Browsing by Issue Date, starting with "2005-08"
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- Modelling and simulation of artificial locomotion systemsPublication . Silva, Manuel; Tenreiro Machado, J. A.; Lopes, António M.This paper describes a simulation model for a multi-legged locomotion system with joints at the legs having viscous friction, flexibility and backlash. For that objective the robot prescribed motion is characterized in terms of several locomotion variables. Moreover, the robot body is divided into several segments in order to emulate the behaviour of an animal spine. The foot-ground interaction is modelled through a non-linear spring-dashpot system whose parameters are extracted from the studies on soil mechanics. To conclude, the performance of the developed simulation model is evaluated through a set of experiments while the robot leg joints are controlled using fractional order algorithms.
- Fractional order dynamics in classical electromagnetic phenomenaPublication . Tenreiro Machado, J. A.; Jesus, Isabel S.; Galhano, Alexandra; Albert, W. Malpica; Silva, Fernando; Tar, József K.The Maxwell equations play a fundamental role in the well established formulation of the electromagnetic theory. These equations lead to the derivation of precise mathematical models useful in many applications in physics and engineering. The Maxwell equations involve only the integer-order calculus and, therefore, it is natural that the resulting classical models adopted in electrical engineering reflect this perspective. Recently, a closer look of some phenomena present in electrical systems, such as motors, transformers and lines, and the motivation towards the development of comprehensive models, seem to point out the requirement for a fractional calculus approach. Bearing these ideas in mind, in this study we shall address the well-known ‘skin effect’ and we reevaluate the results demonstrating its fractional-order dynamics.
- Evolutionary design of combinational circuits using fractional-order fitness functionsPublication . Reis, Cecília; Tenreiro Machado, J. A.; Cunha, J. BoaventuraThis paper analyses the performance of a genetic algorithm using the new concept of fractional-order dynamic fitness function, for the synthesis of combinational logic circuits. The experiments reveal superior results in terms of speed and convergence to achieve a solution.