Implementation of the ADRC Technique in the Radial Position Control of a Bearingless Permanent Magnet Synchronous Machine.
ADRC, bearingless machine, permanent magnet machine, radial position control.
The objective of this work was to implement and test radial position control of the rotor of a bearingless permanent-magnet synchronous machine using the Active Disturbance Rejection Control (ADRC) technique. The operation of bearingless machines is highly dependent on the application of closed-loop control strategies. Due to its multivariable, nonlinear, and time-varying nature, with strongly coupled variables, the system requires the use of advanced control strategies for efficient operation and good dynamic performance. The ADRC technique addresses these complexities by treating the total system disturbance—which encompasses unmodeled dynamics, nonlinearities, parametric uncertainties, and load variations—as a new system state. This state is estimated in real time using an extended-state observer, enabling active compensation, elimination of steady-state errors, and a satisfactory dynamic rotor response. To validate the study, a cascade control architecture was used on a horizontal permanente-magnet prototype with a 4/6 topology (four poles for torque and six poles for radial suspension). The strategy employed classical PI controllers to act on the inner current loops and robust ADRC controllers to directly control the outer radial position loops. The experimental results demonstrated the effectiveness of the approach; the system was able to track the references, estimate and compensate for couplings, and keep the rotor properly centered with low deviations, even during acceleration tests with the rotor suspended in four degrees of freedom.