• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.634-637
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• 1994

This paper presents a CMAC network based controller on the basis of Lyapunov theory. CMAC network is employed to approximate and to compensate the uncertainties induced by inaccurate modelling of the system. For the improvement of robustness under the bounded disturbances and the approximation error of the CMAC, the adaptation scheme with a deadzone and an additional control input are developed.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.332-337
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• 1988

A digital series-feedback compensator algorithm for tracking time-varying signal is presented. The series-feedback compensator is composed of one closed loop pole / zero cancellation compensator and one desired-input generator. This algorithm is applied to nonlinear hydraulic position control system. The hydraulic servo system is modelled as a second order linear model and cancellation compensator is modelled from it. The desired input generator is inserted to reduce modelling error. Digital computer simulation output using this control method is present and the usefulness of this control algorithm for nonlinear hydraulic system is verified.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.5
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• pp.519-526
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• 1990

In this paper we propose the resolved motion controller using a neural network for a robot manipulator. Neural identifier designed by a neural network is trained by using a feedback force as an error signal. The identifier approximates the output of a unknown nonlinear system by monitoring both the input and the output of this system. If the neural network is sufficiently trained well, it does not require either strict modelling of the manipulator or precise parameter estimation. The effectiveness of the proposed controller is demonstrated by computer simulation using a two-link planar robot.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.2
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• pp.42-48
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• 1993

In this paper, dynamic collapse behavior of the rectangular tube under impact loading is anlayzed using nonlinear finite element method of shell element. In case of shell element formulation using corotational element coordinates system, dynamic collapse behavior is analyzed without initial imperfection, and with initial imperfection. This paper reveals that the collapse of a rectangular tue without initial imperfection is caused by an error of transformation of the corotational coordinates system.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.285-291
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• 2011

The error motion of a machine tool spindle directly affects the surface errors of machined parts. The error motions of the spindle are not desired errors in the three linear direction motions and two rotating motions. Those are usually due to the imperfect of bearings, stiffness of spindle, assembly errors, external force or unbalance of rotors. The error motions of the spindle have been needed to be decreased to desired goal of spindle's performance. The level of error motion is needed to be estimated during the design and assembly process of the spindle. In this paper, the estimation method for the five degree of freedom (5 D.O.F) error motions of the spindle is suggested. To estimate the error motions of the spindle, waviness of shaft and bearings, external force model was used as input data. And, the estimation models are considering geometric relationship and force equilibrium of the five degree of the freedom. To calculate error motions of the spindle, not only imperfection of the shaft, bearings, such as rolling element bearing, hydrostatic bearing, and aerostatic bearing, but also driving elements such as worm, pulley, and direct driving motor systems, were considered.

• International Commerce and Information Review
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• v.8 no.2
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• pp.299-312
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• 2006

This study examines the relations among wage differentials, trade, and productivity in Korea, using the methodology of Granger causality and vector error correction modelling. Cointegration test results over the 1975-2004 period indicate that all the test variables are cointegrated. Therefore, wage differentials, trade, and productivity are all related in the long run. We found some evidence on long-run relationship, while there is no short-run relationship between three test variables. First, trade and wage differentials have positively and bi-directionally Granger causality in the long-run. Second, productivity Granger causes negatively wage differentials in the long-run. Finally, productivity Granger causes positively trade in the long-run. These results explain partially the current theoretical predictions for wage inequality as well as supports the productivity-led growth hypothesis in the Korean economy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.391-394
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• 2002

This paper introduces that the lathe optimize for main and sub spindle's synchronous in Opening-CNC. In view of optimal design, the mathematical modelling and the frequency domain analysis of spindle's system are performed. For the compensation of synchronous error in compounded manufacture process, the optimization method of motor drive's control parameter and the related parameter is proposed. By the experiment in prototype machines using the server/client program, the validity of the proposed method is verified.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.123-129
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• 1996

Computed torque method has been used for precise trajectory control of the robotic system that involves nonlinear dynamics. It is hard to know exact values of robot system parameters, and the robot arm receives umpredictable interference from the working environment. These disturbances, especially in a direct drive robot, are directly transmitted to actuating motor without reduction. Modelling error and distrubance can cause significant errors in a trajectory tracking problem. In this paper, we propose a new controller that $H_{\infty}$controller is conbined to robot system linearized by computed torque. Simula- tions are made for comparing the performance of the proposed controller with that of a nonlinear $H_{\infty}$ controller proposed by Chen and also computed torque method.hod.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.323-326
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• 1996

In a simple system, the control schemes work well provided that the characteristic of the plant or the coefficients are known and fixed. But the condition is not met in the system like satellite, for example, varying over time and the coefficients of dynamic system change due to disturbance, etc, and the better precise model is required to control the given dynamic system well. Conversely, the fixed controller make the unmodel dynamic system with a wide class of modelling error be stable within the error tolerance limits. Also, a robust model reference adaptive control scheme is designed for the plant, paying attention to the derivation of the appropriate parametric model and the design of the normalizing signal to guarantee that it has the desired properties.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.1
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• pp.55-62
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• 2004

This paper addresses the method for figuring out the hole diameter on the mask containing the information about machining depth. With this mask e micro machining is carried out with a simple 2D movement of the mask. Based on e suggested method excimer laser ablation processes are modeled and determination of the optimal laser ablation conditions such as hole diameter, step size, mask movement velocity, etc. is completed. The excimer laser ablation simulation for creating 3D micro lens is carried out by employing determined ablation conditions to prove verification of the method. The results from simulation illustrated the average error of 140nm and e relative error of 2％.