Development of Probability-Based Assessment Index for Docking Process Assessment
천승재 Seung-jae Chon , 김준영 Joon-young Kim , 최중락 Joong-lak Choi , 정성훈 Seong-hoon Jeong , 김종화 Jong-hwa Kim
25(3) 177-184, 2021
천승재 Seung-jae Chon , 김준영 Joon-young Kim , 최중락 Joong-lak Choi , 정성훈 Seong-hoon Jeong , 김종화 Jong-hwa Kim
DOI: JANT Vol.25(No.3) 177-184, 2021
This paper proposes an assessment method using probability-based index for safe and successful underwater docking of autonomous underwater vehicles(AUVs) to the docking stations(DSs). The proposed method assesses the probability of docking according to the degree to which the state of the AUV is consistent with the state criteria for docking. The assessment is performed within a specific area considering the kinematic constraints and docking plans of the AUV. The assessment process is defining probability density function, calculating probabilities for reaching the docking station according to the difference to position and heading criteria, and computing the probability-based index in real-time. We verify the validity of the proposed method through analyzing the data acquired on operation test.
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A Study on improvement of Korean aircraft system modification certification procedure
유병선 Beong-seon Yoo , 임인규 In-kyu Lim
25(3) 185-193, 2021
유병선 Beong-seon Yoo , 임인규 In-kyu Lim
DOI: JANT Vol.25(No.3) 185-193, 2021
The system needs to be modified to improve the performance of the aircraft in operation or to satisfy the requirements of related laws. Appropriate standards are required for the technical skills for remodeling the aircraft system, design verification for airworthiness of the aircraft, and supplemental type certification (STC) certification procedures for type certification. This study analyzes the current status and demand of domestic aircraft remodeling, examines the current supplementary type certification procedure, and diagnoses the problem. In addition, as a result of researching measures to improve remodeling technology and certification capabilities to extend the life of the aircraft, improvements in the education system were derived to improve the domestic additional type certification process, such as approval of remodeling agencies and appointment of qualifications for each professional technician.
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A Residual Ionospheric Error Model for Single Frequency GNSS Users in the Korean Region
윤문석 Moonseok Yoon , 안종선 Jongsun Ahn , 주정민 Jung-min Joo
25(3) 194-202, 2021
윤문석 Moonseok Yoon , 안종선 Jongsun Ahn , 주정민 Jung-min Joo
DOI: JANT Vol.25(No.3) 194-202, 2021
Ionosphere, one of the largest error sources, can pose potentially harmful threat to single-frequency GNSS (global navigation satellite system) user even after applying ionospheric corrections to their GNSS measurements. To quantitatively assess ionospheric impacts on the satellite navigation-based applications using simulation, the standard deviation of residual ionospheric errors is needed. Thus, in this paper, we determine conservative statistical quantity that covers typical residual ionospheric errors for nominal days. Extensive data-processing computes TEC (total electron content) estimates from GNSS measurements collected from the Korean reference station networks. We use Klobuchar model as a correction to calculate residual ionospheric errors from TEC (total electron content) estimate. Finally, an exponential delay model for residual ionospheric errors is presented as a function of local time and satellite elevation angle.
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Analyses of Hover Lift Efficiency, Disc Loading and Required Battery Specific Energy for Various eVTOL Types
김동희 Dong-hee Kim , 장한용 Han-yong Jang , 황호연 Ho-yon Hwang
25(3) 203-210, 2021
김동희 Dong-hee Kim , 장한용 Han-yong Jang , 황호연 Ho-yon Hwang
DOI: JANT Vol.25(No.3) 203-210, 2021
In many metropolitan cities around the world, ground and underground transportation networks are saturated due to urbanization. In addition, regulations on carbon emissions to prevent global warming are becoming stricter, and eVTOL, which will be operating in complex cities, is gaining popularity as the next generation of eco-friendly transportation. In this study, the hover lift efficiency and disc loading of eVTOLs for each type were calculated by classifying eVTOLs into following types: multicopter, lift+cruise, and vectored thrust. In addition, using the aerodynamic analysis programs OpenVSP, Fluent and Javaprop, the specific battery energy required for the smooth operation of eVTOL, which will be realized in the near future, was calculated and analyzed base on reports published by Uber and airworthiness authorities of each country.
