Response Sensitivity of Centrifugal Pendulum Vibration Absorbers to Symmetry-Breaking Absorber Imperfections

This paper details an analytical investigation on free and forced vibration response sensitivity of centrifugal pendulum vibration absorbers (CPVA) to symmetry-breaking absorber imperfections. Minor variations in the absorbers' design due to manufacturing tolerances, errors as well as operational wear and tear tend to break cyclic-symmetry and lead to asynchronous absorber oscillations, unbalanced rotor translations and thus significant vibration amplification. Therefore, an in-depth understanding on the sensitivity of CPVA's vibration response to absorber imperfections is needed to devise an improved absorber tuning strategy for robust vibration and noise reduction from realistic vehicle transmissions and drivelines. In this paper, free and forced vibration response sensitivity of generalized CPVA systems are analytically derived for absorber spacing and mass variations using the perturbation-based eigensensitivity technique in conjunction with modal superposition. The methodology applied in this study is realized through a linearized planar dynamic model, which includes both torsional and translational motions of the rotor along with oscillations of N equally-spaced baseline identical absorbers. Distinct mode distortions and degenerate mode splitting from the known baseline modal structure (with translational, rotational and absorber modes) are investigated for systems with asymmetric absorber spacing and absorber mass variations. The baseline modal structure is modified differently due to having unequal absorber masses or absorber spacing errors, and these differences are analytically derived and demonstrated. Moreover, it was identified that CPVA systems do not exhibit mode splitting with the absorber mass and spacing deviations. Response alterations and localized response patterns due to asymmetric absorber spacing and mass variations are identified and visualized through a case study. Results define a new parametric lower limit for the overtuning of absorbers to avoid localized absorber response and vibration amplification due to absorber imperfections. Additionally, the outcomes are used to locate unique excitation orders, which would help distinguish the alterations in system response due to absorber spacing and mass from each other and serve as a diagnostic tool.

Automated summary

This paper presents an analytical investigation on the sensitivity of centrifugal pendulum vibration absorbers (CPVA) to symmetry-breaking absorber imperfections. It provides an improved absorber tuning strategy for robust vibration and noise reduction in realistic vehicle transmissions and drivelines. The study derives the free and forced vibration response sensitivity of generalized CPVA systems for absorber spacing and mass variations using a perturbation-based eigensensitivity technique. The linearized planar dynamic model used includes torsional and translational motions of the rotor along with oscillations of baseline identical absorbers. Results highlight the response alterations and localized response patterns due to asymmetric absorber spacing and mass variations, and propose a new parametric lower limit for the overtuning of absorbers.