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ABSTRACT
In this paper, authors studied the boundary controllability results for neutral impulsive integrodifferential evolution systems with time-varying delays in Banach spaces. The sufficient conditions of the boundary controllability are proved under the evolution operator. The results are obtained by using the semigroup theory and the Schaefer fixed point theorems.
1. Introduction
The theory of differential equations in abstract spaces is a fascinating field with important applications to a number of areas of analysis and other branches of mathematics. Depending on the nature of the problems, these equations may take various forms such as ordinary differential equations. Using the method of semigroups, various solutions of nonlinear and semilinear evolution equations have been discussed by Pazy [Citation1]. Delay differential equations are similar to ordinary differential equation, but their evolution involves past values of the state variable. Time delay is inherently the character of most dynamical systems to some extent. Time delays are frequently encountered in various engineering systems such as aircraft, long transmission lines in pneumatic models and chemical or process control systems. These delays may be the source of instability and lead to serious deterioration in the performance of closed-loop systems. The problem of controllability of nonlinear systems and integrodifferential systems including delay systems has been studied by many researchers [Citation2–4] and the theory of neutral differential equations has been studied by the authors Radhakrishnan and Balachandran [Citation5].
The concept of control can be described as the process of influencing the behaviour of a dynamical system so as to achieve a desired goal. Roughly speaking, controllability generally means that it is possible to steer a dynamical system from an arbitrary initial state to an arbitrary final state using the set of admissible controls. The complexity of modern systems, inaccuracies in output measurements and uncertainties about the system dynamics often make this problem extremely hard to solve. Controllability of linear and nonlinear systems represented by ordinary differential equations in finite-dimensional spaces has been extensively investigated. Since there are many examples where time delay and spatial diffusion enter the control systems, several authors have extended the concept of controllability to infinite-dimensional systems in Banach spaces [Citation6].
The fast scientific development in the foundations and micro-world of biology has led to a reconsideration of nature and some characteristics of life. In fact, scientists agree that its continuous nature in enriched by discretely arising discontinuities and the latter ones are also called jumps or impulses. The dynamics of many evolving processes are subject to abrupt changes, such as shocks, harvesting and natural disasters. These phenomena involve short-term perturbations from continuous and smooth dynamics, whose duration is negligible in comparison with the duration of an entire evolution. For more details on this theory and on its applications, we refer to the monographs of Lakshmikantham et al. [Citation7], and Samoilenko and Perestyuk [Citation8] for the case of ordinary impulsive systems and [Citation9] for partial differential equations with impulsive systems. Similarly in [Citation10], the authors discussed the abstract neutral differential equation with time-varying delay by using the Schaefer fixed point theorem.
The study on the distributed control systems in which the control is exercised through the boundary as distinct from systems controlled in the interior has emerged as one of the most important fields of modern research. Many partial integrodifferential equations with boundary control occur frequently in various physical applications like evolution of population, modelling of thermoelastic plates and damped wave equations. These types of physical models can be reformulated mathematically into an abstract smooth function. Several authors [Citation11,Citation12] have developed many abstract settings to describe the boundary control systems in which the control must be taken in sufficiently smooth functions for the existence of regular solutions to state space system. A semigroup approach to boundary input problems for linear differential equations was developed by Fattorini [Citation13] and Washburn [Citation14]. In [Citation15] Barbu discussed a class of boundary-distributed linear control systems in Banach Spaces. The problem of boundary controllability of integrodifferential systems and delay integrodifferential systems in Banach spaces has been investigated by Balachandran and Anandhi [Citation16,Citation17].
The purpose of this paper is to establish the set sufficient conditions for the boundary controllability of neutral impulsive integrodifferential evolution systems with time-varying delays by using the semigroup theory and fixed point theorem.
2. Preliminaries
Let and
be a pair of real Banach spaces with the norms
and
, respectively. Let α be linear, closed and densely defined operator with
and
and let θ be a linear operator with
and
a Banach space.
Throughout this paper, is a Banach space,
is a family of closed linear operators defined on a common domain
which is dense in
and we assume that the linear non-autonomous system
(1)
(1) has associated evolution family of operators
. In the next definition,
is a space of bounded linear operator from
into
endowed with the uniform convergence topology.
Definition 2.1
[Citation1] A family of operators is called a evolution family of bounded linear operators for (Equation1
(1)
(1) ) if the following properties hold:
and
, for every
and all
.
For each
the function for
is continuous and
for every
For
the function
for
is differentiable with
for
To accommodate the impulsive condition in the system, it is convenient to introduce some additional concepts and notations.
