Coaxial Tilt Damping Coil with Additional Active Actuation Capabilities

This work presents a tilt stabilization coil inside an exemplary high speed bearingless disk drive. The coil is based on the passive, electrodynamic “Null-Flux” principle where there are no coil currents and, thus, no losses when the rotor is non-deflected during rotation. The proposed conductor structure is then used as a means of active actuation on the rotor by energizing the coil actively for first producing tilt torque. Modifying the structure geometrically into multiple, coaxial conductor loops which are energized with currents in the same or in equal direction then allows producing additional axial forces and tilt torque with multiple degrees of freedom, depending on the coil design. Simulation and measurement at prototype drives demonstrate the functioning of both, the passive stabilization and the active actuation principles.