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Issue 9 ， 2015
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Influence of skylight polarization pattern on bionic polarized orientation and corresponding experiments
Abstract：To solve the problems of directional precision errors and low stability existed in a bionic polarized light compass caused by the weather and sun position or other factors, the effect mechanism of sky polarization mode on polarized orientation was researched. A polarized orientation model including model errors was built and the algorithm to calculate a heading angle for the bionic polarized compass was deduced. Then, the influence of the model errors on the polarized orientation precision was analyzed systematically. It points out that the horizontal angle and the solar altitude angle are main factors to determine the impact of the model errors. Finally, a static experiment and a dynamic car test were designed. The influence of polarized model errors on the polarized orientation precision was assessed in different horizontal angles and solar altitude angles. The results indicate that when the solar altitude angle is less than 40°, the error of polarized orientation is 0.729°. When the angle is between 40° and 75°,the precision is evidently decreased,and the error is 3.764°. Moreover,the impact of polarized model is also evidently increased as the horizontal angle. When the vehicle runs in a level, the error is 0.323°. After inclining, the error is increased to 1.352°. The error mechanism proposed provides theoretical references for compensating model errors and improving the precision of polarized orientation.Keywords：polarized light navigation;skylight polarization pattern;polarized orientation;orientation algorithm;heading angle error- 54
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- 3
Published：2020-08-12 -
Optical and electrical properties of vanadium pentoxide films prepared by RF reactive magnetron sputtering
Abstract：Vanadium oxide (V2O5) films were deposited on sapphire substrates by Radio Frequency(RF) reactive magnetron sputtering at sputtering time of 15 min,25 min,30 min and 45 min. The film structures, film thicknesses, surface morphology, electrical and optical properties were studied at different sputtering time and other experimental parameters unchanged. The results indicate that the deposited films are polycrystalline V2O5 films on (001) preferred orientation. With the increase of sputtering time, crystallization behaviors become stronger, the grain sizes are larger, and the surface roughness values are reduced gradually. Moreover, phase-transition temperatures and temperature ranges are increased while the electrical mutation properties are reduced. The transmittances of the films (thickness of 350 nm) in a middle-infrared band were detected at high and low temperatures. The results show that the rangeability of transmittances (wavelength of 5 μm) is as high as 74% which ranges from 81% at 25 ℃ to 7% at 300 ℃. All the transmittance ratios before and after phase transitions are between 9—13, showing a very prominent optical-switching property.Keywords：V2O5 film;magnetron sputtering;sputtering time;thin film thickness;electrical performance;infrared transmittance- 36
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- 9
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- 4
Published：2020-08-12 -
Correction of angle measuring errors for large telescopes
Abstract：As the turntable shaft system of a large telescope needs a higher angle measuring precision,this paper explores an error correction method for the angle measuring system. The causes of data errors of angle measuring were analyzed, and the errors of angle measuring device, installation errors and the errors of measured shaft were discussed. It points out that the error rules of the shaft angle measuring subsystem are according with a resonant equation, so the resonant equation was used to explain the error rule. For engineering applications, a simplified resonant equation error formula was established through the research of the Fourier series, Then, the harmonic equation algorithm and the polynomial fitting algorithm were used to correct the system errors. A test was taken on the vertical axis turntable of a telescope and the results show that the peak of angle measurement precision is improved from 3.81"to 1.06". The experiments indicate that the modified algorithm based on Fourier series conforms the error distribution rule better. The error correction method corrects comprehensive errors of the system in a unified way and effectively improves the angle measurement precision of the system.Keywords：telescope;angle measurement system;Encoder;angle measurement precision;error correction- 61
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- 9
Published：2020-08-12 -
Detection on interfacial tension of insulating oil with trace water based on mid-infrared spectroscopy
