Initial rotor position estimation for sensorless brushless DC drives

This paper presents a method to determine the initial rotor position of a brushless DC machine at standstill without a position sensor. The key principle of the rotor position estimation is based on the simple detection and comparison of phase voltage and current responses relating to the stator inductance varied with the position of the rotor magnet. In the proposed method, only three pulse voltage injections are applied and 30 degree resolution can be achieved. Moreover, no knowledge of machine parameters is required. The effectiveness of the proposed method is validated by experimental results.