The dynamic response of multiple pairs of subharmonic torsional vibration absorbers

Recent studies have demonstrated an arrangement of centrifugal pendulum vib ration absorbers that is very effective at reducing torsional vibrations in rotating machinery. The basic system is composed of a pair of identical ab sorbers that are tuned to a one-half subharmonic order relative to the appl ied fluctuating torque. These absorbers, when moving in an out-of-phase man ner along a particular path relative to the rotor, are capable of significa ntly reducing torsional vibrations of a desired order. In this paper, we co nsider the response of systems composed of multiple pairs of these absorber s, with the goal of determining the dynamic stability of the desired respon se and the effects of small imperfections in the absorbers' paths. The desi red response of this system is one in which the N absorbers (N even) act as a single pair, with two groups of N/2 each moving with equal amplitudes bu t exactly out of phase with respect to one another. It is shown that this r esponse can be made to be dynamically stable and robust to certain model un certainties by a slight, identical overtuning of each absorber. The analyti cal results, obtained by the method of averaging and symmetric bifurcation theory, are confirmed by simulations for the cases with two and three pairs of absorbers. (C) 2000 Academic Press.