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Publicações

Publicações por Rui Esteves Araujo

2012

Torque blending and wheel slip control in EVs with in-wheel motors

Autores
de Castro, R; Araujo, RE; Tanelli, M; Savaresi, SM; Freitas, D;

Publicação
VEHICLE SYSTEM DYNAMICS

Abstract
Among the many opportunities offered by electric vehicles (EVs), the design of power trains based on in-wheel electric motors represents, from the vehicle dynamics point of view, a very attractive prospect, mainly due to the torque-vectoring capabilities. However, this distributed propulsion also poses some practical challenges, owing to the constraints arising from motor installation in a confined space, to the increased unsprung mass weight and to the integration of the electric motor with the friction brakes. This last issue is the main theme of this work, which, in particular, focuses on the design of the anti-lock braking system (ABS). The proposed structure for the ABS is composed of a tyre slip controller, a wheel torque allocator and a braking supervisor. To address the slip regulation problem, an adaptive controller is devised, offering robustness to uncertainties in the tyre-road friction and featuring a gain-scheduling mechanism based on the vehicle velocity. Further, an optimisation framework is employed in the torque allocator to determine the optimal split between electric and friction brake torque based on energy performance metrics, actuator constraints and different actuators bandwidth. Finally, based on the EV working condition, the priorities of this allocation scheme are adapted by the braking supervisor unit. Simulation results obtained with the CarSim vehicle model, demonstrate the effectiveness of the overall approach.

2012

Real-time estimation of tyre-road friction peak with optimal linear parameterisation

Autores
de Castro, R; Araujo, RE; Freitas, D;

Publicação
IET CONTROL THEORY AND APPLICATIONS

Abstract
Spurred by the problem of identifying, in real-time, the adhesion levels between the tyre and the road, a practical, linear parameterisation (LP) model is proposed to represent the tyre friction. Towards that aim, results from the theory of function approximation, together with optimisation techniques, are explored to approximate the non-linear Burckhardt model with a new LP representation. It is shown that, compared with other approximations described in the literature, the proposed LP model is more efficient, that is, it requires a smaller number of parameters, and provides better approximation capabilities. Next, a modified version of the recursive least squares, subject to a set of equality constraints on parameters, is employed to identify the LP in real time. The inclusion of these constraints, arising from the parametric relationships present when the tyre is in free-rolling mode, reduces the variance of the parametric estimation and improves the convergence of the identification algorithm, particularly in situations with low tyre slips. The simulation results obtained with the full-vehicle CarSim model under different road adhesion conditions demonstrate the effectiveness of the proposed LP and the robustness of the friction peak estimation method. Furthermore, the experimental tests, performed with an electric vehicle under low-grip roads, provide further validation of the accuracy and potential of the estimation technique.

2011

Survey on Fault-Tolerant Diagnosis and Control Systems Applied to Multi-motor Electric Vehicles

Autores
Silveira, A; Araujo, RE; de Castro, R;

Publicação
TECHNOLOGICAL INNOVATION FOR SUSTAINABILITY

Abstract
In the last years we have witnessed a growing interest, by the academic community and the automotive industry, in the multi-motor electric vehicles. The electrical nature of the propulsion is going to stress even more an increasing insertion of electronic devices in the vehicles. Furthermore, carmakers are performing research and already presented some vehicles based on the concept of X-By-Wire. Consequently, the growing complexity of the actuators and their control, as well as the need of increasing the safety and reliability of the vehicles obliges to the study and development of intelligent computational systems dedicated to the detection and diagnosis of failures in the electric propulsion. Hence, it is fundamental to start advanced studies leading to the development of innovative solutions that embed fault-tolerant electric propulsion in the electric vehicles. Accordingly, the main objective of this work consists on the bibliographic revision and study of fault-tolerant diagnosis and control systems dedicated to multi-motor electric vehicles.

2006

Low cost control and monitoring motion control ICs

Autores
Moutinho, J; Araujo, RE; Leite, V;

Publicação
Circuits and Systems for Signal Processing , Information and Communication Technologies, and Power Sources and Systems, Vol 1 and 2, Proceedings

Abstract
For a long time, controlling AC motors in an efficient way, was a task only in the reach of some very specific electronic design Engineers. Now, with the up rise of Integrated Platforms it is possible to implement, with almost no effort, the desired application, customizing almost everything at the reach of a simple and user friendly software interface. However, the simplicity in control and monitoring has a major settle back. As expected, such products, very desirable by the market, are only sold in conjunction with an evaluation platform. Sometimes this platform does not fit the consumer needs and buying the full package is not a satisfactory solution, especially if it is just to get the control and monitoring software. In this paper, it will be shown that low cost alternatives are possible. Using free tools and manufacturer's documentation, it is simple to implement Motor Control with the desired IC by means of a very intuitive and complete Graphical Unit Interface (GUI), built attending our special needs.

2011

Overview on energy management strategies for electric vehicles - Modelling, trends and research perspectives

Autores
Melo, P; Araujo, RE; De Castro, R;

Publicação
Proceedings of the 2011 3rd International Youth Conference on Energetics, IYCE 2011

Abstract
The economical and environment impacts of fossil energies increased the interest for hybrid, battery and fuel-cell electric vehicles. Energy management systems (EMS) have a fundamental role in achieving high efficiency levels in vehicle performances, without compromise its drivability features. This is a complex task, since one is dealing with the integration of different physical subsystems. In addition, several vehicle electric power-train architectures must be considered, requiring different energy management approaches. Considering EMS for real-time applications will bring a higher complexity level. This paper aims at putting these efforts into perspective deriving a more holistic view of the literature in this topic. We start the analysis on the general requirements for EMS to identify the more demanding ones for real-time applications. Based on this analysis, we suggest some open challenges and describe new research opportunities. © 2011 INESC Coimbra.

2005

A hardware tool for explained power electronics control of induction motors

Autores
Araujo, RE; Teixeira, H; Barbosa, J; Leite, V;

Publicação
2005 European Conference on Power Electronics and Applications

Abstract
This paper presents a digital controller suitable for an instructional laboratory in electric drives. A prototype has been designed specifically to meet the requirements of low cost and motivating education tool, and it contains all of the active functions required to implement the open loop control of induction motors. This approach develops the concept of "grey box" module where the details are built for convenience, but not hidden inside as a "black box". Introductory laboratory experiments are presented to demonstrate how this hardware can be integrated in laboratory classes to present the most important concepts as regards adjustable speed drives.

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