Study On Vibration And Noise Control Of Car Body Structure Based On Smart Constrained Layer Damping

As the increasing of the production and quantity of the cars, energy economy, environment protection, safety have been the important problems for the auto technology's development. Under the situation of the noncommittal way of the new energy, the car lightweight technology which used by the global main auto enterprise, will be the best way to solve the problem before. Car body, as the most important constitution of the car, is the key position to attain the lightweight target of the car. However, when the car body becomes thin, the body structure's rigidity becomes smaller, the flexibility becomes bigger, and the modal concentration becomes higher, which lead to the deterioration of dynamic performance and NVH performance for the body structure. For this situation, the conventional NVH control method, which used to be restricted by the shortcoming of the passive and active damping technology, can't reach the ideal damping effect. At this background, learning from the good performance of Smart Constrained Layer Damping (SCLD) structure on the active control of the sheet metal's vibration, the potential of SCLD structure on vibration and noise Control of Car Body is further discussed. The active control fundamental research of the lightweight body's NVH function based on the SCLD structure is done.It can not only develop new NVH solution, but also open new path to development of high grade, high quality cars for the future. .Firstly, the establishment of dynamic model is researched for the SCLD plate which is the abstract physical model of the car body. In the modeling, the coupling motion and displacement compatibility of layers and the electrical and mechanical coupling effect of piezoelectric materials are considered. The constitutive property varied with frequency and temperature for viscoelastic material is characterized by ADF model. Then combining with the finite element method, a new coupling dynamic analysis model is derived based on the Hamilton principle. The results of the numerical examples and modal analysis experiments show that the model can accurately reflect the dynamic characteristics of SCLD plate. Due to the confine of ADF model and FEA method, SCLD coupling structure's dynamic model is faulted for its giant DOF, a new model reduction method composed of the complex modal truncation method and the internal balanced order reduction method proposed in the state space. The dynamic model with low DOF, considerable and controllable characteristics is derived based on the method above. The results of the examples indicate that the proposed reduction method is feasible and the reduced model can be directly applied to the development of the follow-up control system.Regarding thin steel plate with partially covered SCLD structure as the research object, the active controllers are designed respectively based on the optimal control theory and the adaptive feed forward filtering algorithm, and simulation analysis is accomplished. Then, based on the adaptive active control system, the vibration control problem of the thin steel with SCLD structure is researched by experiment. It shows that the SCLD structure has good actuator ability and strong vibration response inhibitory ability; the adaptive controller of SCLD structure owns strong self-adjustment ability, good dynamic tracking characteristics and robustness. Then a radiated acoustic power forecast model of the SCLD system is established. Based on the numerical methods, the radiation ability and its influencing factors of sheet steel with SCLD structure are investigated. The research shows that the SCLD structure can not only effectively reduce the acoustic radiation of the plate, but also can make up for PCLD structure on the low frequency noise control; the damping layer thickness, thickness of splicing layer and piezoelectric layer thickness of SCLD structure have effect on the structural dynamic characteristics and acoustic radiation control, especially the splicing layer thickness and piezoelectric layer thickness.In order to apply SCLD technology from simple to complex vibration system, SCLD structure theory is studied based on dynamic neural network. Firstly,based on LMBP algorithm of multilayer feed forward neural network, an adaptive adjust fast algorithm on dynamic training for network learning rate is put forward, named ILMBP algorithm. Then the algorithm is test on neural network learning, linear system identification and nonlinear system identification. By a large number of researches, it shows that the algorithm which put forward before not only has good recognition performance, but also can improve the convergence speed of neural network learning. Then,the offline identification of control system for SCLD plate is realized by NARX neural network model which using ILMBP algorithm. Then adaptive control system based on identification model is set up. The results show that the NARX network model which based on ILMBP algorithm can obtain higher accuracy of identification model and can really represent the dynamic behavior of the system. It can be directly applied to the simulation analysis of active controller and the parameters of the controller can be directly used in the field experiments. Finally, based on the conclusion of the study before, taking the body scale model of a car as the experimental object, an adaptive active control system for vibration and noise of SCLD body structure has been build. The hardware online platform of active control experiment for vibration and noise of SCLD body structure has also been established. Under different external disturbance excitation, the active control experiments on body structure are carried out based on the SCLD technology, and the satisfactory results have been obtained. Among them, under single harmonic excitation with low frequency, the interior vibration and noise of the car has reduced 7.6dB (A) after control; as well as under the complex periodic signal excitation with low frequency, the interior vibration and noise of the car has reduced 5.1 dB(A) after control, and the driving voltage on SCLD structure is all smaller than 150 volt . Thus it can be proved that SCLD structure can effectively improve the NVH performance of car body structure with low frequency in lower energy. It also can lay a good foundation for further engineering application.