Patent ID: 6995567

Claim:
A failure detection system for an electric power steering system, comprising: a bridge circuit that is disposed between a battery and a steering motor and drives the motor in forward and reverse direction; an actual current detection means for detecting the actual current supplied from the battery to the motor via the bridge circuit; a control means for carrying out feedback control so that the actual current coincides with a target current; wherein the bridge circuit comprising: a high voltage terminal connected to a positive pole of the battery; a low voltage terminal connected to a negative pole of the battery; first and second output terminals connected to the motor; a first switching element providing a connection between the low voltage terminal and the first output terminal; a second switching element providing a connection between the low voltage terminal and the second output terminal; a third switching element providing a connection between the high voltage terminal and the first output terminal; and a fourth switching element providing a connection between the high voltage terminal and the second output terminal; wherein the control means determines that there is an ON failure among the first to the fourth switching elements based on a first cumulative time for which the actual current is equal to or greater than an upper limit value until a timer has timed up and a second cumulative time for which the actual current is equal to or less than a lower limit value until the timer has timed up.