Research on the kinematic calibration of the 3-PTT parallel mechanism

Liang'en Huang,Minfang Chen,Shigao Zheng,Chaoyin He,Enxiao Zhu,Yongxia Zhang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

Most of the kinematic calibration methods of parallel mechanisms only consider the geometric error of the mechanism, and the calibration effect is poor. To improve the calibration effect, this paper takes the 3-PTT (3-prismatic hook hook) parallel mechanism as the research object and proposes a kinematics calibration method based on the normalized representation model of the geometric error and non-geometric error of the mechanism. First, the degree of freedom of the mechanism is analyzed, its kinematics positive and negative solutions are solved, and its singularity is analyzed. Secondly, a normalized characterization method of mechanism geometric errors and non-geometric errors is proposed, and an error model without redundant parameters is constructed. The end motion error of the machine is measured by laser tracker, and the objective function is constructed. The genetic algorithm is designed to solve the minimum value of the objective function, and the normalized error of the mechanism is identified. By comparing with the recent methods, the better identification performance of the algorithm in this paper is verified. Finally, the kinematics model was corrected according to the identification results. After the calibration was completed, the movement errors of the end of the mechanism along each coordinate axis were reduced by more than 99 %. Compared with other calibration methods, the better calibration performance of the method in this paper is verified.

단일장치로 발사환경구속 및 결함안전기능이 가능한 전개수납형 교정 메커니즘의 기능검증

이명재(Myeong-Jae Lee),김태규(Tae-Gyu Kim),조문신(Mun-Shin Jo),오현웅(Hyun-Ung Oh) 한국항공우주학회 2016 韓國航空宇宙學會誌 Vol.44 No.10

우주용 영상센서의 비균일 출력특성 교정을 통한 영상품질향상을 목적으로 탑재교정장치가 요구된다. 탑재교정장치는 균일한 온도정보 제공을 위한 흑체를 비롯하여, 흑체로의 지향성 확보를 위하여 전개/수납 기능이 포함되는 교정 메커니즘으로 구성된다. 이 중, 교정 메커니즘은 궤도상에서 구동장치의 결함 발생 시 주광경로 확보를 위한 결함안전 기능이 요구된다. 추가적으로, 구동부에 대한 발사환경에서의 구조건전성 확보가 필수적이다. 본 논문에서는 단일장치로 발사환경 구속 및 결함안전 기능 구현이 가능한 전개수납형 교정 메커니즘을 제안하였다. 상기 제안한 메커니즘의 기능모델을 통한 동작 기능시험을 수행하여 설계의 유효성을 입증하였다. Spaceborne imaging sensors require periodic calibrations using an on-board calibration device for an image quality of observation satellites. The on-board calibration device consists of a blackbody to provide uniform radiance temperatures and calibration mechanism with a function of stow and deploy to target the blackbody during the calibration. Among these devices, the calibration mechanism is required to implement a fail-safe function to prevent blocking of the main optical path when the mechanism stops at a certain position during on-orbit calibration. In addition, structural safety of the mechanical driving part of the mechanism within the launch environment must be guaranteed. In this study, we proposed a deploy/stow-type calibration mechanism that provides launch-lock and fail-safe function. The effectiveness of the functionality of the proposed mechanism was validated through functional test using engineering model.

공간오차 측정을 통한 6자유도 병렬기구의 보정

오용택(Yong-Taek Oh),아궁 샴수딘 사라기(Agung. S. Saragih),김정현(Jeong-Hyun Kim),고태조(Tae-Jo Ko) 한국기계가공학회 2012 한국기계가공학회지 Vol.11 No.3

This paper introduces the kinematic calibration method to improve the positioning accuracy of a parallel mechanism. Since all the actuators in the parallel mechanism are controlled simultaneously toward the target position, the volumetric errors originated from each motion element are too complicated. Therefore, the exact evaluation of the error sources of each motion element and its calibration is very important in terms of volumetric errors. In the calibration processes, the measurement of the errors between commands and trajectories is necessary in advance. To do this, a digitizer was used for the data acquisition in 3 dimensional space rather than arbitrary planar error data. After that, the optimization process that was used for reducing the motion errors were followed. Consequently, Levenberg-Marquart algorithm as well as the error data acquisition method turned out effective for the purpose of the calibration of the parallel mechanism.

