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Publicações

Publicações por CPES

2016

Minimum-Time Path-Following for Highly Redundant Electric Vehicles

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

Publicação
IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY

Abstract
Modern electric vehicles are most often designed with actuator redundancy and in-wheel propulsion, a combination that appears particularly suitable for the design of motion controllers that can optimally blend multiple objectives, such as dynamic, safety and driver-oriented. This paper considers such a technological setting and concentrates on the design of a path-following algorithm with minimum-time features, with the aim of combining performance and energy-oriented optimization of the vehicle motion. Specifically, an approximate minimum-time trajectory is obtained by appropriate convexification of the resulting optimization problem. The effectiveness of the approach is assessed by means of simulation tests carried out on the CarSim vehicle simulation environment.

2016

Initial Study on Fault Tolerant Control with Actuator Failure Detection for a Multi Motor Electric Vehicle

Autores
dos Santos, B; Araujo, RE;

Publicação
TECHNOLOGICAL INNOVATION FOR CYBER-PHYSICAL SYSTEMS

Abstract
This study presents a scheme to detect and isolate faults in over-actuated electric vehicles. Although this research work is still emerging, it already provides a view of the main challenges on the problem and discusses some possible approaches that can be useful to overcome the key difficulties. This paper intends to present a fault detection algorithm based on Unknown Input Observer (UIO). The residuals are built through the difference of signals between the measured outputs and the output estimations from the observer. The main idea is to detect fault in the electric motors and steering wheel actuator. The algorithm is presented and tested with some fault scenarios using the co-simulation tool between Simulink/MATLAB and the high-fidelity model from Carsim software.

2016

Indoor localization using barely perceptible audio signals

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

Publicação
U.Porto Journal of Engineering

Abstract
This paper presents a new approach to an audio-based indoor localization system. By using audio signals emitted by a public address sound system, mobile devices may globally localize themselves in an indoor environment where global navigation satellite systems are not viable or reliable. The use of data hiding techniques such as spread spectrum coding or echo hiding has allowed to convey information to a receiver avoiding people’s perception of the added audio content. Results demonstrate a relatively quite good localization with centimetre accuracy and precision and successful data transmission using barely perceptible audio signals.

2016

Model-based predictive control implementation for cooperative adaptive cruise control

Autores
Lopes, A; Araújo, RE;

Publicação
U.Porto Journal of Engineering

Abstract
The automation of road vehicles has become a necessity to improve the efficiency and safety of this system. In a vehicle formation it is important to maintain a safety distance between the vehicles. The control of a vehicle spacing distance and longitudinal velocity can be achieved through the implementation of a model-based predictive controller. This implementation of a cooperative adaptive cruise control allows the access of another vehicle state information through vehicular communication technology and promote state prediction and ultimately system stability. The optimization algorithm performs the computation of the control input in a control horizon window and ensures that the spacing error takes only positive values. The results of the proposed controller are evaluated through the computational tool Simulink in the two-vehicle platoon. The controller is implemented in the precedent vehicle. To assess the performance of the proposed controller different control parameters and constraints were used.

2016

Price forecasting and validation in the Spanish electricity market using forecasts as input data

Autores
Ortiz, M; Ukar, O; Azevedo, F; Mugica, A;

Publicação
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS

Abstract
The electricity sector has been subjected to major changes in the last few years. Previously, there existed a regulated system where electric companies could know beforehand the amount of energy each generator would produce, hence basing their largely operational strategy on cost minimization in order to increase their profits. In Spain, from 1988 till 1997, electricity prices were established by the 'Marco Legal Estable' Stable Legal Framework, where the Ministry of Industry and Energy acknowledged the existence of certain generation costs related to each type of technology. It was an industrial sector with no actual competition and therefore, with very few controllable risks. In the aftermath of the electricity market liberalization competition and uncertainty arose. Electricity spot prices became highly volatile due to the specific characteristics of electricity as a commodity. Long-term contracts allowed for hedge funds to act against price fluctuation in the electricity market. As a consequence, developing an accurate electricity price forecasting model is an extremely difficult task for electricity market agents. This work aims to propose a methodology to improve the limitations of those methodologies just using historical data to forecast electricity prices. In this manner, and in order to gain access to more recent data, instead of using natural gas prices and electricity load historical data, a regression model to forecast the evolution of natural gas prices, and a model based on artificial neural networks (ANN) to forecast electricity loads, are proposed. The results of these models are used as input for an electricity price forecast model. Finally, and to demonstrate the effectiveness of the proposed methodology, several study cases applied to the Spanish market, using real price data, are presented.

2016

Optimal Cable Design of Wind Farms: The Infrastructure and Losses Cost Minimization Case

Autores
Cerveira, A; de Sousa, A; Solteiro Pires, EJS; Baptista, J;

Publicação
IEEE TRANSACTIONS ON POWER SYSTEMS

Abstract
Wind power is the source of electrical energy that has grown more over the last years, with annual rate in installed capacity around 20%. Therefore, it is important to optimize the production efficiency of wind farms. In a wind farm, the electrical energy is collected at a central substation from different wind turbines placed nearby. This paper addresses the optimal design of the cable network interconnecting the turbines to the substation aiming to minimize not only the infrastructure cost but also the cost of the energy losses in the cables. Although this problem is non-linear, different integer linear programming models are proposed considering the wind farm technical constraints. The models are applied to three real cases Portuguese wind farms. The computational results show that the proposed models are able to compute the optimal solutions for all cases.

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