Sensorless Position Estimator for Active Magnetic Bearings Based on Non-linear Voltage Equation and Square-wave Voltage Injection

This paper presents a novel sensorless position estimator for active magnetic bearings. The algorithm primarily consists of a first-order nonlinear finite difference equation for position estimation, derived from the direct discretization of the voltage equation. The performance of the estimator is enhanced by an additional square-wave voltage injection at the Nyquist frequency. Simulations and hardware tests are conducted to validate the performance of the estimator. The measured position repeatability of the proposed estimator is 6.41μm at 5kHz sampling frequency, which enables reliable levitation control.