• 한국정밀공학회지
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• 제33권12호
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• pp.1007-1013
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• 2016

This paper presents the development of a magneto-optical encoder for higher precision and smaller size. In general, optical encoders can have very high precision based on the position information of the slate, while their sizes tend to be larger due to the presence of complex and large components, such as an optical module. In contrast, magnetic encoders have exactly the opposite characteristics, i.e., small size and low precision. In order to achieve encoder features encompassing the advantages of both optical and magnetic encoders, i.e., high precision and small size, we designed a magneto-optical encoder and developed a method to detect absolute position, by compensating for the error of the hall sensor using the linear table compensation method. The performance of the magneto-optical encoder was evaluated through an experimental testbed.

• 한국정밀공학회지
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• 제30권7호
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• pp.754-761
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• 2013

Thermal displacement is an important issue in machine tool systems. During the last several decades, thermal error compensation technology has significantly reduced thermal distortion error; this success has been attributed to the development of a precise, robust thermal error model. A major advantage of using the thermal error model is instant compensation for the control variables during the modeling process. However, successful application of thermal error modeling requires correct determination of the temperature sensor placement. In this paper, a procedure for predicting thermal-mode-based thermal error is introduced. Based on this thermal analysis, temperature sensors were positioned for multiple heat-source models. The performance of the sensors based on thermal-mode error analysis, was compared with conventional methods through simulation and experiments, for the case of a slide table in a transient state. Our results show that for predicting thermal error the proposed thermal model is more accurate than the conventional model.

• 한국지능시스템학회논문지
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• 제14권3호
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• pp.375-382
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• 2004

신경회로망을 이용한 XY 테이블의 비선형 보상기법을 제안한다. 제안된 신경망 제어기는 시스템의 비선형 성분에 의한 성능저하를 보상하는 신경회로망과 시스템의 안정화를 위한 비례미분(PD) 제어기로 구성된다. 신경망 보상 구조가 적응적이고 추적오차와 파라미터 추정치가 유계가 되는 신경망 파라미터 동조알고리듬과 안정도 증명을 제시한다. 신경망 제어기를 위치 테이블에 실험함으로써 비선형 성분에 의한 성능저하를 줄이는 효과를 보여준다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1828-1831
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• 2003

There are various sources causing a position error in a linear motor. This paper focuses on error sources from rotational motions of a table and friction. Rotational errors occur due to imperfections during manufacturing and/or assembly of guide ways, and cause a position error at locations of interest. Friction is another factor deteriorating the position error due to its highly nonlinear behavior. The position error of the linear motor was about 20∼30$\mu\textrm{m}$. After compensating the position errors due to rotational error motions and friction. the remaining errors become about 6～8$\mu\textrm{m}$ and 2～3$\mu\textrm{m}$, respectively. It is shown that the positional accuracy of a linear can be greatly improved by compensating the two error sources.

• 한국정밀공학회지
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• 제14권8호
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• pp.130-136
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• 1997

For compensating the error motion of hydrostatic guideways, we introduce a way that the clearance of table is actively controlled corresponding to the amount of error with the variable capillary. The structure and the theoretical design method of active controlled capillary using piezo actuator, named ACC, are proposed in this paper. Basic characteristics such as the maximum controllable range, micro step response and available dynamic bandwidth are tested for confirmation of structural suitability of ACC, and these characteristics are also tested on the table mounted with ACC for verifying the availability. The experimental result showed that by the use of ACC, the error motion within 2.7 .mu. m of a hydrostatic guideway can be compensated with the resolution of 2.7nm, 1/100 contollable range, and the frequency bandwidth of 5.5 Hz. From these results, it is confirmed that the ACC is very effective to improve the motion accuracy of high or ultra precision hydrostatic guideways.

