Sensorless control of PMSM at low speed range using reference model

A new control structure is presented for use at the sensorless control of speed for low speed range. That method uses an observer for position estimation. Such structure does not require the calculation of the speed value from the estimated back EMF, thus such drive can work even in a case of non-sinusoidal shape of estimated back EMF. Such structure is especially recommended for speed in a range single revolutions per second (excluding standstill). Proposed structure is similar to the model following control, but the reference model is trying to track the motor operating point.