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Flexible Formation Algorithm for Multiple UAV Using the Packing
김효중 Hyo-jung Kim , 김정훈 Jeong-hun Kim , 김문정 Moon-jung Kim , 유창경 Chang-kyung Ryoo
25(3) 211-216, 2021
김효중 Hyo-jung Kim , 김정훈 Jeong-hun Kim , 김문정 Moon-jung Kim , 유창경 Chang-kyung Ryoo
DOI: JANT Vol.25(No.3) 211-216, 2021
Multiple UAV System has been used for various purposes such as reconnaissance, networking and aerial photography. In such systems, it is essential to form and maintain the formation of multiple UAVs. This paper proposes the algorithm that produces an autonomous distributed control for each vehicle for a flexible formation. This command is a repulsive force in the form of the second-order system by the nearest UAV or mission area. The algorithm uses the relative position/speed through sensing and communication for calculating the command without external intervention. The command allows each UAV to follow the reference distance and fill the mission area as densely as possible without overlapping. We determine the reference distance via optimization technique solving the packing problem. The mission area comprises the desired formation outline and can be set flexibly depending on the mission. Numerical simulation is carried out to verify the performance of the proposed algorithm under a complex and flexible environment. The formation is formed in 26.94 seconds and has a packing density of 71.91%.
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The Optical Tracking Method of Flight Target using Kalman Filter with DTW
장석원 Sukwon Jang
25(3) 217-222, 2021
장석원 Sukwon Jang
DOI: JANT Vol.25(No.3) 217-222, 2021
EOTS(Electro-Optical Tracking System) is utilized in acquiring visual information to assess a guided missile’s performance. As the missile travels so fast, it is almost impossible for operator to re-capture the lost target. The RADAR or telemetry data are used to re-capture the lost target however facilities to receive real time data is required, which constrains selection of tracking site. Unlike aforementioned data, pre-calculated nominal trajectory can be used without communication facility. This paper proposes a method to predict lost target’s state by employing nominal trajectory. Firstly, observed trajectory and nominal trajectory are compared using DTW and current target’s state is predicted. The predicted state is used as observation in Kalman filter’s correction phase to predict target’s next state. The plausibility of the proposed method is verified by applying on actual missile trajectory.
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Slot Antenna Embedded in a PCB for Zigbee Communication
우희성 Hee-sung Woo , 신동기 Dong-gi Shin , 이영순 Young-soon Lee
25(3) 223-228, 2021
우희성 Hee-sung Woo , 신동기 Dong-gi Shin , 이영순 Young-soon Lee
DOI: JANT Vol.25(No.3) 223-228, 2021
In this paper, we proposed a slot-type antenna with microstrip feed embedded in a PCB for Zigbee communication (2.4 ~ 2.484 GHz). The proposed antenna is designed on a FR-4 substrate with dielectric constant 4.3, thickness of 1.6 ㎟, and size of 50×65㎟ . Through simulations, trends of design parameters are analyzed and optimized, and the proposed antenna composed with three slots satisfy the frequency band. The measured impedance bandwidths (|S11|≤ -10 dB) of fabricated antenna are 900 MHz (2 ~ 2.9 GHz) in Zigbee frequency band. In addition, the radiation pattern showed omnidirectional characteristics for E and H-planes, and the gain of antenna in Zigbee frequency band was 1.782 dBi.
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Power Dividers for High Splitting Ratios using Transmission Line Connected with Open and Short Stubs
김영 Young Kim
25(3) 229-235, 2021
김영 Young Kim
DOI: JANT Vol.25(No.3) 229-235, 2021
This paper proposes a method of implementing an unequal power divider for high splitting ratios by using transmission lines connected with open and short stubs. The proposed method is an equivalent circuit analysis of a transmission line with an additional port so that it can be converted to an arbitrary impedance in the center of a 2-port transmission line and a 3-port transmission line with an open or short stub connected in parallel to each port. To prove the validity of this method, a Wilkinson power divider with k2 = 20 dB splitting ratio and a Gysel power divider with k2 = 17 dB splitting ratio were designed at a center frequency of 1 GHz using a 3-port transmission line equivalent circuit. The experimental results of the electrical characteristics are in good agreement with the simulation.
