좌표변환 기반의 두 자세 정렬 기법 비교

이정근 ( Jung-keun Lee ),정우창 ( Woo-chang Jung ) 한국센서학회 2019 센서학회지 Vol.28 No.1

Inertial measurement units (IMUs) are widely used for wearable motion-capturing systems in the fields of biomechanics and robotics. When the IMUs are combined with optical motion sensors (hereafter, OPTs) for their complementary capabilities, it is necessary to align the coordinate system orientations between the IMU and OPT. In this study, we compare the application of two coordinate transformation- based orientation alignment methods between two coordinate systems. The first method (M1) applies angular velocity coordinate transformation, while the other method (M2) applies gyroscopic angle coordinate transformation. In M1 and M2, the angular velocities and angles, respectively, are acquired during random movement for a least-square algorithm to determine the alignment matrix between the two coordinate systems. The performance of each method is evaluated under various conditions according to the type of motion during measurement, number of data points, amount of noise, and the alignment matrix. The results show that M1 is free from drift errors, while drift errors are present in most cases where M2 is applied. Thus, this study indicates that M1 has a far superior performance than M2 for the alignment of IMU and OPT coordinate systems for motion analysis.

효율적인 지적재조사를 위한 지적좌표의 세계좌표 변환 정확도 향상 방안

박연수(Bak Yeon Su),홍성언(Hong Sung Eon),박기헌(Park Ki Heon) 한국지적학회 2014 한국지적학회지 Vol.30 No.3

본 연구에서는 기존 좌표변환 방법을 이용해 지역좌표체계를 세계좌표체계로 변환하고 이에 대한 정확도 분석한 후 세계좌표계를 이용한 현장 측량을 실시하였다. 그리고 변환좌표와 실측좌표를 이용한 추가적인 좌표변환 작업 및 분석을 통해 좌표변환의 정확도 향상 방안을 제시하였다. 연구결과, 실험지역의 1차 변환결과 모든 도면 307장 중 학림지구를 제외한 좌표변환의 표준편차가 평균 X=0.05m, Y=0.05m로 나타나 매우 양호하게 산출되었다. 이러한 1차 분석결과를 기초로 월송지구 내 실측한 4구역에 20점을 선정하였다. 그리고 구역별 외곽에 위치한 4점을 공통점으로 이용해 2차 세계좌표 변환을 시행한 결과 작지만 현장 경계복원한 점과의 이격은 물론 필지의 둘레길이(면적)의 차이가 감소함을 알 수 있었다. In this study, we carried out a site survey after an analysis accuracy of the World Geodetic system which is transformed from the cadastral coordinate system using the existing method of coordinate transformation. Furthermore, we suggested the method of the improving accuracy of a coordinate transformation through an additional coordinate conversing and analysis using the points of converted and measured coordinate. Based on the frist conversion in the study area, the standard deviations for the conversion of coordinates in 307 maps except the zone of HAKRIM were calculated satisfactorily as X=0.05m and Y=0.05m. Based on the results of the first analysis, 20 points were selected in the surveyed 4th district in the zone of WAULSONG. Moreover, we could notice the minute decrease of the differences in the restored boundary points and the difference of the perimeter(area) of parcel as the result of the second conversion to World Geodetic System using the 4 common points located at the boundary of districts respectively.

