Reconstrução de falhas em sistemas com atrasos variantes de medição utilizando observadores por modos deslizantes

Abstract

This thesis presents a novel method for actuator fault reconstruction under mea- surement delays by means of sliding mode observers. The delay duration is con- sidered arbitrary, and may be constant or time-variant, possibly uncertain. The proposed approach has the advantage of being applicable to systems with measure- ments delays with no limitation regarding its duration, contrasting to other methods of the literature. The developed technique is applied to the case of sampled-output systems, where is possible to wait for some samples and apply more efficient inter- polation filters to improve fault reconstruction. The use of a predictor to estimate the state and fault signals in current time allows the application of this method to design a closed loop control law that rejects or attenuates the effect of the fault on the system output. An observer-predictor strategy is developed using the PDE- Backstepping method, which combined to a sliding mode control law is used to regulate the system output to zero, rejecting the fault effect. Another observer pre- dictor is developed using least-squares identification methods to estimate unknown parameters of a fault assumed parametrized. An application of the developed meth- ods to a simplified model of an intelligent completion valve used in oil and gas industry is also presented. In summary, the main contributions of this thesis are the development of a time-shifted observer to reconstruct failures in systems with ar- bitrarily long measurement delays and in systems with sampled outputs, and their application to the development of closed loop control strategies for systems with measurement delays.