Application of Robust Control to Chatter Attenuation for a High-Speed Machining Spindle on Active Magnetic Bearings

The purpose of this work is to demonstrate a robust control strategy to avoid machining chatter in a high-speed machining spindle levitated on active magnetic bearings. Chatter avoidance is an important aspect in machining because chatter limits the material removal rate and inhibits production. A method is implemented which uses µ-synthesis AMB control with a cutting force model in the controller design process. Such an approach causes the controller to stabilize the naturally unstable cutting process, avoiding chatter and resulting in smoother surface finish, longer tool life and increased material removal rate. Stability lobe diagrams are calculated for the new control strategy showing increased critical feed rate and confirmed through numerical simulations. The developed method is implemented experimentally on the high-speed AMB machining spindle. Impulse hammer testing is performed to measure the controlled spindle’s transfer function and evaluate chatter free machining suitability.