Browsing by Issue Date, starting with "2007-11"
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- Combining genetic and particle swarm algorithms for the design of combinational circuitsPublication . Reis, Cecília; Tenreiro Machado, J. A.Evolutionary computation (EC) is a growing research field of Artificial Intelligence (AI) and is divided in two main areas: the Evolutionary Algorithms (EA) and the Swarm Intelligence (SI). This paper presents an algorithm that combines an EA algorithm - the Genetic Algorithm (GA) with a SI algorithm - the Particle Swarm Optimization Algorithm (PSO). The new algorithm is applied to the synthesis of combinational logic circuits. With this combination is possible to take advantage of the best features of each particular algorithm.
- Applications of fractional calculus in electrical and computer engineeringPublication . Tenreiro Machado, J. A.; Silva, Manuel; Barbosa, Ramiro; Jesus, Isabel S.; Reis, Cecília; Marcos, Maria da Graça; M. Afonso, Luís; Lima, Miguel F. M.; Pires, E. J. Solteiro; Ferreira, N. M. FonsecaFractional Calculus (FC) goes back to the beginning of the theory of differential calculus. Nevertheless, the application of FC just emerged in the last two decades, due to the progress in the area of chaos that revealed subtle relationships with the FC concepts. In the field of dynamical systems theory some work has been carried out but the proposed models and algorithms are still in a preliminary stage of establishment. Having these ideas in mind, the paper discusses a FC perspective in the study of the dynamics and control of several systems. This article illustrates several applications of fractional calculus in science and engineering. It has been recognized the advantageous use of this mathematical tool in the modeling and control of many dynamical systems. In this perspective, this paper investigates the use of FC in the fields of controller tuning, electrical systems, digital circuit synthesis, evolutionary computing, redundant robots, legged robots, robotic manipulators, nonlinear friction and financial modeling.
- Helicopter system modelling and control with matlabPublication . Coelho, J.; Neto, R.; Afonso, D.; Lebres, C.; Fachada, H.; Ferreira, N. M. Fonseca; Pires, E. J. Solteiro; Tenreiro Machado, J. A.This paper presents the modelling and control of a laboratory helicopter system with MatLab. In this perspective, students are motivated to investigate the dynamics, trajectory planning and control. Based on this experience, further studies on helicopter system, using more sophisticated concepts, are, then, more attractive from the students point of view.
- Single-objective maximin sorting scheme: application to radio frequency circuit designPublication . Machado, E. J. Solteiro Pires; Mendes, Luís; Oliveira, P. B. de Moura; Tenreiro Machado, J. A.; Ferreia, N. M. Fonseca; Vaz, João Caldinhas; Rosário, Maria JoãoObtaining a well distributed non-dominated Pareto front is one of the key issues in multi-objective optimization algorithms. This paper proposes an algorithm which promotes well distributed non-dominated fronts in the parameters space when a single-objective function is optimized. The proposed technique is described and tested in an automated synthesis circuit design problem. The project consists in designing CMOS radio-frequency and microwave binaryweighted differential switched capacitor arrays (RFDSCAs) from user top-level specification to component size. The genetic synthesis tool optimizes a fitness function based on the performance parameter of the RFDSCAs. To validate the proposed design methodology, a CMOS RFDSCA is synthesized, using a 0.25 μm BiCMOS technology, and verified by the SpectreRF simulator of the Cadence design environment. The results show that the synthesis and simulation outcomes are in very good agreement.