• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.409-412
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• 2002

This paper presents a measurement method to compromise surface error in surface machining processes. In order to compromise the surface error in machining process, on-machine measurement is essential. There are two kinds of on-machine measurement methods available to measure the surface errors in flat workpieces: i.e., surface scanning method and sensor scanning method. However, motion errors are inevitably engaged in both methods. This paper proposes a new idea to measure the surface error for error compensation. The measurement system consists of a laser, a CCD camera and processing system, a carrier system with a stylus, and some optical units. The experimental results show that the proposed method is useful to compensate the surface errors of machined workpieces.

• 한국정밀공학회지
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• 제27권5호
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• pp.7-13
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• 2010

The integrity and accuracy of the drilling hole are decided by positional error, diameter error, the roundness, the straightness, the cylindericity, size of the burr, the surface roundness and others. Among these parameters, positional error and diameter error have the most important parameters. The diameter error has been widely studied, but there has been little research done about the positional error due to the difficulty of measuring it. The measurement of hole location and diameter would be performed by CMM(Coordinate Measurement Machine). However, the usage of CMM requires much time and cost. In order to overcome the difficulties, we have developed a hole location and diameter error measuring device using machine vision. The developed measurement device attached to a CNC machine can determine hole quality quickly and easily.

• Journal of Magnetics
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• 제21권4호
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• pp.529-536
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• 2016

Magnetically suspended sensitive gyroscopes (MSSGs) provide an interesting alternative for achieving precious attitude angular measurement. To effectively reduce the measurement error caused by dynamic imbalance, this paper proposes a novel compensation method based on analysis and modeling of the error for a MSSG. Firstly, the angular velocity measurement principle of the MSSG is described. Then the analytical model of dynamic imbalance error has been established by solving the complex coefficient differential dynamic equations of the rotor. The generation mechanism and changing regularity of the dynamic imbalance error have been revealed. Next, a compensation method is designed to compensate the dynamic imbalance error and improve the measurement accuracy of the MSSG. The common issues caused by dynamic imbalance can be effectively resolved by the proposed method in gyroscopes with a levitating rotor. Comparative simulation results before and after compensation have verified the effectiveness and superiority of the proposed compensation method.

• Smart Structures and Systems
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• 제25권2호
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• pp.135-153
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• 2020

There has been a sustained interest towards the non-contact structural displacement measurement by means of videogrammetric technique. On the way forward, one of the major concerns is the spurious image drift induced by temperature variation. This study therefore carries out an investigation into the temperature effect of videogrammetric technique, focusing on the exploration of the mechanism behind the temperature effect and the elimination of the temperature-caused measurement error. 2D videogrammetric measurement tests under monotonic or cyclic temperature variation are first performed. Features of measurement error and the casual relationship between temperature variation and measurement error are then studied. The variation of the temperature of digital camera is identified as the main cause of measurement error. An excellent linear relationship between them is revealed. After that, camera parameters are extracted from the mapping between world coordinates and pixels coordinates of the calibration targets. The coordinates of principle point and focal lengths show variations well correlated with temperature variation. The measurement error is thought to be an outcome mainly attributed to the variation of the coordinates of principle point. An approach for eliminating temperature-caused measurement error is finally proposed. Correlation models between camera parameters and temperature are formulated. Thereby, camera parameters under different temperature conditions can be predicted and the camera projective matrix can be updated accordingly. By reconstructing the world coordinates with the updated camera projective matrix, the temperature-caused measurement error is eliminated. A satisfactory performance has been achieved by the proposed approach in eliminating the temperature-caused measurement error.

