Self-sensing magnetic bearings using multiple sampling of currents alone

This paper presents a new technique to estimate the rotor position for self-sensing magnetic bearings. The current slope, which is caused by the switching voltage of the PWM amplifier, is used to estimate the rotor position. One highlight of the proposed technique is to calculate the current slope from more than two samples of currents within one PWM cycle. Thus, using multiple sampling of coil currents alone, no additional hardware than that for a current control is needed for the position estimation. The position control of a single-axis magnetic bearing, using the proposed technique, was successfully implemented.