코사인 법칙과 3차원 좌표 변환을 이용한 단사진의 후방교회법

홍송표,최한승,김의명 한국측량학회 2019 한국측량학회지 Vol.37 No.3

사진측량에서 단사진의 후방교회법은 이미 알고 있는 카메라의 내부표정요소, 지상좌표, 사진좌표를 이용하여 촬영당시 카메라의 위치와 자세에 해당하는 외부표정요소를 결정하는 방법이다. 본 연구에서는 코사인 법칙과 선형식기반의 3차원 좌표변환식을 이용하여 카메라의 외부표정요소를 결정할 수 있는 단사진의 공간후방교회법 알고리즘을 제안하였다. 제안한 알고리즘은 먼저 렌즈왜곡이 보정된 정규좌표를 코사인 법칙을 이용하여 지상좌표와 이에 대응되는 정규좌표간의 축척을 계산하였다. 그리고 나서 축척을 고려한 정규좌표와 지상좌표를 이용하는 선형방정식 기반의 3차원 좌표변환식을 적용하여 외부표정요소를 결정하였다. 제안한 알고리즘은 비선형방정식으로 편미분이 필요하나 지상좌표의 조합 중 가장 긴 거리를 구하여 각 지상좌표에 나누는 방법을 이용하여 초기값에 민감하지 않은 장점이 있었다. 또한, 세 점을 이용하여도 외부표정요소를 결정할 수 있기 때문에 기준점의 기하학적 배치에 안정적인 장점이 있었다. In photogrammetry, single photo resection is a method of determining exterior orientation parameters corresponding to a position and an attitude of a camera at the time of taking a photograph using known interior orientation parameters, ground coordinates, and image coordinates. In this study, we proposed a single photo resection algorithm that determines the exterior orientation parameters of the camera using cosine law and linear equation-based three-dimensional coordinate transformation. The proposed algorithm first calculated the scale between the ground coordinates and the corresponding normalized coordinates using the cosine law. Then, the exterior orientation parameters were determined by applying linear equation-based three-dimensional coordinate transformation using normalized coordinates and ground coordinates considering the calculated scale. The proposed algorithm was not sensitive to the initial values by using the method of dividing the longest distance among the combinations of the ground coordinates and dividing each ground coordinates, although the partial derivative was required for the nonlinear equation. In addition, since the exterior orientation parameters can be determined by using three points, there was a stable advantage in the geometrical arrangement of the control points.

좌표변환 오차를 고려한 MRA 임계기준

채상현,강형민,오세종,이관중 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.11

본 연구에서는 좌표변환시 발생하는 오차를 고려한 MRA의 임계기준을 제시한다. 정렬격자계로 외부유동해석시 body-fitted 형태의 격자를 작성하기 때문에 Cartesian좌표계에서 일반화된 좌표계로 좌표변환을 수행한다. 이때 좌표변환과정에서 오차가 발생하게 되는데, 기존 MRA의 임계기준은 이러한 오차를 고려하지 않았기 때문에 물성치의 변화와 상관없이 격자의 skewness, aspect ratio가 크게 변하는 부분도 adaptive dataset에 포함된다. 본 연구에서는 좌표변환에서 발생하는 오차를 고려하여, 격자변형이 큰 부분에서는 임계기준치가 높아져서 dataset에 격자가 포함되지 않도록 해서 격자변형에 관계없이 유동장 변화가 두드러진 부분만 dataset에 포함되도록 개선하였다. 이를 검증하기 위해 수행한 2차원 와류이동 문제에서 개선된 임계기준으로 MRA 수행시, 격자변형이 큰 부분의 격자가 dataset에 포함되지 않아서 격자압축률이 약 2배 증가함을 보였다. We suggest novel thresholding criterion of MRA for considering numerical errors from the coordinate transformation. In structured grid system, the coordinate transformation from Cartesian coordinate to generalized coordinate is mandatory due to the use of body-fitted grids on external flow applications. Conventional thresholding criterion of MRA doesn’t take account of errors from coordinate transformation; compression ratio is deteriorated by adding grids with high skewness or aspect ratio into the adaptive dataset. To resolve this problem, the thresholding criterion is modified to increase the value of criterion in the region of high skewness or aspect ratio. In the validation case of 2D moving vortex problem, the suggested criterion improves compression ratio as two times of conventional criterion by excluding the points where has high skewness or aspect ratio.

지구자전에 대한 정밀좌표변환 알고리듬 분석

김정래,노정호,윤성환 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11

위성체 궤도계산을 위해서는 지구중심 관성좌표계로 위치계산에 필요한 수치적분을 수행하게 되는데, 정밀지구중력 등 동력학모델을 사용하기 위해서는 지구고정좌표계로의 변환이 필요하게 된다. 본 연구에서는 정밀한 좌표변환에 필요한 세차운동, 장동운동 및 극운동에 대한 조사를 수행한 두 계산 프로그램을 개발하고, 주요 운동요소에 의한 좌표변환 오차를 분석하였다. Computation of Earth satellite orbit requires numerical integration in Earth centered inertial coordinates. The use of precision Earth gravity field model requires use os Earth centered earth fixed coordinates, and a precision transform between the two coordinate systems is required. This research studies the coordinate transform models; precession, nutation, and polar motion. A coordinate transform program is developed and coordinate difference due to model components are discussed.

