Chinese Version Light学术出版中心
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Issue 6 ， 2015
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Strain transfer errors of optical fiber sensors embedded in asphalt pavement
Abstract：Strain transfer theory for optical fiber sensing was introduced, and the quantitative relationship of strains between host material and optical fiber was set up to eliminate the strain transfer errors and to improve the testing precision on the basis of the strain transfer theory. A typical three-layered structural model containing a sensing optical fiber, a package layer and a host was established for the application of an optical fiber sensor embedded in asphalt pavement. The Goodman's hypothesis was introduced to describe the relationship of interfacial shear stresses between layers, and the Fourier series was adopted to solve the differential equation and to establish the average strain transfer relationship between host material and optical fiber. The effectiveness of the formula of strain transfer theory derived by this paper was validated experimentally. Moreover, the sensitivity of related geometrical and physical parameters effecting on the average strain transfer efficiency was discussed. The analytical results indicate that average strain transfer coefficient increases with the growth of sensing length and the interfacial adhesion coefficient between optical fiber and protective layer. The work in this paper could be widely used for the modification of strain transfer errors and the design of embedded optical fiber sensors.Keywords：embedded optical fiber sensor;optical fiber sensing strain;strain transfer error;length of fiber adhesion;optical fiber packaging- 64
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Published：2020-08-13 -
Doppler spectrum imaging of vibrating target using laser heterodyne detection
Abstract：To recognize the profile of a vibrating target, the Doppler spectral image of the target was captured by using the laser heterodyne detection method. A photo-current model of laser heterodyne signal from the vibrating target was derived based on the instant changing of phase, the target was scanned point by point in the laser direction controlled by a scanning galvanometer, and the data collection was synchro-controlled by the drive voltage of the galvanometer to synchronize data scanning and data capturing. A method called the Ratio in Broaden Spectrum (RIBS) to vibration signal processing was proposed to process the Doppler spectrum come from the vibration signal, by which the data processing was simplified and the effect of peak noise on the signal was eliminated. The characteristic spectra of two targets in different positions were detected at a 5 MHz sampling rate in the experiment to derive the RIBS curve, and Doppler spectrum imaging was captured with different RIBS, which show that when the optimal ratio is set from 0.7 to 0.9, the high quality vibration image can be obtained. The result demonstrates the validity of the RIBS in vibrating target detection and the feasibility of the laser heterodyne detection to capture spectrum images.Keywords：laser heterodyne detection;vibrating target detection;Doppler spectrum imaging;target recognition- 91
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Published：2020-08-13 -
Preparation and properties of ITO/Ag photonic crystal thin films
Abstract：As the shielding effectiveness and light transmittance of materials are conflict, this paper designs transparent shielding films based on the metallic photonic crystals with a period of Silver/Indium Tin Oxide(Ag/ITO) to realize the compatibility of the shielding effectiveness and the light transmittance. The composition of the photonic crystals was optimized and their properties were researched. Then, ITO/Ag periodic films were prepared by magnetron sputtering. Furthermore, the shielding, transmittance and electric conductivity of different structures were analyzed and tested. It is found that the maximum transmittance of the ITO/Ag periodic films at the visible band is up to 55% when the total thickness of Ag films is far more than optical skin depth and the maximum shielding of the ITO/Ag periodic films at microwave frequencies is up to 65 dB when the total thickness of Ag films is far less than the microwave skin depth. By structure design, the visible light transmittance curve of the samples is coincided with the human eye sensitivity curves. The square resistance decreases with each period of Ag film thickness increasing, correspondingly, the shielding increases. Moreover, the transmittance of the films does not decrease with numbers of periods and the shielding is not obviously changed. It realizes that the shielding is greater than 40 dB in the 30 MHz—18 GHz frequency ranges. The method proposed provides a new compatible approach to electromagnetic shielding and visible light transparent.Keywords：photonic crystal;photonic crystal thin film;ITO/Ag thin film;electromagnetic shielding;transparent metal- 56
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Published：2020-08-13 -
High precision measurement for barrage weapon dispersion based on large area triangle composite light-screens
Abstract：A high precision laser screen dispersion measurement method based on a large area triangle light-screen composite was presented to solve the difficulty of location dispersion test for super-high firing rate barrage weapons. A design scheme for large area triangle photoelectric switch system composed by a laser, a laser beam shaping system and a laser detector array was given, the measuring principle of double large area triangle light-screens was analyzed, and an algorithm for triangle light-screen impact point coordinates was derived. By combining with the output characteristics of the detection device in the system, the algorithm error was analyzed. The analysis results show that maximum theoretical error increases by 0.275 mm, from 0.557 mm to 0.832 mm when the width of regular target area increases from 3.6 m to 10 m. The results of the test show that when the resolution of detector array is 1.6 m, the maximum X error of output coordinates is 0.747 mm, and the maximum Y error of output coordinates is 0.635 mm, which shows a high precision measurement for the location dispersion of super-high firing rate barrage weapons. This measurement method is characterized by a larger screen area, higher test precision and easy to install and debug.Keywords：laser measurement;triangle composite light-screen;barrage weapon;impact point coordinate algorithm;barrage weapon dispersion- 77
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Published：2020-08-13 -
Nondestructive detection on firmness of peaches based on hyperspectral imaging and artificial neural networks
Abstract：To explore a nondestructive method to measure peach internal quality, a hyperspectral imaging technology combined with Artificial Neural Networks (ANN) was applied to evaluate the firmness of intact peaches. The hyperspectral images of 140 peaches during 12 day storage were acquired from 900 nm to 1 700 nm, and the average reflective spectrum of interest region of 40 pixel×40 pixel in each image was calculated and was used as the original spectra. The spectra were preprocessed by Savitzky-Golay smoothing and the standard normal variate. The sample set was partitioned based on joint x-y into calibration sets (105) and prediction sets (35). Then the successive projection algorithm, uninformative variable elimination method and competitive adaptive reweighted sampling method were used to select characteristic wavelengths by 12, 103 and 22 from 216 wavelengths, respectively. A support vector machine and an error back propagation (BP) network model were established based on full spectra and selected characteristic wavelengths for predicting the firmness of intact peaches. The result shows that BP model based on full spectra has the best prediction performance with a correlation coefficient and a root-mean-square error of 0.856 and 0.931, respectively. This study offers the base for identifying internal qualities of peaches in industry.Keywords：hyperspectral imaging;peach;firmness;nondestructive detection;BP network;support vector machine- 47
