Study Of Dynamic Vibration Absorber Based On Variable Mass And Its Control Strategy

The adaptive dynamic vibration absorber (ADVA) has been an important research fieldin vibration control. The ADVA can track the external excitation frequency and reduce thevibration of the primary system over a wider band by changing its parameters (and thennatural frequency), hence, it can address the disadvantage of narrow band of the traditionalDVA. Different from the usual ADVA at present, whose natural frequency is modified bychanging its stiffness, a novel absorber based on variable mass (VM) is proposed in this thesis.The VM ADVA can be obtained by introducing a liquid box into the common absorber.When the liquid volume in the box changes, the mass and the natural frequency of theabsorber will be modified as well, consequently, a wideband absorber will be achieved.The main work of this thesis is as follows:(1) Based on the vibration theory of two degrees of freedom system, the principle of thetraditional DVA is studied, including fixed-point design theory and DVA parameteroptimization theory. The influence of the absorber parameters on vibration reductionperformance is investigated as well through simulation.(2) The VM ADVA design is proposed, and the motion differential equation of theprimary system-absorber is established. Then, the simulation model in Simulink environmentis built according to the motion differential equation, and the performance of the VM ADVAon vibration reduction are investigated. Meanwhile, the effective bandwidth of the absorber isanalyzed.(3) An experimental system was built to test the performance of the VM ADVA. A glassbottle is applied as the variable mass element of the absorber. The mass of the absorber isadjusted by changing the water line in the bottle, so as to track the excitation frequency. Theexperimental results show that the VM absorber can suppress the vibration of the primarysystem about14dB across the frequency range from8.125Hz to9.297Hz when its masschanges. It demonstrates that the proposed absorber has a wider bandwidth comparing withthe traditional DVA.(4) A control strategy based on VM ADVA is proposed to solve the problem that it canincrease the vibration of the primary system as a new resonance peak is introduced into thefrequency response of the primary system when a DVA is applied. Some simulation and experiments are conducted to study the effectiveness of the control plan. The results show thatwhen the new control plan is used, the VM ADVA can not only substantially reduce thevibration of the primary system over a wider band, but also avoid the resonance of theprimary system caused by the application of the absorber. Therefore, the proposed controlstrategy is valuable in practical engineering applications of vibration control.