1.
Introduction
Chemistry, astronomy, population growth, turbulence, weather, linguistics and stock markets are some of the scientific fields that exhibit chaotic phenomena. Chaos is understood through linguistics. In [1], Eleonora and Pietro investigated a linguistic approach to chaos understanding. We translate the complexity of chaotic systems into sounds and music, as with Chua's attractors. They found that there is an interaction between the different levels of chaotic language. Furthermore, some traits of the dynamics of language evolution in human infants are found in the major routes to chaos.
In 1981, Leipnik and Newton [2] studied their concept of the gyroscope for chaotic motion, discovering two strange attractors for rigid bodies' motion. In [3], Wang and Tian named this system the Newton-Leipnik system and studied a chaotic Newton-Leipnik system with two strange attractors. Since Leipnik and Newton's work, many scientists have intensively examined the chaotic dynamics of rigid body motion [4,5,6,7,8,9]. Chaos control is performed by a simple linear controller, and a numerical simulation of the control is provided. In addition, Chen and Lee [4] introduced a novel chaotic system capable of generating dual-role chaos attractors when investigating rigid body motion anti-chaos control. Richter [5] studied the stability and chaos control of Newton-Leipnik systems using static nonlinear feedback laws based on Lyapunov functions. In [6], Long-Jye Sheu et al., investigated the dynamics of the Newton-Leipnik system with fractional order and was studied numerically. The Newton-Leipnik system [3] is described as:
Fractional calculus (FC) allows integration and differentiation of operators in fractional order. FC is considered a popular research topic and has been extensively studied in recent decades [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34]. Samko proposed a fascinating extension of constant-order FC in [35]. Solís-Pérez et al. [36] introduced fractional operators that consider order as a function of time, space or other variables see also [37,38]. In addition, applications of these fractional variable-order operators can be found in [39,40,41,42,43,44,45,46,47,48].
Variable-order fractional differential equations cannot be solved exactly, so developing numerical schemes for solving these equations is crucial. In [36], Solís-Pérez et al. developed a constant-order numerical scheme that combines fractional calculus and Lagrange polynomials. Using this method, they generalized the numerical schemes for simulating variable-order fractional differential operators with power-law, exponential-law and Mittag-Leffler kernels. See also [49,50,51,52,53,54,55,56,57,58,59,60].
The memory and genetic properties of Eq (1.1) can be improved by extending the integer-order Newton-Leipnik model to a variable-order Newton-Leipnik model. In this paper, we apply the novel generalized numerical scheme of Mittag-Leffler kernels to simulate a variable-order fractional Newton-Leipnik system. Numerical methods developed by Atangana-Baleanu and Atangana-Seda for solving fractional Newton-Leipnik systems are presented. Moreover, we use numerical successive approximation methods to solve the proposed model. In order to stabilize the proposed system, fractional Routh-Hurwitz conditions must be applied. When nonlinear control functions are chosen carefully, chaos synchronization of Newton-Leipnik systems has also been demonstrated when fractional-order systems are considered. Furthermore, some examples are given, and our numerical simulations reveal novel attractors. Through simulations, the method's accuracy and efficiency have been demonstrated.
2.
Preliminaries
A very significant role in fractional calculus was introduced by Humbert and Agarwal in 1953. It is a two-parameter Mittag-Leffler function defined as (Gorenflo et al., 1998):
For β=1 we obtain the Mittag-Leffler function in one parameter (Mittag-Leffler, 1903):
According to [45], ABC (Atangana-Baleanu-Caputo) may be derived in fractional derivatives with variable orders g∈C1(0,T),0<T,
In this formula, ABC(κ)=1−κ+η/Γ(κ) is the normalization function, Γ(⋅) is the Euler Gamma function, and Eκ(⋅) is the Mittag-Leffler function.
Theorem 1. [39,40] The time-fractional ABC differential equation:
provides a unique solution
In [39,40], ABC fractional derivative has the fractional-integral associate:
3.
Model properties
3.1. Existence and uniqueness
ABC fractional derivatives of the Newton-Leipnik system are presented here.
Taking the fractional integral operator of ABC and applying it to Eq (3.1), we get
We will assume that f, g and h are nonnegative bounded functions, i.e., ‖f‖≤κ1, ‖g‖≤κ2, ‖h‖≤κ3, where κ1,κ2 and κ3 are some positive constants. Denote
When we apply the ABC fractional integral to system (3.1), we obtain
where the kernels L1(t,f,g,h), L2(t,f,g,h), L3(t,f,g,h) are defined as:
Proposition 1. If
Thus, the kernels L1(t,f,g,h), L2(t,f,g,h), L3(t,f,g,h) satisfy Lipschitz conditions.
Proof. If f2 and f1 are any two functions, then
where ℓ1 is the Lipschitz constant and is defined in Eq (3.3). Similarly, the kernels L2,L3 can be calculated using {g2,g1},{h2,h1}, respectively:
Thus, the Lipschitz conditions are satisfied forL1(t,f,g,h), L2(t,f,g,h), L3(t,f,g,h). Additionally, since 0≤M=max{ℓ1,ℓ2,ℓ3}<1, the kernels are contractions. Equation (3.4) can be used to display state variables as kernels:
We now introduce the following recursive formulas using Eq (3.5):
with
For the recursive formulas, the difference between consecutive terms is
Note that:
As a result, the recursive inequalities:
Therefore
Similarly
□
As a result, a solution of a system (3.1) exists if the following condition is satisfied, if t0>0:
Proposition 2. System (3.1) provides a unique solution if the following conditions are met:
4.
