- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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3D tracking of multiple onsite workers based on stereo vision
摘要： Varied sensing technologies have been delved in for positioning workers and equipment in construction sites. Vision-based technology has been received growing attentions by the virtue of its tag-free and inexpensive con?guration. One of the core research works in this area was the use of stereo camera system for tracking 3D locations of construction resources. However, the previous work was limited to tracking of a single entity. To overcome the limitation, this paper presents a new framework for tracking multiple workers. The proposed framework supplements the previous work by embedding an additional step, entity matching, which ?nds corresponding matches of tracked workers across two camera views. Entity matching takes advantage of the epipolar geometry and workers' motion directions for ?nding correct pairs of a worker's projections on two image planes. This paper also presents an e?ective approach of camera calibration for positioning entities located a few tens of meters away from the cameras. The proposed framework is evaluated based on completeness, continuity, and localization accuracy of the generated trajectories. The evaluation results have shown its capability of retrieving 96% of actual movements, within localization errors of 0.821 m with 99.7% con?dence.
关键词： Occlusion,Computer vision,Entity matching,Tracking,Construction worker,Site monitoring,Camera calibration
更新于2025-09-23 15:21:01
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[ACM Press the 12th International Conference - Eindhoven, Netherlands (2018.09.03-2018.09.04)] Proceedings of the 12th International Conference on Distributed Smart Cameras - ICDSC '18 - Hand-Eye Camera Calibration with an Optical Tracking System
摘要： This paper presents a method for hand-eye camera calibration via an optical tracking system (OTS) faciltating robotic applications. The camera pose cannot be directly tracked via the OTS. Because of this, a transformation matrix between a marker-plate pose, tracked via the OTS, and the camera pose needs to be estimated. To this end, we evaluate two different approaches for hand-eye calibration. In the first approach, the camera is in a fixed position and a 2D calibration plate is displaced. In the second approach, the camera is also fixed, but now a 3D calibration object is moved. The first step of our method consists of collecting N views of the marker-plate pose and the calibration plates, acquired via OTS. This is achieved by keeping the camera fixed and moving the calibration plate, while taking a picture of the calibration plate using the camera. A dataset is constructed that contains marker-plate poses and the relative camera poses. Afterwards, the transformation matrix is then computed, following a least-squares minimization. Accuracy in hand-eye calibration is computed in terms of re-projection error, calculated based on camera homography transformations. For both approaches, we measure the changes in accuracy as a function of the number of poses used for each calibration, while we define the minimum number of poses required to obtain a good camera calibration. Results of the experiments show similar performances for the two evaluated methods, achieving a median value of the re-projection error at N = 25 poses of 0.76 mm for the 2D calibration plate and 0.70 mm for the 3D calibration object. Also, we have found that minimally 15 poses are required to achieve a good camera calibration.
关键词： optical tracking system,neurosurgery,augmented reality,Hand-eye calibration,endoscope,tracking
更新于2025-09-23 15:21:01
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Stereo Camera Head-Eye Calibration Based on Minimum Variance Approach Using Surface Normal Vectors
摘要： This paper presents a stereo camera-based head-eye calibration method that aims to ?nd the globally optimal transformation between a robot’s head and its eye. This method is highly intuitive and simple, so it can be used in a vision system for humanoid robots without any complex procedures. To achieve this, we introduce an extended minimum variance approach for head-eye calibration using surface normal vectors instead of 3D point sets. The presented method considers both positional and orientational error variances between visual measurements and kinematic data in head-eye calibration. Experiments using both synthetic and real data show the accuracy and ef?ciency of the proposed method.
