Sensorless control algorithm of BLDC motors with current model

This paper proposes a new sensorless control algorithm of BLDC(Brushless DC) motors with current model based on the 120 degree conduction mode. The rotor speed and the position can be estimated by using the current model of BLDC motor which is modified version of the conventional current model of PMSM(Permanent Magnet Synchronous Motor) sensorless method. The rotor position and the speed can be obtained by using the difference of the actual current and the model current. The position error caused by the parameter errors of the current model, current distortion at commutation points and nonideal trapezoidal shape of back-EMF is also compensated by using simple PI controller and the feedback loop of the real current. The validity of the proposed sensorless control algorithm is verified through several experiments.