Abstract：To monitor the operating status of insulating oil effectively, the affecting law of trace water on the interfacial tension of insulating oil was investigated by a quantitative method. By making up a series of oil samples with different trace water contents, the interfacial tension of every group of oil sample was measured and its mid-infrared spectrum was scanned. Then, the absorbance values of oil samples at the characteristic wave number of water molecules (1 640 cm-1,3 400 cm-1,3 450 cm-1,3 615 cm-1) were obtained and the influence of the 2,6-Di-tert.-butyl-p-cresol (T501), a kind of additive in oil samples, on the interfacial tension was analyzed. The results show that the trace water contents in oil samples are dependent on water characteristic absorbance values, which can be up to 0.964 1,0.984 8,0.984 5 and 0.944 0. Moreover, there is a good positive correlation between the trace water contents in oil samples and the changes of absorbance values of oil samples at 1 640 cm-1,3 400 cm-1,3 450 cm-1,3 615 cm-1,3 650 cm-1. According to these data, a multiple linear regression model with the goodness fit of 0.992 8 was constructed. The error between calculated values and measured values of the interfacial tension varies from -0.07% to 0.06%, shows a good coincidence. This research supports the measurement of interfacial tension for insulating oil in theory.Keywords：mid-infrared spectrum;insulating oil;interfacial tension;trace water;quantitative measurement- 49
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- 6
Published：2020-08-12 -
4-primary-color-based LED backlight for aircraft cockpit LCD
Abstract：According to the special requirements of Liquid Crystal Display(LCD) in an airplane cockpit, a 4-primary-color-based LED(Lighting Emission Diode) backlight is developed. The LED backlight applies LEDs with 4 different colors of red, green, blue and amber to control the lightness independently. In the day model, all LEDs with different colors are turned on to form white lights. In the night mode, the red LEDs are closed to reduce infrared radiation. The mixed ratio of green, blue, and amber LEDs in the night model is first calculated. With the fixed luminance of blue LEDs, the ratios of red, green, and amber LEDs in the day model are decided. The detailed simulations are performed to decide the physical structures and optical characteristics of the backlight. The 3-in-1 LEDs with the individual amber LEDs are applied in a prototype. Experimental results show that the luminance, nonuniformity, and color gamut of the backlight in the day model are 23 515 cd/m2 (1 175 cd/m2 of panel brightness), 8.07%, and 116.5% NTSC(National Television Standard Committee), respectively; and those in the night model are 15.36 cd/m2 (0.77 cd/m2 of panel brightness), 15.49%, and 83.5% NTSC, respectively. The developed backlight satisfies the requirements of luminance and night-vision-compatibility of aircraft liquid crystal display.Keywords：Light Emitting Diode(LED);backlight;Night Vision Image System(NVIS);liquid crystal display;color gamut- 35
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- 11
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- 2
Published：2020-08-12 -
Surface topography measuring system based on wavelength switching and phase shift scanning
Abstract：When optical microscopic interferometry is used to measure the surface topography, there is a contradiction between the enlargement of measuring interval and the improvement of measuring precision. Therefore, a three-wavelength interference measurement system for surface topography was designed based on wavelength switching and phase shift scanning. A data processing method for three wavelength interference images was proposed by using the phase extraction and recognition algorithm based on elliptic fitting and combined size scales of phase difference. The method was used to process multi-wavelength interformetric images, and it effectively improves the overall precision of surface topographic measurement and expands the measuring interval. Experimental results show that when the measurement interval is expanded to nearly 15 times, the relative measurement error of surface roughness of square wave specimen with multiple grooves is only 4.12% as compared to that of the data calibrated by China Metrology Institute. It concludes that the three wavelength interferometry realizes a high precision measurement for surface topography in a certain range. Moreover, the data processing method for multi-wavelength phase recognition has not higher demands for environment noise and can support system measurement in a higher noise environment in real time.Keywords：surface topography measurement;phase shift interference;wavelength switching;phase shift scanning;optical microscopic interferometry- 73
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- 14
