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A Novel Feature Coordinate Initialization Algorithm Utilizing Image-Based Hybrid Correspondences
Lee Yu Dam,Yoo Won Jae,Kim Lawoo,Lee Hyung Keun 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.2
This paper proposes a novel feature coordinate initialization algorithm based on combined 2D and 3D feature points for visual Simultaneous Localization and Mapping (vSLAM) and Structure from Motion (SfM) algorithms. In conventional algorithms, the feature initialization assumes the known camera pose (position and orientation). The initialized feature points are utilized in turn for estimating future camera pose. For the reason, the accuracy of the estimated camera pose is highly dependent on that of the initialized feature points and vice versa. The proposed algorithm deals with the problem based on a simple and effi cient error model exploiting the 2D-2D and 2D-3D matched feature points (referred to as hybrid correspondence) between two views acquired by a single camera. The advantage of the proposed algorithm is threefold. First, it performs the camera pose estimation and triangulation simultaneously. Second, it reduces sensitivity to measurement errors in 3D reference points so that more reliable camera pose can be provided with fewer feature points. Third, it improves the depth accuracy as the baseline between two cameras becomes longer. For the performance evaluation, the proposed algorithm is compared with conventional algorithms by both synthetic and real data.
Yu Dam Lee,Taek Geun Lee,Hyung Keun Lee 사단법인 항법시스템학회 2023 Journal of Positioning, Navigation, and Timing Vol.12 No.2
Autonomous driving systems are likely to be operated in various complex environments. However, the well-known integrated Global Navigation Satellite System (GNSS)/Inertial Navigation System (INS), which is currently the major source for absolute position information, still has difficulties in accurate positioning in harsh signal environments such as urban canyons. To overcome these difficulties, integrated Visual/Inertial/GNSS (VIG) navigation systems have been extensively studied in various areas. Recently, a Compressed-State Constraint Kalman Filter (CSCKF)-based VIG navigation system (CSCKF-VIG) using a monocular camera, an Inertial Measurement Unit (IMU), and GNSS receivers has been studied with the aim of providing robust and accurate position information in urban areas. For this new filter-based navigation system, on the basis of timepropagation measurement fusion theory, unnecessary camera states are not required in the system state. This paper presents a performance evaluation of the CSCKF-VIG system compared to other conventional navigation systems. First, the CSCKF-VIG is introduced in detail compared to the well-known Multi-State Constraint Kalman Filter (MSCKF). The CSCKF-VIG system is then evaluated by a field experiment in different GNSS availability situations. The results show that accuracy is improved in the GNSS-degraded environment compared to that of the conventional systems.
( Yu Jun Lee ),( Su Bin Lee ),( Jae Young Jung ),( Dam Hee Lee ),( Ur Ryong Cho ) 한국고무학회 2016 엘라스토머 및 콤포지트 Vol.51 No.2
The composites of EVA/EPDM including aluminum trioxide (ATH) as a fire retardant were manufactured for the purpose of improving low temperature property and flame resistance in the rubbery materials. The ratio of EVA to EPDM didn``t affect the flame resistance of the rubber composites. The addition of ATH resulted in increase of the flame resistance. In the evaluation of the cold resistance, the increasing EPDM content showed enhancement of cold resistance in the composites due to increasing low Tg EPDM. It was found out that tensile strengths of the composites showed a maximum value at 100 phr of ATH by reinforcing effect, but a minimum value at 200 phr of ATH owing to slippage between the flame retardant by the external stress. In the measurement of solvent resistance in tetrahydrofuran, the increasing ATH content yielded enhancement of solvent resistance by reducing swelling of the composite, and increasing EPDM content also resulted from increase of the solvent resistance by reduction of polarizability as well as increase of crosslink in the com-posites.
RTK GPS/INS/스테레오 카메라를 활용한 3 차원 지도 기반 복합 항법의 공간 정보 생성 시스템
이유담(Yu Dam Lee),최광호(Kwang Ho Choi),임준후(Joon Hoo Lim),유원재(Won Jae Yoo),김라우(La Woo Kim),이형근(Hyung Keun Lee) 제어로봇시스템학회 2018 제어·로봇·시스템학회 논문지 Vol.24 No.8
This paper proposes a method to obtain absolute coordinates of considerably many point clouds on designated objects by integrating Global Positioning System (GPS), an Inertial Navigation System (INS), and a stereo camera. Compared with existing methods, the proposed method enables acquiring absolute coordinates instead of relative coordinates of point clouds with respect to a global reference frame. The GPS receiver and INS sensor are used for acquiring absolute coordinates and attitude parameters of the camera. The stereo camera is used to capture image pairs to compute relative coordinates of point clouds by feature-based image matching method. In addition, a Real-Time Kinematic (RTK) software is utilized to estimate accurate coordinates of the camera, and a time synchronization method between different systems to which sensors are connected is proposed. Based on the estimated absolute coordinates and attitude parameters of the camera, the relative coordinates of point clouds with respect to the camera are converted to the absolute coordinates.
A Study on Effective Satellite Selection Method for Multi-Constellation GNSS
Taek Geun Lee,Yu Dam Lee,Hyung Keun Lee 사단법인 항법시스템학회 2023 Journal of Positioning, Navigation, and Timing Vol.12 No.1
In this paper, we propose an efficient satellite selection method for multi-constellation GNSS. The number of visible satellites has increased dramatically recently due to multi-constellation GNSS. By the increased availability, the overall GNSS performance can be improved. Whereas, due to the increase of the number of visible satellites, the computational burden in implementing advanced processing such as integer ambiguity resolution and fault detection can be increased considerably. As widely known, the optimal satellite selection method requires very large computational burden and its realtime implementation is practically impossible. To reduce computational burden, several sub-optimal but efficient satellite selection methods have been proposed recently. However, these methods are prone to the local optimum problem and do not fully utilize the information redundancy between different constellation systems. To solve this problem, the proposed method utilizes the inter-system biases and geometric assignments. As a result, the proposed method can be implemented in real-time, avoids the local optimum problem, and does not exclude any single-satellite constellation. The performance of the proposed method is compared with the optimal method and two popular sub-optimal methods by a simulation and an experiment.
이종담,유태현,이석규,허방,허만하 고신대학교 의학부 1987 高神大學校 醫學部 論文集 Vol.3 No.1
Chordoma is a rare, slow-growing, but relentless tumor which arises from primitive notochodal remnants. This tumor is a locally aggressive, rarely, if ever, metastasizing tumor. Although it occurs primarily in the sphenooccipital and sacrococcygeal regions, it may occasionally present with a nasopharyngeal mass in the intervening vertebrae of the cervical spine such as this case. The treatment of choice is a surgical excision with radiation therapy. The authors experienced a rare case of pathologically confirmed cervical chordoma in a 65-year-old Korean female who had suffered from dysphagia for several months. We report this case with literature review with emphasis on the histogenesis of chordoma and clinopathologic features.