비정형 디팔레타이징 작업을 위한 Multi-RRT 기반의 다관절 로봇 경로 계획

김동형(Donghyung Kim),송병열(Byoung Youl Song),김중배(Joong Bae Kim) 제어로봇시스템학회 2020 제어·로봇·시스템학회 논문지 Vol.26 No.4

This paper presents an algorithm for robot path planning for unstructured depalletizing tasks. Parcel depalletization is a multi-start single-goal path planning problem that involves placing multiple parcels in the same location. To solve this problem, we propose a new path planning algorithm called the multi-start single-goal RRT (Rapidly-exploring Random Tree), which is an extended version of the bidirectional RRT. The multi-start single-goal RRT is based on multi-RRT and uses multiple trees to find a path that connects multiple parcels to a single placing position. We verified the performance of the proposed algorithm by solving the three-dimensional path planning problem with a simulation before applying it to articulated robot arms.

로봇형 차량의 경로 추종 및 장애물 회피를 위한 운동 계획에 관한 연구

김동형(Donghyung Kim),김창준(Changjun Kim),김상호(Sangho Kim),최주영(Jooyoung Choi),한창수(Changsoo Han) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11

This paper presents the motion planning of robotic vehicles for the path tracking and the obstacle avoidance. To follow the given path, the vehicle moves through the turning radius obtained through the pure pursuit method, which is a geometric path tracking method. In this paper, we assume that the vehicle is equipped with a range scanner, allowing it to avoid obstacles within its sensing range. The turning radius for avoiding the obstacle, which is inversely proportional to the virtual force, is then calculated. Therefore, these two kinds of the turning radius are used to generate the steering angle for the front wheel of the vehicle. And the vehicle reduces the velocity when it meets the obstlace or the large steering angle using the potentials of obstacle points and the steering angle. Thus the motion planning of the vehicle is done by planning the steering angle for the front wheels and the velocity. Finally, the performance of the proposed method is tested through simulation.

축소 모델 차량을 통한 자율 주행 차량의 경로 추종 및 장애물 회피 기법에 관한 연구

김동형(Donghyung Kim),김창준(Changjun Kim),김영렬(Youngryul Kim),한창수(Changsoo Han) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5

This paper presents a method that integrates the geometric path tracking and the obstacle avoidance for autonomous ground vehicle (AGV). AGV follows the path by moving through the turning radius given from the pure pursuit method which is the one of the geometric path tracking methods. As the AGV equipped with 2D laser scanner, the obstacle within the sensing range of 2D laser scanner, the virtual force is obtained. Therefore, the turning radius for avoiding the obstacle is calculated by inversely proportional to the virtual force. By integrating the turning radius for avoiding the obstacle and the turning radius for following the path, AGV follows the path and avoids the obstacle simultaneously. The effectiveness of the proposed method is verified through the real experiments using a scale-down vehicle.

방향성 정수 변환을 이용한 비디오 압축 효율 개선 알고리즘

김동형(Donghyung Kim),정세윤(Seyoon Jeong),정원식(Won-Sik Cheong),최진수(Jin-Soo Choi),문경애(Kyung-Ae Moon),홍진우(Jinwoo Hong) 대한전자공학회 2007 대한전자공학회 학술대회 Vol.2007 No.11

H.264 standard adapts new coding tools such as 1/4-pel accuracy motion estimation, 4×4 integer transform, and intra prediction in spatial domain. In this paper, the directional reordering method for integer transform is proposed. Simulation results show that the proposed method is potentially able to improve coding efficiency.

자율주행 차량의 경유점 추종을 위한 통합된 궤적 계획기 및 제어기에 관한 연구

김동형(Donghyung Kim),김창준(Changjun Kim),김상호(Sangho Kim),최주영(Jooyoung Choi),최민석,한창수(Changsoo Han) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5

This paper presents the integrated trajectory planner and controller for the waypoint tracking of autonomous vehicles. In the case of that there are no driving lanes, the trajectory should be planned for the vehicle. However, because of the nonholonomic constraint which renders the motion orthogonal to the vehicle’s forward direction is impossible, the trajectory planning and the control problems are becoming complicated. To solve these problems, the trajectory planning and control are integrated using the flatness property of the kinematic model of the vehicle. And with the given waypoints, the waypoint tracking algorithm is proposed to plan the trajectory for the next waypoint. Therefore the vehicle follows the waypoints in order. Finally, the performance of the proposed method is tested through simulation.

