Torque Ripple Reduction of BLDC Traction Motor of Electric Wheelchair for Ride Comfort Improvement

In this study, a method to reduce the torque ripple of brushless direct current (BLDC) traction motor which drives the electric wheelchair is discussed. As the main users of electric wheelchair are mobility handicapped people, it is important to decrease the speed ripple of the wheelchair for their comfort and safety and for this, reducing the torque ripple of traction motor can be a solution for this problem, because the fluctuation of vehicle speed is affected by ripple of the driving torque, especially at lower speed. The waveforms of current and back electromotive force (EMF) of motor need to be considered because they determine the torque characteristics such as average value and ripple. After the current waveform of BLDC motor is calculated by simulation, back EMF waveform that reduces the torque ripple is determined as a trapezoidal form. The traction motor for electric wheelchair reducing torque ripple is designed by optimization process. The design parameter selected from the sensitivity analysis are optimized through kriging surrogate model. Finally, the back EMF waveform and the torque ripple of BLDC motor are verified by conducting experiments.