• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.3
• /
• pp.50-57
• /
• 2010

A high precision air bearing stage has been developed and calibrated. This linear-motor driven stage was designed to transport a glass or wafer with the X and Y following errors in nanometer regime. To achieve this level of precision, bar type mirrors were adopted for real time ${\Delta}X$ and ${\Delta}Y$ laser measurement and feedback control. With the laser wavelength variation and instability being kept minimized through strict environment control, the orthogonality of this type of control system becomes purely dependent upon the surface flatness, distortion, and assembly of the bar mirrors. Compensations for the bar mirror distortions and assembly have been performed using the self-calibration method. As a result, the orthogonality error of the stage was successfully decreased from $0.04^{\circ}$ to 2.48 arcsec.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.30 no.6_2
• /
• pp.593-605
• /
• 2012

LiDAR systems provide dense and accurate topographic information. A pre-requisite to achieving the potential accuracy of LiDAR is having a proper system calibration, which aims at estimating all the systematic errors in the system measurements and the mounting parameters relating the different components. This paper presents a rigorous and two approximate methods for LiDAR system calibration. The rigorous approach makes use of the LiDAR equation and the system raw measurements. The approximate approaches utilize simplified LiDAR equations using some assumptions, which allow for less strict requirements regarding the raw measurements. The first presented approximate method, denoted as quasi-rigorous, assumes that we are dealing with a vertical platform (i.e., small pitch and roll angles). This method requires time-tagged point cloud and trajectory position data. The second approximate method, denoted as simplified, assumes that we are dealing with parallel strips, vertical platform, and minor terrain elevation variations compared to the flying height above ground. Such method can be performed using the LiDAR point cloud only. Experimental results using a real dataset, whose characteristics deviate to some extent from the utilized assumptions in the approximate methods, are presented to provide a comparative analysis of the outcome from the introduced methods.

• The KSFM Journal of Fluid Machinery
• /
• v.20 no.1
• /
• pp.59-64
• /
• 2017

Diverter is an essential element in gravimetric calibration method of flowmeter. Error of diverter are influenced by flow velocity profile of nozzle outlet, motion velocity of diverter and detecting location. That's why, time detection position of diverter is tuned through repetitive test for minimizing error of diverter. Further the diverter must be compared with the other institutions test since the influence on the accuracy of the flow meter used in the test. In this paper, errors (flow velocity profile of nozzle outlet, motion velocity of diverter and detecting location) of diverter are decreased by produced uni-direction diverter and error of gravimetric calibration system is decreased. Uni-direction diverter is calibrated by gravimetric calibration system with precision flowmeter, the flowmeter is calibrated by pipe prover and other institutions and uni-direction diverter is evaluated. Uni-direction diverter is not influenced by flow velocity profile of nozzle outlet, motion velocity of diverter and detecting location. As a result, Uni-direction diverter can calibrate in wider scope since increasing ratio of maximum and minimum flow rate of uni-direction diverter.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.1188-1191
• /
• 2017

Thrust is one of the crucial performance parameter of a combustion chamber in the combustion chamber development test. So it is very important to measure an accurate thrust. Thrust calibration test was performed to identify the system characteristics, resistance and linearity of a vertical thrust measurement system(TMS) for accurate thrust measurement. It has been found 6.9% ~ 8.6% errors between the measured thrust by TMS calibration equations and theoretical thrust. It has been confirmed that the TMS calibration is necessary to be performed with the propellant lines connected to the combustion chamber for accurate thrust measurement.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.34S no.11
• /
• pp.148-155
• /
• 1997

Ths signal processing technqiue of FET type electrolyte sensors using the back propagation neural network was studied to reduce the interference effects of the different electrolytes. The FET-type electrolyte sensors, pH-ISFET, K-ISFET, and Ca-ISFET, were prepared to measure the pH, K, and Ca electrolytes. Neural network consisted of three layers was learned with 8 patterns and 9 patterns. The sensor output obtained with arbitrary concentrations was processed by the learned neural network. The errors obtained from calibration curve for pH, K, and Ca were .+-.0.039 pH, .+-.2.508 mmol/l, and .+-.1.807 mmol/l, respectively, without considering the interference effects. The errors of the network output for pH, K, and Ca were reduced to .+-.0.005 pH, .+-.0.436 mmol/l, and .+-.0.381 mmol/l in case of 9 patterns, respectively. the signal processing using the neural network can reduce the errors ofthe electrolyte sensor outputs caused by the interference effect, thereby providing effectiveness in the improvement of the sensor selectivity.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.513-516
• /
• 2003

Phase Measuring Profilometry(PMP) has been developed as one of three dimensional 3-D shape measuring methods. The 3-D profile of an object was calculated from the phase data obtained by the sinusoidal patterns projected on the object. However, in some cases the approximation includes considerable errors. In this paper, the effect on the errors caused by the optical geometry and the calibration procedure in PMP technique are discussed. The errors which occured in the process of calculating the 3-D profile from the phase distribution are investigated theoritically and experimentally.

