The performance of multiple pendulum vibration absorbers applied to rotating systems

A centrifugal pendulum vibration absorber (CPVA) is a device used for reducing torsional vibrations in rotating machinery. It consists of a movable mass, the center of gravity of which is restricted to follow a prescribed path. When this path is properly designed, the motion of the CPVA is tuned so as to generate a torque that reduces torsional vibrations. CPVA's are currently widely employed to suppress torsional vibrations in light aircraft engines, and are receiving attention in experimental automotive studies.;This study starts with an overview of the operation of CPVA's and a description of some existing CPVA designs. A mathematical model is then derived that captures the nonlinear dynamics of a multi-absorber/rotor system response. Using a generic methodology which combines asymptotic techniques (averaging) and bifurcation theory, the mathematical model is analyzed for two representative absorber systems: tautochronic and subharmonic. Analysis is first conducted for the tautochronic system, which enables one to: (1) predict the instability/bifurcation point of the unison motion, (2) investigate the dependence of the post-critical dynamics on various system parameters, and (3) assess the absorber performance in terms of two quantitative measures: the rotor acceleration and the feasible range of the applied torque. A similar analysis is carried out for the system comprised of multiple pairs of subharmonic absorbers. In addition, uncertainties and intentional mistuning are incorporated into the absorber path configurations, which permits one to consider design robustness issues. It is found that the system dynamics and absorber performance measures are accurately predicted by the analyses, as verified by extensive numerical simulations for both absorber systems. Based on these predictions, design guidelines are distilled for various system parameters, including absorber damping, the number of absorbers, and intentional mistuning of the path.;Existing CPVA designs are based on several assumptions, including the following two: First, for a multiple-absorber system, the set of identical absorbers moves in unison, and, second, the absorber paths are manufactured exactly as designed. The present study aims to re-assess absorber performance in terms of relaxing these two assumptions. This necessitates consideration of the nonlinear dynamics of multiple-CPVA systems.