• Journal of Institute of Control, Robotics and Systems
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• v.2 no.3
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• pp.181-187
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• 1996

A frictionless positioning device using cone-shaped active magnetic bearings(AMBs) is developed, which is driven by a brushless DC motor equipped with resolver. The cone-shaped AMB feature that the structure is simple and yet the five d.o.f. rotor motion is controlled by four magnet pairs. A linearized dynamic model, which accounts for the relationship between input voltage and output current in the cone-shaped magnet, is developed and the azimuth motion of the frictionless positioning device is modeled as the second order system. The feedback controller is designed by using linear quadratic regulator with integral action optimal control law so that the cone-shaped AMB system is stabilized and the frictionless positioning device gets the zero steady state. It is observed that the linearized dynamic model is adequate and the frictionless positioning device can achieve the tracking accuracy within the sensor resolution.

• Smart Structures and Systems
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• v.4 no.6
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• pp.741-757
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• 2008

The research field of structural control has evolved from the development of passive devices since 1970s, through the intensive investigation on active systems in 1980s, to the recent studies of semi-active control systems in 1990s. Currently semi-active control is considered most promising in civil engineering applications. However, actual implementation of semi-active devices is still limited due mainly to their system maintenance and associated long-term reliability as a result of power requirement. In this paper, the concept of functionally upgraded passive devices is introduced to streamline some of the state-of-the-art researches and guide the development of new passive devices that can mimic the function of their corresponding semi-active control devices for various applications. The general characteristics of this special group of passive devices are discussed and representative examples are summarized. Their superior performances are illustrated with cyclic and shake table tests of two example devices: mass-variable tuned liquid damper and friction-pendulum bearing with a variable sliding surface curvature.

• Journal of the Korean Society of Safety
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• v.32 no.6
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• pp.81-88
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• 2017

This study deals with the optimal design of a hybrid control system composed of a combination of active control system and passive control system for effective seismic performance improvement of two adjacent structures. The proposed hybrid control system adopts a configuration of installing an active control device in one building and connecting two adjacent structures with a passive control device so that the one-side active control force can be bi-directionally applied to both buildings through the passive connecting devices. In order to derive the optimal performance of the proposed system, the design parameters of the passive and active control systems were searched using the genetic algorithm. Numerical simulations of 10-story and 8-story buildings have been performed to verify the effectiveness of the proposed technique. For the purpose of comparison, the conventional independent control system with two identical active control systems being installed separately for each structure was also optimally designed and its seismic response has been evaluated as well. From the comparative results of the two control systems, it is demonstrated that the proposed hybrid control system requires larger control force for its one-side active control device than the conventional independent control system does for each of both-side active devices, but quite less than the total control force required for both-side devices of the independent control system, while maintaining similar seismic performance. Therefore, the proposed system is more economical and reliable than the conventional independent control system with two identical active devices.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.282-286
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• 2000

In this paper, magneto-rheological(MR) damper is studied for vibration control of large infra structures under earthquake. Generally, active control devices need a large control force and a high power supply system to reduce the vibration effectively. Large and miss tuned control force may induce the dangerous situation such that the generated large control force acts to amplify the structural vibration. Recently, to overcome the weaknesses of the active control, the semi-active control method is suggested by many researchers. Semi-active control uses the passive control device of which the characteristics can be modified. Control force of the semi-active device is not generated from the actuator with power supply. It is generated as a dynamic reaction force of the device same as in the passive control case, so the control system is inherently stable and robust. Unlike the case of passive control, control force of semi-active control is adjusted depending on the measured response of the structure, so the vibration can be reduced more effectively against various unknown environmental loads. Magneto-rheological(MR) damper is one of the semi-active devices. Dynamic characteristics of the MR material can be changed by applying the magnetic fields. So the control of MR damper needs only small power. Response time of MR to the input voltage is very short, so the high performance control is possible. MR damper has a high force capacity so it is adequate to the vibration control of large infra structure. Because MR damper has a nonlinear property, normal control method used in active control may not be effective. Clipped optimal control, modified bang-bang control etc. have been suggested to MR damper by many researchers. In this study, sliding mode fuzzy control(SMFC) is applied to MR damper. Genetic algorithm is used for the controller tuning. To verify the applicability of MR damper and suggested algorithm, numerical simulation on the aseismic control is carried out. Simulation model is three-story building structure, which was used in the paper of Dyke, et al. The control performance is compared with clipped optimal control. The present results indicate that the SMFC algorithm can reduce the earthquake-induced vibration very effectively.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2336-2338
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• 1998

