A System Identification Technique Using Bias Current Perturbation for the Determination of the Magnetic Axes of an Active Magnetic Bearing

Abstract

Inherent in every Active Magnetic Bearing (AMB) are differences between the expected geometric axes and the actual magnetic axes due to a combination of discrepancies, including physical variation from manufacturing tolerances and misalignment from mechanical assembly, fringing and leakage effects, as well as variations in magnetic material properties within a single AMB. A method is presented here for locating the magnetic axes of an AMB that will facilitate the accurate characterization of the bearing air gaps for potential improvement in field tuning, performance analyses and certain shaft force measurement techniques. This paper presents an extension of the application of the bias current perturbation method for the determination of the magnetic center to the determination of magnetic axes for the further development of accurate current-based force measurement techniques.

Dual flexible rotor system with active magnetic bearings for unbalance and coupling misalignment faults analysis

“…An extension of [16] is presented by authors of [17] by considering flexible shaft system and applying a more practical solution approach, i.e., finite element method (FEM). The influence of bias current is studied to identify the center position of AMB [18]. They presented a bias current perturbation technique to determine the magnetic axis and measurement of current force; also, identified the influence of air gaps in the AMB system.…”

Actuators for Active Magnetic Bearings

“…Spangler et al [10] develop and explore a technique for characterizing the magnetic properties of an AMB in situ. This allows compensation for manufacturing tolerance and misalignment between mechanical coordinates and centers and magnetic coordinates and centers during the commissioning process of an AMB.…”