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Published：2020-08-13 -
Evaluation of Φ400 mm instantaneous wavefront using grating point diffraction interferometry
Abstract：A method to measure Φ400 mm instantaneous wavefront based on grating point diffraction interferometry was proposed. The method introduced the lateral displacement into the test wavefront and reference wavefront by applying a phase grating, which means that a linear carrier was introduced in an interferogram. Then, the test wavefront was retrieved by Fourier Transform(FT). On the basis of scalar diffraction theory and Fourier optics theory, a theoretical model of instantaneous wavefront was established and the formula of linear carrier was derived. Furthermore, the effects of energy reducing and aperture angle changing due to pinhole diffraction were studied by using Kirchhoff formula, then the formula of grating etched depth was derived. An experimental installation of Φ400 mm instantaneous wavefront testing was set up and the interferogram with high modulation and a linear carrier was acquired. The FT method was applied to the restoration of the interferogram. The results indicate that the root mean square value of tested wavefront is 0.105λ, which is in accord with that of 0.101λ acquired by a SID-4 wavefront sensor. It concludes that the measurement of Φ400 mm instantaneous wavefront has been realized by this method.Keywords：optical testing;wavefront evaluation;instantaneous wavefront;grating point diffraction interferometry;linear carrier- 54
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Published：2020-08-13 -
Measurement of mid-infrared total atmospheric transmittance and its error analysis
Abstract：To measure the mid-infrared total atmospheric transmittance in a field and to improve the measuring accuracy of infrared radiation of spatial objects, a measuring method based on standard infrared stars was discussed. A mathematical model based on Beer's law and Langley-Plot calibration principle was established, and an experimental system based on the ground-based optic-electric telescope with an aperture of 1.2 m was set up. Then,“Quasi-real-time One-point Correction Method”, “Window-extracted Method” and “SNR Characteristic Curve” were employed to reduce the effects of the non-uniformity of detectors and the diffusion imaging of stars on the measuring accuracy. Finally,the error of the measurement in the experiments was analyzed.Experiments and analysis show that the maximum measuring error of the infrared radiation illumination of spatial objects is 16.28%, and the theoretical measuring error of mid-infrared total atmospheric transmittance is 11.75%.The results indicate that the measuring method proposed in this pape has a smaller measuring error, the experimental system is adapt to observation missions in the field and it provides a new solution for measuring the infrared radiation of spatial objects.Keywords：atmospheric transmittance measurement;infrared radiation;space target;standard infrared star;large-aperture ground-based telescope- 56
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Published：2020-08-13 -
Optoelectronic aiming and orientation system of laser tracker
Abstract：As the optoelectronic aiming and orientation of an optoelectronic tracker effect directly the overall measurement accuracy and operational performance of instruments, this paper proposes an improved design scheme. Firstly, the optoelectronic aiming and orientation control technology of the laser tracker was analyzed, and a systemic technological scheme for optoelectronic detection and aiming, signal regulate acquisition, digital signal processing and intelligent tracking servo was proposed. The key components in the system were selected, and the detection optical path and signal processing circuit were designed by using a cube-corner prism and a Position Sensing Detector(PSD) as the photoelectric detecting core. Then, a system prototype was developed and a standard test platform for target displacement was established to test the detecting signals of photoelectronic aiming system in the prototype. The tested results demonstrate that the proposed system performance index has achieved, in which the static precision of the position measurement is up to 6 μm, and the stochastic dynamic tracking measurement speed is greater than 1 m/s. It shows that the proposed method improves orientation accuracy and tracking effect of the laser tracker and provides reference for development of measurement instruments with high accuracy and large-scale fields.Keywords：laser tracker;optoelectronic aiming;optoelectronic tracking;orientation system;Position sensitive detector;signal processing- 77
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Published：2020-08-13 -
Effect of feeding speed on micro-hole drilling in TiC ceramic by femtosecond laser
Abstract：By spiral drilling hole technology, micro-holes were drilled at different feeding speeds in TiC ceramic. The morphologic features of micro-holes were examined by scanning electron microscope, the elemental compositions for untreated specimens and laser-treated areas were identified by using an energy dispersive spectroscopy and the chemical bonds for untreated specimens and laser-treated debris were analyzed by an X-ray photoelectron spectroscopy. Then, the mechanism of interaction between femtosecond laser and TiC was further discussed. The results indicate that the drilled micro-holes show a good morphology without visible microcracks in ablated areas. The roundness of entrance is above 98%, better than that of the exit. The diameter at entrance is slightly smaller than that of the diameter at exit. The feeding speed has an obvious effect on micro morphology of entrance. When the feeding speed is lower, the regular ripples are observed in ablated areas. With increasing feeding speed, the surface is characterized by sporadic particles. High oxygen content is detected in a deposited layer at low and high feeding speeds, respectively, and the optimum feeding speed is 6.4 μm/s in this research. Moreover, the machining mechanism could be explained by the multiphoton absorption theory. When the C-Ti bond is broken during machining, the titanium ion will combine with oxygen and the TiO2, Ti2O3 in debris will be generated.Keywords：femtosecond pulsed laser;micro-hole drilling;feeding speed;micro-hole morphology;TiC ceramic- 73
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Published：2020-08-13 -
Correction of removal function of ion beam figuring highly steep off-axis asphere