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- 4
Published：2020-08-12 -
Closed-loop feedback intelligent control system for tunnel lighting
Abstract：To solve the current problems in tunnel lighting, such as power consumption, illumination measuring complex, and difficult to ensure the actual luminance in real-time, a tunnel lighting closed-loop feedback intelligent control system is presented in this paper. The system realizes the lighting by need through adjusting lighting states based on the vehicle behavior information and environmental perception information collected by a sensor. It uses a camera image to measure luminance, and acquires pavement luminance in real-time through the transformation relationship between the image gray and pavement luminance. To meet the required luminance by lighting, the PID closed-loop feedback adjustment method is used to adjust the output of the lighting system in real-time and to ensure the actual luminance. The experiment shows that the designed system is secure and reliable and has higher adaptive ability. It is characterized by luminance measurement in real time, closed-loop feedback adjustment, lighting by need and can ensure the actual luminance to meet standard requirements. Meanwhile, it reduces energy consumption and offers an optimum visual experience for human eyes at safety driving vehicles.Keywords：tunnel lighting;PID closed-loop feedback;energy-saving;luminance;intelligent control system- 71
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- 9
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- 1
Published：2020-08-12 -
Measurement of defocused spot parameters of optical system
Abstract：Defocused spot parameters of an optical system were measured by a testing system with CCD microscopic imaging quantitatively, and an evaluating method for the defocused spot parameters was designed. Firstly, the definitions of the defocused spot parameters including the diameter and the roundness were given. The connected region shaped by the energy contour of the defocused spots was analyzed, and the diameter equal to the area which is 80% of the total energy of the defocused spots was calculated. Then, the boundary of the region was fitted as an ellipse and the roundness of defocused spot was obtained. The method introduces the ellipse fit into the defocused spot roundness measurement through analysis of the energy distribution of star point image on image plane, so that the effects of CCD noise and stray light in test environment on the measuring results are reduced and the confidence of the test results is improved. The experimental results show that the repeatability of the diameter is 0.18 μm and that of the roundness is 1.65%. The method meets the needs of the optical systems in space projects for the imaging quality control.Keywords：optical system;defocused spot parameter;CCD microscopic system;energy contour;region filling;ellipse fitting- 79
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- 12
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- 2
Published：2020-08-12 -
Rapid quantitative determination of components in ternary blended edible oil based on Raman spectroscopy
Abstract：The rapeseed oil, peanut oil and sesame oil contents in ternary blended edible oil were measured quantitatively by laser Raman spectroscopy combined with the chemometric resolution method. Two kinds of pretreatment methods called Standard Normal Variate(SNV)+de-trending and Orthogonal Signal Correction(OSC) were used to process the original Raman spectra at 600—3 000 cm-1 , respectively. The quantification calibration models based on nonlinear Support Vector Machine(SVM) and linear Partial Least Squares (PLS) for the rapeseed oil, peanut oil and sesame oil were established, and nineteen prediction samples were predicted using the external cross-validation to verify the accuracy of these models. The results show that linear PLS model after the OSC spectral processing obtains the best result for ternary blended edible oil containing rapeseed oil, peanut oil and sesame oil. The determination coefficients(Rp2)of the prediction are 0.990 4, 0.965 8, 0.977 1 and Root Mean Square Error of Prediction (RMSEP) are 0.018 8, 0.037 9, 0.026 2, respectively. The research results indicate that laser Raman spectroscopy combined with chemometric resolution method can be used for the determination of the contents for rapeseed oil, peanut oil and sesame oil in ternary blended edible oil, and can achieve excellent prediction precision.Keywords：Raman spectroscopy;blended edible oil;Support Vector Machine(SVM);Partial Least Square(PLS);quantitative determination model- 64
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- 14
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- 17
Published：2020-08-12 -
Fast grinding of large SiC off-axis aspheric surface
