Position sensorless direct torque control of BLDC motor by using modifier

Direct torque control (DTC) can directly control the inverter states in order to reduce the torque error within the prefixed band limit DTC of brushless dc drive with trapezoidal back-EMF is presented in this paper. Using the rotor flux vector position in alpha - beta axis stationary reference frame and torque error, the proper switching pattern can be selected to control the generated torque and reducing commutation torque ripple. Sliding mode observer, which is robust to parameter uncertainties can be used to estimate the back-EMF and the generated torque. The rotor flux vector position estimation and its novel modifier can be achieved using a rotor flux observer. Simulation and experimental results confirm that the proposed method is good idea to introduce reliable sensorless scheme.