Two different control strategies for 16-pole rotor active magnetic bearings system with constant stiffness coefficients

Abstract

Rotor active magnetic bearing is one of the preferable supporting techniques for the high-speed rotating machinery. This article proposes a comparison between two different control strategies for the constant stiffness coefficients 16-pole rotor active magnetic bearings system (16-pole Rotor-AMBs). The first strategy is the Cartesian control in which the applied currents on the poles depend on the horizontal or vertical displacements of the rotor. The second strategy is the radial control in which the applied currents depend on the radial displacement of the rotor. Both strategies are based on the proportional-derivative (PD) control algorithm to make the rotor's vibrations track a zero reference point. The major novelty here is that we compare the two strategies to explore their advantages and disadvantages in controlling the 16-pole Rotor-AMBs. The analytical and numerical approximate predictions of the rotor's vibrations are extracted to show and verify the nonlinear dynamical behavior of the rotor based on the two methods. The local stability of the extracted solutions is analyzed via Hartman–Grobman theorem to conclude the stable and unstable solutions regions and the boundary between them. Various responses are included to show, in most conditions, that the radial control has a privilege over the Cartesian control in avoiding either the multi-stable solutions or the rub/impact forces occurrence between the rotating disk and the stator pole legs.