Control apparatus for controlling an electric power steering mechanism

A control apparatus for controlling an electric power steering mechanism comprising:

• a torque sensor mounted on a steering shaft for detecting a steering torque signal;
• an indicating value calculating unit for calculating a motor current indicating value based on the steering torque signal detected by the torque sensor and a vehicle speed detected by a vehicle speed sensor;
• an electric motor for providing a steering assist force to the steering shaft;
• a motor current detecting unit for detecting a motor current flowing in the electric motor;
• a motor drive circuit for driving the electric motor;
• a drive signal calculating circuit for calculating a drive signal from current deviation between the motor current indicating value and the motor current detected value, and transferring the drive signal to the motor drive circuit;
• an abnormal state detecting unit for detecting whether the electric power steering mechanism is in an abnormal state or a normal state for each of a plurality of sampling times, wherein a count value of an abnormality counter is incremented at every detection of the abnormal state that is detected by the abnormal state detecting unit;
• and
• a failure deciding unit for detecting failure of the electric power steering mechanism when the abnormality counter reaches a failure deciding value, wherein the failure deciding unit returns the count value of the abnormality counter to zero when the abnormal state detecting unit sequentially detects normality during a predetermined number of the sampling times, even if the abnormal state detecting unit once detects abnormality.