• 대한전기학회논문지:전력기술부문A
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• 제48권4호
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• pp.452-460
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• 1999

Sawing experiments using a two-arm system have been performed in this work. The two-arm system under consideration of two kinematically-nonidentical arms. A passive joint is inserted at the end-point of one robot in order to increase the mobility up to the motion degree required for sawing tasks. A hybrid control algorithm for control of the two-arm system is designed. We experimentally show that the performance of the velocity and force response are satisfactory, and that one additional passive joint not only prevents the system from unwanted yaw motion in the sawing task, but also allows an unwanted pitch motion to be notably reduced by an internal load control. To show the general applicability of the proposed algorithms, we perform experimentation under several different conditions for saw, such as three saw blades, two sawing speeds, and two vertical forces.

• 대한전자공학회논문지SP
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• 제44권3호
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• pp.16-22
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• 2007

H.264에서 움직임 예측은 전체 부호화 시간의 큰 비중을 차지함으로써 실시간 적용을 위해서 반드시 개선되어야할 부분이다. 이런 문제점 개선을 위해 제안된 알고리즘들의 대부분은 부호화에서 실시간 적용에 문제되는 시간을 줄이고자 전체 검색의 화질을 목표로 빠른 검색 알고리즘을 제안해 왔으며 부 화소관련 알고리즘도 이와 같다. 본 논문은 이런 알고리즘들의 접근과는 다르게 움직임 영상별 부호화된 움직임 예측을 분석하여 이를 바탕으로 현재 매크로 블록의 정수 화소 움직임 벡터와 이미 부호화된 주변 3개 움직임 벡터를 이용하여 부 화소 탐색 진행 여부를 결정하는 것을 제안한다. 또한 분석된 움직임 벡터의 수평/수직 방향성을 이용, 부 화소에서의 수평/수직 방향만의 탐색을 제안하고 위의 두 제안 사항에 대한 적용 결과를 보여 준다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.490-496
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• 1995

A four-legged mobile robot can move on the plain terrain with mobility and stability, but if there exist any obstacles on the terrain of the motion direction, it takes extra times for a mobile robot to cross those obstacles and the stability should be considered during motion. The main objevtive is the study of a quadruped which can cross obstacles with better mobility, stability and fuel economy than any other wheeled or tracked vehicles. Vertical step, isolated wall and ditch are the basic obstacles and by understanding those three cases perfectly, a quadruped can move on any mixed rough terrain as 4-legged animal moves. Each leg of a determine the crossing capability in a static analysis. A quadruped can be simplified with links and joints. By applying the research method, a quadruped can determine the control procedures as soon as it receives the terrain informations from scanner and finally can be moved as animals move with mobility and stability.

• 한국정밀공학회지
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• 제28권5호
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• pp.599-605
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• 2011

A 3-D rehabilitation robot system is developed. The robot system is for the rehabilitation of upper extremities, especially the shoulder and elbow joints, and has 3-D workspace for occupational therapy to recover physical functions in activities of daily living(ADL). The rehabilitation robot system has 1 DOF in horizontal rotational motion and 2 DOF in vertical rotational motion, where all actuators are set on the ground. Parallelogram linkage mechanisms lower the equivalent inertia of the control elements as well as control forces. Also the mechanisms have high mechanical rigidity for the end effector and the handle. In this paper, a hybrid position/force controller is used for controlling positions and forces simultaneously The controller is tuned according to the robot posture. The active motion modes for rehabilitation program consist of active-resisted motion mode and active-free motion mode. The results of the experiments show that the proposed motion modes provide the intended forces effectively.

• 한국해안해양공학회지
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• 제14권3호
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• pp.183-191
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• 2002

해수교환이 우수하고, 조차에 따라 상·하로 자유롭게 운동하며, 연약지반과 대수심역에도 설치될 수 있다는 것을 일반적인 부방파제의 주요한 특징으로 들 수 있다. 본 연구는 말뚝계류된 부방파제에 의한 3차원파랑제어와 동적인 거동을 경계적분법과 고유함수전개법을 병용하는 수치해석법으로부터 논의한다. 여기서, 말뚝계류시스템은 연직운동만이 허용되고 다른 운동성분들은 모두 구속되며, 체인계류시스템보다도 파랑에너지의 흡수가 많은 것으로 알려져 있다. 본 연구에서는 말뚝계류에 있어서 말뚝과 본체인 폰툰과의 사이에 작용하는 마찰력과 같은 저항력은 고려되지 않는다. 수치해석결과에 따르면 부방파제의 홀수와 폭의 변화는 파랑제어에 큰 영향을 미치고, 입사파의 주기가 길면 부방파제를 통한 전달파가 크다는 것을 알 수 있다. 그리고, 부방파제의 연직운동은 단주기파에서 크게 나타난다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1082-1087
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• 2003

