• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.3
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• pp.253-259
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• 2004

This paper presents a speed controller method based on the disturbance torque observer for high-performance speed control of the brushless DC (RLDC) motor. In case of the speed control of robot arms and tracking applications with lower stiffness, we cannot design the speed controller gain to be very large from the viewpoint of the system stability Thus, the feedforward compensation method using disturbance torque observer was proposed. This method can improve the speed characteristic without increasing the speed controller gain. The speed characteristic against disturbance torque can be improved when the bandwidth of the speed controller cannot be made large enough. Consequently, the speed control of the BLDC motor for the high-performance application become achieved.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.601-606
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• 1998

In this paper, we propose a new design method of an optimal fuzzy logic controller using co-evolutionary concept. In general, it is very difficult to find optimal fuzzy rules by experience when the input and/or output variables are going to increase. Futhermore proper fuzzy partitioning is not deterministic ad there is no unique solution. So we propose a co-evolutionary method finding optimal fuzzy rules and proper fuzzy membership functions at the same time. Predator-Prey co-evolution and symbiotic co-evolution algorithms, typical approaching methods to co-evolution, are reviewed, and dynamic fitness landscape associated with co-evolution is explained. Our algorithm is that after constructing two population groups made up of rule base and membership function, by co-evolving these two populations, we find optimal fuzzy logic controller. By applying the propose method to a path planning problem of autonomous mobile robots when moving objects applying the proposed method to a pa h planning problem of autonomous mobile robots when moving objects exist, we show the validity of the proposed method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1841-1852
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• 1992

With the wide application of fiber-reinforced composite material in aircraft, space structures and robot arms, the design and manufacture of composite joints have become a very important research area because they are often the weakest areas in composite structures. In this study, the effects of the adhesive thickness, residual thermal stress on the torque capacity of the tubular single lap joints were studied. The torque capacity of the adhesive joints were experimentally determined and found to be inversely proprotional to the adhesive thickness. In order to match the experimental results to the theoretical analyses, the elastic-perfectly plastic material properties of the adhesive were used in the closed form solution. Also, the residual thermal stress of the joints were calculated by the finite element method and it was proved that the residual thermal stress could play an important role in the thick adhesive joints.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.7-13
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• 2015

The production processes were reviewed through the injection analysis of the shift lever as a core component of an auto lever installed in the automatic transmission of cars. The injection analysis was carried out for the shift lever and rod among the components in a shift lever module. The shift lever and rod are designed for injection molding with the insertion of a tube, a pin cable plate, and a steel rod for securing the strength of the product. The charging time, failure of injection molding, weld line, air trap, and deformation were reviewed according to this insert. Analyses on various gate positions were carried out for reviewing the cultivation and deformation of fiber around major components, such as the generation section of manipulation feeling and assembly section, so that optimal gate conditions might be reviewed and reflected in the mold design. Finally, we plan to compare the analysis results with the production of trial products.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.563-569
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• 2012

In the semiconductor and display device production processes, the handling of sensitive objects needs new carrying technology. Floating carrying motion is a practical alternative solution for non-contact handling of parts and substrates. This paper presents a study of through paths inside the air pressure pick-up head to generate the floating motion. The air motion by conceptual designed paths inside the head gradually develops positive pressure and vacuum between narrow objects. Positive pressure occurs through the head tip before discharging outside of the head. Negative pressure is developed by evacuating the inside head bottom as result of the radial flow connecting the vertical through-holes. The numerical analysis was done to figure out the stable levitation caused by the two acting forces between surfaces. In comparing with the standard case that the levitation gap gets 0.7-0.9 mm, it confirms the suggested head characteristics to show floating capacity in accordance with the head size, number of through-hole, and locations of through-hole in succession of conceptual design for a prototype.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.816-821
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• 2005

The cycloid reducer has very high efficiency, high ratios, high stiffness and small size, in comparison with a conventional gear mechanism, which makes it an attractive candidate for limited space and precision application such as industrial robot. There are several publications on analysis and design of the cycloid reducer, however, it was assumed that the contact stiffness of pin rollers and cycloid disk is constant regardless of their contact geometry. Moreover, the torsional stiffness of the cycloid reducer couldn't be calculated due to the assumption. In this paper, we present a new procedure of calculating torsional stiffness of the cycloid reducer using Hertz contact theory. First, conventional force analysis of the cycloid reducer is briefly reviewed. Then, iterative numerical calculation procedure of the contact stiffness is proposed based on the Hertz contact theory where the contact stiffness depends on the contact force. In addition, total torsional stiffness of the cycloid reducer is estimated considering its rolling element bearing stiffness. The torsional stiffness of the cycloid reducer is dominated by the rolling element bearing stiffness since the contact stiffness of the cycloid disk is too large.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.4
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• pp.279-286
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• 1996