결함안전 기능을 고려한 교정 반사경 구동장치

이경민(Kyong-Min Lee),오현웅(Hyun-Ung Oh) 한국항공우주학회 2011 韓國航空宇宙學會誌 Vol.39 No.7

일반적으로 탑재 교정을 위한 교정 반사경 구동장치는 교정임무 수행 시에는 주광경로상의 전개위치로 반사경을 구동하며, 교정 후에는 주광경로와 이격된 수납위치로 반사경을 구동한다. 교정 반사경 구동장치의 결함 발생 시에는 반사경이 전개된 상태로 남아 주광경로를 차단하지 않도록 반사경을 강제 수납한다. 본 논문에서 제안한 결함 안전장치를 가지는 교정용 반사경 구동장치는 구동을 위한 스텝모터, 전개 및 수납 상태확인을 위한 마이크로 스위치, 베어링과 스프링의 기능을 동시에 갖는 피봇베어링 등으로 구성된다. 본 논문에서는 상기의 기능을 갖는 교정 반사경 구동장치 구현을 위한 구동장치 구성을 제안하였으며, 구성요소의 최적화 설계치를 도출하고 기능시험을 통해 결함안전 기능을 갖는 교정 반사경 구동장치의 유효성을 검증하였다. Calibration mirror mechanism has been widely used for on-board calibration with black body. The calibration mirror is deployed to reflect the radiation energy from the black body to the image sensor for calibrating the sensor system. After the calibration, the calibration mirror is stowed not to hide a main optical path. It also has a fail-safe function which can stow the mirror by just removing the input power of motor when the calibration mirror is stopped at certain position during the calibration. In the present work, the operation concept, design, torque analysis and functional test results of the calibration mirror mechanism with the aforementioned function have been introduced and investigated.

External Kinematic Calibration of Hybrid Kinematics Machine Utilizing Lower-DOF Planar Parallel Kinematics Mechanisms

Abdur Rosyid,Bashar El-Khasawneh,Anas Alazzam 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.6

This paper presents the implementation of nonlinear least squares and iterative linear least squares algorithms for external kinematic calibration of a hybrid kinematics machine composed of two 3PRR planar parallel kinematics mechanisms by utilizing a laser tracker. First the hand-eye and robot-world transformations were obtained by a separable closed-form solution and refi ned by the nonlinear least squares. Subsequently, the geometric parameters of the machine’s mechanisms were estimated using the two algorithms. Due to the rank defi ciency, we implemented the nonlinear least squares algorithm through a subset selection approach in which we performed the estimation in two steps. We iterated the closed-form solution of the linear least squares until the solution converges to the actual values. We have shown that the nonlinear least squares algorithm successfully refi ned the hand-eye and robot-world transformations and outperformed the iterative linear squares algorithm in the estimation of the geometric parameters of the mechanisms.

Development and kinematic calibration for measurement structure of a micro parallel mechanism platform

강득수,서태원,김종원 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.4

This paper presents a micro-positioning platform based on a unique parallel mechanism developed by the authors. The platform has a meso-scale rectangular shape whose size is 20 x 23 mm. The stroke is 5 mm for both the x- and y-axes and 100 degrees for the α-axis. The platform is actuated by three sets of dual stage linear actuators: a linear motor for rough positioning and a piezo actuator for fine positioning. The developed micro-positioning platform has a measurement system that consists of three linear sensors. The position and orientation values of the movable platform can be measured directly and used in a feedback control system. Selecting 18 kinematic error parameters of a measurement system (feedback control system), a two-stage kinematic calibration method is proposed. Constant error parameters are found in the first stage and variable error parameters are found in the second stage of kinematic calibration. After kinematic calibration the position error is reduced to within 0.5㎛ and error reduction rate is over 90%.

