A vehicle steering control system is provided which is capable of reliably protecting
a motor for driving a wheel steering shaft. In the system, a current sensor and
a motor rotational speed detection section respectively detect a current applied
to the steering shaft drive motor and the motor rotational speed of the steering
shaft drive motor, and current inference means infers the motor current applied
to the steering shaft drive motor based on the detected motor rotational speed.
Abnormal judgment means compares the current inference value obtained by the current
inference means with a current detection value indicated by the current sensor
to judge whether the current sensor is normal or not. Abnormal judgment output
means outputs the result of the abnormal judgment when the current sensor is judged
to be abnormal. When a trouble occurs that the current sensor fails to operate
normally due to the malfunction or the like, such a trouble can be recognized at
the early stage of the malfunction. Therefore, it can be successfully obviated
that the current sensor has fallen in the malfunction, nevertheless the operation
of the motor is continued as usual.
