Active Control Of Structural Vibration And Acoustic Radiation Based On Reduced Order Model And Pressure Feedback Method

For a long time,the ship vibration and noise control are hot spots in research area,which brought much influence to comfort and safety of the ship.The ship vibration and noise control mostly stay in the passive control,especially to the underwater structure.In order to effectively suppress the vibro-acoustic response of an underwater structure,its vibration and sound radiation active control simulation and tests were implemented based on two different kinds of reduced order model respectively.And a active control of vibro-acoustic response using sound pressure feedback was also numerically studied.The main contents are as follows:First of all,the compressible fluid-loaded undamped modal matrix was used to build the reduced order model of underwater structure.Due to dimension number's reduction,a simplified active vibration control system was designed to decrease the number of sensors and actuators.Active vibration control of an underwater structural was simulated with the linear quadratic(LQ)control method and variable stiffness control method,respectively.The simulation and test results showed that the plate5 s vibro-acoustic response is quite well controlled with the LQ control method,while the natural frequencies of the plate can be changed according to requirements with the variable stiffness control method;based on the reduced order model,the active control is relatively easy to implement in tests and the test results verifies the vibration reduction effects of active control of vibration ans acoustic radiation on underwater structures.Secondly,the problem of modal pole assignment of a coupled structural acoustic system based on reduced order model from the forced responses was addressed.The reduced order model might be obtained entirely from vibration data,there being no need to know the structural matrices and the acoustic impedance matrix.The modal natural frequencies and damping ratios of the coupled system are assigned separately and using output feedback control by collocated actuator-sensor arrangements simultaneously.Different control configurations are discussed and active structural acoustic control is demonstrated numerically using a fluid-loaded plate.The numerical examples show that chosen eigenvalues may be assigned to predetermined values.Finally,the active control of vibro-acoustic response using sound pressure feedback was numerically studied.An output feedback approach based on sound pressure measurement for pole placement is proposed.The control performance is evaluated for the case of a baffled plate in air.Measures of observability of a mode in pressure outputs.Numerical results show that the chosen poles may be assigned to predetermined values by the active control with complex gains.This method do not use microphones as the error sensors,the acoustic pressures from the microphones are not sought to be minimized but to feedback for pole assignment for the active control of vibro-acoustic response.