• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.433-437
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• 1988

Direct measurement of the relative position between the end effector of robot and moving objects reduces difficulties caused by the joint encoder reading and transformation. For those purpose, the on-line sensing method using PSD sensor was developed in this paper. The sensor was calibrated on the precision table. Then, the relative position of a moving objects on the conveyor was measured while the robot was tracking the one.

• International Journal of Aeronautical and Space Sciences
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• 제12권1호
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• pp.24-36
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• 2011

A new approach for spacecraft absolute attitude estimation based on the unscented Kalman filter (UKF) is extended to relative attitude estimation and navigation. This approach for nonlinear systems has faster convergence than the approach based on the standard extended Kalman filter (EKF) even with inaccurate initial conditions in attitude estimation and navigation problems. The filter formulation employs measurements obtained from a vision sensor to provide multiple line(-) of(-) sight vectors from the spacecraft to another spacecraft. The line-of-sight measurements are coupled with gyro measurements and dynamic models in an UKF to determine relative attitude, position and gyro biases. A vector of generalized Rodrigues parameters is used to represent the local error-quaternion between two spacecraft. A multiplicative quaternion-error approach is derived from the local error-quaternion, which guarantees the maintenance of quaternion unit constraint in the filter. The scenario for bounded relative motion is selected to verify this extended application of the UKF. Simulation results show that the UKF is more robust than the EKF under realistic initial attitude and navigation error conditions.

• Journal of Mechanical Science and Technology
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• 제18권1호
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• pp.132-144
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• 2004

This paper presents a new method driving multiple robots to their goal position without collision. To consider the movement of the robots in a work area, we adopt the concept of avoidability measure. The avoidability measure figures the degree of how easily a robot can avoid other robots considering the velocity of the robots. To implement the concept to avoid collision among multiple robots, relative distance between the robots is proposed. The relative distance is a virtual distance between robots indicating the threat of collision between the robots. Based on the relative distance, the method calculates repulsive force against a robot from the other robots. Also, attractive force toward the goal position is calculated in terms of the relative distance. These repulsive force and attractive force are added to form the driving force for robot motion. The proposed method is simulated for several cases. The results show that the proposed method steers robots to open space anticipating the approach of other robots. In contrast, since the usual potential field method initiates avoidance motion later than the proposed method, it sometimes fails preventing collision or causes hasty motion to avoid other robots. The proposed method works as a local collision-free motion coordination method in conjunction with higher level of task planning and path planning method for multiple robots to do a collaborative job.

• 제어로봇시스템학회논문지
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• 제13권1호
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• pp.39-45
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• 2007

This paper proposes a method of container position measurement using automatic landing system that is estimated by a laser range finder. In the most of container position measurement methods, CCD cameras or laser scanners have been used to get the source data. However those sensors are not only weak for disturbances, for examples, the light, fog, and rain, but also the system cost is high. When the spreader arrives at the goal position, it is still swung by inertia or by wind effect. In this paper, the spreader swung data have been used to find the container position. The laser range finder is equipped in the front side of spreader. It can measure distance and relative position between spreader and container. This laser range finder can be rotated as desired by a motor. And a tilt sensor is equipped on the spreader to measure spreader sway. The relative position information between the spreader and a container using the laser range finder and tilt sensor is estimated through the geometrical analysis.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1712-1721
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• 2004

A method of measuring the thermal diffusivity of semi-infinite solid material at room temperature using photothermal displacement is proposed. In previous works, within the constant thickness of material, the thermal diffusivity was determined by the magnitude and phase of deformation gradient as the relative position between the pump and probe beams. In this study, however, a complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in semi-infinite solid materials. The influence of parameters, such as, radius and modulation frequency of the pump beam and the thermal diffusivity, was studied. We propose a simple analysis method based on the zero -crossing position of real part of deformation gradient and the minimum position of phase as the relative position between two beams. It is independent of parameters such as power of pump beam, absorption coefficient, reflectivity, Poisson's ratio, and thermal expansion coefficient.

• 대한전자공학회논문지SP
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• 제39권3호
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• pp.66-77
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• 2002

본 논문에서는 TMS320C80 멀티미디어 MVP(multimedia video processor)를 이용한 항법 변수 추출의 구현 기법에 관하여 연구하였다. 특히, 항법 변수 추출 시스템의 실시간 구현에 중요한 역할을 하는 상대 위치 추정 알고리듬의 실시간 구현 방법에 관하여 고찰한다. 두 지점에서 취득된 영상을 이용하는 상대위치 추정 알고리듬을 근간으로 하여, 방대한 양의 계산량을 감축하면서 고정 소수점 프로세서에 적합한 고속 알고리듬을 개발한다. 그런 다음, MVP 내의 4개의 병렬 프로세서(PP; parallel processor)를 이용하여 병렬 처리할 수 있도록 알고리듬을 재구성한다. 그 결과, MVP를 이용한 항법 변수 추출 시스템은 초당 30프레임을 처리할 수 있음을 확인하여, 실시간 구현 조건을 만족시킴을 알 수 있었다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.140-150
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• 2004

