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Machine learning algorithms for ICU mortality prediction in community-acquired pneumonia:A standardized validation and calibration study on the NACef cohort 认领 引用
1
作者 Hanane Belmouss Ahmed Aamouche 《Medical Data Mining》 CAS 2026年第3期41-49,共9页
Background:Mortality in intensive care due to community-acquired pneumonia remains high.Although machine learning models have demonstrated promising predictive performance,standardized validation and explicit calibrat... Background:Mortality in intensive care due to community-acquired pneumonia remains high.Although machine learning models have demonstrated promising predictive performance,standardized validation and explicit calibration assessment across independent clinical settings remain limited.Methods:This study systematically reviewed machine learning algorithms for mortality prediction in community-acquired pneumonia.A search across six databases identified 241 records,of which seven met the eligibility criteria.Standalone algorithms meeting predefined selection criteria were subsequently implemented within a standardized validation framework and evaluated on the NACef cohort(n=764;163 deaths,21.2%).Model performance was assessed using nested cross-validation and independent hold-out testing,with evaluation of both discrimination and calibration metrics.Results:Three standalone algorithms,XGBoost,LightGBM,and Logistic Regression,were selected for standardized implementation and evaluation.In nested cross-validation,all models achieved mean AUC values above 0.90.On the independent hold-out test set,uncalibrated AUC values were 0.941 for XGBoost,0.933 for LightGBM,and 0.915 for Logistic Regression,with small absolute differences across models.Recall ranged from 0.818(LightGBM)to 0.969(Logistic Regression),while precision ranged from 0.615(Logistic Regression)to 0.658(LightGBM).Calibration analysis indicated probability misalignment before recalibration.Platt scaling and isotonic regression improved calibration metrics,with isotonic regression achieving the lowest expected calibration error while maintaining comparable discrimination.Conclusion:Logistic Regression,XGBoost,and LightGBM demonstrated comparable discrimination,and calibration improved probability reliability,underscoring the importance of harmonized validation and explicit calibration assessment in clinical machine learning research. 展开更多
关键词 community-acquired pneumonia intensive care unit mortality machine learning algorithms model calibration nested cross-validation
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Data-Driven Calibration of Industrial Robots:A Comprehensive Survey 认领 引用 被引量：2
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作者 Tinghui Chen Weiyi Yang +1 位作者 Shuai Li Xin Luo 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI CSCD 2025年第8期1544-1567,共24页
Industrial robots,as the fundamental component for intelligent manufacturing,have attracted considerable attention from both academia and industry.Since its absolute positioning accuracy can suffer from collision,wear... Industrial robots,as the fundamental component for intelligent manufacturing,have attracted considerable attention from both academia and industry.Since its absolute positioning accuracy can suffer from collision,wear,elastic,or inelastic deformation during its operation,a data-driven calibration(DDC)model has become a trending technique.It utilizes abundant data to decrease the difficulty in building complex system models,making it an economic and efficient approach to robot calibration.This paper conducts a comprehensive survey of the state-of-the-art DDC models with the following six-fold efforts:a)Summarizing the DDC modeling methods;b)Categorizing the latest progress of DDC optimization algorithms;c)Investigating the publicly available datasets and several typical metrics;d)Evaluating several widely adopted DDC models to demonstrate their calibration performance;e)Introducing the applications of the current DDC models;f)Discussing the progressing trend of DDC models.This paper strives to present a systematic and thorough overview of the existing DDC models from modeling to kinematic parameter optimization,thereby providing some guidance for research in this field. 展开更多
关键词 Absolute positioning accuracy data-driven calibration(DDC) industrial robot modeling methods optimization algorithms
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Unfolding analysis of LaBr3:Ce gamma spectrum with a detector response matrix constructing algorithm based on energy resolution calibration 认领 引用 被引量：19
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作者 Rui Shi Xian-Guo Tuo +4 位作者 Huai-Liang Li Yang-Yang Xu Fan-Rong Shi Jian-Bo Yang Yong Luo 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2018年第1期23-31,共9页
