Active Vibration Control of Motor Driven Power Steering for Reduction of Interior Noise

This study presents a novel active vibration control (AVC) system on motor driven power steering (MDPS) to reduce interior noise reduction caused by operating the MDPS in an electric vehicle. MDPS is electronic power steering (EPS). The MDPS attached to the rack gear of power steering system is called R-MDPS. Operating of the R-MDPS generates a structural vibration of R-MDPS, and the vibration is transmitted to car body through mounts of car subframe. The vibrating body of car becomes a monopole and dipole sources of vibroacoustic noise generated inside car. This vibracoustic noise is a structure borne noise and makes passenger annoyance. To reduce interior noise inside a car directly, active noise control (ANC) has been used as active method and is a useful method for active cancellation of the low frequency noises less than 400Hz. However, in this study, because the frequency range of interior noise due to operation of R-MDPS is higher than 400Hz, the AVC system is employed and is applied to active cancellation of the vibration transmitted to car body through the subframe mounts. For application of AVC to test car, the control force is required and the actuator for generation of control force should be install on the mounts. For application of AVC to test car, the control force is required and the actuator for generation of control force should be inserted in the mount between subframe and R-MDPS. It requires an extra rework of test car. In this study to study the feasibility for the application of AVC system to R-MDPS, the test jig, which composes of R-MDPS and subframe of test car, is made and is set up in the laboratory. All study on AVC is performed in the laboratory. The proposed method is successfully applied to the active cancellation of vibration at target point of subframe. The developed method is going to be applied to the AVC of real test vehicle.