Function projective synchronization

International Journal of Computer Science, Engineering and Information Technology (IJCSEIT), Vol. 4, No.5, October 2014
FUNCTION PROJECTIVE SYNCHRONIZATION
OF NEW CHAOTIC REVERSAL SYSTEMS
Olurotimi S. Ojoniyi
Department of Physics and Telecommunications, Tai Solarin University of Education,
Ijagun, Ogun State Nigeria.
ABSTRACT
In the present work, Lyapunov stability theory, nonlinear adaptive control law and the parameter update
law were utilized to derive the state of two new chaotic reversal systems after being synchronized by the
function projective method. Using this technique allows for a scaling function instead of a constant thereby
giving a better method in applications in secure communication. Numerical simulations are presented to
demonstrate the effective nature of the proposed scheme of synchronization for the new chaotic reversal
system.
KEYWORDS
Function projective synchronization, Lyapunov stability theory, chaotic system, new chaotic reversal
system.
1. INTRODUCTION
The chaotic dynamics observed only in nonlinear systems have been largely defined by
oscillations which are sensitive to initial conditions [1]. Lorenz and Rossler systems are
pioneering simple chaotic systems discovered with a lot of interesting properties that can model
physical systems [1]-[2]. This relatively new dynamical behaviour has since been discovered in
other disciplines such as engineering, science and economics. In order to understand fully most
nonlinear phenomenon in nature through interaction of systems, the control and synchronization
of chaotic oscillations is vital.
The process of controlling and synchronising chaotic systems has attracted much attention since
its discovery in less than twenty years [3]. The work of Pecora and Caroll [4] generated a wider
research in synchronization since it entails the synchronization of two identical chaotic systems
with different initial conditions.A number of methods of synchronization have been proposed
since the pioneering work of Pecora and Caroll such as complete synchronization, generalized
synchronization, phase synchronization, lag synchronization, adaptive synchronization, time-scale
synchronization, intermittent synchronization, projective synchronization and function
projective synchronization [5]-[9]. Function projective synchronization deserves much attention
since it has been found applicable and better in secure communication.
Function projective synchronization implies that the master and slave oscillators could be
synchronized up to a scaling function unlike a constant in the projective synchronization. The
DOI : 10.5121/ijcseit.2014.4503 33

advantage is that it becomes more complex to determine the function used and as a result more
secure communication is achieved under this scheme.
In the present work, function projective synchronization of new chaotic reversal systems [10]
with uncertain parameters using nonlinear adaptive controller has been investigated to
demonstrate the effectiveness of this scheme as it applies in secure communication. The
remaining part of this work is arranged as follows: section 2 is on the nonlinear adaptive
controller designed to synchronize the new chaotic reversal systems, section 3 is on numerical
simulations presented to demonstrate the robust nature of the scheme, and section 4 is the
conclusion of the paper.
In the present section, we examine briefly the dynamics of the new deterministic model for
chaotic reversal [10].
34
2. ADAPTIVE CONTROL SCHEME
We have a new deterministic model for chaotic reversal by C. Gissinger [10] given by:

………. (1)

Where and are the states and are unknown parameters.
The system (1) is chaotic when the parameter values are taken as:
and as shown in figure 1.
Strange Attractor of the New Chaotic Reversal System
-5
0
5
-5
0
4
2
0
-2
5
x
1
3
x
2 x
Figure 1:
The system (1) is taken as master system, and the slave system with the adaptive control scheme
is taken as
………. (2)

Where are the parameters of the slave which needs to be estimated and are
the nonlinear controllers such that the two new chaotic reversal systems are function projective
synchronized in the sense that
35

……… (3)
Where is the scaling function.
From system (1) and (2) we get the error dynamical system which can be written as
……… (4)
Where
In order to stabilize the error variables of system (3) at the origin, we propose the adaptive control
law and the parameter update law for system (3) as follows
…….(5)
And the update rule for the three uncertain parameters are
……….. (6)
Where and
Theorem For the given scaling function , the function projective synchronization between
the master system (1) and the slave system (2) can be achieved if the nonlinear controller (5) and
the update law (6) are adopted.
Proof We construct the following Lyapunov function
Calculating the time derivative of V along the trajectory of error system (4), we have

