SATURATION FAULT-TOLERANT CONTROL FOR LINEAR
PARAMETER VARYING SYSTEMS
Ali Abdullah
Kuwait University, Electrical Engineering Department, P. O. Box 5969, Safat-13060, Kuwait
Keywords:
Fault diagnosis, fault-tolerant systems, parameter estimation.
Abstract:
This paper presents a methodology for designing a fault-tolerant control (FTC) system for linear parameter
varying (LPV) systems subject to actuator saturation fault. The FTC system is designed using linear matrix
inequality (LMI) and model estimation techniques. The FTC system consists of a nominal control, fault
diagnostic, and fault accommodation schemes. These schemes are designed to achieve stability and tracking
requirements, estimate a fault, and reduce the fault effect on the system. Simulation studies are used to
illustrate the proposed design.
1 INTRODUCTION
In recent years, the ﬁeld of designing FTC systems
has received considerable attention (Blanke et al.,
2001; Bodson, 1995; Isermann et al., 2002; Patton,
1997; Rauch, 1994; Stengel, 1991). For the case of
actuator fault, most of this research had addressed
fault accommodation for system subject to parame-
ter variation or frozen output. Other types of actua-
tor fault have been rarely considered. In this paper,
a methodology for designing FTC system for LPV
systems subject to a reduction in the actuator satura-
tion limit is presented. The LPV systems are deﬁned
as a class of linear time-varying systems whose state
space matrices depend on a set of parameters that are
bounded and can be measured or estimated online.
In the case of using an analytical approach, the main
idea behind fault tolerance is the use of fault diagnos-
tic and accommodation schemes. A fault diagnostic
scheme driven by plant measurements is used to de-
tect, locate, and estimate faults; while a fault accom-
modation scheme driven by fault information from the
diagnostic scheme is used to modify the nominal con-
trol law in order to reduce the fault effect on the sys-
tem. Based on the above idea, the total task of the
proposed FTC system is divided into three parts:
• Plant control: attempts to stabilize the closed-loop
system and provide the desired tracking properties
in the absence of faults. The controller is designed
using LPV technique (Apkarian et al., 1995; Ap-
karian and Adams, 1998; Gahinet et al., 1996;
Kose et al., 1998; Tuan and Apkarian, 2002).
• Fault diagnosis: deals with the problem of satura-
tion fault detection, location, and level estimation.
To achieve that, a suitable LPV model is derived
to describe the faulty system. Then the results in
(Polycarpou and Helmicki, 1995) are used to con-
struct the diagnostic scheme.
• Fault accommodation: attempts to reduce the fault
effect on the system by modifying the nominal
control law through the reference reshaping ﬁl-
ter and feed-forward gain. The accommodation
scheme is designed with the help of the bounded
real lemma for LPV system presented in (Gahinet
et al., 1996).
The notation
H (A ,B ,C ,D ,E ,F ) is used through-
out the paper to denote the symmetric matrix
A B C
B
T
D E
C
T
E
T
F
.
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