With respect to the gamma spectrum, the energy resolution improves with increase in energy. The counts of full energy peak change with energy, and this approximately complies with the Gaussian distribution. This study... With respect to the gamma spectrum, the energy resolution improves with increase in energy. The counts of full energy peak change with energy, and this approximately complies with the Gaussian distribution. This study mainly examines a method to deconvolve the LaBr_3:Ce gamma spectrum with a detector response matrix constructing algorithm based on energy resolution calibration.In the algorithm, the full width at half maximum(FWHM)of full energy peak was calculated by the cubic spline interpolation algorithm and calibrated by a square root of a quadratic function that changes with the energy. Additionally, the detector response matrix was constructed to deconvolve the gamma spectrum. Furthermore, an improved SNIP algorithm was proposed to eliminate the background. In the experiment, several independent peaks of 152Eu,137Cs, and 60Co sources were detected by a LaBr_3:Ce scintillator that were selected to calibrate the energy resolution. The Boosted Gold algorithm was applied to deconvolve the gamma spectrum. The results showed that the peak position difference between the experiment and the deconvolution was within ± 2 channels and the relative error of peak area was approximately within 0.96–6.74%. Finally, a 133 Ba spectrum was deconvolved to verify the efficiency and accuracy of the algorithm in unfolding the overlapped peaks. 展开更多
关键词 Detector response matrix Energy resolution calibration LaBr3:Ce scintillator SNIP background elimination Boosted Gold deconvolution algorithm
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Robot stereo vision calibration method with genetic algorithm and particle swarm optimization 认领 引用 被引量：2
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作者 汪首坤 李德龙 +1 位作者 郭俊杰 王军政 《Journal of Beijing Institute of Technology》 EI CAS 2013年第2期213-221,共9页
Accurate stereo vision calibration is a preliminary step towards high-precision visual posi- tioning of robot. Combining with the characteristics of genetic algorithm （GA） and particle swarm optimization （PSO）, a ... Accurate stereo vision calibration is a preliminary step towards high-precision visual posi- tioning of robot. Combining with the characteristics of genetic algorithm （GA） and particle swarm optimization （PSO）, a three-stage calibration method based on hybrid intelligent optimization is pro- posed for nonlinear camera models in this paper. The motivation is to improve the accuracy of the calibration process. In this approach, the stereo vision calibration is considered as an optimization problem that can be solved by the GA and PSO. The initial linear values can be obtained in the frost stage. Then in the second stage, two cameras＇ parameters are optimized separately. Finally, the in- tegrated optimized calibration of two models is obtained in the third stage. Direct linear transforma- tion （DLT）, GA and PSO are individually used in three stages. It is shown that the results of every stage can correctly find near-optimal solution and it can be used to initialize the next stage. Simula- tion analysis and actual experimental results indicate that this calibration method works more accu- rate and robust in noisy environment compared with traditional calibration methods. The proposed method can fulfill the requirements of robot sophisticated visual operation. 展开更多
关键词 robot stereo vision camera calibration genetic algorithm （GA） particle swarm opti-mization （PSO） hybrid intelligent optimization
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Kinematic Calibration of a 5-DoF Parallel Machining Robot with a Novel Adaptive and Weighted Identification Method Based on Generalized Cross Validation 认领 引用
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作者 Lefeng Gu Fugui Xie 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2025年第2期262-278,共17页
Accurate kinematic calibration is the very foundation for robots'application in industry demanding high precision such as machining.Considering the complex error characteristic and severe ill-posed identification ... Accurate kinematic calibration is the very foundation for robots'application in industry demanding high precision such as machining.Considering the complex error characteristic and severe ill-posed identification issues of a 5-DoF parallel machining robot,this paper proposes an adaptive and weighted identification method to achieve high-precision kinematic calibration while maintaining reliable stability.First,a kinematic error propagation mechanism model considering the non-ideal constraints and the screw self-rotation is formulated by incorporating the intricate structure of multiple chains and a unique driven screw arrangement of the robot.To address the challenge of accurately identifying such a sophisticated error model,a novel adaptive and weighted identification method based on generalized cross validation(GCV)is