• International Journal of Precision Engineering and Manufacturing
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• 제7권2호
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• pp.18-24
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• 2006

This paper proposes a LuGre Model-Based Neural Network (MBNN) friction compensation algorithm for a linear motor stage. For matching the friction phenomena in both the motion-start region and the motion-reverse region, the LuGre dynamic model is employed into the proposed compensation algorithm. After training of the model-based neural network is completed, the estimated friction for compensation is obtained. From the obtained result we find that the new structure gains advantage over the non-friction compensation system on the performance of the compensator in both regions. The proposed compensator is evaluated and compared experimentally with an uncompensated system on a microcomputer controlled linear motor tracking system in the final section of the paper. The experimental results show the improvement on the maximum velocity error and the root mean square tracking error in the motion-start region ranges from 34% to 53% and from 53% to 75% respectively, and in the motion-reverse region from 48% to 65% and from 79% to 90% respectively.

• 한국공작기계학회논문집
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• 제15권4호
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• pp.44-48
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• 2006

Recently, demand the ultra precision product which is increasing rapidly is used extensively frontier industry field such as semi-conductor, computer, aerospace, precision machine. Ultra precision processing is the portion that is very needed to NT in the field of mechanical engineering. The latest date, together with radical advancement of electronic and photonics industry, necessity of ultra precision processing is on the increase for the manufacture of various kernel parts those are connected with these industrial fields. Specially, require motion accuracy of high resolution of nm order in stroke of hundreds millimeters according as diameter of processing object great and processing accuracy rises. In this case ,the response speed absolute delay because inertial mass of moving part is very large. Therefore, real time motion error compensation becomes very hardly. In this paper, we used ultra precision cutting unit(UPCU) to cope such problem. a UPCU is designed and tested to obtain sub-micrometer from accuracy in diamond turning of flat surfaces. The thermal growth spindle error is compensated for real time using a UPCU driven by piezoelectric actuator along with a laser encoder displacement sensor.

• 산업경영시스템학회지
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• 제35권4호
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• pp.24-32
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• 2012

Of many approaches to reduce motion analysis errors, the compensation method of anatomical landmarks estimates the position of anatomical landmarks during motion. The method models the position of anatomical landmarks with joint angle or skin marker displacement using the data of the so-called dynamic calibration in which anatomical landmark positions are calibrated in ad hoc motions. Then the anatomical landmark positions are calibrated in target motions using the model. This study applies the compensation methods with joint angle and skin marker displacement to three lower extremity motions (walking, sit-to-stand/stand-to-sit, and step up/down) in ten healthy males and compares their performance. To compare the performance of the methods, two sets of kinematic variables were calculated using different two marker clusters, and the difference was obtained. Results showed that the compensation method with skin marker displacement had less differences by 30~60% compared to without compensation. And, it had significantly less difference in some kinematic variables (7 of 18) by 25~40% compared to the compensation method with joint angle. This study supports that compensation with skin marker displacement reduced the motion analysis STA errors more reliably than with joint angle in lower extremity motion analysis.

• 전자공학회논문지
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• 제52권8호
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• pp.29-39
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• 2015

본 논문은 모바일 광학식 손떨림 보정(OIS) 움직임 검출부의 성능과 안정도를 높이기 위하여 퍼지기반 손떨림 상태 검출 및 오차 보상 알고리즘의 설계 및 구현을 기술한다. OIS 움직임 검출을 위한 자이로 센서 출력에는 소자의 고유 오차가 포함되어 있기 때문에 신속한 손떨림 보정과 안정적인 손떨림 상태 검출을 위해서 정확한 오차 보상이 요구된다. 본 연구에서는 퍼지 알고리즘을 기반으로 낮은 연산량을 통해서 손떨림 주파수에 대한 각도 및 위상 오차를 신속하게 줄여서 보정 성능을 개선하였다. 또한 손떨림 각도 크기에 따라 {정지, 작은 손떨림, 큰 손떨림, 팬/틸트} 등의 손떨림 상태를 적절히 구분해서 시스템의 안정성을 향상시켰다. 모바일 OIS 움직임 검출부를 위해 제안된 알고리즘의 성능 및 안정도를 실제 손떨림과 같은 2~12Hz 주파수 범위의 ${\pm}0.5^{\circ}$, ${\pm}0.8^{\circ}$ 손떨림 진동에 대해서 정량적 및 정성적 실험으로써 평가하였다. 실험결과를 통해서 기존 BACF/DCF 알고리즘과 비교해서 평균 3.71dB의 개선된 성능을 검증하였고, 4가지 손떨림 상태를 안정적으로 검출하는 동작을 확인하였다.

