Theories And Techniques For Active Control Of Structural Acoustic Radiation And Transmission

The structural-acoustic coupling characteristics, mechanisms, effect of structural-acoustic coupling on natural mode and eigenfrequency of the system are analyzed theoretically and numerically. A new approach is presented for analyzing structural-acoustic coupling. The analysis results demonstrate that the strongly coupled system has obvious closed-loop feedback characteristics, whereas the weakly coupled system has obvious feedforward characteristics, and it is because of the presence of the feedback loop that the natural characteristics and eigenfrequency are changed. Cluster coupling characteristics between the structural and acoustic modes for the regular cavity and panel system are found, which determine the coupling interaction between the flexible panel and cavity. Any mode in one mode cluster only affects the modes and the modal eigenfrequency in the same cluster independently.The problem of sensing and active control of sound radiation into an enclosure is studied from the point of view of the acoustic radiation mode using the structural error sensing. Acoustic radiation modes of the flexible boundary of an enclosure are obtained using the eigenvalue decomposition based on the quadratic form of total acoustic potential energy. The physical characteristics of the radiation modes and the inherent relationships between the acoustic modes and the radiation modes are analyzed in detail. A model for the active control of sound radiation from the vibrating structure into an enclosure is presented based on the radiation modes sensing and using the lead zirconate titanate piezoelectric (PZT) actuators. The numerical simulations and analyses with the proposed strategy are conducted and the results are compared with those with the traditional PEM (acoustic potential energy minimization) and structural kinetic energy minimization.Combing finite element method and modal coupling theory, a new modeling method is developed for active minimization of radiated noise within a three-dimensional irregular enclosure. The modeling approach is validated through a comparison with the analytical result of a regular enclosure. Based on the developed active control model, active structural acoustic control is conducted and analyzed.Combing the subsystem modal coupling theory and the impedance-mobility approach, two analytical models are developed for the analysis and active control of structural acoustic radiation and transmission through the double-wall structure into the free field and enclosure. The matrix formulae for calculating the modal response of the coupled structural acoustic are derived and presented. Then the transmission characteristics of the double-wall structure are analyzed, and the active control of sound transmission through it is studied theoretically and numerically.On the basis of the model of sound transmission through double panel structure, the active control model under different control strategies is presented. Based on the model, active control of sound transmission through double panel is studied numerically, and the results are analyzed in detail. The results demonstrate that control strategy using the secondary sound source in the cavity is a better control strategy compared to other two control strategies, i.e. incident panel PZT control and radiating panel PZT control.An analytical model for active sound transmission control of a double panel structure using the acoustic radiation mode control is presented, control performance is studied numerically, and the influence of order number of radiation modes to be controlled and the sound speed of the air in the cavity on the control performance is analytically.A new FIR filter-based online secondary path identification algorithm is proposed to eliminate the interactive disturbances. Compared with existing algorithms, the proposed method doesn't need feeding extra noise to the secondary source, and is also different from the overall modeling method using the control output. Instead, the facts that the FIR filters have coefficient vectors equivalent to impulse responses corresponding to the transfer functions of physical systems are utilized, and when the coefficients of the control filter are updated, the filter coefficient vectors are different at different iteration steps because of estimation errors. Furthermore, in the method, the modeling of the secondary path is relatively independent of the active noise control system, and the reference signal is used as the input for the system identification. Therefore, the unwanted disturbances between the operation of the ANC controller and the identification of the secondary path are eliminated completely, and the complexity of ANC system is greatly reduced. Computer simulations show its effectiveness, robustness, and the advantage of low residual noise.Combining the charge output equation of the PVDF piezoelectric film and orthogonal property of trigonometric function, a new design approach for structural volume velocity sensor is presented, and an experiment for measuring structural volume velocity on a concrete model is conducted to validate the approach. The result reveals that the distributed volume velocity sensor has a better sensing accuracy. Active structural acoustic control experiment using the designed volume velocity sensor is also carried on and good control effects are obtained.