Sensorless Direct-Torque-Control Of Brushless DC Motor

In this paper, a method which is the direct torque and sensorless control of the brushless DC motor for the control of BLDCM is presented. Firstly, it describes a mathematical model of the BLDCM, which is validated by a common control method—PWM current controller. The approach that the direct torque control(DTC) is applied for the BLDCM is studied. In this approach, the mathematical model of the inverter and the voltage space vector and the corresponding voltage space vector table are built. And the stator magnetic flux model and its control locus are studied. Through simulations the above two methods are compared and it represents that the DTC can effectively reduce the torque pulsations.A sliding-mode observer is employed to estimate the back-EMF waveform, and a extended Kalman filter is used to estimate the rotor speed. Through that, the key issue of the DTC which is the calculation of the instantaneous torque is solved and the sensorless control of the BLDCM is realized in order to simplify the systematic structure. The effectiveness of this approach is validated by simulations.