Reomtly, Coordinate bieasuring Machines （CMMs） are widely used to measure roundness errors. Roundness is calculated from a large number of points collected from the profiles of the parts. According to the Guide to t...Reomtly, Coordinate bieasuring Machines （CMMs） are widely used to measure roundness errors. Roundness is calculated from a large number of points collected from the profiles of the parts. According to the Guide to the Expression of Uncertainty in Measta- meat （GUM）, all measurement results must have a stated uncertainty associated the titan. However, no CMMs give the uncertainty value of the roundness, because no suitable measrement uncertainty calculation procedure exists. In the case of roundness raeasurement in coordinate metrology, this paper suggests the algorithms for the calculation of the measurement uncertainty of the roudness deviation based on the two mainly used association criteria, LSC and MZC. The calculation of the sensitivity coefficients for the uncertainty calculatiion can be done by autnatic differentiation, in order to avoid introducing additional emars by the traditional difference quotient approxima- tions. The proposed methods are exact and need input data only as the nrasured coordinates of the data points and their associated un- certainties.展开更多
Clearances at joints cause an uncertainty in the actual posture of the end-effector of any mechanism. This uncertainty relays on the clearance dimension and the way these clearances are taken up by the mechanism under...Clearances at joints cause an uncertainty in the actual posture of the end-effector of any mechanism. This uncertainty relays on the clearance dimension and the way these clearances are taken up by the mechanism under the load and the inertial effects at every instant. As a matter of fact, the actual measure of the pose error is often replaced by an uncertainty measure. However, a side effect of the existence of clearances is that they can cause sudden changes in the posture of the mechanism as a motion is performed. Such discontinuities in the position produce task defects and impacts. In this work a tool to determine the pose error due to clearances is presented together with a discontinuity analysis. In addition, effects of mass distribution and inertial effects on such discontinuities are expounded, taking a 3-PRS robot as example.展开更多
Remotely sensed spectral data and images are acquired under significant additional effects accompanying their major formation process, which greatly determine measurement accuracy. In order to be used in subsequent qu...Remotely sensed spectral data and images are acquired under significant additional effects accompanying their major formation process, which greatly determine measurement accuracy. In order to be used in subsequent quantitative analysis and assessment, this data should be subject to preliminary processing aiming to improve its accuracy and credibility. The paper considers some major problems related with preliminary processing of remotely sensed spectral data and images. The major factors are analyzed, which affect the occurrence of data noise or uncertainties and the methods for reduction or removal thereof. Assessment is made of the extent to which available equipment and technologies may help reduce measurement errors.展开更多
Trace element analysis on hair samples has been widely used to assess wildlife and human exposure to different contaminants present in the environment or at the workplace. Pollutants due to the presence of toxic metal...Trace element analysis on hair samples has been widely used to assess wildlife and human exposure to different contaminants present in the environment or at the workplace. Pollutants due to the presence of toxic metals in environment not only enter the body by breading, water, and foodstuff accumulates in hair, but they could be adsorbed directly on the hair from environment. In order to remove adsorbed elements and thus determine the internally bound elements correctly, hair sample must be washed. In the present work, we propose uncertainty estimation for the analytical results that are obtained from determination of cadmium, lead, copper, iron, manganese and nickel in human hair by flame and electrothermal atomic absorption spectrometry （FAAS and ETAAS）. To estimate the uncertainty of analytical result obtained, two types of bias are calculated in the assessment of trueness： a proportional bias and a constant bias. Nested design was applied for calculating proportional bias and Youden method to calculate the constant bias. The results we obtained for proportional bias are calculated from spiked samples. In this case, the concentration found is plotted against the concentration added and the slop of standard addition curve is an estimate of the method recovery. Estimated method of average recovery in human hair is： （1.019 ±0.026）, （0.918 ±0.014）, （1.073±0.016）, （1.0597± 0.017）, （1.073± 0.020） and （0.934± 0.117） for Cd, Pb, Mn, Ni, Fe and Cu respectively.展开更多
To evaluate measurement uncertainty for small sample size and measurement data from an unknown distribution, we propose a grey evaluation method of measurement uncertainty based on the grey relation coefficient. The u...To evaluate measurement uncertainty for small sample size and measurement data from an unknown distribution, we propose a grey evaluation method of measurement uncertainty based on the grey relation coefficient. The uncertainty of measurement is analyzed using grey system theory, and the defects of the grey evaluation model of measurement uncertainty (GEMU) are studied. We then establish an improved grey evaluation model of measurement uncertainty (IGEMU). Simulations show that the precision of IGEMU is greater than that of GEMU, and that sample size has only a small effect on the precision of IGEVU. In particular, IGEMU is applied to evaluating measurement uncertainty for small sample size and measurement data from an unknown distribution. The measurement uncertainty of total profile deviation, which is measured by the CNC gear measuring center, can be evaluated by a combination of IGEMU and the Monte Carlo method.展开更多
基金supported by the National Natural Science Foundation of China(No.50705002,50627501)
文摘Reomtly, Coordinate bieasuring Machines （CMMs） are widely used to measure roundness errors. Roundness is calculated from a large number of points collected from the profiles of the parts. According to the Guide to the Expression of Uncertainty in Measta- meat （GUM）, all measurement results must have a stated uncertainty associated the titan. However, no CMMs give the uncertainty value of the roundness, because no suitable measrement uncertainty calculation procedure exists. In the case of roundness raeasurement in coordinate metrology, this paper suggests the algorithms for the calculation of the measurement uncertainty of the roudness deviation based on the two mainly used association criteria, LSC and MZC. The calculation of the sensitivity coefficients for the uncertainty calculatiion can be done by autnatic differentiation, in order to avoid introducing additional emars by the traditional difference quotient approxima- tions. The proposed methods are exact and need input data only as the nrasured coordinates of the data points and their associated un- certainties.