Let and define the following spaces:Let
=
is a function from
into
such that
is continuous at
and left continuous at
and the right limit
exists, for
. Similarly as in [Citation18], we see that
is a Banach space with the norm
To prove the boundary controllability results we need the following hypotheses:
and the restriction of θ to
is continuous relative to graph norm of
.
generates a family of evolution operators
when
of
semigroup on
and there exists a constant M>0 such that
There exists a linear continuous operator
such that
,
, for all
Also
is continuously differentiable and
for all
, where C is a constant.
For all
and
Moreover, there exists a positive function
such that
, a.e. for
and choose a constant P>0 such that
is continuously differentiable and
and for each
the function
is integrable.
Consider the first-order boundary control neutral impulsive integrodifferential evolution system of the form
(2)
(2) where the state variable
takes values in the Banach space
with norm
and the control function
is given in
, a Banach space of admissible control functions
is a linear continuous operator and the nonlinear operators and
. Here
closed operators on
with dense domain
which is independent of
The delays
are given appropriate functions;
and
represent the right and left limits of
at
for
Let be the solution of (Equation2
(2)
(2) ). Then, we can define a function
and, from our assumption, we see that
. Hence, (Equation2
(2)
(2) ) can be written in terms of A and B as
If u is a continuously differentiable on
then z can be defined as a mild solution to the Cauchy problem
and the solution of (Equation2
(2)
(2) ) is given by
(3)
(3)
Definition 2.2
A solution is said to be a mild solution of (Equation2
(2)
(2) ) if
; the restriction of
to the interval
is continuous and, for each
the function
is integrable and the following integral equation:
(4)
(4) Thus, (Equation4
(4)
(4) ) is well defined and it is called mild of solution of the system (Equation2
(2)
(2) ).
Definition 2.3
The system (Equation2(2)
(2) ) is said to be controllable on the interval J if for every
there exists a control
such that the solution
of (Equation2
(2)
(2) ) satisfies
and
Theorem 2.4
For arbitrary define the control
(5)
(5) transfers the initial state
to
Proof.
From (H1) and substituting this control in Equation (Equation4
(4)
(4) ) at t=b, we have
and
Let for some
To study the boundary controllability problem, we assume the following hypotheses:
The linear operator
defined by
has an inverse operator
which takes values in
and there exists a positive constant K such that
.
There exists a positive constant
and, for each
there is a compact set
such that
,
for every
and all
and there exist positive constants
such that
The function
is continuous differentiable function and there exist constants
such that for all
we have
and constants
such that
for all
and
The function
is continuous and there exist a constant
and
such that for all
and
we have
The function
is continuous and there exist constants
and
such that for all
we have
There exists a constant q>0 such that for all
where
Let
and where
be such that
3. Controllability result
Theorem 3.1
If the hypotheses (i)–(v) and (H1)–(H9) are satisfied, then the system (Equation2(2)
(2) ) is controllable on J.
Proof.
Let using the hypotheses (H1), for an arbitrary function
and the control
from
Equation (Equation5
(5)
(5) ).
We shall show that when using the control the operator
defined by
(6)
(6) has a fixed point. This fixed point is then a solution of the control problem (Equation2
(2)
(2) ). Clearly
, which means that the control u steers the system (Equation2
(2)
(2) ) from the initial stage
in the time b provided we can obtain a fixed point of the operator Γ.
First we show that Γ maps into itself. From the assumptions we have
Thus, Γ maps
into itself. Now
we have
Therefore, Γ is a contraction mapping and hence there exists a unique fixed point
such that
Any fixed point of Γ is a mild solution of (Equation2
(2)
(2) ) which satisfies
Thus, the system (Equation2
(2)
(2) ) is controllable on J.
4. Controllability via Schaefer fixed point theorem
In this section, we investigate a different set of sufficient conditions for the boundary controllability of the system (Equation2(2)
(2) ) by suitably adopting the technique of [Citation19].
We need the following fixed point theorem due to Schaefer [Citation20]
Theorem 4.1
Schaefer's theorem
Let Z be a normed linear space. Let be a completely continuous operator, that is, it is continuous and the image of any bounded set is contained in a compact set and let
Then, either is unbounded or F has a fixed point.
Let be the infinitesimal generator of a bounded analytic semigroup
with bounded inverse
on the Banach space
. The operator
can be defined for
as the inverse of the bounded linear operator
and
is a closed linear invertible operator with domain
dense in
For more results of fractional powers of operators one can refer [Citation1].
Furthermore, we consider the following assumptions:
generates a family of evolution operators
when
of analytic semigroups on
and there exists a constant M>0 such that
and for any
there exists a positive constant Q>0 such that
(refer [Citation1] for fractional powers of operators
For each
the function
is continuous and for each
the function
is strongly measurable.