• Current Optics and Photonics
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• 제4권6호
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• pp.500-508
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• 2020

The rifling angle of artillery is an important parameter, and its determination plays a key role in the stability, hit rate, accuracy and service life of artillery. In this study, we propose an optical measurement method for the rifling angle based on angle error correction. The method is based on the principle of geometrical optics imaging, where the rifling on the inner wall of the artillery barrel is imaged on a CCD camera target surface by an optical system. When the measurement system moves in the barrel, the rifling image rotates accordingly. According to the relationship between the rotation angle of the rifling image and the travel distance of the measurement system, different types of rifling equations are established. Solving equations of the rifling angle are deduced according to the definition of the rifling angle. Furthermore, we added an angle error correction function to the method that is based on the theory of dynamic optics. This function can measure and correct the angle error caused by the posture change of the measurement system. Thus, the rifling angle measurement accuracy is effectively improved. Finally, we simulated and analyzed the influence of parameter changes of the measurement system on rifling angle measurement accuracy. The simulation results show that the rifling angle measurement method has high measurement accuracy, and the method can be applied to different types of rifling angle measurements. The method provides the theoretical basis for the development of a high-precision rifling measurement system in the future.

• 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.

• Journal of the Korean Data and Information Science Society
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• 제28권3호
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• pp.709-720
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• 2017

In healthcare and medical research, many important variables have a measurement error such as body mass index and laboratory data. It is also not easy to collect samples of large size because of high cost and long time required to collect the target patient satisfied with inclusion and exclusion criteria. Beside, the demand for solving a complex scientific problem has highly increased so that a semiparametric regression approach could be of substantial value solving this problem. To address the issues of measurement error, small domain and a scientific complexity, we conduct a multivariable Bayesian smoothing under structural measurement error covariate in this article. Specifically we enhance our previous model by incorporating other useful auxiliary covariates free of measurement error. For the regression spline, we use a radial basis functions with fixed knots for the measurement error covariate. We organize a fully Bayesian approach to fit the model and estimate parameters using Markov chain Monte Carlo. Simulation results represent that the method performs well. We illustrate the results using a national survey data for application.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 2006년도 추계 학술대회
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• pp.199-204
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• 2006

ANOVA is widely used for measurement system analysis. It assumes that the measurement error is normally distributed, which may not be seen in some industrial cases. In this study, the estimates of the measurement system variability and PTR (precision-to-tolerance ratio) are obtained by using weighted standard deviation for the case where the measurement error is non-normally distributed. The Standard Bootstrap method is used for estimating confidence intervals of measurement system variability and PTR. The point and confidence interval estimates for the cases with normally distributed measurement error are compared to those with non-normally distributed measurement errors through computer simulation.

• 소음진동
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• 제8권6호
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• pp.1023-1029
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• 1998

When one attempts to construct a hologram. one finds that there are many sources of measurement errors. These errors are even amplified if one predicts the pressures close to the sources. The pressure estimation errors depend on the following parameters: the measurement spacing on the hologram plane. the prediction spacing on the prediction plane. and the distance between the hologram and the prediction plane. This raper analyzes quantitatively the errors when these are distributed irregularly on the hologram plane The sensor mismatch and inaccurate measurement location. position mismatch. are mainly addressed. In these cases. one can assume that the measurement is a sample of many measurement events. The bias and random error are derived theoretically. Then the relationship between the random error amplification ratio and the parameters mentioned above is examined quantitatively in terms of energy.

• Journal of Biosystems Engineering
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• 제22권3호
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• pp.269-278
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• 1997

An automatic level measurement system was developed to level the land fer direct seeding of rice. A laser transmitter/receiver set was used to measure land-level. The inclination error occurred in level measurement on irregular land surface could be compensated by attaching rotating mass. The level measuring experiments were performed on three kinds of different shapes(step, random, sine). This system could accurately measure step level of which amplitude was 40mm in 0.5s, random level change within $\pm$ 5mm maximum measurement error, and sine level change of which spatial frequency was 0.5m-1. To verify performance of the inclination error compensation system, frequency transfer function(acceleration input vs. inclination error) was computed by spectral analysis. The inclination error was decreased about 20㏈ by error compensation system.