Research On Dynamic Characteristic Of Magnetic Suspension Rotor

As one of the supporting components, which can be controlled actively, active magnetic bearing (AMB) has been widely used in many machines with high rotation speed in all kinds of field because of its high performances beyond other traditional bearings. The basic research of the AMB has been achieved, but there are still many problems to be solved before putting them into industrial applications. One of them is bearing-rotor system dynamics and its stability. This paper will deal with these problems, and mainly focus on the critical speeds of the high speed rotating machinery supported AMB.First, some useful methods and theories in traditional bearing-rotor dynamics are summarized as the basis of study on dynamics of active magnetic bearing-rotor system. Next, basic on the analysis and calculation formulas of stiffness and dampness of one-degree-of-freedom, calculation formulas of stiffness and dampness of five-degree-of-freedom is given. Secondly, the mathematical model and mechanic models have been established using traditional dynamics combined with the characteristics of AMB. Then, by considering the characteristics of AMB and adapting the traditional Riccati transfer matrix method to active magnetic suspension rotor system, a method is established for calculating and analyzing dynamics. Finally, an actual active magnetic bearing-rotor system is calculated and validated by using above method and experiment.Some conclusions are formed by analyzing the results of the calculations: Like traditional bearings, the dynamic characteristic coefficient can be described by eight equivalent stiffness and dampness coefficients. The stiffness and dampness coefficients relate with not only parameters of bearing itself but those of controller as well and thus stiffness and dampness coefficients can be adjusted by changing those parameters. Low critical speed of magnetic suspension rotor system is mainly determined by bearing structure and parameters of controller on AMB, while high critical speed is mainly affected by rotor structure.