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- Da tradução: a problemática da competência retórica e da aceitabilidadePublication . Mota, Eduarda Maria Ferreira daDa tradução: a problemática da competência retórica e da aceitabilidade
- Vozes suspensas, vidas adiadas: Bertha Mason, Lucy Audley, e a situação da mulher no século XIXPublication . Pontes, Maria da Conceição Gomes NogueiraVozes suspensas, vidas adiadas: Bertha Mason, Lucy Audley, e a situação da mulher no século XIX
- A Variable Structure Control Algorithm for Robot Manipulators Using Acceleration FeedbackPublication . Machado, J. A. Tenreiro; Carvalho, J. L. Martins deA new variable structure control algorithm for robot manipulators is announced. Second order linear system sliding curves and a new control law, eliminate the reaching phase problems as well as the chattering usually present in the sliding mode. This controller architecture may also be interpreted as the result of the acceleration data integration on the VSS algorithm. Consequently, there is a shift from the computational burden, often present in sophisticated control schemes, towards a simpler but highly sensor based structure. The results show a remarkable improvement over conventional VSS controllers, maintaining, however, a low computational complexity which make it well suited for microcomputer implementation.
- On the analysis and design of robot manipulators: A statistical perspectivePublication . Galhano, Alexandra; Tenreiro Machado, J. A.; Carvalho, J. L. Martins deA new approach to the analysis and design of robot manipulators is presented. The novel feature resides on a non-standard formulation to the modelling problem. Usually, system descriptions and based on a set of differential equations which, due to thier nature lead to very precise results and strategies but, in general, require laborious computations. Yhis motivates the need of alternative models based on other mathematical concepts. The proposed statistical method is a step in this direction which gives clear guidelines towards the robot kinematic and dynamic optimization. Furthermore, the proposed method points out new concepts well adapted to the study of biological-like muscleactuated robotic arms.
- THE SIMULATION OF INTERACTING LIQUID-LIQUID DISPERSIONS - A NEW ALGORITHM AND ITS POTENTIALITYPublication . Guimarães, M. M. L.; Cruz-Pinto, J. J. C.; Regueiras, P. F. R.; Madureira, C. N. M.[Abstract] The simulation of interacting liquid-liquid dispersions undergoing mass transfer and/or chemical reactions is a major chemical engineering problem, that has not yet been satisfactorily solved. The difficulties do not exclusively lie on the experimental validation of the models and their predictions, but are still rooted on the inability of current algorithms to describe the real nature of the dispersion, namely its full trivariate structure - distribution of drop volumes (v), ages (tT) and _= solute concentrations (c) - where v, t and ce are not satistically independent. A survey is given of the authors' latest, recently published (1,2), work and a detailed discussion is then presented of the fine structure and behaviour of the dispersion; the major requirement of an adequate statistical analysis of the simulation results is also dealt with. The paper ends with the authors views on possible trends of future research on this topic.
- On the statistical modelling of robot manipulatorsPublication . Galhano, Alexandra; Carvalho, J. L. Martins de; Tenreiro Machado, J. A.A novel approach to the modelling of robot manipulators is presented. Usually, system descriptions are based on a set of differential equations which, due to their nature, lead to very precise results and strategies but, in general, require laborious computations. This motivates the need of alternative methods based on other mathematical concepts. The proposed statistical model gives clear guidelines towards the optimization of the robot performances.
- Microcomputer evaluation in robot controlPublication . Tenreiro Machado, J. A.; Carvalho, J. L. Martins de; Galhano, AlexandraThe high computational burden posed by modern control algorithms preclude its industrial application using present day microcomputers. In this paper we evaluate the computational load of different logical and arithmetic operations and the capabilities of several computing systems (software and hardware). This study reveals that real-time limitations ca be alleviated through the adoptation of general techniques associated with the data representation. Such techniques achieve not only a more efficient management of the computational resources but also provide a deeper insight on developments towards future real-time control architectures.
- On the analysis and design of robot manipulators: A statistical approachPublication . Galhano, Alexandra; Tenreiro Machado, J. A.; Carvalho, J. L. Martins deA new approach to the analysis and design of robot manipulators is presented. The novel feature resides on a non-standard approach to the modelling problem. Usually, system descriptions are based on a set of differential equations which, due to their nautre lead to very precise results and strategies but in general lead to laborious computations. This motivates the need of alternative models based on other mathematical concepts. The proposed statistical method is a step in this direction which gives clear guidelines towards the robot kinematic and dynamic optimization. Furthermore, the use of histograms allows not only fast design procedures but above all, the use of experiemental data; consequently, complex dynamic modelling exercises can be avoided.
- Computer system evaluation in robot controlPublication . Tenreiro Machado, J. A.; Carvalho, J. L. Martins de; Galhano, AlexandraThe high computational burden posed by mordern control algorithms preclude its industrial application using present day microcomputers. In this paper we evaluate the computational load of different logical and arihmetic operations and the capabilities of several computing systems (software & hardware). This study reveals that real-time limitations can be alleviated through the adoption of general techniques achieve not only a more efficient management of the computational resources but also provide a deeper insight on developments towards future real-time control architectures.
- Statistical modelling of robot manipulatorsPublication . Galhano, Alexandra; Tenreiro Machado, J. A.; Carvalho, J. L. Martins deA novel approach to the modelling of robot manipulators is presented. Usually, system descriptions are based on a set od differential equations which, due to their nature, lead to very precise results and strategies but, in general, require laborious computations. This motivates the need of alternative methods based on other mathematical concepts. The proposed statistical model gives clear guidelines towards the robot kinematic and dynamic optimization and the definition of rest and active manipulation regions. Furthermore, the results point out ideal properties for the actuators namely as "position and acceleration" devices instead of "velocity" machines. This observation is utmost importance as it gives a basis to new mechanical robot manipulator structures, with performances close to biomechanical systems.