Study On Multi-objectvie Opimization And Adaptive Control Of Active Constrained Layer Damping Structure

The automobile has become the most important transportation vehicles in the world, and vehicles comfort requirements are also increasing. It makes the NVH performance become an important index to evaluate the quality of vehicles, and the major car companies make much research to improve NVH performance. On the other hand, engery saving and environmental protection is one of the key issues influcing the sustainable development of automobile industry, and lightweight technology is currently the most effective method to deal with this problem. However, lightweight will make body panels thinner, weaken the body attenuation ability for low-frequency noise, and deteriorate the NVH performance. For this situation, due to its shortcomings, the conventional NVH control method, such as damping coating, can not achieve the satisfactory effect on vibration and noise reduction. In this paper, taking aforementioned situations as the background and centering on the theme of vibration and noise control using ACLD, a thin plate abstracted from the body thin-walled structure is seleced as the main research object, and some researches have been done from the aspects of dynamic modeling of ACLD/plate, multi-objective optimization and vibration/noise control strategy.① The finite element dynamical model of ACLD/plate is established. Considering constitutive equation of piezoelectric materials and the constant complex model and GHM model for shear modulus of viscoelastic material(VEM), the dynamical model of ACLD/plate is developed by using finite element method.Taking a cantilever plate partly treated with ACLD patches as an example, the natural frequencies and damping ratios are obtained from the use of Matlab code, Ansys software and modal testing. Comparison among the results show the finite element model can accurately reflect the characteristic of ACLD/plate.② The multi-objective optimization for CLD/plate is investigated. Taking locations of CLD patches, thicknesses of constrained layer and viscoelastic material as design variables, and maximizing several modal loss factors as objectives, the multi-objective optimization model of CLD/plate is developed based on its dynamic model. The improved non-nominated sorting genetic algorithm(INSGA-II) is proposed to solve the optimization problem with hybrid variables. The results of the examples show INSGA-II has better performance.Based on ‘step-by-step’ multi-objectives optimization strategy, optimal locations of CLD patches are firstly obtained, and then come the optimal thicknesses of constrained layer and VEM. Based on the integrated optimization strategy, the Pareto optimal locations of CLD patches, thicknesses of constrained layer and VEM are obtained simultaniously. As the results of numerical example, the various feasible Pareto optimal CLD/plate configurations are obtained, and effects of design variables on vibration characteristics are also discussed. The accelearion frequency responses experiment is carried out with two different optimal CLD locations. The result proves the validaty of INSGA-II③ Aaptive vibration control for ACLD/plate is investigated based on Fx LMS algorithm. The reduced state space model of ACLD/plate is obtained using balance order reduction method. Adaptive feedforward filtering controller based on Fx LMS algorithm is designed and employed to control the vibration of ACLD/plate, and its performance is discussed. Simulation results show that the controller is efficient for controlling the vibration induced by sine excitation and mixed periodic excitation; the secondary path model has a significant effect on performance of the controller. Furthermore, the Fx LMS controller with online identified secondary path is designed and simulated. The hardware in-loop platform of active vibration control experiment for ACLD/plate is established. The vibration of ACLD/plate induced by different excitation is suppressed using Fx LMS controller with online identified secondary path. The results show that the controller has good performance and the ACLD technique is good choice for controlling structural vibration.④ The hybrid control strategy combined feedback LQG and feedforwad Fx LMS is proposed to suppress vibration of ACLD cantilever plate. Firstly, the LQG controller is design for the vibration induced by process noise and measurement noise. Then the hybrid controller is established by combining LQG controller and Fx LMS controller. It can be utilized individually or in a hybrid way to suppress the vibration of the plate Simulation analysis show that the hybrid controller can reduce the vibration subjected to a complicated disturbance substantially without more control effort. Meanwhile, perfect robustness and more rapid stable convergence are demonstrated in proposed hybrid controller.⑤ Structural acoustic control of a closed cavity abstracted from the automobile passenger cabin is explored preliminarily using ACLD technique. The sound pressure of field points in inner cavity, which is induced by vibration of the only ACLD/plate, is formulated based on Helmholze equation. A case that optimal locations of CLD patches on the elastic plate is given using genetic algorithm, and a sound frequency response experiment is carried out. The results show that sound pressure of cavity center can be reduced effectively by optimal configurations of CLD patches. Afterwards, a closed cavity active structural acoustic control platform is established, and the noise in cavity is suppressed using the Fx LMS controller with online identified secondary path. The results show that the sound pressure with expected frequency can be depressed significantly and the designed controller has strong adaptability and robustness.