A four-quadrant control for permanent magnet brushless DC electric actuator

The torque could be controlled by controlling the phase current through investigating the relationship between phase current and torque of brushless DC motor (BLDCM) in this paper. Based on this, this paper presents a novel four-quadrant control method for brushless DC electric actuator. Firstly the feedback current is calculated according to the different position of the rotor. Then the hysteresis comparison between the feedback current and given current is implemented, to obtain the forward/reverse signals. According to the signals, the phase current is adjusted to control the torque in the end. In addition, the paper presents the investigation of BLDCM commutation torque ripple. The commutation torque ripple is eliminated by maintaining the constant value of non-commutation phase currents through setting 2α=α_t during the low speed operation of the motor. Therefore, the commutation torque ripple could be reduced using the control of the phase current of the four-quadrant control method. Simulation and experiments give the confidence that the proposed four-quadrant control method controls the phase current effectively, reduces the ripple of non-commutation current during the low speed of the motor and meets the requirements of the system dynamic performance.