Self-check method of four-wheel steering drive system

Claim 1

A self-check method of a four-wheel steering drive system for a vehicle, which comprises a rear-wheel steering mechanism for steering rear wheels, a steering motor for driving said rear-wheel steering mechanism, an H bridge circuit, consisting of four switching elements, for driving said steering motor in a forward or reverse direction to turn said rear wheels to the left or right, and a relay for turning on/off a battery power supply with respect to said H bridge circuit, comprising the steps of, when an engine of the vehicle is in an idling state before starting traveling: (1) checking a relay downstream current upon ON/OFF of said relay to check a state of said relay; (2) supplying forward and reverse rotation control signals of a duty ratio of 0% to a predetermined combination of said switching elements constituting said H bridge circuit to check if a current obtained from said predetermined combination of switching elements is an overcurrent, thereby checking a state of said H bridge circuit; and (3) when the rear wheels are turned to a target rear wheel position with reference to a present rear-wheel position, checking whether or not a difference between the target rear-wheel position and an actual rear-wheel position is set to be not more than a predetermined value within a predetermined period of time, thereby checking a state of said steering motor and said rear-wheel steering mechanism.