Sensorless Direct Torque Control in Brushless DC Motor Using Sliding Mode Observer

Brushless Direct Current (BLDC) motors have obvious advantages such as simple structure, low cost, high output torque, and high efficiency, making them more widely used than other types of motors. Control strategies for BLDC motors necessitate rotor position; however, position sensors are susceptible to malfunctions that can incapacitate the entire motor system. Furthermore, commutation torque pulsation in BLDC motors constrains their application, contributing to vibration and noise during prolonged operation. To address these issues, a sensorless direct torque control (DTC) strategy is devised by integrating position estimation by a proposed sliding mode observer (SMO) with direct torque control (DTC) technology. This strategy estimates the back electromotive force and speed to calculate the instantaneous electromagnetic torque applied to the BLDC motor and restricts the torque ripple to approximately 0.25 N.m. Simulation verification confirms the feasibility of the strategy.