Automatica 75 (2017) 127–132
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Automatica
journal homepage: www.elsevier.com/locate/automatica
Brief paper
Continuous observer design for a class of multi-output nonlinear
systems with multi-rate sampled and delayed output measurements
✩
Yanjun Shen
a
, Daoyuan Zhang
a
, Xiaohua Xia
b
a
Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, China Three Gorges University, Yichang, Hubei, 443002, China
b
Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Pretoria 0002, South Africa
a r t i c l e i n f o
Article history:
Received 25 October 2014
Received in revised form
18 July 2016
Accepted 20 August 2016
Keywords:
Hybrid systems
Continuous observer
Multi-rate
Delayed measurements
a b s t r a c t
In this paper, continuous observer is designed for a class of multi-output nonlinear systems with multi-
rate sampled and delayed output measurements. The time delay may be larger or less than the sampling
intervals. The sampled and delayed measurements are used to update the observer whenever they are
available. Sufficient conditions are presented to ensure global exponential stability of the observation
errors by constructing a Lyapunov–Krasovskii function. A numerical example is given to illustrate the
effectiveness of the proposed methods.
© 2016 Elsevier Ltd. All rights reserved.
1. Introduction
Recently, the problem of design global convergent observers for
nonlinear systems has made great progress. For the observation
of nonlinear systems, one can use extended Luenberger observers
(Zeitz, 1987), normal form observers (Bestle & Zeitz, 1983;
Krener & Isidori, 1983; Xia & Gao, 1988, 1989), Lyapunov based
observers (Raghavan & Hedrick, 1994; Thau, 1973), high-gain
observers (Gauthier, Hammouri, & Othman, 1992; Gauthier &
Kupka, 1994), sliding mode observers (Haskara, Özgüner, &
Utkin, 1998) and moving horizon/optimization based observers
(Michalska & Mayne, 1995). Among these methods, high-gain
observers play an important role and can be used to a large class
of nonlinear systems with a triangular structure after a coordinate
change. New developments of high gain observers have been
carried out in various directions (Andrieu, Praly, & Astolfi, 2009;
Deza, 1991; Deza, Bossanne, Busvelle, Gauthier, & Rakotopara,
1993; Gauthier et al., 1992; Praly, 2003). For example, the result
✩
This work was supported by the National Science Foundation of China
(61374028, 61273183), the Scientific Innovation Team Project of Hubei Provincial
Department of Education (T201504). The material in this paper was not presented
at any conference. This paper was recommended for publication in revised form by
Associate Editor Dragan Nesic under the direction of Editor Andrew R. Teel.
E-mail addresses: shenyj@ctgu.edu.cn (Y. Shen), 944732896@qq.com
(D. Zhang), xxia@up.ac.za (X. Xia).
of Gauthier et al. (1992) is extended to a class of nonlinear
systems where the nonlinear terms admit an incremental rate
depending on the measured output (Praly, 2003). In Deza (1991),
the authors considered observer design for multi-input and multi-
output (MIMO) nonlinear systems. The result has been extended
to a class of MIMO nonlinear systems, in which interconnection
between the blocks are not allowed (Deza et al., 1993). Based on
the observer normal form, another extension for the multi-output
systems has been studied in Rudolph and Zeitz (1994). However,
the nonlinearity of each block does not allow the unmeasurable
states of its own block. Under the conditions of observability and
triangular structure, a nonlinear system can be transformed into
the block low triangular form considered in Shim, Son, and Seo
(2001) by a coordinate transformation. Then, semi-global observer
has been designed for nonlinear systems with interconnections
between the subsystems (Shim et al., 2001). The nonlinear system
with block lower triangular form is rather general when nonlinear
changes of coordinates are allowed. It includes the control-affine
multi-input and single-output (MISO) nonlinear systems which
are strongly observable for any input (Gauthier et al., 1992) and
the control-affine MIMO nonlinear systems which are strongly
observable for any input for each output taken separately (Deza,
1991). Moreover, it can be used to express some physical systems.
For example, the dynamical equations of a permanent magnet
stepper motor can be transformed into the block lower triangular
form Mahmoud and Khalil (2002). The estimation errors can
converge to the origin in finite-time by using high gain observers
http://dx.doi.org/10.1016/j.automatica.2016.09.028
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