Improved Commutation in Sensorless Control of Brushless DC Motors by Index Pulse Comparison

In this paper, a method for Zero Crossing Point (ZCP) error correction to improve commutation accuracy, called Index Pulse Comparison (IPC), is proposed. Firstly, Brushless Direct Current (BLDC) motor is mathematically modeled and voltage and torque equations are extracted. Then, the twelve-pulse production strategy, which includes the creation of two types of pulses, is introduced and the time interval between each pulse is calculated. Finally, using the Index Pulse (IP), the deviation time from the ZCP is estimated and the commutation error is corrected. The advantage of the proposed method is the fast correction of ZCP detection error and accurate delay of 30 degrees after ZCP detection to determine commutation instances. The proposed method has been simulated in MATLAB/Simulink environment and its performance has been compared with the ZCP detection error. The simulation result has shown the effectiveness of the proposed method in correcting the ZCP detection error.