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ROBUST FAULT-TOLERANT CONTROL OF LAUNCH VEHICLE VIA GPI
OBSERVER AND INTEGRAL SLIDING MODE CONTROL
Dang-Jun Zhao, Yong-Ji Wang, Lei Liu, and Zhi-Shen Wang
ABSTRACT
A robust fault-tolerant attitude control scheme is proposed for a launch vehicle (LV) in the presence of unknown external disturbances,
mismodeling dynamics, actuator faults, and actuator’s constraints. The input-output representation is employed to describe the rotational
dynamics of LV rendering three independently decoupled second order single-input-single-output (SISO) systems. In the differential
algebraic framework, general proportional integral (GPI) observers are used for the estimations of the states and of the generalized
disturbances, which include internal perturbations, external disturbances, and unknown actuator failures. In order to avoid the defects of the
conventional sliding surface, a new nonlinear integral sliding manifold is introduced for the robust fault-tolerant sliding mode controller
design. The stability of the GPI observer and that of the closed-loop system are guaranteed by Lyapunov’s indirect and direct methods,
respectively. The convincing numerical simulation results demonstrate the proposed control scheme is with high attitude tracking perform-
ance in the presence of various disturbances, actuator faults, and actuator constraints.
Key Words:
fault-tolerant control, launch vehicle, attitude control, integral sliding mode control, general proportional integral observer.
I. INTRODUCTION
Recently, many countries have focused on building heavy
lifting launch vehicles (HLLV) in order to facilitate their deep
space explorations, such as the Ares series of NASA, the Ariane
series of the European Space Agency, and the Long March series
of China, etc. HLLV is aerodynamically unstable, structurely
flexible, and strongly nonlinear, rendering a great challenge for
the design of ascent flight control systems. The main challenge is
to guarantee high performance in the presence of perturbations,
disturbances, mismodeling dynamics, and actuator faults, thus a
robust and reliable flight control system is necessarily demanded.
The conventional ascent flight control system is based on
the combination of the gain scheduling (GS) method and the
proportional-integral-differential (PID) controller, in which the
table look-up PID gains are scheduled over a set of operating
points along the given trajectory of LV. However, the GS tech-
nique is not very robust when facing a large deviation from the
nominal trajectory or system uncertainties. Consequently, many
advanced guidance and control techniques have been developed
for dealing with uncertainties and disturbances, such as, sliding
mode control [1], neural adaptive control [2], nonparametric
adaptive control [3], etc. However, all of these methods
mentioned above have not considered the case of actuator faults,
thus the scarcity of reliability.
In order to enhance the reliability of flight control systems,
a great number of investigations have been made (see two litera-
ture reviews [4, 5] on FTC and references therein). Such works
can be divided into two kinds, active and passive FTC. Generally
speaking, a diagnosis module is necessary for active FTC strate-
gies, while passive FTC strategies change control parameters
according to online observations. A reconfigured controller of an
active FTC scheme was designed for a satellite launch vehicle in
[6]. For passive FTC schemes, in [7] an FTC controller was
proposed based on dynamics inversion and time delay for attitude
tracking of a rigid satellite; an indirect adaptive fault scheme was
considered in [8] for a spacecraft attitude tracking problem under
thruster faults; in [9], three implicit estimation filters and an
attitude controller derived from the back-stepping technique were
employed in FTC design of spacecraft; an LMI based FTC
control method appeared in [10] for the tracking control of linear
parameter varying systems. Although the aforementioned control
methods have made splendid contributions, there are still some
defects to be improved. These methods deal with the system faults
and disturbances separately, rendering a complicated control
structure and a number of parameters to be tuned.
This work of a passive FTC strategy for the flight control of
LV is based on a general proportional integral (GPI) observer [11,
12] and a nonlinear integral sliding mode control (SMC) tech-
nique. In this brief paper, the actuator faults mainly refer to the
mechanism deadlock, while the thrust loss is not examined. The
nonlinear multiple-input-multiple-output (MIMO) system of LV
is divided into three independent second order single-input-
single-output (SISO) systems in the framework of differential
algebra originated by Fliess [13]. The disturbances, mismodeling
dynamics, and actuator faults are treated as a generalized
Manuscript received June 11, 2011; revised December 10, 2011; accepted April 18,
2012.
The authors are with Key Laboratory of Image Processing and Intelligent Control,
Department of Control Science & Engineering, Huazhong University of Science &
Technology, Wuhan, 430074, China. Yong-Ji Wang is the Corresponding author
(e-mail: wangyjch@mail.hust.edu.cn).
Dang-Jun Zhao is also with School of Aeronautics & Astronautics, Central South
University, Changsha, 410083, China.
This work was supported by National Nature Science Foundation of China
(60975058), the Nature Science Foundation of Hubei Province (2010CDB01904) and
the 2010 Spaceflight Support Foundation.
Asian Journal of Control, Vol. 15, No. 3, pp. 1–10, May 2013
Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/asjc.564
–Brief Paper–
© 2012 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society