Speed control system of slotless PM brushless DC motor using 2Hall-ICs

The high performance drives of the slotless permanent magnet brushless DC (PM BLDC) motor can be achieved by the current control, where the currents flow according to the rotor position and the current phase is suitably controlled according to the operation condition. The inexpensive Hall-ICs are a right choice or the so-called back EMF sensorless algorithm can be used for the rotor position sensing. Generally, to drive and control of the PM BLDC, it is necessary that the three Hall-ICs evenly be distributed around the stator circumference and encoder be installed in case of the 3 phase motor. So, the Hall-ICs are set up in this motor to detect the main flux from the rotor, and the output signal from Hall-ICs is used to drive a power transistor to control the winding current. However, instead of using three Hall-ICs and encoder, we used only two Hall-ICs for the permanent magnet rotor position and for the speed feedback signals, and also for a microcontroller of 16-bit type (80C196KC) with the 3 phase PM BLDC whose six stator and two rotor designed. Two Hall-ICs CS1 and CS2 are placed on the endplate at 120 degree intervals, and with these elements, we estimated information of the others phase in sequence through a revolving rotor.