THE EFFECTS OF IMPERFECTIONS ON THE PERFORMANCE OF THE SUBHARMONIC VIBRATION ABSORBER SYSTEM

A recent study has demonstrated a new configuration of centrifugal pen dulum vibration absorbers (CPVAs) that is very effective at reducing t orsional vibration levels in rotating systems that are subjected to ha rmonic external torques. This system is composed of a pair of absorber masses riding on epicycloidal paths that are tuned to one-half order relative to the frequency of the applied torque. In the desired respon se, the two absorbers move in direct opposition to one another in a se cond-order subharmonic manner. The basic analysis of this subharmonic vibration absorber system assumes that the paths for the absorber mass es can be perfectly manufactured and are exactly tuned as desired. The primary goal of this study is to explore the effects that imperfectio ns and intentional mistuning of the absorber paths have on performance of the system. The results obtained allow one to select certain featu res of the path in order to achieve the desired performance, even in t he face of uncertainties. To this aim, the equations of motion are fir st derived for a simplified model, consisting of two absorber masses a nd a rigid rotor. This system is shown to possess a one-to-one interna l resonance subjected to two-to-one resonant external excitation. By m aking use of some scaling assumptions on the system parameters, the me thod of averaging is applied in order to obtain approximate solutions of the equations of motion. These are used to evaluate the absorber pe rformance in terms of two performance measures: the magnitude of the r otor acceleration and the range of the disturbing torque over which th e absorbers operate effectively. The results obtained are distilled in to design guidelines in terms of how one should choose certain mistuni ng parameters for the absorber paths in order to achieve satisfactory system performance. In summary, it is determined that one should keep the two absorber paths as identical as possible, but that a small leve l of identical overtuning in each path will provide a certain level of robustness. In addition, it is also shown that this mistuning can be used to adjust a tradeoff between torsional vibration levels and the o perating torque range for the system. (C) 1998 Academic Press.