2268 IEEE TRANSACTIONS ON SYSTEMS, MAN, AND CYBERNETICS: SYSTEMS, VOL. 47, NO. 8, AUGUST 2017
Adaptive Neural-Fuzzy Sliding-Mode Fault-Tolerant
Control for Uncertain Nonlinear Systems
Shiping Wen, Michael Z. Q. Chen, Senior Member, IEEE, Zhigang Zeng, Senior Member, IEEE,
Tingwen Huang, Senior Member, IEEE, and Chaojie Li
Abstract—This paper proposes an adaptive neural-fuzzy
sliding-mode control method for uncertain nonlinear systems
with actuator effectiveness faults and input saturation. The
parameter dependence of the control scheme is removed from
the bound of actuator faults by updating online. A neural-fuzzy
model is developed to approximate the uncertain nonlinear
terms and a sliding-mode online-updating controller is developed
to estimate the bound of the actuator with no prior knowl-
edge of the fault. The asymptotic stability is verified via the
Lyapunov method in the presence of actuator faults and satu-
ration. Furthermore, the adaptive neural-fuzzy control method
is extended to the uncertain faulty nonlinear systems with inte-
gral sliding-mode manifold as well as other popular sliding-mode
surfaces. A numerical example is presented to demonstrate the
effectiveness of the derived results.
Index Terms—Actuator fault, actuator saturation, neural-fuzzy
approximator, sliding-mode control (SMC), uncertain nonlinear
system.
I. INTRODUCTION
A
LONG with fuzzy logic and neural networks, intelligent
control systems have been developed rapidly over the
past few decades. Fuzzy-control methods have been utilized in
the complex ill-defined nonlinear systems with effective tech-
niques. Adaptive fuzzy control method was applied for uncer-
tain nonlinear systems [3]–[14], [33], [34]. In general, there
Manuscript received June 2, 2016; revised September 2, 2016 and
November 16, 2016; accepted January 1, 2017. Date of publication
February 22, 2017; date of current version July 17, 2017. This work was
supported in part by the Natural Science Foundation of China under Grant
61403152, Grant 61402218, Grant 61673187, and Grant 61673188, in part by
the Research Grants Council of Hong Kong through General Research Fund
under Grant 106140120, and in part by the NPRP Grant NPRP 8-274-2-107
from the Qatar National Research Fund (a member of Qatar Foundation). The
statements made herein are solely the responsibility of the authors. This paper
was recommended by Associate Editor C.-C. Tsai. (Corresponding author:
Zhigang Zeng.)
S. Wen is with the School of Automation, Huazhong University of Science
and Technology, Wuhan 430074, China, the College of Science, Engineering
and Technology, Hamad bin Khalifa University, 23874, Doha, Qatar, and
also with the Key Laboratory of Image Processing and Intelligent Control
of Education Ministry of China, Wuhan 430074, China.
M. Z. Q. Chen is with the Department of Mechanical Engineering,
University of Hong Kong, Hong Kong (e-mail: mzqchen@hku.hk).
Z. Zeng is with the School of Automation, Huazhong University of Science
and Technology, Wuhan 430074, China, and also with the Key Laboratory of
Image Processing and Intelligent Control of Education Ministry of China,
Wuhan 430074, China (e-mail: zgzeng527@126.com).
T. Huang is with Texas A&M University at Qatar, Doha 23874, Qatar
(e-mail: tingwen.huang@qatar.tamu.edu.cn).
C. Li is with the Platform Technologies Research Institute, RMIT
University, Melbourne, VIC 3001, Australia (e-mail: chaojie.li@rmit.edu.au).
Color versions of one or more of the figures in this paper are available
online at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TSMC.2017.2648826
are two main components in the developed controllers: first,
a fuzzy system is employed to achieve feedback cancellation;
second, to make sure the augmented system stable on the basis
of the Lyapunov method, a robust compensator such as back-
stepping control [15], sliding-mode control (SMC) [16], [17],
H
∞
control [18], determines the tuning parameters in the fuzzy
system. These methods make systems stable in robust con-
trol schemes. However, some specific constrained conditions
are imposed for uncertain nonlinear systems such as known
boundness of the approximation errors. To overcome the diffi-
culties such as external disturbances and approximation errors,
some hybrid control techniques have been developed with var-
ious control components [19]–[21]. Although these methods
achieve favorable performances, the number of fuzzy rules
increases dramatically when the nonlinear system demon-
strates more degrees of freedom, which increases the difficulty
to implement the real-time control. In recent, neural-fuzzy net-
works have emerged with the learning capability of neural
networks and being widely adopted in the adaptive control to
deal with uncertainties in order to achieve desired performance
criteria [22]–[32].
With the advantages of high robustness to external distur-
bances [33]–[38], SMC has been utilized in many applica-
tions [39]–[46]. An ideal sliding mode can be achieved by
driving the augmented system to satisfy certain equation gov-
erning the sliding mode for all time. On the other hand, the
nonlinear uncertain systems are generally controlled with high
gains by the SMC method, which can easily lead to a chat-
tering phenomenon, therefore, some interest has been paid to
combine a sliding mode controller with fuzzy logic control
for nonlinear systems [47]. Thus, neural-fuzzy control is com-
bined with the SMC to ensure global stability and robustness
to disturbances,
However, uncertainties and nonlinearities are considered in
the case of no actuator fault or failure during the entire con-
trol process in most of the previous research, which is hardly
existed in practice [48]–[50]. In this way, the whole con-
trol objective will be failed ultimately with an abrupt fault
occurrence if no fault tolerance capability has been considered
for the designed controller. Thus, the control design should
address the issue of fault tolerance capacity [51]–[55]. As
another critical issue, actuator saturation should be tackled
in nonlinear control as well as fault tolerant control [51].
Since the output of the augmented actuators will be satu-
rated or constrained sometimes, which will destabilize the
augmented systems. In consequence, a lot of controllers
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