• International Journal of Precision Engineering and Manufacturing
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• 제9권4호
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• pp.26-31
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• 2008

A precision four-degree-of-freedom measurement system has been developed for simultaneous measurement of four motion errors of a linear stage, which include straightness and angular errors, The system employs a retro-reflector to detect the straightness errors and a plane mirror to detect the angular errors. A common-path compensation method for laser beam drift is put forward, and the experimental results show that the influences of beam drift on four motion errors can be reduced simultaneously. In comparison with the API 5D laser measuring system, the accuracy for straightness measurement is about ${\pm}1.5{\mu}m$ within the measuring range of ${\pm}650{\mu}m$, and the accuracy for pitch and yaw measurements is about ${\pm}1.5$ arc-seconds within the range of ${\pm}600$ arc-seconds.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1380-1383
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• 2004

The scanning type XY stage is frequently used these days as precision positioning system in equipment for semiconductor or display element. It is requested higher velocity and more precise accuracy for higher productivity and measuring performance. The position accuracy of general stage is primarily affected by the geometric errors caused by parasitic motion of stage, misalignments such as perpendicular error, and thermal expansion of structure. In the case of scanning type stage, H type frame is usually used as base stage which is driven by two actuators such as linear motor. In the point view of scanning process, the stage is used in moving motion. Therefore, dynamic variation is added as significant position error source with other parasitic motion error. Because the scanning axis is driven by two actuators with two position detectors, 2 dimensional position errors have different characteristic compared to general tacked type XY stage. In this study 2D position error of scanning stage is analyzed by 1D heterodyne interferometer calibrator, which can measure 1D linear position error, straightness error, yaw error and pitch error, and perpendicular error. The 2D position error is evaluated by diagonal measurement (ISO230-6). The yaw error and perpendicular error are compensated on the base stage of scanning axis. And, the horizontal straightness error is compensated by cross axis compensation. And, dynamic motion error in scanning motion is analyzed.

• 전자공학회논문지B
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• 제31B권10호
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• pp.99-111
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• 1994

A motion picture compression scheme using subband coding with motion compensation is presneted in this paper. A hierarchical subband decomposition is used to split the image signal into 10 subbands with a 3-layer pyramid structure and motion compensation is used in each band. However, in this case, motion vector information is drastically increased; therefore, initial motion vectors are estimated in the highest pyramid and motion vectors are refined using the reconsructed subband signal in each layer. Simulation results show that the proposed method compares favorably in terms of prediction error energy and side informatio with methods requiring additional information. Images recostructed from the proposed method show good quality compared to those reconstructed using blockwise DCT.

• 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.

• 정보처리학회논문지B
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• 제11B권6호
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• pp.661-666
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• 2004

통신 기술의 발전으로 무선 채널을 이용한 멀티미디어 서비스를 제공하기 위한 방법이 활발히 연구되고 있다. 이에 따라 최근 무선망이나 인터넷과 같이 오류가 많이 발생하는 채널을 통한 비디오의 전송이 급격히 증가하면서 채널 상에서 발생하는 전송에러로 인한 데이터의 손실이 심각한 문제로 대두되고 있으며, 이에 따라 에러 은닉이 주된 관심사로 부각되었다. 에러 은닉 기법은 부가 정보가 필요 없으며, 부호화 기법의 변형 없이 적용이 가능하기 때문에 널리 연구되고 있다. 본 논문에서는, 손실된 블록 주위의 정상블록들 중 움직임 벡터들의 적응적 선택을 이용하여 중간 값을 취한 후, 손실된 블록의 새로운 움직임 벡터로 할당하고, OBMC(Overlapped Block Motion Compensation)을 통해 최종적으로 손실영역을 은닉하게 된다. 이 방법은 연속된 GOB(Group Of Block)의 손실에 있어서 효과적임을 알 수 있었다. 실험 결과 PSNR 성능평가 면에서 제안한 방법의 결과가 기존의 방법들 중 우수한 에러은닉 결과를 내는 MVRI(Motion Vector Rational Interpolation)이나 메디안$.$중첩 에러 은닉 기법에 비해 약 3db정도 향상된 결과를 얻을 수 있었다.

• 한국통신학회논문지
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• 제24권7B호
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• pp.1384-1392
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• 1999

저속 이동 통신 채널과 같은 저속 통신망에서 비디오 전송을 위해서는 시스템에서 요구하는 비디오 전송율을 보장하기 위하여 높은 압축율을 갖는 부호화 방법들이 사용된다. 이러한 부호화 방법들에 의하여 부호화된 비디오가 오류율이 높은 이동 채널로 전송될 때, 비트열에 오류가 발생하면 복호되기 어려울 뿐 아니라 비트열의 다른 부분에도 치명적인 영향을 미치게 된다. 본 논문에서는 비디오 전송 중에 비트열이 손상되어 복호가 불가능한 블록을 복구하기 위한 오류 은폐 알고리듬을 제안한다. 제안하는 오류 은폐 알고리듬은 정상적으로 복호된 주변 블록들의 정보를 이용하여 손실된 블록을 복구한다. 즉, 공간적으로 이웃하는 블록과 손실된 블록간에는 높은 움직임 벡터의 상관성이 있다는 성질을 바탕으로, 중복 블록 움직임 보상(overlapped block motion compensation: OBMC)과 블록 경계 정합(block boundary matching : BBM)을 통하여 손상된 블록의 움직임 벡터를 정확히 추정하는 알고리듬이다. 제안하는 알고리듬은 기존의 오류 은폐 방법들에 비하여 복구된 영상의 PSNR과 시각적인 면에서 우수한 성능을 보임을 실험을 통하여 확인하였다.