• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2048-2053
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• 2005

The aim of this paper is to compensate hysteresis phenomena in Shape Memory Alloy (SMA) actuators by using numerical inverse Preisach model. This is used to design a controller that correct hysteresis effects and improve accuracy for the displacement of SMA actuators. Firstly, hysteresis is identified by numerical Preisach model implementation. The geometrical interpretation from first order transition curves is used for hysteresis modeling. Secondly, the inverse Preisach model is formulated and incorporated in open-loop control system in order to obtain desired input-output relationship with hysteresis reducing. The experimental results for hysteresis compensation by using this method are also shown in this paper.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.634-642
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• 2006

The aim of this paper is to increase the performance of hysteresis compensation for Shape Memory Alloy (SMA) actuators by using inverse Preisach model in closed-loop control system. This is used to reduce hysteresis effects and improve accuracy for the displacement of SMA actuators. Firstly, hysteresis is identified by numerical Preisach model implementation. The geometrical interpretation from first order transition curves is used for hysteresis modeling. Secondly, the inverse Preisach model is formulated and incorporated in closed-loop PID control system in order to obtain desired current-to-displacement relationship with hysteresis reducing. The experimental results for hysteresis compensation by using this method are also shown in this paper.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.5-10
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• 2005

We deal with the sliding mode control using the time delay estimation. The time delay estimation is able to weaken the need for obtaining a quantitative plant model analogous to the real plant so the sliding mode control with a time delay estimation (SMCTE) is very suitable for plant such as SMA actuators whose quantitative model is difficult to obtain. We have already studied the application of the time delay control (TDC) to SMA actuators in other literature. Based on the previous study on the TDC, we developed the gain tuning method for the SMCTE, which results were nearly the same as the TDC. With respect to the step response, the SMCTE proved its predominance in a comparison with other control schemes such as the PID control and the relay control. As well as the contribution of the above control methodology, the model identification for SMA actuators has also been studied. The dynamics for an SMA actuator was newly derived using the modified Liang's model. The derived dynamics showed a continuity at the change of the phase transformation process but the original Liang's model could not.

• Smart Structures and Systems
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• v.16 no.1
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• pp.183-194
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• 2015

Shape memory alloy (SMA) helical springs have found a large number of different applications in industries including biomedical devices and actuators. According to the application of SMA springs in different actuators, they are usually under tension and torsion loadings. The ability of SMAs in recovering inelastic strains is due to martensitic phase transformation between austenite and martensite phases. Stress or temperature induced martensite transformation induced of SMAs is a remarkable property which makes SMA springs more superior in comparison with traditional springs. The present paper deals with the simulation of SMA helical spring at room temperature. Three-dimensional phenomenological constitutive model is used to describe superelastic behavior of helical spring. This constitutive model is implemented as a user subroutine through ABAQUS STANDARD (UMAT), and the process of the implementation is presented. Numerical results show that the developed constitutive model provides an appropriate approach to captures the general behavior of SMA helical springs.

• Smart Structures and Systems
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• v.7 no.1
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• pp.1-13
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• 2011

It has been shown in the literature that active adjustment of the intake area of a jet engine has potential to improve its fuel efficiency. This paper presents the design and control of a novel proof-of-concept active jet engine intake using Nickel-Titanium (Ni-Ti or Nitinol) shape memory alloy (SMA) wire actuators. The Nitinol SMA material is used in this research due to its advantages of high power-to-weight ratio and electrical resistive actuation. The Nitinol SMA material can be fabricated into a variety of shapes, such as strips, foils, rods and wires. In this paper, SMA wires are used due to its ability to generate a large strain: up to 6% for repeated operations. The proposed proof-of-concept engine intake employs overlapping leaves in a concentric configuration. Each leaf is mounted on a supporting bar than can rotate. The supporting bars are actuated by an SMA wire actuator in a ring configuration. Electrical resistive heating is used to actuate the SMA wire actuator and rotate the supporting bars. To enable feedback control, a laser range sensor is used to detect the movement of a leaf and therefore the radius of the intake area. Due to the hysteresis, an inherent nonlinear phenomenon associated with SMAs, a nonlinear robust controller is used to control the SMA actuators. The control design uses the sliding-mode approach and can compensate the nonlinearities associated with the SMA actuator. A proof-of-concept model is fabricated and its feedback control experiments show that the intake area can be precisely controlled using the SMA wire actuator and has the ability to reduce the area up to 25%. The experiments demonstrate the feasibility of engine intake area control using an SMA wire actuator under the proposed design.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.11
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• pp.1-6
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• 2005

