Second order hold and taylor series based discretization of SISO input time-delay systems

Second order hold is a method that enables the discretization of input-driven nonlinear systems to be carried out with high precision. A new discretization scheme combining second order hold with the Taylor-series is proposed. The sampled-data representation and mathematical structure are explored. Both exact and approximate sampled-data representations are described in detail. The performance of the proposed algorithm is evaluated for three different systems. Various sampling rates, delay times and truncation orders of the Taylor-series are considered to investigate the proposed method. The results demonstrate that the proposed scheme is practical and easy to use for time-delay systems. Comparisons between the second, first and zero orders are given to show the advantages of the proposed method. This paper was recommended for publication in revised form by Associate Editor Kyongsu Yi Zheng Zhang received a B.S. degree in Mechanical Engineering from Chang’an University in 1994. After four years work in AVIC I XI’AN AERO-EN-GINE (GROUP) LTD., he went on to receive his M.S. and Ph.D. degrees from Xi’an Jiaotong University in 2001 and 2005, respectively. Dr. Zhang is currently a lecturer at the School of Mechanical Engineering at Xi’an Jiaotong University, China. He is currently serving as a postdoctoral researcher of School of Electronics and Information, Chonbuk National University, Korea. Dr. Zhang’s research interests are in the area of nonlinear time-delay systems, intelligent transportation systems, intelligent vehicles, and robotics. Kil To Chong received the PhD degree in mechanical engineering from Texas A&M University, U.S.A., in 1995. Currently, he is Professor in School of Electronics and Information Engineering, Chon-buk National University, Jeonju, Korea. He is editor in chief of journal of IEEK (SC). He is interested in the area of the Motor Fault Detection, Network System Control, Nonlinear System with Time Delay Control, Robotics and Neural Networks.     

Novel scan path generation method based on area division for SFFS

A solid freeform fabrication (SFF) system using selective laser sintering (SLS) is currently recognized as a leading process of fabrication using variable materials, and SLS extends the application to machinery and automobiles. Due to the time delay in the sintering process, shrinkage and warping often occur. Curling also occurs due to laser and scan delays. These problems affect not only the accuracy of the fabricated product but also the total system efficiency. These deficiencies can be overcome by reducing the total processing time of the SFF system. To accomplish this, the laser scanning time, from mark (laser on) to jump (laser off), must be reduced as it contributes the major part of the total processing time. This can be done by employing area division scan path generation, which promotes digital efficiency. A simulation and an experiment was carried out in this study to evaluate the developed scan path method. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Kyung-Hyun Choi received his B.S. and M.S. degrees in Mechanical Engineering from Pusan National University, Korea, in 1983 and 1990,. He then received his M.S. and Ph.D. degrees from University of Ottawa in 1995. Dr. Choi is currently a professor at the School of Mechanical Engineering at Cheju National University, Korea. His research interests include micro-machining, printed Electronics. Hyung-Chan Kim received his B. S. and M. S. degrees in Electronics Engineering from Cheju National University, Korea, in 2006 and 2008, respectively. Mr. Kim is currently a Ph.D. candidate at the School of Electronics Engineering at Cheju National University, Korea. His research interests include RP System, micro-machining, printed Electronics. Yang-Hoi Doh received his B.S. and M.S. degrees in Electronics Engineering from KyungBuk National University, Korea, in 1982 and 1984, respectively. He then received his Ph.D. degree from University of Kyung Buk National University, Korea, in 1988. Dr. Doh is currently a Professor at the School of Electronics Engineering at Cheju National University, Korea. His research interests include micro-machining, Digital signal processing. Dong-Soo Kim received his M.S. and Ph.D. degrees in Mechanical Engineering from Yung Nam University, Korea, in 1991 and 2001, respectively. Dr. Kim is currently the general manager at Nano Mechanical System Research Division at Korea Institute of Machinery & Materials. His research interests include printed Electronics, R2R printing, RP system.     

Approximate velocity scale for primary and secondary dual-inlet side-dump flows

Effects of the bulk inlet velocity on the characteristics of dual-inlet side-dump flows are numerically investigated. Non-reacting subsonic turbulent flow is solved by a preconditioned Reynolds-averaged Navier-Stokes equation system with low-Reynolds number k − ɛ turbulence model. The numerical method is properly validated with measured velocity distributions in the head dome and the combustor. With substantial increase in the bulk inlet velocity, general profiles of essential primary and secondary flows normalized by the bulk inlet velocity are quantitatively invariant to the changes in the bulk inlet velocity. This paper was recommended for publication in revised form by Associate Editor Do Hyung Lee Seung-chai Jung received his B.S. degree in Mechanical Engineering from Yonsei University, Korea, in 2001. He then received his M.S. degree in Mechanical Engineering from Yonsei University, Korea, in 2005. Mr. Jung is currently a Ph. D. candidate at Yonsei University, where he is majoring in Mechanical Engineering. Mr. Jung’s research interests include propulsion system and particle-surface collision dynamics. Byung-Hoon Park received his B.S. degree in Mechanical Design and Production Engineering from Yonsei University in 2003. He is currently a Ph.D. candidate in Yonsei University in Seoul, Korea. His research interests include performance design of propulsion systems and nu-merical analysis of instability in multiphase turbulent reacting flow-fields. Hyun Ko received his B.S. degree in Aerospace Engineering from Chonbuk National University, Korea, in 1996. He then received his M.S. degree in Mechanical Design from Chonbuk National University, Korea, in 1998. In 2005, he obtained his Ph.D. degree from Yonsei University, where he majored in mechanical engineering. Dr. Ko is currently a Principal Research Engineer of the MicroFriend Co., Ltd. in Seoul, Korea. His research interests include propulsion related systems and computational fluid dynamics. Woong-sup Yoon received his B.S. degree in Mechanical Engineering from Yonsei University, Korea, in 1985. He then received his M.S. degree from University of Missouri-Rolla in 1989. In 1992, he obtained his Ph.D. degree from the University of Alabama in Huntsville, where he majored in mechanical and aerospace engineering. Dr. Yoon is currently a professor at the School of Mechanical Engineering at Yonsei University in Seoul, Korea. His research interests include propulsion system and particle-related environmental/ thermal engineering.     

