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- 摘要
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- 实验方案
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Fiber Bragg Gratings Sensors for Aircraft Wing Shape Measurement: Recent Applications and Technical Analysis
摘要： The safety monitoring and tracking of aircraft is becoming more and more important. Under aerodynamic loading, the aircraft wing will produce large bending and torsional deformation, which seriously affects the safety of aircraft. The variation of load on the aircraft wing directly affects the ground observation performance of the aircraft baseline. To compensate for baseline deformations caused by wing deformations, it is necessary to accurately obtain the deformation of the wing shape. The traditional aircraft wing shape measurement methods cannot meet the requirements of small size, light weight, low cost, anti-electromagnetic interference, and adapting to complex environment at the same time, the fiber optic sensing technology for aircraft wing shape measurement has been gradually proved to be a real time and online dynamic measurement method with many excellent characteristics. The principle technical characteristics and bonding technology of fiber Bragg grating sensors (FBGs) are reviewed in this paper. The advantages and disadvantages of other measurement methods are compared and analyzed and the application status of FBG sensing technology for aircraft wing shape measurement is emphatically analyzed. Finally, comprehensive suggestions for improving the accuracy of aircraft wing shape measurement based on FBG sensing technology is put forward.
关键词： accuracy,aircraft,FBGs,wing shape measurement
更新于2025-09-23 15:22:29
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A fast reconstruction method for three-dimensional shape measurement using dual-frequency grating projection and phase-to-height lookup table
摘要： Phase-to-height mapping is indispensable part of three-dimensional (3D) shape measurement system based on phase analysis, which guarantees the accuracy of 3D reconstruction. In this paper, a fast 3D shape reconstruction method based on dual-frequency grating projection and phase-to-height lookup table is proposed. In this proposed method, the reference plane is moved with known interval along the measurement depth direction to establish the mapping lookup table between the phase of the high and low frequency projected grating and their corresponding spatial height pixel by pixel respectively. Then, two methods to establish the lookup table with the unwrapped and the wrapped phase have been respectively introduced according to the characteristics of dual-frequency grating. The actual experimental results show that the two methods can effectively extend the measurement range of the current wrapped phase-to-height lookup method, and the reconstruction accuracy is better than the traditional phase-to-height quadratic fitting method. At the same time, the consumed time for 3D shape reconstruction of the tested object by the two methods is compared and analyzed. Finally, combining the high performance parallel computation of GPU, the fast 3D shape reconstruction is realized with the speed of 60fps.
关键词： Dual-frequency grating,Parallel computing,3D shape measurement,Multi-reference plane,Phase-to-height mapping
更新于2025-09-23 15:22:29
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[IEEE 2018 5th IEEE International Workshop on Metrology for AeroSpace (MetroAeroSpace) - Rome, Italy (2018.6.20-2018.6.22)] 2018 5th IEEE International Workshop on Metrology for AeroSpace (MetroAeroSpace) - Shape Measurement of Large Structures in Space: Experiments
摘要： A method to reconstruct the shape of a large planar structure in space is introduced and demonstrated through a lab-scale experiment. Lightweight sun sensors are distributed on the structure to measure local angles relative to the sun. The methodology to integrate the measured angles into the shape of the structure, based on a decomposition of the shape into basis functions is introduced. This methodology has been implemented on a lab-scale experiment. The design of the sensors is based on a 4 pixel pinhole camera. The calibration method for these sensors is presented as well as the techniques to integrate and communicate with them. A 1.2 m by 20 cm structure was designed and populated with sensors to show the performance of an integrated system. Preliminary results show an accuracy of 1 mm RMS on the shape reconstruction of this structure.