• Journal of Korean Society of Water and Wastewater
• /
• v.13 no.2
• /
• pp.23-33
• /
• 1999

This study is to investigate the effect of C factor errors on the analysis of water distribution systems. For this purpose, an artificial distribution network and a real distribution network were selected as the study networks. Results are as follows. 1. The C factor of a pipe which has small velocity didn't give significant effect on the analysis of a water distribution system. 2. The effect of decreased value of C factors give more influence on the analysis of water distribution systems than that of the increased values. 3. For the C factor calibration, errors of the residual water heads as well as those of the head losses should be considered together. 4. In the analysis of water distribution systems, changes of C factors can give influences only on the nodes which locate behind the pipe. Therefore, this characteristics should be considered in the selection of nodes for the measurement of water heads.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1992.03a
• /
• pp.131-158
• /
• 1992

Verification, calibration, and compensation are becoming more essential elements for manufacture and maintenance of high performance CMMs. A computer module of volumetric error generation has been developed to calculate volumetric errors (random as well as systematic) from measured parametric errors, accepting most types of CMMs in current use. New transformation rules have been derived to transform all the parametric errors with respect to the origin of working volume considered, then incorporated, then incorporated into the module of error calculation. Two cases of practical CMMs are tested with the developed module, and showed good performance.

• Structural Engineering and Mechanics
• /
• v.43 no.3
• /
• pp.371-394
• /
• 2012

Accurate finite element (FE) models are needed in many applications of Civil Engineering such as health monitoring, damage detection, structural control, structural evaluation and assessment. Model accuracy depends on both the model structure (the form of the equations) and the model parameters (the coefficients of the equations), and can be generally improved through that process of experimental reconciliation known as model updating. However, modelling errors, including (i) errors in the model structure and (ii) errors in parameters excluded from adjustment, may bias the solution, leading to an updated model which replicates measurements but lacks physical meaning. In this paper, an application of ambient-vibration-based model updating to a large-scale benchmark prototype of a building structure is reported in which both types of error are met. The error in the model structure, originating from unmodelled secondary structural elements unexpectedly working as resonant appendages, is faced through a reduction of the experimental modal model. The error in the model parameters, due to the inevitable constraints imposed on parameters to avoid ill-conditioning and under-determinacy, is faced through a multi-model parameterization approach consisting in the generation and solution of a multitude of models, each characterized by a different set of updating parameters. Results show that modelling errors may significantly impair updating even in the case of seemingly simple systems and that multi-model reasoning, supported by physical insight, may effectively improve the accuracy and robustness of calibration.

• Journal of the Optical Society of Korea
• /
• v.19 no.4
• /
• pp.415-420
• /
• 2015

A novel method to measure the scale factor for the all-optical atomic spin inertial measurement device (ASIMD) is demonstrated in this paper. The method can realize the calibration of the scale factor by a self-consistent method with small errors in the quiescent state. At first, the matured IMU (inertial measurement unit) device was fixed on an optical platform together with the ASIMD, and it has been used to calibrate the scale factor for the ASIMD. The results show that there were some errors causing the inaccuracy of the experiment. By the comparative analysis of theory and experiment, the ASIMD was unable to keep pace with the IMU. Considering the characteristics of the ASIMD, the mismatch between the driven frequency of the optical platform and the bandwidth of the ASIMD was the major reason. An all-optical atomic spin magnetometer was set up at first. The sensitivity of the magnetometer is ultra-high, and it can be used to detect the magnetization of spin-polarized noble gas. The gyromagnetic ratio of the noble gas is a physical constant, and it has already been measured accurately. So a novel calibration method for scale factor based on the gyromagnetic ratio has been presented. The relevant theoretical analysis and experiments have been implemented. The results showed that the scale factor of the device was $7.272V/^{\circ}/s$ by multi-group experiments with the maximum error value 0.49%.