Approximation method for placing the roots of an algebraic equation within a prescribed region

For the stability of a control system, it is desirable that the roots of the characteristic equation, including parameters in the coefficients, exist in a prescribed region. The approximation method discussed places the roots of the characteristic equation within a prescribed region. The simultaneous equation is obtained from the roots and coefficients of the characteristic equation. By iterating the simultaneous equation, the roots are shifted to a prescribed region.