Abstract：The effect of curvature change of a mirror surface on the removal function of ion beam figuring was explored. A new higher precision figuring method for a highly steep off-axis asphere was proposed by using a correction matrix to calculate the removal function in different dwell points. The coordinate transformation for the off-axis asphere was used to decrease the effect of steep change on the removal function, the material removal rate of ion beam figuring asphere was analyzed based on Sigmund sputtering theory and a mathematics model of the removal function of the ion beam figuring asphere was established to calculate the variation of the material removal rate in different well points. The FWHMs (full wave and half maximum) of removal functions on different dwell points were calculated based on projection theory. Then the correction matrix for removal function was obtained based on the dwell point matrix, by which the information of removal function on every dwell points was calculated. Furthermore, the dwell time could be computed by Computer Controlled Optical Surfacing(CCOS) theory. At last, the experiments were performed by combing with a simulation. A silicon off-axis sphere mirror with a size of 900 mm×680 mm and an off-axis magnitude of 350 mm was figured. Obtained the RMS value of profile accuracy for the off-axis asphere mirror changes from 32.041 nm to 11.566 nm and the rate of convergence is up to 2.77. The experimental result demonstrates that the correction matrix for removal function of ion beam figuring satisfies the requirement of optical fabrication.Keywords：optical fabrication;off-axis asphere surface;ion beam figuring;sputtering theory;removal function- 71
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Published：2020-08-13 -
Analysis of human colonic motility using EEMD
Abstract：As current diagnostic methods for constipation are invasive and the diagnostic effects are not ideal, this paper researches how to use the noninvasive detection equipment to obtain the gastrointestinal physiological information. The nonlinear analysis methods were taken to analyze human colon dynamics and to find out the difference between normal people and constipated patients, then to provide references for clinical diagnosis of the constipation. Colonic pressure data from 8 healthy and 10 constipated subjects were analyzed. Firstly, the breathing, coughing, electromagnetic interference noise in the colonic pressure data were filtered by thresholds and the Ensemble Empirical Mode Decomposition (EEMD). Then, the colonic contractile frequency, motility index and the average peak of peristaltic wave were extracted to characterize the colonic dynamic properties. Finally, the feature parameters between healthy and constipated subjects were compared by using the t test. Analysis shows that the number of contractions and the motility indexes of healthy subjects are different from that of the patients with constipation (p <0.05), and they have statistically significance for distinguish the healthy subjects and the patients with constipation, but the average peak of peristaltic wave does not.So it suggests that the number of contractions and motility indexes could be used in the noninvasive detection for diagnostics of the healthy subjects and patients with the constipation.Keywords：wireless capsule;wireless sensor;slow transit constipation;human colonic motility;Ensemble Empirical Mode Decomposition(EEMD)- 41
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Published：2020-08-13 -
Comprehensive error modeling and compensation for optical free-form surface polishing machine tool
Abstract：To improve the machining accuracy of an optical free-form surface, an integrated error model for five-axis polishing machine tool was established based on multi-body system theory. The movement error and rotation error of every axis were measured and analyzed by direct and repetitive measurement model, and it shows that the feed speed and measurement spacing have no significant influence on the movement and rotation errors. By taking the error data into the integrated error model, the variation rule of movement and rotation errors which are the components in the three axes of x, y and z from the integrated error of polishing machine tool was obtained. According to the above analysis, the main influence factor of integrated error is linear displacement errors. The compensation experiment was conducted based on integrated error model. The linear displacement errors of the three axes of x, y and z have been compensated obviously and they are decreased by 88%, 89% and 84% respectively. The experiment results indicate that the integrated error model and compensation method have high accuracy and excellent robustness.Keywords：optical free-form surface;five-axis polishing machine;multi-body system;comprehensive error modeling;error compensation- 57
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Published：2020-08-13 -
Fabrication of polymer thin film resistors by a drop-on-demand technology
Abstract：This paper focuses on the fabrication of polymer thin film resistors by the digitalization of microfluids. A fabrication system with drop-on-demand(DOD) jetting for polymer thin film resistors was setup based on the digitalization of microfluids. The poly(3.4-ethylenedioxythiophene)/poly(styrenesulfonate)(PEDOT/PSS) was jetted on the Resin Coating(RC) paper substrate at the best overlap of 13.4%, the film consisting of polymer droplets was quickly dried by the capillary action of the paper to form a thin film resistor and the resistance value was reduced by annealing processing. The influences of the system parameters on the diameter of the droplets were researched. The thin film resistors with the resistances varied from 3.5 to 23.2 MΩ were obtained by changing the row number, column number, layer number and the annealing conditions. The results show that the resistance is almost proportional to the row number and decreases with the number of the rows and layers increases. Furthermore, the resistance of the printed thin film resistors has decreased by 10%—40% due to the annealing processing. With the same fabrication parameter and annealing condition, the thin film resistors show good uniformity. The resistance of the resistors decreases when the temperature increases and reaches a stable level. The experimental results indicate that the fabrication of the polymer thin film resistors based on the drop-on-demand technology has advantages on the simple process, low costs and good electrical properties.Keywords：polymer thin film resistor;microfluid digitalization;drop-on-demand;RC paper;overlap- 19
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Published：2020-08-13 -
Pressing-fitting technology and instrument for precision small parts
Abstract：According to the assembling demands of precise small parts with interference fitting, a precision pressing-fitting instrument for assembling small parts was developed. Through analyzing the relation of pressing-fitting force and the instrument's elastic deformation in pressing-fitting process, the parts' pressing-fitting displacement was compensated to increase assembly accuracy. A kind of machine vision device with upper and lower vision fields was used to detect relative situation of parts, and a XY displacement platform was used to align the positions of the parts. A calibration method of the machine vision device was proposed. The relation between pressing-fitting force and pressing-fitting displacement was analyzed, and the predicted values of force and displacement were proposed to judge the assembly rationality. Five kinds of parts obtained randomly was assembled. The experimental results show that pressing displacement-pressing force curve is consistent with the predicted values. The parts' relative position deviation is less than ±5 μm, and vertical deviation is less than 10 μm, which meets the requirements of the assembly accuracy index.Keywords：small part;interference fitting;pressing-fitting instrument;part alignment- 54
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Published：2020-08-13 -
Integrated primary and tertiary mirror components from common base line of off-axis TMA space camera
