Fault Detection for Networked Systems with Uncertain
Time-Delay and Packet Dropout using Delta Operator
Xinyu Dong, Duanjin Zhang*
School of Information Engineering, Zhengzhou University.
Zhengzhou 450001, China
E-mail: xinyudong715@163.com, djzhang@zzu.edu.cn
Abstract—This paper addresses the problem of observer-
based fault detection for networked control systems (NCSs) with
uncertain time-delays and data packet dropouts. The uncertain
time-varying delays and packet dropouts of NCSs are modeled as
parameter uncertainties of th e NCSs and a stochastic variable
satisfying Bernoulli distribution, respectively. Combining with
the delta operator theory, a new discrete model is constructed to
depict the behavior of the NCSs. Then, based on the established
model, an observer-based H
fault detection filter is proposed to
guarantee the stability of the delta operator system and the
sufficient conditions of the H
performance for the filtering error
system are derived with linear matrix inequalities (LMIs) and
Lyapunov-Krasovskii functional technique. The parameters of
the filter are solved via LMI toolbox. A simulation example is
provided to illustrate the effectiveness of the proposed method.
Keywords—networked control systems; Delta operator; fault
detection; uncertain time-delay; packet dropout; LMI
I. I
NTRODUCTION
Networked control systems (NCSs) are feedback control
systems with closed-loops via a real-time shared network,
which have several advantages such as reduced cost, simpler
maintenance and installation. Owing to NCSs’ prominent
features, more applications of them have been developed such
as automobiles control systems, intelligent building, unmanned
air vehicles and tele-surgery. However, because of the limited
of network bandwidth, the communication network also brings
some problems, such as network-induced delay, packet
dropouts and network congestion [1-2], which could degrade
the system performance and even destabilize the system.
Therefore, the research of fault detection (FD) for NCSs is of
great significance and it has attracted a great deal of attention.
In recent years, the modeling of network-induced delay and
data packet dropouts which existing in NCSs are mainly
constructed by the following methods: 1) By using Markov
random process, NCSs with uncertainties are transformed into
Markov jump linear systems(MJLS). In [3-4], Considering the
influence of the Markovian packet dropouts and the unknown
short delay which can be treated as norm-bounded
uncertainties, the NCSs were modeled as the uncertain MJLS.
References [5-6] described the phenomenon of packet dropouts
as a Markov random process. 2)The NCSs including time-
delay and packet dropout are described by the Bernoulli
distributed sequence. In [7-8], the problems of H
filtering for
NCSs with packet dropouts were discussed.
Most of these studies focused on the discrete-time systems
formulated by traditional shift operator. However, traditional
shift-operator-based methods may bring about the problems of
crowding poles located in the boundary of stability circle when
sampling is fast. With regard to high sampling rate, Goodwin
adopted delta operator instead of shift operator to discretize
continuous systems [9]. Furthermore, delta operator system has
been studied extensively due to its excellent performances [10-
13] and its practical applications have been extensively
highlighted. Nonetheless, the fault detection observer design
problem of NCSs via delta operator approach has not been
fully researched and the observer-based FD for NCSs with
uncertain time-delays and packet dropouts using delta operator
has not been investigated yet, that constitutes the main
motivation of this paper.
In this paper, the FD problems of NCSs subject to uncertain
time-delays and packet dropouts via delta operator are
investigated. The unknown networked-induced delays are
convert to the parameter uncertainties of the system. By
introducing a stochastic variable satisfying Bernoulli
distribution to describe the missing of data packet and
considering the definition of delta operator, a new delta
operator discrete system model is established. Based on the
established model and stability theory, a state observer of the
system is designed to detect faults. The sufficient conditions
for the stability of the NCSs and the existence of the FD filter
can be derived with LMI and fault observer technique.
II. D
ELTA OPERATOR SYSTEM WITH UNCERTAIN TIME-DELAY
AND PACKET DROPOUT
Consider the continuous-time linear time-invariant(LTI)
system described by
() () () () ()
() ()
df
xt AxtButBdtBft
yt Cxt
%% %
!
∀
!
#
(1)
where
()
m
xt R∃
is the state of the plant,
()
n
yt R∃
is the
measurement output,
()
s
ut R∃
is the control input,
()
p
dt R∃
is the external disturbance which belongs to
2
[0, ]l %
,
()
q
ft R∃
is the fault signal. Suppose that
,, , ,
df
ABB B C
,are
real matrices of the appropriate dimensions.
Some reasonable assumptions are given to this system:
*This work is supported by National Natural Science Foundation of China
under Grant 61471323, and the Key Program of Science Technology of
Educational Department of Henan of China under Grant 14A120004
189
978-1-4673-8644-9/16/$31.00
c
2016 IEEE