Speed control of high-performance brushless DC motor drives by load torque estimation

This paper presents a novel robust speed control method based on the load torque observer of high-performance brushless DC (BLDC) motor. Recently, high-performance BLDC motor drives are widely used for variable speed drive systems of the industrial applications. In case of the control of robot arms and tracking applications with lower stiffness, we cannot design the speed controller gain to be very large from the viewpoint of the system stability. Thus, the feedforward compensator with disturbance torque observer was proposed. This method can improve the servo stiffness without increasing the speed controller gain. The enhanced speed control performance can be achieved and the speed response against the disturbance torque can be improved for high-performance BLDC motor drive systems in which the bandwidth of the speed controller cannot be made large enough. The load disturbance is compensated by detected load torque through the observer. The compensation current is made through q-axis current. The d-q transform of phase currents were possible by the Fourier series summation method. Consequently, the speed control for high-performance BLDC motor drives become improved. The simulation results for BLDC motor drive systems confirm the validity of the proposed method.