Patent ID: 7091684

Claim:
An electric power steering apparatus which includes a three-phrase motor that supplies a steering assist power to a vehicle steering system, a torque sensor that detects a steering power to affect a handle, and at least two current detectors that detect phase currents of the three-phase motor, and controls an electric current of the three-phase motor based on a current command value determined based on an output value from the torque sensor and the electric current of the three-phase motor, comprising: a current detect or failure specifying section that specifies a failure current detector and a normal current detector when the current detector breaks down; and a first current calculating section that calculates the phase currents of the three-phase motor from a detected current for one phase detected by the normal current detector, wherein the electric current of the motor is continued to be controlled based on the calculated phase currents, the first current calculating section includes a three-phase/two-phase converting section that inputs the detected current for one phase detected by the normal current detector and an estimated current for at least one phase which is substituted for a detected current of the failure current detector therein, two low pass filters that are arranged at an output of the three two-phase converting section, and a two-phase/three-phase converting section that inputs the outputs from the low pass filters therein, an electric current corresponding to the estimated current in the three-phase currents as an output from the two-phase/three-phase converting section is feed-backed as the estimated current.