Controller is designed to control operation of a rear-wheel steering
apparatus typically provided in a four-wheel steering vehicle, and is
based on electronic circuitry. In the electronic circuitry, a
target-steering-angle setting section sets a target steering angle of the
rear wheels. Actual-steering-angle measurement section measures an actual
steering angle of the rear wheels. On the basis of the target steering
angle and actual steering angle, a steering-angle adjustment section
generates a motor drive signal to control the rotation of the motor in
such a manner that a difference or offset between the target steering
angle and the actual steering angle becomes zero. On condition that the
motor is in a predetermined driving state, a motor-deceleration-amount
calculation section is activated to calculate an actual rotating speed of
the motor on the basis of the actual steering angle of the rear wheels and
compares the calculated actual rotating speed of the motor with a
prestored reference rotation speed. The motor-deceleration-amount
calculation section operates to calculate a motor-rotation deceleration
amount when the compared result indicates that the calculated actual
rotating speed is higher than the reference rotation speed.