Optimization of an engine mounting system with consideration of frequency-dependent stiffness and loss factor

Abstract

An engine mounting system is the primary vibration isolator of the engine from the chassis. The frequency-dependent stiffness and loss factor present a more accurate representation of a rubber mount as opposed to the frequency-independent damping model. In this article, dynamic optimization of an engine mounting system considering the frequency-dependent stiffness and loss factor is presented. The dynamic properties in all three principal directions are measured on the basis of the optimum locations and orientation angles of the individual engine mounts, which are identified to minimize the mean force transmissibility of the system for a range of frequencies, resulting in a 45% reduction in the vertical transmissibility to the installation base. In comparison, optimization based on a frequency-independent stiffness underestimated the peak transmissibility, and minimization of the vertical force transmissibility created a significant increase in other directions. The optimum parameters are applied to a small utility two-stroke engine. A significant reduction in the transmitted force and engine displacement is demonstrated.