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JOURNALS // Trudy Instituta Matematiki i Mekhaniki UrO RAN // Archive

Trudy Inst. Mat. i Mekh. UrO RAN, 2021 Volume 27, Number 2, Pages 108–119 (Mi timm1818)

Asymptotics of a solution to a problem of optimal boundary control with two small cosubordinate parameters. II

A. R. Danilin

Institute of Mathematics and Mechanics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg

Abstract: We consider a problem of optimal boundary control for solutions of an elliptic type equation in a bounded domain with smooth boundary with a small coefficient at the Laplace operator, a small coefficient, cosubordinate with the first, at the boundary condition, and integral constraints on the control:
$$  \left\{  
\begin{array}{ll}  \displaystyle {\mathcal L}_\varepsilon z\mathop{:=}\nolimits - \varepsilon^2 \Delta z + a(x) z = f(x), &  \displaystyle                 x\in \Omega,\ \  z \in H^1(\Omega), \\[3ex]  \displaystyle l_{\varepsilon} z\mathop{:=}\nolimits \varepsilon^\beta \frac{\partial z}{\partial n} = g(x) + u(x), &  x\in\Gamma,  \end{array}
 \right.  $$

$$  J(u) \mathop{:=}\nolimits \|z-z_d\|^2 + \nu^{-1}|||u|||^2 \to \inf, \quad   u \in \mathcal{U},  $$
where $0<\varepsilon\ll 1$, $\beta\geqslant 0$, $\beta\in\mathbb{Q}$$\nu>0,$ $H^1(\Omega)$ is the Sobolev function space, $\partial z/\partial n$ is the derivative of $z$ at the point $x\in\Gamma$ in the direction of the outer (with respect to the domain $\Omega$) normal,
$$  
\begin{array}{c}   \displaystyle  a(\cdot),  f(\cdot), z_d(\cdot)  \in  C^\infty(\overline{\Omega}),  \quad   g(\cdot)\in C^\infty(\Gamma),\quad   \forall\, x\in \overline{\Omega}\quad a(x)\geqslant \alpha^2>0, \\[2ex]   \displaystyle \mathcal{U} = \mathcal{U}_1,\quad \mathcal{U}_r\mathop{:=}\nolimits \{u(\cdot)\in L_2(\Gamma)\colon      |||u||| \leqslant r\}.  \end{array}
 $$
Here $\|\cdot\|$ and $|||\cdot|||$ are the norms in the spaces $L_2(\Omega)$ and $L_2(\Gamma)$, respectively. We find a complete asymptotic expansion of the solution of the problem in powers of the small parameter in the case where $\beta\geqslant 3/2$. In contrast to the previously considered case, the relevance of the constraints on the control depends on $|||g|||$.

Keywords: singular problems, optimal control, boundary value problems for systems of partial differential equations, asymptotic expansions.

UDC: 517.977

MSC: 35C20, 35B25, 76M45, 93C70

Received: 31.01.2021
Revised: 10.02.2021
Accepted: 15.02.2021

DOI: 10.21538/0134-4889-2021-27-2-108-119



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