NVH refinement of commercial vehicles is the key attribute for customer
acceptance. Engine and road irregularities are the two major factors responsible
for the same. During powertrain isolators’ design alone, the mass and inertia of
the powertrain are usually considered, but in practical scenarios, a directly
coupled subsystem also disturbs the boundary conditions for design. Due to the
upgradation in emission norms, the exhaust aftertreatment system of modern
automotive vehicles becomes heavier and more complex. This system is further
coupled to the powertrain through a flexible joint or fixed joint, which results
in the disturbance of the performance of the isolators.
Therefore, to address this, the isolators design study is done by considering a
multi-body dynamics model of vehicles with 16 DOF and 22 DOF problems, which is
capable to simulate static and dynamic real-life events of vehicles. Design
indicators are thoroughly analyzed and validated through the rigid body modes
and real field events of the vehicle. As most of the research is done for
four-point mounting powertrain systems by considering 6 DOF or 12 DOF in
commercial vehicles but a novel approach with a 22 DOF model is proposed in this
study to predict the impact of the inclusion of the exhaust aftertreatment
system on torque roll axis and rigid body modes decoupling.
The results of the proposed system show that the rigid body mode decoupling of
the powertrain system improved and consequently the overall NVH performance of
the vehicle in real life is further improved. Therefore, it is suggested from
the study that ignoring the inclusion of the exhaust aftertreatment system in
the powertrain mounting system design reduces the NVH performance of the
vehicle, hence it is recommended to include it in the early phase of design.