This paper describes an active laser sensing device using laser diodes and optic devices. It is able to detect near targets existed in $360^{\circ}$ directions simultaneously with effectiveness and reliability. This sensing device consists of four laser transmitters and four receivers. Only four transmitter/receiver channels of this near range sensing device are capable of $360^{\circ}$ coverage. The usefulness of this sensing device is confirmed through some experiments for the mock-up targets.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.98-101
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• 2012

I studied the stability of organic photovoltaic cells in terms of P3HT:PCBM-71 blend ratio as a function of storage time. I obtained the best cell performance by optimizing the blend ratio of electron donor and electron acceptor within the active layer. In this study, I found that the more the P3HT:PCBM ratio increases within the active layer, the more the cell efficiency decreases as the storage time increases. As a result, the best optimized blend ratio was the 1:0.6 ratio of P3HT:PCBM-71, and cell efficiency of the device with the 1:0.6 blend ratio was 4.49%. The device with the best cell efficiency showed good stability.

• Electronics and Telecommunications Trends
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• v.32 no.6
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• pp.27-39
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• 2017

A variety of medical devices are utilized to repair or help injured body functions after accidental injury(such as a traffic accident), population aging, or disease. Such medical devices are being actively researched and developed in portable form, skin patchable type, and further, implantable form. In the future, active implantable medical devices for neuro and brain sciences are expected to be developed. Active implantable medical devices that detect brain signals and control neurology for a wider understanding of human cognition and nerve functions, and for an understanding and treatment of various diseases, are being actively pursued for future use. In this paper, the core elements of implantable devices that can be applied to neuro and brain sciences are classified into electrode technologies for bio-signal acquisition and stimulation, analog/digital circuit technologies for signal processing, human body communication technologies, wireless power transmission technologies for continuous device use, and device integration technologies to integrate them. In each chapter, the latest technology development trends for each detailed technology field are reviewed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.351.1-351.1
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• 2014

In this study, we prepared the solution-based In-Ga-Zn oxide thin film transistors (IGZO TFTs) of multistacked active layer and characterized the gate bias instability by measuring the change in threshold voltage caused by stacking. The solutions for IGZO active layer were prepared by In:Zn=1:1 mole ratio and the ratio of Ga was changed from 20% to 30%. The TFTs with multistacked active layer was fabricated by stacking single, double and triple layers from the prepared solutions. As the number of active layer increases, the saturation mobility shows the value of 1.2, 0.8 and 0.6 (). The electrical properties have the tendency such as decreasing. However when gate bias VG=10 V is forced to gate electrode for 3000 s, the threshold voltage shift was decreased from 4.74 V to 1.27 V. Because the interface is formed between the each layers and this affected the current path to reduce the electrical performances. But the uniformity of active layer was improved by stacking active layer with filling the hole formed during pre-baking so the stability of device was improved. These results suggest that the deposition of multistacked active layer improve the stability of the device.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_3
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• pp.1315-1323
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• 2023

Rehabilitation assistive devices not only assist the rehabilitation therapy and daily life of the disabled and the elderly, but also assist the labor of their caregivers, so various functions are required to improve their quality of life. In this study, a design method considering its practicality is introduced for an active rehabilitation assistive device that can perform both standing and walking assistance by driving various actuators. For this purpose, the force required to assist standing was calculated using statics with the body segmentation method. Also, the overturning stability of the device was verified for various physical conditions and postures. The actuator in the active rehabilitation assistive device was operated by a patient using a graphical user interface in an embedded computer and a touch panel for easy usage. The detailed design was performed for implementation through the help of 3D-CAD and the finite element analysis, and a prototype was produced. Finally, it was proven that the design goal was satisfied by experimental validation.

• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.15-20
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• 2019

Inspection and measurement of surface quality is one of the most critical processes for manufacturing products such as semiconductor wafers, sapphire substrates, and display panels. The vibrations of the inspection and measurement devices are supposed to be the most dominant factors for severe measurement errors and longer measuring time. In this study, dynamic characteristics of an inspection and measurement device are analyzed through frequency response experiment and computer simulation to obtain parameters such as frequencies, magnitudes, mode shapes, and periods of vibrations. And then an active damper which consists of sensor, interface board, and actuator is designed based on the parameters to formulate the most effective reaction signal to suppress the vibrations which is generated by an interface board, and provided by an actuator. If the vibrations are measured by the sensor, the active damper immediately generates and provides the corresponding reaction signal to inspection and measurement device. The result shows that the active damper can suppress structural vibrations effectively and reduce measuring time of the device and enhance the productivity.