Linear and nonlinear control of a three pole combined radial and axial active magnetic bearing - a comparison

This paper analyses two control strategies, linear and nonlinear, for a 5-axis magnetic suspension system built with two three pole combined radial and axial bearings. Therein soft magnetic composites (SMC) are used as iron core material to carry the required three-dimensional flux distribution. While the linear approach has been designed around the CLARKE-Transformation to stabilize the bearing, the nonlinear one is based on feedback linearization to achieve a stable system even in the case of minimal bias flux. The paper outlines the control strategies and the controller design. Both schemes are compared regarding command response, decoupling performance and stability margin based on experimental results in the time and the frequency domain.