Composite Anti-disturbance Control for A Class of Uncertain
Nonlinear Systems Via Disturbance Observer and Adaptive
backstepping method
Huifeng Zhang
1
, Yuanwei Jing
1
, Xinjiang Wei
2
1. College of Information Science and Engineering, Northeastern University, Shenyang, 110004, China.
E-mail: weixinjiang@163.com
2. School of Mathematics and Information, Ludong University, Yantai, 264025, China
E-mail: weixinjiang@163.com
Abstract: A new anti-disturbance control scheme is proposed for a class of nonlinear systems subjecting to multi-source dis-
turbances in this paper. The uncertain multi-source disturbances are classified into two parts, one is the harmonic or constant
disturbance with partial known information, which can be formulated by an exogenous system, another one is unknown time-
varying disturbances. The nonlinear disturbance observer(NDO) is constructed separately from the controller design to estimate
the first kind of disturbance. By integrating NDO with adaptive backstepping technique, a novel composite anti-disturbance
control scheme is proposed for the nonlinear systems. Then the stability analysis of all signals of the closed-loop system is
presented. Simulation for a numerical example is given to demonstrate the effectiveness of the results.
Key Words: Disturbance attenuation; Nonlinear Disturbance observer; Adaptive control; Backstepping control.
1 Introduction
In the late 1980s, disturbance observer technique was first-
ly presented for a robotic system, where an observer was
proposed to estimate external disturbance [28]. The basic
idea of DOBC is to estimate the external disturbance with
disturbance observer, a feed-forward compensator is used in
the control part to reject the disturbance, and achieve the de-
sired performance, which has a simple structure, and pro-
vides a promising approach to handle system disturbances to
improve its robustness.
Most of the above-mentioned anti-disturbance methods
are used for systems with a single disturbance. However,
multiple disturbances exist in most practical systems rather
than single disturbances. In order to improve the control pre-
cision, it is necessary to investigate new anti-disturbance ap-
proaches for systems with multiple disturbances. For sys-
tems with multiple disturbances, DOBC has been integrat-
ed with the H∞ control, variable structure control, fuzzy
control, stochastic control and adaptive control methods and
etc [14,35-38,42]. Recently, the combination of DOBC with
fault tolerant controller has been reported [3], and in [15], a
nonlinear initial alignment approach for inertial navigation
system (INS) is first presented based on a new robust anti-
disturbance filter design against multiple disturbances.
The aforementioned disturbance observer based control
are mostly established in terms of linear matrix inequali-
ties(LMIs). When strong non-linearities exist in system-
s, the validity of using linear analysis and synthesis tech-
nique may be doubtful. As a result, disturbance observer-
based control(DOBC) for nonlinear systems has received
a great deal of attention. In the past few years, many re-
sults have been reported [7,8,31,39-41]. Chen [7] devel-
oped a nonlinear disturbance observer(NDO) for a single-
input-single-output (SISO) non-linear system and applied it
The work is supported by National Science Foundation of China
61374108; Special research funds of forestry public service industry, China
201304515-3.
to a two-link manipulator. [8] presents a general framework
for nonlinear systems using disturbance observer based con-
trol(DOBC) techniques. Then composite methods that com-
bine DO with terminal sliding model control and adaptive
control were proposed in [5,31,41]. In [5], an initial non-
linear disturbance observer is proposed, based on the output
of the disturbance observer, an SMC scheme is presented
for the nonlinear system, and the stability of the closed-loop
system is established using Lyapunov method. But the dis-
turbance d is an unknown bounded constant that is
˙
d =0.
In [41], a nonlinear disturbance observer(NDO) is designed,
and a NDO-based SMC method is developed to counterac-
t the mismatched disturbance. But the disturbance in it is
assumed to satisfy the condition that the derivative of the
disturbance is bounded and satisfies lim
t→0
˙
d(t)=0. In [31],
a novel control scheme combining adaptive disturbance ob-
server technique and back-stepping method is proposed for a
class of nonlinear system with multiple disturbances. But in
[31], the disturbance observer is linear, the system is linear
for principal part, and the disturbances include an unexpect-
ed nonlinear signal presented as a nonlinear function except
for single harmonic or constant disturbances.
In this paper, we consider a more general nonlinear sys-
tem with multi-source mismatched disturbances. The distur-
bances include two parts, one is external disturbance which
can be formulated by an exogenous system, the other one is
unknown time-varying disturbances, which is more common
than unexpected nonlinear signal in practical systems. For
the first kind of disturbances, we construct a nonlinear dis-
turbance observer(NDO), and adaptive backstepping method
is used to attenuate the second disturbance. Then the com-
posite controller is presented based on the NDO and adaptive
backstepping technique. The remaining part of the paper is
organized as follows. Section 2 presents the problem formu-
lation and preliminaries. In section 3, the nonlinear distur-
bance observer(NDO) is proposed, then NDO based adap-
tive backstepping control design and the stability analysis of
Proceedings of the 34th Chinese Control Conference
Jul
28-30, 2015, Han
zhou, China
2907