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Publicações

Publicações por Rui Esteves Araujo

2016

Indoor Global Localisation in Anchor-based Systems using Audio Signals

Autores
Moutinho, J; Freitas, D; Araujo, RE;

Publicação
JOURNAL OF NAVIGATION

Abstract
This paper presents a method that allows mobile devices to be globally self-localised in indoor localisation systems by transmitting to them data from position reference anchors. The objective is to establish a reliable one-way down-link communication through signals used in the localisation process in a typically strong fading and multipath channel environment. This is accomplished by using signal processing techniques, including coding and forward error correction, to transmit data using a specific transmission control protocol. Experimental results, using audio as the signal between anchors and the mobile device, demonstrate successful data transmission in realistic scenarios like a common noisy and reverberant room. Spread spectrum noise-like masked signals 49 dB below background noise were sufficient to attain correct data reception at four metres distance between a loudspeaker anchor and a mobile device's microphone.

2014

Influence of Li-ion Battery Models in the Sizing of Hybrid Storage Systems with Supercapacitors

Autores
Pinto, C; Barreras, JV; de Castro, R; Schaltz, E; Andreasen, SJ; Araujo, RE;

Publicação
2014 IEEE VEHICLE POWER AND PROPULSION CONFERENCE (VPPC)

Abstract
This paper presents a comparative study of the influence of different aggregated electrical circuit battery models in the sizing process of a hybrid energy storage system (ESS), composed by Li-ion batteries and supercapacitors (SCs). The aim is to find the number of cells required to propel a certain vehicle over a predefined driving cycle. During this process, three battery models will be considered. The first consists in a linear static zeroeth order battery model over a restricted operating window. The second is a non-linear static model, while the third takes into account first-order dynamics of the battery. Simulation results demonstrate that the adoption of a more accurate battery model in the sizing of hybrid ESSs prevents over-sizing, leading to a reduction in the number of cells of up to 29%, and a cost decrease of up to 10%.

2018

Modulation Strategy for a Single-Stage Bidirectional and Isolated AC-DC Matrix Converter for Energy Storage Systems

Autores
Varajao, D; Araujo, RE; Miranda, LM; Lopes, JAP;

Publicação
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS

Abstract
This paper presents a new modulation and control strategies for the high-frequency link matrix converter (HFLMC). The proposed method aims to achieve controllable power factor in the grid interface as well as voltage and current regulation for a battery energy storage device. The matrix converter (MC) is a key element of the system, since it performs a direct ac to ac conversion between the grid and the power transformer, dispensing the traditional dc-link capacitors. Therefore, the circuit volume and weight are reduced and a longer service life is expected when compared with the existing technical solutions. A prototype was built to validate the mathematical analysis and the simulation results. Experimental tests developed in this paper show the capability of controling the grid currents in the synchronous reference frame in order to provide grid services. Simultaneously, the battery current is well regulated with small ripple, which makes this converter ideal for battery charging of electric vehicles and energy storage applications.

2015

A novel BEV concept based on fixed and swappable li-ion battery packs

Autores
Barreras, JV; Pinto, C; de Castro, R; Schaltz, E; Andreasen, SJ; Rasmussen, PO; Araujo, RE;

Publicação
2015 TENTH INTERNATIONAL CONFERENCE ON ECOLOGICAL VEHICLES AND RENEWABLE ENERGIES (EVER)

Abstract
In this paper a novel battery electric vehicle (BEV) concept based on a small fixed and a big swappable li-ion battery pack is proposed in order to achieve: longer range, lower initial purchase price and lower energy consumption at short ranges. For short ranges the BEV is only powered by the relatively small fixed battery pack, without the large swappable battery pack. In this way the mass of the vehicle is reduced and therefore the energy consumed per unit distance is improved. For higher ranges the BEV is powered by both battery packs. This concept allows the introduction of subscription-based ownership models to distribute the cost of the large battery pack over the vehicle lifetime. A methodology is proposed for the analysis and evaluation of the proposed concept in comparison with a direct owned non swappable single pack BEV, proving that significant improvements on city fuel economy (up to 20 %) and economic benefits are achievable under several scenarios. These results encourage further study of battery swapping service plans and energy management strategies.

2014

Assisted Assignment of Automotive Safety Requirements

Autores
Azevedo, LD; Parker, D; Walker, M; Papadopoulos, Y; Araujo, RE;

Publicação
IEEE SOFTWARE

Abstract
ISO 26262, a functional-safety standard, uses Automotive Safety Integrity Levels (ASILs) to assign safety requirements to automotive-system elements. System designers initially assign ASILs to system-level hazards and then allocate them to elements of the refined system architecture. Through ASIL decomposition, designers can divide a function’s safety requirements among multiple components. However, in practice, manual ASIL decomposition is difficult and produces varying results. To overcome this problem, a new tool automates ASIL allocation and decomposition. It supports the system and software engineering life cycle by enabling users to efficiently allocate safety requirements regarding systematic failures in the design of critical embedded computer systems. The tool is applicable to industries with a similar concept of safety integrity levels. © 1984-2012 IEEE.

2014

Adaptive-robust friction compensation in a hybrid brake-by-wire actuator

Autores
de Castro, R; Todeschini, F; Araujo, RE; Savaresi, SM; Corno, M; Freitas, D;

Publicação
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART I-JOURNAL OF SYSTEMS AND CONTROL ENGINEERING

Abstract
This work focuses on the development of a pressure-loop controller for a hybrid brake-by-wire system, composed of a hydraulic link and an electro-mechanical actuator. Towards this goal, we will start by constructing a reduced model that is capable of capturing the fundamental dynamics of the actuator, which is particularly useful for control design purposes. Motivated by the large friction disturbances that affect the system, we also investigate linear-in-the-parameter models suitable for (online) model-based friction compensation. More specifically, results from the theory of function approximation, together with optimization techniques, are explored to approximate the Stribeck friction model through a linear-in-the-parameter model. This new linear-in-the-parameter model is then employed in the design of a control law for tracking the braking pressure of the hybrid brake-by-wire. The main features of this controller are the robustness to parametric uncertainties, thanks to the inclusion of a switching-sigma adaptive mechanism, and the attenuation of non-parametric disturbances with a continuous sliding mode action. The stability and robustness properties of the closed-loop system are investigated with the help of the Lyapunov method. Finally, experimental tests demonstrate the effectiveness of the proposed approach and its ability to handle disturbances.

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