Flux Based Control of AMBs Using Integrated Ultra-Thin Flexible Bismuth Hall Sensors

To increase stiffness and precise rotor positioning of active magnetic bearings (AMB), flux based control algorithms were suggested. However, the typical thickness of air gaps in AMBs is too small to apply conventional magnetic field sensors with a typical thickness of more than 500 µm. Furthermore, the curved surfaces of the sta tor poles require a mechanically flexible sensor design. Here, we propose a flexible Bismuth based Hall sensor with a total thickness of only 80 µm including encapsulation. After wiring th e sensors have a maximum height of 280 µm and could be mounted onto curved surfaces. T he fabricated sensors were characterized and the influence of size, temperature and bending radius on the Hall sensitivity was determined. On a proof-of-concept level we demonstrated the performance of the flexible magnetic field sensors to control an one-axis AMB with a levitating ball. Several algorithms using flux density measurements were tested and compared to conventional control strategies.