Precision Positioning Oriented Modeling of Electromagnetic Actuator

This article presents a novel approach for accurate modeling of the relation between force, electric current and the actual air gap in the electromagnetic actuator used in active magnetic bearings (AMB) based precision positioning systems. The novelty of the presented modeling approach lies in a newly derived correlation for the relative permeability term in the electromagnetic actuator force model. This correlation, which can be easily obtained using the B-H curve for a given low-hysteresis actuator core material, describes the relative permeability term by means of electric current, actual air gap and a few parameters of the actuator. The resulting actuator model, which can be used either for more correct implementation of the well-known feedback-linearization technique or for obtaining more reliable results in simulations, was validated experimentally using a real single-degree-of-freedom (S-DoF) AMB plant.