In this paper, variable structure control(VSC) based on reaching law method with fuzzy inference for nonlinear systems is proposed. The reaching law means the reaching condition which forces an initial state of system to reach switching surface in finite time, and specifies the dynamics of a desired switching function. Since the conventional reaching law has fixed coefficients, the chattering can be existed largely in sliding mode. In the design of a proposed fuzzy reaching law, we fuzzify RP(representative point)'s orthogonal distance to switching surface and RP's distance the origin of the 2-dimensional space whose coordinates are the error and the error rate. The coefficients of the reaching law are varied appropriately by the fuzzy inference. Hence the state of system in reaching mode reaches fastly switching surface by the large values of reaching coefficients and the chattering is reduced in sliding mode by the small values of those. And the effectiveness of the proposed fuzzy reaching law method is showen by the simulation results of the control of a two link robot manipulator.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.341-342
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• 2008

GA(Genetic Algorithm)는 NP-Complete 도메인이나 NP-Hard 도메인 내의 문제들에 대해서 최적의 해를 찾기 위해서 많이 사용되어 지는 진화 컴퓨팅 방법 중 하나이다. 모바일 로봇 기술 중 경로계획은 NP-Complete 도메인 영역의 문제 중 하나로 이를 해결하기 위해서 Dijkstra 등의 그래프 이론을 이용한 연구가 많이 연구되었고 최근에는 GA등 진화 컴퓨팅 기법을 이용하여 최적의 경로를 찾는 연구가 많이 수행되고 있다. 그러나 모바일 로봇이 처리해야 될 공간 정보 크기가 증가함에 따라 기존 GA의 개체의 크기가 증가되어 게산 복잡도가 높아져 시간 지연등의 문제가 발생할 수 있다. 이는 모바일 로봇의 잠재적 오류로 발생될 수 있다. 공간 정보에는 동적이 장애물들이 예측 불허하게 나타 날 수 있는데 이것은 전역 경로 계획을 수립할 때 또한 반영되어야 된다. 본 논문에서는 k-means 클러스터링 기법을 이용하여 장애물 밀집도 및 거리 정보를 기반으로 공간정보를 k개의 군집 공간으로 재분류하여 이를 기반으로 N*M개의 그리드 개체 집단을 생성하여 최적 경로계획을 수립하는 GA를 제시한다.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.630-639
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• 2004

The Stewart platform manipulator is a closed-kinematics chain robot manipulator that is capable of providing high structural rigidity and positional accuracy. However, this is a complex and nonlinear system, so the control performance of the system is not so good. In this paper, a new robust motion control algorithm is proposed. The algorithm uses partial state feedback for a class of nonlinear systems with modeling uncertainties and external disturbances. The major contribution is the design of a robust observer for the state and the perturbation of the Stewart platform, which is combined with a variable structure controller (VSC). The combination of controller and observer provides the robust routine called sliding mode control with sliding perturbation observe. (SMCSPO). The optimal gains of SMCSPO, which is determined by nominal eigenvalues, are easily obtained by genetic algorithm. The proposed fitness function that evaluates the gain optimization is to put sliding function. The control performance of the proposed algorithm is evaluated by the simulation and experiment to apply to the Stewart platform. The results showed high accuracy and good performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.18-25
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• 2003

A haptic hand controller (HHC) operated by the user’s hand can receive information on position and orientation of the hand and display force and moment generated in the virtual environment to the hand. In this paper, a 3-DOF hand controller is first presented, in which all the actuators are mounted on the fixed base by combining a 5-bar linkage and a gimbal mechanism. The 6-DOF HHC is then designed by connecting these two 3-DOF devices through a handle which consists of a screw and nut. Analysis using performance index is carried out to determine the dimensions of the device. The HHC control system consists of the high-level controller for kinematic and static analysis and the low-level controller for position sensing and motor control. The HHC used as a user interface to control the mobile robot in the virtual environment is given as a simple application.