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Time Frequency Domain Reflectometry 기법을 이용한 Coaxial Cable에서의 결함 감지 및 추정
송은석,신용준,최덕선,육종관,박진배,Powers, Edward J. 한국항행학회 2003 韓國航行學會論文誌 Vol.7 No.1
본 논문에서는 도선사에서 발생하는 결함 위치와 이상 유무를 감지하는 새로운 고분해능 반사측정법인 시간-주파수 영역반사측정법 (TFDR, Time-Frequency Domain Reflectometry)을 제안하였다. 고전적인 반사측정법들은 단지 시간 또는 주파수의 한 영역에서 분석되어져 왔으나, 본 논문에서 제시한 TFDR은 도선의 결함 위치와 이상 유무를 발견하기 위해 과도신호의 시간과 주파수 영역의 정보를 동시에 이용할 수 있는 시간-주파수 분석기법으로 특성화하였다. TFDR의 기준신호 설계는 측정 케이블의 물리적 성질들을 고려하여 주파수 밴드를 결정하며, 도선의 결함감지와 추정은 시간-주파수 상호상관관계 함수에 의해 이루어진다. TFDR 시스템을 이용하여 여러 결함 상태를 가진 실제 coaxial cable (RG-142, RG-400)에 대해 실험하였고 정확성을 입증하기 위해 TDR (Time Domain Reflectometry) 장비와 성능은 비교하였다. 본 논문에서는 TFDR이 TDR보다 작은 오차로 결함을 찾아냄을 나타내고 있으며, 측정된 정확도는 TFDR의 오차율이 0.5%이하로 TDR (54750A/54754A) 장비보다 성능이 월등히 우수하다는 것을 알 수 있다. In this paper, a new high resolution reflectometry scheme, time-frequency domain reflectometry (TFDR), is proposed to detect and locate fault in wiring. Traditional reflectometry methods have been achieved in either the time domain or frequency domain only. However, time-frequency domain reflectometry utilizes time and frequency information of a transient signal to detect and locate the fault. The time-frequency domain reflectometry approach described in this paper is characterized by time-frequency reference signal design and post-processing of the reference and reflected signals to detect and locate the fault. Design of the reference signal in time-frequency domain reflectometry is based on the determination of the frequency bandwidth of the physical properties of cable under test. The detection and estimation of the fault on the time-frequency domain reflectometry relies on the time-frequency domain reflectometry is compared with commercial time domain reflectometry (TDR) instrument. In these experiments provided in this paper, TFDR locates the fault with smaller error than TDR. Knowledge of time and frequency localized information for the reference and reflected signal gained via time-frequency analysis, allows one to detect the fault and estimate the location accurately.
Depth sensor and DVL-aided vertical channel damping loop design for underwater vehicles
Tok Son Choe,Won Sang Ra,Jin Bae Park IET 2015 Electronics letters Vol.51 No.22
<P>A novel vertical channel damping loop design method that uses not only a depth sensor but also a Doppler velocity log (DVL) for underwater vehicles is proposed. In the proposed method, the loop gains are calculated by adopting the steady-state Kalman filter gain with consideration of characteristics of the depth sensor and the DVL. The simulation results demonstrate that the proposed method achieves better performance than the conventional method.</P>
Vertical Channel Damping Loop Design using Vertical Position and Velocity Information
Tok Son Choe,Won Sang Ra,Jin Bae Park,Kwanghoon Kim,Myonghwan Ahn 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10
In this paper, a vertical channel damping loop design using vertical position and velocity information is newly proposed. The inertial navigation system (INS) for the position, orientation, and velocity is mostly used for various platforms. The main disadvantage of the INS is that the navigation information degrade with time. Especially, the vertical channel error diverges exponentially if external sensors do not compensate it. The proposed method uses vertical position and velocity information acquired by additional sensors. The Kalman filter is constructed to calculate vertical channel damping loop gains. The proposed method is simulated by using INS and additional sensors error statistics. Results demonstrate the usefulness and practicality of the proposed method.
崔德善(Tok Son Choe) 대한전기학회 2007 전기학회논문지 Vol.56 No.7
In this paper, a real-time collision avoidance algorithm is proposed for eXperimental Autonomous Vehicle(XAV). To ensure real-time implementation, a virtual potential field is calculated in one dimensional space. The attractive force is generated by the steering command either transmitted in the remote control station or calculated in the Autonomous Navigation System(ANS) of the XAV. The repulsive force is generated by obstacle information obtained from Laser Range Finder(LRF) mounted on the XAV. Using these attractive and repulsive forces, modified steering, velocity and emergency stop commands are created to avoid obstacles and follow a planned path. The suggested algorithm is inserted as one component in the XAV system. Through various real experiments and techinical demonstration using the XAV, the usefulness and practicality of the proposed algorithm are verified.
야지 주행 무인지상차량을 위한 3D 라이다 기반 지면 및 장애물 탐지에 대한 연구
최덕선(Choe, Tok Son),심성대(Sim, Sungdae),민지홍(Min, Jihong) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
In this paper, we propose a 3D LIDAR based-obstacle and ground detection algorithm for unmanned ground vehicles driving on rough terrain. We use the Velodyne HDL-32E which is a 32 laser 3D (360°×41.33°) scanning LIDAR. By using the vertical scanning mechanism of this 3D LIDAR, we calculate the gradient of the terrain. For real-time applications, we develop the obstacle and ground detection algorithm by using this gradient. The algorithm is verified by various real experiments.
최덕선(Tok Son Choe),주상현(Sang Hyun Joo),박용운(Yong Woon Park),박진배(Jin Bae Park) 대한전기학회 2016 전기학회논문지 Vol.65 No.2
We propose an obstacle detection algorithm for unmanned ground vehicle on uneven terrain. The key ideas of the proposed algorithm are the use of two-layer laser range data to calculate the gradient of a target, which is characterized as either ground or obstacles. The proposed obstacle detection algorithm includes 4-steps: 1) Obtain the distance data for each angle from multiple lidars or a multi-layer scan lidar. 2) Calcualate the gradient for each angle of the uneven terrain. 3) Determine ground or obstacle for each angle on the basis of reference gradient. 4) Generate a new distance data for each angle for a virtual laser scanner. The proposed algorithm is verified by various experiments.
지도 정보를 활용한 저사양 GPS의 위치 정확도 향상 기법
최덕선(Tok Son Choe),강정민(Jung Min Kang),김한솔(Han Sol Kim),박진배(Jin Bae Park) 대한전기학회 2016 전기학회논문지 Vol.65 No.4
In this paper, we propose a novel position accuracy enhancement method of a low-end GPS using digital map information. The latest digital map has various kinds of information on geographical features. The proposed method uses position information of lane marks among the geographical features. We define the position information of lane marks as the reference points. The position information of a low-end GPS acquired for a period of time is defined as the source points. In the proposed method, rotation and translation matrices between the reference and the source points are calculated by using an Iterative Closest Point(ICP) algorithm. The source points are transformed by the obtained rotation and translation matrices. Finally, the transformed source points are projected on the reference points. Through these processes, the position accuracy of a low-end GPS is ultimately enhanced. To verify the proposed method, the various real experimental results are presented.
최덕선(Tok Son Choe),민지홍(Ji-Hong Min),안성용(Seong Yong Ahn) 대한전자공학회 2018 대한전자공학회 학술대회 Vol.2018 No.6
This paper introduces improvement of object recognition using tracking information. Intermittent erroneous recognition and occlusion are important problems to overcome in object recognition. Using the trajectory information of each object generated by tracking, the problems are solved in this paper. The possibility of the proposed method is verified by a simple experiment.