proposed.Specifically,this approach innovatively introduces Gauss-Markov estimation into the GCV algorithm and utilizes prior physical information to construct both a weighted identification model and a weighted cross-validation function,thus eliminating the inaccuracy caused by significant differences in dimensional magnitudes of pose errors and achieving accurate identification with flexible numerical stability.Finally,the kinematic calibration experiment is conducted.The comparative experimental results demonstrate that the presented approach is effective and has enhanced accuracy performance over typical least squares methods,with maximum position and orientation errors reduced from 2.279 mm to 0.028 mm and from 0.206°to 0.017°,respectively. 展开更多
关键词 Parallel machining robot Accurate kinematic calibration Weighted identification model Adaptive identification algorithm
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An Adaptive Image Calibration Algorithm for Steganalysis 认领 引用
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作者 Xuyu Xiang Jiaohua Qin +2 位作者 Junshan Tan Neal N.Xiong 无 《Computers, Materials & Continua》 SCIE EI 2020年第2期963-976,共14页
In this paper,a new adaptive calibration algorithm for image steganalysis is proposed.Steganography disturbs the dependence between neighboring pixels and decreases the neighborhood node degree.Firstly,we analyzed the... In this paper,a new adaptive calibration algorithm for image steganalysis is proposed.Steganography disturbs the dependence between neighboring pixels and decreases the neighborhood node degree.Firstly,we analyzed the effect of steganography on the neighborhood node degree of cover images.Then,the calibratable pixels are marked by the analysis of neighborhood node degree.Finally,the strong correlation calibration image is constructed by revising the calibratable pixels.Experimental results reveal that compared with secondary steganography the image calibration method significantly increased the detection accuracy for LSB matching steganography on low embedding ratio.The proposed method also has a better performance against spatial steganography. 展开更多
关键词 Calibration algorithm neighborhood node degree ordinary pixel sensitive pixel steganalysis
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Calibration of Pipe Roughness Coefficient Based on Manning Formula and Genetic Algorithm 认领 引用
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作者 于志强 田一梅 +1 位作者 郑毅 赵新华 《Transactions of Tianjin University》 EI CAS 2009年第6期452-456,共5页
This paper presents a method to calibrate pipe roughness coefficient (i.e., Manning n-factor) with genetic algorithm (GA) under multiple loading conditions. Due to the old pipe age as well as deleting valves and blend... This paper presents a method to calibrate pipe roughness coefficient (i.e., Manning n-factor) with genetic algorithm (GA) under multiple loading conditions. Due to the old pipe age as well as deleting valves and blends in the skeleton of distribution network, most of the pipes in hydraulic model of practical water distribution system (WDS) are rough. The commonly used Hazen-Williams C-factor is therefore replaced by Manning n-factor in calibrating WDS hydraulic model. Adjustment to GA is designed, and the program efficiency is improved. A case study shows that the adjustment can save 60% of the total runtime. About 90% of the relative differences between simulated and observed pressures at monitoring locations are lower than 3%, which suggests that the proposed adjustment to the calibration is efficient and effective. 展开更多
关键词 genetic algorithm calibration pipe roughness coefficient Manning n-factor
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A new calibration algorithms of spinning projectile aerodynamic parameters 认领 引用
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作者 丛明煜 张伟 王丽萍 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2005年第4期440-445,共6页
This paper demonstrates that the application of calibration algorithms of aerodynamic parameters for the trajectory of spinning projectile is successful. First, from the point of view of the trajectory simulation, a g... This paper demonstrates that the application of calibration algorithms of aerodynamic parameters for the trajectory of spinning projectile is successful. First, from the point of view of the trajectory simulation, a general summary of well-known trajectory models is given. A five degrees of freedom （5 DOF） model is developed that can match the projectile motion essentially in the vertex region, and the results obtained by 5 DOF model are in close agreement with those of a more sophisticated 6 DOF model for elevation angles above 45 degrees. Secondly, the calibration algorithms have been developed and are summarized. The methods of calibrating the flight trajectory models are compared, and these methods are shown to be effective in the representative cases. In addition, the method of Math number calibration （MNC） is presented; some possible areas in MNC for further investigation are indicated together with benefits to be gained. The utilization of MNC schemes not only allow a worthwhile reduction of calibration rounds firing in range and accuracy （R＆A） trial and production of firing tables （PFT） test, but also make PFT and fire control data （FCD） more cost effective. 展开更多
