Browsing by Issue Date, starting with "2002-05-26"
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- Fractional describing function analysis of systems with backlash and impact phenomenaPublication . Barbosa, Ramiro; Tenreiro Machado, J. A.This paper analyses the dynamical properties of systems with backlash and impact phenomena based on the describing function method. It is shown that this type of nonlinearity can be analyzed in the perspective of the fractional calculus theory. The fractional-order dynamics is illustrated using the Nyquist plot and the results are compared with those of standard models.
- Application of fractional calculus in the control of mechanical systemsPublication . Tenreiro Machado, J. A.; Barbosa, Ramiro; Duarte, Fernando B. M.; Ferreira, Nuno M. F.The Fractional Calculus (FC) goes back to the begining of the theory of differential calculus. Nevertheless, the application of FC just emerged in the last two decades, due to the progress in the area of chaos that revelead subtle relationships with the FC concepts. In the field of dynamical systems theory some work has been carried out but the proposed models and algorithms are still in a preliminary stage of establishment. Having these ideas in mind, the paper discusses a FC perspective in the study of the dynamics and control of mechanical systems.
- Gait efficiency of walking robotsPublication . Silva, Manuel; Tenreiro Machado, J. A.; Lopes, António M.This paper studies periodic gaits of multi-legged robot locomotion systems based on dynamic models. The purpose is to determine the system performance during walking and the best set of locomotion variables. For that objective the prescribed motion of the robot is completely characterized in terms of several locomotion variables such as gait, duty factor, body height, step length, stroke pitch, foot clearance, legs link lengths, foot-hip offset, body and legs mass and cycle time. In this perspective, we formulate three performance measures of the walking robot namely, the mean absolute power, the mean power lost in the joint actuators and the mean force of the interface body-legs per walking distance. A set of model-based experiments reveals the influence of the locomotion variables in the proposed indices.