| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an electric power steering device which determines that a steering mechanism reaches a steering limit (end contact) based on the change rate of a current command value or a phase advance value and restricts the drive force of an electric motor which supplies a steering assist force to reduce the impact produced upon the end contact. <P>SOLUTION: A current command value Iref calculated based on a steering torque T and a vehicle speed V is output to a motor control section 20, and the duty ratio D of a pulse width modulation signal driving the electric motor 30 is calculated. A current command value change rate calculation section 25 calculates a derivative value indicating the change rate of the current command value Iref, and the derivative value is compared with the threshold of a threshold memory 26b. When the derivative value does not exceed the threshold, the calculated duty ratio DVN is selected, and when exceeds the threshold, a limit duty ratio DVL is selected, and the electric motor 30 is driven through an inverter 24. A current command value only the phase of which is advanced by means of a filter can be compared with the threshold, and duty ratios DVN, DVL can be selected as in the same manner above. <P>COPYRIGHT: (C)2013,JPO&INPIT |
