• Smart Structures and Systems
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• v.14 no.5
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• pp.765-784
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• 2014

In comparison with conventional shape memory actuated structures, antagonistic shape memory alloy (SMA) actuators permits a fully reversible two-way response and higher response frequency. However, excessive internal stress could adversely reduce the stroke of the actuators under repeated use. The two-way shape memory effect might further decrease the range of the recovered strain under actuation of an antagonistic SMA actuator unless additional components (e.g., spring and stopper) are added to regain the overall actuation capability. In this paper, the performance of all four possible types of SMA actuation schemes is investigated in detail with emphasis on five key properties: recovered strain, cyclic degradation, response frequency, self-sensing control accuracy, and controllable maximum output. The testing parameters are chosen based on the maximization of recovered strain. Three types of these actuators are antagonistic SMA actuators, which drive with two active SMA wires in two directions. The antagonistic SMA actuator with an additional pair of springs exhibits wider displacement range, more stable performance under reuse, and faster response, although accurate control cannot be maintained under force interference. With two additional stoppers to prevent the over stretch of the spring, the results showed that the proposed structure could achieve significant improvement on all five properties. It can be concluded that, the last type actuator scheme with additional spring and stopper provide much better applicability than the other three in most conditions. The results of the performance analysis of all four SMA actuators could provide a solid basis for the practical design of SMA actuators.

• Transactions of the Society of Information Storage Systems
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• v.5 no.1
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• pp.1-7
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• 2009

Recently, the growing market demand for small and slim mobile phone cameras requires the size reduction of the camera module. In this paper, an auto-focusing actuator for camera phones is proposed by converting the rotational motion by a rotary VCM actuator into the linear motion using a novel cam structure. This new concept for auto-focusing module enables the reduction of the module thickness and low power consumption. This paper presents the theoretical analysis and optimal design for VCM actuator, cam structure and preload spring. Finally, the experimental results using a prototype with the size of $9.9{\times}9.9{\times}5.9\;mm^3$ are compared with the theoretical predictions.

• Journal of Aerospace System Engineering
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• v.9 no.2
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• pp.7-12
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• 2015

In this paper, we report a non-explosive separation device for a small satellite which utilize a shape memory alloy actuator and spring clamp. In order to increase the preload, the proposed device employs spring clamp that can generate high toque when the shape memory alloy actuator makes the cylinder key unlatch a holding ball effectively. Owing to simple design of separation device configuration, we could obtain good repeatability(up to 30 times activation). Conclusively, we could develop a non-explosive separation device which can reliably activate within 1.2 sec under high preload(up to 300kgf).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.12
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• pp.1246-1253
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• 2007

The recent issue of optical pickup actuators is to apply optical storage devices to mobile devices such as a cellular phone and PDA. It requires actuators to become smaller than conventional types. As the size becomes smaller, the magnetic force is reduced and the assembly of optical pickup actuators becomes more difficult. In addition, its dynamic characteristics are changed. In this paper, methods to improve magnetic forces and dynamic characteristics are suggested and the optimal result of the plate spring design is obtained. A diamond shape magnet and the fine pattern coil (FPC) are used to improve magnetic forces and damping elements are attached to decrease the peak magnitude of the mode instead of using structural damping, mostly for the purpose of improving the accuracy of the finite element simulation. To get more stable dynamic characteristics than conventional ones, a plate spring is applied to the optical pickup actuator and it is optimized with topology and parameter optimization to obtain the concept and the detail design, respectively.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.3
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• pp.10-15
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• 2011

The separation actuator for the small satellite should fix satellite appendages with high clamping force. After operation, it has to be separated from the satellite body without any damage on satellite system and release the appendages such as a solar panel and an antenna successfully. Therefore, we invent a non-explosive separation actuator for the small satellite which generates low shock and is resettable. In order to confirm performance of the proposed separation actuator, we carried out experiments for separation time, maximum preload for activation, and shock level.

• Smart Structures and Systems
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• v.24 no.3
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• pp.361-377
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• 2019

The stiffness of shape memory alloy (SMA) spring while in actuation is represented by an empirical model that is derived from the logistic differential equation. This model correlates the stiffness to the alloy temperature and the functionality of SMA spring as active variable stiffness actuator (VSA) is analyzed based on factors that are the input conditions (activation current, duty cycle and excitation frequency) and operating conditions (pre-stress and mechanical connection). The model parameters are estimated by adopting the nonlinear least square method, henceforth, the model is validated experimentally. The average correlation factor of 0.95 between the model response and experimental results validates the proposed model. In furtherance, the justification is augmented from the comparison with existing stiffness models (logistic curve model and polynomial model). The important distinction from several observations regarding the comparison of the model prediction with the experimental states that it is more superior, flexible and adaptable than the existing. The nature of stiffness variation in the SMA spring is assessed also from the Dynamic Mechanical Thermal Analysis (DMTA), which as well proves the proposal. This model advances the ability to use SMA integrated mechanism for enhanced variable stiffness actuation. The investigation proves that the stiffness of SMA spring may be altered under controlled conditions.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.673-675
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• 2002

In this paper. the lumped electrical circuit approach of mass/spring system is used to model the mechanical aspects according to the frequency. Therefore, the mass/spring system can be dealt with here and linked with the equivalent circuit of electric linear oscillatory actuator(LOA). Analysis models are double-coil type linear compressor for stirling refrigerator. The compressor consists of the moving coil LOA, piston, and spring. The electro-mechanical system with mass and spring can be represented using the lumped electrical circuit. We present the system impedance and dynamics of moving coil linear compressor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.3
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• pp.242-247
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• 2016

This work investigates the performances of active hood lift system(AHLS) activated by two different operating methods through the experimental test. In the AHLS, the deployment time of the system and decrement of pedestrian injury are the most important factors for the pedestrian safety during the pedestrian-vehicle impact. After introducing the working principle of AHLS using spring actuator and gunpowder actuator, the deployment time of AHLS and decrement of pedestrian injury are evaluated by the experimental test. It has been identified that the gunpowder actuator can provide a faster deploying time of AHLS.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.615-617
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• 1997

This paper reports experimental results on the fabrication and analysis of millimeter-sized bending actuators for active catheter by use of the shape memory alloy spring and the flexible beam. The major components of micro actuator are shape memory alloy spring, stainless steel strip and two acryl links. The micro actuator with the diameter of 2.0 mm and the length of 25 mm has been fabricated and characterized for the possible application to the micro active catheters. The measured maximum angle is $60^{\circ}$ and the response time is 5 sec.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.905-906
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• 2006

This paper deals with the dynamic simulations and experiments of moving-coil linear actuator with/without spring. Dynamic simulation algorithm is established from the voltage and motion equation. Finally, for various values of frequency, dynamic simulation results for characteristics of current and displacement of moving-coil linear actuator with and without spring are presented and confirmed through the experiments.