Abstract：As axial locations of two mirrors in a space camera with off-axis Three Mirror Anastigmatic(TMA) optical system are closed, this paper proposes a integrated structure combined primary and tertiary mirrors to improve the precision and stability of the opto-mechanical structure. A high-stiffness and ultra-lightweighted integrated support plate was applied as the replacement of separated primary and tertiary mirror support plates to achieve the unification of optical machining, detection and adjustment base lines. The integrated support plate was also a constituent part of the main support frame, so that the entire weight was reduced and the dynamic/static stiffness of the opto-mechanical structure was enhanced. The interference detection of the space camera with the integrated structure was performed. The results indicate that maximum surface shapes of primary mirror and tertiary mirror are 0.024λ (rms) and 0.013λ(rms), respectively, and both meet optical tolerance requirement. The MIMO(multi-input multi-output)free modal test was performed for an aluminum structure prototype, and the results show that the first mode is 48 Hz, which corresponds to the first constrained mode of 114 Hz for the principle prototype and meets the structural stiffness requirement. During ion beam fine optical machining process, the time sharing was used to machine the primary mirror and the tertiary mirror, and the machining efficiency is improved by about 50% for omitting the heat dissipation time. It concludes that the application of integrated structure for primary mirror and tertiary mirror improves the performance and optical machining efficiency of the space camera, and provides a reference for opto-mechanical structure design of high resolution and wide field of view space cameras.Keywords：off-axis Three Mirror Anastigmatic(TMA) space camera;primary mirror;tertiary mirror;common base line;integrated structure;interference detection;modal test;ion beam machining- 81
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Published：2020-08-13 -
Stable pulse micro-feeding of micron spherical metal fine powder
Abstract：For the requirements of stable micro-feeding of micron metal powder in advanced metal part manufacturing technology including laser cladding and 3D micro-printing, the pulse micro-feeding mechanism of micron spherical metal fine powder was researched. To improve the resolution and stability of metal powder micro-feeding, three driving voltage waveforms, including cosine-shape rounded wave, sine-shape rounded wave and sine-cosine integrated rounded wave, were designed as the driving voltages of the piezoelectric actuator. A pulse micro-feeding experiment for the uniform spherical TC4 titanium alloy powder with an average diameter of 100 μm was performed. The experiment result show that the cosine-shape rounded wave makes the powder go forward while the sine-shape rounded wave makes the powder go back. The percentage of the dispersing state powder transported one by one has reached 90%. The powder degree of compaction can be controlled. The powder micro-feeding process is stable without the phenomenon of powder arch accumulation. The obtained results provide references for the micro-feeding of other kinds of powder with different materials and different shapes.Keywords：laser cladding deposition;metal fine powder;micro-feeding;pulse inertia force;micro-nozzle- 47
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Published：2020-08-13 -
Piezoelectric driven hydraulic amplification jetting system
Abstract：To pursue a more accurate non-contact dispensing in a higher speed, a piezoelectric-driven hydraulic amplification jetting system is designed. The system uses a piezostack as the driving source and amplifies the output displacement of piezostack based on the hydraulic amplifier principle to implement the jet glue. Through theoretical analysis of hydraulic amplification module, the structure parameters of the module are designed by combining with the analysis of output displacement of the piezostack. Then, the displacements of the needle and the piezostack are measured by a laser micrometer, and the magnifications of the hydraulic amplifier module on different voltages are obtained. Finally, a jetting system platform is set up, the epoxy with a viscosity of 1 000 cps is chosen to check its property of dispensing, and the relations between the driving voltage, high-low voltage time and the volume of droplet are obtained. The experiments show that the jetting system can stably jet 143 glue dots per second and the volume error of each dot is within ±3.11%, which is a more efficient and accurate dispensing method for the electronic packaging.Keywords：electronic packaging;piezostack;jetting dispensing;piezoelectric driving;hydraulic amplifying- 61
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Published：2020-08-13 -
Structural design of 1.5 m mirror subassembly for space camera
Abstract：The subassembly of a 1.5 m diameter primary mirror in a space camera was researched and the structure system of subassembly for the primary mirror was designed. RB-SiC was chosen as the material of the primary mirror, the lightweight design, support scheme and the structure design of the concrete support were analyzed, and a mirror structure with a mass of 131.9 kg and lightweight ratio of 81% was obtained. The support structure of the primary mirror was designed after determining the basic configuration of the primary mirror. Then, a flexible support structure was reasonably designed to adjust the force, thermal environment adaptability and vibration resistance. Finally, the Finite Element Method (FEM) was used to analyze the performance of the subassembly of the primary mirror synthetically. The experimental results show that the surface figure accuracy(Root Mean Square,RMS) of the primary mirror reaches 0.025λ(λ=632.8 nm)under the action of gravity of 1g and the changed scope is 0.01λ(RMS) in the (20±4) ℃ temperature environment. The first order natural frequency of the subassembly of the primary mirror is 95.8 Hz and the error obtained by the FEM is 4%. It demonstrates that the static stiffness, dynamic stiffness, and the thermal environment adaptability of the subassembly of the primary mirror have met the requirements of design criterion.Keywords：space camera;primary mirror;lightweight;Support;vibration test- 55
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Published：2020-08-13 -
Quickest deployable curve of linear-rotary actuator
Abstract：The quickest deploying of a linear-rotary actuator for wing deployment in a fast air vehicle was explored. The quickest deployable equation was deduced by using the variational method, and a planar equivalent motion model for the linear-rotary actuator was established. The quickest deployable equation is a new kind of curve named by scaled-cycloid here, which is similar to the cycloid curve, but is not any kind of curve from the former research. Some basic characteristics of the scaled-cycloid were studied and the quickest deploying time was calculated. The MSC.Adams software was used to simulate the scaled-cycloid equation and deploying time, and simulation results are well coincident with that of the theoretical analysis. The comparison results with that of cycloid curve show there is no obvious difference of the deployment time between standard cycloid and scaled-cycloid when scaled coefficient (kC) is large than 1, but the deployment time decreases quickly with the decreasing of scaled coefficient when kC is less than 1. The deployment time of scaled-cycloid is just 87% of standard cycloid when the kC decreases to 0.24.Keywords：high speed aircraft;linear-rotary actuator;wing deployment;quickest deployment;cycloid;scaled-cycloid- 38
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Published：2020-08-13 -
Hysteresis and linearization of piezoelectric fast steering mirror