关键词： reconstruction,shape,measurement,sensor,sun,solar,laboratory,experiment,structure,sail,antenna array
更新于2025-09-23 15:22:29
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Handheld pocket-size Fourier transform profilometry using projector-enabled smartphone
摘要： Surface Fourier transform profilometry (FTP) is a technique used for reconstructing three-dimensional (3-D) surface topography using light. It has been widely used in machine vision for biomedical and biometric automations, providing solutions beyond conventional 2-D imaging. This paper proposes an implementation of the handheld pocket-size FTP for 3-D surface profile imaging using a projector-enabled Samsung Galaxy Beam smartphone. In the implementation, a crossed-optical-axes geometry of the FTP is formed by using a mirror positioned over the phone’s projector via an adjustable tilt mounting bracket. Experimental proof-of-concept of the proposed profilometry is done by implementing conventional and non-phase shifting FTPs with different diffuse test objects. The experimental results obtained by using the non-phase shifting technique are in good agreement with those of the direct contact measurement. Besides having superiority of compactness, the proposed profilometry paves the way for the development of real-time 3-D profiling and printing through internet or Bluetooth interconnection.
关键词： 3-D profilometry,non-phase shifting technique,contrast function,sinusoidal grating,projector-enabled smartphone,3-D surface topography,Samsung galaxy beam,Fourier transform,shape measurement
更新于2025-09-23 15:21:01
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Deep-learning-enabled geometric constraints and phase unwrapping for single-shot absolute 3D shape measurement
摘要： Fringe projection profilometry (FPP) has become a more prevalently adopted technique in intelligent manufacturing, defect detection, and some other important applications. In FPP, efficiently recovering the absolute phase has always been a great challenge. The stereo phase unwrapping (SPU) technologies based on geometric constraints can eliminate phase ambiguity without projecting any additional patterns, which maximizes the efficiency of the retrieval of the absolute phase. Inspired by recent successes of deep learning for phase analysis, we demonstrate that deep learning can be an effective tool that organically unifies phase retrieval, geometric constraints, and phase unwrapping into a comprehensive framework. Driven by extensive training datasets, the neural network can gradually “learn” to transfer one high-frequency fringe pattern into the “physically meaningful” and “most likely” absolute phase, instead of “step by step” as in conventional approaches. Based on the properly trained framework, high-quality phase retrieval and robust phase ambiguity removal can be achieved only on a single-frame projection. Experimental results demonstrate that compared with traditional SPU, our method can more efficiently and stably unwrap the phase of dense fringe images in a larger measurement volume with fewer camera views. Limitations about the proposed approach are also discussed. We believe that the proposed approach represents an important step forward in high-speed, high-accuracy, motion-artifacts-free absolute 3D shape measurement for complicated objects from a single fringe pattern.
关键词： Deep learning,Phase unwrapping,Fringe projection profilometry,Geometric constraints,Single-shot absolute 3D shape measurement
更新于2025-09-23 15:21:01
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[IEEE 2018 2nd European Conference on Electrical Engineering and Computer Science (EECS) - Bern, Switzerland (2018.12.20-2018.12.22)] 2018 2nd European Conference on Electrical Engineering and Computer Science (EECS) - An Extraction Method for the Parameters of the Solar Cell Single-Diode-Model
摘要： To satisfy the requirement of high wireless transmission rate from user terminals, the multi-cell cooperative communication is an important solution for cellular networks. The selection of cooperative cells is usually depended on every wireless single cellular coverage boundary in cellular networks. In this paper, we analyze the characteristics of wireless single cellular coverage boundary based on real measured data. Moreover, the alpha-stable processes are first proposed to model the wireless single cellular coverage boundary. Simulation results indicate that probability density functions of wireless single cellular coverage boundary can be fitted by alpha-stable processes with 95% confidence interval based on the real measured data. This result provides a basis for cooperative communications considering the anisotropic fading characteristic of wireless signal propagation in wireless single cellular coverage region.
