• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1843-1847
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• 2012

Piezo devices have large power density and simple structure. They can generate larger force than the conventional actuators. It has also wide bandwidth with fast response in a compact size. Thus the piezo devices are expected to be used widely in the future for small actuators with fast response time and large actuating force. However, the piezo actuators need high voltage with high driving current due to their large capacitive property. In this paper, we propose a simple method to drive piezo devices using voltage inversion circuit with coil inductance. Experiments with real circuit demonstrates that the proposed scheme can improve the energy efficiency very much.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.12
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• pp.1281-1286
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• 2013

In this paper, a miniaturized stage with two prismatic-prismatic joints (2-PP) type parallel compliant mechanism driven by piezo actuators is proposed. This stage consists of two layers which are a motion guide layer and an actuation layer. The motion guide layer has 2-PP type parallel compliant mechanism to guide two translational motions, whereas the actuation layer has two leverage type amplification mechanisms and two piezo actuators to generate forces. Since the volume of the stage is too small to mount displacement sensors, the piezo actuators embedding strain gauge sensors are chosen. With the strain gauge-embedded piezo actuators, a semi-control is implemented, which results in hysteresis compensation of the stage. As the results, the operating range of $30{\mu}m$, the resolution of 20 nm, and the bandwidth of 400 Hz in each axis were obtained in the experiments.

• Composites Research
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• v.27 no.2
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• pp.47-51
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• 2014

The purpose of the present study is to develop lightweight and simple smart actuators in order to replace conventional hydraulic/pneumatic actuators, and to apply the developed actuators to the actuation systems of a small unmanned air vehicle. This research describes the procedures of design, manufacturing of the piezo-composite actuator, and the performance evaluation. From the test results of the developed devices, we found the possibility of piezo-composite actuator could be used as a control surface of a small UAV system. We have designed and manufactured two kinds of piezo-composite actuators, unimorph actuator and bimorph actuator. The manufactured actuators were evaluated through the performance testes. It was found that the bimorph type actuator showed more linear angle change for the same excitation voltage variation than unimorph type. It is expected that piezo-composite actuator has a possibility to be used not only as a control surface of small unmanned flying vehicle but also as a control surface actuator of a guided missile fin through the miniaturization of power supply and control system.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.491-496
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• 2000

The objective of this study is to increase lift and decrease drag of an airfoil by delaying flow separation with piezo-ceramic actuators. The airfoil used is NACA 0012 and the chord length is 30cm. An experiment is performed at the freestream velocity of 15m/s at which the Reynolds number is $3{\times}10^5$. Seven rectangular actuators are attached to the airfoil surface and move up and down based on the electric signal. At the attack angle of $16^{\circ}$, the separation point is delayed downstream due to momentum addition induced by the movement of the actuators. Drag and lift are measured using an in-house 2-dimensional load cell and the surface pressures are also measured. Lift is increased by 10%, drag is reduced by 50%, and the efficiency is increased to 170%. The flow fields with and without control are visualized using the smoke-wire and tuft techniques.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.5
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• pp.546-551
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• 2016

The objective of this study is to investigate the response delays between piezo-stack actuator and the displacement magnifier of jetting dispenser and to reduce its falling time in terms of displacement optimization. The dispenser is driven by the dual piezo-stack actuators with a hinge lever mechanism to precisely control flow rate of the working fluid (3000 cP). It is commonly found that piezo actuator-driven jetting dispensers involving viscous working fluids have displacement optimization problem for ideal performance. The response delay of the system is caused by the phenomenon that the displacement magnifier cannot exactly follow the motion of the piezo actuators. The response delay may lower the performance of the system due to the inaccurate discharge of working fluid or even damages to the system itself due to inharmonious motion of piezo actuators with lever system. To reduce its response delay, a new displacement profile obtained from displacement optimization is suggested; its performance is tested through finite element analysis; and experiments are carried out to verify the performance of the obtained displacement profile.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.756-760
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• 2011

This paper proposed an alignment stage driven by piezo actuators for alignment process of a contact-type lithography. Among contact-type lithography processes, an UV-curable nanoimprint process is an unique process to be able to align patterns on upper and lower layers. An alignment stage of the UV-curable nanoimprint process requires nano-level resolution as well as high stiffness to overcome friction force due to contact moving. In this paper, the alignment stage consists of a compliant mechanism using flexure hinges, piezo actuators for high force generation, and capacitive sensors for high-resolution measurement. The compliant mechanism is implemented by four prismatic-prismatic compliant chains for two degree-of-freedom translations. The compliant mechanism is composed of flexure hinges with high stiffness, and it is directly actuated by the piezo actuators which increases the stiffness of the mechanism, also. The performance of the ultra-precision stage is demonstrated by experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.649-654
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• 2003

This paper is focused on the research of the ultra precision linear motor by using piezo stack actuators. The development of linear motor which can be controlled nano or micro scale is necessary for the precision manufacturing. Self-moving-cell principle is used for the design of linear motor Self-moving-cell linear motor is consisted of three cell structures, and each cell has two shells and one piezo-stack actuator. Each cell can do clamping and moving by two shell structures. The shell structure deformation by piezo stack actuator can move the linear motor by losing the clamping between the shall and guideway. This paper presents the design, manufacturing and test of the motor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1095-1100
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• 2013

Piezo devices have large power density and simple structure compared with conventional electrical motors. Thus they can generate larger forces than the conventional actuators with small size. Their resopnses to commands are also very fast and thus the bandwidths are very wide. Thus the piezo devices are expected to be used widely in the future for actuating devices requiring fast response and large actuating force with small size. However, the piezo actuators need high voltage with high driving current due to their large capacitive property. In this paper, proposed is a simple method to drive piezo devices using voltage inversion circuit with coli inductance. The coil inductance carries the charges in the piezo device to the opposite side, inverting the polarity of the applied voltage, thus saving the power to drive the device with AC voltages. Experiments with real circuit demonstrates that the proposed scheme can improve the energy efficiency very much.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5409-5415
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• 2012

Piezo ceramic actuator is used for various industrial products such as spray, dispenser, and valve control etc. Since the deflection of the piezo ceramic element depends on the applied voltage, it is required a power amplifier with high voltage supply for driving the piezo ceramic actuators. In this paper, we develop a simple H-bridge type power amplifier and a compact flyback type high voltage switching mode power supply for piezo ceramic actuators. It is easy to adjust the amount of energy input to piezo ceramic actuator by pulse-width-modulation with H-bridge type power amplifier.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.8
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• pp.1112-1118
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• 2000

The objective of this study is to increase lift and decrease drag of an airfoil at high angles of attack by delaying flow separation with piezo-ceramic actuators. The airfoil used is NACA 0012 and its chord length is 0.3m. An experiment is performed at the freestream velocity of 15m/s at which the Reynolds number based on the chord length is $2{\times}10^5$. Seven rectangular actuators are attached to the airfoil surface and move up and down based on the electric signal. Drag and lift are measured using an in-house two-dimensional force-balance and the surface pressures are also measured. At the attack angle of $16^{\circ}$, the separation point is delayed downstream due to momentum addition induced by the movement of the actuators. Lift is increased by 10%, drag is reduced by 37%, and the efficiency is increased up to 170%. The flow fields with and without control are visualized using the smoke-wire and tuft techniques.