Ultralow parasitic eigenvalues for oscillation problem of a guided elastic flying vehicle that contains integrating section in a feedback loop

Integration sections are frequently inserted in feedback loops of flight control systems. They usually help to increase the accuracy of flight control. But at the same time such an engineering solution can change significantly dynamic properties of the guided elastic structure. The oscillation system becomes unconservative. The number of degrees of freedom continues to be the same but the quantity of modes increases. Ultralow parasitic eigenvalues appear. They are named ultralow ones because they tend to zero together with the feedback loop amplification factor. They are named parasitic ones because they interact with the main eigenvalues. The interaction of the ultralow parasitic oscillation mode and the main oscillation mode can cause dynamic instability. It is shown in this issue that violations of the principle oscillation theorems (oscillation properties) take place for the parasitic oscillation modes [S.V. Arinchev, 2002].