Estimation of rattle noise from an electric power steering system

This study proposes a methodology for estimating rattle noise from electric power steering systems (EPS) under vehicle-running condition by virtually installing EPS to vehicles. In this methodology, blocked forces of an EPS under the operational condition and vibro-acoustic transfer functions of a vehicle are required. The formers were indirectly determined by applying the in-situ blocked force approach to a component test, in which rattle impacts inside an EPS under vehicle running condition was reproduced, and the latters were measured by hammering connections of an EPS on a vehicle under static condition. Target microphone for the vibro-acoustic transfer functions is set up at the center of steering wheel without its airbag module, because it is possible to extract rattle noise component of an EPS with a band pass filter from the sound measured with the microphone under vehicle running condition. The proposed methodology was verified by comparing the estimated and measured rattle noises from an EPS under vehicle-running condition.