Closed loop control commutation strategy of brushless DC motors without position sensor based on virtual neutral point

To reduce the commutation error of Brushless DC motors position sensorless, this paper presents a novel Non position commutation error corrected method achieved by a close loop, and which is based on virtual neutral point of the brushless DC motor. voltage difference between the virtual neutral point and middle point of driving voltage are identified. The relationship between the voltage difference and Commutation error are also analysed in this paper. After that, the voltage difference was sampled before and after the commutation points. These two results are subtracted as feedback quantity in commutation error controller. Then a control loop is established to reduce the commutation error which aim is the voltage difference approaching zero. The control part is a PI controller. In the Experiment, 15° commutation error is given to verify the method, The result proves that this method is stable and reliable, and it can component the commutation time quickly when it is influenced by external factors. It only took about 70 steps to convergence to the steady state at 1500 r/min and 40 steps at 3000 r/min for the 15°.