摘要:To realize accurate phase measurements of a laser, a laser phase demodulation system based on 3×3 polarization maintaining (PM) fiber coupler was proposed and demonstrated. The two output signals of the 3×3 PM fiber coupler were converted to electrical signals through photoelectric conversion, and the phase information was obtained through a phase demodulation calculation based on differential cross multiplication. Through adoption of the 3×3 PM fiber coupler and PM delayed fiber structure, the Faraday rota
摘要:The Fengyun 3D satellite is a second-generation polar orbit meteorological satellite that was launched by China on November 15th, 2017, with a novel High-Spectral Resolution Infrared Atmospheric Sounder (HIRAS), aiming to provide hyperspectral infrared observations. The infrared high-spectral sounder needs to perform spectral calibration for each channel owing to the direct influence of spectral frequency accuracy on radiometric calibration results. First, a rough spectral calibration result was obtained by
摘要:Cover glass used in photovoltaic panels plays an important role in light harvesting and in turn panel performance. In this paper, the effects on panel performance of surface antireflection (AR) coating and of micropatterns on cover glass were systematically studied by ray tracing simulation. It was found that inner surface patterns of glass have negligible effects on the optical and electrical properties of panels. Both AR film and front surface patterns benefit panel performances. A 45° pyramidal pattern i
关键词:photovoltaic panels;cover glass;surface pattern;antireflection coating;equivalent photon current density
摘要:To fulfill the requirements of small volume, low cost, anti-interference ability, high sensitivity, and real-time and accurate temperature measurement in a complex environment, a double Fabry-Pérot (F-P) fiber optical temperature sensor based on end-face corrosion was proposed. The sensor was fabricated by fusion Endlessly Photonic Crystal Fiber (EPCF) with a Multi-Mode Fiber (MMF). There are three F-P reflectors: one between the Single-Mode Fiber(SMF) and EPCF, one between EPCF and MMF, and one at the inte
摘要:A station-transfer model was established in this study to improve the accuracy of laser tracker station-transfer measurement in larger-scale metrology. The accuracy of the laser tracker is related to the measurement errors, such as random and system measurement errors. First, the source and precise form of measurement error of the laser tracker system was analyzed according to the measurement principle of the laser tracker. Moreover, a spatial point measurement model containing the laser tracker measurement
关键词:large-scale metrology;laser tracker;random measurement error;systematic measurement error;station-transfer error;Monte Carlo simulation
摘要:A reasonable recording distance sets the premise to obtain a reconstructed image with no overlap and high-quality pre-magnification digital holography. Herein, a comprehensive analysis and design of the recording distance were proposed, which combines the conditions of recording and numerical reconstruction. In addition, not only were the sampling theorem and the spectrum separation theorem considered, but the relationship between the sizes of reconstructed and amplified images, and the sampling requirement
关键词:digital holography;recording distance;reconstructed image;amplified image;optical transfer function
摘要:To improve the mechanical properties of an aluminum alloy surface, high-purity Cr, Fe, Co, Ni, and Cu powders were laser deposited on the alloy by using a coaxial powder feeder to form an AlCrFeCoNiCu High-Entropy Alloy (HEA) coating. With laser power, scanning speed, and powder feeding rate selected as the factors and the wetting angle and dilution taken as the responses, a multi-objective optimization of the process parameters of laser deposition was conducted by combining the Taguchi method and the techn
摘要:In this study, a wave 3-RPS/3n-SPS parallel mechanism with redundant limbs was proposed. To solve the inverse dynamics of the mechanism, the kinematics of the mechanism were first analyzed. The velocity and acceleration mapping relationships between the branch chains and center of the moving platform were established. Then, the kinematics model was verified by simulation, and a force analysis of the 3-RPS/3n-SPS mechanism was performed. Dynamics supplementary equations were constructed based on the coordina
摘要:In order to produce transparent glass heaters with high light transmittance, conductivity, and adhesion of the heating wire, a novel method that combines the advantages of electric-field-driven melt-jet-deposition 3D printing technology and UV-assisted micro-transfer technology was developed. This method can enable the low-cost, batch-based manufacture of high-performance glass heaters. First, the material for 3D printing, media for the UV-assisted micro-transfer and material for the heating wire were selec
