The self-gap-detecting electromagnetic suspension system with robust stability against variation of levitation mass

There are few self-gap-detecting electromagnetic suspension (EMS) systems robust enough against variation of coil resistance. The authors succeeded in providing much robustness against the variation of coil resistance with a self-gap-detecting EMS system. An adaptive control to coil resistance and an exciting voltage compensation for difference between the coil resistances were applied to the self-gap-detecting EMS system. The adaptive control covered the feedback controller and the state observer which evaluates gap length and its change rate with respect to time. The exciting voltage compensator was used to prevent interaction between plural control axes due to the coil resistance difference. As a result, it made clear that this self-gap-detecting controller yields more robustness against levitation mass variation to EMS systems than conventional controllers with gap detectors. The experimental result shows that the proposed controller can keep stability of the EMS system from variation of 50 % of levitation mass