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Publications

Publications by CRIIS

2010

Multi-objective Optimization of Parallel Manipulators using a Particle Swarm Algorithm

Authors
Lopes, AM; Freire, H; De Moura Oliveira, PB; Solteiro Pires, EJS; Reis, C;

Publication
NEW ASPECTS OF APPLIED INFORMATICS, BIOMEDICAL ELECTRONICS AND INFORMATICS AND COMMUNICATION

Abstract
Parallel manipulators have attracted the attention of researchers from different areas such as: high-precision robotics, machine-tools, simulators and haptic devices. The choice of a particular structural configuration and its dimensioning is a central issue to the performance of these manipulators. A solution to the dimensioning problem, normally involves the definition of performance criteria as part of an optimization process. In this paper the kinematic design of a 6-dof parallel robotic manipulator is analyzed. Three performance criteria are formulated and optimal solutions are found through a particle swarm formulation.

2010

A long-term risk management tool for electricity markets using swarm intelligence

Authors
Azevedo, F; Vale, ZA; Oliveira, PBM; Khodr, HM;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
This paper addresses the optimal involvement in derivatives electricity markets of a power producer to hedge against the pool price volatility. To achieve this aim, a swarm intelligence meta-heuristic optimization technique for long-term risk management tool is proposed. This tool investigates the long-term opportunities for risk hedging available for electric power producers through the use of contracts with physical (spot and forward contracts) and financial (options contracts) settlement. The producer risk preference is formulated as a utility function (U) expressing the trade-off between the expectation and the variance of the return. Variance of return and the expectation are based on a forecasted scenario interval determined by a long-term price range forecasting model. This model also makes use of particle swarm optimization (PSO) to find the best parameters allow to achieve better forecasting results. On the other hand, the price estimation depends on load forecasting. This work also presents a regressive long-term load forecast model that make use of PSO to find the best parameters as well as in price estimation. The PSO technique performance has been evaluated by comparison with a Genetic Algorithm (GA) based approach. A case study is presented and the results are discussed taking into account the real price and load historical data from mainland Spanish electricity market demonstrating the effectiveness of the methodology handling this type of problems. Finally, conclusions are dully drawn. Crown Copyright

2010

Button heat-pulse sensor for soil water content measurements

Authors
Valente, A; Soares, S; Morais, R; Baptista, JM; Cabral, M;

Publication
Proceedings - 1st International Conference on Sensor Device Technologies and Applications, SENSORDEVICES 2010

Abstract
Recent developed button heat pulse probes (BHPP) demonstrated a great potential for soil water content measurements. This new probe compared to conventional heat pulse probes (HPP), does not use needles, and measurement accuracy is significantly improved. This new design, with the possibility to assembly the probe and electronics in the same package, with low-cost, and with less power consumption compared to conventional HPP, make it suitable to be connected to wireless data acquisition systems in precision agriculture. The probe was tested in agar to demonstrate the potential advantages of the button heat pulse sensor for soil water content measurements. It was possible to have an 0.5 °C temperature rise with only 156mW of power consumption, a ten times power reduction in heat-pulse soil water content measurements. These tests showed the potential use of the button heat pulse sensor for the determination of soil water content. © 2010 IEEE.

2010

A Software Tool for Harmonic Distortion Simulation Caused by Non-linear Household Loads

Authors
Baptista, J; Morais, R; Valente, A; Soares, S; Bulas Cruz, J; Reis, MJCS;

Publication
SOFT COMPUTING MODELS IN INDUSTRIAL AND ENVIRONMENTAL APPLICATIONS

Abstract
In this paper we present a software tool to be used in residential/household generic power circuitry analysis and simulation, under non-linear loads. This tool can both be used by electrical engineers and by students of electrical engineering. It has an easy-to-use, friendly interface, and can be used to teach design techniques or as a laboratory tool to study the applicability of known methods to real world practical situations. Also, the users may supply their own data. The simulated results are very close to the measured ones.

2010

Induction motor response to periodical voltage fluctuations

Authors
Baptista, J; Gonçalves, J; Soares, SFSP; Valente, A; Morais Dos Santos, R; Bulas Cruz, JAM; Reis, MJCS;

Publication
19th International Conference on Electrical Machines, ICEM 2010

Abstract
The main aim of this paper is to analyze the behavior of the three-phase squirrel cage induction motor under different voltage fluctuation levels. To achieve this goal several simulations were performed using the EMTP/ATP tool. Here we present how mechanical torque, speed and efficiency parameters varied with different levels of voltage fluctuation and modeling frequencies. As it was expected, the induction motor is sensitive to voltage fluctuations within certain amplitude levels and frequencies. Also, the speed is more affected by low frequencies and high amplitudes of voltage fluctuations, while the torque and efficiency are more affected by middle and high frequencies and amplitudes. ©2010 IEEE.

2010

Characterization and testing of a shock absorber embedded sensor

Authors
Ferreira, C; Ventura, P; Grinde, C; Morais, R; Valente, A; Neves, C; Reis, M;

Publication
EUROSENSORS XXIV CONFERENCE

Abstract
This article presents the characterization of a shock absorber embedded sensor (SAES) for real-time monitoring of the condition of vehicle shock absorbers in everyday use. A prototype system was built using a custom designed monolithic silicon combined accelerometer, pressure and temperature sensors. The characterization of the SAES was performed and the obtained results meet and even outperform the specification requirements. The SAES was installed in a shock absorber, with adjustable dampling properties, and submitted to road tests. Results show that the condition of a shock absorber can be effectively assessed with the presented SAES. Ensuring that shock absorbers are replaced before reach unacceptable condition, this system will increase onboard comfort and vehicle safety. (C) 2010 Published by Elsevier Ltd.

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