Initial Rotor Position Estimation Method for PM Motors

This paper presents a method to detect the rotor position of PM motors at standstill. It is suitable to avoid temporary reverse rotation or starting failure. The basic approach is the well-known method to estimate the rotor position by using the inductance variation as a function of the magnets position and the stator currents: a suitable sequence of voltage pulses is applied to the stator windings and the evaluation of the peak value of the current leads to the rotor position estimation. Actually, the current measurements show significant uncertainties which affect the rotor detection. In order to avoid these problems, the authors propose a novel procedure which combines an iterative sequence of voltage pulses with a fuzzy logic processing of the current responses and phase currents derivation based on the dc link current measurements. The proposed method has been implemented on a uC DSP(TMS320F240). The obtained results confirm the effectiveness of the proposed solution. It is consistent with sensorless or non absolute position transducers drives, a wide range of motors and it does not require the knowledge of any of the motor parameters.