• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.2
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• pp.143-149
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• 2021

BLDC motors are getting better performance due to the improvement of material technology including high performance of permanent magnets, advancement of driving IC technology with high integration and high functionality, and improvement of assembly technology such as high point ratio. While having the advantage of such a square wave driven BLDC motor, interest in the design and development of a square wave driven BLDC permanent magnet motor and development of a position detection circuit and driver is increasing in order to more meet the needs of users. However, in spite of the cost and functional advantages due to reduced efficiency, switching loss and vibration, noise, etc., the application is somewhat limited. Therefore, in this paper, we study a position detection circuit that generates a sinusoidal signal in proportion to the magnetic flux of a BLDC motor rotor using a Hall Effect Sensor that generates a sinusoidal wave to increase the efficiency of the motor, reduce ripple, and drive a sinusoidal current with excellent speed and torque characteristics.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.1
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• pp.75-80
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• 2021

Positioning technology is performing important functions in augmented reality, smart factory, and autonomous driving. Among the positioning techniques, the positioning method using beacons has been considered a challenging task due to the deviation of the RSSI value. In this study, the position of a moving object is predicted by training a neural network that takes the RSSI value of the receiver as an input and the distance as the target value. To do this, the measured distance versus RSSI was collected. A neural network was introduced to create synthetic data from the collected actual data. Based on this neural network, the RSSI value versus distance was predicted. The real value of RSSI was obtained as a neural network for generating synthetic data, and based on this value, the coordinates of the object were estimated by learning a neural network that tracks the location of a terminal in a virtual environment.

• Journal of IKEEE
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• v.26 no.3
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• pp.488-493
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• 2022

In manufacturing sites, bearing fault in eletrically driven motors cause the entire system to shut down. Stopping the operation of this environment causes huge losses in time and money. The reason of this bearing defects can be various factors such as wear due to continuous contact of rotating elements, excessive load addition, and operating environment. In this paper, a motor driving environment is created which is similar to the domestic manufacturing sites. In addition, based on the established environment, we propose a dataset for bearing fault detection by collecting changes in vibration characteristics that vary depending on normal and defective conditions. The sensor used to collect the vibration characteristics is Microphone G.R.A.S. 40PH-10. We used various machine learning models to build a prototype bearing fault detection system trained on the proposed dataset. As the result, based on the deep neural network model, it shows high accuracy performance of 92.3% in the time domain and 98.3% in the frequency domain.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.4
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• pp.723-730
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• 2023

Due to the recent development of battery technology, various types of means of transportation such as electric kickboards, Segways, and electric bicycles have emerged, which can be defined as Personal Mobility. In this paper, as the incidence of safety accidents increases due to the increase in the number of users of Personal Mobility, safety helmet devices that strengthen safety capabilities and peripheral recognition functions were studied. In order for the helmet to send a safety signal, Arduino was used as a base to set the value of the sensor according to changes in distance and angle using the ultrasonic sensor to minimize errors and ensure smooth recognition. In addition, a gyro sensor was used to turn on the direction indicator according to each slope. Using a CDS sensor, the LED is designed to turn on when it goes below 150 lux at night. Finally, it is possible to check whether a helmet is worn within 5cm, and when driving at an average speed, the direction indicator light is turned on at 10 degrees, and the LED is turned on at less than 150 lux.

• Journal of the Korean Society of Safety
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• v.38 no.1
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• pp.25-33
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• 2023

In this study, we determined the failure rate and fire status of electric motors widely used in domestic and industrial devices and analyzed the associated fire risks by identifying the electrical and temperature characteristics of electric motors under the normal and restrained operation modes in industrial sites and laboratories. A 2.2kW motor used for driving a conveyor during the vulcanization process in a rubber product manufacturing plant was employed as the study object and was exposed to a high- temperature environment as this motor is widely used in industrial sites. The current amplitude was 4.45-4.50 A during normal operation and 38.2-41.5 A during restrained operation due to the pinching of products and semi-finished products (i.e., 8.5 times higher than that during normal operation). The leakage current amplitude was 0.33 mA during both operation modes. The temperature of the workplace in summer was 42.38℃, indicating a poor environment for the installed motor. In the laboratory, the current and temperature of the coil inside a 3.7kW motor were measured under the restrained operation mode as performing measurements of the coil inside the motor in industrial sites is challenging. The current amplitude during normal operation was 3.5 A, whereas that during restrained operation for 30 s was 51.7-58.6 A, which is 14.8-16.7 times higher than that of normal operation. Moreover, the temperature of the motor coil increased from 22.9℃ to 101℃. Based on the experimental data, we derived the temperature increase formula according to the restrained operation time by performing a regression analysis and verified the time at which the temperature exceeded the stipulated limit for the insulation grade. The findings presented in this paper can be utilized to establish fire-prevention measures and perform safety management of motors of the same type or with a similar capacity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3D
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• pp.367-374
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• 2006

This research revealed the operation problems of the current crossing control systems through inspecting and testing the obstacle detection systems and gate control systems for the crossings. To resolve the problems of the crossing control systems, this research developed new algorithms of four-quadrant gate system and obstacle detection systems combing the functions of rasar sensors and magnetic sensors and tested the reliability of the systems. Currently, the obstacle detection systems and gate control systems controls approaching and departing traffic by simply detecting vehicles and obstacles but do not consider traffic movements at the crossings. In addition, they do not make signal cooperation for gate controls. As a result, such inefficient crossing controls result in unsafe gate controls for drivers. Therefore, the newly developed crossing control systems through this study will provide more effective crossing control services with more strengthen information cooperation within control systems. Besides they will help to reduce train crashes at the crossings by gate control systems considering various driving behaviors.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.2
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• pp.217-228
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• 2024

