| 摘要 |
PROBLEM TO BE SOLVED: To determine, when a failure is generated in a motor driving system of an electric power steering device, whether or not the failure is fatal, and to quickly start an appropriate process with respect to the failure for ensuring a safety depending on a determined result. SOLUTION: The failure in a motor driving part 20 is detected based on a detected current difference|Ia-Ib|which is a difference between an inflow current Ia and an outflow current Ib of a motor driving circuit 30 detected by an inflow current detection circuit 23 and an outflow current detection circuit 26. When the failure is detected, determination is performed whether or not the failure is fatal based on a difference|VDsum-VEsum|between a detected motor terminal voltage sum VDsum and an estimated motor terminal voltage sum VEsum, thereby selecting the appropriate process for the failure depending on the determined result. Here, the VDsum is a sum of positive and negative terminal voltages Vm+ and Vm- detected in positive and negative terminal voltage detection circuits 24 and 25, and VEsum is calculated by a power supply voltage VB detected in a power supply voltage detection circuit 22 and a duty ratio of an input signal to the motor driving circuit 30. |
