• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.5
• /
• pp.51-57
• /
• 2011

The lightweight and compact actuator with high power is required to perform motion with multiple degrees of freedom. To reduce the size and inertia of a robot manipulator, the mechanical transmission system is used. The shape memory alloy(SMA) is similar to the muscle-tendon-bone network of a human hand. However, there are some drawback and nonlinearity, such as the hysteresis and the stress dependence. In this paper, the design of the underactuated robot hand is studied. The 3-finger dexterous hand is driven by the SMA actuator using segmental mechanism. This digital approach enables to overcome the nonlinearity of SMA wire. The translational displacement of SMA actuator required to bend a phalanx of the underactuated robot hand is estimated and the bending angle of the underactuated robot hand according to input displacement of SMA actuator is predicted by the multi-body dynamic analysis.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.11
• /
• pp.1128-1136
• /
• 2012

This paper analyzes the vibration characteristics of an optical pickup actuator, which has six wire-suspensions and is used in optical disc drives(ODDs). The vibration characteristics of the actuator is mathematically described by analyzing its beam configuration and motion condition confined to lateral and longitudinal directions of the beams. The accuracy of the vibration characteristics is proved by comparing mode frequencies with a finite element analysis. Finally, it is shown that mode frequencies and shapes can be modified by changing design parameters in mathematical expressions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.04a
• /
• pp.73-78
• /
• 2013

In this paper, the vibration for a pickup actuator is described by mathematically analyzing its suspension configuration and motion, confined to lateral and torsional directions of suspensions. In order to prove the accuracy of this result, it is compared to a finite element analysis. Also it is shown that modal frequencies can be modified by changing design parameters in mathematical motion expressions.

• Structural Engineering and Mechanics
• /
• v.77 no.2
• /
• pp.167-177
• /
• 2021

Due to various benefits such as unlimited degrees of freedom, environment adaptability, and safety for humans, engineers have used soft materials with hyperelastic behavior in various industrial, medical, rescue, and other sectors. One of the applications of these materials in the fabrication of bending soft actuators (SA) is that they have eliminated many problems in the actuators such as production cost, mechanical complexity, and design algorithm. However, SA has complexities, such as predicting and monitoring behavior despite the many benefits. The first part of this paper deals with the prediction of SA behavior through mathematical models such as Ogden and Darijani, and its comparison with the results of experiments. At first, by examining different geometric models, the cubic structure was selected as the optimal structure in the investigated models. This geometrical structure at the same pressure showed the most significant bending in the simulation. The simulation results were then compared with experimental, and the final gripper model was designed and manufactured using a 3D printer with silicone rubber as for the polymer part. This geometrical structure is capable of bending up to a 90-degree angle at 70 kPa in less than 2 seconds. The second section is dedicated to monitoring the bending behavior created by the strain sensors with different sensitivity and stretchability. In the fabrication of the sensors, silicon is used as a soft material with hyperelastic behavior and carbon fiber as a conductive material in the soft material substrate. The SA designed in this paper is capable of deforming up to 1000 cycles without changing its characteristics and capable of moving objects weigh up to 1200 g. This SA has the capability of being used in soft robots and artificial hand making for high-speed objects harvesting.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.1
• /
• pp.119-125
• /
• 1997

This paper deals with an experimental investigation on an active vibration control of ahybrid smart structure(HSS) via an electro-rheological fluid actuator(ERFA) and a piezoelectric film actuator(PFA). Firstly, an HSS is constructed by inserting a silicone oil-based electro-rheological fluid into a hollow can- tilevered beam and perfectly bonding piezoelectric films ofn the upper and lower surfaces of the beam as an actuator and a sensor, respectively. The control scheme of the ERFA tuning stiffness and damping charac- teristics of the HSS with imposed electric fields is formulated as a function of excitation frequencies on the basis of field-dependent respnses. On the other hand, as for the control scheme of the PFA permitting control voltages to generate axial forces or bending moments for suppressing deflections of the HSS, a neuro sliding mode controller(NSC) is employed. Furthermore, an experimental implementation activating the ERFA and the PFA independently is established to carry out an active vibration control in both the transient and forced vibrations. The experimental results exhibit a superior ability of the gtbrid actuation system to tailor elastodynamic response characteristics of the HSS rather than a single class of actuator system alone.