关键词:transparent glass heater;composite manufacturing;electric-field-driven-melt-jet deposition 3D printing;UV-assisted micro-transfer
摘要:A bidirectional piezoelectric linear actuator was proposed to solve the issue of the piezoelectric linear actuator being incapable of functioning under tension and pressure load. The actuator mainly adopted the principle of the two-way screw clamping to realize two-way large-thrust actuation. Structurally, the two piezoelectric stacks were symmetrically arranged, and the trapezoidal screw nut constituted a screw clamp. By matching the driving timing of the piezoelectric stack and screw clamp, the actuator c
关键词:piezoelectric linear actuator;large thrust;piezoelectric stack;screw clamp;inchworm
摘要:A novel MEMS capacitive vibrating ring gyroscope was proposed in this paper based on the advantageous of the ring gyroscope: symmetric resonator, identical mode parameters and excellent anti-interference ability. The sensitive structure of silicon-based capacitive vibrating ring gyroscope with S-shaped elastic supporting beams was designed, and the operating mode and amplitude-frequency response characteristics of the gyroscope were simulated and analyzed. The electromechanical interface and the silicon ele
关键词:Micro-electro-mechanical System(MEMS);vibrating ring gyroscope;sensitive structure;capacitor electrode;manufacturing process
摘要:Due to the advantages of compact structure and large displacement amplification ratio, compliant bridge-type displacement amplification mechanism (DAM) has increasingly gained attention in the field of precision engineering. In previous reports, the design and analysis of bridge-type DAM have been limited to the linear range. In this work, nonlinear modeling and optimization of a typical lumped bridge-type DAM were investigated. Considering the shearing effect and geometrical nonlinearity, the output-input
摘要:To improve the stability and measurement accuracy of the positioning system of a metrological scanning electron microscope, the mechanical displacement platform in the positioning system was simulated and analyzed, and vibration parameter values were obtained. A model of the mechanical displacement platform was established according to its working conditions, and the structural vibration parameter values of the platform were acquired by conducting static and modal analysis using the finite element method. T
关键词:metrological scanning electron microscope;micro-displacement platform;vibration;coupling displacement;finite element analysis
摘要:Coupling moments and nonlinear transmission torques are the main factors that influence the precise angular speed control for a gimbal system of double-gimbal magnetically suspended control moment gyro with harmonic drives. Therefore, a composite decoupling control method based on a disturbance observer and adaptive backstepping control was presented to address this problem and to achieve high precision angular speed servo control of the gimbal system. Disturbances were estimated by the designed disturbance
关键词:Double-Gimbals Magnetically Suspended Control Moment Gyro (DGMSCMG);gimbal system angular speed servo control;harmonic drive;disturbance observer;adaptive backstepping
摘要:Aiming at the problem that the chatter of the Three-Dimensional Elliptical Vibration Cutting (3D-EVC) will reduce the quality of optical components. Therefore, the chatter phenomenon in 3D-EVC process need be suppressed. The chatter problem can be regarded as an optimization problem of cutting parameters. In other words, an intelligent optimization algorithm must be used to obtain the optimal cutting parameters to meet the requirements of the chatter suppression parameters. Therefore, a Particle-Artificial
摘要:To improve the accuracy and anti-interference of the position detection of a linear motor mover from a target shooting source, an aperiodic sinusoidal stripe image was constructed and a sub-pixel measurement method based on the gradient method was introduced to achieve high-precision measurement of the mover position. First, by changing the stripe cycle of the sinusoidal stripe, an aperiodic sinusoidal stripe image was generated. Second, an aperiodic sinusoidal stripe image with strong robustness was selected by using the Pnatt entropy of the image. Finally, the subpixel displacement of the adjacent target image was calculated using the gradient method based on the Barron operator, and the actual displacement of the linear motor mover was obtained by combining the calibration coefficients of the calibration system. Simulation and experimental results show that when compared to the aperiodic fence image, the aperiodic sinusoidal stripe image has strong robustness and a measurement accuracy of 0.02 pixels.