关键词 trajectory models trajectory simulation spinning projectile aerodynamic parameters calibration algorithms
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An improved self-calibration approach based on adaptive genetic algorithm for position-based visual servo 认领 引用 被引量：1
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作者 Ding LIU Xiongjun WU Yanxi YANG 《控制理论与应用（英文版）》 2008年第3期246-252,共7页
An improved self-calibrating algorithm for visual servo based on adaptive genetic algorithm is proposed in this paper. Our approach introduces an extension of Mendonca-Cipolla and G. Chesi＇s self-calibration for the ... An improved self-calibrating algorithm for visual servo based on adaptive genetic algorithm is proposed in this paper. Our approach introduces an extension of Mendonca-Cipolla and G. Chesi＇s self-calibration for the positionbased visual servo technique which exploits the singular value property of the essential matrix. Specifically, a suitable dynamic online cost function is generated according to the property of the three singular values. The visual servo process is carried out simultaneous to the dynamic self-calibration, and then the cost function is minimized using the adaptive genetic algorithm instead of the gradient descent method in G. Chesi＇s approach. Moreover, this method overcomes the limitation that the initial parameters must be selected close to the true value, which is not constant in many cases. It is not necessary to know exactly the camera intrinsic parameters when using our approach, instead, coarse coding bounds of the five parameters are enough for the algorithm, which can be done once and for all off-line. Besides, this algorithm does not require knowledge of the 3D model of the object. Simulation experiments are carried out and the results demonstrate that the proposed approach provides a fast convergence speed and robustness against unpredictable perturbations of camera parameters, and it is an effective and efficient visual servo algorithm. 展开更多
关键词 Dynamic self-calibration Visual servo Adaptive genetic algorithm Parameter optimizing Essential matrix Computer vision
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DOA estimation and mutual coupling calibration with the SAGE algorithm 认领 引用 被引量：5
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作者 Xiong Kunlai Liu Zhangmeng +1 位作者 Liu Zheng Jiang Wenli 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2014年第6期1538-1543,共6页
In this paper, a novel algorithm is presented for direction of arrival（DOA） estimation and array self-calibration in the presence of unknown mutual coupling. In order to highlight the relationship between the array ... In this paper, a novel algorithm is presented for direction of arrival（DOA） estimation and array self-calibration in the presence of unknown mutual coupling. In order to highlight the relationship between the array output and mutual coupling coefficients, we present a novel model of the array output with the unknown mutual coupling coefficients. Based on this model, we use the space alternating generalized expectation-maximization（SAGE） algorithm to jointly estimate the DOA parameters and the mutual coupling coefficients. Unlike many existing counterparts, our method requires neither calibration sources nor initial calibration information. At the same time,our proposed method inherits the characteristics of good convergence and high estimation precision of the SAGE algorithm. By numerical experiments we demonstrate that our proposed method outperforms the existing method for DOA estimation and mutual coupling calibration. 展开更多
关键词 Array self-calibration Convergence Direction of arrival estima-tion Mutual coupling Space alternating generalized expectation-maximization algorithm
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CALIBRATION OF A 6-DOF SPACE ROBOT USING GENETIC ALGORITHM 认领 引用 被引量：17
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作者 LIU Yu JIANG Yanshu +1 位作者 LIANG Bin XU Wenfu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS 2008年第6期6-13,共8页
