Updating the model of a rotor with surface mounted permanent magnets in an active magnetic bearing rotor system

In this publication, the finite element method (FEM) model of a rotor of permanent magnet (PM) machine with surface mounted permanent magnets is updated. Typically rotors are modeled with FEM, but the model is still only an approximation of the real rotor. The rotor is constructed from number of different elements and have a complex geometry. Electrical machine part might have slits, surface mounted or embedded permanent magnets. Elements are often connected with shrink fits and this leads to the properties discrepancy compared to the elements described with Timoshenko beam theory. In the work, specific elements are selected as uncertain based on engineering experience and the elasticity values of these elements is updated. Experimental data is obtained with AMB system identification and then the frequency difference in the resonance and anti-resonance frequencies between the experimental data and FEM-model is minimized. When the frequency difference has been minimized, the updated FEM-model corresponds better to the experimental data. The updated model is utilized for controller synthesis procedure to improve performance of the control system. An AMB PM machine with surface mounted permanent magnets was used to test the rotor model update procedure. The procedure allowed to fit the model to the experimental data with accuracy of 56.57 %.