关键词： stereo camera,humanoid robot,surface normal vector,minimum variance approach,head-eye calibration
更新于2025-09-23 15:21:01
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A Study on the Uncertainty of a Laser Triangulator Considering System Covariances
摘要： A laser triangulation system, which is composed of a camera and a laser, calculates distances between objects intersected by the laser plane. Even though there are commercial triangulation systems, developing a new system allows the design to be adapted to the needs, in addition to allowing dimensions or processing times to be optimized; however the disadvantage is that the real accuracy is not known. The aim of the research is to identify and discuss the relevance of the most significant error sources in laser triangulator systems, predicting their error contribution to the final joint measurement accuracy. Two main phases are considered in this study, namely the calibration and measurement processes. The main error sources are identified and characterized throughout both phases, and a synthetic error propagation methodology is proposed to study the measurement accuracy. As a novelty in uncertainty analysis, the present approach encompasses the covariances of correlated system variables, characterizing both phases for a laser triangulator. An experimental methodology is adopted to evaluate the measurement accuracy in a laser triangulator, comparing it with the values obtained with the synthetic error propagation methodology. The relevance of each error source is discussed, as well as the accuracy of the error propagation. A linearity value of 40 μm and maximum error of 0.6 mm are observed for a 100 mm measuring range, with the camera calibration phase being the main error contributor.
关键词： accuracy,camera calibration,laser triangulation,laser calibration,uncertainty,covariances
更新于2025-09-23 15:19:57
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Laser optical frequency combs and their applications in optical fibre communication systems and astrophysics
摘要： This paper examines the generation and applications of laser optical frequency combs (LOFCs). The unique properties of LOFCs are widely used in spectroscopy and metrology, in particular for making ultra-accurate optical clocks. The use of LOFCs contributes to advances in optical fibre communication systems and studies pertaining to fundamental problems of astrophysics, such as the search for and investigation of exoplanets and verification of the hypothesis that physical constants vary with time.
关键词： exoplanets,optical frequency comb,calibration of astronomical spectrographs,multiplexing,Doppler spectroscopy
更新于2025-09-23 15:19:57
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Spectral analysis of Miracle Moringa tree leaves using X-ray photoelectron, laser induced breakdown and inductively coupled plasma -optical emission spectroscopic techniques
摘要： The antioxidant Moringa oleifera (a medicinal plant) leaves (MOLs) containing diverse nutrients are highly beneficial for the human health. The MOLs upon consumption can lower the blood sugar, cure the heart diseases, and reduce the inflammation. In this perception, the “primary nutrients contents” in the dry MOLs (pellet samples) were evaluated for the first time using the XPS, LIBS and ICP-OES techniques. The XPS analysis of the MOLs showed the presence of vital elements like calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu), phosphorous (P), sulfur (S) and zinc (Zn). The LIBS analyses of the MOLs revealed the atomic and ionic spectral lines corresponding to the essential nutrients such as the Ca, Na, K, Fe, Mg, Mn, Cu, P, S and Zn. The calibration free LIBS algorithm (CF-LIBSA) was developed to quantify the content of each element in the dry MOLs. In addition, the LIBS results were validated by the analysis using ICP-OES standard analytical technique. The elemental contents in the MOLs obtained from the CF-LIBS analyses were counter verified by the ICP-OES results. Present results are highly valuable for the development of a traditional herbal medicine using the miracle MOLs.
关键词： Calibration free LIBS algorithm,Laser induced breakdown spectroscopy,Moringa oleifera leaves,X-ray photoelectron spectroscopy,Inductively coupled plasma atomic emission spectroscopy
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Quantifying the Relationship Between Higher Photovoltaic Module Efficiency and the Adoption of Distributed Solar
摘要： Some applications of data from the Clouds and the Earth’s Radiant Energy System (CERES) scanning radiometer require the use of the point response function (PRF), which describes the influence of radiance from each point on the measurement. A radiance source for the measurement of the PRF of the CERES instruments was built and installed into the Radiometric Calibration Facility, in which the CERES instruments have been calibrated. The design and application of the PRF source and the computation of the PRF from these measurements are described. In order to compare the PRF based on measurements with the theoretical PRF, it is necessary to account for the finite size of the beam from the source. The use of the PRF source and the analysis of the data are demonstrated by application to the FM-5 instrument. The measured results compare well with theory for the CERES instruments and are presented for FM-5.
