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Design and Modeling of an Image Stabilizing Device for Small Unmanned Ground Vehicle
Doo-Yeol Koh,Soo-Hyun Kim,Kyung-Soo Kim 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10
This paper addresses about an image stabilizing device for small unmanned ground vehicle (SUGV). Most SUGV’s have innate purpose of operating in harsh conditions where human can hardly visit, e.g., mountain area, crashed building and so on. In those environments, terrain is not normally flat and even. Therefore, various types of vibrations are incurred to SUGV which leads to fuzzy image output to operator, so the operator suffers from the remote control. Furthermore, the vibration is escalated as the SUGV moves faster. The primary purpose of this study is to reject those vibrations from the robot to the image capturing device. Throughout the sensor measurement during the SUGV operation, we found out that the vibration is significant in roll and pitch axis of the robot. From this point, we have made an effort to develop an image stabilizing device that is suitable for SUGV. This paper focuses about the design and modeling process as an early step of image stabilizer development. In this paper, the design approach and result is presented, and the dynamic model is derived for later controller design.
Mitigating shrinkage cracking in posttensioning grout using shrinkage-reducing admixture
Yoo, Doo-Yeol,Ryu, Gum-Sung,Yuan, Tianfeng,Koh, Kyung-Taek Elsevier 2017 Cement & concrete composites Vol.81 No.-
<P><B>Abstract</B></P> <P>This study aims to reduce the cracking potential of posttensioning high-performance grout (HG) through use of shrinkage-reducing admixture (SRA). With this regard, an HG mixture was initially developed to possess appropriate fluidity with low bleeding and settling. Various amounts of SRA were subsequently incorporated into the developed HG mixture at 1% and 2% by weight to the cementitious components. A widely used ordinary grout (OG) mixture was also considered for comparison. Test results indicated that the HG mixture exhibited similar flowability to the OG mixture, while imparting much better performance with regard to strength, bleeding, and settling. The addition of SRA to the HG mixture led to higher compressive and tensile strength values after 28 days, lower shrinkage strain, lower maximum internal temperature due to hydration heat, and delayed shrinkage cracking. On the other hand, the degree of restraint due to an uneven surface of duct and the filling capacity of the HG were insignificantly affected by the inclusion of the SRA. Complete filling of ducts was observed for the HG samples. The OG mixture exhibited the smallest shrinkage strain and the best performance with regard to shrinkage cracking resistance; however, the OG mixture resulted in insufficiently filled ducts, leading to atmospheric exposure of prestressing strands. Consequently, the HG mixture with 2% SRA was proposed to be most appropriate for posttensioning grout with regard to the several properties denoted above.</P>
Yoo, Doo-Yeol,Kim, Min-Jae,Kim, Soonho,Ryu, Gum-Sung,Koh, Kyung-Taek Elsevier 2018 Construction and Building Materials Vol.166 No.-
<P><B>Abstract</B></P> <P>This study investigated the effects of mixture proportion and curing condition on the mechanical and shrinkage behaviors of high-performance fiber-reinforced cementitious composites (HPFRCCs). Different water-to-binder (W/B) ratios and amounts of mineral admixtures, such as zirconium silica fume (Zr SF) and blast furnace slag were evaluated. The test results indicate that initial steam-heat curing accelerated the strength development and was sufficient to develop its full strength. The ultimate autogenous shrinkage was insignificantly affected by the curing conditions, but the heat curing accelerated the development of autogenous shrinkage. HPFRCC with a lower W/B ratio and greater amount of Zr SF exhibited higher autogenous shrinkage but lower drying shrinkage. In addition, the amount of total shrinkage of HPFRCC was more effectively reduced by providing heat curing when a higher W/B ratio and a smaller amount of Zr SF were used. There were no increases in the autogenous and drying shrinkage for HPFRCC immediately after finishing the initial heat curing, meaning that there is no possibility of shrinkage cracks forming in HPFRCC elements after the heat curing process. Finally, the autogenous shrinkage behaviors of HPFRCC were simulated with several prediction models from literature and an optimized model, considering equivalent age, was suggested.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ultimate autogenous shrinkage of HPFRCCs is insignificantly affected by curing condition. </LI> <LI> Lower W/B ratio and higher amount of Zr SF result in higher autogenous shrinkage but lower drying shrinkage. </LI> <LI> After heating curing, there are no increases of autogenous and drying shrinkage strains of HPFRCCs. </LI> <LI> Total shrinkage of SC150 and SC120 is effectively reduced by applying heat curing. </LI> </UL> </P>
Vibration Reduction Control of Omnidirectional Mobile Robot with Lift Mechanism
Jinseong Park,Doo-Yeol Koh,Jeong-Jung Kim,Chang-Hyun Kim 제어로봇시스템학회 2021 제어로봇시스템학회 국제학술대회 논문집 Vol.2021 No.10
An omnidirectional mobile robot with lift mechanism has been developed to assist worker to transport heavy goods placed on high position. However, as the center of gravity heightens and the stiffness decreases with introducing the lift mechanism, and the suspension is adopted for consistent contact between mecanum wheel and the ground, a large amount of vertical vibration is inevitable. In this paper, the simultaneous controller for the driving velocity tracking and vibration reduction without additional actuators is developed based on a combined model with longitudinal and vertical motion, i.e. a suspended cart-pole inverted pendulum model. Proper Filters were designed to effectively remove uninterested characteristics such as mecanum wheel roller contact vibration and static inclination so that the performance of the vibration reduction controller can be optimized. From the experimental results, the performance of the proposed method is verified that the magnitude and time of residual vibration greatly reduced.
