Browsing by Issue Date, starting with "1998-09-17"
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- Dynamic phenomena during biped walkingPublication . Silva, Filipe M.; Tenreiro Machado, J. A.This paper presents the energy analysis of a biped locomotion system. Our main goal is to gain insight into the movement strategeis in walking and to search for the optimal locomotion variables that minimise a cost function related to energy. In roder to accomplish this goal, three different indices are proposed: mean absolute power, mean power dispersion and mean power lost. At the same time, the description and analysis of the motion is based on a set of locomotion variables, namely: step length, hip height, hip ripple, hip offset, foot claerance and link lengths. The influence of these variables on the energy flow is discussed and the results compared with those observed in nature.
- On the optimal configuration of redundant manipulatorsPublication . Duarte, Fernando B. M.; Tenreiro Machado, J. A.Redundant manipulators have some advantages when compared wih 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 manipulators, the proposed kinematic control algorithms adopt generalized inverse matrices. In this line of thought, the generalized inverse control scheme is tested through several experiments that reveal the difficulties that often arise, namely by showing that we may get non-optimal arm configurations and chaotic-like motions. Motivated by these problems this paper presents a new method that optimizes the manipulability through a least square polynominal approximation to determine the joints positions. The experiments confirm the superior performance of the proposed algorithm for redundant and hyper-redundant manipulators.
- On the multifrequency calculation of robot trajectoriesPublication . Tenreiro Machado, J. A.; Rudas, Imre J.; Cordeiro, Carla S. M.The computational burden of robot trajectory planning algorithms may be significant, namely when the inverse kinematics is required. Nevertheless, the variables involved (e.g. positions, velocities and accelaration) have distinct bandwidths. Therefore, they have different effects upon the final result and we can adopt a multifrequency strategy for the calculatinos, namely using different frequencies for the robot joint positinos, velocities and accelarations. In this line of thought, this paper compares a multirate trajectory planning scheme in the cartesian space in contrast with classical monofrequency calculation strategy.