A novel nonlinear variable damping device and its application for the systems with uncertain parameters

This paper deals with the performance of a novel nonlinear viscous dashpot with variable damping. The new proposed dashpot can be utilized in devices for instance dynamic vibration absorbers (DVAs). When the vibration absorber is tuned to the bridge's fundamental frequency, it represents a robust effect in controlling the vibrations of the bridge; however, a DVA is very sensitive to frequency detuning. The proposed nonlinear dashpot can be applied in a passive vibration absorber and upgrades it to a nonlinear variable damping one. Since the parameter of such DVA can be adjusted, it is the so-called nonlinear adjustable DVA. The mentioned dashpot, provides a quadratic nonlinearity for the damping element. The proposed dashpot in this study possesses a simple mechanism, which can handle large range of flow rates of fluid, smoothly without turbulence, in the oil channel. To investigate the effectiveness of an adjustable vibration absorber, a semi-active DVA with variable damping, and stiffness elements is applied on a footbridge; where, the footbridge is experienced variations of the fundamental frequency over time, and is subjected to a walking pedestrian. For the case study in the present study, a vibration reduction of 31% in comparison with the attached traditional passive DVA with constant parameters was achieved. The results show that, by using the proposed nonlinear dashpot, presented in this study, into an attached DVA, the footbridge will experience about 10% more deflection reduction concerning a classical linear DVA.