Robust Fault Tolerant Control Framework Using Uncertain Takagi-Sugeno Fuzzy Models - Fuzzy Modeling and Control: Theory and Applications - page 111

Chapter 6
Robust Fault Tolerant Control Framework
Using Uncertain Takagi-Sugeno Fuzzy Models

Damiano Rotondo, Fatiha Nejjari and Vicenç Puig

6.1 Introduction

Fault tolerant control (FTC) has been consolidated as an important research topic in
the control applications during last years (Patton 1997 ; Blanke et al. 2006 ; Zhang and
Wang 2008 ). The objective of an FTC system is to maintain desirable closed-loop
performance, or with an acceptable degradation, and preserve stability conditions in
the presence of component and/or instrument faults. The accommodation capability
of a control system depends on many factors such as the fault severity, the robustness
of the nominal system and the presence of redundancy in the sensors and/or the actu-
ators. Generally speaking, FTC systems can be categorized into two main groups:
active and passive. The passive FTC techniques (Chen et al. 1998 ) are control laws
that take into account the fault appearance as a disturbance, with resulting conser-
vative control system performance. On the other hand, the active FTC techniques
involve adapting the control law by using the information given by the fault detection
and isolation (FDI) block (Blanke et al. 2006 ). With this information, some automatic
controller adjustments are done after the fault trying to guarantee acceptable control
objectives. The main advantage of active FTC techniques is that they overcome the
conservativeness of the passive FTC ones, but the price to pay is that the overall
system becomes more complicated and costly.
The Takagi-Sugeno (TS) framework has also been deeply studied in the automatic
control literature (Tanaka et al. 2001 ;Kluska 2009 ). Introduced in Takagi ( 1985 ),
TS systems provide an effective way of representing nonlinear systems with the aid