LiDAR(Light Detection And Ranging) sensors, which play a pivotal role among cameras, RADAR(RAdio Detection And Ranging), and ultrasonic sensors for the safe operation of autonomous vehicles, can recognize and detect objects in 360 degrees. However, since LiDAR sensors use lasers to measure distance, they are vulnerable to attackers and face various security threats. In this paper, we examine several security threats against LiDAR sensors: relay, spoofing, and replay attacks, analyze the possibility and impact of physical jamming attacks, and analyze the risk these attacks pose to the reliability of autonomous driving systems. Through experiments, we show that jamming attacks can cause errors in the ranging ability of LiDAR sensors. With vehicle-to-vehicle (V2V) communication, multi-sensor fusion under development and LiDAR anomaly data detection, this work aims to provide a basic direction for countermeasures against these threats enhancing the security of autonomous vehicles, and verify the practical applicability and effectiveness of the proposed countermeasures in future research.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.77-88
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• 2000

In this paper, the 3-mode variable gain high power amplifier for a transmitter of INMARSAT-B operating at L-band(1626.5-1646.5 MHz) was developed. This SSPA can amplify 42 dBm in high power mode, 38 dBm in medium power mode and 36 dBm in low power mode for INMARSAT-B. The allowable errol sets +1 dBm as the upper limit and -2 dBm as the lower limit, respectively. To simplify the fabrication process, the whole system is designed by two parts composed of a driving amplifier and a high power amplifier. The HP's MGA-64135 and Motorola's MRF-6401 were used for driving amplifier, and the ERICSSON's PTE-10114 and PTF-10021 for the high power amplifier. The SSPA was fabricated by the RP circuits, the temperature compensation circuits and 3-mode variable gain control circuits and 20 dB parallel coupled-line directional coupler in aluminum housing. In addition, the gain control method was proposed by digital attenuator for 3-mode amplifier. Then il has been experimentally verified that the gain is controlled for single tone signal as well as two tone signals. In this case, the SSPA detects the output power by 20 dB parallel coupled-line directional coupler and phase non-splitter amplifier. The realized SSPA has 41.6 dB, 37.6 dB and 33.2 dB for small signal gain within 20 MHz bandwidth, and the VSWR of input and output port is less than 1.3:1. The minimum value of the 1 dB compression point gets more than 12 dBm for 3-mode variable gain high power amplifier. A typical two tone intermodulation point has 36.5 dBc maximum which is single carrier backed off 3 dB from 1 dB compression point. The maximum output power of 43 dBm was achieved at the 1636.5 MHz. These results reveal a high power of 20 Watt, which was the design target.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.87-97
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• 2016

This work proposes a time-shared 10b DAC based on a two-step resistor string to minimize the effective area of a DAC channel for driving each AMOLED display column. The proposed DAC shows a lower effective DAC area per unit column driver and a faster conversion speed than the conventional DACs by employing a time-shared DEMUX and a ROM-based two-step decoder of 6b and 4b in the first and second resistor string. In the second-stage 4b floating resistor string, a simple current source rather than a unity-gain buffer decreases the loading effect and chip area of a DAC channel and eliminates offset mismatch between channels caused by buffer amplifiers. The proposed 1-to-24 DEMUX enables a single DAC channel to drive 24 columns sequentially with a single-phase clock and a 5b binary counter. A 0.9pF sampling capacitor and a small-sized source follower in the input stage of each column-driving buffer amplifier decrease the effect due to channel charge injection and improve the output settling accuracy of the buffer amplifier while using the top-plate sampling scheme in the proposed DAC. The proposed DAC in a $0.18{\mu}m$ CMOS shows a signal settling time of 62.5ns during code transitions from '$000_{16}$' to '$3FF_{16}$'. The prototype DAC occupies a unit channel area of $0.058mm^2$ and an effective unit channel area of $0.002mm^2$ while consuming 6.08mW with analog and digital power supplies of 3.3V and 1.8V, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.1
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• pp.53-60
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• 2004

This work describes a l0b 150 MSample/s CMOS pipelined A/D converter (ADC) based on advanced bootsuapping techniques for higher input bandwidth than a sampling rate. The proposed ADC adopts a typical multi-step pipelined architecture, employs the merged-capacitor switching technique which improves sampling rate and resolution reducing by $50\%$ the number of unit capacitors used in the multiplying digital-to-analog converter. On-chip current and voltage references for high-speed driving capability of R & C loads and on-chip decimator circuits for high-speed testability are implemented with on-chip decoupling capacitors. The proposed AU is fabricated in a 0.18 um 1P6M CMOS technology. The measured differential and integral nonlinearities are within $-0.56{\~}+0.69$ LSB and $-1.50{\~}+0.68$ LSB, respectively. The prototype ADC shows the signal-to-noise-and-distortion ratio (SNDR) of 52 dB at 150 MSample/s. The active chip area is 2.2 mm2 (= 1.4 mm ${\times}$ 1.6 mm) and the chip consumes 123 mW at 150 MSample/s.