Every closed-loop system holds a level of fault tolerance, which could be increased by using a fault tolerant control (FTC) scheme. In this paper, an efficient FTC scheme for a class of nonlinear systems (Euler-Lagrange ones) is proposed, which guarantees high performance and stability in a faulty system. This scheme was designed on the basis of a cascade control structure in which the inner loop is the closed-loop system and the external loop is the FTC, a generalized proportional integral (GPI) observer-based controller, which manages the fault tolerance level increment. An important issue of the proposed scheme is that the GPI observer-based controller jointly estimates disturbances and faults, providing information about the state of health of the system, and then compensates their effect. The scheme is efficient because only the inertia matrix is required for the controller design, it is able to preserve the nominal control law unchanged and can operate properly without explicit information about system faults (fault diagnostic module). Simulation results, on a pendulum model, show the effectiveness of the proposed scheme for tracking control.
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Sliding mode and fuzzy logic control have been combined together in a variety of ways. In this paper, a novel direction to design fuzzy sliding controllers is proposed based on the approach of Ben-Ghalia et al. Which is able to provide a fuzzy set based on a decoupled and linear system obtained after the application of the feedback- linearization control to the model of an induction motor. On the other hand, a Luenberger observer is conceived in the present work to observe the rotor flux in the motor which is too important to permit the application of fuzzy modeling approach and ensure the optimal and required performances . Furthermore, another objective to use such an observer consists in stabilizing the system and rejecting the disturbances when the system is subjected to uncertainties. Furthermore, to overcome the problem of the chattering phenomenon generated by the application of conventional sliding mode control applied to the cascade structure of the motor, the approach of fuzzy sliding mode control based on the fuzzy modelling proposed by Ben-Ghalia is used. The robust fuzzy control design is made feasible without resorting to model simplification or imposing restrictive conditions on the system uncertainty. Finally, simulation results proves the capability of the proposed process to ensure a good performances and robustness which is the principal aim of this research
W pracy przedstawiono metodę projektowania kaskadowych dyskretno- ciągłych układów mechanicznych o żądanym widmie częstości. Metoda ta oparta jest na rozkładzie charakterystyki dynamicznej na ułamek łańcuchowy. Przedstawiono ponadto problem modyfikacji strukturalnej i parametrycznej otrzymanego układu.
EN
In the paper presents a method of design of mechanical systems with the assumed frequency spectrum, using the synthesis of the dynamical characteristics of the longitudinally vibrating discrete - continuous mechanical systems with cascade structure. This is of the continued fiaction expansion method. Moreover the modification of structural and parameters problem of obtained system has been presented.
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