摘要:To achieve a multi-structure parameter design and optimization based on the sensitivity index of a washer-type piezoelectric six-axis force sensor, an analytical mathematical model of the static sensitivity of the sensor must be studied. First, the structural characteristics and working principle of the sensor are analyzed, and a static sensitivity analytical mathematical model is derived based on the load transfer path inside the sensor. Then, an analytical mathematical model and a mathematical model based
关键词:six-axis force sensor;sensitivity;analytic mathematical model;orthogonal experiment
摘要:To achieve tracking of marine vessel targets and improve maritime intelligence monitoring levels, this study proposed a target tracking algorithm with improved kernelized correlation filters (KCF). First, per the characteristics of a KCF algorithm, the concept of ship target tracking critical probability was proposed for evaluating whether target tracking was abnormal. A Kalman filter module was added to the algorithm to predict the position of the tracking target at the next moment. A target tracking excep
摘要:To reduce noise in the output of a low-cost Micro-Electro-Mechanical System (MEMS) gyroscope, an Empirical Mode Decomposition (EMD) fuzzy interval threshold denoising method was proposed. The signal was first decomposed into multiple eigenmode functions/intrinsic mode functions (IMFs) using EMD. Then the IMFs were classified into three categories in terms of their IMF characteristics: noise dominated IMF, mixed noise and information IMF, information-dominated IMF. For the mixed noise and information IMF, th
摘要:To recognize minor defect echoes from metallic material ultrasonic testing signals, the recurrence analysis method was used to analyze ultrasonic detecting signals. By modeling the backscattering signal, we describe its components. In the ultrasonic detection signal, the defect echo signal will affect the recurrence characteristics of the system. In this study, we employ the recurrence analysis method to study the backscattering defect and defect-free signals of a low carbon steel testing specimen with a di
摘要:Previous studies have used signal-to-background ratio in spectroscopy to address the lack of physical quantities that describe target signal saliency in image processing. Similar to the signal-to-noise ratio calculation method, the ratio of the average gray value of the target signal to the average gray value of the background was obtained, therefore, the contrast between the target signal and the background was visually demonstrated. However, a video enhancement method was proposed for low-speed dim target
关键词:image processing;signal-to-background ratio;target enhancement;low-speed dim targets
摘要:For each point of the surface obtained from organized point cloud, the normal can be estimated by fitting a local surface approximation to the surface local sample. However, for a surface sample with defects, it is difficult to robustly approximate the local area. Therefore, it is difficult to accurately estimate the normal of the sample points. To suppress the influence of sample defects on the normal estimation of sample points, a weighted normal estimation algorithm was presented for sample points, which
关键词:robust normal estimation;bounded Poisson surface;surface local sample;vertex normal estimation;gain optimization
摘要:Recognizing facial expressions in video sequences is challenging because of the difficulty in distinguishing between hand-crafted features and subjective emotions. To solve this problem, we aim to improve the performance of facial expression recognition in videos. Our method used two deep convolutional neural networks (DCNNs) (i.e., spatial and temporal convolutional neural networks) to learn the temporal-spatial expression features in videos. The spatial convolutional neural network was used to extract the spatial features of static expression images from each video frame, where as the temporal convolutional neural network was used to extract dynamic features from optical flow information hidden in multi-frame expression images of a video. The temporal-spatial features were then fused using a deep belief network. Finally, support vector machines were employed to perform facial expression classification. Based on experimental results on public RML and BAUM-1s video-based emotional datasets, our method achieved an accuracy of 71.06% and 52.18%, respectively, which is clearly better than the results of existing studies. This study thus showed that our multimodal DCNN can improve the performance of facial expression recognition in videos.
摘要:In additive manufacturing, reverse engineering, and other fields, many triangular mesh models were used to process big data. To facilitate storage and improve processing efficiency, simplifying the mesh model was necessary. However, conflicts existed among feature preservation, simplification rate, and simplification efficiency in mesh simplification. For improved balancing of results and efficiency of simplification, a method based on curvedness was proposed to compute new vertices more precisely. In addit
摘要:On-orbit calibration of camera parameters is a key step in the process of enhancing positioning accuracy without the need of ground control points. Triangulation-based bundle adjustment is an efficient method for calibrating the geometric parameters of a camera by incorporating stereo imagery. However, it is necessary that the established strip model should not cause system deformation owing to the rate of attitude variation. In this study, characteristics of the payloads present in the TH-1 satellite were
摘要:Future video coding considerably improves compression efficiency over that of the previous high-efficiency video coding standard. The quadtree plus binary tree structure of future video coding is more consistent with the texture of high-definition video but at the cost of tremendous computational complexity. In this study, a joint multi-feature classification algorithm was proposed to reduce the complexity of the quadtree plus binary tree block structure in future video coding. The partition mode of the cur
关键词:future video coding;joint multi-feature classification algorithm;quadtree plus binary tree block structure;fast coding technique