Effective Powertrain Isolation of Off-Highway Vehicles

A Powertrain is one of the major sources of excitation of a vehicle vibration and noise in off highway vehicles. It typically has a significant contribution in whole vehicle NVH characteristics. The structure borne energy of the powertrain is transmitted to the chassis and rest of the vehicle through powertrain mounts. Hence, it is of prime importance to design an effective powertrain mounting system in such a way that it will reduce vehicle vibrations to improve vehicle NVH as well as ride comfort, resulting in an effective vibration isolation system and ensuring long service life. In this paper, a newly developed an analytical tool for effective design of isolation system is discussed. For this model, powertrain is considered as a six degree-of-freedom system. Analytical calculations are implemented to find optimum mount design parameters i.e. stiffness, orientation and position of isolators to meet desired NVH targets. To achieve a good isolation characteristic, there is a necessity of decoupling of rigid body modes using optimization of various decoupling methods, which further helps in reducing the forces transmitted by the powertrain through the mounts. To evaluate coupling between the rigid body modes, modal energy distribution calculated from an analytical tool is used. The results from the developed analytical model are validated using commercially available tools for design of isolation systems.