The tool axis misalignment,which causes the machining inaccuracies in active magnetic bearing(AMB)-spindle system, is compensated by tracking control of the rotor-spindle.
The pseudo-derivative feedback(PDF) control scheme alone does not correct the tool axis misalignment since the integral action results in the narrow bandwidth and large phase lag in the controlled system. To improve the tracking performance, the feedback and feedforward controllers are combined with the existing proportional -derivative controller, which stabilizes the inherently unstable AMB-spindle system. The feedforward controller is constructed simply by inverting the stabilized AMB-spindle system dynamics.
The theoretical and experimental results show that the proposed control scheme efficiently compensates the tool axis misalignment compared with the conventional PDF control scheme.