A Novel Starting Method of Sensorless BLDC Motors for Electric Vehicles

A novel starting method of the brushless DC (BLDC) motors without position sensor for electric vehicles (EV) is proposed, including detecting of rotor position at standstill and a start-up method to accelerate the rotor up to a certain speed where the conventional position sensorless control methods based on the back EMF could work effectively. The whole starting procedure is accompanied with rotor position estimation, which can avoid the temporary reverse rotation and the starting failure of electric vehicles. The principle of the estimation is based on the variation of the current response caused by the magnetic saturation of the stator core of BLDC motor when the current flows along the magnetic axis. Further more, specific strategies of starting torque optimization and noise reduction are developed to start electric vehicles quickly and smoothly. This method is implemented with only one current sensor at the DC bus of the inverter and a low-cost general-purpose microcontroller, which becomes a simple, compact, low-cost, and effective solution for sensorless BLDC motors in the field of electric vehicles. It is demonstrated experimentally that a rapid and stable starting can be achieved by the proposed method.