Reduction of torque ripple in AC motor drives for electric power steering

EPS (electric power steering) have attracted much attention for their advantages with respect to improved fuel consumption and have been widely adopted as automotive power-steering equipment in recent years. In the EPS system, the fact that motor vibration and torque fluctuations are directly transferred through the steering wheel to the hands of the driver must be considered. Because of switching device and current offset according to the temperature variation, torque fluctuation in the motor has many undesirable harmonic ripples. In this paper, the offset current error compensation method to overcome high temperature variation and compensation method to reduce current distortion caused by FET voltage drop and dead time for low voltage and high current applications is demonstrated.