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Publications

Publications by Rui Esteves Araujo

2011

A control allocation approach to manage multiple energy sources in EVs

Authors
De Castro, R; Melo, P; Pacheco, P; Araujo, RE; Freitas, D;

Publication
2011 IEEE Vehicle Power and Propulsion Conference, VPPC 2011

Abstract
This article is concerned with the design of an energy management system (EMS) for the hybridization of multiple energy sources (ES's) in electric vehicles, focusing in a particular configuration composed by batteries and supercapacitors (SCs). As a first design step, we investigated an (non-causal) optimal power allocation, targeting the minimization of the energy losses over a complete driving cycle. Albeit the solution obtained with this formulation demands the advance knowledge of the vehicle driving cycle, it also provides a useful benchmark solution to assess the performance of causal EMS's. A more practical EMS is then derived, based on the control allocation (CA) concept. This approach, typically employed in redundant control systems, enable us to address the various objectives and constraints that appear in EMS design problem, such as the DC bus voltage regulation, SC state of charge tracking, minimization of power losses, current and state of charge limits, etc. Simulation results show the effectiveness of the proposed CA based EMS, yielding performances very close to the optimal non-causal power allocation. © 2011 IEEE.

2009

Design, Development and Characterisation of a FPGA Platform for Multi-Motor Electric Vehicle Control

Authors
de Castro, R; Araujo, RE; Oliveira, H;

Publication
2009 IEEE VEHICLE POWER AND PROPULSION CONFERENCE, VOLS 1-3

Abstract
Two three-phase squirrel-cage induction motors are used as a propulsion system of an electric vehicle (EV). A simple XC3S1000 FPGA is used to simultaneously control both electric motors, with field oriented control and space vector modulation techniques. To electronically distribute the torque between the two electric motors, a simple, yet effective, strategy based on a uniform torque distribution has been implemented. Experimental results obtained with a multi-motor EV prototype demonstrate the proper operation of the proposed system.

2012

Robust DC-Link Control in EVs With Multiple Energy Storage Systems

Authors
de Castro, R; Araujo, RE; Trovao, JPF; Pereirinha, PG; Melo, P; Freitas, D;

Publication
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY

Abstract
The energy storage system (ESS), as well as its efficient management, represents a key factor for the success of electric vehicles. Due to well-known technological constraints in ESSs, there has been a growing interest in combining various types of energy sources with complementary features. Among the many possible combinations, our interest here lies in the hybridization of batteries and supercapacitors (SCs) with an active parallel arrangement, i.e., the sources are connected to the direct current (dc) bus through two bidirectional dc-dc converters (step-up). Based on this ESS topology, a robust dc-link controller is employed to regulate the dc-bus voltage and track the SCs current in spite of uncertainties in the system. For this purpose, we start by showing that the converters' uncertainty, e. g., the powertrain load, can be modeled as a convex polytope. The dc-link controller is then posed as a robust linear-quadratic regulator problem and, by exploring the convex polytope, converted in a linear matrix inequalities framework, which can efficiently be solved by numerical means. Finally, the operation envelope of the controller is extended by scheduling the gains according to the energy sources' voltages, which is an important feature to cope with the voltage variations in the SCs. To analyze the performance of the control architecture, a reduced-scale prototype was built. The experimental results show that, compared with the nonrobust and non-gain-scheduled controllers, the proposed dc-link controller offers better transient response and robustness to disturbances. Furthermore, the global performance of the controller is evaluated during certain driving cycles.

2008

An Electric Wheelchair as a Tool for Motivating Students in Power Electronics

Authors
Lopes, FP; Oliveira, PS; Reis, LP; Araujo, RE;

Publication
2008 INTERNATIONAL SYMPOSIUM ON POWER ELECTRONICS, ELECTRICAL DRIVES, AUTOMATION AND MOTION, VOLS 1-3

Abstract
Nowadays the education on electrical engineering, in European countries, is facing on one side a high demand for engineers coming from industry and on the other hand a reduced interest from younger generation, whose interest is highly polarised by information and communication technologies. A permanent-magnet synchronous motor (PMSM) controller for an electric wheelchair demo track has been set up, in order to reinforce the demonstrative aspects of modern technology as a contribution to the motivation of students for the industrial electronics world. The motors are controlled at different operating conditions by means of a current control law using a low cost microcontroller board. The prototype has been designed specifically to meet the requirement of low cost and it contains all of the active functions required to implement the control of the electric wheelchair. The resulting prototype has a very low cost compared to commercial "black-box" modules. This prototype allows a first approach between a real technical system and power electronics, increasing the student's motivation for the power electronics area and to significantly enhance their skills to measure and interpret measurements and comparing those to theoretical predictions.

2006

The design and implementation of an electric go-kart for education in motor control

Authors
Cardoso, C; Ferreira, J; Alves, V; Araujo, RE;

Publication
2006 INTERNATIONAL SYMPOSIUM ON POWER ELECTRONICS, ELECTRICAL DRIVES, AUTOMATION AND MOTION, VOLS 1-3

Abstract
In this paper we present an electric go-kart suitable for an instructional laboratory in electric drives. An overview of propulsion system design, power conversion structure and control is presented. A three-phase squirrel-cage induction motor is used as propulsion system. The motor is controlled at different operating conditions by means of a simple scalar control using a low cost controller board developed for light electric vehicles used in local areas. The prototype has been designed specifically to meet the requirement of low cost and it contains all of the active functions required to implement the control of the go-kart.

2009

Control in Multi-Motor Electric Vehicle with a FPGA Platform

Authors
de Castro, R; Araujo, RE; Oliveira, H;

Publication
2009 IEEE INTERNATIONAL SYMPOSIUM ON INDUSTRIAL EMBEDDED SYSTEMS

Abstract
A new FPGA based platform is presented for controlling a Multi-Motor Electric Vehicle (EV). By exploring the FPGA parallel processing capabilities, two induction motor controllers, based on Field Orientation Control and Space Vector Modulation techniques, were merged in a single and compact chip. Implementation issues related with the limited number of dedicated multipliers were overcome using an efficient computational block, based on resource sharing strategy. The developed IP Cores were carefully optimized to fit in a low cost XC3S1000. Experimental results, obtained with a multi-motor EV prototype, demonstrate the proper operation of the proposed propulsion system.

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