• Journal of the Korean Ceramic Society
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• v.41 no.3
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• pp.216-220
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• 2004

This paper is concerned with the development of stacked ceramic thin actuation layer IDEAL (InterDigitated Electrode Actuation Layer) using d$_{33}$ actuation mechanism of piezoelectric ceramic. Most of the thin piezoelectric actuators are operated with d$_{31}$ actuation mechanism. Many kinds of piezoelectric ceramic actuators are strived now to improve the actuation performance. One of efforts to improve performance of piezoceramic actuators is the research trying to develop an actuator using the piezoelectric coefficient d$_{33}$ . The piezoelectric coefficient d$_{33}$ is almost twice larger than piezoelectric coefficient d$_{31}$ . Therefore, the induced strain of PZT thin layer with d$_{33}$ 3 actuation mechanism is bigger than that with d$_{31}$ actuation mechanism. The AFC(MIT) and LaRC-MFC$^{TM}$ which is developed by a research team of NASA Langley Research Center used d$_{33}$ actuation mechanism with surface interdigitated electrode to enhance its actuation performance. But their actuation mechanism is not perfect d$_{33}$ actuation mechanism since the interdigitated electrodes are placed at the surface of the actuation layer. In this research, the stacked ceramic thin actuation layer with imbedded interdigitated electrode is designed and manufactured. The actuation strain of stacked ceramic thin actuation layer is measured and compared with the actuation strain of the LaRC-MFC$^{TM}$. The comparison shows that the developed stacked ceramic thin actuation layer can produce 15% more actuation strain than LaRC-MFC$^{TM}$.> TM/.

• The Journal of Korea Robotics Society
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• v.12 no.2
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• pp.194-205
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• 2017

A redundantly actuated planar 3-degree-of-freedom parallel mechanism is analyzed to show its high application potential as a haptic device. Its structure along with the closed form forward position solutions is briefly discussed. Then its geometric and kinematic characteristics via singularity analysis, the kinematic isotropy index, and the input-output force transmission ratio are investigated both for the redundantly actuated cases and for the non-redundantly actuated case. In addition, comparative joint torque simulations of the mechanism with different number of redundant actuations as well as without redundant actuation are conducted to confirm the improved joint torque distribution characteristics. Through these analyses it is shown that the geometric and kinematic characteristics of the redundantly actuated mechanism are superior to the ones of the mechanism without redundant actuation. Thus, it can be concluded that the suggested planar mechanism with redundant actuation has a very high potential for haptic device applications.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1613-1616
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• 1997

In order to develop a human hand mechanism, a 5-bar finger with redundant actuation is designed and implemented. an optimal set of acutator locations and link lengths for the case of one redundant actuator is obtained by employing a composite design index which simulataneously consider several performance indices such as workspace, isotropic index, and force transmission ratio. Each joing is driven by an compact actuator mechanism having ultrasonic motor and a gear set with poeneiometer an controlled by VME Bus-based control system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.846-855
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• 1994

An effective stiffness, analogous to that of a wound spring, can be created by antagonistic redundant actuation of general closed-chain mechanisms. The qualitative and quantitative characteristics of the effective stiffness are investigated through a Four-bar mechanism, and a load distribution method is introduced which simultaneously guarantees the required system motion and the effective stiffness of the Four-bar mechanism. Furthermore, a simulation is performed to understand the inter-relationship among the effective stiffness, the Four-bar geometry, and the actuation effort. Based on this analysis, the Four-bar synthesis problem for effective stiffness generation is discussed.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.11
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• pp.960-966
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• 2016

This paper proposes a new concept of a soft and wearable upper-limb exoskeleton. A novel actuation principle, called the twisted string actuation principle, is implemented to make it lightweight, soft, and therefore easily wearable. Its power transmission mechanism and harness are designed to be soft and wearable, yet have enough control accuracy for rehabilitation. In addition to force transmission optimization, a speed enlargement mechanism is newly introduced in order to increase the contraction speed of the twisted string actuation mechanism by sacrificing the unnecessarily large gear reduction ratio of the twisted string mechanism. A prototype has been tested for mirroring therapy, and the feasibility of the proposed mechanism has been shown through a sufficiently accurate tracking performance.

• Smart Structures and Systems
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• v.12 no.5
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• pp.483-499
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• 2013

A new piezoceramic $d_{15}$ shear-induced torsion actuation mechanism representative benchmark is proposed and its experimentations and corresponding 3D finite element (FE) simulations are conducted. For this purpose, a long and thin smart sandwich cantilever beam is dimensioned and built so that it can be used later for either validating analytical Saint Venant-type solutions or for analyzing arm or blade-based smart structures and systems applications. The sandwich beam core is formed by two adjacent rows of 8 oppositely axially polarized d15 shear piezoceramic patches, and its faces are dimensionally identical and made of the same glass fiber reinforced polymer composite material. Quasi-static and static experimentations were made using a point laser sensor and a scanning laser vibrometer, while the 3D FE simulations were conducted using the commercial software $ABAQUS^{(R)}$. The measured transverse deflection by both sensors showed strong nonlinear and hysteretic (static only) variation with the actuation voltage, which cannot be caught by the linear 3D FE simulations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.769-770
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• 2012

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.5
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• pp.7-15
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• 2009

This paper introduces a new variable valve actuation mechanism with movable second cam center. Valve lift and open duration can be continuously varied according to engine speed and load conditions. A new method to analyze the kinematic relations between the first and second cam profiles and valve motion are also introduced. Because of rocker motion of the second cam, conventional motion conversion program could not be used in this problem. An example shows continuous variations of valve motion and adequate ramp incorporation throughout all valve lift modes. Valve acceleration profile at the high lift mode is similar to that of conventional valvetrains. Contact geometry analysis of the mechanism gives basic information on the load conditions between the components.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.418-426
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• 1995

A bubble-powered microactuator is designed conceptually. And the actuation mechanism due to bubble growth and collapse is studied numerically and analytically. In this analysis, it is estimated that the time lag for bubble formation on micro line heater, the duration of the bubble growth and collapse and the pressure change in actuator due to the bubble evolution. Based on these calculations, the actuator control scheme is visualized. This actuator may be applicable to the system which needs to pump liquid correctly and regularly.

• Smart Structures and Systems
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• v.13 no.1
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• pp.55-80
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• 2014

The present work pays emphasis on investigating the effect of different types of debonding on the bending behaviour of active sandwich beam, consisting of both extension and shear actuators. An active sandwich beam finite element is formulated by using Timoshenko's beam theory, characterized by first order shear deformation for the core and Euler-Bernoulli's beam theory for the top and bottom faces. The problem of debondings of extension actuator and face are dealt with by employing four-region model for inner debonding and three-region model for the edge debonding respectively. Displacement based continuity conditions are enforced at the interfaces of different regions using penalty method. Firstly, piezoelectric actuation of healthy sandwich beam is assessed through deflection analysis. Then the effect of actuators' debondings with different boundary conditions on bending behavior is computationally evaluated and experimentally clamped-free case is validated. The results generated will be useful to address the damage tolerant design procedures for smart sandwich beam structures with structural control and health monitoring applications.