Abstract：A fast ultrasonic grinding for SiC off-axis large aspheres used in space remote sensors was researched. The principle of grinding, the selection of diamond grinding wheel bond, the selection of machine tool, and setting grinding parameters were analyzed, and the grinding process was designed. A high precise model of off-axis aspheric surfaces was established on the basis of the principle of reverse engineering, and the online testing method in fine grinding state for a large off-axis aspheric mirror by a laser tracker was established. Combination with an engineering example, the model of a large SiC off-axis asphere with the aperture of 700 mm×700 mm was established by the reverse engineering principle, and it was grinded by ultrasonic method and measured by the laser tracker. After 3 cycles (4 hours per cycle of grinding), the PV value(45.986 μm) and RMS value(7.949 μm) of the surface error are reduced to 12.181 μm and 2.131 μm, respectively. As compared with three coordinate testing results, the errors of PV value and RMS value are 0.892 3 μm and 0.312 8 μm, respectively. It concludes that the grinding technology realizes fast and high precise grinding for the SiC off-axis large asphere and improves its machining precision, efficiency, and surface quality.Keywords：optical fabrication;SiC off-axis asphere;fast grind;ultrasonic grinding;online testing- 59
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- 6
Published：2020-08-12 -
Precise ground target location of subsonic UAV by compensating delay of navigation information
Abstract：For the real time ground target location precision of an Optic Electric(O-E) reconnaissance platform of the subsonic Unmanned Aerial Vehicle (UAV), an algorithm for O-E platform location was proposed based on inertial navigation information. The influence factors on the precision of target location were studied by using the mathematics model and error model of target location. The mathematical simulation model with influences of parameter errors on the precision of target location was established. Simulation results show that the real-time performance of the satellite navigation information is the decisive factor affecting the target location error. Then, it points out that modifying the delay time of the satellite navigation information can solve the real-time target location error problem of the O-E reconnaissance platform. A flying experiment was carried out to verify the results above mentioned. The results indicate that real-time target location precision of O-E reconnaissance platform for the high speed UAV has been substantially improved by modifying the delay time of the satellite navigation information, and the location error has decreased from 100 m to less than 40 m. The result has important reference values for applications of high speed aerocrafts.Keywords：Unmanned Aerial Vehicle(UAV);photoelectric reconnaissance platform;target location;satellite navigation;delay compensation- 63
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- 14
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- 5
Published：2020-08-12 -
Preparation of shear thickening polishing abrasive slurries and their polishing properties
Abstract：To realize Shear Thickening Polishing (STP) for workpieces, a kind of Al2O3-STP slurries were prepared by mechanical mixing and ultrasonic dispersion methods and their polishing properties were investigated. The rheological properties of dispersion of STP slurries were studied by using a stress controlled rheometer. The morphologies of a Si wafer before and after STPs were also researched by a Scanning Electron Microscopy(SEM) and an optical profilometer, and their surface roughnesses were measured. Experimental results indicate that the STP slurry sytem has shear thinning and reversible shear thickening behaviors. The Al2O3 “cluster” would be formed as the critical shear rate is reached. When the shear rate increases to 1000 s-1, the storage modulus, loss modulus and the dissipation factor are increased to a maximum value, respectively. At this time, the slurry shows the main properties of the elastic behavior like solid, which are conducive to the formation of “flexible fixed abrasive tool”. In STP process, the material of Si wafer is removed by ductile mode. As extension of polishing time, the material removal rate increases quickly, but grows at a slow rate in the later period. The surface roughness decreases and tends to a stable during the STP process. Moreorer, it suggests that the abrasive concentration should not be too high, otherwise polishing quality would be affected. When the mass fraction of Al2O3 is 23%, the surface roughness Ra reduces from 422.62 nm to 2.46 nm and removal rate is up to 0.88 μm/min after polishing by 25 min, which indicate that it achieves high efficiency precision polishing of Si wafers.Keywords：Shear Thickening Polishing (STP);shear thickening;Al2O3;STP slurry;Si wafer- 39
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- 14
