First-Pulse Technique for Brushless DC Motor Standstill Position Detection Based on Iron B-H Hysteresis

This paper introduces a promising technique, called the first-pulse technique, for detecting the rotor position of a brushless DC motor at standstill. The technique is based on the B-H hysteresis characteristics of the stator iron. Depending on the rotor position, a very particular phenomenon related to B-H hysteresis appears. Voltage pulses are injected into the motor phases, without the need of saturating the stator teeth. In the first-pulse technique, the rotor position is estimated not by an absolute measurement, but by the comparison between the measurated effects created by the first injected pulse and the following ones. This technique permits to detect the electrical position of a non-salient rotor.