Browsing by Subject "Magnetic levitation"
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Item Magnetically levitated XY-THETA motion stage for X-ray microscopy applications(2022-08-21) Fahmy, Abdel; Zhou, Lei, Ph. D.Precision motion systems with micro/nanometers accuracy are used in a wide range of applications such as semiconductor metrology inspection equipment and photo lithography scanners, precision machine tools and microscopes. The demand for precision motion systems that offer higher precision positioning performance and faster motion acceleration in more degrees-of-freedom (DOFs) and can offer a compact design necessitates more sophisticated precision motion systems. In this thesis, we present the modeling, design, prototyping and experimental evaluation for a magnetically levitated positioning stage with a novel electromagnetic design that uses the concept of a bearing-less motor. The developed stage is to be used for microscope applications, the stage can move in 5-DOFs and provide approximately 12mm range of motion in the X-Y-DOFs and full 360 degrees of rotation around the vertical axis, we also present how this stage can be upgraded to provide motion in all 6-DOFs with the integration of a Voice Coil Actuator (VCL). The prototype stage has been successfully levitated and the position control loop experimentally demonstrated a bandwidth of 32 Hz. These results show that the proposed stage is able to meet the needed requirements for precision stages of microscope applications that offer high speed long range scanning and have a compact design. The initial results show promise that with an upgraded sensing system and further tuning of the controller, the proposed stage can offer nanometer positioning accuracy and longer range of motion.Item Self-sensing hysteresis-type bearingless motor(2022-05-06) Homiller, Laura; Zhou, Lei, Ph. D.; Longoria, RaulThis thesis presents the design, implementation, control, and experimental evaluation of a self-sensing hysteresis-type bearingless motor (SSBM). Bearingless motors are well-suited to high-speed applications due to their frictionless operation, but the magnetic levitation of the rotor is unstable without airgap sensors. Eliminating these sensors decreases system cost and volume while increasing system robustness. This work presents the design for a hysteresis-type bearingless motor that operates without the use of airgap sensors. Bearingless motors use a single stator to generate torque and suspension forces to control the position of the rotor. Some measure of the airgap length is needed to enable stable magnetic suspension, so this thesis proposes the injection of a high-frequency carrier signal to the stator windings to amplify the change in coil inductance with rotor position. The coil response is demodulated against the carrier signal to provide an estimate for airgap length. This design uses a stator with 12 independently controlled windings to generate a 4-pole magnetic field for torque and a 2-pole magnetic field to control the rotor suspension. Analytical and finite-element simulation demonstrate that if the current in the windings is controlled, demodulating the winding voltage against the carrier signal gives a good estimate for rotor displacement. When the winding voltage is considered the input, the current through the coils can be used for estimation, but the result is highly dependent on the suspension field. The prototype developed to test this operating principle has been constructed and tested with voltage as the winding input. Inductive sensors are used to provide a "ground truth" signal to evaluate the estimation result and to provide feedback for the rotor suspension while the estimation is being developed. Initial results show that even under voltage control the SSBM prototype is able to estimate the rotor displacement, but only when the suspension control is active. Current control for the system has been developed and will be implemented as the immediate next steps.