컬러 이미지 화질 개선을 위한 Retinex 기반의 로그변환 기법

김동형(Donghyung Kim) 한국산학기술학회 2018 한국산학기술학회논문지 Vol.19 No.5

광원 자체의 밝기가 낮거나 그림자 등의 이유로 어두운 영역을 포함하는 이미지는 Retinex 기반의 영상화질 개선기법을 통해 주관적 화질을 높일 수 있다. Retinex 이론은 인간의 시각 시스템이 장면을 인식할 때 특정 위치에서의 장면의 밝기를 인식하는 것이 아니라 주변과의 상대적인 밝기를 인식하는 특징을 적용한 방법으로 크게 SSR, MSR, MSRCR의 방법으로 나눌 수 있다. 제안하는 방법은 컬러복원단계를 포함하고 있는 MSRCR에 기반한 방법으로 크게 3단계로 구성되어 있다. 첫 번째 단계에서는 기존의 MSRCR 방법을 적용하고 두 번째 단계에서 MSRCR 출력의 동적 영역을 이미지의 히스토그램분포에 따라 조정한다. 마지막 단계에서는 인간의 시각특성을 고려한 로그변환함수를 이용하여 Retinex 출력 값을 디스플레이 동적영역으로 변환한다. 실험결과 제안하는 알고리즘은 전체적으로 어두운 이미지뿐만 아니라 밝은 영역과 어두운 영역을 모두 포함하는 이미지에서도 주관적 화질을 효과적으로 증가시키는 것을 볼 수 있다. 특히 낮은 밝기를 갖는 이미지의 경우 제안한 알고리즘은 기존의 방법들 보다 높은 성능향상을 보였다. Images with lower illumination from the light source or with dark regions due to shadows, etc., can improve subjective image quality by using retinex-based image enhancement schemes. The retinex theory is a method that recognizes the relative lightness of a scene, rather than recognizing the brightness of the scene. The way the human visual system recognizes a scene in a specific position can be in one of several methods: single-scale retinex, multi-scale retinex, and multi-scale retinex with color restoration (MSRCR). The proposed method is based on the MSRCR method, which includes a color restoration step, which consists of three phases. In the first phase, the existing MSRCR method is applied. In the second phase, the dynamic range of the MSRCR output is adjusted according to its histogram. In the last phase, the proposed method transforms the retinex output value into the display dynamic range using a logarithm transformation function considering human visual system characteristics. Experimental results show that the proposed algorithm effectively increases the subjective image quality, not only in dark images but also in images including both bright and dark areas. Especially in a low lightness image, the proposed algorithm showed higher performance improvement than the conventional approaches.

다관절 로봇을 사용한 롤테이너 모서리에서 기울어진 소포 피킹을 위한 동작계획 방법

김동형(Donghyung Kim),임을균(Eul Gyoon Lim),김중배(Joong Bae Kim) 대한전자공학회 2021 대한전자공학회 학술대회 Vol.2021 No.6

국부가중선형변환 함수를 이용한 이미지 대비비 향상 기법

김동형(Donghyung Kim) 한국정보기술학회 2014 한국정보기술학회논문지 Vol.12 No.4

Typical methods that enhance image contrast are histogram stretching and histogram equalization. The histogram stretching method is the linear transformation function mapping dynamic range of input image to total available one. The histogram equalization method uses the transformation function that is a cumulative density function of input image. In this paper, a local linear transformation(LLT) and a local weighted linear transformation methods based on these two methods were proposed. LLT is linear transformation function that stretches or compresses dynamic range adaptively in each local region. LWLT is the LLT adding weight that reflects humans characteristics of sight, and each weight is calculated from Weber-Fechners law. The experimental results show that the proposed algorithm effectively enhances the contrast in terms of subjective quality. Also, the proposed method has higher entropy, EBCM and GSD values than other conventional approaches.

이미지 화질개선을 위한 Weber-Fechner 법칙을 적용한 가중 히스토그램 균등화 기법

김동형(Kim, Donghyung) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.7

저화질 이미지의 화질 개선에는 전통적으로 히스토그램균등화 기법이 사용되어 왔다. 히스토그램균등화 기법은 입력 이미지의 누적밀도함수를 변환함수로 사용하는 기법으로 이는 이론상 최대의 엔트로피를 가지지만 주관적 화질 측면에서는 백화현상이 나타나는 문제점이 있다. 본 논문에서는 히스토그램균등화 기법 기반의 가중 히스토그램 균등화 기법을 제안한 다. 이는 인간의 시각특성을 반영한 Weber-Fechner 법칙을 사용하며 입력영상에 독립적인 변환함수를 제공하는 여러 이미 지 화질 개선 기법들이 가지는 문제점을 해결하기 위해서 동적영역 재조정 과정을 포함한다. 최종적으로 재조정된 동적영역 범위 내에서 Weber-Fechner 법칙을 적용한 변환함수와 히스토그램균등화 기법을 통해 얻어진 변환함수간의 가중 평균을 통하여 변환함수를 생성한다. 실험결과 제안하는 알고리즘은 주관적 화질 측면에서 대비비를 효과적으로 향상시키는 것을 보여주며, 엔트로피 또한 비교 에 사용된 여러 이전의 방법들과 비교하여 유사하거나 높은 값을 가지는 것을 볼 수 있었다. A histogram equalization method have been used traditionally for the image enhancement of low quality images. This uses the transformation function, which is a cumulative density function of an input image, and it has mathematically maximum entropy. This method, however, may yield whitening artifacts. This paper proposes the weighted histogram equalization method based on histogram equalization. It has Weber-Fechner's law for a human's vision characteristics, and a dynamic range modification to solve the problem of some methods, which yield a transformation function, regardless of the input image. Finally, the proposed transformation function was calculated using the weighted average of Weber-Fechner and the histogram equalization transformation functions in a modified dynamic range. The simulation results showed that the proposed algorithm effectively enhances the contrast in terms of the subjective quality. In addition, the proposed method has similar or higher entropy than the other conventional approaches.

H.264/AVC 인트라 부호화에서의 비손실 고속 예측모드 선택방법

김동형(Donghyung Kim),서재성(Jaesung Seo) 한국정보기술학회 2010 한국정보기술학회논문지 Vol.8 No.2

For the improvement of coding efficiency, the H.264/AVC standard uses new coding tools such as multiple references, intra prediction, loop filter, motion estimation using variable block sizes etc. Using these coding tools, H.264/AVC has achieved significant improvements from rate-distortion point of view compared to existing standards. However, the encoder complexity was greatly increased due to these coding tools. In this paper, we focus on the complexity reduction method of prediction mode selection included in encoding process of intra frames. Simulation results show that the proposed method saves about 17.5% for QCIF sequences and 18.5% for CIF sequences of total encoding time without any PSNR decrease or any bitrate increase, and it works better at low-bitrate.