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UBC Theses and Dissertations

A new type of magnet array for planar motor Chen, Rui


Non-contact 6-DOF planar motors are playing more and more important roles in high precision machine tools, such as photolithography machines in semiconductor industry. Among existing planar motor designs, magnetically levitated planar motors with moving magnet have the potential to greatly improve the performance of motion stages by eliminating the force disturbance from umbilical cables and hoses that supply electricity and cooling water to motion stages, and can be easily extended to multiple-stage application. However, moving magnet planar motors suffer from intrinsic high-order force ripples that are generated by the interaction between stator coils and magnetic field harmonic components from magnet arrays. This thesis presents the design, analysis and experimental results of a novel magnet array for planar motor application, termed as M-Magnet array. An M-Magnet array consists of four identical magnet pieces per spatial period. Each magnet piece has a magnetization axis in 45 degree direction relative to its side surfaces, instead of 0 or 90 degree magnetization pieces used in conventional Halbach arrays. Previous symmetric magnet array contains 5 magnet pieces at each spatial period with the two edge pieces having half width of inner magnet pieces. The new M-magnet array design allows a symmetric magnet array made of 4 identical pieces. In addition, M-Magnet array design has the scalability to be extended to various sizes of mover with only one type of magnets, which makes the manufacturing of movers more cost effective. This thesis develops 3D analytical models to investigate the actuating force and torque generation of magnet arrays, and its sensitivity to manufacturing tolerances. A novel hybrid array design based on M-Magnet array is presented which can attenuate 6th force ripple by a factor of 100 without sacrifice of force constant of the planar motor compared to existing array splitting solution. The new M-Magnet array and hybrid array designs are analyzed via 2D and 3D models. An M-Magnet array is fabricated and experimentally tested at two distances from the magnet array bottom plane. The experimental results match the calculation results from 3D analytical models within 3% deviation, which confirms the validity of the 3D models.

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