Patent ID: 7994776

Claim:
A failure detection apparatus for a resolver, the resolver being configured to output a sine signal indicative of sin θ and a cosine signal indicative of cos θ according to a rotational angle θ of a rotator, the failure detection apparatus comprising: a first inspection value calculating section configured to calculate a first inspection value based on at least one of the sine signal and the cosine signal; a second inspection value calculating section configured to calculate a second inspection value and a third inspection value on the basis of the first inspection value, to assign the first inspection value to the second inspection value if the first inspection value is greater than the second inspection value, to decrease the second inspection value gradually with a lapse of time if the first inspection value is smaller than the second inspection value, to assign the first inspection value to the third inspection value if the first inspection value is smaller than the third inspection value, and to increase the third inspection value gradually with a lapse of time if the first inspection value is greater than the third inspection value; and a failure detecting section configured to judge whether the resolver is in a failure state or not on the basis of the second and third inspection values; a counting section configured to increase a count value when the failure detecting section is determining that the resolver is in the failure state, and configured to decrease the count value when the failure detecting section is determining that the resolver is not in the failure state; and a failure deciding section configured to decide that the resolver has caused the failure on the basis of the count value.