36

… (8)
+
+
+ [
Where , and .
It is evident that is negative definite and if and only if . By the Lyapunov
stability theory, the function projective synchronization is achieved. This ends the proof.
3. NUMERICAL SIMULATIONS
The numerical simulations to verify the effectiveness of the proposed function projective
synchronization using the adaptive controllers are carried out by the fourth-order Runge-Kutta
method. This method is used to solve the master system (1) and the slave system (2) with time
step size . The initial conditions of the master system are
. The scaling function is chosen as and . The figure
2 shows that the error variables tend to zero with . Figure 3 shows that the
estimated values of the uncertain parameters converge to as
.
300
250
200
150
100
50
0
0 2 4 6 8 10 12 14 16 18 20
Time / s
e
1

37

5
4
3
2
1
0
-1
0 2 4 6 8 10 12 14 16 18 20
Time /s
e
2
10
8
6
4
2
0
0 2 4 6 8 10 12 14 16 18 20
Time /s
e
3
Figure 2: Error dynamics between master system (1) and the slave system (2)
100
0
-100
-200
-300
0 2 4 6 8 10 12 14 16 18 20
Time /s
a
1

38

4
3
2
1
0
-1
0 2 4 6 8 10 12 14 16 18 20
Time /s
b
1
12
10
8
6
4
2
0
0 2 4 6 8 10 12 14 16 18 20
Time /s
c
1
Figure 3: The time evolution of the estimated parameters
4. CONCLUSION
In the present work we have demonstrated the application of function projective synchronization
in synchronizing the new chaotic reversal systems with uncertain parameters. The Lyapunov
stability theory was used to design the adaptive synchronization controllers with associated
parameter update laws to stabilize the error dynamics between the master and the slave chaotic
oscillators. All the theoretical investigations have been verified by numerical simulations to proof
the effectiveness of the scheme.
REFERENCES
[1] Lorenz, E.N. (1963) “Deterministic nonperiodic flow,” J. Atmos. Phys. Vol. 20, pp 131-141.
[2] Rössler, O.E. (1976) “An equation for continuous chaos,” Physics Letters A, Vol. 57, pp 397-398.
[3] Junbiao Guan, (2012 )‘’Function projective synchronization of a class of chaotic systems with
uncertain parameters’’, Hindawi Publishing Corp., Article ID 431752,
[4] L. M. Pecora and T. L. Carroll, (1990) “Synchronization in chaotic systems,” Physical Review
Letters, vol. 64, no. 8, pp. 821–824,.
[5] M. Rosenblum, A. Pikovsky, and J. Kurths, (1996) “Phase synchronization of chaotic oscillators,”
Physical Review Letters, vol. 76, pp. 1804–1807,.
[6] H. Taghvafard and G. H. Erjaee, (2011)“Phase and anti-phase synchronization of fractional order
chaotic systems via active control,” Communications in Nonlinear Science and Numerical
Simulation, vol. 16, no. 10, pp. 4079–4088,.
[7] R. Mainieri and J. Rehacek, (1999)“Projective synchronization in three-dimensional chaotic systems,”
Physical Review Letters, vol. 82, pp. 3042–3045,.

[8] Junbiao Guan, (2010) “Synchronization control of two different chaotic systems with known and
39

unknown parameters,” Chinese Physics Letters, vol. 27, Article ID 020502,.
[9] L. Runzi, (2008) “Adaptive function project synchronization of Rossler hyperchaotic system with
uncertain parameters,” Physics Letters. A, vol. 372, no. 20, pp. 3667–3671,
[10] Gissinger, C. (2012) ‘’ A new deterministic model for chaotic reversals, ’’ Euro. Phy. J. B 85:137, pp
1-12.
Author
Ojoniyi, Olurotimi Seyi is currently on a Ph.D programme in nonlinear dynamics and chaos
at the department of Physics of the University of Agriculture, Abeokuta, Ogun State, Nigeria.
He holds a M.Sc, degree in Physics from the University of Ibadan, Ibadan, Nigeria and is
currently an academic Staff of Physics and Telecommunications department of Tai Solarin
University of Education, Ijagun, Ogun State, Nigeria.

Function projective synchronization

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