文摘Clearances at joints cause an uncertainty in the actual posture of the end-effector of any mechanism. This uncertainty relays on the clearance dimension and the way these clearances are taken up by the mechanism under the load and the inertial effects at every instant. As a matter of fact, the actual measure of the pose error is often replaced by an uncertainty measure. However, a side effect of the existence of clearances is that they can cause sudden changes in the posture of the mechanism as a motion is performed. Such discontinuities in the position produce task defects and impacts. In this work a tool to determine the pose error due to clearances is presented together with a discontinuity analysis. In addition, effects of mass distribution and inertial effects on such discontinuities are expounded, taking a 3-PRS robot as example.
文摘Remotely sensed spectral data and images are acquired under significant additional effects accompanying their major formation process, which greatly determine measurement accuracy. In order to be used in subsequent quantitative analysis and assessment, this data should be subject to preliminary processing aiming to improve its accuracy and credibility. The paper considers some major problems related with preliminary processing of remotely sensed spectral data and images. The major factors are analyzed, which affect the occurrence of data noise or uncertainties and the methods for reduction or removal thereof. Assessment is made of the extent to which available equipment and technologies may help reduce measurement errors.
文摘Trace element analysis on hair samples has been widely used to assess wildlife and human exposure to different contaminants present in the environment or at the workplace. Pollutants due to the presence of toxic metals in environment not only enter the body by breading, water, and foodstuff accumulates in hair, but they could be adsorbed directly on the hair from environment. In order to remove adsorbed elements and thus determine the internally bound elements correctly, hair sample must be washed. In the present work, we propose uncertainty estimation for the analytical results that are obtained from determination of cadmium, lead, copper, iron, manganese and nickel in human hair by flame and electrothermal atomic absorption spectrometry （FAAS and ETAAS）. To estimate the uncertainty of analytical result obtained, two types of bias are calculated in the assessment of trueness： a proportional bias and a constant bias. Nested design was applied for calculating proportional bias and Youden method to calculate the constant bias. The results we obtained for proportional bias are calculated from spiked samples. In this case, the concentration found is plotted against the concentration added and the slop of standard addition curve is an estimate of the method recovery. Estimated method of average recovery in human hair is： （1.019 ±0.026）, （0.918 ±0.014）, （1.073±0.016）, （1.0597± 0.017）, （1.073± 0.020） and （0.934± 0.117） for Cd, Pb, Mn, Ni, Fe and Cu respectively.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61108052 and 61108073)the Technology Program of the Educational Office of Hei Longjiang Province in China (Grant No.11553016)
文摘To evaluate measurement uncertainty for small sample size and measurement data from an unknown distribution, we propose a grey evaluation method of measurement uncertainty based on the grey relation coefficient. The uncertainty of measurement is analyzed using grey system theory, and the defects of the grey evaluation model of measurement uncertainty (GEMU) are studied. We then establish an improved grey evaluation model of measurement uncertainty (IGEMU). Simulations show that the precision of IGEMU is greater than that of GEMU, and that sample size has only a small effect on the precision of IGEVU. In particular, IGEMU is applied to evaluating measurement uncertainty for small sample size and measurement data from an unknown distribution. The measurement uncertainty of total profile deviation, which is measured by the CNC gear measuring center, can be evaluated by a combination of IGEMU and the Monte Carlo method.