The kinematic error model of a 6-DOF space robot is deduced, and the cost function of kinematic parameter identification is built. With the aid of the genetic algorithm （GA） that has the powerful global adaptive pro... The kinematic error model of a 6-DOF space robot is deduced, and the cost function of kinematic parameter identification is built. With the aid of the genetic algorithm （GA） that has the powerful global adaptive probabilistic search ability, 24 parameters of the robot are identified through simulation, which makes the pose （position and orientation） accuracy of the robot a great improvement. In the process of the calibration, stochastic measurement noises are considered. Lastly, generalization of the identified kinematic parameters in the whole workspace of the robot is discussed. The simulation results show that calibrating the robot with GA is very stable and not sensitive to measurement noise. Moreover, even if the robot＇s kinematic parameters are relative, GA still has strong search ability to find the optimum solution. 展开更多
关键词 Robot calibration Position and orientation accuracy Measurement noises Genetic algorithm
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Systematic calibration of a 2-m Ring Solar Telescope based on local interferometry and model comparison 认领 引用
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作者 Renai Liu Jinpeng Li +2 位作者 Zuozifei Song Changyu Zeng Yichun Dai 《Astronomical Techniques and Instruments》 CSCD 2025年第3期175-185,共11页
To address the installation challenges of a 2-m ring Gregorian telescope system,and similar optical systems with a small width-to-radius ratio,we propose a detection method combining local interferometry with a compar... To address the installation challenges of a 2-m ring Gregorian telescope system,and similar optical systems with a small width-to-radius ratio,we propose a detection method combining local interferometry with a comparison model.This method enhances the precision of system calibration by establishing a dataset that delineates the relationship between secondary mirror misalignment and wavefront aberration,subsequently inferring the misalignment from interferometric detection results during the calibration process.For the 2-m ring telescope,we develop a detection model using five local sub-apertures,enabling a root-mean-square detection accuracy of 0:0225λ(λ=632:8 nm)for full-aperture wavefront aberration.The calibration results for the 2-m Ring Solar Telescope system indicate that the root-mean-square value of sub-aperture wavefront aberration reaches 0.104λ,and the root-mean-square value of spliced full-aperture measurement yields reaches 0.112λ.This method offers a novel approach for calibrating small width-toradius ratio telescope systems and can be applied to the calibration of other irregular-aperture optical systems. 展开更多
关键词 Local aperture Model comparison 2-m Ring Solar Telescope System calibration Splicing algorithm
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Geometric Calibration and Mergence Algorithm of Ocular Fundus Images 认领 引用
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《Chinese Journal of Biomedical Engineering(English Edition)》 CAS 1999年第4期94-95,共2页
关键词 Chen Geometric Calibration and Mergence Algorithm of Ocular Fundus Images
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Online calibration of laser-induced breakdown spectroscopy for detection of heavy metals in water 认领 引用 被引量：3
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作者 Yao JIA Mingjun Jianguo Nanjing ZHAO +5 位作者 Li FANG Mingjun MA Deshuo MENG Gaofang YIN LIU Wenqing UU 《Plasma Science and Technology》 SCIE EI CAS CSCD 2018年第9期127-132,共6页
In order to reduce the fluctuation of LIBS detection spectrum of liquid sample,the full-spectrum sum method and the internal standardization method is adopted,using an equal-RSD normalization algorithm to calibrate th... In order to reduce the fluctuation of LIBS detection spectrum of liquid sample,the full-spectrum sum method and the internal standardization method is adopted,using an equal-RSD normalization algorithm to calibrate the detection spectrum.Experiment result shows that the full-spectrum sum method reduced the RSD of parallel samples of Cd and Cr to 9.4% and 11.06% from 28.32% and 31.93% respectively,yielded better overall calibration than the singleelement internal standardization approach,thereby suggesting that the former method is convenient and effective for online calibration of LIBS for detection of aqueous heavy metals. 展开更多
关键词 LIBS aqueous heavy metals spectroscopic stability spectral calibration full-spectrum sum method equal-RSD normalization algorithm
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Scanner external calibration algorithm based on fixed point in robot remanufacturing system 认领 引用 被引量：2
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作者 朱胜 崔培枝 +1 位作者 沈灿铎 郭迎春 《Journal of Central South University》 SCIE EI CAS 2005年第S2期133-137,共5页
