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Publicações

Publicações por Paulo Moura Oliveira

2006

Dynamical modelling of a genetic algorithm

Autores
Solteiro Pires, EJS; Tenreiro Machado, JAT; de Moura Oliveira, PBD;

Publicação
SIGNAL PROCESSING

Abstract
This work addresses the signal propagation and the fractional-order dynamics during the evolution of a genetic algorithm (GA). In order to investigate the phenomena involved in the GA population evolution, the mutation is exposed to excitation perturbations during some generations and the corresponding fitness variations are evaluated. Three distinct fitness functions are used to study their influence in the GA dynamics. The input and output signals are studied revealing a fractional-order dynamic evolution, characteristic of a long-term system memory.

2003

Fractional order dynamics in a GA planner

Autores
Pires, EJS; Machado, JAT; Oliviera, PBD;

Publicação
SIGNAL PROCESSING

Abstract
This work addresses the signal propagation and the fractional-order dynamics during, the evolution of a genetic algorithm (GA), for generating a robot manipulator trajectory. The GA objective is to minimize the trajectory space/time ripple without exceeding the torque requirements. In order to investigate the phenomena involved in the GA population evolution, the mutation is exposed to excitation perturbations and the corresponding fitness variations are evaluated. The chaos-like noise and the input/output signals are studied revealing a fractional-order dynamics, characteristic of a long-term system memory.

2007

Manipulator trajectory planning using a MOEA

Autores
Pires, EJS; Oliveira, PBDM; Machado, JAT;

Publicação
APPLIED SOFT COMPUTING

Abstract
Generating manipulator trajectories considering multiple objectives and obstacle avoidance is a non-trivial optimization problem. In this paper a multi-objective genetic algorithm based technique is proposed to address this problem. Multiple criteria are optimized considering up to five simultaneous objectives. Simulation results are presented for robots with two and three degrees of freedom, considering two and five objectives optimization. A subsequent analysis of the spread and solutions distribution along the converged non-dominated Pareto front is carried out, in terms of the achieved diversity.

2011

MaxiMin MOPSO Design of Parallel Robotic Manipulators

Autores
Freire, H; de Moura Oliveira, PBD; Solteiro Pires, EJS; Lopes, AM;

Publicação
SOFT COMPUTING MODELS IN INDUSTRIAL AND ENVIRONMENTAL APPLICATIONS, 6TH INTERNATIONAL CONFERENCE SOCO 2011

Abstract
A maximin multiobjective particle swarm optimization algorithm variant is presented, in the context of parallel robotic manipulator design. 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. Two dynamic performance criteria are formulated and non-dominated optimal solutions are found through a multi-objective particle swarm optimization algorithm. Preliminary simulation results are presented.

2010

Greenhouse Heat Load Prediction Using a Support Vector Regression Model

Autores
Coelho, JP; Cunha, JB; Oliveira, PD; Pires, ES;

Publicação
SOFT COMPUTING MODELS IN INDUSTRIAL AND ENVIRONMENTAL APPLICATIONS

Abstract
Modern greenhouse climate controllers are based on models in order to simulate and predict the greenhouse environment behaviour. These models must be able to describe indoor climate process dynamics, which are a function of both the control actions taken and the outside climate. Moreover, if predictive or feedforward control techniques are to be applied, it is necessary to employ models to describe and predict the weather. From all the climate variables, solar radiation is the one with greater impact in the greenhouse heat load. Hence, making good predictions of this physical quantity is of extreme importance. In this paper, the solar radiation is represented as a time-series and a support vector regression model is used to make long term predictions. Results are compared with the ones achieved by using other type of models, both linear and non-linear.

2007

Fractional dynamics in particle swarm optimization

Autores
Pires, EJS; Machado, JAT; Oliveira, PBD; Reis, C;

Publicação
2007 IEEE INTERNATIONAL CONFERENCE ON SYSTEMS, MAN AND CYBERNETICS, VOLS 1-8

Abstract
This paper studies the fractional dynamics during the evolution of a Particle Swarm Optimization (PSO). Some swarm particles of the initial population are randomly changed for stimulating the system response. After the result is compared with a reference situation. The perturbation effect in the PSO evolution is observed in the perspective of the time behavior of the fitness of the best individual position visited by the replaced particles. The dynamics is investigated through the median of a sample of experiments, while adopting the Fourier analysis for describing the phenomena. The influence of the PSO parameters upon the global dynamics is also analyzed by performing several experiments for distinct values.

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