Dynamic Stability and the Performance of Nonlinear Torsional Vibration Absorbers

Professor Steven Shaw, Department of Mechanical Engineering , Michigan State University

Centrifugal pendulum vibration absorbers are used to attenuate torsional vibrations in rotating machinery. They consist of a set of masses that are mechanically suspended from a rotating shaft and are free to move relative to it in a plane perpendicular to the axis of rotation. The paths along which these masses move are designed so that their motions dynamically cancel the effects of fluctuating torques applied to the rotor, thereby reducing vibration levels. These absorbers are linearly tuned to the frequency of the applied torque, and they operate most effectively when lightly damped. Also, due to balancing and space limitations, these systems are generally composed of several identical absorbers that are weakly coupled to one another through the (relatively large) inertia of the rotor. These features - a lightly damped system with a high level of symmetry, driven by resonant excitation - set the stage for a variety of nonlinear interactions, most of which are undesirable in terms of the effectiveness of the absorbers. This presentation will describe two approaches to the design of absorber paths for enhanced performance at large amplitudes. The first is to develop paths that avoid the performance-limiting instabilities and bifurcations that arise from the symmetry of the system. This extends the torque operating range, but does so at the expense of vibration amplitudes. The second approach utilizes a novel subharmonic tuning for the absorbers that offers excellent performance over a wide operating range. Some preliminary experimental results that demonstrate general features of these absorbers will also be presented.