Study of two different tunable vibration absorbers: Variable stiffness absorber and variable damping absorber

In this thesis, two different tunable vibration absorbers are studied.;The developed variable stiffness absorber is a cantilever-beam attached by a mass at its free end. The absorber stiffness is varied by changing the beam length through a DC motor drive system. Various models of the beam-absorber system are derived. The proposed tuning algorithm is based on the frequency information extracted from spectrum of the response. Using a simplified 2-degree-of-freedom (DOF) model, the computer simulation tests the tuning algorithm's ability to track a step change and a linear change in the exciting frequency. Factors affecting the performance of the absorber are investigated. The developed variable damping absorber is an electromagnetic damper that is based on the eddy current principle. Analytical study shows that there exist two crossing frequencies which determine whether damping should or should not be added to the absorber system. An on/off tuning control strategy is developed. Using a 2-DOF system, the computer simulation tests the tuning strategy when the exciting frequency experiences a multi-step change. For both the absorber systems, the experiment study focuses on validation of the tuning algorithms and addresses some practical issues encountered in implementation. (Abstract shortened by UMI.).