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Effect of Maritime Traffic Control Radar Interference by a small number of Wind Turbines
오성원 Seongwon Oh , 박태용 Tae-yong Park
25(3) 236-241, 2021
오성원 Seongwon Oh , 박태용 Tae-yong Park
DOI: JANT Vol.25(No.3) 236-241, 2021
This paper presents a methodology to analyze the interference of maritime traffic control radar by wind turbines installed in the sea, and the interference result of the maritime traffic control radars by a small number of wind turbines installed in sea near Gunsan port (Gunsan vessel traffic services). A ray based electromagnetic analysis software is used to analyze the interference. The geographic information system map containing altitude data, drawing of wind turbines, and sea with waves are imported to the software to analyze the effect of the terrain and the wind turbines. According to the analysis, a small number of wind turbines, not large scale wind farms, has no severe impact on the operation of the radar.
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Analysis of Maritime-based Space Capabilities of Major Countries and Future Direction for South Korea
조태환 Taehwan Cho , 이성섭 Soungsub Lee
25(3) 242-247, 2021
조태환 Taehwan Cho , 이성섭 Soungsub Lee
DOI: JANT Vol.25(No.3) 242-247, 2021
Major countries in space field such as the United States, China and Russia have not only general ground-based space capabilities, but also maritime-based space capabilities. Maritime-based space systems include a maritime-based space surveillance system, a maritime-based space launch vehicle, and a maritime-based space information transmission system, and these maritime-based systems complement the ground-based space systems. Therefore, in this paper, we analyze the maritime-based space capabilities of major countries, and propose the future direction for south Korea's maritime-based space capabilities. The maritime-based space system is essential due to the geographical characteristics of south Korea, which has three sides of the ocean, and it is considered an one of important strategic element to become the seven major country in the space field.
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Trend Analyses of B777 FLCH Usage Beyond FAF Events
정승섭 Chung Seung Sup , 김현덕 Kim Hyeon Deok
25(3) 248-255, 2021
정승섭 Chung Seung Sup , 김현덕 Kim Hyeon Deok
DOI: JANT Vol.25(No.3) 248-255, 2021
The main causes of the July 2013 OZ 214 accident were poorly performed approach and the failure to recognize the autothrottle in the HOLD position which the automated speed control was not provided. The pilots late decision for go-around was also a critical factor leading to the accident. The B777 POM restricts the use of FLCH mode beyond the FAF. This research utilized the QAR data of an airline’s B777 fleet in the period of two years where 44 cases were found. In many cases, the FLCH mode was used for rapid descent from an higher than normal situation. In addition, in the base turn, continuous use of FLCH mode even when the path was below the glide path were observed. Airports with elevation above 500 ft MSL had a higher rate of occurrence. In this research, the proper descent planning and vertical path monitoring, and the adherence to the limitation set in the manuals and the stabilized approach criteria were re-emphasized as mitigation to reduce event occurences.
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Applicable Focal Points of HFACS to Investigate Domestic Civil Unmanned Aerial Vehicle Accidents
이건희 Keon-hee Lee , 김현덕 Hyeon-deok Kim
25(3) 256-266, 2021
이건희 Keon-hee Lee , 김현덕 Hyeon-deok Kim
DOI: JANT Vol.25(No.3) 256-266, 2021
Domestic and foreign studies point to human factors as the main cause of unmanned aerial vehicle accidents, and HFACS is introduced as a technique to effectively analyze these human factors. Until now, domestic and foreign cases of analyzing the human factors of unmanned aerial vehicle accidents using HFACS were mainly targeted by military unmanned aerial vehicles, which can be used as an objective cause identification and similar accident prevention tool. In particular, identifying the focus of HFACS application considering the performance and operation conditions of domestic civilian unmanned aerial vehicles is expected to greatly help identify the cause and prevent recurrence in the event of an accident. Based on HFACS version 7.0, this study analyzed the accident investigation report data conducted by Korea Aviation and Railway Accident Investigation Board to identify the focus of HFACS application that can be used for domestic civilian unmanned aircraft accident investigations.
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