduce the stress on the grid during the energy demand peak. Simulation results are presented to demonstrate the proficiency and performance of the proposed DLC technique in DG technology.

2015

How to combine different microsimulation tools to assess the environmental impacts of road traffic? Lessons and directions

Authors
Fontes, T; Pereira, SR; Fernandes, P; Bandeira, JM; Coelho, MC;

Publication
TRANSPORTATION RESEARCH PART D-TRANSPORT AND ENVIRONMENT

Abstract
In the last decades, traffic microsimulation platforms have a growing complexity allowing a detailed description of vehicle traffic dynamics in a second-by-second basis. However, to project spatially their outputs, some precautions must be followed. Therefore, we analyze some variables used in the microscopic traffic models which have a high impact on further applications, especially when a spatial projection is required. To assess these objectives, a microsimulation framework which includes traffic and emission models was defined to characterize traffic flows and to evaluate vehicular emissions. This general methodology was then applied in a European medium sized city using two scenarios: (i) considering a Lagrangian approach and (ii) using an Eulerian approach of the simulation road traffic platform. The Lagrangian approach shows that if we have long links (some hundred meters, e.g. >500 m), we lose the spatial detail on emissions. On the other hand, using the Eulerian approach to define very small links (some few meters, e.g. <30 m), a significant statistic representation of traffic dynamics, in that link, was not obtained, particularly in areas with low traffic flow. The latter situation can occur because the vehicle speed can be high enough that did not allow recording any information in that link, even considering a high time resolution analysis (second-by-second). Thus, a non-linear trend of the error is identified when such data are analyzed geographically. Accordingly, depending on the use of those microsimulation tools, we identify some best practices related with the traffic model design that must be followed to minimize those errors.

2015

Finite element analysis of pectus carinatum surgical correction via a minimally invasive approach

Authors
Neves, SC; Pinho, ACM; Fonseca, JC; Rodrigues, NF; Henriques Coelho, T; Correia Pinto, J; Vilaca, JL;

Publication
COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING

Abstract
Pectus carinatum (PC) is a chest deformity caused by a disproportionate growth of the costal cartilages compared to the bony thoracic skeleton, pulling the sternum towards, which leads to its protrusion. There has been a growing interest on using the 'reversed Nuss' technique as a minimally invasive procedure for PC surgical correction. A corrective bar is introduced between the skin and the thoracic cage and positioned on top of the sternum highest protrusion area for continuous pressure. Then, it is fixed to the ribs and kept implanted for about 2-3years. The purpose of this work was to (a) assess the stresses distribution on the thoracic cage that arise from the procedure, and (b) investigate the impact of different positioning of the corrective bar along the sternum. The higher stresses were generated on the 4th, 5th and 6th ribs backend, supporting the hypothesis of pectus deformities correction-induced scoliosis. The different bar positioning originated different stresses on the ribs' backend. The bar position that led to lower stresses generated on the ribs backend was the one that also led to the smallest sternum displacement. However, this may be preferred, as the risk of induced scoliosis is lowered.

2015

Integrated modeling of road environments for driving simulation

Authors
Campos, C; Leitao, JM; Coelho, AF;

Publication
GRAPP 2015 - 10th International Conference on Computer Graphics Theory and Applications; VISIGRAPP, Proceedings

Abstract
Virtual environments for driving simulations aimed to scientific purposes require three-dimensional road models that must obey to detailed standards of specification and realism. The creation of road models with this level of quality requires previous definition of the road networks and the road paths. Each road path is usually obtained through the dedicated work of roadway design specialists, resulting in a long time consuming process. The driving simulation for scientific purposes also requires a semantic description of all elements within the environment in order to provide the parameterization of actors during the simulation and the production of simulation reports. This paper presents a methodology to automatically generate road environments suitable to the implementation of driving simulation experiences. This methodology integrates every required step for modelling road environments, from the determination of interchanges nodes to the generation of the geometric and the semantic models. The human supervisor can interact with the model generation process at any stage, in order to meet every specific requirement of the experimental work. The proposed methodology reduces workload involved in the initial specification of the road network and significantly reduces the use of specialists for preparing the road paths of all roadways. The generated semantic description allows procedural placing of actors in the simulated environment. The models are suitable for conducting scientific work in a driving simulator. Copyright

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