COMPENSATION OF TOOL AXIS MISALIGNMENT IN ACTIVE MAGNETIC BEARING SPINDLE SYSTEM

The tool axis misalignment, which causes machining inaccuracies in an active magnetic bearing(AMB)-spindle system, can be compensated by tra cking control of the rotor-spindle. The pseudo-derivative feedback(PDF ) control scheme alone does not correct the tool axis misalignment sin ce the integral action results in the narrow bandwidth and large phase lag in the controlled system. To improve the tracking performance, th e feedback and feedforward controllers are combined with the existing proportional-derivative controller, which stabilizes the inherently un stable AMB-spindle system dynamics. The theoretical and experimental r esults show that proposed control scheme efficiently compensates the t ool axis misalignment compared with the conventional PDF control schem e.