Patent ID: 8082080

Claim:
An electric power steering apparatus, comprising: a motor; a steering force assist device that uses the motor as a drive source to apply assist force to a steering system, thereby assisting a steering operation; a torque sensor for detecting a steering torque of the steering system; and a controller for controlling an operation of the steering force assist device, the controller further comprising; a computation section that computes a basic assist force applied to the steering system based on the steering torque detected by the torque sensor, a compensation section that computes a compensation amount that compensates for the steering torque used in the computation of the basic assist force, thereby adjusting the basic assist force; and a filtering section that subjects the compensation amount obtained at the compensation section to a filtering process with a filter constant that represents the degree of filtering effect, wherein the state of the steering operation includes a turning for increasing the steering angle, a holding for maintaining the steering angle, and a returning for reducing the steering angle, wherein the controller determines which one of said returning, said holding, and said turning the state of the steering operation is, wherein, when the state of the steering operation is said returning or said holding, the controller sets the filter constant to a value that inhibits the compensation amount from sharply changing, and wherein, when the state of the steering operation is said turning, the controller changes the filter constant so as to reduce the filtering effect.