Browsing by Issue Date, starting with "2004-12"
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- Fractional Order Control of a Hexapod RobotPublication . Silva, Manuel; Tenreiro Machado, J. A.; Lopes, A. M.This paper studies the performance of integer and fractional order controllers in a hexapod robot with joints at the legs having viscous friction and flexibility. For that objective the robot prescribed motion is characterized in terms of several locomotion variables. The walking performance is analysed through the Nyquist stability criterion and several indices that reflect the system dynamical properties. A set of model-based experiments reveals the influence of the different controller implementations upon the proposed metrics.
- Synthesis of Logic Circuits Using Fractional-Order Dynamic Fitness FunctionsPublication . Reis, Cecília; Tenreiro Machado, J. A.; Cunha, J. BoaventuraThis paper analyses the performance of a genetic algorithm using a new concept, namely a fractional-order dynamic fitness function, for the synthesis of combinational logic circuits. The experiments reveal superior results in terms of speed and convergence to archieve a solution.
- Dynamical Analysis of Freeway TrafficPublication . Figueiredo, Lino; Tenreiro Machado, J. A.; Ferreira, José RuiThis paper presents the simulator of intelligent transportation systems (SITS). The SITS is based on a microscopic simulation approach to reproduce real traffic conditions in an urban or nonurban network and considers different types of vehicles, drivers, and roads. A dynamical analysis of several traffic phenomena is then addressed. The results of using classical system theory tools notes that it is possible to study traffic systems, taking advantage of the knowledge gathered with automatic control algorithms. In this line of thought, a new modeling formalism based on the embedding of statistics and Fourier transform is also presented.
- Tuning of PID Controllers Based on Bode’s Ideal Transfer FunctionPublication . Barbosa, Ramiro; Tenreiro Machado, J. A.; Ferreira, Isabel M.This paper presents a new strategy for tuning PID controllers based on a fractional reference model. The model is represented as an ideal closed-loop system whose open-loop is given by the Bode’s ideal transfer function. The PID controller parameters are determined by the minimization of the integral square error (ISE) between the time responses of the desired fractional reference model and of the system with the PID controller. The resulting closed-loop system (with the PID controller) has the desirable feature of being robust to gain variations with step responses exhibiting an iso-damping property. Several examples are presented that demonstrate the effectiveness and validity of the proposed methodology.