Passive Pendulum Balancer for Rotor Systems

Abstract

Automatic, passive self-balancing systems are important tools for reducing the effects of synchronous vibration in a variety of rotating machinery. Such systems are ideally capable of precise balancing, subject to certain dynamic restrictions. There are a number of designs that are used, but the most common type is the ball balancer system that employs balls that move inside a cylindrical race or channel. However, such systems may be subject to a variety of effects that arise due to rolling resistance. An alternative approach uses pendulums rather than balls to provide the balancing. In the present work, a passive pendulum balancer system is investigated from several aspects. A mathematical model has been developed to discover the stability characteristic of the pendulum balancer. Because of the obvious potential for practical application pendulum balancers this system was investigated from engineering point of view. These investigations tried to cover all the possible differences that could arise when the mathematical model would be materialized as a real passive balancing device. The application of non identical pendulums was studied in detail and its advantages and disadvantages are discussed. The influences of rolling resistance and shaft misalignment on the functional capability of pendulum self-balancing systems are specifically examined. The study of a passive pendulum balancer with non-isotropic suspension is also presented. The existence of two natural frequencies results in two distinct areas of stability. These stable areas are determined by Floquet analysis and verified by numerical simulations and experimental measurements.