Newton-Leipnik chaos control
Consider the ABC fractional-order Newton-Leipnik system:
Its Jacobian matrix J(E∗) is
where E∗=(f∗,g∗,h∗) is the equilibrium point of the system (4.1). The Jacobian eigenvalues at all equilibrium points indicate that they are all saddle points. All of these eigenvalues have a chaos condition.
Newton-Leipnik controlled fractional-order system is given by:
In addition, K=diag(c1,c2,c3),c1,c2,c3≥0. By selecting the appropriate feedback control gains c1,c2,c3, the controlled system (4.2) approaches the unstable equilibrium point asymptotically. Specifically, we are trying to reduce the trajectory of system (4.1) to one of E0,E1,E2,E3 and E4 which defined in Table 1. A simple feedback gain is K=diag(c1,0.0). At E0=(0,0,0), the characteristic equation of (4.2) is:
By choosing satisfactory feedback control gains c1, c2, c3
It is necessary to apply the fractional Routh-Hurwitz conditions to control chaos in the (4.1) to its equilibrium. The equilibrium point of (4.1) can be achieved by using specific linear controllers, based on Routh-Hurwitz. When the nonlinear control functions are chosen carefully, chaos synchronization of (4.1) has been demonstrated.
4.1. Chaos synchronization
The following example illustrates synchronizing chaos between two Newton-Leipnik systems with unidirectional linear error feedback. This is the drive system:
The response system is provided by:
where the controller u=[ω1ω2ω3]T, with
By subtracting (4.3) from (4.4) in case κ=1, we obtain:
where ef=f1−f2,eg=g1−g2,eh=h1−h2. The matrix form of system (3.1) is as follows:
where
As a result, if the feedback control c1,c2 and c3 gains satisfy the following inequalities:
the synchronization of (4.3) is achieved. Combined Newton-Leipnik systems (4.1) and (4.2) are numerically integrated with parameters c1=280, c2=250,c3=100.
4.2. Nonlinear control of a proposed system
The controllers for the drive and response systems (4.1) and (4.2) are as follows:
As a result, fractional-order error dynamics are characterized by
By using the feedback control gain c1=69.2111 as well as the parameters κ=1.0,κ=0.98, the error system (4.7) is numerically integrated.
5.
Numerical results
The following schemes is taken from [50,51].
5.1. Atangana-Baleanu-Caputo numerical scheme
The fundamental theorem of fractional calculus of (2.1), gives
At tn+1, we have
Two-step Lagrange polynomial interpolation can be used to approximate ζ(η,ϕ(η)):
Equation (5.2) is replaced by Eq (5.1) in order to obtain
which implies that
The following approximation can be obtained by integrating (5.4) and replacing it with (5.3):
The following is the numerical representation of the system (2.1):
5.2. Mittag-Leffler kernel for the Atangana-Seda method
Based on the integration of the equations above, we are able to arrive at the result:
At t=tn+1,
As a result, we have the following:
A Newton polynomial is added to the integrals above to yield the following result:
Therefore, we can express the Newton-Leipnik system numerically as follows:
5.3. Successive approximation method
For a system (3.1) with initial conditions, we use the successive approximation method:
We have
Then
Based on the theorem regarding the product of convolution, we obtain the following three iterations:
Then
5.4. Numerical simulation and discussions
Example 1. [6] We deal with the following chaotic problem:
with the initial conditions.
The numerical simulations of the ABC fractional Newton-Leipnik system (5.5) are presented in Figures 1, 3, 5 and 7 for κ(t)=1, κ(t)=0.98, κ(t)=0.97+0.03×tanh(t/10), κ(t)=0.97−0.03×sin(t/10), respectively. The numerical simulations of the AS fractional Newton-Leipnik system (5.5) are presented in Figures 9, 11, 13 and 15 for κ(t)=1, κ(t)=0.98, κ(t)=0.97+0.03×tanh(t/10), κ(t)=0.97−0.03×sin(t/10), respectively.
Example 2. We deal with the following chaotic problem:
with the initial conditions
The numerical simulations of the ABC of the controlled fractional order Newton-Leipnik system (5.6) are presented in Figures 2, 4, 6 and 8 for κ(t)=1, κ(t)=0.98, κ(t)=0.97+0.03×tanh(t/10), κ(t)=0.97−0.03×sin(t/10), respectively. The numerical simulations of the AS of the controlled fractional order Newton-Leipnik system (5.6) are presented in Figures 10, 12, 14 and 16 for κ(t)=1, κ(t)=0.98, κ(t)=0.97+0.03×tanh(t/10), κ(t)=0.97−0.03×sin(t/10), respectively.
6.
Conclusions
Fractional differential operators have the ability to accurately replicate and reveal some chaos. However, because of their non-linearity, their analytical solutions are difficult to obtain and, in some circumstances, impossible to achieve due to their non-linearity. Researchers rely on numerical methods to understand physical behavior. We present a numerical method for chaotic problems. Using differential and integral operators in the sense of Atangana-Baleanu-Caputo, we investigated the Newton-Leipnik system of mathematical equations able to capture chaotic behavior. Solutions are obtained for the fractional-order Newton-Leipnik model using a fractional operator with a non-singular kernel. Uniqueness and boundedness for solutions are proved through the fixed point theory. Due to the high non-linearity of our problem, we used a suitable numerical scheme to solve this system of equations numerically. The presented scheme is applicable to many other systems, such as those in [36,37,38,39,40,41,42,43,44,45,46,47,48]. In future work, the existence and uniqueness of solutions reported for general component differential equations will be extended to multidimensional problems.
Use of AI tools declaration
The authors declare they have not used Artificial Intelligence (AI) tools in the creation of this article.
Acknowledgment
The first author would like to thank the Deanship of Scientific Research, Qassim University, Saudi Arabia for funding the publication of this project.
Conflict of interest
The authors declare that they have no conflict of interest.