Browsing by Issue Date, starting with "1998-06-29"
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- Redundancy optimization for mechanical 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 manipulators, the proposed kinematic control algorithms adopt generalized inverse matrices. In this line od 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.
- Man-machine processes in modelling based engineering activitiesPublication . Horváth, László; Rudas, Imre J.; Tenreiro Machado, J. A.This paper discusses the man-machine interaction process in collaborative engineering systems where decisions of humans are assisted by computer procedures. Recent development in communication, multimedia, modelling and knowledge engineering techniques brought a new age in human-computer interface processes. Authors propose a model of the man-machine interaction that can be applied in CAD/CAM and flexible manufacturing systems. The paper is organized as follows. Firstly, computer environment of the group work of engineers is outlined. Then a model of the man-machine system is proposed. The approach to modeling human and computer activities is discussed with an emphasis on handling human intent. Following this, communication between engineers is analysed and the concept of human intent and its saving by explanation based methods are expalined. Finally impact of human-computer procedures on the engineering design and plannig work is concluded.
- Dynamic performance of biped locomotion systemsPublication . Silva, Filipe M.; Tenreiro Machado, J. A.This paper presents the energy analysis of a bipedal walking system. The main goal is to understand the movement strategies in walking and the search for the optimal locomotion variables that minimise the energy comsunption. In order to accomplish this goal, a set of locomotion variables is used in the description and analysis of motion. The locomotion variables considered are the following: step length, hip height, hip ripple, hip offset, foot clearance, link lenghts and link masses. Based on thes variables and their influence on the energy flow, the performance is discussed and the results are compared with those observed in nature.
- Position/force fractional control of mechanical manipulatorsPublication . Tenreiro Machado, J. A.; Azenha, AbílioIn this paper it is studied the implementation of fractional-order algorithms in the position/force hybrid control of robotic manipulators. The system robustness and performances are analysed, in terms of time responses, and compared with other control approaches. Moreover, it is also investigated the effect of nonlinear phenomena at the robot joints such as nonlinear friction, dynamic backlash and flexibility.