ut K x t
such that the resulting closedloop system is stabilizable for the case without the controller failure
w here K is the controller gain to be determined Also suppose that the controller will completely fail
in some unknow n time interval and can be recovered through a time interval Then the states of the system
can be demonstrated by the following piecewise differential equation
x t
A
k
tx t A
h
tx t
ht
A tx t A
h
t x t
h t
w here
A
k
t A
BK
A t A t A
A t A
h
t A
h
A
h
t
Thus during all over operation the entire system dynamics can be rew ritten into a switched system
composed of both a stable system the closedloop system and an unstable system the openloop system
with controller not available
x t A
t
tx t A
h
t
tx t
h t
x t
t t
h
Where
t P A
t A
k
t A
t A t A
h
t A
h
t A
h
t
t means the controller works means the controller fails
Remark 2 T he stability analysis and controller design of system are considered
In
based on an average dwell time technique the exponential stability have been developed for sw itched
systems with timevarying delay but the lower bound of delay is restricted to be zero In the
delay is a constant value In this paper system is a special switched linear system w ith interval time
varying delay and controller failure The range of delay may vary in an interval for w hich the lower bound
is not restricted to be zero The objective of this paper is to find a class of switching laws to establish new
delayrangedependent stabilization conditions for system and design a state feedback controller such
that system is exponentially stable
Definition 1
For any switching signal
t and any T t let N
t T denote the number
of switching of
t on an interval t T If
N
T t N
T
t
a
N
a
holds constant
a
is called the average dwell time and N
the chatter bound As commonly used in the
literature we choose N
in this paper
Definition 2 T he system with a decay rate
is said to be robustly exponentially stable under
t if the solution x t of system satisfies
x t
ke
t
t
H
t
t
w here
H
sup
h
x t
x t
is the Euclidean norm
Lemma 1
For any constant symmetric matrix W scalar
and vector function
x
R
n
such that the following integration is w ell defined then
t
t
x
T
sZ
x sd s
z
T
t
W W
W
W
z t
w here
z t x
T
t x
T
t
T
Lemma 2
Let M D F E and M be real matrices of appropriate dimensions with M M
T
then
M
DFE
E
T
F
T
D
T
for all F
T
F
I
if and only if there exists a scalar
such that
M
DD
T
E
T
E
2 Main results
First consider the stability of the system with controller for the case w ithout controller failure
That is
x t A
k
tx t A
h
tx t
ht
w here A
k
t A t BK A
k
A t A BK A t
第 期 WANG Limin et al Delayrangedependent robust control for uncertain state delay systems with