Research On Vibration Control Of Dynamic Vibration Absorbers For Submarine Isolation System

The application of vibration isolation technology in large-scale rotating machinery of thesubmarine can effectively depress the structure-borne sound which is induced by the machineryfacilities, and thus reduce the radiated noise from the submerged submarine. However, the traditionalvibration isolation device is limited to the form of the passive isolation with a poor performance withinthe low-frequency band. In addition, with the increasing operating speed of the rotating machinery aswell as the occurring of the large-scale and lightweight submarines, the elastic vibration modes of theisolation devices and the controlled objects can easily be excited. For the above reasons, it is oftenunlikely to take a single isolation measure to achieve the requirements of the vibration attenuation,which could limit the application and development of the isolation devices in submarine.This thesis focuses on the study of the vibration control approach, taking advantage of thesingle-layer isolation system and the floating raft isolation one, for the submarines. Above all, thedynamic models of these two systems without the dynamic vibration absorbers (DVAs) are derived byassembling the mobility matrices of subsystems when a combined excitation acts on the source.According to the relationship between the force and the velocity on each subsystem’s interfaces, thepower flow expressions of the systems are derived, and the impact of the structural parameters on thepower flow transmitted into the subsystem of the isolation devices are also analyzed. Subsequently, bychanging the system configuration where several DVAs are mounted on the two isolation devicesrespectively, an integrated control model taking account of the vibration absorption and isolation isestablished. The performance of the vibration reduction under different conditions is evaluated bycomparing the power flow transmitted into the foundation before installing DVAs with that afterinstalling ones. Finally, the control strategies for the minimization of total power flow, axial force andaxial velocity are proposed by employing the adaptive active vibration absorbers (AAVAs) for the activevibration control of the floating raft isolation system, the control behavior of the AAVAs is verifiedunder the single-frequency excitation and the multi-frequency excitation respectively. Numericalsimulation results show that the control strategy based on the total power flow minimization is muchbetter than the other ones. It can achieve the broad band vibration absorption effectively, and reduce thepower flow transmitted into the foundation significantly. The control strategy using the axial forceminimization produces good results at low frequencies, whereas the control strategy using the axial velocity minimization maintains good results at intermediate frequencies.