关键词： channel estimation,Cellular networks,wireless communication,shape measurement
更新于2025-09-23 15:19:57
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High-speed 3D shape measurement using Fourier transform and stereo vision
摘要： Background: In the fast 3D shape measurement, it is an important factor to use the least number of fringe patterns to get the wrapped phase and the wrapped phase is always required to be retrieved to absolute phase. But the process of phase unwrapping may affect the quality of absolute phase. Besides absolute phase retrieval is time-costing especially for high-speed 3D shape measurement. Methods: This paper proposes a fast measurement method based on Fourier transform profilometry and stereo vision. Because of the property of stereo vision, every point can find its corresponding point in the wrapped phase. This method can reconstruct 3D surface without phase unwrapping. In order to further increase the measurement speed and overcome the gamma effect of projector, the dithering fringe pattern is used. To resist false matching, the original image matching constraint gives a rough parallax. Phase matching and sub-pixel parallax optimization are used to reduce the matching errors. In order to confirm the phase value of points which are at the edge of wrapped phase, average phase value is calculated. Results: A white mask is measured based on the proposed method. The results from every step show the effect of different functions. To better show the effect of the proposed method, a white house is measured and the measurement is compared with LSSM and MFH. In order to further to show the advantage of the proposed method, discontinuous blocks and continuous blocks are measured. The average height, RMS, average error, maximum error are compared with the method which uses absolute phase to match the corresponding points. Experiment results verify the feasibility of the proposed method and it can measure complex objects with high speed and accuracy. Conclusion: This paper uses Fourier transform and stereo vision to get wrapped phase and reconstruct 3D shape without phase unwrapping. The proposed method contains three part: phase matching, edge points detection and sub-pixel parallax optimization. By comparing matching precision, the proposed method can get high quality surface. Because the process of measurement only need one frame of deformed fringe pattern to get the wrapped phase and the matching process does not need phase unwrapping, the proposed method has the potential to be used in fast measurement.
关键词： Fourier transform,Three-dimensional shape measurement,Stereo vision,Fringe analysis
更新于2025-09-19 17:15:36
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Polarization-Insensitive Laser Scanning and Profiling using Amplitude-Modulated CW Scheme
摘要： Laser scanners have emerged as powerful instrument for high-precision 3D geometry measurement. However, such attractive laser scanners have failed to address to drop of receiving power due to laser’s interaction with the surface of the object under measurement. This is a serious weakness of laser scanning systems since it can result in data deterioration and data loss in the acquired 3D point clouds. Numerous studies have been carried out on laser illumination on rough surfaces and have shown that interference between backscattered lights within the laser beam spot forms speckles which affect the level of the receiving power. In this article, we propose a laser scanner having a rapid and continuous polarization scrambling function and cope with the drop in the receiving power. This is the first report of speckle reduction with depolarization approach for laser scanning used for industrial measurement.
关键词： Interference,Optical polarization,Shape measurement,Laser radar,Surface roughness
更新于2025-09-19 17:13:59
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Dual-beam interferometric particle imaging for size and shape characterization of irregular coal micro-particle: validation with digital inline holography
摘要： The size and shape characterization of irregular particles is of great significance in the comprehensive understanding of many natural and industrial processes. The dual-beam interferometric particle imaging (DIPI) technique is adapted from a dual-beam backward illumination configuration of interferometric particle imaging to access the size and 2D shape of an irregular particle from its interferogram. An experimental setup combining the digital inline holography (DIH) and DIPI techniques characterizes the same projection of the same particle with a color camera, permitting the accuracy evaluation and validation between these two techniques. The comparison results show a good agreement between the 2D-Fourier transform of DIPI interferogram and the 2D-autocorrelation of DIH reconstructed in-focus image. The DIH gives the reference result for the size measurement of the particles, and we observe a maximum difference as low as 9% with the DIPI measurement. The backward arrangement of the dual-beam interferometric particle imaging technique facilitates its further instrumental development and application to a variety of real circumstances, e.g., solid fuel particles and ice crystals.
关键词： Irregular particle,Size,Holography,Shape measurement,Interferometric particle imaging
更新于2025-09-11 14:15:04