The influence on the contact condition and initial fixation stability of the main design parameters of a self-expansion type anterior cruciate ligament fixation device

This paper proposes a self-expansion type anterior cruciate ligament fixation device. The proposed fixation device provides graft fixation force by maintaining contact with the bone tunnel. Since the device maintains contact with the bone tunnel by the force that expands by the self-driven elastic force of the device, the main design parameters that determine the performance of this device are the ring thickness and expansion angle. This paper develops the three-dimensional finite element models of the fixation device and bone. By simulation with the developed finite element model, this paper studies the influence of the main design parameters of the device on the maximum stress around the ring when grasping the fixation device. Through the analysis of the stress on the bone tunnel wall when the fixation device comes in contact with the bone tunnel, this paper shows the influence of the main design parameters of the fixation device on the contact condition. In addition, through the analysis of the migration that occur upon application of the pull-out force, this paper studies the influence of the main design parameters on the initial fixation stability of the fixation device. This paper was recommended for publication in revised form by Associate Editor Young Eun Kim Jong-Dae KIM received the B.S. and M.S. degrees in Precision Mechanical Engineering from Chonbuk National University, Korea in 1993 and 1995, respectively. He then received his Ph.D. degree in Bionano System Engineering from Chonbuk National University, Korea in 2008. He worked at DAEWOO Electronic Components Co., Ltd., Korea for eight years from 1995. He is currently a full-time lecturer at the Department of Mechanical and Automotive Engineering in Jeonju University, Korea. Dr. Kim’s research interests are in the area of biomechanics and robotics for rehabilitation. Chae-Youn OH received the B.S. degree in Mechanical Engineering from Chonbuk National University, Korea, in 1982. He then received his M.S. and Ph.D. degrees in Mechanical Engineering from Iowa State University, U.S.A., in 1987 and 1990, respectively. He is currently a Professor at the Division of Mechanical System Engineering at Chonbuk National University in Jeonju, Korea. Dr. OH’s research interests are in the area of biomechanics and haptics. Cheol-Sang KIM received his B.S. and M.S. degrees in Mechanical Engineering from Chonbuk National University in Korea in 1980 and 1982, respectively. He then received a Ph.D. degree in Material Science at Universite de Louis Pasteur in Strasbourg, France in 1988. He spent two years at the Department of Bioengineering at University of Pennsylvania (U.S.A) as a Post Doc. fellow. Dr. Kim is currently an Associate Professor at the Division of Mechanical Engineering at Chonbuk National University in Korea. Dr. Kim’s research interests are in the area of biomaterials for hard tissue replacements, design and analysis of implants and artificial organs, and anti-biofouling technology.     

Micro machining of an STS 304 bar by magnetic abrasive finishing

A magnetic abrasive finishing process is a method of non-traditional precision machining in which the finishing process is completed using magnetic force and magnetic abrasives. In this research, a STS 304 cylindrical workpiece was finished using a magnetic abrasive finishing process at 30,000 rpm, and the roughness, roundness, and changes in the micro-diameter were investigated. The study showed that it is possible to control the micro-diameter and weight of the STS 304 cylindrical workpiece by using a near linear approach. Surface roughness as fine as 0.06 μm (Ry) and roundness as fine as 0.12 μm (LZS) were achievable by using a diamond paste with 1 μm particles. Vibrational motion applied to the workpiece improved the surface roughness. The improvement of the surface roughness was achieved because the vibrational motion effectively removes unevenness in the rotational direction and the direction orthogonal to it. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007.recommended for publication in revised form by Associate Editor Dae-Eun Kim Ik-Tae Im received the B.S., M.S. and Ph.D. degrees in Mechanical Engineering from Hanyang University, Seoul, Korea, in 1993, 1995 and 1999, respectively. He has been a visiting scientist at the Department of Materials Engineering, the University of Tokyo, Japan, where he studied on the film growth during the MOCVD process. His research interests include the numerical modeling on the transport phenomena in various materials processing. He is a professor at the Division of Mechanical Design Engineering at Chonbuk National University in Jeonju, Korea. Sang Don Mun received the B.S. degree and M.S. in Precision Mechanical Engineering from Chonbuk National University, Korea, in 1991 and 1993, respectively. He then received the Ph.D. in Precision Mechanical Engineering at the same university in 1997. Dr. Mun is currently a Professor at the Division of Mechanical Design Engineering at Chonbuk National University in Jeonju, Korea. His research interests include magnetic abrasive finishing, tool wear, and micro machining. Seong Mo Oh received his B.S. degree in Mechanical Engineering from Wonkwang University, Korea, in 1992. He then received his M.S. and Ph.D. degrees from Wonkwang in 1994 and 2000 respectively. Dr. Oh is currently a Lecturer at the Division of Mechanical and Automotive Engineering at Wonkwang University in Jeonbuk, Korea. Dr. Oh’s research interests include tribology, functional surfaces, and micromachining.     

