In this thesis, model based fault detection, isolation, and estimation problem in several classes of nonlinear systems is studied using sliding mode and learning approaches. First, a fault diagnosis scheme using a bank of repetitive learning observers is presented. The diagnostic observers are established in a generalized observer scheme, and the observer inputs are repetitively updated using t...

This paper presents a brief study on the design and performance comparison of conventional first-order and super-twisting second-order sliding mode observers for some nonlinear control systems. Estimation accuracy, fast response, chattering effect, peaking phenomenon and robustness are considered for nonlinear systems under observer-based output feedback control and state feedback control.

– In this chapter, we provide the key ideas on how to build software sensors (also called observers) for wastewater treatment plants (WWTPs). We give an overview of the existing linear and nonlinear observers and discuss criteria that help to identify which observer is best suited with respect to the amount of information being available for the WWTP. Depending on the model reliability, the ava...

This paper shows how the theory of adaptive observers can be effectively used in the design internal models for nonlinear output regulation. The main result obtained in this way is a new method for the synthesis of adaptive internal models which substantially enhances the existing theory of adaptive output regulation, by allowing nonlinear internal models and more general classes of controlled ...

In this paper we propose a new method for fault detection and isolation based on adaptive observers. Each adaptive observer estimates the state variables and one of the parameters of the monitored system. The algorithms for both residual generation and evaluation are presented in detail. The proposed method is applicable to all nonlinear dynamic systems for which the required observers and adap...

In the control systems literature, it is well known that a separation principle holds locally for nonlinear control systems, when exponential feedback stabilizers and exponential observers are used. In this paper, we present a counterexample to show that the global separation principle need not hold for nonlinear control systems. Our example demonstrates that global stability might be lost when...

This paper presents a simplified nonlinear observer for power systems by exploring the special features of the nonlinear power system model. Rather than directly applying the existing nonlinear observer theory to the 6 order nonlinear power system model, the model is first decoupled into a 3 order nonlinear subsystem and a 3 order linear subsystem. Low order observers are designed for each subs...