Browsing by Issue Date, starting with "2003-09-02"
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- Comparison of fractional and integer order control of an hexapod robotPublication . Silva, Manuel; Tenreiro Machado, J. A.; Lopes, António M.This paper studies the dynamics of foot-ground interaction and the performance of integer and fractional order controllers in multi-legged locomotion systems. For that objective the robot precribed motion is characterized in terms of several locomotion variables. Moreover, to compare the system performance, we formulate six performance measures of the walking robot namely, the mean absolute power, the mean power dispersion, the mean power lost in the joint actuators, the mean force of the interface body-legs per walking distance and mean square error of the hip and foot trajectories. A set of model-based experiments reveals the influence of the different controller implemantations in the proposed indices.
- Fractional order dynamics in the trajectory planning of redundant and hyper-redundant manipulatorsPublication . Duarte, Fernando B. M.; Tenreiro Machado, J. A.Redundant manipulators have some advantages when compared with classical arms because they allow the trajectory optimization, both on the free space and on the presence of obstacles, and the resolution of singularities. For this type of arms the proposed kinematic control algorithms adopt generalized inverse matrices but, in general, the corresponding trajectory planning schemes show important limitations. Motivated by these problems this paper studies the pseudoinverse-based trajectory planning algorithms, using the theory of fractional calculus.
- A fractional calculus perspective of PID tuningPublication . Barbosa, Ramiro; Tenreiro Machado, J. A.; Ferreira, Isabel M.This paper gives an interpretation of the classical PID controller tuning based on the fractional calculus theory. The PID parameters are calculated according with the specifications of an elementary system whose open-loop transfer function is a fractional order integrator (FOI). The performances of the two systems are compared and illustrated through the frequency and time responses.