This paper deals with the scanner exterior calibration algorithm when the scanner is arranged by the robot and the object scanned is fixed on a rotate device in the Robot Remanufacturing System. The method of calibrat... This paper deals with the scanner exterior calibration algorithm when the scanner is arranged by the robot and the object scanned is fixed on a rotate device in the Robot Remanufacturing System. The method of calibrating the relationship between the scanner coordinate and the robot Tool0, such as the rotation, Rx, Ry, Rz, and the transformation ,Y, Z is studied. The data of Tool0 can be directly obtained from the relationship with the robot base-coordinate. So, the coordinate relationship between the scanner coordinate and the robot base coordinate can be easily gotten. This paper explains the basic algorithm theory, computing method, data collecting process and the resulted data in detail. The calibration algorithm is deduced under the orthogonal coordinate. 展开更多
关键词 scanner calibration algorithm remanufacturing
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Non-crossing Quantile Regression Neural Network as a Calibration Tool for Ensemble Weather Forecasts 认领 引用 被引量：2
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作者 Mengmeng SONG Dazhi YANG +7 位作者 Sebastian LERCH Xiang'ao XIA Gokhan Mert YAGLI Jamie M.BRIGHT Yanbo SHEN Bai LIU Xingli LIU Martin Janos MAYER 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2024年第7期1417-1437,共21页
Despite the maturity of ensemble numerical weather prediction(NWP),the resulting forecasts are still,more often than not,under-dispersed.As such,forecast calibration tools have become popular.Among those tools,quantil... Despite the maturity of ensemble numerical weather prediction(NWP),the resulting forecasts are still,more often than not,under-dispersed.As such,forecast calibration tools have become popular.Among those tools,quantile regression(QR)is highly competitive in terms of both flexibility and predictive performance.Nevertheless,a long-standing problem of QR is quantile crossing,which greatly limits the interpretability of QR-calibrated forecasts.On this point,this study proposes a non-crossing quantile regression neural network(NCQRNN),for calibrating ensemble NWP forecasts into a set of reliable quantile forecasts without crossing.The overarching design principle of NCQRNN is to add on top of the conventional QRNN structure another hidden layer,which imposes a non-decreasing mapping between the combined output from nodes of the last hidden layer to the nodes of the output layer,through a triangular weight matrix with positive entries.The empirical part of the work considers a solar irradiance case study,in which four years of ensemble irradiance forecasts at seven locations,issued by the European Centre for Medium-Range Weather Forecasts,are calibrated via NCQRNN,as well as via an eclectic mix of benchmarking models,ranging from the naïve climatology to the state-of-the-art deep-learning and other non-crossing models.Formal and stringent forecast verification suggests that the forecasts post-processed via NCQRNN attain the maximum sharpness subject to calibration,amongst all competitors.Furthermore,the proposed conception to resolve quantile crossing is remarkably simple yet general,and thus has broad applicability as it can be integrated with many shallow-and deep-learning-based neural networks. 展开更多
关键词 ensemble weather forecasting forecast calibration non-crossing quantile regression neural network CORP reliability diagram post-processing
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Second-order calibration applied to quantification of two active components of Schisandra chinensis in complex matrix 认领 引用 被引量：1
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作者 Xiao-Hua Zhang Hai-Long Wu +6 位作者 Jian-Yao Wang Yao Chen Yong-Jie Yu Chong-Chong Nie Chao Kang De-Zhu Tu Ru-Qin Yu 《Journal of Pharmaceutical Analysis》 CAS 2012年第4期241-248,共8页
The effectiveness of traditional Chinese medicine(TCM)against various diseases urges more low cost,speed and sensitive analytical methods for investigating the phamacology of TCM and providing a theoretical basis for ... The effectiveness of traditional Chinese medicine(TCM)against various diseases urges more low cost,speed and sensitive analytical methods for investigating the phamacology of TCM and providing a theoretical basis for clinical use.The potential of second-order calibration method was validated for the quantification of two effective ingredients of Schisandra chinensis in human plasma using spectrofluorimetry.The results obtained in the present study demonstrate the advantages of this strategy for multi-target determination in complex matrices.Although the spectra of the analytes are similar and a large number of interferences also exist,second-order calibration method could predict the accurate concentrations together with reasonable resolution of spectral profiles for analytes of interest owing to its‘second-order advantage’.Moreover,the method presented in this work allows one to simply experimental procedure as well as reduces the use of harmful chemical solvents. 展开更多
关键词 Traditional Chinese medicine Second-order calibration Schizandrol A Schizandrin B Self-weighted alternating normalized residue fitting(SWANRF)algorithm Alternating normaliza-tion-weighted error(ANWE)algorithm.
