ISEP – DEE – Comunicações em eventos científicos
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- A smooth variable structure control algorithm for robot manipulatorsPublication . Machado, J. A. Tenreiro; Carvalho, J. L. Martins deA new sliding controller is proposed. Second order linear system sliding curves eliminate the reaching phase and consequently and associated problems of load sensitivity and high demanded torque. Moreover, the chattering usually present in the sliding phase also disappears with the new control law. Simulation results show a negligible coupling between axes, thus enabling an easier and more efficient controller adjustment. It is also shown that the controller parameter set can be easily adjusted, and there is a large set of possible quasi-optimal values. This is of utmost importance, when one thinks of the industrial applications of this type of algorithms. Experiments were developed based on the position control problem. Nevertheless, generalization to the trajectory tracking problem is trivial. In either case the controller computational requirements are low, thus well adapted to today's microprocessor based digital control technology.
- A real-time system for robot manipulator inverse dynamics computationPublication . Machado, J. A. Tenreiro; Carvalho, J. L. Martins de; Matos, J. A. SilvaA new robot manipulator inverse dynamics computational algorithm is announced. The novel feature resides in the computations which are a blend of ordinary and Boolean algebra. As such, this method may also be interpreted as a dedicated compiler that optimizes the on-line conputing time at expenses of the off-line stage. Nevertheless, the high off-line requirements are alleviated, through the derivation of some general ruls that stem from the structure of the robot manipulator equations. Moreover, the on-line computing time is further optimized through the use of Binary Decision Diagrass. The results show a considerable computational improvement on a conventional sequential machine. Furthermore, they clearly point out new computational parallel architectures, without schedualing problems, and where performance improvement is proportional to the number of processors. Finally, it is observed that the proposed algorithm is not restricted to robot inverse dynamic computations, but is also applicable to many other real-time computing structures.
- An Efficient algorithm for robot manipulators dynamic computationPublication . Tenreiro Machado, J. A.; Matos, J. S.; Carvalho, J. M.; Costa, A. C.Despite recent advances in robot manipulator inversc dynamic computing methods, the development of industrial implementations of real-time controllers is still highly difficult, and impractical, due to the large mumber of arithmetic and transcendental floating point operations involved. The paper presents a method based on the use of a combination of boolean ond ordinary algebra that leads to a considerable reduction of the on-line computing time. Terms of the link torque equations are calculated by boolean algebra, using Binary Decision Diagrams, and are then combinated by arithmetiic summations. The result is an efficient computational technique for real-time robot manipulator nonlinear control which is well suited to today's digital technology. The method, which is not restricted to the particular application described in the paper, is well adapted to implementation on a parallel architecture with performance improvement porportional to the number of processors, and without scheduling problems.
- A new variable structure controller for robot manipulatorsPublication . Tenreiro Machado, J. A.; 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. The results show a remarkable improvement over conventional VSS controllers, maintaining, however, a low computationla complexity which make it well suited for microcomputer implementation. Furthermore, the well known standard heuristic procedures of controller adjustment can be used in the proposed scheme. This is of utmost importance in an industrial environment.
- An efficient computational scheme for robot manipulatorsPublication . Tenreiro Machado, J. A.; Carvalho, J. L. Martins de; Matos, J. A. SilvaA new robot manipulator computational scheme which is a blend of ordinary and Boolean algebra is presented. This method may also be interpreted as a dedicated compiler that optimizes the on-line computing time at expenses of the off-line stage. The off-line requirements are alleviated, by the implementation of some general rules that stem from the structure of the robot manipulator equations, and the on-line computing time is optimized through the use of Binary Decision Diagrams. The results show a considerable computational improvement on conventional sequential machines but, furthermore, they clearly point out new computational parallel architectures. Finally, it is observed that the proposed algorithm is not restricted to robot dynamic computations, but is also applicable to many other computing structures.
- Robot manipulator dynamics - Towards better computational algorithmsPublication . Tenreiro Machado, J. A.; Carvalho, J. L. Martins de; Matos, J. A. Silva; Costa, António M. C.A new robot manipulator inverse dynamics computational algorithm is announced. The novel feature resides in the computations which are a blend of ordinary and Boolean algebra. As such, this method may also be interpreted as a dedicated compiler that optimizes the on-line computing time at expenses of the off-line stage. Nervertheless, the high off-line requirements are alleviated, through the derivation of some general rules that stem from the structure of the robot manipulator equations. In a practical implementation, a copmuter program based on a Quine-McCluskey truth table simplification method was used and experimented on a 2R robot manipulator. The results show a considerable computational improvement on a conventional sequential machine. Furthermore. they clearly point out new comptutational parallel architectures, without scheduling problems, and where performance improvement is porportional to the number of processors. Finally, it is observed that the proposed algorithm is not restricted to robot inverse dynamic computations, but also applicable to kinematic and control computations.
- A statistical approach to the analysis and design of robot manipulatorsPublication . Tenreiro Machado, J. A.; Carvalho, J. L. Martins deA new approach the the analysis and design of robot manipulators is announced. 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 nature lead to very precise results and strategies but, can be very complex to tackle. This motivates the need of models based on other mathematical comcepts having distinct characteristics. The proposed statistical scheme is a step in that direction which gives clear guidelines towards the robot kinematic and dynamic optimization. Furthermore, the inherent use of histograms allows not only fast calculation procedures, but above all, the use of experimental data; consequently, complex dynamic modelling exercises can be avoided.
- 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.
- 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.