In this work, the movement of the rotor center when changing the excitation frequency has been analyzed. The rotor model is a nonlinear wave-discus system. The numerical recorders of the movement are the portraits in the $x-\dot x$, $y-\dot y$, $x-y$ planes, the time diagrams $x-t$, $y-t$, $A-t$ and the Poincare map. The frequency increase changes the character of the movement: from the usual backward movement on the large orbit through the chaotic movement to the usual backward movement on the small orbit. The chaotic motion is the effect of the external constraining force on the non-linear rotor.