Browsing by Issue Date, starting with "2007-10"
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- Fractional order dynamics in a particle swarm optimization algorithmPublication . Pires, E. J. Solteiro; Oliveira, P. B. Moura; Machado, J. A. Tenreiro; Jesus, Isabel S.This article reports the study of fractional dynamics during the evolution of Particle Swarm Optimization (PSO) algorithm. Some initial swarm particles are randomly changed, for simulating the system response, and its effect is compared with a non-perturbed reference. The perturbation effect in the PSO evolution is observed in the perspective of the fitness time behavior of the best particle. the dynamics is represented throught the median of a sample of experiments, while adopting the Fourier analysis for describing the phenomena. The influence of the PSO parameters influence upon the global dynamics is also analyzed.
- Fractional Dynamics in Particle Swarm OptimizationPublication . Pires, E. J. Solteiro; Tenreiro Machado, J. A.; Oliveira, P. B. de Moura; Reis, CecíliaThis 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.
- Evolutionary Computation in the Design of Logic CircuitsPublication . Reis, Cecília; Tenreiro Machado, J. A.; Cunha, J. Boaventura; Pires, E. J. SolteiroThis paper presents two evolutionary schemes and a swarm intelligence algorithm for the design of combinational logic circuits. A Genetic and a Memetic schemes as the evolutionary algorithms. The Particle Swarm Optimization as the swarm algorithm. The fitness function used in these three algorithms is sequential, that is, divided in two parts. The first part of the fitness function f1 evaluates the circuit functionality, while the second part f2 deals with the circuit complexity. The experiments consist in applying the algorithms in the design of two arithmetic circuits: the one-bit full adder and the one-bit full subtractor. We also present a scalability analysis using the parity checker family of circuits.
- A general discretization scheme for the design of IIR fractional filtersPublication . Barbosa, Ramiro S.; Machado, J. A. Tenreiro; Jesus, Isabel S.In this paper we present a general discretization scheme for digital fractional-order integrators and differentiators. The proposed scheme yields many of the widely classical s --> z conversion formulas. A least-squares method for the design of IIR fractional filters is proposed. The design of the recursive digital filter only requires the solution of linear equations. an illustrative example is presented showing the effectiveness of the resulting approximations.
- Towards the PID Control of Heat Diffusion SystemsPublication . Jesus, Isabel S.; Machado, J. A. Tenreiro; Barbosa, Ramiro S.; Pires, E. S. SolteiroIn this work we study a heat diffusion system on a fractional calculus perspective. Several fractional PID tuning methodologies are investigated and compared. The simulations demonstrate the good performance of the proposed fractional algorithm.
- Aplication of fractional algoritms in the control of an helicopter systemPublication . Coelho, J.; Neto, R. Matos; Lebres, C.; Fachada, H.; Ferreira, N. M. Fonseca; Pires, E. J. Solteiro; Tenreiro Machado, J. A.This paper compares the application of fractional and integer order controllers for a laboratory helicopter twin rotor MIMO system using the MatLab package.