Browsing by Issue Date, starting with "2000-04"
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- Interferências no discurso bilinguePublication . Veloso, Manuela; Amorim, Clara; Ermida, Isabel; Gusmão, MiguelAferir as interferências fonolólicas, morfosintácticas, lexico-semanticas e pragmáticas de uma amostragem homogénea de indivíduos bilingues (Inglês-Potuguês, com aprendizagem naõ cativa ou informal. Os testes foram feitos a partir de uma entrevista, uma tradução, interpretação de imagens e indagação sobre a reação pragmática dos falantes Anglo-Americanos, da mesma faixa social e com o grau de instrução, perante situações do dia-a-dia. em Portugal.
- Chaos dynamics in the trajectory control of redundant manipulatorsPublication . Duarte, Fernando B. M.; Tenreiro Machado, J. A.Several kinematic control algorithms for redundant manipulators adopt generalized inverse matrices. In this line of thought, the generalized inverse control scheme is tested through experiments that reveal the difficulties that often arise. Motivated by these problems this paper studies kinematics and dynamics of the trajectory planning scheme. The experiment confirm the non-linear and chaotic performance of the algorithm and gives a deeper insight towards the future development of superior trajectory control systems.
- On the statistical and Fourier modelling of robot motionPublication . Tenreiro Machado, J. A.; Galhano, AlexandraA new method for the study and optimization of manipulator trajectories is developed. The novel feature resides on the modelling formulation. Standard system descriptions are based on a set of differential equations which, in general, require laborious computations and may be difficul to analyse. Moreover, the derived algorithms are suited to "deterministic" tasks, such as those appearing in a repetitive work, and are not well adapted to a "random" operation that occurs in intelligent systems interacting with a non-structured and changing environment. These facts motivate the development of alternative models based on distinct concepts. The proposed embedding of statistics and Fourier transform gives a new perspective towards the calculation and optimization of the robot trajectories in manipulating tasks.
- Controllability analysis of biped walking robotsPublication . Silva, Filipe M.; Tenreiro Machado, J. A.The focus of this paper is the problem of modelling and control of a biped robot by combining Cartesian-based position and force control algorithms. The complete walking cycle is divided in two phases: i) a single support phase, in which it is studied the trajectory controllability based on simple motion goals and ii) an exchange of support phase, in which the foward leg should absorb the impact and then gradually accept the robot's weight. The contact of the foot with the constrained surface is modelled through linear spring-damper systems both in the vertical and horizontal directions. The system's controllability is enchanced through the insertion of a dynamic selection matrix that modifies the actuating profile in each phase. The control algorithms are simulated and their effectiveness and robustness and discussed.
- Motion chaos in the pseudoinverse control of redundant robotsPublication . Duarte, Fernando B. M.; Tenreiro Machado, J. A.When a manipulator is redundant it is anticipated that the inverse kinematics admits an infinitive number of solutions. Several kinematic control algorithms for redundant manipulators adopt generalized inverse matrices. In this line of thought, the generalized inverse control scheme is tested through experiments that reveal the difficulties that often arise. Motivated by these problems this paper studies kinematics and dynamics of the trajectory planning scheme. The experiment confirm the non-linear and chaotic performance of the algorithm and gives a deeper insight towards the future development of superior trajectory control systems.