Self Calibration of the Thermo-Mechanical Analyzer

Kweonho Kang,Kwilim Lee,Byeongjoo Yoon,Seokmin Yoon 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

NFDC (Nuclear Fuel and materials Data Center) is designated as a one of the data center of National Standard Reference Center from Ministry of Trade Industry and Energy at Dec. 30 2008. The fields of designation were nuclear fuel and energy materials. NFDC produces standard reference data of nuclear fuel and materials. To ensure reliability of experimental data uncertainty should be estimated. There are two kinds of uncertainty: A-type uncertainty from tester and B-type uncertainty from experimental equipments. To reduce the former, the measurement should be repeated for sufficient amount of times, and to reduce the latter type uncertainty all equipment have to be calibrated. In this study self calibration process of thermo-mechanical analyzer (TMA) was established to ensure the B-type uncertainty. The self calibration was performed using the standard reference material and correction factor was obtained. The correction factor was defined as the ratio of the thermal expansion value of the standard reference material reported in the certificate and the thermal expansion value measured using TMA. It is believed that the uncertainty evaluation process of TGA data developed in this study will be helpful for increasing reliability and stability evaluation of nuclear fuel and spent fuel.

기계적 교정에 의한 강재의 소재특성 변화에 관한 연구

김성배,김상섭,백기열 한국방재학회 2020 한국방재학회논문집 Vol.20 No.3

Steel elements exhibit varying characteristics during site installation after shop manufacturing. There may be a mix-up owing to unclear management methods for transport, and deformation might occur during field installation. Moreover, the technical basis for evaluating repair methods is narrow. In this study, variations in material properties after performing mechanical calibration were determined for widely used steel types, such as SS400 and SM490, in which thicknesses of 30 mm and less are frequently used on sites. The test results showed that the mechanical calibration in unheated and thermal heating cases increased the yield strength and tensile strength of steel, and the Korea Standard value was satisfied. A yield ratio of approximately 85% or less was obtained, indicating sufficient toughness. In addition, variations owing to thermal heating did not occur when temperatures below 650 °C were applied. 강구조는 공장제작 후 현장설치 하는 제작 특성으로 운반 및 현장설치 과정에서 발생하는 변형 등에 대한 관리방안이 불명확하여현장감독자 및 제작자 간에 약간의 불협화음이 발생하는 경우가 있다. 또한 보수방법에 대한 기술적 판단근거가 적은 것이사실이다. 이에 본 연구에서는 현장에서 많이 사용되는 30 mm 이하의 판재(30 mm, 12 mm)와 가장 일반적으로 사용되는강종(SS400, SM490)에 대해 교정 후 소재특성의 변화 등을 시험으로 확인하였다. 시험결과 기계적 교정(비가열교정과 가열교정) 은 강재의 항복강도와 인장강도를 상승시키나 KS 규정 값은 만족하며, 항복비도 85% 이하를 나타내어 충분한 인성을 확보할수 있을 것으로 판단된다. 또한 650 ℃ 이하의 온도로 관리하면, 가열교정에 의한 조직변화는 발생하지 않을 것으로 판단된다.

용해실리카의 기준경도를 이용한 나노 압입시스템의 실험적 교정

이윤희 ( Yun Hee Lee ),안승민 ( Seung Min Ahn ),김주영 ( Ju Young Kim ),박찬평 ( Chan Pyung Park ),장희광 ( Hee Kwang Jang ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.3

Indirect calibration of a nanoindentation system was performed by deriving a reference loading curve. This reference load-depth relationship was accomplished by assuming a perfect nanoindentation test on an ideal reference material; if all components in a nanoindentation system are well calibrated and the reference material has unique hardness and Young’s modulus, the indentation depth can be formulated with a function of the indentation load having two parts of contact and surrounding elastic depths. Substituting both the hardness and Young’s modulus of a fused silica into the derived function, the reference loading curve was plotted and directly compared with experimental data of the fused silica measured by two commercial nanoindenters. All indentation loading curves showed leftward shifts compared to the reference loading curve, and this is discussed, offering two reasons for the result, system compliance and indenter apex geometry.(Received January 6, 2014)

마이크로 병렬기구 플랫폼의 기구학적 보정

강득수(Deuksoo Kang),김종원(Jongwon Kim) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월

This paper describes the mechanism of parallel micro machine platform and its feedback control system for acquiring high accuracy. The parallel micro machine platform that has developed has 5x5x5 work-space and sub-micron accuracy. For the high accuracy, the feedback control system is important but errors in machining and assembling are inevitable. Kinematic calibration is important for this reason. In this paper, various error components are introduced and the effects of error component are analyzed.