Patent ID: 7664619
Filing Date: 2010-02-16
Classification: G01D

Abstract:
1. A fault detection unit for detecting a fault occurred in a detecting device which detects a rotational angle of a rotor with respect to a stator from a sine-wave phase signal and a cosine-wave phase signal of which amplitudes are modulated in a sinusoidal wave shape so as to be changed in a cycle of the rotation of the rotor, the fault detection unit comprising: a first section which produces a fault judging value from the sine-wave phase signal and/or the cosine-wave phase signal received from the detecting device; a second section which judges based on the fault judging value placed out of a normal range that a fault has occurred in the detecting device; a third section which judges the detecting device to be in a tentative fault state, in response to continuation of the judgment by the second section for a first predetermined period of time; a fourth section which examines whether the rotational angle is changed over its entire range and judges the detecting device, judged by the third section to be in the tentative fault state, to have returned to a normal state, in response to the rotational angle changed over the entire range and the fault judging value always placed within the normal range during the change of the rotational angle over the entire range; and a fifth section which judges the detecting device to be in a determinate fault state in response to continuation of the judgment by the second section for a second predetermined period of time which is longer than the first predetermined period of time, and decides occurrence of a fault in the detecting device.