For each positive integer k, there exists
such that
There exists an integer function
such that
For each
the function
is continuous and for each
the function
is strongly measurable.
For each positive integer d, there exists
such that
There exists an integrable function
such that
The function
is completely continuous and for any bounded set
in
, the set
is equicontinuous in
.
There exists
and a constant
such that
The function
satisfies
where
Theorem 4.2
If the hypotheses (i)–(v), (H1) and (H10)–(H14) are satisfied then the system (Equation2(2)
(2) ) is controllable on J.
Proof.
Let the Banach space with the norm
Now define the operator by
(7)
(7) We shall show that when using the control
, the operator Ψ has a fixed point
. This fixed point is the mild solution of the system (Equation2
(2)
(2) ) implying that the system is controllable.
We shall now prove that the operator Ψ is a completely continuous operator. Set
Clearly
is a non-empty, bounded, convex and closed set in
.
Lemma 4.3
The operator defined by (Equation7
(7)
(7) ), is compact.
Proof.
We first show that Ψ maps into an equicontinuous family. Let
. In view of (H10)–(H13), we obtain
Since is continuous and
are in the compact set
for all
and all
the functions
for
are equicontinuous. We see that
tends to zero independent of
as
Thus, Ψ maps
into an equicontinuous family of functions.
Next we show that is compact. Since we have shown
is equicontinuous, by Arzela Ascoli Theorem it suffices to show that Ψ maps
into precompact set in
Let
be fixed and ε be a real number satisfying
For
we define
Now, by the assumption (H2) the set
is relatively compact in
for every
. Moreover, for every
, we have
Therefore,
Since, there are precompact sets arbitrarily close to the set . Thus, the set precompact in
It remains to show that
is continuous. Let
with
in
Then, there is an integer q such that
for all n and
so
By (H11) and (H13),
for each
and since
and also h is completely continuous,
we have by the dominated convergence theorem:
Thus, Ψ is continuous. This completes the proof.
In order to study the controllability using the Schaefer fixed point theorem, we obtain a priori bounds for the integral equation
(8)
(8) where
be a mild solution of
Lemma 4.4
For the system there is a priori bound
such that
depending only on b and the functions
Proof.
From the system (8), (i)–(v) and (H1)–(H9), we have
Let us take the right side of the above inequality as
Then, we have
. Then,
This implies
This inequality implies that there exists a constant such that
and hence we have
where
depends only on b and the functions
and
Therefore it follows from the Schaefer fixed-point theorem that the operator Ψ has a fixed point . Hence, the system (Equation2
(2)
(2) ) is controllable on J.
5. Example
Consider the following boundary control integrodifferential evolution system:
(9)
(9)
(10)
(10)
(11)
(11)
(12)
(12)
(13)
(13) where
is continuous on
and the constant
is small. Let us take
endowed with the usual norm
Put
Define the operators by
In particular, set
Let
Then, we have
Hence, the condition (H5) holds with
Let
Then, we have
Hence, the condition (H6) holds with
Let
Then, we have
Hence, the condition (H4) holds with
Let
Then, we have
Hence, the condition (H3) holds with
Assume that the linear operator
from
into
defined by
induces an invertible operator
on
.
Choose K=1 in such a way that ,where
which is satisfied for some
All the remaining conditions of Theorem (3.1) are satisfied. Hence, the system (Equation9
(9)
(9) )–(Equation13
(13)
(13) ) is controllable on J.
6. Conclusion
To summarize this, authors investigated the boundary controllability results for neutral impulsive integrodifferential evolution systems with time-varying delay in Banach spaces by semigroup theory and the evolution operator. Also proved that the existence and uniqueness of first-order impulsive integrodifferential evolution system by using -semigroup and the Banach contraction principle and thereby shown that the governing system is controllable. Furthermore, based on Schaefer's fixed point theorem, sufficient conditions of controllability for the given system have been obtained by using analytic semigroup. Finally provide an example to illustrate the theory.
7. Future research
Current investigation of the neutral impulsive integrodifferential evolution systems with time-varying delays gives an analytical result only. In future, this work will be implemented to find the numerical solutions also. Moreover, recently fractional differential equations are increasingly used for many mathematical models in science and engineering. Fractional differential equations have attracted considerable interest because of their ability to model complex phenomena. It is also serve as an excellent tool for the description of hereditary properties of various materials and processes. In fact, fractional differential equations are considered as an alternative model to non-linear differential equation. So the current work extended under fractional differential equations too.
Acknowledgements
The authors are grateful to an anonymous referee for valuable comments and suggestions, which helped to improve the quality of the paper.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
B. Radhakrishnan http://orcid.org/0000-0002-0451-5525
P. Chandru http://orcid.org/0000-0002-2652-1723
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