Transfer alignment considering measurement time delay and ship body flexure

This paper deals with the transfer alignment problem of strap-down inertial navigation systems (SDINS), using electro-magnetic (EM) log velocity information and gyrocompass attitude information of the ship. Major error sources for velocity and attitude matching are lever-arm effect, measurement time-delay, and ship-body flexure (flexibility). To reduce these alignment errors, an error compensation method based on delay state augmentation and DCM (direction cosine matrix) partial matching is devised. A linearized error model for a velocity and attitude matching transfer alignment system is devised by first linearizing the nonlinear measurement equation with respect to its time delay, and augmenting the delay state into conventional linear state equations. DCM partial matching is then properly combined with velocity matching to reduce the effects of a ship’s Y-axis flexure. The simulation results show that this method decreases azimuth alignment errors considerably. This paper was recommended for publication in revised form by Associate Editor Kyongsu Yi Joon Lyou received a B.S. degree in Electronics Engineering from Seoul National University in 1978. He then went on to receive M.S. and Ph.D. degrees from KAIST in 1980 and 1984, respectively. Dr. Lyou is currently a professor of the Department of Electronics Engineering at Chungnam National University in Daejeon, Korea. His research interests include industrial control and sensor signal processing, IT based robotics, and navigation systems. You-Chol Lim received a B.S. degree in Electronics Engineering from Chungnam National University in 1998. He then received his M.S. and Ph.D. degrees from Chungnam National University in 2000 and 2003, respectively. Dr. Lim is currently a senior researcher at Electronics Department KSLV Technology Division at KARI in Daejeon, Korea. Dr. Lim’s research interests are in the area of remote control, digital filter, and navigation systems.     

Dual stage and an image processing-based method for sight stabilization

This paper presents a combined dual stage-based mechanical and image-based stabilization scheme for a three-axis image-tracking sight system. To improve the stabilization and tracking accuracy, a secondary stage actuated by a pair of electro-magnets is mounted on a conventional elevation gimbal. For the remaining roll axis stabilization, an electronic digital- image stabilization technique is introduced to estimate and correct roll motions. Experimental results are given to demonstrate the effectiveness of the proposed stabilization system and the image-stabilization scheme. This paper was recommended for publication in revised form by Associate Editor Dong Hwan Kim Joon Lyou received a B.S. degree in Electronics Engineering from Seoul National University in 1978. He then went on to receive M.S. and Ph.D. degrees from KAIST in 1980 and 1984, respectively. Dr. Lyou is currently a professor of the Department of Electronics Engineering at Chungnam National University in Daejeon, Korea. His research interests include industrial control and sensor signal processing, IT based robotics, and navigation systems. MinSig Kang received a B.S. degree from the Department of Mechanical Engineering of Seoul National University in 1980. He then went on to receive M.S. and Ph.D. degrees from KAIST in 1983 and 1987, respectively. He worked for the Agency for Defence Development during 1987–1998. Dr. Kang is currently a professor of the Department of Mechanical and Automotive Engineering at Kyungwon University in Sungnam, Korea. His research interests include dynamic systems measurement and control, industrial robotics, and manufacturing systems. HwyKuen Kwak received a B.S. degree in Electronics Engineering from Chungnam National University in 2005. He is currently working on his M.S. and Ph.D. course at Chungnam National University in Daejeon, Korea. His research areas are image signal processing, sensors and digital control systems. YoungJun Choi received a B.S. and M.S. degree in Mechanical Engineering from Kyungwon University in 2004 and 2006. He is currently a researcher for the Agency for Defence Development in Daejeon, Korea. His research fields are dynamic systems measurement and control, satellite systems, navigation systems and smart materials.     

Optimal operating points of PEM fuel cell model with RSM

The output power efficiency of the fuel cell system mainly depends on the required current, stack temperature, air excess ratio, hydrogen excess ratio, and inlet air humidity. Therefore, the operating conditions should be optimized to get maximum output power efficiency. In this paper, a dynamic model for the fuel cell stack was developed, which is comprised of a mass flow model, a gas diffusion layer model, a membrane hydration, and a stack voltage model. Experiments have been performed to calibrate the dynamic Polymer Electrolyte Membrane Fuel Cell (PEMFC) stack model. To achieve the maximum output power and the minimum use of hydrogen in a certain power condition, optimization was carried out using Response Surface Methodology (RSM) based on the proposed PEMFC stack model. Using the developed method, optimal operating conditions can be effectively selected in order to obtain minimum hydrogen consumption. This paper was recommended for publication in revised form by Associate Editor Tong Seop Kim Dong-Ji Xuan received his B.S. degree in Mechanical Engineering from Harbin Engineering University, China in 2000. He then received his M.S. degree in Mechanical Engineering from Chonnam National University, South Korea in 2006. Currently, he is a Ph.D. candidate of the Department of Mechanical Engineering, Chonnam National University, South Korea. His research interests include control and optimization of PEM fuel cell system, dynamics and control, and mechatronics. Zhen-Zhe Li received his B.S. degree in Mechanical Engineering from Yanbian University, China in 2002. He then received his M.S. degree in Aerospace Engineering from Konkuk University, South Korea in 2005 and his Ph.D. degree in Mechanical Engineering from Chonnam National University, South Korea in 2009. Dr. Li is currently a Researcher of the Department of Mechanical Engineering in Chonnam National University, South Korea. Dr. Li’s research interests include applied heat transfer, fluid mechanics, and optimal design of thermal and fluid systems. Jin-Wan Kim received his B.S. degree in Aerospace Engineering from Chosun University, South Korea in 1990. He then received his M.S. degree in Aerospace and Mechanical Engineering from Korea Aerospace University, South Korea in 2003 and his Ph.D degree in Mechanical Engineering from Chonnam National University, South Korea in 2008. He is currently a Post Doctor of the Department of Mechanical Engineering in Chonnam National University, South Korea. His research interests include control of hydraulic systems, dynamics and control, and mechatronics. Young-Bae Kim received his B.S. degree in Mechanical Design from Seoul National University, South Korea in 1980. He then received his M.S. degree in Mechanical Engineering from the Korean Advanced Institute of Science and Technology (KAIST), South Korea in 1982 and his Ph.D. degree in Mechanical Engineering from Texas A&M University, USA in 1990. Dr. Kim is currently a Professor of the School of Mechanical and Systems Engineering in Chonnam National University, South Korea. Dr. Kim’s research interests include mechatronics, dynamics and control, and fuel cell hybrid electric vehicle (FCHEV) systems.     

