• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.10
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• pp.803-810
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• 2009

Micromirrors have a wide range of applications such as optical switches, laser scanners, and digital projection displays. Due to their low performances and high costs, however, practical applications of micromirrors are quite limited. At present micromirrors demand not only a better design but also a simple fabrication process. In this study a twisting-type micromirror that can be driven by two thermal bimorph actuators bending in opposite directions is designed from electro-thermo-mechanical theories and fabricated through a simple MEMS process. Each actuator consists of $SiO_2$ and gold thin-film layers. Simplified analytical model has been built to optimize the performance of micromirror. Due to unexpected resistance increase of metal film and alignment mismatch during fabrication process, experimental rotation angles of micromirrors are about $11^{\circ}$ at applied voltages less than 0.6V. From numerical simulation and analytical studies, however, the next design can provide rotation angles over $20^{\circ}$ at the same applied voltage.

• Journal of Power Electronics
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• v.14 no.5
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• pp.957-966
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• 2014

Some of DC actuators used in home automation, office automation, medical equipment and automotive systems require a position sensor. In low power applications, the introduction of such a transducer remarkably increases the whole system cost, which justifies the development of sensorless position estimation techniques. The well-known AC motor drive sensorless techniques exploiting the fundamental component of the back electromotive force cannot be used on DC motor drives. In addition, the sophisticated approaches based on current or voltage signal injection cannot be used. Therefore, an effective and inexpensive sensorless position estimation technique suitable for DC motors is presented in this paper. This technique exploits the periodic pulses of the armature current caused by commutation. It is based on a simple pulse counting algorithm, suitable for coping with the rather large variability of the pulse frequency and it leads to the realization of a sensorless position control system for low cost, medium performance systems, like those in the field of automotive applications.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1231-1236
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• 2007

This study presents the static and dynamic actuating performances of a bending piezoelectric actuator with a thin sandwiched PZT plate under a static load. The stored elastic energy within the actuators which occurs during a curing process is obtained through a flexural bending test. An actuating performance is evaluated in terms of an actuating displacement at the simply supported condition. The results reveal that an actuator that consists of a top layer having a high elastic modulus and a low coefficient of thermal expansion exhibits a better performance than the rest of actuators due to the formation of the large stored elastic energy within the actuator system. When actuators are excited at the alternating current voltage, the effect of PZT ceramic softening results in a slight reduction in the resonance frequency of each actuator as the applied electric field increases. It is thus suggested that the static and dynamic actuating characteristics of bending piezoelectric actuators with a thin sandwiched PZT plate should be simultaneously considered in controlling their performances.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.12
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• pp.639-647
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• 2001

We present an integrated optical microswitch, composed of silicon waveguides, gold-coaled silicon micromirrors, and electrostatic contact actuators, for applications to the optical signal transceivers. For a low switching voltage, we modify the conventional curled electrode microactuator into a electrostatic microactuator with touch-down beams. We fabricate the silicon waveguides and the electrostatically actuated micromirrors using the ICP etching process of SOI wafers. We observe the single mode wave propagation through the silicon waveguide with the measured micromirror loss of $4.18\pm0.25dB$. We analyze major source of the micromirror loss, thereby presenting guidelines for low-loss micromirror designs. From the fabricated microswitch, we measure the switching voltage of 31.74V at the resonant frequency of 6.89kHz. Compared to the conventional microactuator, the present contact microactuator achieves 77.4% reduction of the switching voltage. We also discuss a feasible method to reduce the switching voltage to 10V level by using the electrode insulation layers having the residual stress less than 30MPa.

• Macromolecular Research
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• v.14 no.6
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• pp.624-629
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• 2006

The cellulose-based, Electroactive Paper (EAPap) has recently been reported as a smart material with the advantages of lightweight, dry condition, biodegradability, sustainability, large displacement output and low actuation voltage. However, it requires high humidity.. This paper introduces an EAPap made with a cellulose solution and lithium chloride (LiCl), which can be actuated in room humidity condition. The fabrication process, performance test and effect of LiCl content of the EAPap actuator are illustrated. The bending displacement of the EAPap actuators was evaluated with actuation voltage, frequency, humidity and LiCl content changes. At a LiCl/ cellulose content of 3:10, the displacement output was maximized at a room humidity condition. Even though the displacement output was less than that of a high humidity EAPap actuator, the mechanical power output was not reduced due to the increased resonance frequency, which is promising for developing EAPap actuators that are less sensitive to humidity.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.11
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• pp.971-975
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• 2004

