Adaptive Threshold Correction Strategy for Sensorless High-Speed Brushless DC Drives Considering Zero-Crossing-Point Deviation

This article investigates the influence of two nonideal factors on zero-crossing-point-detection-based sensorless control of high-speed brushless dc (BLDC) motor, i.e., asymmetric machine parameters and the resistance tolerance of back electromotive force (EMF) measurement circuit. Influenced by the machine parameter asymmetry, the back EMF envelopes will shift horizontally from its ideal position. Furthermore, the acquisition accuracy of back EMF is limited by the resistance tolerance of measurement circuit. Inaccurate acquisition of back EMF will result in vertical deviation of the envelopes. These two nonideal factors decrease the commutation accuracy and deteriorate the control performance. In order to suppress the commutation errors, an adaptive threshold correction strategy, including horizontal and vertical corrections is proposed for eliminating the influence of these two nonideal factors, respectively. In addition, the proposed correction method does not depend on any parameters of the machine or the measurement circuit. Finally, the theoretical analysis and the proposed correction method are verified by experiment on a 54 000 r/min high-speed BLDC drive platform.