Vehicle vibration is the key consideration in the early stage of vehicle
development. The most dynamic system in a vehicle is the powertrain system,
which is a source of various frequency vibration inputs to the vehicle. Mostly
for powertrain mounting system design, only the uncoupled powertrain system is
considered. However, in real situations, other subsystems are also attached to
the powertrain unit. Thereby, assuming only the powertrain unit ignores the
dynamic interactions among the powertrain and other systems. To address this
shortcoming, a coupled powertrain and driveline mounting system problem is
formulated and examined. This 16 DOF problem is constructed around a case of a
front engine-based powertrain unit attached to the driveline system, which as an
assembly resting on other systems such as chassis, suspensions, axles, and
tires. First, the effect of a driveline on torque roll axis and other rigid body
modes decoupling is examined analytically in terms of eigensolutions and
frequency responses. It is observed from the analysis that when the optimized
uncoupled powertrain system is introduced in real vehicle conditions, the
vibration isolation level of the powertrain mountings gets degraded. Then, a new
improved approach of considering coupled powertrain and driveline systems in the
initial design phase itself is proposed. The mounting system parameters such as
mount location, mount orientation angle, and stiffness rate are optimized and
redesigned for the proposed system. The results of the redesigned system show
that the decoupling of the rigid body mode parameters is improved and
consequently powertrain vibration performance is also improved in static and
dynamic conditions of the vehicle. Overall, the findings of this study suggest
that considering the driveline along with the powertrain as a coupled system at
the early phase of the mounting system design itself improves the vibration
performance of the vehicle during real-life situations.
