Robust Sliding Mode Observer Research Articles

FDI Based on High-gain Robust Sliding Mode Observers

This paper considers the problems of actuator and sensor fault detection and isolation for a class of uncertain linear systems. By introducing an augmented vector, an augmented system which contains a fault vector consisting of both the actuator and sensor faults of original system is constructed. An auxiliary output vector is proposed so that the observer matching condition for the new augmented system is satisfied. A high-order sliding mode observer is considered to obtain the exact estimates of the auxiliary outputs. Then, a robust sliding mode observer is developed as fault detection observer to detect actuator and sensor faults. Furthermore, multi-observers are used for the actuator and sensor fault isolation purpose. Finally, a numerical simulation example is given to show the effectiveness of the proposed methods.

Sliding Mode Observer-Based Fault Reconstruction for Uncertain Linear Systems

Problem statement: Fault reconstruction scheme is different from the majority of Fault Detection and Isolation (FDI) methods described in the literature in the sense that it not only detects and isolates the fault, but provides an estimate of the fault. This approach is very useful for incipient faults and slow drifts, which are very difficult to detect. Also, this approach is very useful for Fault Tolerant Control (FTC) systems in the sense that instead of reconfiguration of the control system, the faulty sensors or actuators can be corrected and the simple control method can still be effectively used. Motivated by these useful features of fault, we are interested in performing observer-based fault reconstruction scheme for uncertain linear systems. Approach: In this study we present a scheme to design robust sliding mode observer for linear systems where both faults and uncertainties are considered. The objective is to derive a sufficient condition using Linear Matrix Inequalities (LMIs) for the stability of the observer. The so-called equivalent output error injection is discussed for fault reconstruction. Results: we get a simple sliding mode observer design for detection and reconstruction of faults for uncertain linear systems. Conclusion: With the real model of the seventh-order aircraft we show that the methods provided by present paper have good performances.

ℋ︁∞ sliding mode observers for uncertain nonlinear Lipschitz systems with fault estimation synthesis

AbstractThis paper presents a scheme to design robust sliding mode observers(SMO) with ℋ︁∞ performance for uncertain nonlinear Lipschitz systems where both faults and disturbances are considered. We study the necessary conditions to achieve insensitivity of the proposed sliding mode observer to the unknown input(fault). The objective is to derive a sufficient condition using linear matrix inequality(LMI) optimization for minimizing the ℋ︁∞ gain between the estimation error and disturbances, while at the same time the design method guarantees that the solution of the LMI optimization satisfies the so‐called structural matching condition. The sliding motion affects only a part of the system through a novel reduced‐order sliding mode controller. Furthermore, the so‐called equivalent control concept is discussed for fault estimation. Finally, a numerical example of MCK chaos demonstrates the high performance of the results compared with a pure SMO. Copyright © 2010 John Wiley & Sons, Ltd.

Smooth adaptive sliding mode observers in uncertain chaotic communication

We study the performance of adaptive sliding mode observers (ASMO) in chaotic synchronization and communication in the presence of uncertainties. The proposed robust adaptive observer-based synchronization is used for cryptography based on non-linear chaotic masking modulation (NCM). Uncertainties are intentionally injected into the chaotic dynamical system to achieve higher security and we use robust sliding mode observer design methods for the uncertain non-linear dynamics. In addition, a relaxed matching condition and a boundary layer smooth gain are introduced to realize the robust observer design more feasibly. A brief study in introducing an alternative augmented ASMO-based chaotic communication configuration will be discussed. Finally, a Lorenz system is employed as an illustrative example to demonstrate the effectiveness and feasibility of the proposed cryptosystem.

Tracking unmodelled signals of nonlinear systems via robust sliding mode observer: Application to reacting systems

The problem of the on-line estimation of the reaction heat in a continuous stirred tank reactor from temperature measurements is addressed in this paper. The proposed uncertainty observer is based on differential algebraic techniques, such that the algebraic observability condition of the uncertainty from noisy temperature measurements is easily verified and the observer structure is very simple, which lead to feasible implementation. The observer proposed is robust against noisy measurements and sustained disturbances. The good performance of the observer is shown by means of numerical simulations.

Synchronization of uncertain chaotic systems using a single transmission channel

This paper proposes a robust sliding mode observer for synchronization of uncertain chaotic systems with multi-nonlinearities. A new control strategy is proposed for the construction of the robust sliding mode observer, which can avoid the strict conditions in the design process of Walcott-Żak observer. A new method of multi-dimensional signal transmission via single transmission channel is proposed and applied to chaos synchronization of uncertain chaotic systems with multi-nonlinearities. The simulation results are presented to validate the method.

Development of a Robust Nonlinear Observer for a Single-Link Flexible Manipulator

Accurate measurements of all the state variables of a given system are often not available due to the high cost of sensors, the lack of space to mount the transducers or the hostile environment in which the sensors must be located. The purpose of this study was to design a robust sliding mode observer that is capable of accurately estimating the state variables of the system in the presence of disturbances and model uncertainties. It should be emphasized that the proposed observer design can handle state equations expressed in the general form. The performance of the nonlinear observer is assessed herein by examining its capability of predicting the rigid and flexible motions of a compliant beam that is connected to a revolute joint. The simulation results demonstrate the ability of the observer in accurately estimating the state variables of the system in the presence of structured uncertainties and under different initial conditions between the observer and the plant. Moreover, they illustrate the deterioration in the performance of the observer when subjected to unstructured uncertainties of the system. Furthermore, the nonlinear observer was successfully implemented to provide on-line estimates of the state variables for two model-based controllers. The simulation results show minimal deterioration in the closed-loop response of the system stemming from the usage of estimated rather than exact state variables in the computation of the control signals.