Published：2020-08-12 -
Error and fault-tolerant processing of parallel type six-axis accelerometer
Abstract：On the basis of decoupling algorithm, the error characteristics and fault-tolerance strategy of a parallel type six-axis accelerometer were researched. By introducing an aided angular velocity and using quaternion to describe rotation parameters in a four-dimensional space, two explicit recursive formulas with simple forms were obtained, and six-axis accelerations were entirely decoupled. By analyzing the decoupling mechanism, three kinds of error sources affecting the decoupling precision were obtained, and the reasons that cause the error were analyzed. By establishing the mapping relations between the error of aided angular velocity, source errors and output errors, the analytical expressions of the basic error equations were derived, and then the influence rules of error components were revealed. The verification experiment shows that the mathematical results are well consistent with the simulation ones in ADAMS, and the relative error between them is acceptable. Three force coordination equations were derived by establishing the hidden deformation compatibility conditions of elastomeric topological configuration, and then a fault-tolerant processing scheme was proposed to solve 93 combined failures. Experimental results indicate that the maximum relative error is 8.5% after using the new algorithm to decouple the six-axis acceleration of the systems with partial failures, which meets the accuracy requirements. Above results verify that the influence rules of errors and the scheme of fault-tolerant processing are both correct and feasible, and also demonstrate that the parallel type six-axis accelerometer has some level of robustness.Keywords：Six-axis accelerometer;Decoupling;Error;sensitivity;fault-tolerant processing;robustness- 54
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- 12
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- 2
Published：2020-08-12 -
Effect of vacuum outgassing on dimensional stability of composite materials
Abstract：To verify the influence of outgassing effects of polymer matrix in a vacuum environment on the dimensional stability of composite materials, this paper researches the outgassing properties of carbon fiber composite materials on the epoxy and cyanate resin matrixes. Firstly, the relation between expansion coefficient and outgassing coefficient was analyzed theoretically. Then, the test assemblies were designed to accurately measure their changes in the size and the mass. Finally, vacuum tests were carried out three times for several groups of test assemblies according to the demands of satellite environmental test conditions. Experimental results on the sizes and mass of these test assemblies show that the mass loss rates (TML) of epoxy matrix and cyanate resin matrix composite materials are approximately 0.033%—0.06% and 0.014%—0.029% respectively. Moreover, the size changes of epoxy matrix and cyanate resin matrix composite materials are about 2—8 μm, and 1—3 μm respectively. The mass change of the former is 2 times that of the latter, which means the dimensional stability of two kind of composite materials has different in the vacuum environment.Keywords：composite materials;cyanate resin;epoxy;vacuum outgassing;dimensional stability- 63
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- 17
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- 0
Published：2020-08-12 -
Force feedback close-loop detection of silicon micromachined gyroscope based on bandpass sigma delta modulator
Abstract：To enhance the performance of a silicon micromachined gyroscope, a force feedback close-loop detection method based on a fourth-order electromechanical bandpass Sigma Delta modulator(SDM) was researched. A simulation model was established based on Cascade Resonant Feed Forward(CRFF) structure of a resonator. Meanwhile, the loop parameters were calculated with the commercial software SD TOOLS. Then behavioral simulations were carried out with MATLAB/SIMULINK to test the results. The results suggest that the Signal to Noise Ratio(SNR) of the loop achieves 109.2 dB at the bandpass of 1 Hz, which meets the previous expectation. A force feedback close-loop detection system for the silicon micromachined gyroscope was designed by using a Field Programming Gate Array(FPGA) as the processing core, and the properties of gyroscope were tested. Experiments indicate that based on this detecting method and digital close-loop driving technology, the zero bias instability of the gyroscope achieves 1.15(°)/h, and the Angle Random Walk (ARW) is around 7.74×10-2(°)/√h. Meanwhile, the Signal and Noise Ratio(SNR) meets the designed specifications. These results verify the validity of the detecting technique. The method is conductive to improving the performance of the SMGs and extending their application fields.Keywords：silicon micromachined gyroscope;force feedback close-loop detection;Sigma Delta(Σ-Δ) modulator;Allan variance- 77