모델 예측 제어를 이용한 높은 질량 중심을 가지는 전방향 이동 로봇의 진동 저감 제어
박진성(Jinseong Park),고두열(Doo-Yeol Koh),김정중(Jeong-Jung Kim) 제어로봇시스템학회 2021 제어·로봇·시스템학회 논문지 Vol.27 No.10
Autonomous mobile robots equipped with long-stroke lift modules have been developed to assist human workers to transport high positioned heavy objects in the field of logistics. A large amount of rolling vibration during acceleration or deceleration when driving is inevitable for a robot with a high center of mass and low stiffness mechanism. In this study, the simultaneous control of reference velocity tracking and vibration reduction, only using driving motors, is proposed based on a suspended cart-pole inverted pendulum model that combines velocity and vertical vibration motion. A model predictive controller was adopted to account for constraints that prevented the object from slipping when placed atop the lift by saturating the magnitude of the rolling angular acceleration. The simulation results verified that the residual vibration time and magnitude significantly decreased with the proposed controller compared to the controller accounting for driving velocity alone. Additionally, object slippage prevention was ensured with taking minimal loss of the reference velocity tracking performance.
소형 무인주행로봇에 탑재되는 EOD 매니퓰레이터 설계에 대한 연구
고두열,이승호,이준성,황기상,김수현,Koh, Doo-Yeol,Lee, Seung-Ho,Rhee, Joon-Seong,Hwang, Ki-Sang,Kim, Soo-Hyun 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.5
In this paper, mechanism design of the explosive ordnance disposal(EOD) manipulator for small unmanned ground vehicle(SUGV) is presented from the conceptual to detailed design. EOD manipulator has been widely developed in the world due to the growing threat of the improvised explosive devices at war. It has distinctive characteristics, such as small size and high loading performance, compared to the industrial manipulator which is fixed on the floor. Design of new EOD manipulator must take into account various functional requirements and constraints simultaneously. We focused on developing the EOD manipulator that has suitable size for the SUGV and maximum 15kg payload capacity. Design approach taken in this paper is based on axiomatic design procedure and comparison among many possible candidates of each joint structure to obtain appropriate entire structure of EOD manipulator.
윤병호(Byungho Yoon),정태일(Taeil Chung),고두열(Doo-Yeol Koh),김수현(Soohyun Kim) 제어로봇시스템학회 2012 제어·로봇·시스템학회 논문지 Vol.18 No.3
Mobility is one of the most important issues for search and rescue robots. To increase mobility for small size robot we have focused on the mechanism and algorithm inspired from centipede. In spite of small size, using many legs and flexible long body, centipede can overcome high obstacles and move in rough terrains stably. This research focused on those points and imitated their legs and body that are good for obstacle negotiation. Based on similarity of a centipede’"s legs and tracks, serially connected tracks are used for climbing obstacles higher than the robot’"s height. And a centipede perceives environments using antennae on its head instead of eyes. Inspired from that, 3 IR sensors are attached on the front, top and bottom of the first module to imitate the antenna. Using the information gotten from the sensors, the robot decides next behavior automatically. In experiments, the robot can climb up to 45 cm height vertical wall and it is 600 % of the robot’"s height and 58 % of the robot’"s length.