Finite Element Modeling And Active Vibration Control Of Smart Constrained Layer Damping Thin Plate

The development of lightweight automobile body makes body panel thinner, result in the body stiffness becoming lower, modal concentration becoming higher, which increases the low frequency vibration of automobile body structure and vehicle interior noise. The traditional NVH control methods limited to the shortcomings of passive damping technology and active control technology, cannot reach the ideal damping effect. Smart constrained layer damping(SCLD) vibration control technology, combination of the advantages of both passive and active control technology, can maintain high damping characteristic in a wide frequency range, especially excellent control effect in the lower frequency, providing new ideas and solutions for active control of low frequency vibration and noise of automobile.Thin plate structures are a crucial part of automobile body. In this paper, taking the physical simplified model of body thin structure—the clamped-clamped plate as the study object, active vibration control was studied by the SCLD plate structure. Firstly, finite-element SCLD coupling system dynamics analysis model was established according to the coupling motion and displacement compatibility, and meanwhile the damping characteristic of viscoelastic material varying with temperature and frequency was considered by GHM(Golla-Hughes-Mc Tavish) damping model, and the correctness of the model was then verified by the example calculation and modal experiment. Secondly, a combinatorial model reduction method based on the modal analysis theory was presented to address the large number of degrees of freedom of coupling system dynamics mode. Dynamic condensation was firstly performed in the physical coordinates, minority main modes were then retained to form the reduced model on the basis of the modal orthogonality in the equation of state, a low-dimensional real modal control model was then obtained from the conversion of complex modal space to the real modal space. Finally, since the modal coordinates could not be directly acquired by the physical sensor in engineering practice,modal state observer was designed based on separation theorem. An active vibration controller was designed with non-coupling modal control method and optimal control, and vibration active control experiments were accomplished.It is shown that the results of considering basic layer damping are closer to the experiment, significantly better than the results without considering basic layer damping. The finite element dynamic model can be obtained accurately by lesser dissipation of degrees of freedom by the method of introducing GHM model in global dynamic equations, reducing the workload of computation; Combination reduction method proposed in this paper is effective for SCLD structure. Control model obtained by model reduction is very helpful for the design and development of modal vibration controller; Modal controller in conjunction with state observer can better solve the difficulty of modal full-state feedback. Experiments of hardware-in-loop were carried out under in different external disturbance excitations. When the external incentive is single frequency signal excitation, vibration response amplitude attenuates 60%. When the external incentive is complicated periodic signal, vibration response amplitude decreases nearly 50%. When the external excitation is gauss white noise, the root mean square values of vibration response reduces 9.48%, the vibration control effect is desirable.