Abstract
Research and/or Engineering Questions/Objective Belt type R-EPS system uses an electric motor to assist the driver of a vehicle and it typically uses belt and pulley assembly for assist-torque amplification. Operating noise and vibration of this system, transferred through surrounding structures and air, can be noticed by driver. The objective of this study is to improve structure NVH level of Belt R-EPS system for making driver to feel more comfort and quiet while driving. Methodology Operation noise and vibration of Belt type R-EPS system is classified into internal and external factors. Internal noise and vibration is generated by mechanical components of REPS system (Actuator ? Belt? Pulley ? Ball-screw ? Rack ? Pinion ? U-joint? Column ? Steering wheel to Driver). External noise and vibration is mainly enhanced by resonance between R-EPS system and sub-frame of vehicle. In order to reduce resonance causing noise and vibration, total NVH mechanism was created about Internal and external noise. NVH analysis procedure (especially related R-EPS system and sub-frame of vehicle) also was established based on NVH-mechanism. Finally our study suggests total optimal design-parameters for reducing NVH of R-EPS system. Results In this paper, optimal analysis test procedure was created to improve structure NVH of belt R-EPS system. NVH optimization of the system is proceeded to achieve natural frequency separation of sub-frame, motor and housing to avoid resonance. The procedure of Optimization analysis test is following: proto-design ? stress and FRF analysis of structural components ? restudy and complementation ? verification. As a result, total system NVH level is improved by more than 3dB. Conclusions Structural NVH analysis is highly demanded as it is directly connected to a driver of vehicle through steering wheel. Understanding total NVH mechanism is prior step to predict future NVH pattern and issues. Structure NVH optimization is applied to the belt R-EPS system in order to design steering gear system with quiet and comfort feeling.