Study On Behavior Of Two-layer Fluid-type Floating Vibration Isolation System

The vibration isolation or control is important to improve the bahavior of modernmachine. Traditional linear vibration isolator is difficult to isolate low frequency orbroadband vibration. In order to isolate low frequency vibration with multi-frequencycomponents, a two-layer fluid-type floating vibration isolation system was presentedin this paper based on anti-resonance mechanism, which use inertial force induced byadded mass of flowing fluid to cancel the spring force.The structure of the two-layer fluid-type floating vibration isolation system weredescriped and the mathematical model of it was derived. The mathematical model wassimplified to linear equations. The vibration response and force transmissbility wereobtained. The expression of force transmissbility was analyzed to explain theisolation mechanism. It is indicated that the system can perform vibration isolationsuperbly at very low frequencies due to the added mass can be adjusted to very large.It is also feasible to tune the anti-frequencies in real-time to adapt to the change ofexcitation frequency.The design variables of the vibration isolation system were optimized based ontheoretical analysis. The isolation behavior of two-layer fluid-type floating vibrationisolation system was compared with single-layer fluid-type floating vibrationisolation system, it was found that two-layer fluid-type floating vibration isolationsystem exhibits better vibration isolation behavior.The nonlinear behaviors of the vibration isolation system were analyzed byperturbation method. The numerical computational method was used to simulate thevibration responses of the system under excitations with single-frequency anddouble-frequencies. The perturbation method revealed that the mean position of thefloating body and fluid container will drift downward under exciation and higherorder harmonic vibration can be observed, which was verified by the numericalsimulation.A prototype of two-layer fluid-type floating vibration isolation system wasdesigned and built to verify the theoretical model. Experimental tests were carried outfor a series of excitation frequency. The force transmissbility obtained by experimentwas compared with that obtained by theory.It is showed that the trend of experimentaldata agree with the theoretical ones.