• 한국정밀공학회지
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• 제15권1호
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• pp.69-77
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• 1998

Linear displacement accuracy is one of the most important factors that determine machine tool accuracy The laser interferometer has been usually recommended for the measurement of linear displacement accuracy. In this paper, microcomputer aided measurement and compensation system has been developed for the pitch error in a CNC machine tool. For accurate pitch error calculation. the analysis code for the pitch error has been also implemented according to the international standards (ISO). The PC based automatic compensation system for the pitch error is also implemented. A new algorithm for calculating optimum value for pitch error compensation is proposed, minimizing the deviation at each target points. The development system has been applied to a practical CNC maching center and the performance has been demonstrated.

• 대한기계학회논문집A
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• 제32권10호
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• pp.823-830
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• 2008

We present a high-accuracy digital-to-analog (DA) actuator using a load spring, specially designed to compensate the output displacement errors caused by fabrication errors. The compensated linear DA actuator is capable to change the slope of input-output modulation line in order to compensate fabrication errors. We design, fabricate, and characterize three different prototypes: one uncompensated design and two compensated designs respectively for a specific value and for a given range of fabrication error. The compensated linear DA actuators show the output displacement errors of $-0.20{\pm}0.23{\mu}m\;and\;-0.13{\pm}0.18{\mu}m$, respectively, reduced by 64.3% and 76.8% of the output displacement error, $0.56{\pm}0.20{\mu}m$, produced by the conventional uncompensated linear DA actuator. We experimentally verify the fabrication error compensation capability of the present compensated linear DA actuators, thus demonstrating high-accuracy actuation performance immune to fabrication errors.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.297-302
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• 1997

Linear displacement accuracy is one of the most important factors that determine machine tool accuracy. The laser interferometer has been usually recommended for the measurement of linear displacement accuracy. In this paper, microcomputer aided measurement and compensation system has been developed forthe pitch error in a CNC machine tool. For accurate pitch error calculation, the analysis code for the pitch error has been also implemented according to the international standards(ISO). The PC based automatic compensation system for the pitch error is also implemented. A new algorithm for calculating optimum value for pitch error compensation is proposed, minimizing the deviation at each target points. The development system has been applied to a practical CNC maching center and the performance has been demonstrated.

• 한국정밀공학회지
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• 제14권11호
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• pp.154-162
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• 1997

A real time error compensation system was developed to improve the quasistatic volumetric accuracy of a machining center by using sensing, metrology, modeling, and computer control techniques. Including thermal errors, 32 error components are formulated in the time-space domain. Fifteen thermal sensors are used to characterize the temperature field of the machine. A compensation controller based on the IBM/PC has been linked with a CNC controller to compensate for machine errors in real time. The maximum linear displacement error in 4 body diagonals were reduced from 140 ${\mu}m$ to 34.5${\mu}m$ with this compensation system, and the spindle thermal drift in space was reduced from 147.3 ${\mu}m$ to 16.8 ${\mu}m$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.150-153
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• 1997

In this paper, a control and data analysis S/W of a dedicated measuring machine for cams is developed. A rotary encoder is employed to measure the angular displacement of the motor, and a linear scale does the linear displacement of the prove. The design and measuring data are interpolated by cubic spline curves respectively to compute the error which is defined by the maximum distance between two curves. Further, optimization module to find the exact error is also developed to remove the error occurred due initial measuring position. The developed system takes only 6 minutes to measure the cam and to analyze the measuring data while the CMM takes about 1 hours even with a skilled operator.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2142-2153
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• 2014

Linearization of transducer characteristic plays a vital role in electronic instrumentation because all transducers have outputs nonlinearly related to the physical variables they sense. If the transducer output is nonlinear, it will produce a whole assortment of problems. Transducers rarely possess a perfectly linear transfer characteristic, but always have some degree of non-linearity over their range of operation. Attempts have been made by many researchers to increase the range of linearity of transducers. This paper presents a method to compensate nonlinearity of Linear Variable Displacement Transducer (LVDT) based on Extreme Learning Machine (ELM) method, Differential Evolution (DE) algorithm and Artificial Neural Network (ANN) trained by Genetic Algorithm (GA). Because of the mechanism structure, LVDT often exhibit inherent nonlinear input-output characteristics. The best approximation capability of optimized ANN technique is beneficial to this. The use of this proposed method is demonstrated through computer simulation with the experimental data of two different LVDTs. The results reveal that the proposed method compensated the presence of nonlinearity in the displacement transducer with very low training time, lowest Mean Square Error (MSE) value and better linearity. This research work involves less computational complexity and it behaves a good performance for nonlinearity compensation for LVDT and has good application prospect.

• 한국정밀공학회지
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• 제17권10호
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• pp.147-154
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• 2000

A new hardware compensation method reducing displacement measurement errors, caused by tilt of index scale in moire linear encoders, has been developed. In conventional moire linear encoders, the detectors are aligned perpendicular to the line of moire fringes this structure is very sensitive to an unwanted tilt of the gratings. In this paper, a newly designed grating, called a phase-modulated grating, is developed to compensate for non-orthogonal errors. By using the phase-modulated grating instead of a conventional index, it is possible to reduce non-orthogonal errors of moire linear encoders.

• 터널과지하공간
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• 제22권3호
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• pp.214-220
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• 2012

터널 굴착에 의해 발생되는 주변 지반의 변위는 터널의 안정성 평가를 위해 중요한 정보가 된다. 실제 시공중 계측에 의해 획득되어 지는 변위량은 불가피하게 계측전 발생한 변위를 포함하지 못하게 된다. 따라서, 계측이 이루어진 시점을 고려하여 계측전 발생한 변위량을 예측하는 것은 매우 중요하다. 본 연구에서는 초기 계측이 이루어진 시점에 따라 계측전 변위 예측의 정확도를 굴착면과 계측지점의 이격거리만을 고려하여 통계적 기법으로 고찰하였다. 또한, 계측 오차가 변위 예측결과에 미치는 영향을 몬테카를로 시뮬레이션을 통하여 살펴보았다. 연구결과 초기 계측이 이루어진 이격거리가 커질수록 전체 변위 이력곡선의 예측 정확도는 급격히 감소하였으며, 계측오차가 커질수록 예측 정확도가 낮아지는 경향을 확인하였다.

• 한국정밀공학회지
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• 제30권6호
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• pp.607-614
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• 2013

In this study, effect of the sensor gain error is theoretically analyzed and simulated when mixed sequential two-prove method(MTPM) is applied for the precision measurement of straightness error of a linear motion table. According to the theoretical analysis, difference of the gain errors between two displacement sensors increases measurement error dramatically and alignment error of the straightedge is also amplified by the sensor gain difference. On the other hand, if the gain errors of the two sensors are identical, most of error terms are cancelled out and the alignment error doesn't give any influence on the measurement error. Also the measurement error of the straightness error is minimized compared with that of the straightedge's form error owing to close relationship between straightness error and angular motion error of the table in the error terms.

• 한국생산제조학회지
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• 제4권3호
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• pp.58-66
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• 1995

It is very important to test motion accuracy and performance of NC machine tools as they affect that of all other machines machined by them in industry. In this paper, in has become possible to detect errors of linear displacement of radial direction for circular motion test using newly assembled magnetic type of linear scales so called Magnescale ball bar system, and to calculate time interval getting error motion data and revolution angle of circular motion in machining center using tick pulses come out from computer. And a set of error data gotten from test is expressed to a plot by computer treatment and to numerics of error motion by statistical treatment and results of test are compared with those of Renishaw ball bar system.