Method for Adjusting Torsional Natural Frequencies of Powertrains with Novel Coupling Design

Torsional vibrations are inherently present in every rotating powertrain. In resonant conditions, torsional vibrations can be significantly amplified. A typical method to reduce the torsional vibration particularly at resonance is to modify the torsional natural frequencies with the component design. Commonly, a straightforward method for the modification is the adjustment of the torsional stiffness of a coupling. This study presents a method to modify the torsional natural frequencies using a coupling design with continuously adjustable torsional stiffness. The presented coupling design is investigated with torsional analysis and experimental measurements. Torsional analysis was utilized to predict the effects of varying the coupling stiffness to the torsional natural frequencies of a powertrain. The experimental measurements were conducted by attaching the adjustable stiffness coupling to the powertrain and measuring the change in the torsional natural frequencies while the torsional stiffness of the coupling was adjusted. The torsional natural frequencies were determined from the measurements by identifying the resonance induced torsional vibrations from the vibration response of the powertrain. The torsional vibrations were excited to the system by a load motor. The measurements showed that the first torsional natural frequency of the powertrain changed from 15.6 Hz to 43.0 Hz as the torsional stiffness of the coupling was adjusted. The results of the torsional analysis and the experimental measurements were compared to determine the performance of the realized coupling. The results indicated that the torsional natural frequencies determined by torsional analysis agree well with the experimentally measured results. The prediction errors were generally below ±5%, which is typically considered as a margin for accurate torsional analysis.