M. Hofer, M. Hutterer, Th. Nenning, M. Schrödl:
"Improved Sensorless Control of a Modular Three Improved Sensorless Control of a Modular Three";
Talk: 14th International Symposium on Magnetics Bearings, Linz; 08-11-2014 - 08-14-2014; in: "Proceedings of 14th International Symposium on Magnetics Bearings", (2014), 679 - 684.

This paper discusses new results and improvements
on the sensorless control of a permanent magnet biased three
phase radial active magnetic bearing (AMB), which are also
known as hybrid magnetic bearings (HMB). Self-sensing methods
offer cost potentials because of a more simple bearing system
architecture, but show lower performance in accuracy and bandwidth
compared to external position sensors. Thus, making selfsensing
technologies competitive to systems with position sensors
is a broad field of research and as well a goal of this paper. The
proposed sensorless method is based on inductance measurement
by voltage pulse injection. Applying an oversampling strategy for
current slope measurement reduces the noise of the sensorless
obtained rotor position significantly. Timing limitations and
operational bandwidth can be improved by utilizing alternative
voltage pulse sequences. Further, variations of the permanent
magnet bias flux of the HMB prototype are investigated to show
the influences on the sensorless rotor position detection method
and limitations for applications.

http://publik.tuwien.ac.at/files/PubDat_230385.pdf