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Application of camera calibrating model to space manipulator with multi-objective genetic algorithm 认领 引用 被引量：1
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作者 王中宇 江文松 王岩庆 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第8期1937-1943,共7页
The multi-objective genetic algorithm(MOGA) is proposed to calibrate the non-linear camera model of a space manipulator to improve its locational accuracy. This algorithm can optimize the camera model by dynamic balan... The multi-objective genetic algorithm(MOGA) is proposed to calibrate the non-linear camera model of a space manipulator to improve its locational accuracy. This algorithm can optimize the camera model by dynamic balancing its model weight and multi-parametric distributions to the required accuracy. A novel measuring instrument of space manipulator is designed to orbital simulative motion and locational accuracy test. The camera system of space manipulator, calibrated by MOGA algorithm, is used to locational accuracy test in this measuring instrument. The experimental result shows that the absolute errors are [0.07, 1.75] mm for MOGA calibrating model, [2.88, 5.95] mm for MN method, and [1.19, 4.83] mm for LM method. Besides, the composite errors both of LM method and MN method are approximately seven times higher that of MOGA calibrating model. It is suggested that the MOGA calibrating model is superior both to LM method and MN method. 展开更多
关键词 space manipulator camera calibration multi-objective genetic algorithm orbital simulation and measurement
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Automatic calibration for wobble errors in shallow water multibeam bathymetries 认领 引用
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作者 Tianyu YUN Xianhai BU +3 位作者 Zhe XING Zhendong LUAN Miao FAN Fanlin YANG 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2022年第5期1937-1949,共13页
The wobble errors caused by the imperfect integration of motion sensors and transducers in multibeam echo-sounder systems(MBES)manifest as high-frequency wobbles in swaths and hinder the accurate expression of high-re... The wobble errors caused by the imperfect integration of motion sensors and transducers in multibeam echo-sounder systems(MBES)manifest as high-frequency wobbles in swaths and hinder the accurate expression of high-resolution seabed micro-topography under a dynamic marine environment.There are many types of wobble errors with certain coupling among them.However,those current calibration methods ignore the coupling and are mainly manual adjustments.Therefore,we proposed an automatic calibration method with the coupling.First,given the independence of the transmitter and the receiver,the traditional georeferenced model is modified to improve the accuracy of footprint reduction.Secondly,based on the improved georeferenced model,the calibration model associated with motion scale,time delay,yaw misalignment,lever arm errors,and soundings is constructed.Finally,the genetic algorithm(GA)is used to search dynamically for the optimal estimation of the corresponding error parameters to realize the automatic calibration of wobble errors.The simulated data show that the accuracy of the calibrated data can be controlled within 0.2%of the water depth.The measured data show that after calibration,the maximum standard deviation of the depth is reduced by about 5.9%,and the mean standard deviation of the depth is reduced by about 11.2%.The proposed method has significance in the precise calibration of dynamic errors in shallow water multibeam bathymetrie s. 展开更多
关键词 multibeam echo-sounder systems footprint reduction wobble errors genetic algorithm automatic calibration
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A Flexible Calibration Method of Laser Light-Sectioning System for Online 3D Measurement 认领 引用
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作者 KANG Xin SUN Wei +1 位作者 YIN Zhuoyi LIU Cong 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2021年第6期1048-1057,共10页
A flexible calibration method based on a front-coated flat mirror is proposed for a laser light-sectioning three-dimensional(3D)measurement system. Since the calibration target and its mirror image are spatially separ... A flexible calibration method based on a front-coated flat mirror is proposed for a laser light-sectioning three-dimensional(3D)measurement system. Since the calibration target and its mirror image are spatially separated and can be recorded in an image by a camera,the proposed method requires only a single composite image that contains a non-planar checkerboard pattern,a laser strip projected on the target and their mirror images to complete the calibration of the camera and the laser plane in one step. Levenberg-Marquardt(LM)algorithm is used to optimize the system parameters,and the measurement accuracy and speed are improved to enable online 3D inspection. Static and dynamic online 3D measurements are carried out on a cup and a triple stepped shaft,respectively,to validate the proposed method. The shaft has two steps with the depth of(0.5±0.01)mm and(2±0.01)mm to be measured online when the shaft is rotated and translated at the same time. The measurement results can be output at a frequency of 7 to 11 readings per second with standard deviations of 0.040 mm and 0.051 mm. The experimental results verify the effectiveness and flexibility of the proposed method. 展开更多
关键词 laser light-sectioning system calibration front-coated flat mirror online three-dimentional(3D)measurement Levenberg-Marquardt(LM)algorithm
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