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