Electronmagentic suspension control without air gap measurement

Novel controllers for electromagnetic suspensions are investigated, the important feature of which is that measurement of the airgap is not needed. The paper explores the hypothesis that measurements of magnet current and airgap flux density should be sufficient for stable control, and it examines strategies by which such control can be achieved. A somewhat unexpected control strategy emerges from the investigation, and this is supported by a theoretical stability analysis and by simulation.