Damping effects introduced by a nonlinear vibration absorber in automotive drivelines at idle engine speeds

Legislation on vehicle emissions and the requirements for fuel efficiency are currently the key development driving factors in the automotive industry. Research activities to comply with these targets point to engine downsizing and new boosting technologies, which have adverse effects on the NVH performance, durability and component life. As a consequence of engine downsizing, substantial torsional oscillations are generated due to high combustion pressures. Meanwhile, to attenuate torsional vibrations, the manufacturers have implemented absorbers that are tuned to certain frequency ranges, including clutch dampers, Dual Mass Flywheel (DMF) and centrifugal pendulum dampers. These devices add mass/inertia to the system, potentially introducing negative effects on other vehicle attributes, such as weight, driving performance and gear shiftability. This paper provides a study of torsional damping effects of nonlinear vibration absorbers on drivetrain NVH refinement by attenuating torsional oscillations at the idling engine speeds. The nonlinear absorber concept presented operates on the principle of Targeted Energy Transfer (TET), whereby the energy excess (vibration) from a donor (primary powertrain system) is transferred to a receiver (nonlinear absorber) in a nearly irreversible manner. Thereafter, the received energy can be absorbed, dissipated, or redistributed. This potentially allows the absorber to operate over a broadband frequency range, whilst being light and compact, which is ideal for automotive powertrains. In the present work, simulations are performed using an automotive drivetrain (subsystem) model with a nonlinear absorber. The damping content of the absorber is varied to study its effect on the attenuation of torsional oscillations.