Electric power steering device including rotation angle detection device

An electric power steering device, comprising a rotation angle detection device, the rotation detection device comprising:

• a coefficient identification circuitry configured to identify, based on a sine signal and a cosine signal which are based on a rotation angle of a motor, coefficients of frequency components included in the sine signal and the cosine signal, wherein identifying the coefficients includes application of low-pass filters to products of an M-th power of the sine signal and an N-th power of the cosine signal;
• a correction value calculator configured to calculate correction values based on the coefficients identified by the coefficient identification circuitry;
• and
• a rotation angle calculator configured to calculate the rotation angle of the motor based on values obtained by correcting one of the sine signal or the cosine signal, or both thereof, through use of the correction values;
• wherein the electric power steering device is configured to cause the motor to generate an assist torque based on the rotation angle of the motor.