Index of content:
Volume 119, Issue 3, March 2006
- STRUCTURAL ACOUSTICS AND VIBRATION 
Experimental and numerical investigations on resonant characteristics of a single-layer piezoceramic plate and a cross-ply piezolaminated composite plate119(2006); http://dx.doi.org/10.1121/1.2161428View Description Hide Description
Piezolaminated composite plates are widely used in many industrial applications such as intelligent structures and advanced aerospace structural applications. To improve the dynamic performance of the piezolaminated composite structures, it is necessary to experimentally investigate the resonantcharacteristics of these structures. Three measurement techniques are used in this study to investigate the vibration behavior of tested specimens. The first method, AF-ESPI (amplitude-fluctuation electronic speckle pattern interferometry), is the major technique for measuring the resonantcharacteristics of a single-layer piezoceramic plate and a multilayer cross-ply glass fiber reinforced plastics piezolaminated composite plate for completely free conditions. The completely free condition is approximated in experiment by placing and partially sticking the specimen on the surface of a very soft sponge. A thin single-layer piezoceramic plate is first investigated and up to twenty-six transverse modes are presented. Excellent quality of interferometric fringe patterns for vibration mode shapes is presented. The influence of the actual boundaries on the resonantcharacteristics of the thin piezoceramic plate is discussed. The second method, laser Doppler vibrometer, and the third method, impedance analyzer, are both employed to verify the AF-ESPI results for the piezolaminated composite plate. Both in-plane and out-of-plane resonant frequencies and vibration mode shapes of the piezolaminated composite plate are demonstrated. Finally, numerical computations based on the finite element analysis are presented for comparison with the experimental results. Excellent agreement between the experimental measured data and the numerical calculated results are found for resonant frequencies and mode shapes of the single-layer piezoceramic plate and the cross-ply piezolaminated composite plate.
119(2006); http://dx.doi.org/10.1121/1.2163270View Description Hide Description
This paper examines the performance of centralized and decentralized feedback controllers on a plate with multiple colocated velocity sensors and force actuators. The performance is measured by the reduction in either kinetic energy or sound radiation, when the plate is excited with a randomly distributed, white pressure field or colored noise. The trade-off between performance and control effort is examined for each case. The controllers examined are decentralized absolute velocity feedback, centralized absolute velocity feedback control and linear quadratic Gaussian (LQG) control. It is seen that, despite the fact that LQG control is a centralized, dynamic controller, there is little overall performance improvement in comparison to decentralized direct velocity feedback control if both are limited to the same control effort.