Analysis And Experimental Research On Control Of Complex Passive-active Vibration Isolation System

Theoriotical analysis and experiments were carried out to study isolation design and active control for complex isolation system. After building the model of one-stage-multi-mount passive isolation system with flexible foundation under complex excititation, the equation of vibration transfermission was derived. A two-stage isolation model with flexibility of intermediate structure taken into account was established to study the influence of intermediate structure’s vibration on vibration isolation performance. The distributed parameters of isolator were considerd to study isolation system with intermediate-mass. Dynamic equations of isolation system with intermediate-mass were derived by transfer matrix method to study characteristics of system. The response of isolation system with intermediate-mass forced by complicate excitation was studied and active control equation with constraints of the system was derived. An experiment model was built to test power flow, accelation transmissibility and mobility of the isolation system and to carry out experimental modal test.Passive isolation model of one-stage-multi-mount isolation system with flexible foundation forced by complex excititation was built and the dynamic equation of system was derived by mobility method to analyze response to complicate excitrration. Finite element method (FEM) was taken to study the modal characteristics of system. It is shown that resonance of rigid modal causes isolation effect decrease in low frequency domain and flexibile vibration of foundation cause isolation effect decrease in high frequency domain. Power flow caused by vertical vibration of foundation is higher than others and is the main energy that causes structure-borne sound.A two-stage isolation system with flexibility of intermediate structure taken into account was built. Using mobility/impedence method to derive equation of system forced by single vertical excitation to analize the influence of structure’s flexible vibration on power flow transmission. The coupling between intermediate structure and foundation was studied. FEM validation was taken to study the modal characterics of system. It is shown that flexible vibration of intermediate structure causes transmission of energy to increase in high frequency. Coupling among flexible vibration of intermediate structure, foundation and standing wave effet of isolator make isolation effect decrease in high frequncey domain. Asymmetric arrangement of isolators and machine causes isolation effect to decerease.Considering distributed parameter of isolator, equation of multi-mount isolation system on flexible foundation with intermediate-mass was studied whose equation was derived by transmission matrix method to analyse the improvement on standing wave effect. Active isolation of isolation system with intermediate-mass forced by complex excitation was built and its equations were derived with output constraints. Strategies including minimization of total power flow into foundation, minimization of vertical velocity of intermediate mass, minimization of vertical force on intermediate mass were studied. Influence of output constraints on active control performance was discussed. It is shown that intermediate-mass can depress standing wave effect in isolator and reduce the vibration energy into foundation. The heavier intermediate-mass is, the better isolation. Symmetric arrangement of different mass causes more rigid modals in low frequency domain. On the contrary, unsymmetric arrangement will excite more elastic modals of foundation causing isolation effect to decrease in the end. Active isolation without constrants can improve isolation effect greatly, especially in low frequency domain, but it is too difficult to sasify the need for performance of actuator. Constrants can reduce the need for actuator and get a better isolation effect than passive isolation system.One-stage isolation systems were built to carry out power flow test and experimental modal test. The results of power flow test are consistent with theoriotical analysis. Mobility curves of isolation on plate are consistent with theoriotical calculation. Accelation transmissibility was tested. Modal characteristics were studied through experimental modal test which were compared with theoriotical calculation and FEM validation results.