In this research, the thermomechanical responses of shape memory alloy(SMA) actuators and their applications in the structures combining strip SMA actuators are investigated. The numerical algorithm of the 3-D SMA thermomechanical constitutive equations based on Lagoudas model is developed using user material(UMAT) subroutine written by FORTRAN. For the numerical results, the ABAQUS finite element program has been utilized with UMAT subroutine of the numerical algorithm of SMAs. The interactions between the host structure and SMA strip actuator are numerically investigated.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.167-174
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• 1995

This paper experimentally demonstrates the feasibility of using shape memory alloy(SMA) actuators in controlling structural vibrations of a flexible cantilevered beam. The dynamic characteristics of the SMA actuator are identified and integrated with the beam dynamics. Three types of control schemes; constant amplitude controller(CAC), proportional amplitude controller (PAC) and sliding mode controller(SMC) are designed. The CAC and PAC are determined on the basis of physical phenomenon of the SMA actuator, while teh SMC is formulated in a mathematical manner. The proposed controllers are implemented and evaluated at various operating condirions by investigating the control level of suppression in transient vibration.

• Composites Research
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• v.12 no.3
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• pp.55-65
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• 1999

In this paper, the thermal buckling and postbuckling behaviour of composite beam with embedded shape memory alloy (SMA) wires are investigated experimentally and analytically. The results of thermal buckling tests on uniformly heated, clamped, composite beam embedded with SMA wire actuators are presented and discussed in consideration of geometric imperfections, slenderness ratio of beam and embedding position of SMA wire actuators. The shape recovery force can reduce the thermal expansion of composite laminated beam, which result in increment of the critical buckling temperature and reduction of the lateral deflection of postbuckling behaviours. It is presented quantitatively on the temperature-load-deflection behaviour records how the shape recovery force affects the thermal buckling. The cross tangential method is suggested to calculate the critical buckling temperature on the temperature-deflection plot. Based on the experimental analysis, the new formula is also proposed to describe the critical buckling temperature of a laminated composite beam with embedded SMA wire actuators.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.4
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• pp.259-265
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• 2024

Shape memory alloy (SMA)-textile actuators have attracted significant attention across various fields, including soft robotics and wearable technology. These smooth actuators are developed by combining SMA and simple textile fibers and then knitting them into two loop patterns known as the knit (K-loop) and plain (P-loop) patterns. Both loops are distinguished by opposite bending characteristics owing to loop head geometry. However, the knitting processes for these actuator sheets require expertise and time, resulting in high production costs for knitted loop actuation sheets. This study introduces a novel method by which to assess the strain in SMA textile-based actuators, which experience large deformations when subjected to voltage. Owing to the highly nonlinear constitutive equations of the SMA material, developing an analytical model for numerical analysis is challenging. Therefore, this study employs a novel approach that utilizes a linear constitutive equation to analyze large deformations in SMA material with nonlinear geometry considerations. The user-defined material (UMAT) subroutine integrates the linear constitutive equation into the ABAQUS software suite. This equivalent unit cell (EUC) model is validated by comparing the experimental bending actuation results of K-loops and P-loops.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.2
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• pp.147-152
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• 2016

Shape Memory Alloys (SMAs) undergo changes in shape and hardness when heated or cooled, and do so with great force. Since wire-type SMAs contract in length when heated and pull with a surprisingly large force and move silently, they can be used as actuactors which replace motors. These SMA actuators can be heated directly with electricity and can be used to create a wide range of motions. This paper presents the mechanical design and control for a three fingered, six degree-of-freedom robotic hand actuated by SMA actuators. Each finger has two joints and each joint is actuated with two tendons in the antagonistic manner. In order to create the sufficient force to make the smooth motion, the tendon is composed of two SMA actuators in parallel. For controlling the current to heat the SMA actuators, PWM drivers are used. In experiments, the antagonistic interaction of fingers are evaluated.