[Problem]
An object of the present invention is to provide an electric power steering apparatus with high quality and reasonable price that estimates a motor shaft angle and a steering shaft angle with high accuracy by learning nonlinear elements of a mechanism system and a steering system, and can back up the both angle sensors by utilizing the estimating angles of the angle sensors.
[Means for solving the problem]
The present invention is the electric power steering apparatus that a motor to assist-control a steering system of a vehicle is connected to a steering shaft via a reduction mechanism, and comprises a first angle sensor to detect a steering shaft angle of the steering shaft and a second angle sensor to detect a motor shaft angle of the motor, comprising: a function that obtains compensation value maps by iteratively learning characteristics of nonlinear elements including the reduction mechanism based on an actual measuring angle of the first angle sensor, an actual measuring angle of the second angle sensor, a motor torque and a motor angular speed, and estimates the steering shaft angle and the motor shaft angle by using the compensation value maps.