Smoothing algorithm is exploited to remove the errors of multiple frequency point, half frequency point and random point, and realize pitch curve smoothing.

The analysis results also indicate rub-impact faults induced by oil-film instability can produce some low-frequency components with small amplitude and oil whip can produce half frequency component;

It is posed that angular air-hammer self-excited vibration and half frequency wobble self-excited vibration are two reasons for resulting angular wobble self-excited vibration for gas film face seals.