In this paper, we address the development of magnetic levitation positioning system. This planar magnetic levitator employs four permanent magnet liner motors. Each motor generates vertical force for suspension against gravity, as well as horizontal force for drive levitation object called a platen This stage can generate six degrees of freedom motion by the vertical and horizontal force. We derived the mechanical dynamics equation using lagrangian method and used coenergy to express an electromagnetic force. We proposed control algorithm for the position and posture control from its initial value to its desired value using sliding mode control. Some simulation result is provided to verify the effectiveness of the proposed control scheme.

• 제어로봇시스템학회논문지
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• 제17권7호
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• pp.659-667
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• 2011

The study of bipedal robot is towards similar shape and function with human. In this paper, we propose a human-like walking pattern compatible to the flexible foot with toe and heel structure. The new walking pattern for a bipedal robot consists of ZMP, center of mass (CoM), and ankle trajectory and is drawn by considering human kinesiology. First, the ZMP trajectory moves forward without stopping at a point even in the single support phase. The corresponding CoM trajectory to the ZMP one is derived by solving differential equations. As well, a CoM trajectory for the vertical axis is added by following the idea of human motion. The ankle trajectory closely mimics the rotational motion of human ankles during taking off and landing on the ground. The advantages of the proposed walking pattern are demonstrated by showing improved stability, decreased ankle torque, and the longer step length capability. Specifically, it is interesting to know that the vertical CoM motion is able to compensate for the initial transient response.

• 한국정밀공학회지
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• 제25권6호
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• pp.134-142
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• 2008

In this paper, we propose a precise linear motion stage supported by magnetically preloaded air bearings. The eight aerostatic bearings with rectangular carbon porous pads were located only one side of vertical direction under the platen where four bearings are in both sides of horizontal direction as wrap-around-design, and this gives simpler configuration than which constrained by air bearings for all direction. Each of the magnetic actuators has a permanent magnet generating static magnetic flux far required preload and a coil to perturb the magnetic farce resulting adjustment of air- bearing clearance. The characteristics of porous aerostatic bearing are analyzed by numerical analysis, and analytic magnetic circuit model is driven for magnetic actuator to calculate preload and variation of force due to current. A 1-axis linear stage motorized with a coreless linear motor and a linear encoder was designed and built to verify this design concept. The load capacity, stiffness and preload force were examined and compared with analysis. With the active magnetic preloading actuators controlled with DSP board and PWM power amplifiers, the active on-line adjusting tests about the vertical, pitching and rolling motion were performed. It was shown that motion control far three DOF motions were linear and independent after calibration of the control gains.

• 한국정밀공학회지
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• 제32권3호
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• pp.263-268
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• 2015

This paper describes lost motion analysis for a novel 6-DOF ultra-precision positioning stage. In the case of flexure hinge based precision positioning stage, lost motion is generated when the displacement of actuator is not delivered completely to the end-effector because of the elasticity of flexure hinge. Consequently, it is need to compute amount of lost motion to compensate the motion or to decide appropriate control method for precision positioning. Lost motion analysis for the vertical actuation unit is presented. The analysis results are presented in two ways: analytic and numerical analyses. It is found that they closely coincide with each other by 1% error. In finite element analysis result, the amount of lost motion is turned out to be about 3%. Although, the amount is not so large, it is necessary procedure to check the lost motion to establish the control method.

• Journal of Advanced Marine Engineering and Technology
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• 제28권6호
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• pp.906-915
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• 2004

In this paper, we address the development of magnetic levitation positioning system. This planar magnetic levitator employs four permanent magnet liner motors. Each motor generates vertical force for suspension against gravity, as well as horizontal force for driving levitation object called a platen. This stage can generate six degrees of freedom motion by the vertical and horizontal force. We derived the mechanical dynamics equation using Lagrangian method and used coenergy to express an electromagnetic force. We proposed a control algorithm for the position and posture control from its initial value to its desired value using sliding mode control. Some simulation results are provided to verify the effectiveness of the proposed control scheme.