关键词： Aqua,Terra,point spread function,radiometry,National Polar-orbiting Partnership (NPP),Earth radiation budget,point response function (PRF),calibration,Clouds and the Earth’s Radiation Energy System (CERES)
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE Transportation Electrification Conference and Expo, Asia-Pacific (ITEC Asia-Pacific) - Seogwipo-si, Korea (South) (2019.5.8-2019.5.10)] 2019 IEEE Transportation Electrification Conference and Expo, Asia-Pacific (ITEC Asia-Pacific) - Optimal scheduling of critical peak pricing considering photovoltaic generation and electric vehicle load
摘要： For long-wavelength space-based radars, such as the P-band radar on the recently selected European Space Agency BIOMASS mission, system distortions (crosstalk and channel imbalance), Faraday rotation, and system noise all combine to degrade the measurements. A first-order analysis of these effects on the measurements of the polarimetric scattering matrix is used to derive differentiable expressions for the errors in the polarimetric backscattering coefficients in the presence of Faraday rotation. Both the amplitudes and phases of the distortion terms are shown to be important in determining the errors and their maximum values. Exact simulations confirm the accuracy and predictions of the first-order analysis. Under an assumed power-law relation between σhv and the biomass, the system distortions and noise are converted into biomass estimation errors, and it is shown that the magnitude of the deviation of the channel imbalance from unity must be 4–5 dB less than the crosstalk, or it will dominate the error in the biomass. For uncalibrated data and midrange values of biomass, the crosstalk must be less than ?24 dB if the maximum possible error in the biomass is to be within 20% of its true value. A less stringent condition applies if the amplitudes and phases of the distortion terms are considered random since errors near the maximum possible are very unlikely. For lower values of the biomass, the noise becomes increasingly important because the σhv signal-to-noise ratio is smaller.
关键词： Biomass,Faraday rotation,polarimetric measurements,system distortion,calibration,long-wavelength radar
更新于2025-09-23 15:19:57
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Modal Analysis of 2-D Material-based Plasmonic Waveguides by Mixed Spectral Element Method with Equivalent Boundary Condition
摘要： For long-wavelength space-based radars, such as the P-band radar on the recently selected European Space Agency BIOMASS mission, system distortions (crosstalk and channel imbalance), Faraday rotation, and system noise all combine to degrade the measurements. A first-order analysis of these effects on the measurements of the polarimetric scattering matrix is used to derive differentiable expressions for the errors in the polarimetric backscattering coefficients in the presence of Faraday rotation. Both the amplitudes and phases of the distortion terms are shown to be important in determining the errors and their maximum values. Exact simulations confirm the accuracy and predictions of the first-order analysis. Under an assumed power-law relation between σhv and the biomass, the system distortions and noise are converted into biomass estimation errors, and it is shown that the magnitude of the deviation of the channel imbalance from unity must be 4–5 dB less than the crosstalk, or it will dominate the error in the biomass. For uncalibrated data and midrange values of biomass, the crosstalk must be less than ?24 dB if the maximum possible error in the biomass is to be within 20% of its true value. A less stringent condition applies if the amplitudes and phases of the distortion terms are considered random since errors near the maximum possible are very unlikely. For lower values of the biomass, the noise becomes increasingly important because the σhv signal-to-noise ratio is smaller.
关键词： Biomass,Faraday rotation,polarimetric measurements,system distortion,calibration,long-wavelength radar
更新于2025-09-23 15:19:57
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Real-Time Weld Quality Prediction Using a Laser Vision Sensor in a Lap Fillet Joint during Gas Metal Arc Welding
摘要： Nondestructive test (NDT) technology is required in the gas metal arc (GMA) welding process to secure weld robustness and to monitor the welding quality in real-time. In this study, a laser vision sensor (LVS) is designed and fabricated, and an image processing algorithm is developed and implemented to extract precise laser lines on tested welds. A camera calibration method based on a gyro sensor is used to cope with the complex motion of the welding robot. Data are obtained based on GMA welding experiments at various welding conditions for the estimation of quality prediction models. Deep neural network (DNN) models are developed based on external bead shapes and welding conditions to predict the internal bead shapes and the tensile strengths of welded joints.
关键词： deep neural network,camera calibration,laser vision sensor,gas metal arc welding,weld quality prediction
更新于2025-09-23 15:19:57