An enhanced real-time dynamic imbalance correction for precision rotors

Even a moderate mass imbalance of a high-precision rotor produces a significant level of vibration when it spins at high revolutionary speed such as 10,000 rpm or faster. As a result, many attempts have been made for the development of dynamic rotor balancing methods mostly by the precision mechanical system industry; however, intensive studies about the fundamental principles from a theoretical point of view should be carried out further. In the present paper, a new dual axes dynamic imbalance correction method is introduced and tested through simulations. The proposed method is more efficient and effective than its predecessors. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Jung Kwan Lee is currently a masteral student in the School of Mechanical Engineering at Sungkyunkwan University Korea. He received his B.S. degree from Sungkyunkwan University. His primary research interests are rotor design, analysis, and rotor dynamics. Hyungpil Moon received his Ph.D. degree in mechanical engineering from the University of Michigan in 2005. He was a postdoctoral fellow at Carnegie Mellon University. He joined the faculty of the School of Mechanical Engineering at Sungkyunkwan University in 2008. Dongho Oh received his Ph.D. degree from KAIST in 1996. He worked as a Principal En-gineer of Samsung Electronics and SAIT. Dr. Oh is currently an Associate Professor at the Department of Mechanical Engineering at Chungnam National University. Ja Choon Koo is an associate professor of the School of Mechanical Engineering at Sungkyunkwan University Korea. He was an engineer at IBM Corporation, San Jose, California. He received his Ph.D from the University of Texas at Austin. His primary research interests are analysis, and control of dynamic systems, mechatronics, sensors, and actuators.     

A novel optimal assembly algorithm for haptic interface applications of a virtual maintenance system

A virtual maintenance system in a virtual environment can be used to simulate a real-world maintenance system. The efficiency of the simulation depends mainly on the assembly/disassembly task sequence. During simulation, path planning of mechanical parts becomes an important factor since it affects the overall efficiency of the maintenance system in terms of saving energy and time. Therefore, planners must consider the path-planning factors under constraints such as obstacles and the initial/final positions of the parts, as well as the assembly sequence such as number of gripper exchanges and direction changes. We propose a novel optimal assembly algorithm that considers the assembly sequence of mechanical parts and the path-planning factors for a virtual maintenance simulation system. The genetic algorithm is used to determine the optimal sequence of parts to minimize the numbers of gripper exchanges and direction changes, as well as find a repulsive force radius by using the potential field method to generate the shortest optimal distance for transferring each part during the assembly operation. By applying the proposed algorithm to a virtual maintenance system, users can be haptically guided to the optimized assembly solution during mechanical parts assembly operations. This paper was recommended for publication in revised form by Associate Editor Jong Hyeon Park Christiand received a B.Eng. degree in Mechanical Engineering from University of Indonesia in 2006. He then went on to receive his M.Eng. from Gyeongsang National University in 2008. He is currently a member of engineering staff at Electronics and Telecommunication Research Institute (ETRI) in Daejeon, Korea. Jungwon Yoon received the B.S. degree in precision mechanical engineering in 1998 from the Chonbuk National Univ., Korea, and the M. S. degree in the Department of Mechatronics in 2000 from Gwangju Institute of Science and Technology (GIST), Kwangju, Korea, where he received the Ph.D. in 2005. He had worked as a senior researcher in Electronics Telecommunication Research Institute (ETRI), Daejeon, Korea, and a visiting researcher at Virtual Reality Lab, the Rutgers University, U.S.A, from 2001 to 2002. In 2005, he joined the School of Mechanical & Aerospace Engineering, Gyeongsang National University, Jinju, Korea, where he is currently an assistant professor. His research interests include virtual reality haptic devices & locomotion interfaces, and rehabilitation robots.     

Numerical analysis of flow characteristics of fire extinguishing agents in aircraft fire extinguishing systems

If fire breaks out on an airplane, a large amount of fire extinguishing agents should be discharged within a very short time. For effective fire extinguishing, increased discharge velocity of the fire extinguishing agents is required. This can be achieved by using a large-sized vessel in which the fire extinguishing agents are highly pressurized by noncombustible gases. It is important to understand the flow characteristics of a fire extinguishing system for optimal system design. This study reports a numerical analysis of the flow characteristics of an airplane fire extinguishing system using halon-1301 as a fire extinguishing agent. The unsteady flow model was simulated with the general-purpose software package “FLUENT”, to study the flow characteristics of the fire extinguishing agents in the system. The effects of the rupture surface area and tube diameter on the flow characteristics were investigated for optimal system design. From the analysis results, it was clarified that the characteristics of the halon discharge from the end of tube are very sensitive to the rupture surface area and significantly affected by the tube diameter. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Byung-Joon Baek received his B.S. degree in Mechanical Engineering from Seoul National University, KOREA, in 1979. He then received his M.S. and Ph.D. degrees from Seoul National University, KOREA, in 1981 and University of Missouri-Rolla USA, in 1989, respectively. Dr. Baek is currently a Professor at Division of Mechanical System Engineering at Chonbuk National University in Jeonju, Korea. Dr. Baek’s research interests include the thermal control of micro-fluidics. Jee-Keun Lee received his B.S. degree in Precision Mechanical Engineering from Chonbuk National University, KOREA, in 1986. He then received his M.S. and Ph.D. degrees from Chonbuk National University, KOREA, in 1992 and in 1998, respectively. Dr. Lee is currently an associate Professor at Division of Mechanical System Engineering at Chonbuk National University in Jeonju, Korea. Dr. Lee’s research interests include the measurement of a turbulent flow and sprays using the laser diagnostics.     

