Patent ID: 6459972
Filing Date: 2002-10-01
Classification: B62D

Abstract:
A diagnostic apparatus for a motor driven power-assisted steering system of an automotive vehicle, comprising:a motor controlling section that outputs a rotational direction drive command current to a motor drive circuit connected to an electric reversible motor to regulate a rotational direction of the electric motor in accordance with the rotational direction drive command current; a drive current detection circuit to detect magnitude and direction of a rotational direction drive current flowing through the motor; and an abnormality determining section that detects a state in which the detected rotational direction drive current indicates a direction opposite to the direction of the rotational direction drive command current and determines whether the state is in excess of a predetermined abnormality determination criterion so as to determine an occurrence of an abnormality of the power-assisted steering system, the abnormality determining section comprising a sensitivity reducing section that lowers a sensitivity of the abnormality determination criterion as an absolute value of the detected rotational direction drive current becomes smaller.