• 제어로봇시스템학회논문지
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• 제5권4호
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• pp.462-470
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• 1999

In this paper, we proposed a cross-couple controller for compensating nonlinear friction of the X-Y table of CNC machines. Due to the nonlinearity of the frictions, large contour errors, referred to as quadrant glitches, occur when each axis of the X-Y table makes a zero velocity crossing. To reduce the quadrant glitches the friction compensators and nonlinear friction observers for estimating Coulomb frictions are employed in the proposed method. A hyperbolic tangent function is used in reducing the magnitude of quadrant glitches and the CEM (Contour Error Model) is utilized for the estimation of the velocities. The performance of the proposed compensators is evaluated for several trajectories by computer simulations.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.279-285
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• 1993

This paper presents a precision automatic measuring system for ball screw Pitch. Ball screw is mounted on a precision indexing table, and the ball screw pitch is measured via magnetic scale, where the indexing and measurement are performed by a PC. For precision indexing of ball screw, direct driven motor is coupled to the designed dead and live centers; the performance of the centers are assessed with a precision master sylinder,such as radial motion,tilt motion, and axial motions. An error compensation model is constructed for the measurement system of ball screw pitch, where the error motions of indexing system as well as the scale measurement system are combined to give the measurement error for the ball screw. The developed system proposes an automated precision measurement system for manufacturers and users of ball screw.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.672-676
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• 2004

In this paper, measuring system of 5 DOF motion errors are proposed using two capacitive type sensor, a straight edge and a laser interfoerometer. Yawing error and pitching error are measured using the laser interferometer, and rolling error is measured by the reversal method using a capacitive type sensor. Linear motion errors of horizontal and vertical direction are measured using the sequential two point method. In this case, influence of angular motion errors is compensated using the previously measured angular motion errors. In the horizontal direction, measuring accuracy is within 0.05 $\mu$m and 0.27 arcsec, and in the vertical direction, it is within 0.15 $\mu$m and 0.5 arcsec. From these results, it is confirmed that the proposed measureing system is very effective to the measurement of 5 DOF motion errors in the ultra precision feed tables.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1292-1295
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• 1996

This paper proposes an adaptive control technique for the autopilot design of STT missile. Dynamics of the missile is highly nonlinear and the equilibrium point is vulnerable to change due to fast maneuvering. Therefore nonlinear control techniques are desirable for the autopilot design of the missile. The nonlinear controller requires the exact model to obtain satisfactory performance. Generally a look-up table is used for the dynamic coefficients of a missile, so there must be coefficients error during actual flight, and the performance of the nonlinear controller using these data can be degraded. The proposed adaptive control technique compensates the nonlinear controller with modeling error resulting from the error of aerodynamic data and disturbance. To investigate the usefulness, the proposed method is applied to autopilot design of STT missile through simulations.

• 한국전자파학회논문지
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• 제21권8호
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• pp.857-864
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• 2010

본 논문에서는 LINC(LInear amplification with Nonlinear Component) 시스템의 두 경로 간의 이득 및 위상 오차의 발생에 의한 신호 왜곡을 분석하고, 이를 기반으로 생성한 LUT(Look Up Table)를 활용하여 효율적으로 경로 오차를 제거하는 기법을 제안한다. LINC 시스템은 Outphasing 기법을 활용하기 때문에 경로 오차에 의한 EVM (Error Vector Magnitude) 및 ACPR(Adjacent Channel Power Ratio)의 성능 저하가 커진다. 이득 오차, 위상 오차를 두 개의 변수로 하여 EVM과 ACPR을 구하는 방법을 도출하였다. 도출한 방법을 기반으로 EVM, ACPR에 관한 2차원 LUT를 생성하고, 파일럿 신호 없이 효율적으로 경로 오차를 도출하는 기법을 제안하였다. DSP(Digital Signal Processing) 기반의 경로 보상기를 포함한 LINC 시스템을 구축하고 성능을 검증하였다. 대역폭 1.5 MHz, 4.7 dB의 PAPR(Peak to Average Power Ratio)을 갖는 16QAM 신호에 대하여 보상 전에 경로 간 95 %의 이득 비율과 $19.33^{\circ}$의 위상 지연을 가지고 있는 LINC 시스템에 대하여 제안된 기법을 적용한 경우, 경로 간 이득 비율은 99 % 이상, 위상 지연 값은 $0.5^{\circ}$ 이하로 보정되었으며, ACPR은 18.1 dB 향상됨을 확인하였다.