Task Space Control of a Welding Robot Using a Fuzzy Coordinator

Mohammad Mehdi Fateh,Arash Khatamianfar,Shahab Shahrabi Farahani 제어·로봇·시스템학회 2010 International Journal of Control, Automation, and Vol.8 No.3

This paper introduces a fuzzy coordinator as a novel application of fuzzy controller. A control transformation from the task space to the joint space is required to control a robot manipulator in the task space. Because the actuators operate in the joint space while the manipulator is controlled in the task space. A conflict between two spaces is produced due to using an imprecise transformation. Fuzzy coordinator coordinates two spaces by modifying the control transformation affected by uncertainties. The fuzzy coordinator is designed simply and operates as a robust controller. The role of fuzzy coordinator is analyzed and illustrated in the robust control of a welding robot in the task space. A cir-cular trajectory is planned for a welding task performed by a SCARA robot. The fuzzy coordinator is then used to improve the performance of control system affected by imprecise transformations including the imprecise path transformation and the approximated feedback linearization.

Analysis of eccentricity in the ball bar measurement

Lee, Dong-Mok,Cha, Young-Taek,Yang, Seung-Han 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1

The ball bar is widely used in machine tool measurement because it is convenient and cost effective. Eccentricity exists due to machine errors and installation errors during a ball bar test, and the coordinate transformation method is used to remove eccentricity. However, distortion of data (i.e., ovalization) becomes large when eccentricity relative to the radius of a circle cannot be ignored. The number of sampled data for the total angle of circular path is used to estimate the actual rotating angle of the ball bar during measurement. To prevent distortion of data, actual rotating angles of the ball bar must be estimated exactly. In this paper, geometric relations of the ball bar measurement model are described based on the poses of two reference coordinate systems (ball bar and nominal coordinate system). The proposed algorithm calculates the actual rotating angle of the ball bar using geometric conditions and removes eccentricity through coordinate transformation.

구면 파노라마 영상에서의 평면 패턴의 기하 변환 추정

김보성(Bosung Kim),박종승(Jong-Seung Park) Korean Institute of Information Scientists and Eng 2015 정보과학회논문지 Vol.42 No.10

A spherical panoramic image does not conform to the pin-hole camera model, and, hence, it is not possible to utilize previous techniques consisting of plane-to-plane transformation. In this paper, we propose a new method to estimate the planar geometric transformation between the planar image and a spherical panoramic image. Our proposed method estimates the transformation parameters for latitude, longitude, rotation and scaling factors when the matching pairs between a spherical panoramic image and a planar image are given. A planar image is projected into a spherical panoramic image through two steps of nonlinear coordinate transformations, which makes it difficult to compute the geometric transformation. The advantage of using our method is that we can uncover each of the implicit factors as well as the overall transformation. The experiment results show that our proposed method can achieve estimation errors of around 1% and is not affected by deformation factors, such as the latitude and rotation.

An Improved and Efficient Analytical Model for Magnetic Field Calculation in Linear Permanent Magnet Machines

Baocheng Guo,Rong Guo,Hengzai Hu,Jianping Shi,Chunmei Feng 한국자기학회 2022 Journal of Magnetics Vol.27 No.1

A simple and improved analytical model (AM) for linear permanent magnet synchronous machine (LPMSM) based on the correction factor is presented in this paper. A slotless linear permanent magnet machine (PLPM) with AM developed in Cartesian coordinate is selected to investigate. Consequently, the fitting equations of curvature factors for the permanent magnet and armature are obtained. The subdomains for LPMSM are simplified from 6 down to 3 domains based on curvature equations. The magnetic flux density and force show that the proposed approach agrees with the finite element (FE) model. Moreover, the reduced calculation domains and harmonic orders make AM proposed in the paper much faster. The main contribution of the work is to present a simple strategy for coordinate transformation and calculation strategy for LPMSM, which provides guideline for designers to investigate the machines developed in Cartesian coordinate.

論文(논문) : 정밀좌표변환 및 중력가속도 계산 알고리듬 분석

김정래 ( Jeong Rae Kim ),노정호 ( Jeong Ho Noh ) 한국항공운항학회 2011 한국항공운항학회지 Vol.19 No.4

Inertial navigation systems requires gravity model to compute gravity acceleration and its trajectory accuracy depends on the gravity model accuracy especially for a long range flight. The gravity model accuracy is important for satellite orbit prediction as well. The precision gravity model requires a precision coordinate transformation between inertial and Earth fixed coordinates. Precision gravity acceleration algorithms with a coordinate transform are studied and a computer program is developed. The effects of individual model components on trajectory error are analyzed.