Development of a Centrifugal Pendulum Absorber for Reducing Ship Superstructure Vibration

Abstract

A vibration absorber (designated as the Super Dynamic Damper) for installation on ship superstructures, based on a tuned centrifugal pendulum concept, was developed through theoretical analyses followed by tests on units mounted on a vibrating platform and on actual ships. The tests confirmed the analytically estimated performance, and demonstrated that the vibrating amplitude would be reduced, to limit it to a constant low level independent of imparted exciting force. Results of analysis indicate the most important quality demanded of a tuned absorber to be the tuning accuracy. The tolerance permissible for the tuning accuracy is determined by the mass ratio: A smaller mass ratio calls for correspondingly higher tuning accuracy. The centrifugal pendulums are governed by Coulomb damping, which results in a damping behavior distinct from normal viscous damping. Both analysis and measurements attested to the importance of accurately controlling the absorber rotating speed, short of which the absorber risked becoming a vibration amplifier.