Quantitative Characteristic Comparison between Sensorless Six Step and Field Oriented Control Methods for Permanent Magnet Brushless DC Motors

Permanent magnet (PM) brushless DC motors (BLDCM) have the advantages of high power density, high efficiency, simple structure and high reliability. BLDCM can be categorized into either trapezoidal back-electromotive (EMF) motor type, or sinusoidal back-EMF motor. There are typically two BLDCM control methods: One is six step control method which is easy to realize with simple hardware, the other is field oriented control (FOC) method which has better control performance. This paper compares quantitatively the characterization between these two BLDC control methods, with respect to torque ripple and power losses. Theoretical analysis and simulation studies are presented to illustrate their advantages and disadvantages. Experimental verification is conducted using a 48V, 4-pole, 4500RPM BLDC motor.