A method for calculating a steering assist torque, for controlling the motor of an electric assist steering system, comprises the steps of: generating a low frequency torque signal from an applied steering torque signal by using a low-pass filter; calculating a low frequency assist torque on the basis of the low frequency torque signal; generating a relatively high frequency torque signal by using the applied steering torque signal and the low frequency torque signal; generating a high frequency torque signal from the relatively high frequency torque signal by using a high-pass filter; calculating a high frequency assist torque on the basis of the high frequency torque signal; and calculating a steering assist torque by summing the low frequency assist torque and the high frequency assist torque. The high-pass filter is equipped with a plurality of high-pass filters divided according to steering angle sections, and the relatively high frequency torque signal is selectively distributed to any one among the plurality of high-pass filters according to the size of the steering angle at a corresponding time point and the high frequency torque signal is generated.
MOTOR CONTROL METHOD AND DEVICE FOR ELECTRIC ASSIST STEERING SYSTEM