• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.943-950
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• 2008

A novel nondestructive testing (NDT) system, which is able to detect a crack with high speed and high spatial resolution, is urgently required for inspecting small cracks on express train wheels. This paper proposes a high speed scan type magnetic camera, which uses the multiple amplifying circuits and the crack indicating pulse output system. The linearly integrated Hall sensors are arrayed in parallel, and the Hall voltages from each sensor in the scanning direction are obtained and amplified. High-speed NDT can be achieved by using the exclusive analog-digital converter and micro-processor because the ${\partial}\;V_H/\;{\partial}$ x value, which provides the most important crack information, can be obtained by buffering and calculating. The effectiveness of the novel method was verified by examine using cracks on the wheel specimen model.

• The Journal of the Acoustical Society of Korea
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• v.21 no.2E
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• pp.71-80
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• 2002

This paper suggests the Cardioid beamforming algorithm of the doublet sensors employing DIFAR (directional frequency analysis and recording) sensor signals in the frequency domain. The algorithm enables target bearing estimation using the signals from directional sensors. The algorithm verifies its applicability by successfully estimating bearings of a target projecting ten narrow-band signals in shallow water. The estimated bearings agree very well with those from GPS (global positioning system) data. Assuming the bearings from GPS data to be real values, the estimation errors are analyzed statistically. The histogram of estimation errors in each frequency have Gaussian shape, the mean and standard deviation dropping in the ranges -1.1°∼ 6.7°and 13.3∼43.6°, respectively. Estimation errors are caused by SNR (signal to noise ratio) degradation due to propagation loss between the source and receiver, daily fluctuating geo-magnetic fields, and non-stationary background noises. If multiple DIFAR systems are employed, in addition to bearing, range information could be estimated and finally localization or tracking of a target is possible.

• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.3
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• pp.11-17
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• 2017

The aerial support air sculptures currently exhibited in indoor spaces are similar to simple ad balloons, using multiple rope strands. Users now want more advanced unfixed sculptures, and hope these will develop into buoyant sculptures that can maintain the attitudes that users want on their own. This study investigated an attitude control system for unfixed levitation sculptures that can levitate with no rope and continuously maintain a certain attitude at a height specified by the user. To facilitate levitation, the exterior part of the sculpture was made of lightweight fibers, and the interior part was filled with helium gas. The controller was composed of a microprocessor of the dsPIC30F line from microchip, gyro, acceleration, and earth magnetic field sensors, and a highly efficient brushless DC (BLDC) electric motor. The attitude and position control system requires scheduling considering the trajectories of the sculpture and the control system, because the roles of the overall components are more important than those of a single controller. Furthermore, the system was designed like a fusion system that is expanded and controlled as a total controller, because it is interconnected with various sensors. The attitude control system of buoyant sculptures was implemented in this study, such that it can actively cope with the position, direction, stopping, and time aspects. The system performance was then evaluated.

• Smart Media Journal
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• v.1 no.4
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• pp.18-26
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• 2012

The increase of the number of smartphone applications has enforced the importance of new user interface emergence and has raised the interest of research in the convergence of multiple sensors. In this paper, we propose a method for the convergence of acceleration, magnetic and gyro sensors to recognize the gesture from motion of user smartphone. The proposed method first obtain the 3D orientation of smartphone and recognize the gesture of hand motion by using HMM(Hidden Markov Model). The proposed method for the representation for 3D orientation of smartphone in spherical coordinate was used for quantization of smartphone orientation to be more sensitive in rotation axis. The experimental result shows that the success rate of our method is 93%.

• Progress in Superconductivity
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• v.14 no.2
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• pp.82-86
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• 2012

A sensitive eight-channel high-Tc Superconducting Interference Device (SQUID) detection system for magnetic contaminant in a lithium ion battery anode was developed. Finding ultra-small metallic foreign matter is an important issue for a manufacturer because metallic contaminants carry the risk of an internal short. When contamination occurs, the manufacturer of the product suffers a great loss from recalling the tainted product. Metallic particles with outer dimensions smaller than 100 microns cannot be detected using a conventional X-ray imaging system. Therefore, a highly sensitive detection system for small foreign matter is required. We have already developed a detection system based on a single-channel SQUID gradiometer and horizontal magnetization. For practical use, the detection width of the system should be increased to at least 65 mm by employing multiple sensors. In this paper, we present an 8-ch high-Tc SQUID roll-to-roll system for inspecting a lithium-ion battery anode with a width of 65 mm. A special microscopic type of a cryostat was developed upon which eight SQUID gradiometers were mounted. As a result, small iron particles of 35 microns on a real lithium-ion battery anode with a width of 70 mm were successfully detected. This system is practical for the detection of contaminants in a lithium ion battery anode sheet.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.3
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• pp.232-239
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• 2008

