Electric power steering system

摘要

An electric power steering system includes a motor control device that controls, based on an assist command value (Tas), driving of a motor that gives an assist torque to a steering mechanism. The motor control device computes a first assist component (Tal) based on a steering torque (Th) and a vehicle speed (V). A steered-angle command value (θp*) is computed based on the steering torque (Th) and the first assist component (Ta1), and a second assist component (Ta2) is computed by performing a feedback control that matches the steered angle (θp) with the steered-angle command value (θp*). The motor control device adds the second assist component (Ta2) to the first assist component (Ta1) so as to compute an assist command value (Tas). The motor control device includes a road information compensation portion (45) that decreases an absolute value of the second assist component (Ta2) included in the assist command value (Tas) when a skid is detected by a vehicle state detecting portion (46).