• Journal of Institute of Control, Robotics and Systems
• /
• v.18 no.3
• /
• pp.168-174
• /
• 2012

This paper presents a bending propagating actuation using SMA (Shape Memory Alloy) spring for an effective shape transition of a flytrap-inspired soft morphing structure. The flytrap-inspired soft morphing structure is made from unsymmetric CFRP (Carbon Fiber Reinforced Prepreg) structure which shows bi-stability and snap-through phenomenon. For a thin and large curved bistable CFRP structure, SMA spring is more acceptable than SMA wire and piezoelectric actuator which used in previous investigations. A bending propagating actuation is proposed which can induce snap-through of the bi-stable CFRP structure effectively. From this research, effective shape transition of soft morphing structure is possible.

• Journal of Aerospace System Engineering
• /
• v.14 no.6
• /
• pp.91-99
• /
• 2020

This study proposes a finite element (FE) model for predicting the bending strength of small gears used in electro-mechanical actuators for aircraft. First, a strain gauge was attached to the tooth root of test gear, and the strain was measured. Subsequently, the FE model was applied to calculate the strain of the test gear, and the modeled strain was compared with the experimental strain. The results confirmed that the FE strain was very close to the experimental strain and the FE model was valid. This FE model was extended to the bending strength analysis of several small gear tooth models. The bending strengths of all the tooth models were almost identical to the ISO theoretical bending strength. Finally, the FE model was validated and the reliability of the modeled bending strength was evaluated through the strain measurement experiment.

• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.10
• /
• pp.865-871
• /
• 2015

This study was conducted in order to develop a finger exoskeleton system using ionic polymer metal composites (IPMCs) as the actuator and sensor in a hybrid structure. To use the IPMC as an actuator producing large force, a first order transfer function was obtained using results from a block force for DC excitation that applied to two IPMCs of 20mm-width, 50mm-length, and 2.4mm thickness together. After which the validation of 200gf control with anti-windup PI controller was confirmed. A 5mm-width, 50mm-length, 0.6mm-thickness of IPMC was also modeled as a sensor for tip displacement. As a result, the IPMC sensor could been utilized as a trigger role for the actuator. Finally, an IPMC sensor and actuator were installed on the joint of a single DOF exoskeleton in the hybrid structure, and test for the control of 40gf of block force and predefined sequence of motion was performed.

• Ceramist
• /
• v.23 no.1
• /
• pp.16-26
• /
• 2020

Recently, polymer-metal composite (IPMC)-based ionic artificial muscle has been drawing a huge attention for its excellent soft actuator performance having outstanding soft actuator performance with efficient conversion of electrical energy to mechanical energy under low working voltage. In addition, light, flexible and soft nature of IPMC and high bending strain response enabled development of versatile sensor application in association with soft actuator. In this paper, current issues of IPMC were discussed including standardizing preparation steps, relaxation under DC bias, inhibiting solvent evaporation, and improving poor output force. Solutions for these drawbacks of IPMC have recently been suggested in recent studies. After following explanation of the IPMC working mechanism, we investigate the main factors that affect the operating performance of the IPMC. Then, we reviewed the optimized IPMC actuator fabrication conditions especially for the preparation process, additive selection for a thicker membrane, water content, solvent substitutes, encapsulation, etc. Lastly, we considered the pros and cons of IPMCs for sensor application in a theoretical and experimental point of view. The strategies discussed in this paper to overcome such deficiencies of IPMCs are highly expected to provide a scope for IPMC utilization in soft robotics application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.3
• /
• pp.250-254
• /
• 2006

Hetero-junction sheet actuator composed of carbon nanotubes and $V_{2}O_5$ nanowires were demonstrated in a bimetal configuration. The successive filtration of $V_{2}O_5$ nanowire solution followed by carbon nanotube dispersed water solution in the same way produced a dark-gray colored sheet. A significant actuation was observed in sodium chloride electrolyte solution with a bending direction to the carbon nanotube side at the positive bias voltage against the copper counter-electrode. As the frequency of the applied voltage increased, the amplitudes decreased, indicating a rather slow response of the hetero-film actuator in the electrolyte solution. The hybrid structure enabled an easy fabrication of the film actuator with the enhanced efficiencies.