In this study, the effect of relative position of the blade for the fixed vane has been investigated on blade surface heat transfer. The experiments were conducted in a low speed stationary annular cascade, and heat transfer of blade was examined for six positions within a pitch. Turbine test section has one stage composed of sixteen guide vanes and blades. The chord length of the tested blade is 150 mm and the mean tip clearance of the blade having flat tip is about $2.5\%$ of the blade chord. For the detailed mass transfer measurements on the blade surfaces, a naphthalene sublimation technique was used. The inlet flow Reynolds number is fixed to $1.5{\times}10^5$. Complex heat transfer characteristics are observed on the blade surface due to various flow characteristics, such as separation bubble, relaminarization, transition to turbulence and leakage vortices. The distributions of velocity and turbulence intensity change significantly with the relative position due to the blockage effect of the blade. This causes the variation of heat transfer patterns on the blade surface. The results show that the flow near the leading edge get highly disturbed and deflected toward the either side of the blade when the blade leading edge is positioned close to the trailing edge of the vane. Therefore, separation bubble disappears on the pressure side and overall heat transfer on the relaminarization region is increased. But, due to reduced tip gap flow at the upstream region, the effect of leakage flow on the upstream region of the blade surface is weakened. Thus, the heat transfer characteristics significantly change with the blade positions.

• 한국융합학회논문지
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• 제11권3호
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• pp.45-52
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• 2020

본 연구에서는 현존하고 있는 잠금 해제 방식에서 보이는 문제점으로부터 출발해 보안성 및 사용성 측면에서 개선된 블라인드 인터랙션을 적용한 상대적 위치 기반 패턴 잠금 해제 방식을 제안하고 이론적 타당성을 고찰했다. 기존 숫자암호 잠금 해제 방식과 패턴 그리기 잠금 해제 방식과의 차이를 실험을 통해 확인하고 실용적 가치를 평가했다. 상대적 위치 패턴은 숫자 암호 보다 쉽게 기억되고 그리기 패턴과 비슷한 정도의 학습 용이성을 보여 주었고 타 방식에 비해 훔쳐보기 공격에 안전한 결과를 얻었다. 생체신호를 센싱 할 센싱 모듈을 사용할 필요 없이 터치스크린의 기본기능만으로 실현 가능하기에 적은 원가로 제작할 수 있다. 시각적 요소가 필요 없는 방식이기에 시각 장애인과 같은 특수 사용자들도 불편함 없이 사용할 수 있기에 실용적 가치도 상대적으로 높다.

• 센서학회지
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• 제31권3호
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• pp.156-162
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• 2022

This study estimates the relative position between body segments using segment orientation and segment-to-joint center (S2J) vectors. In many wearable motion tracking technologies, the S2J vector is treated as a constant based on the assumption that rigid body segments are connected by a mechanical ball joint. However, human body segments are deformable non-rigid bodies, and they are connected via ligaments and tendons; therefore, the S2J vector should be determined as a time-varying vector, instead of a constant. In this regard, our previous study (2021) proposed a method for determining the time-varying S2J vector from the learning dataset using a regression method. Because that method uses a deformation-related variable to consider the deformation of S2J vectors, the optimal variable must be determined in terms of estimation accuracy by motion and segment. In this study, we investigated the effects of deformation-related variables on the estimation accuracy of the relative position. The experimental results showed that the estimation accuracy was the highest when the flexion and adduction angles of the shoulder and the flexion angles of the shoulder and elbow were selected as deformation-related variables for the sternum-to-upper arm and upper arm-to-forearm, respectively. Furthermore, the case with multiple deformation-related variables was superior by an average of 2.19 mm compared to the case with a single variable.

• 인지과학
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• 제15권3호
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• pp.15-24
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• 2004

추적 눈 운동 동안에 순간적으로 노출되는 표적의 위치는 표적 주위에 참조자극이 존재하지 않을 때에 일반적으로 눈 운동 방향으로 왜곡되어 지각된다. 본 연구는 안정적이고 정적인 참조자극이 존재하는 경우에 순간적으로 노출되는 표적의 참조자극에 대한 상대적인 위치가 얼마나 정확하게 지각되는지를 검증하였다. 참조자극에 대한 표적의 상대적인 위치가 왜곡되게 지각되었으며 상대적인 위치 지각 왜곡의 양상이 참조자극과 표적의 상대적인 위치에 따라서 체계적으로 변화하였다. 동일한 실험결과가 추적 눈 운동의 방향이 상이하거나 참조자극과 표적의 다양한 물리적인 거리 조건에서도 일관되게 관찰되었다. 본 연구의 실험결과가 위치지각에 관하여 제안된 기존의 이론에 의해 어떻게 설명될 수 있는지를 논의하였다.