Mathematical modeling and simulation of Brushless DC motor with ideal Back EMF for a precision speed control

This paper presents a mathematical model of a three-phase Brushless DC motor based on precise speed control methodology with ideal Back EMF on MATLAB/Simulink platform. In this scheme, equivalent output of three hall sensors determine the rotor position at any instant of time and accordingly switch the six step inverter to drive the motor. The model is based on phase voltage and electromagnetic torque equation. Further analysis has been carried out with transfer function to achieve desired level of performance. Moreover, the ideal Back EMF is also derived from mechanical speed and mechanical angle of the rotor. A wide variation of speed control is accomplished with a PI controller due to its simple control structure and ease of implementation. The final analysis on the speed-torque characteristics for the designed Brushless DC motor show quite satisfactory output for varying (0-20 N-m) load torque applications.