PLL control algorithm for precise speed control of the slotless PM brushless DC motor Using 2 Hall-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. Rotor position information can be provided by Hall-IC or sensorless algorithm. However, basically sensorless algorithm is not suitable for the complicated operation conditions of PM BLDC. So, the Hall-ICs are set up in this motor to detect the main flux from the rotor. Instead of using three Hall-ICs and encoder, this paper uses only two Hall-ICs for the permanent magnet rotor position and the speed feedback signals, and uses a microcontroller of 16-bit type (80C196KC) with the 3-phase slotless PM BLDC whose six stator and two rotor designed. Two Hall-ICs H_A and H_B are placed on the endplate at 120 degree phase difference. With these elements, we estimate information of the others phase in sequence through a revolving rotor. Also because of low resolution obtained by using Hall-IC even low-cost and simple structure, to improve the wide range of speed response characteristic more exactly, we propose the rotor position signal synthesizer using PLL circuit based on two Hall-ICs.