Abstract：For the hysteresis of a piezoelectric Fast Steering Mirror (FSM), the working principle and hysteresis properties of the piezoelectric FSM were analyzed. The Bouc-Wen hysteresis operator based mathematical model of the piezoelectric FSM and the corresponding parameter identification method were proposed. The hysteresis component of excursion angle of the piezoelectric FSM was estimated by the Bouc-Wen hysteresis operator, and parameters of Bouc-Wen hysteresis operator were identified according to the excursion angles of the piezoelectric FSM at two driven voltage waves with the same phase position. On this basis, a feedback forward linearization method for the piezoelectric FSM was proposed. In order to validate the proposed mathematical model and linearization method, the rapid prototyping system for the piezoelectric FSM and a linearization controller and an experimental set for the parameter identification of the Bouc-Wen hysteresis operator were established. The experimental results show that the proposed identification method estimates the parameters of the Bouc-Wen hysteresis operator of the piezoelectric FSM accurately and the feedback forward linearization method increases the linearity of mirror deflection angle and input control voltage of the piezoelectric FSM by 2.3% and decreases the delaying error by ±0.5% respectively. It satisfies the requirements of precision control of the piezoelectric FSM.Keywords：Fast Steering Mirror (FSM);Piezoelectric Ceramic Stack Actuator (PCSA);tilt mirror;hysteresis;Linearization- 59
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Published：2020-08-13 -
Fast degumming of high-precision optical cemented elements
Abstract：A degumming process for optical cemented elements by using a GHJ 01 optical epoxy adhesive bond was researched, and a rapid degumming method suitable for precision optical cementing was proposed. Combined with the actual engineering application requirements, the formula of the adhesive layer thickness for the adhesive cementation was summarized to determine a proper optical-mechanic cementing clearance. The operation processes and cementation curing principle were discussed and the technical problems during the curing were concerned carefully. It points out that the technical points of degumming experiments for a high-precision optical cemented element is to choose a reasonable hot strip temperature and a heating speed according to the different cementing agents and cementation structures. A degumming experiment was performed by using a high precision cemented lens and the quick and microstress degumming of the optical parts was implemented by choosing an appropriate hot strip heating process. The experiment shows that the fused silica mirror has been deformed seriously after the cementation, and it is about 6 times that of the original surface value (The original surface value is 0.02λ and that is 0.14λ after deformation). However the surface value of the fused silica mirror has achieved 0.018λ after the degumming experiments and reworked process finally. The surface value meets the design requirement very well, and the degummed time is 105 h. The new degumming method meets the integrity and micro-stress requirements of the optical elements and avoids the cost of waste and discarding optical elements. It could also been applied to the other same type optical components.Keywords：optical epoxy glue;adhesive layer thickness;cementation curing;degumming experiment;thermal releasing;fast degumming- 64
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Published：2020-08-13 -
Driving control for mounting rack of slant axis astronomical telescopes
Abstract：The non-vertical structure in traditional mounting rack of a slant axis astronomical telescope may cause an image field rotation, which will effect the pointing and tracking of the telescope. There fore, a mounting rack with a slant axis of 45° is developed. By selecting the sun as the tracking target, a hardware driving control system for the mounting rack is designed. Capturing the target by a camera in real time, the system uses Digital Signal Processors(DSPs) here for analyzing exactly the centroid position of target image and decouples the deviation between the two directions by image despun scheme. Combined the fuzzy control and neural network, a self-adaptive fuzzy PID approach with a single neuron is proposed for regulating the position errors of the slant and azimuth respectively to achieve tracking and positioning. The experimental results show that the horizontal and slant axis azimuth tracking bias errors are within 2 pixels, and the average tracking error is 0.123 2° for the horizontal orientation and 0.155 3° for the vertical direction respectively. Experimental results indicate that the driving system is very robust. It solves the control problem caused by image rotations and can meet the precision requirement.Keywords：astronomical telescope;mount;slant axis;Digital Signal Processor(DSP);single neuron adaptive fuzzy PID- 63
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Published：2020-08-13 -
Design and test of macro-micro coupling system for dual-stage lithography
Abstract：To reduce the swap time of wafer stage in a dual-stage lithography, and to guarantee the connection reliability between a long stroke system and the wafer stage, a macro-micro coupling system of dual-stage lithography was designed. On the basis of compliance mechanical theory, the fast gripper of coupling system was designed to realize the compactedness of the system, and its locking force was analyzed. A flexible mechanism of the fast gripper was designed, including a flexible lever and a clamp reset unit, then they were analyzed by finite element method. The pneumatic system in the fast gripper was designed. To guarantee the rapidity and safety in the locking process of coupling device, the pneumatic system could realize three dynamic locking process, and complete the buffer locking of the fast gripper. Finally, the experiments of clamp motion test and the clamping force test were performed. Experimental results indicate that the stroke of the clamp is greater than 2 mm, which meets the safety needs of stroke system and wafer stage. Moreover, the opening time and fast buffer closing time of the clamp coupling mechanism are 350 ms and 850 ms respectively, and can bear X direction driving force more than 700 N. The coupling system ensures the reliability of the working process and rapidity of wafer stage swap process.Keywords：lithography;dual-stage;coupling system;compliant mechanism;fast gripper- 48
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Published：2020-08-13 -
Analysis and testing on inertial impact of piezoelectric inertial actuator
Abstract：The movement of a piezoelectric inertial actuator is come from the inertia impact, so this paper explores the inertia impact of a piezoelectric vibrator excited by a square wave. The impact response of the piezoelectric vibrator excited by the square wave was deducted. The time-domain and amplitude-frequency characteristics of the piezoelectric vibrator were analyzed and the theory and experiment results show that the frequency of the inertial impact signal mainly is concentrate on the 0—500 Hz in square wave excitation. An acceleration sensor was used to test the acceleration parameters and the test results are closed to that of the model. The inertial impact force was calculated by the end inertial mass of the piezoelectric bimorph vibrator, and the amplitude-frequency characteristics of acceleration parameter were obtained by the fast Fourier transfer algorithm.Finally, the tribology method was used to verify the test results. Theory and experiment results show that the maximum relative error of two methods is 8.98%, which verifies that the tests of inertial impacts by acceleration sensors are feasible.Keywords：piezoelectric inertial actuator;inertial impact;square wave;impact response- 68