This paper deals with the idea of Electroactive paper (EAPap) actuator and its application possibility. EAPap is a paper that produces large displacement under electrical excitation. EAPap is made with a cellulose paper by constructing thin electrodes on both sides of the paper. When electrical voltage is applied on the electrodes, the EAPap produces bending displacement. EAPap has merits in terms of lightweight, dryness, large displacement output, low actuation voltage and low power consumption. Since the power requirement is so small that it is suitable for microwave-driven smart actuators. This paper describes the working principle and performance of EAPap as an artificial muscle and its possibility far many applications.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1558-1562
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• 2008

Ionic polymer metal composite (IPMC), one of Electro- Active Polymer (EAP) actuators, has great attention due to the low-voltage driven, large deformation and its potential for artificial muscles. In this paper, we firstly review fish swimming modes using various propulsion mechanisms. Based on study on the swimming mechanisms, we develop an underwater robot actuator which mimics fanning motion of webfoot form. It consists of four actuators fabricated by using IPMC and PDMS which mimics Bio-inspired motion Experiments using a prototype show that the webfooted IPMC actuator generates large deformation and propulsion.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.461-469
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• 2002

This paper deals with a fully coupled piezoelectric-mechanical assumed strain solid element that can be used for geometric and material nonlinear modeling of thin piezoelectric actuators. Since the assumed strain solid element can alleviate locking, the element is suitable for performance analysis of very thin actuators without locking. A finite element code is developed based on the finite element formulation and validated by solving typical numerical examples such as bimorph and unimorph beams. Using thecode, we have conducted performance analysis for LIPCA actuator. The estimated actuation displacement of LIPCA agrees well with experimental data under low prescribed voltage.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1185-1191
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• 2011

The kinematic characteristics of cutting device significantly affects cutting performance in 2-dimensional elliptical vibration cutting(EVC) where the cutting tool cuts workpiece, traversing a micro-scale elliptical trajectory in a trochoidal motion. In this study, kinematical characteristics of EVC device constructed with two parallel stacked piezoelectric actuators were analytically modeled and compared with the experimental results. The EVC device was subjected to step and low-frequency(0.1 Hz) sinusoidal inputs to reveal only its kinematical displacement characteristics. Hysteresis in the motion of the device was observed in the thrust direction and distinctive skew of the major axis of the elliptical trajectory of the cutting tool was also noticed. Discrepancy in the voltage-to-displacement characteristics of the piezoelectric actuators was found to largely contribute to the skew of the major axis of the elliptical trajectory of the cutting tool. Analytical kinematical model predicted the cutting direction displacement within 10 % error in magnitude with no phase error, but in estimating the thrust direction displacement, it showed a $27^{\circ}$ of phase-lag compared with the measured displacement with no magnitude error.

• Macromolecular Research
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• v.17 no.12
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• pp.1032-1038
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• 2009

A polypyrrole (PPy)/alumina composite filler prepared via in-situ polymerization of pyrrole on alumina particles was incorporated into $Nafion^{(R)}$ to improve the performance of ionic polymer-metal composite (IPMC) actuators. The IPMCs with the pristine PPy without alumina support did not show bending displacements superior to that of the bare Nafion-based IPMC, except at a high PPy content of 4 wt%. This result was attributed to the low redox efficiency of the PPy alone in the IPMC and may have also been related to the modulus of the IPMC. However, at the optimized filler contents, the cyclic displacement of the IPMCs bearing the PPy/alumina filler was 2.2 times larger than that of the bare Nafion-based IPMC under an applied AC potential of 3 Vat 1 Hz. Even under a low AC potential of 1.5 V at 1 Hz, the displacement of the PPy/alumina-based IPMCs was a viable level of performance for actuator applications and was 2.7 times higher than that of the conventional Nafion-based IPMC. The generated blocking force was also improved with the PPy/aiumina composite filler. The greatly enhanced performance and the low-voltage-operational characteristic of the IPMCs bearing the PPy/alumina filler were attributed to the synergic effects of the neighboring alumina moiety near the PPy moiety involving electrochemical redox reactions.