A new simple sensorless control method for switched reluctance motor drives

In this paper, a new impedance sensing method is described. This method overcomes the shortcomings of the impedance sensing method. According to the new method, sensing voltage pulse is applied to the idle phase in the minimum inductance region and the beginning of the increasing inductance region to detect rotor position. The negative torque produced by the sensing voltage pulse can be neglected in the minimum inductance region and the efficiency of SRM is improved. In the minimum inductance region the back EMF can be neglected. And in the increasing inductance region the EMF opposes the rise of current in the phase, so the position estimation scheme is reliable. Therefore the new "impedance sensing" method is sufficiently precise even under the high back EMF effect. The adjustment of turn-on angle and turn-off angle is also easy to be realized. The technique is very useful in applications where cost or size is primary concerns, such as electric bicycle drives. Experimental results are presented to verify the proposed method.