Experiments of optimal delay extraction algorithm using adaptive time-delay filter for improved vibration suppression

In the previously introduced direct adaptive command shaping filter (ACSF), the time-delay value is fixed and only the magnitudes of the impulses are learned. The performance of the direct adaptive time-delay command shaping filter, however, depends on the select time-delay. In this paper, the authors introduce a new scheme to extract the optimal time-delay value for the improved vibration suppression in flexible motion system. To develop the optimal time-delay extraction scheme, the authors have analyzed the effect of the time-delay value on the performance of the direct ACSF. Based on the analysis result the authors have established a set of equations to extract the optimal time-delay toward the optimal vibration suppression performance of ACSF. Experimental results using a gantry robot with a single flexible link show the effectiveness of the proposed time-delay adaptation approach for the improved vibration suppression. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Joo Han Park received the B.S. and M.S. degrees in Mechanical Engineering from the Kyung Hee University, Korea, in 2005 and 2007. He is currently a candidate for the PhD at Kyung Hee University, Korea. His research interests include robotics and vibration control. Sungsoo Rhim received his B.S. and M.S. degrees in Mechanical Engineering from Seoul National Univ., Korea, in 1990 and 1992 respectively. He then received his Ph.D. degree from Georgia Institute of Technology in 2000. He worked for CAMotion, Inc. in GA, USA, as Research Director from 2000 until 2003 and he is currently an Assistant Professor at the Dept. of Mechanical Engineering in Kyung Hee Univ., Korea. His research interests include system dynamics, control, robotics and vibration.     

Analysis and design study of LCD transfer robot using dynamic simulation and experiment

Recently, the size of raw glass has been greatly increased in the new generation Liquid Crystal Display (LCD) technology. To handle bigger and heavier glasses, it is necessary to develop a large scale LTR (LCD Transfer Robot) to support various complicated LCD fabrication processes. This adjustment will result in difficult design problems such as vibration, handling accuracy deterioration, and high stress due to heavier dynamic loads. In turn, these will result in inaccurate transfer motion and fatigue cracks. In this paper, the dynamic simulation technique is introduced to validate a baseline design and to propose new and improved designs for the best performance of heavy-scaled LCD transfer robots. The dynamic models and analysis results were verified by real experiments including strain measure test and motor power test. Using the verified simulation model, some dynamic situations such as the robot’s emergency stop and free fall situation, which were not impossible to test using the real proto robot, were analyzed and predicted using the simulation model. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Jong-Hwi Seo received a B.S. M.S. and Ph.D. degrees from Ajou University in 1998, 2000 and 2005, respectively. He is currently a senior engineer in Mechatronics and Manufacturing Technology Center of Samsung Electronics Co. His research interests are in the area of multibody dynamics, robotics and mechanism design. Jae Chul Hwang received a B.S., M.S., and Ph.D. degrees in mechanical engineering from Seoul National University, Korea, in 1996, 1998, and 2002, respectively. He is currently a senior engineer in Mechatronics and Manufacturing Technology Center of Samsung Electronics Co., Ltd. His research interests are in the area of kinematics and dynamics of serial and parallel kinematic robot. Yong-Won Choi received a M.S degree in Mechanical Engineering from Korea University in 1993. He has worked for Samsung Electronics, Ltd from 1993 and is currently a principle engineer at Robot Mechanism Part in Mechatronics and Manufacturing Technology Center of Samsung Electronics Co. He is interest in the area of robotics, control and mechanism design. Hong Jae Yim received B.S. and M.S degrees in mechanical engineering from Seoul National University, Korea, in 1979, and 1983, respectively. He received Ph.D degree from Univ. of Iowa, USA. He is currently a professor in School of Mechanical & Automotive Engineering, Kookmin University. His research interests are in the area of computer aided kinematics and dynamics of mechanical systems.     

Prediction of fatigue life distribution of marine propeller materials

Engineering materials have been studied and developed for a remarkably long time, but there are few reports about marine propeller materials. Recently, some researchers have studied the material strength of marine propellers. However, studies on parametric sensitivity and probabilistic distribution of fatigue life of propeller materials have not yet been carried out. In this study, we have evaluated strength characteristics of AlBC3 and HBsC1, both of which have been used for marine propellers using air jet chisel. Then a method to predict the probabilistic distributions of fatigue life of propeller materials is presented and the influence of several parameters on the life distribution is discussed. This paper was recommended for publication in revised form by Associate Editor Jooho Choi Han-Yong Yoon received his B.S. degree in Mechanical Engineering from DanKook University in Seoul, Korea, in 1981. He then received his M.S. and Ph.D. degrees from The University of Tokyo in Tokyo, Japan in 1985 and 1988, respectively. Dr. Yoon is currently a Professor at the Department of Mechanical Engineering at Mokpo National University in Jeonnam, Korea. And, he serves concurrently as the director of Library at his University. His research interests include reliability, fatigue, and fracture mechanics. Jianwei Zhang received his B.E. degree from the School of Electro-Mechanical Automobile Engineering from Yantai University, China, in 2005. He then received his M.E. from the Department of Mechanical Engineering Graduate School of Mokpo National University, Korea, in 2008. Mr. Zhang is currently studying for his doctorate at the Department of Mechanical Engineering, Graduate School of Mokpo National University, Jeonnam, Korea. His research interests include metal fatigue, weld residual stress, and composite materials fatigue.     

