Study Of Active Isolation On A Elastic Foundation

The problem of ship structural vibrations caused by marine powermechanical vibration is always one of the main research directions ofengineering circles. It is difficult to satisfy the strict requirements in vibrationisolation based on the traditional hypothesis of rigid foundation, because of therather strong coupling effect between machinery and flexible foundation.Aiming at the existing problems of active vibration isolation on the flexiblefoundation, a large flexible vibration isolation structure is presented in this thesis,in order to verify the feasibility of control strategy of active vibration isolationon the flexible foundation with simulation technology and experimental method.The large flexible vibration isolation structure presented in this thesis isdivided into five flexible parts: the upper mass, the upper mounting system, theflexible base, the lower vibration isolating structure and the hydraulic system.The finite element analysis model is set up firstly, and the model is modifiedcontinuously in order to its vibration characteristics more close to the actualstructural by comparing the results of experiment and theoretical calculation. The simulation models of single-input and single-output, multi-input andmulti-output based on the Simulink module of MATLAB and the transferfunctions of primary paths and error paths obtained through finite elementcalculation is established, and the simulation results is analyzed secondly.Finally off-line error path identification is selected for the modeling of errorpaths, and the experiments based on the filtered x-LMS algorithm areimplemented on the system. The results of simulation and experiment show thatthe vibration response of each measuring point is efficiently controlled when thecontrol system is working in despite of single frequency excitation or doublefrequencies excitation, thus demonstrating the effectiveness and the feasibility ofcontrol strategy of active vibration isolation on the flexible base.