Research on control of non-ideal permanent magnet brushless motor in view of torque ripple minimization

Due to some inevitable restrictions during fabrication of permanent magnet brushless (PMBL) motors, some of them have neither sinusoidal nor trapezoidal back-EMF voltages, and these types of motor are named non-ideal PMBL motors. Employing conventional control strategies of permanent magnet synchronous motors (PMSMs) and brushless DC motors (BLDCMs) leads to lower efficiency and causes unwanted torque ripple, vibration and acoustic noises. This paper explores a review on control of non-ideal PMBL motors and investigates the torque response of non-ideal PMBL motor while is controlled with conventional control strategies and presents a novel torque ripple minimization method. Investigated control strategies include quasi-square current control using dc-link current, quasi-square current control using three phases current, direct torque control, vector control, and pseudo vector control that are used for speed control of non-ideal PMBL motor. Then, a novel torque ripple minimization based on selective torque harmonic elimination and using one cycle control strategy is suggested. Simulation results indicate the non-ideal PMBL motor by novel proposed method develops smoother torque and lower torque ripple rather than all previous control strategies. It is suitable for any PMBL motor with any back-EMF voltage waveform.