Abstract: The stable problem of rotor system, seen in many fields, has been cared for more. Nowadays the reasons of most losing stability are caused by nonlinear behaviors. This presents higher requirements to the designing of motor system: considering nonlinear elements, avoiding the unstable parameter points or regions where nonlinear phenomena will be presented. If a family of time series of the unknown nonlinear dynamical system can only be got (may be polluted by noise), how to identify the change of motive properties at different parameters? In this paper, through the study of Jeffcott rotor system, the result that using the figures between the fractional dimension of time-serial and parameter can be gained, and the critical bifurcated parameters of bearing-rotor dynamical system can be identified.

Key words: fluid film bearing-rotor system, bifurcation, fractional dimension