Auto lead angle algorithm for high efficiency control of BLDC Motor

The Brushless DC motors are used in various industries such as home appliances, electric vehicles, Medical, Industrial automation equipment and so on. Because they have advantages of low noise, simple control and high power density. But, in a high-speed motor drive, current lagging which is induced by the impedance of the motor inductor reduces the motor efficiency. To solve this problem, we propose an auto lead angle control algorithm based on a gradient descent algorithm. With this algorithm, the motor current and motor Back-EMF have an identical phase angle. Thus, the efficiency of the motor can be increased. In order to verify the proposed algorithm, we implemented the hardware with FPGA and board including analog circuit. As a result, it was confirmed that the optimum lead angle was found with only one current value without various parameters, and the efficiency of the motor was improved. Also, it is confirmed that the efficiency is further increased at high load and high speed.