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Journal of Engineering Science and Technology Review 8 (2) (2015) 17-23
Special Issue on Synchronization and Control of Chaos: Theory,
Methods and Applications
Research Article
Adaptive Synchronization of Memristor-based Chaotic Neural Systems
Xiaofang Hu
1
and Shukai Duan
*, 2
1
Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong, China.
2
School of Electronics and Information Engineering, Southwest University, Chongqing, 400715 China.
Received 13 September 2014; Revised 17 October 2014; Accepted 15 November 2014
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Abstract
Chaotic neural networks consisting of a great number of chaotic neurons are able to reproduce the rich dynamics
observed in biological nervous systems. In recent years, the memristor has attracted much interest in the efficient
implementation of artificial synapses and neurons. This work addresses adaptive synchronization of a class of
memristor-based neural chaotic systems using a novel adaptive backstepping approach. A systematic design procedure is
presented. Simulation results have demonstrated the effectiveness of the proposed adaptive synchronization method and
its potential in practical application of memristive chaotic oscillators in secure communication.
Keywords: Adaptive synchronization, memristors, chaos, chaotic systems, backstepping.
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1. Introduction
The memristor, defined by the relationship between the flux
and the charge of a device, was theoretically predicted by
Leon Chua in 1971 and called the fourth fundamental circuit
element after the resistor, the capacitor and the inductor [1].
In 2008, Williams and his team from HP Lab proved the
existence of the memristor in nanoscale electronics while
developing ultra-high density nonvolatile memory [2].
Afterwards, the research on memristors or memristive
systems has gained ever-increasing attention from both
academia and industry [3-12]. In particular, many efforts
have been devoted into discovery of some important
properties of typical memristors [3,4], various memristive
devices and materials [5-7], as well as promising application
potentials [8-14].
Due to those pioneers’ valuable work, the key features of
the memristor can be summarized as follows.
(i) The memristor is a kind of nonlinear devices in simple
sandwiching structure, featuring hysteretic current-
voltage characteristic under periodic external excitation
conditions.
(ii) The memristor’s capabilities of nanoscale size, variable
resistance and power-off mode storage make it a
competitive candidate of the next-generation
nonvolatile memory [8,9].
(iii) The conductivity of a memristor depends on the total
flux/charge ever passing through it. This property is
very similar to the biological synaptic plasticity, that is,
the strength of a synaptic weight is in the control of the
ionic flowing through the synapse between two adjacent
neurons. Thereby, by combining the advantages of tiny
scale and simple structure, the memristor naturally
becomes the preferred artificial synapses in large-scale
and massively-parallel neuromorphic architectures that
merge computation and memory [10-11].
(iv) The memristor also has potential in nonlinear circuit
design and realization such as chaotic oscillators.
A novel implementation scheme for chaotic oscillators
using nanoscale memristors might achieve richer dynamic
behaviors with much smaller and simpler circuits, compared
with the traditional operational-amplifier-based method. In
fact, many memristive chaotic systems have been designed
and investigated [12-14]. The memristive element used in
most of these systems is the generalized memristor or
memristive system with an odd-symmetric flux-charge
characteristic similar to the current-voltage curve of Chua’s
diode [12]. Recently, more attention has been paid on
chaotic systems consisting of HP memristors [13,14]. In this
paper, the latter will be focused on.
Since the chaos synchronization was shown to be
possible by Pecora and Carroll [15], synchronization
between coupled chaotic systems has been extensively
investigated [16-20]. The concept of chaos synchronization
refers to making two identical chaotic dynamical systems
with different initial conditions oscillate in a
synchronized manner [20]. Up to now, various
synchronization phenomena have been observed in different
chaotic systems, including complete synchronization,
generalized synchronization, phase synchronization, lag
synchronization and so on [16]. In practical applications, it is
well known that synchronization plays an essential role in