A numerical study on oil retention and migration characteristics in the heat pump system

In HVAC system, the oil circulation is inevitable because the compressor requires the oil for lubrication and sealing. A small portion of the oil circulates with the refrigerant flow through the system components while most of the oil stays or goes back to the compressor. Because oil retention in refrigeration systems can affect system performance and compressor reliability, proper oil management is necessary in order to improve the compressor reliability and increase the overall efficiency of the system. This paper describes a numerical analysis of oil distribution in each component of the commercial air conditioning system including the suction line, discharge line and heat exchanger. In this study, system modeling was conducted for a compressor, discharge line, condenser, expansion valve, evaporator and suction line. Oil separation characteristics of the compressor were taken from the information provided by manufacturer. The working fluid in the system was a mixture of a R-410A refrigerant and PVE oil. When the oil mass fraction (OMF) was assumed, oil mass distribution in each component was obtained under various conditions. The total oil hold-up was also investigated, and the suction line contained the largest oil hold-up per unit length of all components. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Min Soo Kim received his B.S., M.S., and Ph.D. degree at Seoul National University, Korea in 1985, 1987, and 1991, respectively. After Ph.D. degree, Prof. Kim worked at National Institute of Standards and Technology (NIST) in U.S.A. for about three years. He is currently a professor at the School of Mechanical and Aerospace Engineering of Seoul National University, Korea. Jong Won Choi received B.S. degree in Mechanical Engineering from Korea University in Seoul, Korea, in 2004, and then received M.S. degrees from Seoul National University in 2006. He is currently a student in Ph.D. course at the School of Mechanical and Aerospace Engineering of Seoul National University in Seoul, Korea. His research interests include refrigeration system, micro-fluidic devices, and PEM fuel cell as an alternative energy for next generation. Mo Se Kim received B.S. degree in Mechanical and Aerospace Engineering from Seoul National University in Seoul, Korea, in 2007. He is currently a student in M.S. course at the School of Mechanical and Aerospace Engineering of Seoul National University in Seoul, Korea. He had studied on the oil migration in the heat pump system, and now he studies on the refrigeration system using an ejector. Baik-Young Chung received his B.S., M.S., and Ph.D. degrees in Mechanical Engineering from Inha University, Korea in 1984, 1986, and 2001, respectively. He is currently a research fellow of HAC Research Center at LG Electronics. He is responsible for the commercial air conditioner group. Sai-Kee Oh received B.S. degree in Mechanical Engineering from Seoul National University, Korea in 1989, and then received M.S. and Ph.D. degrees from KAIST, Korea in 1991 and 1997, respectively. He is currently a principal research engineer of HAC Research Center at LG Electronics. He is responsible for the residential air conditioner group. Jeong-Seob Shin received B.S. degree in Machine Design and Production Engineering from Hanyang University, Korea in 1988, M.S. degree in Mechanical Engineering from KAIST, Korea in 1991, and Ph.D. degree in Mechanical Engineering from POSTECH, Korea in 2004. He has joined HAC Research Center at LG Electronics since 2006 as a principal research engineer.     

A study on cooling efficiency using 1-d analysis code suitable for cooling system of thermoforming

Thermoforming is one of the most versatile and economical processes available for polymer products, but cycle time and production cost must be continuously reduced in order to improve the competitive power of products. In this study, water spray cooling was simulated to apply to a cooling system instead of compressed air cooling in order to shorten the cycle time and reduce the cost of compressed air used in the cooling process. At first, cooling time using compressed air was predicted in order to check the state of mass production. In the following step, the ratio of removed energy by air cooling or water spray cooling among the total removed energy was found by using 1-D analysis code of the cooling system under the condition of checking the possibility of conversion from 2-D to 1-D problem. The analysis results using water spray cooling show that cycle time can be reduced because of high cooling efficiency of water spray, and cost of production caused by using compressed air can be reduced by decreasing the amount of the used compressed air. The 1-D analysis code can be widely used in the design of a thermoforming cooling system, and parameters of the thermoforming process can be modified based on the recommended data suitable for a cooling system of thermoforming. This paper was recommended for publication in revised form by Associate Editor Dongsik Kim Zhen-Zhe Li received his B.S. degree in Mechanical Engineering from Yanbian University, China, in 2002. He then received his M.S. degree in Aerospace Engineering from Konkuk University, South Korea, in 2005. He then received his Ph.D. degree in Mechanical Engineering from Chonnam National University, South Korea, in 2009. Dr. Li is currently a Researcher of the Department of Mechanical Engineering, Chonnam National University, South Korea. Dr. Li’s research interests include applied heat transfer, fluid mechanics and optimal design of thermal and fluid systems. Kwang-Su Heo received his B.S. degree in Mechanical Engineering from Chonnam National University, South Korea, in 1998. He then received his M.S. and Ph.D. degrees in Mechanical Engineering from Chonnam National University, South Korea, in 2003 and 2008, respectively. Dr. Heo is currently a Post-doctorial Researcher of the Department of Mechanical Engineering, KAIST(Korean Advanced Institute of Science and Technology), South Korea. Dr. Heo’s research interests include applied heat transfer, fluid mechanics and thermal analysis of superconductor. Dong-Ji Xuan received his B.S. degree in Mechanical Engineering from Harbin Engineering University, China, in 2000. He then received his M.S. degree in Mechanical Engineering from Chonnam National University, South Korea, in 2006. He is currently a Ph.D. candidate of the Department of Mechanical Engineering, Chonnam National University, South Korea. His research interests include control & optimization of PEM fuel cell system, dynamics & control, mechatronics. Seoung-Yun Seol received his B.S. degree in Mechanical Design from Seoul National University, South Korea, in 1983. He then received his M.S. degree in Mechanical Engineering from KAIST(Korean Advanced Institute of Science and Technology), South Korea, in 1985. He then received his Ph.D. degree in Mechanical Engineering from Texas Tech University, USA, in 1993. Dr. Seol is currently a Professor of the School of Mechanical and Systems Engineering, Chonnam National University, South Korea. Dr. Seol’s research interests include applied heat transfer, fluid mechanics and thermal analysis of superconductor.     

