• 대한전기학회논문지:전력기술부문A
• /
• 제48권3호
• /
• pp.313-320
• /
• 1999

The Lane-Curvature Method(LCM) presented in this paper is a new local obstacle avoidance method for indoor mobile robots. The method combines Curvature-Velocith Method(CVM) with a new directional method called the Lane Method. The Lane Method divides the environment into lanes taking the information on obstacles and desired heading of the robot into account ; then it chooses the best lane to follow to optimize travel along a desired heading. A local heading is then calculated for entering and following the best lane, and CVM uses this heading to determine the optimal translational and rotational velocity space methods, LCM yields safe collision-free motion as well as smooth motion taking the dynamics of the robot Xavier, show the efficiency of the proposed method.

• Journal of Mechanical Science and Technology
• /
• 제17권11호
• /
• pp.1693-1703
• /
• 2003

This paper presents a new local obstacle avoidance method for indoor mobile robots. The method uses a new directional approach called the Lane Method. The Lane Method is combined with a velocity space method i.e., the Curvature-Velocity Method to form the Lane-Curvature Method (LCM). The Lane Method divides the work area into lanes, and then chooses the best lane to follow to optimize travel along a desired goal heading. A local heading is then calculated for entering and following the best lane, and CVM uses this local heading to determine the optimal translational and rotational velocities, considering some physical limitations and environmental constraint. By combining both the directional and velocity space methods, LCM yields safe collision-free motion as well as smooth motion taking the physical limitations of the robot motion into account.

• 한국정밀공학회지
• /
• 제11권4호
• /
• pp.88-98
• /
• 1994

A new local path planning algorithm for free-ranging robots is proposed. Considering that a laser range finder has the excellent resolution with respect to angular and distance measurements, a simple local path planning algorithm is achieved by a directional weighting method for obtaining a heading direction of nobile robot. The directional weighting method decides the heading direction of the mobile robot by estimating the attractive resultant force which is obtained by directional weighting function times range data, and testing whether the collision-free path and the copen parthway conditions are satisfied. Also, the effectiveness of the established local path planning algorithm is estimated by computer simulation in complex environment.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
• /
• pp.105-110
• /
• 1999

This paper presents a local obstacle avoidance method for indoor mobile robots using Lane method and velocity Space Command approach. The method locates local obstacles using the information form multi-sensors, such that ultrasonic sensor array and laser scanning sensor. The method uses lane method to determine optimum collision-free heading direction of a robot. Also, it deals with the robot motion dynamics problem to reduce some vibration and guarantee fast movement as well. It yields translational and rotational velocities required to avoid the detected obstacles and to keep the robot heading direction toward goal location as close as possible. For experimental verification of the method, a mobile robot driven by two AC servo motors, equipped with 24 ultrasonic sensor array and laser scanning sensor navigates using the method through a corridor cluttered with obstacle.

• Journal of Electrical Engineering and Technology
• /
• 제12권4호
• /
• pp.1675-1682
• /
• 2017

This paper deals with three dimensional orientation estimation algorithm for an attitude and heading reference system (AHRS) based on nine-axis inertial/magnetic sensor signals. In terms of the orientation estimation based on the use of a Kalman filter (KF), the quaternion is arguably the most popular orientation representation. However, one critical drawback in the quaternion representation is that undesirable magnetic disturbances affect not only yaw estimation but also roll and pitch estimations. In this paper, a sequential direction cosine matrix-based orientation KF for AHRS has been presented. The proposed algorithm uses two linear KFs, consisting of an attitude KF followed by a heading KF. In the latter, the direction of the local magnetic field vector is projected onto the heading axis of the inertial frame by considering the dip angle, which can be determined after the attitude KF. Owing to the sequential KF structure, the effects of even extreme magnetic disturbances are limited to the roll and pitch estimations, without any additional decoupling process. This overcomes an inherent issue in quaternion-based estimation algorithms. Validation test results show that the proposed method outperforms other comparison methods in terms of the yaw estimation accuracy during perturbations and in terms of the recovery speed.

• 한국작물학회지
• /
• 제65권1호
• /
• pp.1-21
• /
• 2020

Association mapping is widely used in rice and other crops to identify genes underlying important agronomic traits. Most association mapping studies use diversity panels comprising accessions with various geographical origins to exploit their wide genetic variation. While locally adapted breeding lines are rarely used in association mapping owing to limited genetic diversity, genes/alleles identified from elite germplasm are practically valuable as they can be directly utilized in breeding programs. In this study, we analyzed genetic diversity of 179 rice varieties (161 japonica and 18 Tongil-type) released in Korea from 1970 to 2006 using 192 microsatellite markers evenly distributed across the genome. The 161 japonica rice varieties were genetically very close to each other with limited diversity as they were developed mainly through elite-by-elite crosses to meet the specific local demands for high quality japonica rice in Korea. Despite the narrow genetic background, abundant phenotypic variation was observed in heading time, culm length, and amylose and protein content in the 161 japonica rice varieties. Using these varieties in association mapping, we identified six, seven, ten, and four loci significantly associated with heading time, culm length, and amylose and protein content, respectively. The sums of allelic effects of these loci showed highly significant positive correlation with the observed phenotypic values for each trait, indicating that the allelic variation at these loci can be useful when designing cross combinations and predicting progeny performance in local breeding programs.

