Browsing by Issue Date, starting with "2006-08"
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- The Cooperation of Two Manipulators with Fractional ControllersPublication . Ferreira, N. M. Fonseca; Tenreiro Machado, J. A.; Cunha, J. BoaventuraThis paper analyzes the dynamics and the implementation of fractional-order algorithms in the position/force control of two robots holding an object. The experiments reveal that fractional algorithms lead to performances superior to classical integer-order controllers.
- Windowed Fourier Transform of Experimental Robotic Signals with Fractional BehaviorPublication . Lima, Miguel F. M.; Tenreiro Machado, J. A.; Crisóstomo, ManuelThis paper analyzes the signals captured during impacts and vibrations of a mechanical manipulator. The signals are treated through signal processing tools such as the fast Fourier transform and the windowed Fourier transform.The Fourier spectrum of several signals presents a non integer behavior. The experimental study provides useful information that can assist in the design of a control system to deal with the unwanted effects of vibrations.
- Strategies for the Control of Heat Diffusion Systems Based on Fractional CalculusPublication . Jesus, Isabel S.; Barbosa, Ramiro; Tenreiro Machado, J. A.; Cunha, J. BoaventuraThe concept of differentiation and integration to non-integer order has its origins in the nineteen century. However, only in the second-half of the twenty century appeared the first applications related to the area of control theory. In this paper we consider the study of a heat diffusion system based on the application of the fractional calculus concepts. In this perspective, several control methodologies are investigated and compared, such as the adoption of a Smith predictor structure for the better control of systems with time delays. Several simulations are presented assessing the performance of the proposed fractional-order algorithms.
- Circuit Synthesis Using Particle Swarm OptimizationPublication . Reis, Cecília; Tenreiro Machado, J. A.; Galhano, Alexandra; Cunha, J. BoaventuraParticle Swarm Optimization (PSO) is a population-based search algorithm that is initialized with a population of random solutions, called particles. In a PSO scheme each particle flies through the search space with a velocity that is adjusted dynamically according with its historical behavior. Therefore, the particles have a tendency to fly towards the best search area along the search process. PSO is also an evolutionary computation technique well adapted to the automatic design of electronic devices. In this line of thought, this paper proposes a PSO based algorithm for logic circuit synthesis. The results show the statistical characteristics of this algorithm with respect to number of generations required to achieve the solutions. The results are compared with other two Evolutionary Algorithms (EAs), namely Genetic and Memetic Algorithms (GA and MA).