- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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UTILIZA??O DE ALVOS CODIFICADOS DO TIPO ARUCO NA AUTOMA??O DO PROCESSO DE CALIBRA??O DE C?MARAS
摘要： This paper presents a proposal for the automation of the camera calibration process, locating and measuring image points in coded targets with sub-pixel precision. This automatic technique helps minimize localization errors, regardless of camera orientation and image scale. To develop this technique, several types of coded targets were analyzed and the ARUCO type was chosen due to its simplicity, ability to represent up to 1024 different targets and availability of source code implemented with the OpenCV library. ARUCO targets were generated and two calibration sheets were assembled to be used for the acquisition of images for camera calibration. The developed software can locate targets in the acquired images and it automatically extracts the coordinates of the four corners with sub-pixel accuracy. Experiments were conducted with real data showing that the targets are correctly identified unless excessive noise or fragmentation occurs mainly in the outer target square. The results with the calibration of a low cost camera showed that the process works and that the measurement accuracy of the corners achieves sub-pixel precision.
关键词： Calibration Chambers,Targets Coded,Photogrammetry,ARUCO,OpenCV,Sub-Pixel
更新于2025-09-23 15:22:29
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An interactive cameraless projector calibration method
摘要： The geometric calibration of projectors is a demanding task in many areas related to computer vision, virtual reality or augmented reality, to name some. Up to date, different methods have been proposed to retrieve the intrinsic and extrinsic parameters of projectors. During the last 20 years, researchers have used cameras as means to calibrate projectors in order to automatize the process. However, this might add: (1) complexity in terms of mathematical formulation; (2) restrictions in terms of camera locations relative to projectors; and (3) additional errors (those due to the camera calibration itself). Most of these camera-based methods make use of planar homographies, and others require an extended calibration process (for both the camera and the projector). In this paper, we present an approach that combines a direct transformation method (DLT) with projected augmented reality to perform an interactive calibration of projectors without the need for cameras. This method is based on non-coplanar points and 2D/3D correspondences, which are interactively established. Intrinsic and extrinsic calibration is achieved in a single step, making use of the DLT. The method rescues old approaches to calibrate projectors, but brings the new capabilities of interactive systems, all integrated in a single software solution. We conduct different experiments by considering two projector setups and two different sets of control points, proving that the accuracy of the method in the real space can be between one and two pixels.
关键词： Photogrammetry,Augmented reality,DLT,Cameraless,Interactive,Calibration,Projector
更新于2025-09-23 15:22:29
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Ambient Tracer-LIF for 2-D quantitative measurement of fuel concentration in gas jets
摘要： A novel ambient tracer LIF technique with addition of tracer into ambient gas is proposed in this study to quantitatively measure the two dimensional (2-D) fuel concentration distribution in high-pressure gas jets. Firstly, the fundamental principle of the ambient tracer-LIF technique is described, and the equation of fuel concentration in a jet is deduced from the ambient fluorescence intensity. In the ambient tracer-LIF technique, the on-site calibration can be performed, and much more degrees of freedom in selection of tracers or target fuels can be achieved in principle. Then, the experiments are carried out with the high pressure gas injected into the environment doped with acetone in an optical accessible constant volume vessel. The fluorescence in the ambient is induced by using the 266 nm laser, and is recorded by the ICCD camera. The dedicated image processing is implemented to reduce the uncertainty and obtain the quantitative fuel concentration distribution in the jet. The uncertainties of the measurement results are evaluated, including both the systematic and random errors. The uncertainty propagation analysis shows that the measurement uncertainty increases with the local fuel concentration decreasing, and at the boundary regions of the jet, where the mixture is over lean, the relative uncertainty goes up to 26%. Finally, the temporal variations of the fuel concentration distribution in the gas jet are presented, and the effects of injection pressure are discussed. These results are believed to be valuable for development of numerical models and combustion system designs.
关键词： 2-D quantitative concentration measurement,On-site calibration,Ambient tracer-LIF,Natural gas direct injection
更新于2025-09-23 15:22:29
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Spectroscopy approach to methanol detection in waste fat methyl esters
摘要： Second-generation biodiesel manufactured from waste cooking oils (WCO) and inedible animal fats (AF) are one of the alternatives to the first generation (1G) vegetable oil-based biodiesel. In this study, a quality control method is proposed to evaluate methanol content in waste fat methyl esters and is based on near infrared spectroscopy (NIR) combined with multivariate analysis. More specifically, calibration models are constructed using partial least squares regression (PLS) for the prediction of methanol content in rapeseed oil methyl ester (ROME), waste cooking oil methyl ester (WCOME), chicken fat methyl ester (CFME) and pork fat methyl ester (PFME) by Vis-NIR spectrometer. The calibration models are based on the absorbance spectra and computed data from five wavelength regions of 400–2170 nm, 780–2170 nm, 1400–2170 nm, 1400–1600 nm and 1970–2170 nm. For the cases with the highest prediction ability obtained in this study, the coefficient of determination of the model's goodness-of-fit for methanol concentrations range 0–5% (v/v) was R2 N 0.990, and for concentrations 0–1% (v/v) was R2 N 0.994, indicating the spectroscopic approach effectiveness in methanol content detection relevant to the biofuel quality assessment. A pseudo-univariate limits of detection (LODpu) and quantification (LOQpu) as well as ratio of performance to deviation (RPD) were used to confirm the validity and to evaluate the practical applicability of developed models. In addition, the obtained results indicate the possibility of developing a transmission sensor for online monitoring of the production process and the quality of biofuel.
