A Study on the Noise Reduction of Electrical Power Steering in Surface Permanent Magnet Synchronous Motor

Electrical Power Steering (EPS) is designed to use an electric motor to reduce effort by providing steering assist to the driver. EPS have advantages which are economical and eco-friendly compare with hydraulic power steering, because the power steering oil is not used and efficiency of vehicle increased to 3~5 %. Since EPS is connected to handle of vehicle, acoustic noise and vibration have an effect on the driver directly. So study on the acoustic noise and vibration reduction of EPS is proceeding. In this paper, acoustic noise and vibration reduction of motor are generated by electro-magnetic exciting forces between stator and rotor. The magnetic noise is defined as noise generated from vibrations due to electro-magnetic exciting force. The electro-magnetic exciting force affect on stator yoke, and the acoustic noise and vibration of motor generated by deformation of stator yoke. In order to consider mechanical characteristic, the natural frequency mode of stator is calculated using FEA to avoid resonance. In order to verify proposed method, the proto and improved model are manufactured and experimented.