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- 13
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- 2
Published：2020-08-12 -
Linearity calibration and uncertainty evaluation for capacitance displacement sensor
Abstract：As the linearity of capacitance sensor in adjusting a lithographic projection objective could not meet the requirement of the adjustment mechanism for accuracy standard, a method to improve the measuring linearity of the capacitance sensor was proposed. A piezoelectric actuator was used to provide displacement feeding and a higher precise laser length interferometer was used to provide displacement feedback to ensure the accuracy of moving control. The fitting factors getting from the high order curve fitting were used to calibrate the linearity of the capacitance sensor online. Then, the uncertainties of the environment, installation mechanism and control were analyzed and evaluated to meet the accuracy of the linearity measurement. Finally, calibration experiments for the sensor were carried out. The experiment results indicate that the calibration method of the linearity proposed reduces the influence of the error on the measurement results. After calibration, the linearity of capacitance sensor increases from 0.047 14% to 0.004 84%, nearly an order of magnitude. Moreover, the capacitance sensor has high linearity repeatability, the deviation of repeatability is 0.38 nm, and the combined uncertainty of the linearity in the whole stroke is 5.70 nm, which meets the displacement control accuracy of the lithographic projection objective.Keywords：capacitance sensor;displacement sensor;calibration;linearity;uncertainty;lithographic projection objective- 64
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Published：2020-08-12 -
High precision sliding mode control for micro-momentum wheel
Abstract：The precision control of a micro-momentum wheel in micro-satellite was researched based on a sliding mode control algorithm. On the basis of the whole control system framework, the dynamic model of the micro-momentum wheel was analyzed. Combination of the ideal model and consideration of the interference factors such as ripple voltage, the uncertainty of friction coefficient, and disturbance torque, the dynamic model of micro-momentum wheel was improved. Then, sliding mode control algorithm was designed, and simulation control rate parameters were optimized. Through MATLAB simulation, sliding mode control and conventional PI control were compared for the torque control and speed control. Finally, a micro-momentum wheel prototype was designed. The simulation results show that the speed control precision of the micro-momentum wheel based on sliding mode control is ±0.5 r/min and it can accelerate from 0 to 2 000 r/min in 18 s, both are much better than that based on PI control. Experimental results demonstrate that the speed control precision of the micro-momentum wheel based on sliding mode control is ±0.9 r/min and it can accelerate from 0 to 2 000 r/min in 26 s. These results indicate that sliding mode control algorithm effectively overcomes the control interference factors of the micro-momentum wheel and improves the speed control precision, shortens the acceleration time.Keywords：micro-satellite;attitude control;micro-momentum wheel;sliding mode control;simulation and calculation;prototype experiment- 91
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Published：2020-08-12 -
Position layout of rear three point mounting for space rectangular mirror
Abstract：It is difficult to conclude a general method in opto-mechanical design for rectangular mirrors mounted via rear three-point method in a space remote sensor. So, the individual opto-mechanical design for a given size rectangular mirror is usually used. In this paper, an integrated parametric design method based on a regular model was proposed and a parametric model for 3-point mounting space rectangular mirror was established. Integrated analysis and response surface method were used in analysis and optimization of the designed parameters. The results show that the size limit of mirror for rear three mounting method is 1 m for the requirement of the axial self-weight deflection of wavefront error less than 1/10λ (λ=632.5 nm). The best mounting position was proposed, and the proper thick aspect ratio was given by 1/10. The accuracy of the proposed integrated parametric design method was analyzed, and the results show that the total analysis error is 6.13%. The method defines the proper size of rectangular mirror with rear three point mounting, gives the best mounting position and provides a standard for design of space remote sensors.Keywords：space optical remote sensor;space mirror;Rectangular mirror;Parametric design;integrated optimization;rear mounting- 54
