Simulation of Internal Damping in a Rotating System Supported by Magnetic Bearings
TUFTS UNIV MEDFORD MA
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A rotor with internal damping is a complex dynamic system. An accurate model is required to design and test controllers for supercritical operation. This thesis developed and validated a model for this purpose. An existing rotordynamic Finite Element Method FEM model and magnetic bearing simulation, developed by Draper Laboratory, were first compared to actual rotor test data. Correlation of predicted and actual parameters such as critical speeds, rigid body modes, and rotor displacements was used to validate the Draper model and simulation. Once this correlation was established, both the model and simulation were modified to include the destabilizing effects of internal damping. Using these improved predictive tools, several Proportional Integral and Derivative PID controllers were designed and implemented in an effort to stabilize a rotor system with internal damping. The PIE controllers were effective in stabilizing the rotor systems at sub-critical speeds. However, the model developed during this thesis showed that these controllers were unable to counteract the destabilizing effects of internal damping during supercritical operation. This improved rotordynamic model and magnetic bearing simulation is now available to test more complex controller designs in the supercritical regime.