Patent ID: 7826950
Filing Date: 2010-11-02
Classification: B62D

Abstract:
1. An electric power steering apparatus comprising: a motor for generating steering assist power; a torque sensor for detecting a steering torque of a steering wheel; a vehicle velocity sensor for detecting vehicle velocity; a controller comprising a computer, the controller being in at least indirect connection with the motor, torque sensor, and vehicle velocity sensor; wherein the controller performs operations comprising: storing a correspondence relationship between a detected steering torque detected by the torque sensor and a basic assist torque, whereby the relationship between the detected steering torque and the basic assist torque defines an assist gradient as a quotient of a rate of change of the basic assist torque to a rate of change of the detected steering torque; controlling steering assist power generated by the motor based on a basic assist current according to the basic assist torque corresponding to the detected steering torque and a vehicle velocity detected by the vehicle velocity sensor; determining the assist gradient corresponding to the detected steering torque; determining a change acceleration corresponding value that corresponds to an acceleration of change of the steering torque by second order time differential of the detected steering torque; storing a correspondence relationship between the change acceleration corresponding value and a correction basic current that is in direct correlation with the change acceleration corresponding value; calculating the correction basic current corresponding to the determined change acceleration corresponding value; storing a correspondence relationship between the assist gradient and an assist gradient gain such that the assist gradient gain decreases as the assist gradient increases; calculating the assist gradient gain corresponding to the determined assist gradient; multiplying the calculated correction basic current and the calculated assist gradient gain to obtain a multiplication product; and correcting the basic assist current according to the product; whereby a correction amount of the basic assist current is varied according to the variation of the assist gradient.