关键词： PLS calibration models,Waste cooking oil,Animal fat biofuel,Vis-NIR spectroscopy
更新于2025-09-23 15:21:21
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Star sensor installation error calibration in stellar-inertial navigation system with a regularized backpropagation neural network
摘要： The star sensor is the attitude reference in a stellar-inertial navigation system. It is essential to acquire the star sensor installation error, which has a great influence on the system navigation performance. However, traditional methods have a poor tolerance for a large range of installation errors, especially when the system works under a separate installation mode. In this paper a novel calibration method, using a regularized backpropagation (BP) neural network, is proposed. With a specially designed calibration procedure, the neural network is structured with BP and the regularization is improved. The network training is conducted for parameter solidification. The calibration can be achieved without formula derivation and numerical calculation under both small and large installation errors. In the experiment, the calibration accuracy is about 5 arcsec under small installation errors and about 20 arcsec under large installation errors, which is much better than a Kalman filter. The proposed method has the potential to be a universal star sensor calibration method under integrative installation mode or separated installation mode with large installation error.
关键词： neural network,installation error calibration,star sensor
更新于2025-09-23 15:21:21
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[IEEE 2017 IEEE 7th Annual International Conference on CYBER Technology in Automation, Control, and Intelligent Systems (CYBER) - Honolulu, HI, USA (2017.7.31-2017.8.4)] 2017 IEEE 7th Annual International Conference on CYBER Technology in Automation, Control, and Intelligent Systems (CYBER) - Modeling and Stability Analysis of Robot Calibration System Based on Dual PSD
摘要： Industrial robot repeat positioning accuracy is high, but the absolute positioning accuracy is low, which greatly affects the application of offline programming. Compared with the traditional method, calibration method based on dual-PSD provides more efficient way for improving absolute positioning accuracy of robot. However, the required alignment of laser beam to shoot at the two PSD centers was performed separately, which required to pre-known some parameters for the alignment task. This paper proposes a simultaneous laser beam alignment method without knowing these parameters to perform the laser beam alignment task. In this paper, the motion of the end-effector is divided into translational motion and rotational motion. By designing translational motion and rotational motion controller of the robot end-effector respectively, the unknown parameters in the model are estimated, and the laser spot is alligned with the double PSD at the same time. Stability analysis.
关键词： calibration,industrial robot,dual PSD
更新于2025-09-23 15:21:21
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First tests of a Newtonian calibrator on an interferometric gravitational wave detector
摘要： The ongoing improvements of the advanced gravitational wave (GW) detectors are setting challenging requirements on instrument calibration. We report tests of a calibration technique, based on the well-known gravitational force, which has been applied for the first time on a large interferometer. The results obtained with Advanced Virgo are in good agreement with the predictions and with the usual calibration method. This technique is expected to lead to accurate absolute calibration at the sub-percent level in the coming years, matching the needs of the rapidly evolving GW science.
关键词： gravitational wave detector,Virgo,Newtonian force,calibration
更新于2025-09-23 15:21:21
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Pixel-to-pixel variation on a calibrated PILATUS3-based multi-energy soft x-ray detector
摘要： A multi-energy soft x-ray pin-hole camera based on the PILATUS3 100 K x-ray detector has recently been installed on the Madison Symmetric Torus. This photon-counting detector consists of a two-dimensional array of ～100 000 pixels for which the photon lower-threshold cutoff energy Ec can be independently set for each pixel. This capability allows the measurement of plasma x-ray emissivity in multiple energy ranges with a unique combination of spatial and spectral resolution and the inference of a variety of important plasma properties (e.g., T e, nZ, Z eff). The energy dependence of each pixel is calibrated for the 1.6–6 keV range by scanning individual trimbit settings, while the detector is exposed to ?uorescence emission from Ag, In, Mo, Ti, V, and Zr targets. The resulting data for each line are then ?t to a characteristic "S-curve" which determines the mapping between the 64 possible trimbit settings for each pixel. The statistical variation of this calibration from pixel-to-pixel was explored, and it was found that the discreteness of trimbit settings results in an effective threshold resolution of ?E < 100 eV. A separate calibration was performed for the 4–14 keV range, with a resolution of ?E < 200 eV.
关键词： energy calibration,x-ray detector,photon-counting,multi-energy soft x-ray,plasma x-ray emissivity,PILATUS3
更新于2025-09-23 15:21:21
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Temperature Compensation Method for Digital Cameras in 2D and 3D Measurement Applications
摘要： This paper presents the results of several studies concerning the effect of temperature on digital cameras. Experiments were performed using three different camera models. The presented results conclusively demonstrate that the typical camera design does not adequately take into account the effect of temperature variation on the device’s performance. In this regard, a modified camera design is proposed that exhibits a highly predictable behavior under varying ambient temperature and facilitates thermal compensation. A novel temperature compensation method is also proposed. This compensation model can be applied in almost every existing camera application, as it is compatible with every camera calibration model. A two-dimensional (2D) and three-dimensional (3D) application of the proposed compensation model is also described. The results of the application of the proposed compensation approach are presented herein.
关键词： temperature effect,3D imaging,structured light,camera calibration
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Linking SNPP and NOAA-20 Cris Toward Measurement Consistency and Climate Data Records
摘要： Quantifying the radiometric difference and creating a calibration link between SNPP and NOAA-20 CrIS are crucial for creating CrIS long-term climate data records and establishing the space-based calibration standard. This study uses two methods (direct and indirect comparison) to comprehensively evaluate the radiometric consistence and differences between SNPP and NOAA-20 CrIS in term of global distribution, scene temperatures, and orbital variation. The root causes of these differences are explored and the strategy to resolve these differences is proposed.
关键词： CrIS,NOAA-20,Inter-calibration,SNPP
更新于2025-09-23 15:21:21