The position sensors used in a magnetic bearing system are desirable to provide some degree of fault-tolerance as the rotor position is necessary for the feedback control to overcome the open-loop instability. In this paper, we propose an inductive position sensor that can cope with a partial fault in the sensor. The sensor has multiple poles which can be combined to sense the in-plane motion of the rotor. When a high-frequency voltage signal drives each pole of the sensor, the resulting current in the sensor coil contains information regarding the rotor position. The signal processing circuit of the sensor extracts this position information. In this paper, we used the magnetic circuit model of the sensor that shows the analytical relationship between the sensor output and the rotor motion. The multi-polar structure of the sensor makes it possible to introduce redundancy which can be exploited for fault-tolerant operation. The proposed sensor is applied to a magnetically levitated turbo-molecular vacuum pump. Experimental results validate the fault-tolerance algorithm.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.4
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• pp.219-228
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• 2013

The surveillance imaging equipments are functioning to observe the shape of the target in real time or to measure its location precisely. The roles of such equipments are becoming more important in today's weapon systems.The aforementioned imaging equipments can be classified based on the modes of operations such as fixed, installed on cars, or composite of those. Also, according to different concepts of sensor operation, a separate type uses independent housing for each sensor whereas in a composite type a set of multiple sensors are housed into a unit altogether. The sensors in general have magnetism, thereby introducing the possible negative effects, particularly in the composite types, in locating the reference position, which is carried out by the digital compass. The use of shielding material/housing could be an option but results in increased weight and reduced portability, restricting its use in composite type equipments. As such, the objective of this paper is to study on how to reduce such magnetic effects on the position location. To do so, in the absence of magnetic shielding, a variety of sensor positions were first modeled. By combing the result with the fact that the functions of PAN & Tilt are used in the equipments, a new position location algorithm is proposed. The use of the new algorithm can automate the position location process as compared to the manual process of the existing approach. In the algorithm developed, twelve locations are measured in connection with both the azimuth and elevation angles in comparison to the six locations alone around the azimuth angle. As a result, it turns out that the measurement range has been widened but the measurement time reduced. Also, note that the effect of errors the operators may make during measurement could be reduced.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.2
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• pp.169-184
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• 2002

In order to extract bearing information from the directional sensors of DIFAR(directional frequency analysis and recording) that is a kind of passive sonobuoy, the cardioid beamforming algorithm applicable to DIFAR system was studied in the frequency domain. the algorithm uses narrow-band signals propagated though the media from the acoustic sources such as ship machineries. The proposed algorithm is expected to give signal to noise ratio of 6dB when it uses the maximum response axis(MRA) among the Cardioid beams. The estimated bearings agree very well with those from GPS data. Assuming the bearings from GPS data to be real values, the estimation errors are analyzed statistically. The histogram of estimation errors in each frequency have Gaussian shape, the mean and standard deviation dropping in the ranges -1.1~$6.7^{\circ}$ and 13.3~$43.6^{\circ}$, respectively. Estimation errors are caused by SMR degradation due to propagation loss between the source and receiver, daily fluctuating geo-magnetic fields, and non-stationary background noises. If multiple DIFAR systems are employed, in addition to bearing, range information could be estimated and finally localization or tracking of a target is possible.

• Journal of Power System Engineering
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• v.20 no.3
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• pp.22-28
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• 2016

Energy consumption rapidly increases with industrial development. therefore an interest in the efficiency of various power converters is increasing. Especially, the field of high-efficiency small motors widely distributed for industrial and family use is considered a very important field in terms of efficient energy usage, and accordingly, in the field of small electric equipment, the use of BLDC that allows high-efficiency drive in an inductor gradually increases. However, for the BLDC drive, information on the position of the rotor is essential. Both methods using a magnetic encoder and an optical encoder to detect the information on the position of the rotor obtain the information by three position sensitive devices, and if any one of these position sensitive devices fails to function, no positional information can be obtained, so there is a limitation in implementing a position sensor with high reliability. In the paper, proposes a new type of encoder that can obtain the positional information on the position of the rotor using a single position sensor in order to overcome the issues that it has to use numerous signal flows and that the reliability is reduced for the acquisition of positional information generated by using multiple position detectors. The encoder in the proposed method replaced the function of generating positional information from multiple sensors with the shape of the encoder plate and the capture function of MICOM. In order to verify the validity of the position detection technique by the proposed encoder, a prototype was produced, and an experiment using the capture function of DSP was conducted through this.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.579-584
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• 2008

A novel nondestructive testing (NDT) system, which is able to detect a crack with high speed and high spatial resolution, is urgently required for inspecting small cracks on express train wheels. This paper proposes an improved signal processing circuits, which uses the multiple amplifying circuits and the crack indicating pulse output system of the previous scan-type magnetic camera. Hall sensors are arrayed linearly, and the wheel is rotated with static speed in the vertical direction to sensor array direction. Each Hall voltages are amplified, converted and immediately operated by using, amplifying circuits, analog-to-digital converters and $\mu$-processor, respectively. The operated results, ${\partial}V_H/{\partial}t$, are compared with a standard value, which indicates a crack existence. If the ${\partial}V_H/{\partial}t$ is larger than standard value, the pulse signal is output, and indicates the existence of crack. The effectiveness of the novel method was verified by examine using cracks on the wheel specimen model.