This paper deals with the static and dynamic electromechanical responses of piezoelectric layered structures (multimorphs). Based on the Bernoulli-Euler plate model including the dynamics of piezoelectric, electrode and substrate layers, we obtain the natural frequencies, maximum displacement and resultant force of a symmetric cantilevered multimorph. The proposed theoretical model is verified by experiments using a 20-layered PZT (plumbum-zirconate-titanate) multimorph, and it is compared to the conventional bimorph model. Experimental results agree with the analytical predictions on the natural frequencies and vertical displacement. With the analytical solution for multimorph, we investigate the effects of the layer number and the layer thickness on natural frequency, maximum deflection and output force. It is found that there exists an optimum number of piezoelectric layers to maximize the transverse deflection. There also exists a specific value of the thickness ratio between piezoelectric and structure layers to maximize both the tip deflection and force.

The optimal location problem of distributed sensor/actuator for observation and control of a flexible structure is investigated. Using a property of controllability and observability grammian matrices, this approach employs a nonlinear optimization technique to determine the optimal placement of a distributed sensor/actuator. The effect of unimportant modes that do not strongly affect the structural behavior of a system is minimized and the effect of important modes is maximized. The final objective function is expressed as the combinational form of two different objective functions. This technique is applied to several types of beam support conditions and the corresponding optimal locations are determined.

In this paper, a new optical pick-up actuator is proposed using PMN-PT (lead magnesium niobate-lead titanate) bimorphs for slim and small form factor optical disk drives. We suggest a novel structure enabling both tracking and focusing motions by changing the moving directions of the two parallel bimorphs. A cymbal-type flextensional structure is used as a displacement amplifier in order to meet the stroke requirement for optical pick-up actuators. We have performed the theoretical analyses for the bimorph actuator and displacement amplifier to predict the resultant force and displacement. The proposed actuator based on PMN-PT bimorphs and displacement amplifier has been manufactured, and the experimental results are compared to the analytical predictions. Experimental results agree well with the analytical predictions, showing that the cymbal structure amplifies the displacement twice and the focusing stroke is 52 μm at 10 V.

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In an inverse acoustic problem with nearfield sources, it is important to separate multiple acoustic sources and to measure the position of each target. This paper proposes a new algorithm by applying multiple signal classification (MUSIC) to the outputs of discrete wavelet transformation with subband selection based on the entropy threshold. Some numerical experiments show that the proposed method can estimate the more precise positions than a conventional MUSIC algorithm under moderately correlated signal and relatively low signal-to-noise ratio case.