Аннотация:In this paper, the eigenvalue problem for self-adjoint linear Hamiltonian systems with nonlinear dependence on the spectral parameter and parameter dependent boundary conditions is considered. A Newton-type iterative solution method is presented. The method has a quadratic convergence and provides a two-sided estimate of the eigenvalue. With the help of this technique the boundary control problem for a non-uniform string with a L2-norm minimization condition on a finite time interval is studied. Here, the control acts on the left end and a point mass is attached to the right one. The linear-quadratic regulator problem is considered, and an optimal feedback control law for the first mode of the hybrid system is designed.