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Published：2020-08-13 -
Device for improving pointing precision of fast steering mirror with spherical gemel
Abstract：To reduce the axial clearance of a Fast Steering Mirror (FSM) with a spherical gemel and to improve its pointing precision, a device for removing the axial clearance was designed. The structure principle of the FSM with spherical gemel was analyzed and the error sources influencing the pointing precision of FSM were discussed. Then, the device for removing axial clearance was designed, the compress force of a spring was confirmed and its structure parameters were set. Finally, the pointing precisions of FSMs with and without the device for removing axial clearance were tested respectively. The results show that the device for removing axial clearance is very helpful to improve the pointing precision of FSM with spherical gemel, and the azimuth pointing precision has been improved about 4.4 times, the pitching pointing precision has been improved about 3.3 times. The designed flexure device for removing axial clearance not only improves the pointing precision of the FSM but also provides a rigid supporting for the FSM system, so that the carrying capacity of the FSM is increased further.Keywords：fast steering mirror;spherical gemel;axial clearance;pointing precision- 46
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Published：2020-08-13 -
Forming process and high-temperature mechanical properties of variable energy laser selective melting manufacturing IN718 superalloy
Abstract：Selective laser melting manufacturing IN718 powder with changed laser energy densities was researched. The part to be machined was divided into a core and a contour, and the selective laser melting manufacturing was performed by changing the laser energy density. Firstly, a numerical model of sintering in melting pool was set up,the influencing factors of changed laser energy densities on the densification of the part were obtained by changing laser energy densities,and the microstructure features of the formed part were observed. Then, by increasing scanning for the contour and changing the laser energy densities, the effect law of changed laser energy densities on the surface quality of the part was also obtained. Finally, the heat treatment processing was optimized and the high-temperature tensile strength and high temperature lasting time properties of the part were improved to obtain the perfect surface quality. The results indicate when the linear laser energy density is 300 J/m, the optimal densification level of formed part is as high as 98.9%. In this condition, the typical microstructures of the formed part are dendrite and equiaxial crystals along the deposition direction and are equiaxial crystal along the inside layer. Using the core + contour scanning way, the optimal surface quality of the part is obtained in laser energy densities of 100 J/m with the roughness of 3.1 μm. The optimal high temperature performance of the formed part is realized by solution + double aging combination in 1 065 ℃, in which the high temperature tensile strength is 1 356 MPa and the high temperature lasting time is 34 h. Results show that the IN718 nickel-based super alloy manufactured by selective laser melting can satisfy the demands of complex aerospace parts for the densfication level, good forming quality and high-temperature mechanical properties.Keywords：IN718 nickel-based superalloy;variable energy laser selective melting;laser-forming;density;surface quality;high temperature mechanical property- 51
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Published：2020-08-13 -
Application of generalized radial basis function neural network to thermal error modeling
Abstract：In considering of the lower efficiency and worse prediction accuracy of the existing thermal error modeling methods, a generalized Radial Basis Function (RBF) neural network modeling approach was proposed to establish the thermal error model of Numerical Control(NC) machine tools. The model theory and the corresponding steps based on this method were discussed. An experiment on the spindle box of a NC guide rail grinder was performed, and two groups of independent thermal error data were obtained by setting twelve critical temperature measuring points of spindle thermal error. One group of the data was used for building the thermal error model of the spindle box system based on generalized RBF neural network method and the other was used for verifying the correction of the model. The study results show that the thermal error model based on generalized RBF neural network method has high prediction precision and good generalization ability. By comparing the generalized RBF neural network method with traditional RBF neural network modeling method, the former shows better efficiency, robustness and prediction capacity, and it is an effective modeling method for the real-time thermal error compensation of NC machine tools.Keywords：generalized radial basis function;neural network;thermal error modeling;clustering algorithm;generalization ability;robustness;Numerical Control(NC) guide rail grinder- 63
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Published：2020-08-13 -
Suppression of metal artifact in computed tomography by reweighted total variation reconstruction
Abstract：A novel metal artifact reduction algorithm based on a Reweighted Total Variation (RWTV) reconstruction was proposed to suppress the metal artifacts in Computed Tomography (CT) images to improve the image quality. A user-defined weight function was used as penalty weight to generate the weighted Total Variation(TV) model. The reweighted TV reconstruction algorithm was implemented through solving alternately the weighted TV minimization problem and updating the weight procedure. Then, the algorithm was used in the reconstruction experiments for projections from forward projecting phantom and clinical data respectively. The digital phantom experiments show that the proposed algorithm has the topmost spatial resolution of reconstructed images in 60 sampling angles. Furthermore, the signal-to-noise ratios of images through the proposed algorithm are 17.523 6, 7.145 2 dB higher than those of images reconstructed by Smooth Interpolation Metal Artifact Reduction (SI-MAR) algorithm and TV minimization based on Constrained Optimization-Penalized Smoothness (CO-PS) algorithm respectively. Clinical experimental results demonstrate that the proposed algorithm successfully suppresses the metal artifacts and clearly restores the anatomical structure in the skull. Moreover, the quality of reconstructed images has been greatly improved by the proposed metal artifact suppression algorithm.Keywords：Computed Tomography(CT);image reconstruction;metal artifact;reweighted Total Variation(TV);TV minimization;signal-to-noise ratio- 55
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Published：2020-08-13 -
Pose estimation based on multiple line hypothesis and iteratively reweighted least squares
