The Direct Torque Control for Permanent Magnet Brushless DC Motors

Permanent magnet brushless DC motors (BLDCM) have been more and more widely used in industry applications because of their advantages such as higher ratio of power to volume, lower noise and easier maintenance compared to permanent magnet DC servo motors. However, torque ripple generated in commutation period is the main drawback of BLDCM, which make the application of BLDCM in the high accuracy system impossible. The direct torque control (DTC) can control the torque instantly. This method observes the fluxlink and torque of the motor in the stator coordinate, and compares the observed values with the set values to obtain the error. And then the control signal is obtained by inputting the error to the controller. Finally, with this control signal and the state of fluxlink, the corresponding voltage space vector is selected, so that the torque can be controlled directly. In this paper, DTC is used to control the BLDCM, in the purpose of reducing the torque ripple. Simulation and experiment results show that the DTC method can minimize the torque ripple of BLDCM effectively and gain rapid dynamic response.