| 摘要 |
PROBLEM TO BE SOLVED: To provide an electric power steering device which can obtain a frictional coefficient of a road surface without the necessity of a specific sensor, and which can assist in a steering force on the basis of the obtained frictional coefficient. SOLUTION: This electric power steering device for determining a desired value of motor current for a steering force assist motor 24 in accordance with a value detected by a torque sensor 10 detecting a steering torque applied to a steering wheel (which is not shown) and a frictional coefficient between steered wheels and a road surface, and for rotating the motor 24 so as to set the motor current to the desired value in order to assist in steering force, comprises a brushless motor as the motor 24, a steering speed calculating means 12 for calculating a steering speed of the steering wheel from a value detected by a rotor position detector 14 for detecting a position of a rotor in the bushless motor 24, a torque variation calculating means 12 for calculating a variation in torque from a value detected by the torque sensor 10, and a means 12 for obtaining the friction coefficient from the steering speed and the torque variation.
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