Controller and control method for an electric power steering apparatus

摘要

A controller controls an electric motor to provide assist power corresponding to steering operation for an electric power steering apparatus. The controller comprises a detecting device, a filtering device, a judging device and a determining device. The detecting device detects present voltage of a power source for the electric motor. The filtering device filters the present voltage based on a small time-constant when the voltage of the power source increases and based on a large time-constant when the voltage of the power source decreases. The judging device judges whether the filtered voltage is lower than a predetermined threshold. And, the determining device determines being abnormality of the power source when it is judged that the filtered voltage is lower than the threshold.