A new calculation method for Bode and Nyquist diagrams of rotor startup or shutdown and its application

In order to prepare well for drawing Bode and Nyquist diagrams of vibration signals collected from rotor startup or shutdown process, a new Hilbert transform based calculation method is proposed. Experiment results show that the proposed method can smooth Bode and Nyquist diagrams, has more accuracy in amplitude and phase calculation, and also can not be affected by harmonic components of rotor vibration. Verifying tests on dynamic balancing experiment reveal that vibration values of rotor greatly reduce after balancing by using the information extracted form Bode and Nyquist diagrams.