• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.437-438
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• 2012

• 방송공학회논문지
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• 제8권2호
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• pp.163-171
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• 2003

고정 및 이동수신환경에서 결합 소스/채널 부호화 기법을 MPEG-4(Moving picture Experts Group) 비디오 전송에 적용하여 대역폭 사용 효율을 높이는 방안에 대하여 논하였다. 채널환경은 랜덤잡음환경과 이동수신환경을 고려하였다. 소스부호화기는 MPEG-4 비디오, 채널부호화기는 RCPC(Rate Compatible Punctured Convolution) 그리고 변조방식은 QPSK(Quadrature Phase Shift Keying)를 적용하였다. 이 논문에서는 여러가지 채널상태(Es/No)에 따른 율-왜곡특성에 대해 분석하여 소스비트율과 채널부호율 간에 최적의 상충점(Trade-off point)을 결정하였고, 결합 소스/채널 부호화 기법과 일반적인 고정부호율 전송기법을 비교하여 결합 소스/채널부호화의 효율성을 보였다.

• 한국군사과학기술학회지
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• 제10권3호
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• pp.161-172
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• 2007

This article suggests an inverse kinematics analysis of a two degree of freedom spatial parallel motion simulator and design methodology of the robust PID controller. The parallel motion simulator consists of a fixed base and a moving frame connected by two serial chains, with each serial chain containing one revolute joint and two passive spherical joint. First, an inverse kinematics problems are solved in order to find the joint variable necessary to bring the end effector to track the desired trajectory. Second, an inverse optimal PID controller is proposed to track trajectories in the face of uncertainty. And the $H_{\infty}$ optimality and robust stability of the closed-loop system is acquired through the PID controller. Finally numerical results show the effectiveness of the PID controller that is designed by square/linear tuning laws.

• 한국정밀공학회지
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• 제28권3호
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• pp.265-274
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• 2011

This paper presents current state of the prediction simulator of structural characteristics of machinery equipment accuracy. Developed accuracy prediction simulator proceeds and estimates the structural analysis between the designer and simulator through the internet for convenience of designer. 3D CAD model which is input to the accuracy prediction simulator would simplified by the process of removing the small hole, fillet and chamfer. And the structural surface joints would be presented as the spring elements and damping elements for the structural analysis. The structural analysis of machinery equipment joints, containing rotary motion unit, linear motion unit, mounting device and bolted joint, are presented using Finite Element Method and their experiment. Finally, a general method is presented to tune the static stiffness at a rotation joint considering the whole machinery equipment system by interactive use of Finite Element Method and static load experiment.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.656-665
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• 1993

Two types of baby corn silk detachment systems called fixing and moving baby corn and based on applying frictional force on the silk were developed and evaluated. In the fixing mode the baby corn was fixed on a pin and a hollow frictional cylinder was moved concentrically and vertically along the baby corn towards the branch end. In the moving mode the baby corn was forced vertically towards the tip to pass through the same silk detachment cylinder. Traveling speeds of the detachment cylinder and the baby corn were 44.5 and 166.9 mm/s. In the fixing mode at silk moisture content of 91 % (w.b) silk detachment efficiencies at low and high speeds were 99.1 and 99.2%. The silk detachment efficiencies in the moving mode at low and high speeds were 96.6 and 98.5%. Damaged baby corn at low speed was less than at high speed in both modes. Minimum damage was nil in the fixing mode at low speed and the maximum was 47.5% in the moving mode at high speed. The damaged was due to ovaries r moval at the base near the joint between the baby corn and the branch.

• International Journal of Control, Automation, and Systems
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• 제3권3호
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• pp.453-460
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• 2005

In this paper, a prototype Cartesian Parallel Manipulator (CPM) is demonstrated, in which a moving platform is connected to a fixed frame by three PRRR limbs. Due to the orthogonal arrangement of the three prismatic joints, it behaves like a conventional X-Y-Z Cartesian robot. However, because all the linear actuators are mounted at the fixed frame, the manipulator may be suitable for applications requiring high speed and accuracy. Using a geometric method and the practical assumption that three revolute joint axes in each limb are parallel to one another, a simple forward kinematics for an actual model is derived, which is expressed in terms of a set of linear equations. Based on the error model, two calibration methods using full position and length measurements are developed. It is shown that for a full position measurement, the solution for the calibration can be obtained analytically. However, since a ball-bar is less expensive and sufficiently accurate for calibration, the kinematic calibration experiment on the prototype machine is performed by using a ball-bar. The effectiveness of the kinematic calibration method with a ball-bar is verified through the well­known circular test.

• International Journal of Automotive Technology
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• 제7권7호
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• pp.833-839
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• 2006

In this paper, roll behavior of three planar half car models are compared. The first model is a simple model whose contact point between a wheel and the ground is assumed to be fixed with a revolute joint. The second model is a modified model of the fIrst model, whose wheel tread width can vary. In this model, the instant center of a wheel with respect to the ground, which is crucial to find the roll center, is assumed to be at the contact point of a wheel and the ground. The last model uses the pole of a wheel with respect to the ground for small displacement as the instant center of a wheel with respect to the ground. Loci of the center of gravity point, the fixed and the moving centrodes which are traces of roll center position in the ground and the body frame respectively, wheel contact points, and instant centers of a wheel with respect to the ground are calculated.

• 전자공학회논문지A
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• 제33A권10호
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• pp.168-176
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• 1996

This paper presetns a 2-D DCT architecture adopting accurac y compensator for reducing the hardware complexity and increasing processing speed in VL\ulcornerSI implementation. In the application fields such as moving pictures experts group (MPEG) and joint photographic experts group (JPEG), 2-D DCT processor must be implemented precisely enough to meet the accuracy specifications of the ITU-T H.261. Almost all of 2-D DCT processors have been implemented using many multiplications and accumulations of matrices and vectors. The number of multiplications and accumulations seriously influence on comlexity and speed of 20D DCT processor. In 2-D DCT with fixed-point calculations, the computation bit width must be sufficiently large for the above accuracy specifications. It makes the reduction of hardware complexity hard. This paper proposes the accuracy compensator which compensates the accuracy of the finite word length calculation. 2-D DCT processor with the proposed accuracy compensator shows fairly reduced hardware complexity and improved processing speed.

• 한국초전도ㆍ저온공학회논문지
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• 제9권1호
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• pp.76-81
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• 2007

This paper deals with the characteristics of a small scale $high-T_c$ superconducting(HTSC) levitation system. The levitation tester. which models after electrodynamic suspension(EDS) maglev, consists of one HTSC magnet, a reaction plate, and force measuring components. Instead of moving magnet, AC current was applied to the fixed HTSC magnet. The magnet also has persistent current switch(PCS). The inductance of the magnet was 18.5 mH and total joint resistance of the magnet was $5.74{\times}10^{-7}\Omega$. AC current was applied into the HTSC magnet with various frequencies and the levitation force was calculated and measured. According to the increase of the vehicle speed, the levitation force was saturated.

• 한국산업융합학회 논문집
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• 제22권3호
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• pp.315-324
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• 2019

This paper present a novel 6-axis robotic base platform with force/moment sensing. The robotic base platform is made up of six loadcells connecting the moving plate to the fixed plate by spherical joints at the both ends of loadcells. The statics relation is derived, the robotic base platform prototype and the loadcell measurement system are developed. The force/moment calibrations in joint and Cartesian spaces are performed. The algorithm to detect external force applied at a working robot is derived, and using a 6-DOF robot mounted on the robotic base platform, force/moment measurement experiments have been performed.