Abstract：To estimate the pose of known rigid objects efficiently in a complex environment, a rigid object pose estimation method was proposed by combining multiple line hypothesis and iteratively reweighted least squares. The 1D search was utilized to obtain the corresponding image point along a normal direction for each model sample point by an equal interval sampling. Then, the weight of a sample point was calculated according to the local and global appearances of the corresponding image point for each visible model sample point. The optimized pose parameters were obtained by minimizing the errors between the sample points and their corresponding image points. To avoid the failure of the pose optimization caused by the mismatches of the model and image lines, multiple low level hypotheses were retained for each model sample point in the registration process and they were classified into multiple lines for each potential edge by the Random Hough Transform(RHT). Due to the use of the property of the sample point as well as the relation to the neighbor points, the robustness to disordered background and noise was enhanced in the weighting process. Experiments show the proposed method effectively estimates the poses of freely moving objects in an unconstrained environment. The precisions of the poses on x, y and z axes are better than 0.4°, 0.3° and 0.1° respectively; and those of relative positions perpendicular to the optical axis and along the optical axis are better than 0.03% and 0.1% respectively. Comparisons with the single hypothesis based method demonstrate that the proposed method overcomes the influence induced by the complex background and optimizes the pose parameters in special views.Keywords：machine vision;pose estimation;3D tracking;multiple hypothesis;Iteratively Reweighted Least Square(IRLS)- 50
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Published：2020-08-13 -
Guide star selection for star pattern recognition between three FOVs
Abstract：A guide star selection algorithm for the three Field of View(FOV) navigation system was proposed to increase the efficiency of the star pattern recognition between three FOVs, and to decrease the size of a guide star database. According to the characteristics of star pattern recognition for three FOV navigation system, the influence of the number of guide stars between three FOVs on the triangle star pattern recognition was analyzed. According to the requirement of triangle star pattern recognition between FOVs, the guide star selection principle, one guide star at least is inside the FOV and the brighter star can be selected in priority, was presented. Then the 1st order self-organizing guide star selection algorithm based on the principle magnitude mentioned above was proposed. A guide star database between FOVs was established based on the proposed algorithm, and the simulation analysis and field experiments of the capability of the guide star database were performed. Experimental results indicate that the number of the guide stars in the database selected by this method have reduced by 53.91% compared with that of the visual magnitude threshold method and the guide stars in the database show uniform distribution. It satisfies the guide star selection requirement of the star pattern recognition between FOVs in celestial navigation systems.Keywords：celestial navigation;three FOVs;star pattern recognition;guide star selection- 94
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Published：2020-08-13 -
Fault diagnosis based on knowledge pushing in multi-sensor integration hydrogen detection system
Abstract：As multi-sensor integration hydrogen detection systems can not diagnose the working state by itself, an expert system of fault diagnosis based on knowledge was analyzed and a fault diagnosis method based on knowledge management and knowledge pushing was proposed. The hierarchical structure of the fault diagnosis method used in the multi-sensor integration hydrogen detection system was investigated. On the basis of the principle of expert systems, the texture of expert system based on knowledge pushing actively was presented. After the fault modes were analyzed, a knowledge base fault diagnosis design was discussed. Then the method and step of inference engine based on knowledge pushing actively were researched by its established model. Finally, the fault diagnosis unit for multi-sensor integration hydrogen detection system based on knowledge pushing was designed. Experimental results indicate that the fault diagnosis accuracy rate of the proposed method reaches above 97%, which verifies the effectiveness of the method. It can transfer initiatively the knowledge to the decision-maker at opportune moment, and improve the speed and accuracy rate of fault diagnosis.Keywords：hydrogen detection system;multi-sensor integration;fault diagnosis;knowledge pushing;Expert system- 46
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Published：2020-08-13 -
Camshift tracking with saliency histogram
Abstract：According to the target tracking requirements in complex backgrounds, an improved Continuously Adaptive Meanshift(Camshift) tracking method was proposed by modeling a saliency histogram of the target. The saliency values of different hues in the target area were calculated by comparing the difference between the target and the background area. The weighted histogram was used to strengthen the roles of the saliency hues and weaken the roles of the non-saliency hues, by which the interference from the background was restrained. By using the back projection of the weighted histogram, the probability projection image of the tracking image was obtained by the back projection, then the target tracking task was completed by mean shift method. The proposed method was applied to an actual target in tracking experiments and that in the video of the standard test libraries and obtained results were compared with that of traditional methods. The simulation results show that the target is easily recognized from the background by the saliency hues, and the accuracy and the stability of the target recognition are improved with satisfied real time ability and without too much computation cost. The ratio of the max deviation to the size of the target is less than 25%, which ensures the target not to be lost.Keywords：target tracking;saliency;histogram;hue;Camshift tracking- 56
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Published：2020-08-13 -
Chord angle representation for shape matching under occlusion
Abstract：A shape description method based on chord angle representation was proposed to solve the problem of shape matching under partial occlusion, meanwhile balancing retrieval accuracy and computational efficiency. A chord angle descriptor was defined based on the angle between two chords for each sample point, which could be used to describe an open contour by its self-contained property. Then, a match cost matrix was constructed by computing the L1 distance between descriptors of all the sample points on two open contours. Finally, the similarity between two contours was obtained by the integral image algorithm and the partial shape matching result was achieved. The experimental results on MPEG-7 and Kimia216 shape databases indicate that this method is robust to the partial occlusion, and the computational efficiency and the retrieval accuracy are both essentially improved as compared with other partially occluded shape matching algorithms. The retrieval accuracy of proposed partial contour matching method reaches to 83.63% and increased by 19.09%. It concludes that this proposed method meets the requirements of shape matching and object recognition in efficiency, accuracy and ability of anti-occlusion.Keywords：Shape Matching;partial occlusion;chord angle representation;integral image- 33
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Published：2020-08-13 -
Fast digital image stabilization based on characteristic peak of projection matching
