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Lee, Giuk,Jeong, Jay I.,Kim, Jongwon Marcel Dekker inc. 2016 MECHANICS BASED DESIGN OF STRUCTURES AND MACHINES Vol.44 No.4
<P>This paper presents the kinematic calibration of a two degree-of-freedom redundantly actuated parallel mechanism (RAPM), with the aim of eliminating contradicting control forces (CCF). The kinematic errors in the RAPM induce CCFs, especially in the case of decentralized individual position control, which is the standard control method used in industrial applications. The encoder indexing errors of the actuated joints are known to be of strong influence on the CCFs. Therefore, it is believed that the CCFs will be eliminated if the encoder indexing errors are corrected. We proved this through experiments. We performed the calibration using a projection technique, wherein we projected tracking error terms onto orthogonal complementary terms of the constraint Jacobian between the independent joints and actuated joints. Using this projection technique, the effect of tracking error terms from the joint stiffness and external force is eliminated. During the calibration process, the tracking errors in the actuated joints are measured. Using these errors, we derived the optimal values of the encoder indexing error by minimizing the objective function. We verified the calibration result by comparing the CCFs measured before calibration with those measured after calibration, for the case of individual PID position control. Our results confirmed that the calibration procedure of encoder indexing errors successfully reduces the average norm value of CCFs from 366N to 13N.</P>
Minimizing Energy Consumption of Parallel Mechanisms via Redundant Actuation
Giuk Lee,Sumin Park,Donghun Lee,Park, Frank C.,Jeong, Jay I.,Jongwon Kim IEEE 2015 IEEE/ASME transactions on mechatronics Vol.20 No.6
<P>This paper shows that redundant actuation can reduce the energy consumption of parallel mechanisms, in some cases by a considerable margin. A theoretical analysis for the energy-saving mechanism is elucidated, and an energy consumption model for a servo-motor system is proposed. Our hypothesis is experimentally verified with a widely used two degree of freedom parallel mechanism design driven by three actuators. Experimental results show that redundant actuation can reduce the electrical energy consumption of the actuators by up to 45% compared to the corresponding nonredundantly actuated version of the mechanism.</P>
High-Force Display Capability and Wide Workspace With a Novel Haptic Interface
Lee, Giuk,Hur, Sung-Moon,Oh, Yonghwan IEEE 2017 IEEE/ASME transactions on mechatronics Vol.22 No.1
<P>We present a novel haptic interface, named VirtuaPower, having a high-force display capability (FDC) and a wide workspace with a six-degree-of-freedom position measurement and FDC. The overall mechanism of VirtuaPower is designed based on a parallel pair of five-bar mechanisms supporting the end-platform. This novel mechanism enhances the high-FDC and overcomes the problem of small-size workspace, which are the pros and cons of parallel mechanisms, respectively. First, we present the conceptual design and prototype of VirtuaPower. Then, we formulate the forward kinematic and the constraint and space Jacobian. Using these formulations, we analyze two types of workspaces and FDC. In both analyses, VirtuaPower shows remarkable performances, especially in terms of its FDC, compared to other haptic interfaces having an equivalent size. In addition, we validate the static, step, and frequency responses of the force-display performance by performing experiments using the test bench of fixed end setup with a six-dimensional force/torque sensor. Finally, we evaluate the suitability of VirtuaPower as a haptic interface by realizing two types of virtual sphere walls and a virtual reality environment.</P>
Jeong, Giuk,Kim, Jekyung,Gunawan, Oki,Pae, Seong Ryul,Kim, Soo Hyun,Song, Jae Yong,Lee, Yun Seog,Shin, Byungha ELSEVIER SCIENCE 2017 Journal of Alloys and Compounds Vol.722 No.-
<P><B>Abstract</B></P> <P>Single-phase SnSe thin films were prepared via thermal co-evaporation using a Se thermal cracker. By carefully tuning the stoichiometry of the SnSe, we found that the composition range of single phase SnSe is very narrow, a Se/Sn ratio of 0.95–0.99; outside of this range secondary phases (metallic Sn or SnSe<SUB>2</SUB>) formed. Electrical properties were found to be very sensitive to even small changes in the stoichiometry. Three orders of magnitude difference in the carrier concentration was observed within the stoichiometry range for single-phase SnSe, which can be explained by changes in the shallow level defect density. To further control carrier concentration, we introduced In and Sb as counter-dopants into the SnSe thin films and found that they were deep level donors with the ionization fraction of ∼10<SUP>−4</SUP>. Finally, we demonstrate the potential of SnSe thin films as an absorber layer in photovoltaic applications. Our study demonstrates the importance of fine-tuning stoichiometry of SnSe to achieve desired electrical properties.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Single phase SnSe thin films are fabricated via thermal co-evaporation method. </LI> <LI> The range of the Se/Sn ratio for single phase SnSe is 0.95–0.99. </LI> <LI> Also, carrier concentration of films varied dramatically (10<SUP>15</SUP>–10<SUP>17</SUP> cm<SUP>−3</SUP>). </LI> <LI> Sb or In were found to work as counter-dopants to p-type SnSe. </LI> <LI> Working photovoltaic device based on SnSe thin films was reported. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
높은 유효하중 능력과 다양한 벽면전환 능력을 가진 다관절 등반로봇의 개발 및 추종제어
오종균(Jongkyun Oh),이기욱(Giuk Lee),김종원(Jongwon Kim),서태원(TaeWon Seo) 제어로봇시스템학회 2013 제어·로봇·시스템학회 논문지 Vol.19 No.10
Payload capacity and transition ability are essential for climbing robots to apply the robots to various applications such as inspection and exploration. This paper presents a new climbing robotic platform with multi-link structure of track-wheel modules to enhance payload capacity and transition ability, and its tracking controller design and experimental results. The compliances between track-wheel modules achieve stable internal and external transitions while the large adhesion area of the track-wheel module enhances the payload capacity of the robot. Kinematic model-based tracking controller is designed and implemented for autonomous internal transition, and the gains of the controller are optimized by experimental design. Experiments on the automatic internal transitions are performed and the results guarantee autonomous internal transition with little tracking error.