3 degrees of freedom control of semi-zero-power magnetic levitation suitable for two-dimensional linear motor

Electromagnetic suspension (EMS) has been widely used in many industrial fields because of various advantages in practical use. The U-type magnets are often used to generate the levitation force in the EMS system. This conventional electromagnet, however, can only control one degree-of-freedom. It cannot construct a levitation system solely by itself. A four-pole type yoke hybrid electromagnet is proposed instead of the usual U-type magnet and its magnetic levitation control is studied in this paper. The basic structure and characteristics of the proposed magnet are described first. Next the control system is designed. Luenberger observer, only using gap sensors, is applied to realize zero-power control. The semi-zero-power control with a disturbance observer is proposed to improve the performance, as well as the robustness, of the control system. The ideas of coordination with linear motor are discussed. Finally, the simulation results and corresponding experiments have been presented.