• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.411-416
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• 2006

Fault detection and diagnosis is the most important technology in condition-based maintenance(CBM) system that usually begins from collecting signatures of running machines using multiple sensors for subsequent accurate analysis. With the quick development in industry, there is an increasing requirement of selecting special sensors that are cheap, robust, and easy-installation. This paper experimentally investigated performances of four types of sensors used in induction motors faults diagnosis, which are vibration, current, voltage and flux. In addition, diagnostic effects of five popular classifiers also were evaluated. First, the raw signals from the four types of sensors are collected at the same time. Then the features are calculated from collected signals. Next, these features are classified through five classifiers using artificial intelligence techniques. Finally, conclusions are given based on the experiment results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1050-1053
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• 2001

There is great interest in developing magnetoresistance(MR) sensor, using ferromagnetic, electrically non-magnetic conducting and antiferromagnetic films, especially for the use in weak magnetic fields. Here, we report single and Wheatstone-bridge type of MR sensors made in Si(001)/HiO(300$\AA$)/NiFe bilayers. Angular dependence of MR profiles was measured in Si(001)/NiO(300$\AA$)/NiFe(450$\AA$) films as a function of an angle between current and applied field direction, also, linearity was determined. AMR characteristics of single MR sensors was well explained with single domain model. Good linearity in 45$^{\circ}$Wheatstone-bridge type of MR sensors consisting of 4 single MR sensors made in Si(001)/NiO(300$\AA$)/NiFe(450$\AA$) was shown in the range of about $\pm$50 Oe.

• Corrosion Science and Technology
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• v.11 no.6
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• pp.270-274
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• 2012

This study represents the result of corrosion monitoring on reinforced concrete specimens by means of multi-functional corrosion monitoring sensors. To confirm the effectiveness of the sensors, eight different kinds of condition were adopted. Test factors were corrosion potential, current, corrosion rate, resistivity, and temperature, which were monitored with the sensors. Through this study, judging corrosion of steel in concrete with single corrosion factor such as corrosion potential was difficult, because many other factors can have an influence on the reaction of corrosion. By using three different kinds of sensors, it could enhance the accuracy of corrosion monitoring.

• Journal of Astronomy and Space Sciences
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• v.36 no.3
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• pp.181-186
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• 2019

The attitude information of spacecraft can be obtained by the sensors attached to it using a star tracker, three-axis magnetometer, three-axis gyroscope, and a global positioning signal receiver. By using these sensors, the spacecraft can be maneuvered by actuators that generate torques. In particular, electromagnetic-torque bars can be used for attitude control and as a momentum-canceling instrument. The spacecraft momentum can be created by the current through the electrical circuits and coils. Thus, the current around the electromagnetic-torque bars is a critical factor for precisely controlling the spacecraft. In connection with these concerns, a solar-cell array can be considered to prevent generation of a magnetic dipole moment because the solar-cell array can introduce a large amount of current through the electrical wires. The maximum value of a magnetic dipole moment that cannot affect precise control is $0.25A{\cdot}m^2$, which takes into account the current that flows through the reaction-wheel assembly and the magnetic-torque current. In this study, we designed a 300-W solar cell array and presented an optimal wire-routing method to minimize the magnetic dipole moment for space applications. We verified our proposed method by simulation.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.901-904
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• 2005

Testing of mixed-signal circuit has become a difficult task for test engineers and efficient test solution to these problems are needed. In this paper a new specification-based mixed-signal test method called TSS(Time Slot Specification) using high performance current sensors and a novel test point selection technique without heavy computational overhead are proposed. External output and power nodes are used for test points and accessed by the current sensors in the ATE.

• Proceedings of the KOSOMBE Conference
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• v.1992 no.11
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• pp.130-135
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• 1992

In this paper a new cardiac output control method without pressure sensors is presented for the rotor-driven totally implantable TAH using motor-current wavelet analysis. Theoretical analysis and mock circulation system experiment results show that cardiac output of TAH, which is indeperdent of afterload and sensitively dependent to preload, is well controlled for the independently variable preload.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.8
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• pp.1186-1192
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• 2015

This paper proposes an economical method that the phase currents can be measured and reconstructed by means of the leg-shunt resistors in the 3-leg 2-phase vector-controlled inverter for 2-phase induction motor. In general, the phase currents of 2-phase induction motor have been measured using two Hall current sensors. However, because Hall current sensors are expensive, economically disadvantageous to apply in low power applications. The proposed method is verified by computer simulations and experiments to show the good performance of the vector control.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.2
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• pp.53-57
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• 2017

This papers propose a Hall-effect sensors position error compensation method in a sunroof system using a BLDC motor with a low-cost MCU. If the BLDC motor is controlled with this wrong position, the torque ripple and operating current can be increased and the average torque also decreases. Generally, sunroof system has characteristics that operate at constant load for several seconds. It is possible to find the minimum operating current value while changing the position of the Hall-effect sensor during the sunroof operation by using these characteristics. Therefore, propose a method to change the Hall-effect sensor position and find the minimum current value. The validity of the proposed algorithm is verified through experiments.

• Journal of Magnetics
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• v.21 no.4
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• pp.524-528
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• 2016

Eddy current (EC) sensor works based on the electromagnetic induction principle and has been widely applied in the industrial testing and evaluation due to its robustness and environmental adaptability. Meanwhile, tilt angle measurement is mainly based on the laser or visual method, which is strict with the measurement environment and not suitable for the industrial applications. In this paper, a novel tilt angle measurement method based on arrayed EC sensors is proposed. Both the simulation and experiments indicate that the measured error is approximately linear with tilt angle and the accuracy after compensation is $0.25^{\circ}$. In conclusion, this research cannot only broaden the scope of EC application, but also overcome the shortcomings of existing angle measurement methods.

• Smart Structures and Systems
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• v.13 no.6
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• pp.943-957
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• 2014

When subjected to fatigue loading, the main failure mode of partially prestressed concrete (PPC) structure is the fatigue fracture of tensile reinforcement. Therefore, monitoring and evaluation of the steel stresses/strains in the structure are essential issues for structural design and healthy assessment. The current study experimentally investigates the possibility of using fiber Bragg grating (FBG) sensors to measure the steel strains in PPC beams in the process of fatigue loading. Six full-scale post-tensioned PPC beams were exposed to fatigue loading. Within the beams, the FBG and resistance strain gauge (RSG) sensors were independently bonded onto the surface of tensile reinforcements. A good agreement was found between the recorded results from the two different sensors. Moreover, FBG sensors show relatively good resistance to fatigue loading compared with RSG sensors, indicating that FBG sensors possess the capability for long-term health monitoring of the tensile reinforcement in PPC structures. Apart from the above findings, it can also be found that during the fatigue loading, there is stress redistribution between prestressed and non-prestressed reinforcements, and the residual strain emerges in the non-prestressed reinforcement. This phenomenon can bring about an increase of the steel stress in the non-prestressed reinforcement.