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Stability of a nonlinear non-autonomous fractional order systems with different delays and non-local conditions
Advances in Difference Equations volume 2011, Article number: 47 (2011)
Abstract
In this paper, we establish sufficient conditions for the existence of a unique solution for a class of nonlinear non-autonomous system of Riemann-Liouville fractional differential systems with different constant delays and non-local condition is. The stability of the solution will be proved. As an application, we also give some examples to demonstrate our results.
1 Introduction
Here we consider the nonlinear non-local problem of the form
where D α denotes the Riemann-Liouville fractional derivative of order α ∈ (0, 1), x(t) = (x 1(t), x 2(t), ..., x n (t))', where ' denote the transpose of the matrix, and f i , g i : [0, T] × R n → R are continuous functions, Φ(t) = (ϕ i (t)) n × 1are given matrix and O is the zero matrix, r j ≥ 0, j = 1, 2, ..., n, are constant delays.
Recently, much attention has been paid to the existence of solution for fractional differential equations because they have applications in various fields of science and engineering. We can describe many physical and chemical processes, biological systems, etc., by fractional differential equations (see [1–9] and references therein).
In this work, we discuss the existence, uniqueness and uniform of the solution of stability non-local problem (1)-(3). Furthermore, as an application, we give some examples to demonstrate our results.
For the earlier work we mention: De la Sen [10] investigated the non-negative solution and the stability and asymptotic properties of the solution of fractional differential dynamic systems involving delayed dynamics with point delays.
El-Sayed [11] proved the existence and uniqueness of the solution u(t) of the problem
by the method of steps, where A, B, C are bounded linear operators defined on a Banach space X.
El-Sayed et al. [12] proved the existence of a unique uniformly stable solution of the non-local problem
Sabatier et al. [6] delt with Linear Matrix Inequality (LMI) stability conditions for fractional order systems, under commensurate order hypothesis.
Abd El-Salam and El-Sayed [13] proved the existence of a unique uniformly stable solution for the non-autonomous system
where is the Caputo fractional derivatives (see [5–7, 14]), A(t) and f(t) are continuous matrices.
Bonnet et al. [15] analyzed several properties linked to the robust control of fractional differential systems with delays. They delt with the BIBO stability of both retarded and neutral fractional delay systems. Zhang [16] established the existence of a unique solution for the delay fractional differential equation
by the method of steps, where A 0, A 1 are constant matrices and studied the finite time stability for it.
2 Preliminaries
Let L 1[a, b] be the space of Lebesgue integrable functions on the interval [a, b], 0 ≤ a < b < ∞ with the norm .
Definition 1 The fractional (arbitrary) order integral of the function f(t) ∈ L 1[a, b] of order α ∈ R + is defined by (see [5–7, 14, 17])
where Γ (.) is the gamma function.
Definition 2 The Caputo fractional (arbitrary) order derivatives of order α, n < α < n + 1, of the function f(t) is defined by (see [5–7, 14]),
Definition 3 The Riemann-liouville fractional (arbitrary) order derivatives of order α, n < α < n + 1 of the function f (t) is defined by (see [5–7, 14, 17])
The following theorem on the properties of fractional order integration and differentiation can be easily proved.
Theorem 1 Let α, β ∈ R + . Then we have
-
(i)
, and if f(t) ∈ L 1 then .
-
(ii)
, n = 1,2,3,... uniformly.
-
(iii)
, α ∈ (0,1), f (t) is absolutely continuous.
-
(iv)
, α ∈ (0,1), f (t) is absolutely continuous.
3 Existence and uniqueness
Let X = (C n (I), || . ||1), where C n (I) is the class of all continuous column n-vectors function. For x ∈ C n [0, T], the norm is defined by , where N > 0.
Theorem 2 Let f i , g i : [0, T] × R n → R be continuous functions and satisfy the Lipschitz conditions
and , .
Then there exists a unique solution × ∈ X of the problem (1)-(3).
Proof Let t ∈ (0, T). Then equation (1) can be written as
Integrating both sides, we obtain
From (3), we get
Operating by I α on both sides, we obtain
Differentiating both side is, we get
Now let F : X → X, defined by
then
and
and
Now choose N large enough such that , so the map F : X → X is a contraction and hence, there exists a unique column vector x ∈ X which is the solution of the integral equation (4).
Now we complete the proof by proving the equivalence between the integral equation (4) and the non-local problem (1)-(3). Indeed:
Since x ∈ C n and I 1-α x(t) ∈ C n (I), and f i , g i ∈ C(I) then I 1-α f i (t), I 1-α g i (t) ∈ C(I). Operating by I 1-α on both sides of (4), we get
Differentiating both sides, we obtain
which implies that
which completes the proof of the equivalence between (4) and (1).
Now we prove that . Since f i (t, x 1(t), ..., x n (t)), g i (t, x 1(t - r 1), ..., x n (t - r n )) are continuous on [0, T] then there exist constants l i , L i , m i , M i such that l i ≤ f i (t, x 1(t), ..., x n (t)) ≤ L i and m i ≤ g i (t, x 1(t - r 1) ), ..., x n (t - r n )) ≤ M i , and we have
which implies
and
Similarly, we can prove
Then from (4),. Also from (2), we have .
Now for t ∈ (-∞, T], T < ∞, the continuous solution x(t) ∈ (-∞, T] of the problem (1)-(3) takes the form
4 Stability
In this section we study the stability of the solution of the non-local problem (1)-(3)
Definition 5 The solution of the non-autonomous linear system (1) is stable if for any ε > 0, there exists δ > 0 such that for any two solutions x(t) = (x 1(t), x 2(t), ..., x n (t))' and with the initial conditions (2)-(3) and respectively, one has , then for all t ≥ 0.
Theorem 3 The solution of the problem (1)-(3) is uniformly stable.
Proof Let x(t) and be two solutions of the system (1) under conditions (2)-(3) and , respectively. Then for t > 0, we have from (4)
and
Then we have,
Therefore, for δ > 0 s.t., we can find s.t. which proves that the solution x(t) is uniformly stable.
5 Applications
Example 1 Consider the problem
where A(t) = (a ij (t)) n×n and are given continuous matrix, then the problem has a unique uniformly stable solution x ∈ X on (-∞, T], T < ∞
Example 2 Consider the problem
where B(t) = (b ij (t)) n×n , and are given continuous matrices, then the problem has a unique uniformly stable solution x ∈ X on (-∞, T], T < ∞
Example 3 Consider the problem (see [12])
where A(t) = (a ij (t)) n×n B(t) = (b ij (t)) n×n , and H(t) = (h i (t)) n×1are given continuous matrices, then the problem has a unique uniformly stable solution x ∈ X on (-∞, T], T < ∞.
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El-Sayed, A., Gaafar, F. Stability of a nonlinear non-autonomous fractional order systems with different delays and non-local conditions. Adv Differ Equ 2011, 47 (2011). https://doi.org/10.1186/1687-1847-2011-47
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DOI: https://doi.org/10.1186/1687-1847-2011-47