Abstract：A new image stabilization algorithm based on the characteristic peak of projection matching was proposed to improve the real-time characteristics of gray projection image stabilization method. Firstly, the reference frame and the current frame were divided into several sub image blocks, and the horizontal projection and vertical projection of each sub image block were calculated according to the projection calculation formula. Then, the horizontal and vertical position differences of the corresponding sub blocks' maximal projection characteristic peaks were calculated as motion vectors, and the motion vectors were corrected according to the motion vector variance ratio between frame and frame. Finally, the global motion vectors were derived based on the sub motion vectors. The proposed algorithm based on the characteristic peak of projection matching was used in a multi-spectral imager and obtained results were compared with that of the traditional gray projection image stabilization method.The experimental results show that new algorithm has saved nearly 20% time as compared with that of the traditional one for 1 024 pixel×1 024 pixel resolution image sequence and the (-60,60) regions of search. It does not have complex match processing that traditional method has to research the image projection area one by one, and can offer good real-time performance and stabilization effect.Keywords：digital image stabilization;gray projection;characteristic peak matching;motion estimation- 52
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Published：2020-08-13 -
Hand shape recognition based on fusion features of fingers and particle swarm optimization
Abstract：As the hand shape recognition method based on geometric features is limited by its individual information, this paper presents a new hand shape recognition method based on the fusion of finger contour features and geometric features. A curve fitting method was proposed to position the axis of finger after four fingers were separated. Then the matched fingers were normalized by stepwise alignment method, and the contour features and geometric features were extracted. Finally, the Particle Swarm Optimization (PSO) was used to optimize the cut-off coefficients and the weight values of fingers to further improve the recognition rate. Experimental results show that the recognition rate by proposed method is 98.61%. As the four fingers are separated, the proposed method reduces the computing consumption and gets more accurate located hand shapes. With make full use of the hand information,it also avoids the influence of inaccurate feature point location and instable contour around finger valleys on the recognition accuracy, and has high recognition rate and good robustness.Keywords：hand shape recognition;feature extraction;fusion feature;contour matching;Particle Swarm Optimization(PSO)- 55
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Published：2020-08-13 -
Dynamic rate control for CCSDS nearly lossless compression of multispectral remote image
Abstract：On the basis of CCSDS-123.0-B-1 lossless compression algorithm of multi-spectral image recommended by the Consultative Committee for Space Data Systems(CCSDS), a rate control method of forward adaptive quantifying step size was proposed to achieve the nearly lossless compression with a fixed rate. The prediction method of CCSDS was introduced and the ranges of the upper bound and lower bound of Golomb-Rice coding were analyzed. By analyzing the relationship between prediction error and the compression rate, their approximate linear mapping curves were established. According to the mean value of prediction error, the quantization step size was adaptively estimated and the Golomb-Rice coding length was preliminarily controlled. In addition, taking the multi-spectral image rate control strategy under spaceborne conditions into account, the compression code rate was precisely controlled by fine tuning the quantization step size according to the feedback of compression rate. At last, the processes of CCSDS nearly lossless compression rate control method was presented. The experiment results show that distribution area of k (Golomb coding variables) is stable. At the compression rate of 4:1, the Peak Signal to Noise Ratio(PSNR)from the proposed method is 60.42 dB averagely, which is increased by 5.51 dB and 2.89 dB as compared with those from JPEG2000 and differential JPEG-LS methods respectively. The rate control method is accurate, easy to be implemented in hardware and suitable for aerospace engineering.Keywords：Multispectral image;remote sensing image;nearly lossless compression;standard of Consultative Committee for Space Data Systems(CCSDS);code rate control- 48
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Published：2020-08-13 -
Calculation of thread pitch diameters based on two dimensional profile point clouds
Abstract：The multi-parameter measurement of a thread based on profile points may show calculation errors for thread pitch diameters owing to the alignment deviations and inhomogeneous abrasion of thread work-pieces. Therefore, a new method for calculating the thread pitch diameters based on the 2-dimensional profile point clouds was proposed. The cubic spline interpolation was used to increase the data point densification uniformly, and the robust Gauss regression filter was adopted to get the midline of contour. Then, an objective function was put forward to minimize the mean square error of the distance between two adjacent flank segments, and the complex simulated annealing algorithm was adopted to solve the function to get the pitch line. Finally, the pitch diameter parameters were calculated with the obtained pitch line. The experimental results show that the measurement error of pitch diameter obtained by the proposed method is reduced by 17.23% and 96.93% respectively compared with the methods from FAN Y B and TONG Q et al, when the alignment deviation along axes directions of X, Y, Z is 1 mm and the rotation deviation of each axis is 2°. The proposed method effectively reduces the influence of alignment deviations on the thread pitch diameters, and can be used for two dimensional point cloud data by both contact and non-contact 2-dimensional scannings.Keywords：thread workepiece;2-dimensional thread profile;pitch diameter calculation;alignment deviation;cubic spline interpolation;robust Gauss regression filter;simulated annealing algorithm- 84
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Published：2020-08-13 -
Robust digital imaging Spearman's Rho correlation for pepper and salt noise
Abstract：When traditional digital image correlation technique is used to measure the deformation displacement, the digital image with very small amount of pepper and salt noise is difficult to be processed precisely. Therefore, this paper proposes a new digital image correlation method based on Spearman's rho(SR) correlation coefficient robust to pepper and salt noise. According to the SR's average statistic characteristics, the SR coefficient of bivariate Gaussian mixture model is mainly decided by the clean speckle image when the density of pepper and salt noise is small enough. To verify the robustness of the SR to pepper and salt noise, the controllable simulation speckle image is used in a simulation, and the SR correlation technology is used to calculate the scanning errors. The results indicate that it can still get the accurate displacement vector by the SR digital image correlation when the density of pepper and salt noise is less than 25% and the block size is 41 pixel×41 pixel. The algorithm is used to calculate the laser-scanning texture data, and the sampling offset calculated is 4 μm with the correlation coefficient of 0.996 6. The result shows that the SR digital image correlation technique has strong robustness, and is suitable for calculating the deformation displacement vector under the pepper and salt noise.Keywords：digital image correlation;pepper and salt noise;Spearman's rho correlation coefficient;deformation field distribution- 70
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Published：2020-08-13
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