Effect of wave conditions on the performance and internal flow of a direct drive turbine

The purpose of the present study is to investigate the effect of wave conditions on the performance and internal flow of a newly developed direct drive turbine (DDT) model for wave energy conversion experimentally. All the experiments using the test turbine models are conducted in a 2-D wave channel. Monochromatic waves of various conditions of wave height and wave period are applied to the turbine performance test. The influences of turbine configuration on turbine performance are also investigated. Test results show that rotational speed, differential pressure, incident flow rate, maximum output power, and best efficiency of the turbine model vary considerably depending on the wave conditions. Installation of a front guide nozzle and a rear water reservoir to the test turbine improves the turbine performance. Large passage vortex occurs both at the front and rear turbine nozzles in turn through a reciprocating flow in the turbine passage. This paper was recommended for publication in revised form by Associate Editor Jun Sang Park Young-Do Choi received his B.E. and M.E. degrees in Mechanical Engineering from Korea Maritime University, Korea in 1996 and 1998, respectively. He received his Ph.D. in Engineering from the Yokohama National University, Japan in 2003. Dr. Choi is currently a research professor at the School of Mechatronics, Chanwon National University in Changwon, Korea. His research interests include ocean energy, wind power, small hydro power, fluid machinery, PIV and CFD. Chang-Goo Kim received his B.E. and M.E. degrees in Mechanical Engineering from Korea Maritime University, Korea in 2007 and 2009, respectively. Mr. Kim is currently a doctorate student in the Department of Mechanical Engineering, Graduate School, Korea Maritime University. His research interest includes ocean energy. Young-Ho Lee received his B.E. and M.E. degrees from Korea Maritime University, Korea. He received his Ph.D. in Engineering from the University of Tokyo, Japan. Dr. Lee is currently a Professor at the Division of Mechanical and Information Engineering, Korea Maritime University. His research interests include ocean energy, wind energy, small hydro power, fluid machinery, PIV, and CFD.     

Optimal design of a variable stiffness joint in a robot manipulator using the response surface method

The response surface method combined with the design of experiment-based design optimization of a variable stiffness joint (VSJ) is presented in this article. A VSJ used in a manipulator of a robot arm to support 1 kg payload at the end is designed by considering the minimization of the total weight as the objective function. Owing to the requirement of large rotational stiffness of the VSJ, over 10 N · m, ring-type permanent magnets are adopted. First, a model composed of two permanent magnets was initially manufactured and tested for comparison with the analysis results. Then, a three-ring-type permanent magnet-based model is suggested and optimized to increase the torque of VSJ. The finite element method is used as a magnetic field analysis method to substitute for the expensive experimental process. Optimization results decrease the weight from 0.899 kg to 0.538 kg, still satisfying the requirement for the rotational stiffness. This paper was recommended for publication in revised form by Associate Editor Tae Hee Lee Jeonghoon Yoo received his B.S. and M.S. degrees in Mechanical Design and Production Engineering from Seoul National University, in 1989 and 1991, respectively. He then received his Ph.D. degrees from the University of Michigan, Ann Arbor, in 1999. Dr. Yoo is currently a Professor at the School of Mechanical Engineering at Yonsei University in Seoul, Korea. Dr. Yoo’s research interests include analysis and design of electromagnetic field systems. Myung Wook Hyun received his B.S. and M.S. degrees in Mechanical Engineering from Yonsei University, Korea, in 1995 and 1997, respectively. While studying for his M.S. degree, Mr. Hyun also studied variable stiffness unit design. He is now working at Samsung Electronics, Co. Ltd.. Jun Ho Choi received his B.S. and M.S. degrees in Mechanical Design from Hanyang University, Korea and his Ph.D. degree from the University of Michigan, Ann Arbor. He is currently a senior research scientist in the Korea Institute of Science and Technology. His research interests include nonlinear control, manipulator control, and safe-joint design. Sungchul Kang received his B.S., M.S., and Ph.D. degrees in Mechanical Design and Production Engineering from Seoul National University, Korea, in 1989, 1991, and 1998 respectively. Dr. Kang is currently a Principal Research Scientist in the Center for Cognitive Robotics Research, Korea Institute of Science and Technology, in Seoul, Korea. Dr. Kang’s research interests include mobility and manipulation of field and service robots and haptics. Seung-Jong Kim received his B.S. degree in Mechanical Engineering from Seoul University, Korea, in 1989, and his M.S. and Ph.D. degrees from KAIST in 1991 and 1998, respectively. Dr. Kim is currently a Principal Research Scientist at the Korea Institute of Science and Technology in Seoul, Korea. Dr. Kim’s research interests include the design, control, and dynamic analysis of mechatronic systems.     

