An adaptive method of residual life estimation for deteriorated products with two performance characteristics (PCs) was proposed, which was sharply different from existing work that only utilized one-dimensional degra...An adaptive method of residual life estimation for deteriorated products with two performance characteristics (PCs) was proposed, which was sharply different from existing work that only utilized one-dimensional degradation data. Once new degradation information was available, the residual life of the product being monitored could be estimated in an adaptive manner. Here, it was assumed that the degradation of each PC over time was governed by a Wiener degradation process and the dependency between them was characterized by the Frank copula function. A bivariate Wiener process model with measurement errors was used to model the degradation measurements. A two-stage method and the Markov chain Monte Carlo (MCMC) method were combined to estimate the unknown parameters in sequence. Results from a numerical example about fatigue cracks show that the proposed method is valid as the relative error is small.展开更多
In this paper,we propose a roll angle measurement method with a large range based on the photoelectronic autocollimator.According to the corresponding relationship between the rotation position of the measured shaft a...In this paper,we propose a roll angle measurement method with a large range based on the photoelectronic autocollimator.According to the corresponding relationship between the rotation position of the measured shaft and the spot position on the circular trajectory,the roll angle is calculated quickly and conveniently using a simple algorithm.Only a mirror,a coupler and a fine shaft are contained in the measurement system besides the photoelectronic autocollimator.Aiming at the terrible measurement error induced by the axis wobbly error,two measurement schemes are proposed,which are linking the fine precision shaft to the measured shaft for reducing the axis wobbly error and using the segment measurement to enlarge the radius of the circular trajectory.The experimental results show that the measurement error is decreased by ±0.38°.The roll angle error of the mechanism is ±0.14°,and the measurement precision is about ±2′.The proposed method can be widely used in the engineering fields.展开更多
Two kinds of measurement errors have been observed in the recently developed UAT-2 ultrasonic anemometer.One is the flow distortion produced by a"blocking effect",and the other is the angle of attack caused ...Two kinds of measurement errors have been observed in the recently developed UAT-2 ultrasonic anemometer.One is the flow distortion produced by a"blocking effect",and the other is the angle of attack caused by the vertical misalignment of the instrument.Here,we study these errors and discuss the possible correction methods.Via a wind tunnel experiment and numerical simulation,a 3D calibration matrix was developed to correct the"blocking effect".In the field test,the angle of attack was detected by an inclinometer settled on the reference plane of the anemometer,and the instrumental misalignment or tilt was corrected by a coordinate transformation.The combined use of an inclinometer and the proposed correction method may help find a new approach for vertical velocity correction.展开更多
基金Project(60904002)supported by the National Natural Science Foundation of China
文摘An adaptive method of residual life estimation for deteriorated products with two performance characteristics (PCs) was proposed, which was sharply different from existing work that only utilized one-dimensional degradation data. Once new degradation information was available, the residual life of the product being monitored could be estimated in an adaptive manner. Here, it was assumed that the degradation of each PC over time was governed by a Wiener degradation process and the dependency between them was characterized by the Frank copula function. A bivariate Wiener process model with measurement errors was used to model the degradation measurements. A two-stage method and the Markov chain Monte Carlo (MCMC) method were combined to estimate the unknown parameters in sequence. Results from a numerical example about fatigue cracks show that the proposed method is valid as the relative error is small.
基金supported by the National Natural Science Foundation of China(Nos.111742741117427961205021 and 11204299)
文摘In this paper,we propose a roll angle measurement method with a large range based on the photoelectronic autocollimator.According to the corresponding relationship between the rotation position of the measured shaft and the spot position on the circular trajectory,the roll angle is calculated quickly and conveniently using a simple algorithm.Only a mirror,a coupler and a fine shaft are contained in the measurement system besides the photoelectronic autocollimator.Aiming at the terrible measurement error induced by the axis wobbly error,two measurement schemes are proposed,which are linking the fine precision shaft to the measured shaft for reducing the axis wobbly error and using the segment measurement to enlarge the radius of the circular trajectory.The experimental results show that the measurement error is decreased by ±0.38°.The roll angle error of the mechanism is ±0.14°,and the measurement precision is about ±2′.The proposed method can be widely used in the engineering fields.
基金The National Basic Research Program of China(Grant No.2010CB951804)The Strategy Guide for the Specific Task of the Chinese Academy of Sciences(Grant No.XDA10010403)+2 种基金The National Natural Science Foundation of China(Grant No.41375018)Special finance from the China Meteorological Administration(Grant No.GYHY200706034)The National Science and Technology Pillar Program(Grant No.2008BAC37B02)
文摘Two kinds of measurement errors have been observed in the recently developed UAT-2 ultrasonic anemometer.One is the flow distortion produced by a"blocking effect",and the other is the angle of attack caused by the vertical misalignment of the instrument.Here,we study these errors and discuss the possible correction methods.Via a wind tunnel experiment and numerical simulation,a 3D calibration matrix was developed to correct the"blocking effect".In the field test,the angle of attack was detected by an inclinometer settled on the reference plane of the anemometer,and the instrumental misalignment or tilt was corrected by a coordinate transformation.The combined use of an inclinometer and the proposed correction method may help find a new approach for vertical velocity correction.
