Design of an adaptive dynamic vibration absorber

The aim of this thesis is to investigate the use of a Dynamic Vibration Absorber to control vibration \nin a beam. Traditional means of vibration control have involved the use of passive and more \nrecently, active methods. This study is different in that it involves an adaptive component in the \ndesign of vibration absorber using two novel designs for the adaptive mechanism. \nThe first design incorporates the use of an enclosed air volume to provide the variable stiffness \ncomponent in the absorber. By adjusting the volume of compressible air within the absorber, the \nstiffness characteristics of the absorber can be altered, enabling the device to adapt to changing \nvibration frequencies. Work here includes a theoretical investigation of the device. Following this, \ntwo prototypes are constructed and tested, the second of which is the refined model used for further \ntesting. \nThe second design incorporates the use of two concentrated masses cantilevered from two rods. The \nadaptive solution is achieved by moving the two masses along the length of the rod, producing a \nchanging natural frequency for the absorber device. An analytical model of this device is developed \nas well as a finite element model. Results from both are compared to those obtained experimentally. \nFinally, a tuning algorithm is derived for the second absorber, and a control system constructed to \nmake the dynamic vibration absorber "adaptive". Experiments are undertaken to determine the \neffectiveness of the absorber on the beam subject to changing excitation frequencies. The outcome \nof this research is that an Adaptive Vibration Absorber has been constructed with a computer \ninterface such that the device can be used "on line".