Implementation of a Slotted High-Speed Bearingless Slice Motor and Analysis of Tilt Vibration Damping Concepts

A bearingless motor is a device which is capable of creating both bearing forces and rotational torque in a common unit. The omission of mechanical bearings features the advantage of contact-free operation. The rotor of a bearingless slice motor is disk shaped, which means that its length is small compared to its diameter. This leads to reduced system complexity because the axial position and tilting can be passively stabilized by reluctance forces. Unfortunately, axial and tilting vibrations due to disturbances or resonance effects are typically only very poorly dampened. Especially in high speed drives, gyroscopic movements of the rotor due to tilt deflections may cause touch-down. To overcome this problem, an electrodynamic tilt stabilization coil can be integrated into the stator. In the first part of this master thesis, the control model of the bearingless slice motor is discussed. The principal concepts of force and torque generation are investigated, followed by a detailed description of the decoupling strategy for currents to generate either bearing forces or motor torque. Under consideration of a mathematical model for the motors dynamics a control scheme for radial position and rotational speed is developed. Further, a mathematical model which describes the tilt movement of the rotor is presented. Three different strategies to increase damping of tilt vibrations are mathematically modeled and analyzed: additional tilt damping by field-flux modulation, by radial rotor position displacement and by an electrodynamic tilt stabilization coil. After that, the assembly of a slotted bearingless high speed motor prototype, which was designed in a previous work, is described. After winding the stator coils and molding the whole stator in epoxy resin, the motor is connected to the power electronics and commissioned. The angle and position sensors are implemented and adjusted properly. A control model is implemented in X2C and the controller parameters are optimized. Finally, measurements on a test bench are performed to determine passive and active motor parameters. The single phase characteristics, current-force- and current-torque-factor as well as passive stiffness values and drive efficiency are evaluated.submitted by Bianca KlammerUniversität Linz, Masterarbeit, 2019(VLID)386657