• 제어로봇시스템학회논문지
• /
• 제22권1호
• /
• pp.66-73
• /
• 2016

An Inertial Measurement Unit (IMU)-based Attitude and Heading Reference System (AHRS) can calculate attitude and heading information with long-term accuracy and stability by combining gyro, accelerometer, and magnetic compass signals. Motivated by this characteristic of the AHRS, this paper presents a Motion-Tracking and Localization (MTL) method for a person or walking robot using multi-AHRSs. Five AHRSs are attached to the two calves, two thighs, and waist of a person/walking robot. Joints, links, and coordinate frames are defined on the body. The outputs of the AHRSs are integrated with link data. In addition, a supporting foot is distinguished from a moving foot. With this information, the locations of the joints on the local coordinate frame are calculated. The experimental results show that the presented MTL method can track the motion of and localize a person/walking robot with long-term accuracy in an infra-less environment.

• 한국농림기상학회지
• /
• 제9권1호
• /
• pp.17-28
• /
• 2007

영남지역의 농업기후변화 양상을 살펴보고 기후변화에 대응하여 벼 재배의 안전성과 품질향상을 위한 기초 자료를 얻고자 영남지역 22개 기상대 및 기상관측소의 최근 10년($1996{\sim}2005$년) 기후값을 평년($1971{\sim}2000$년)과 비교하고 지역별 벼 생육 가능기간과 최적 출수기를 산정하였다. 영남지역의 최근 기후는 평년에 비하여 평균기온과 강수량은 상승하였으나 기온일교차와 일조시간은 감소하는 특징을 보였는데, 특히 $7{\sim}8$월의 기온은 오히려 낮아졌고, $8{\sim}9$월의 강수량이 현저히 증가하였으며, 기온 일교차와 일조시간은 $8{\sim}10$월에 걸쳐 크게 감소하는 경향이었다. 최근 10년의 벼 생육가능기간은 봉화의 171일부터 부산의 228일까지 매우 넓고 다양하였으며, 평년에 비하여 $1{\sim}13$일 정도 늘어났다. 고품질 쌀 생산을 위한 적정 출수기간은 평년과 비교하여 최근에 $1{\sim}3$일 정도 늘어났으며, 최대 기후등 숙량을 기준으로 추정한 최근 10년의 최적 출수기는 봉화의 7월 31일에서 부산, 마산, 통영의 9월 7일로 지역에 따라 차이가 심하였다. 봉화와 문경, 영덕을 제외한 최근 10년의 지역별 출수 최적일은 평년과 비교하여 거제와 마산, 안동, 의성에서는 변화가 없었고, 대부분의 지역에서 $1{\sim}8$일 정도 늦어진 것으로 분석되었다. 이러한 결과는 기후변화로 인하여 영남지역에서도 고품질 쌀 생산을 위한 지역별 벼 재배적기와 적정 출수기의 재설정이 필요하며, 특히 중만생종 벼 품종 육성 시 기후변화를 감안하여 출수기를 현재보다 늦출 필요가 있을 것으로 생각된다.

• 한국항공우주학회지
• /
• 제44권4호
• /
• pp.308-315
• /
• 2016

본 논문은 관성 항법 시스템(Inertial Navigation System)을 활용한 자세 및 방향 결정시스템(Attitude & Heading Reference System)의 성능을 향상시키기 위한 새로운 기법인, 순차적 측정 오차 공분산(Sequential Measurement Noise Covariance) 기법을 제시하였다. 관성 센서는 시간이 지남에 따라 발생하는 적분오차와 진동이나 가속구간과 같은 외란이 가해 졌을 때 성능이 저하된다는 단점이 있다. 특히, 저가의 관성 센서의 경우 이러한 현상이 더욱 두드러지게 나타난다. 이를 극복하기 위한 알고리즘들은 많이 존재한다. 하지만 가장 일반적으로 사용되는 확장 칼만 필터의 경우 가속도계를 사용할 때 측정값(Measurement)이 일정 범위를 넘어가면 센서값을 배제하는 방법을 사용한다. 본 논문에서 제안하는 기법은 범위를 설정하지 않고 과거의 데이터를 순차적으로 활용하여 측정값의 가중치를 변화하는 기법이다. 최종적으로 제안된 기법을 수치 시뮬레이션을 통해 검증하였다.

• 한국도서관정보학회지
• /
• 제40권1호
• /
• pp.297-316
• /
• 2009

본 연구에서는 최근 활발히 이용되고 있는 커뮤니티 주제 어휘의 특징을 선행연구인 ULIS-DL과 디지털오카야마 대백과(디지털강산대백과(デジタル岡山大百科))를 중심으로 알아보고, 이들 어휘들의 상호운용 모델을 일본의 동경도(東京都), 홋카이도(북해도(北海道)), 한국의 충청남도의 각 도청 홈페이지의 디렉토리 용어들을 이용하여 제안하였다. NDLSH(National Diet Library Subject Heading)와 NDC(Nippon Decimal Classification)를 스위칭 언어를 사용하여 다섯개의 어휘 매핑 모델을 제안하였다. 마지막으로, 각각의 모델들에 대한 평가 및 한계점에 관하여 매핑의 정확율과 재현율을 이용하여 논하였다.