Designs of variable stiffness element for a tunable vibration absorber

T he vibration absorber has been used for vibration control purposes in m an y sectors of engineering from aerospace, to autom otive to civil, for the past 100 years or so. A lim itation of the device, how ever, is that it acts like a notch filter, only being effective over a narrow band of frequencies. R ecent developm ents have overcom e this lim itation by m aking it possible to tune the device over a range of frequencies. T he technical challenge is to design a variable stiffness elem ent that can be adjusted in real-tim e, have a range of stiffness values, is cheap and easy to m anufacture and can respond reasonably quickly to a required change in stiffness from one value to another. In this paper, the w ay in w hich stiffness change can be achieved is review ed, and som e new w ays of achieving a stiffness change are discussed.