Targeted energy transfer in automotive powertrains

Torsional oscillations generated by the internal combustion engine induce various NVH phenomena in the drivetrain system, one being transmission rattle. Palliatives devices such as the clutch predampers or dual mass flywheel have been used to mitigate these NVH phenomena. However, usually these devices are effective over a limited range of frequencies, and not so for broadband transient phenomenon, such as any impulsive actions. This paper considers the Targeted Energy Transfer (TET) method to mitigate torsional vibrations in automotive powertrains. TET is a concept which attempts to direct the mechanical (vibration) energy (in a nearly irreversible manner) from a source (primary system) to a strongly nonlinear attachment (Nonlinear Energy Sink – NES), where it is absorbed, redistributed and/or dissipated. In contrast to the classical powertrain palliative methods, NES should be capable of operating over a broader band of frequencies (with the additional aim of being lightweight and compact). Although the TET concept has been extensively studied for translational systems, there is a dearth of studies for rotational (torsional) ones. In the present work, preliminary parametric studies are performed on a reduced automotive powertrain model, incorporating a NES attachment. The NES parameters, including nonlinear stiffness, viscous linear damping and inertia are varied in order to determine NES effects on engine order (EO) vibration.