• International Journal of Safety
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• v.6 no.1
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• pp.22-25
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• 2007

Damping out high frequency low amplitude structural vibrations using PZT bimorph is presented. Static and Dynamic analyses of the piezoelectric bimorph bender were performed. Three layer piezoelectric actuators were modeled with SOLID5 coupled-field elements using ANSYS. Static deflection and modal analyses of the piezoelectric bimorph bender are presented. Proper tuning of the values of the resistor and inductor in the shunt circuit is required for maximum vibration suppression.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.733-736
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• 2003

This paper presents two systems of two-stage electrohydraulic servovalve with a nozzle-flapper pilot stage, which is controlled by stack-type piezoelectric elements. Two flapper moving mechanisms proposed in this research can compensate for the hysteresis problem and thermal expansion of the piezoelectric elements. The experimental results show that the first flapper moving mechanism has the frequency response of over 500 Hz and the second one has the response of over 600 Hz. And the first simplified servovalve system rising the first flapper moving mechanism has the frequency response of about 150 Hz, and the second system has the response of about 300 Hz at the supply pressure of 210 bar

• Journal of the Korean Society for Precision Engineering
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• v.20 no.6
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• pp.71-80
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• 2003

This paper presents a two-stage electrohydraulic servovalve with a nozzle-flapper pilot stage, which is controlled by stack-type piezoelectric elements. The flapper moving mechanism developed in this research can compensate for the hysteresis problem and thermal expansion of the piezoelectric elements. The experimental result shows that this flapper moving mechanism has the frequency response of about 600 Hz. And a simplified servovalve system using this flapper moving mechanism has the frequency response of about 300 Hz at the supply pressure of 210 bar.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.6
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• pp.29-37
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• 2003

This paper presents a two-stage electrohydraulic servovalve with a nozzle-flapper pilot stage, which is controlled by stack-type piezoelectric elements. The flapper moving mechanism developed in this research can compensate for the hysteresis problem and thermal expansion of the piezoelectric elements. The experimental result shows that this flapper moving mechanism has the frequency response of about 600 Hz. And a simplified servovalve system using this flapper moving mechanism has the frequency response of about 300 Hz at the supply pressure of 210 bar.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.152-157
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• 2001

An ultraprecision rotary motor is developed using inchworm motion of two belts actuated by elongation of piezoelectric elements. A symmetric lever mechanism with flexure hinges is designed to connect belts with piezoelectric elements. The lever mechanism is used not only to amplify the elongation of piezoelectric element but also to minimize the numbers of components and the effort for assembly. By experiment, the rotational angle by one cycle is varied from $0.2{\times}10-4 rad to 9.76{\times}10-4$ rad depending on input signal amplitude. Further, the motor has the capability of getting more precise rotational resolution by enlarging the radius of the rotor.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.49-50
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• 2015

Piezoelectric elements are one of good candidates able to replace motors in various electronics devices. It is slim and compact and low power consumption compare to motors. Linear regulator or class-D amplifier are generally used for piezoelectric element driver, however, suffers from severe power consumption. In this paper, electrical modeling of piezoelectric element will be presented and switching losses on the driver due to the parasitic capacitance will be analyzed. And new ZVS full bridge converter with an inductor will be proposed so as to reduce the power losses.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.127-131
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• 2008

This paper deals with the performance evaluation of piezoelectric unimorph actuator. In the unimorph design, the thickness ratio of substrate to piezoelectric material and the elastic modulus ratio of substrate to piezoelectric material are important parameters. There exists only one structural configuration that satisfies the optimal condition among them, and actuators using that configuration exhibit better actuating displacements. Another design parameter is the piezoelectric coefficient which can be improved due to the induced tensile stress and voltages. The application of the tensile stress to the piezoelectric material makes it get higher piezoelectric coefficient and the total displacement performance of the unimorph actuator is improved. Finally, the piezoelectric actuator system with spring elements is fabricated and it shows higher actuating displacement capability.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.269-278
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• 2003

In this study, the method of the finite element modeling for free vibration control of beam-type smart structures with bonded plate-type piezoelectric sensors and actuators is proposed. Constitutive equations for the direct piezoelectric effect and converse piezoelectric effect of piezoelectric materials are considered. By using the variational principle, the equations of motion for the smart beam finite element are derived, The proposed 2-node beam finite element is an isoparametric element based on Timoshenko beam theory. Therefore, by analyzing beam-type smart structures with smart beam finite elements, it is possible to simulate the control of the structural behavior by applying voltages to piezoelectric actuators and monitoring of the structural behavior by sensing voltages of piezoelectric sensors. By using the smart beam finite element and constant-gain feed back control scheme, the formulation of the free vibration control for the beam structures with bonded plate-type piezoelectric sensors and actuators is proposed.

• Structural Engineering and Mechanics
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• v.12 no.5
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• pp.491-506
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• 2001

In this paper, a new three-dimensional piezoelectric thin shell element containing an integrated distributed piezoelectric sensor and actuator is proposed. The distributed piezoelectric sensor layer monitors the structural shape deformation due to the direct effect and the distributed actuator layer suppresses the deflection via the converse piezoelectric effect. A finite element formulation is presented for static response of laminated shell with piezoelectric sensors/actuators. An eight-node and forty-DOF shell element is built. The performance of the shell elements is improved by reduced integration technique. The static shape control of structure is derived. The shell element is verified by calculating piezoelectric polymeric PVDF bimorph beam. The results agreed with those obtained by theoretical analysis, Tzou and Tseng (1990) and Hwang and Park (1993) fairly well. At last, the static shape control of a paraboloidal antenna is presented.

• Coupled systems mechanics
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• v.2 no.1
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• pp.53-83
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• 2013

Sea waves induce significant pressures on coastal surfaces, especially on rocky vertical cliffs or breakwater structures (Peregrine 2003). In the present work, this hydrodynamic pressure is considered as the excitation acting on a piezoelectric material sheet, installed on a vertical cliff, and connected to an external electric circuit (on land). The whole hydro/piezo/electric system is modeled in the context of linear wave theory. The piezoelectric elements are assumed to be small plates, possibly of stack configuration, under a specific wiring. They are connected with an external circuit, modeled by a complex impedance, as usually happens in preliminary studies (Liang and Liao 2011). The piezoelectric elements are subjected to thickness-mode vibrations under the influence of incident harmonic water waves. Full, kinematic and dynamic, coupling is implemented along the water-solid interface, using propagation and evanescent modes (Athanassoulis and Belibassakis 1999). For most energetically interesting conditions the long-wave theory is valid, making the effect of evanescent modes negligible, and permitting us to calculate a closed-form solution for the efficiency of the energy harvesting system. It is found that the efficiency is dependent on two dimensionless hydro/piezo/electric parameters, and may become significant (as high as 30 - 50%) for appropriate combinations of parameter values, which, however, corresponds to exotically flexible piezoelectric materials. The existence or the possibility of constructing such kind of materials formulates a question to material scientists.