Magnetic stray field based position detection in BLDC outer rotor permanent magnet synchronous machines.

SUMMARY The stray field outside outer rotor permanent magnet synchronous motors can be used for rotor position detection. The focus of the research is on the optimal position of the sensors in order to provide accurate rotor position information. By using 2D and 3D models, the effect of the radial, circumferential and axial position of the sensors on the output signal is shown. Furthermore, the effects of the rotor yoke thickness and the stator current are studied: a thick rotor yoke obviously reduces the stray field amplitude, and high stator currents slightly shift the switching points of the Hall sensors, making the position information less accurate. Also, the rotor temperature and the orientation of the sensors towards the direction normal to the rotor surface are important: modifying the orientation causes a phase shift and is a way to tune the sensors without changing the position. Experiments show that an accurate brushless DC control is possible based on Hall sensors in the stray field. The motor and brushless DC control are used for a wheel drive of an ultra-light electric vehicle. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]