The Study Of The Auxiliary Electromagnetic Support Used For High Rotating Speed Machinery

The excess vibration is always an engineering problem of the high rotating speed machinery. In order to keep the safe operation of this kind of machinery, the active as well as passive vibration control method is applied. Among the factors that cause the vibration, the unbalance and the misalignment are the two main ones. For the vibration caused by the unbalance, many works have been done. The elastic-damp-support theory and balancing method/theory are proposed. And there are many successful engineering cases. For the misalignment, the current research still stays at the dynamics study and the status monitor level.From the viewpoint of theory, the active magnetic bearing (AMB) may be regarded as an elastic-damp-support to eliminate the vibration not only caused by the unbalance but also by the misalignment. From the articles at hand, the research of AMB is confined only within the realm of reliability, controlling method, active vibration reducing and structural simplification. On the contrary, the on-line elimination of misalignment has little been touched.On summarizing the vibration reducing techniques, the main works of this thesis is listed as follows:1. Proposed a new kind of support structure-auxiliary electromagnetic support based on the elastic-damp-support theory and the AMB principle. The auxiliary electromagnetic support is consisted of two major parts: an active magnetic actuator (AMA) and the main bearing. The main bearing provides the main stiffness and the active magnetic bearing provides additional stiffness and damping. The AMA is installed upon the main bearing. The principles of auxiliary electromagnetic support are presented in detail. And a design criterion is summarized for parameters like structure, stiffness and so on.2. Researched the passive vibration reduction capacity of auxiliary electromagnetic support. According to different mechanism, research on passive vibration reduction with constant voltage and constant current is explicitly analyzed. And the two kindsVIIof vibration reducing models are constructed respectively. This kind of structure is applied to a four DOF(degree of freedom) experimental rotor. The result shows that these two kind of passive vibration reduction are successful. The difference between the two types of passive vibration reductions is deduced. The AMA with constant voltage source exhibits damping character, while with constant current source it provides only a negative stiffness that lowers the critical speed of the rotor system.3. Analyzed the influence of the P(proportional coefficient) and Td(differential time coefficient) within the real-time controlling block upon the additional stiffness and damp provided by the AMA. Design principles, which should be taken care of and obeyed, are proposed for designing auxiliary electromagnetic support controllers. With the guidance of the aforementioned principles, the variable stiffness and variable damping control methods have been designed and applied for the auxiliary electromagnetic support system. A good vibration reduction result was observed.4. Stepped into a preliminary research work of on-line misalignment identification and reduction with auxiliary electromagnetic support utilizing the structural characteristics of the auxiliary electromagnetic support. Two kind of controlling strategies are introduced: auto-optimizing control and feed-forward-learning control. Experiments were done for each controlling strategy and a better correcting result was achieved.5. Studied the influence of iron eccentricity upon the auxiliary electromagnetic support system and the system stability. Analyzed the transient response of the iron when AMA shifts the rotor. And finally gave some special advises when using auxiliary electromagnetic support.