With growing demands for better fuel economy and reduced carbon emissions there is a need for smaller and more fuel efficient engines. At the same time, to improve passenger comfort there are also demands placed on improved vehicle quietness [1]. A Homogeneous Charge Compression Ignition (HCCI) system or a higher compression ratio system can be used to obtain better fuel economy but the enhanced combustion rate causes an increase in engine vibration in the medium to high frequency range [2, 3]. To ensure vehicle quietness, this issue of structure-borne noise that is transmitted from the engine mounts to the body must be addressed.
In this paper a simple anti-vibration active mount system is introduced that can significantly reduce structure-borne noise at medium to high frequencies. This is achieved by adding mass to the insulator which leads to resonance at lower frequencies, in order to obtain double anti-vibration performance. This works to significantly reduce the transmission of approximately 300Hz to 1000Hz noise to the body. To suppress the increased vibration due to resonance of added mass, a control force which is proportional to the vibration velocity is applied. Additionally, an equation is developed for reducing force transmitted in directions other than direction of principal force. The resulting active double anti-vibration engine mount system can be used with fuel efficient engines to ensure improved vehicle quietness.