Efficiency evaluation of micro factory for micro pump manufacture

The micro factory, a miniature manufacturing system, is a means of achieving higher throughput with minimal space, and minimal consumption of energy and resources by downsizing of production processes. Even though, a micro factory is able to perform whole manufacturing processes like the macro factory, the possibility of improving its manufacturing efficiency has not been considered enough. In this paper, an efficiency index is proposed to calculate the efficiency of the micro factory to manufacture a micro pump. The efficiency index has been proposed based on efficiency definition with input and output parameters of the system. Input parameters include cost of system, processing time and energy. Output parameters represent number of product manufactured from the microfactory. Cost of the system has been categorized by micro assembly machine cost, cost of resources, manipulators’ cost, manufacturing space value, and human operators. Processing time has been categorized by assembly time and material handling time. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Murali Subramaniyam received his B.E. and M.Tech. from India in 2003 and 2005, respectively. Currently, he is pursuing his Ph.D. in Me-chanical Design Engineering under Brain Korea 21 program fellowship at CNU (Chungnam National University), Korea. Also he is working as a research associate in LID (Laboratory of Intelligent Design and manufacturing) at CNU, under Professor Sangho Park. His research interests include CAD/CAM (Computer Aided Design/ Computer Aided Manufac-turing), Computer Integrated Manufacturing, Rapid Prototyping and DHM (Digital Human Modeling). Sangho Park is currently a Professor in Mechanical Design Engineering at CNU. He received his B.S., M.S. and Ph.D. from Seoul National University, Korea in 1988, 1990 and 1995 respectively. He was a Senior Research Scientist at ETRI (Electronics and Telecommunications Research Institute), Korea. His areas of expertise and research interest includes CAD/CAM, Virtual Reality, DHM and Micro Assembly. LID (renamed from CAD/CAM) is doing research under his advice. Sung-il Choi received a B.S. form Konyang University in 1995, Korea. He then received an M.S. from CNU in 1997. Currently, he is pursuing his Ph.D. in Mechanical Design Engineering at CNU. He was a researcher at ETRI. His research intersts include the areas of development of CAD interface, virtual simulation, 3D Web solutions, geometric modelling, micro-assembly, and application of distributed environment. Jun-Yeob Song is a Team Leader in the IT Machinery Research Team, Korea Institute of Machinery and Materials, Korea. Also, He is a Chief of National Research Laboratory on Knowledge Evolution based Manufacturing Devices. He received a Ph. D. from the School of Industrial Engineering at Busan National University in 2001. He has extensive experience in design & control of automation and autonomous manufacturing systems, and reliability engineering. In recent years, Dr. Song’s research interests are in the area of micro assembly, bonding, and multi chip packaging (MCP). Jong-Kweon Park received a B.S. degree in Mechanical Engineering from Inha University in 1977. He then received M.S. and Ph.D. degrees in mechanical engineering from Changwon National University in 1993 and 1997. Dr. Park is currently a principal research at Korea Institute of Machinery and Materials in Daejeon, Korea. His current research areas are cutting dynamics and control, structural dynamics and optimization, ultra precision machining systems, micro/nano manufacturing systems, and design and evaluation of machine tool systems. He is currently a project leader for the project, “Development of Microfactory System Technologies for Next Generation.”     

Optimization of mixed casting processes considering discrete ingot sizes

Using linear programming (LP), this research devises a simple and comprehensive scheduling methodology for a complicated, yet typical, production situation in real foundries: a combination of expendable-mold casting, permanent-mold casting and automated casting for large-quantity castings. This scheduling technique to determine an optimal casting sequence is successfully applied to the most general case, in which various types of castings with different alloys and masses are simultaneously produced by dissimilar casting processes within a predetermined period. The methodology proves to generate accurate scheduling results that maximize furnace or ingot efficiency. For multivariable and multi-constraint optimization problems per se, it provides an extremely practical solution which is readily implemented in most real-world casting plants. In addition, incorporating ingot adjustment from the reality of discrete ingot size, this LP scheduling can assist the casting industry in strengthening its competence by heightening ingot utilization as well as satisfying due dates. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007.recommended for publication in revised form by Associate Editor Young-Seog Lee Yong Kuk Park received his B.S. degree in Metallurgical Engineering from Seoul National University, Korea, in 1987. He then received his M.S. degree in Industrial and Operations Engineering from University of Michigan, U.S.A., in 1988 and Ph.D. degree in Manufacturing Engineering from Ohio State University, U.S.A., in 1995. Dr. Park is currently an Associate Professor at the School of Mechanical and Automotive Engineering at Catholic University of Daegu, Korea. He worked for Ford Motor Co., U.S.A., and Renault-Samsung Motors, Korea. Dr. Park’s research interests include casting, forging, sheet metal forming, scheduling in production engineering, mechanical design, die failures, and fatigue analysis. Jung-Min Yang received his B.S., M.S., and Ph.D. degrees in Electrical Engineering from Korea Advanced Institute of Science and Technology (KAIST), Korea, in 1993, 1995, and 1999, respectively. From March 1999 to February 2001, he was a Senior Member of the Engineering Staff at Electronics and Telecommunications Research Institute (ETRI), Korea. Since March 2001, he has been with the Department of Electrical Engineering, Catholic University of Daegu, Korea, where he is currently an Associate Professor. His research interests are in control of asynchronous sequential machines, fault-tolerance in real-time systems, and scheduling of casting process.