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- 5
Published：2020-08-12 -
Application of WTLS in coordinate transformation of laser tracker
Abstract：The coordinate transformation algorithm of a laser tracker was investigated to solve the problem that random measurement error from the coefficient matrix of classical least square algorithm influences on transformation precision. The linear Errors-in-Variables(EIV ) model and Weighted Total Least Square (WTLS) were put forward and the form of indirect adjustment was used to solve the parameters of coordinate transformation in iteration. Simulation experiments using Matlab and practical experiments with API laser tracker were performed. The simulation results indicate that the average value and the standard deviation of mean square error of unit weight of WTLS are 4/5 and 1/5 times of those of traditional Weighted Least Square(WLS) respectively. The results of practical experiments show that mean square errors of unit weight of WTLS and WLS are 2.003 5 mm and 2.225 3 mm, respectively. These results verify that the WTLS achieves higher transformation precision and better stability than those of the WLS. Meanwhile, this method can provide the foundation for establishment of laser tracker measuring networks and optimization of network arrangement.Keywords：laser tracker;Weight Total Least Square(WTLS);Error-in-Variable(EIV) model;transformation precision;iterative algorithm- 75
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- 6
Published：2020-08-12 -
Design and test for large-diameter fast seal window
Abstract：As high-power laser launch system with large-caliber and multi-band has complex service environment and a long laser emission interval, and its crystal window can not meet use requirements, this paper designs an automatic shutter-type mechanical window for the laser emission system. The mechanical window consists of a Polyvinyl Chloride(PVC) sheet dust cover and a semi-permanent chute established by a spring and a pressure ring, driven by a stepping motor. Based on the large round plate deflection principle, it establishes the nonlinear differential equations for the deformation of dust cover and positive wind load. The center deflection perturbation is taken as the perturbation parameter to solve the differential equation to obtain the relationship between the dust deflection deformation and wind load and to further determine the motor load torque. Due to the certain motor load torque, the dust cover bending stiffness is optimized by using the relation between motor output torque and deformation to maximize capacity against the wind load. Experimental test shows that the solving error for the deflection of dust cover does not exceed 15%. When the thickness of the dust cover is 0.8 mm, it can resist 10 m/s wind load and the motor load torque is 0.34 Nm. The intervals of the window are stably from 2 to 3 s no matter it is opened or closed. This proposed window works reliably, satisfying working requirements.Keywords：opto-electro detection equipment;laser launch window;shutter-type mechanical window;round plate;positive wind load- 67
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- 1
Published：2020-08-12 -
Influence of restrictor structural parameters on load-bearing characteristics of Nanosys-1000 hydrostatic guideway
Abstract：On the basis of practical machining, influences of structural parameters of a restrictor on the load-bearing characteristics of hydrostatic guideway in the Nanosys-1000 ultra precision machine tool were analyzed. The fluid analysis software was used to establish the finite element model of a carrying oil pad and build a related hydrostatic guideway test bench. The pressure field distribution characteristics of the carrying oil pad when its inlet pressure was 1.7 MPa and the oil film thickness was 36 μm were researched. By integrating the pressure to get the oil film capacity, the oil film stiffness was obtained by derivation, and the effects of the different structural parameters on the load-bearing characteristics of hydrostatic guideway were revealed. The results show that the orifice diameter has the greatest impact on the load-bearing characteristics of the ultra precision machine tool, followed by the orifice hole length, while the entrance and export chamfers have little effect on it. When the guide load is lower, expanding the orifice diameter and shortening the hole length can help to improve the load-bearing characteristics of the hydrostatic guideway. However, narrowing the orifice diameter and increasing the length of the orifice hole would be more favorable. As compared with the simulation data and the experimental ones, data errors of three capacity measuring points are 7.9%, 6.9%, 8.6%, respectively. Finally, according to research results, the restrictor structural parameters of hydrostatic guideway in the Nanosys-1000 ultra precision machine tool were determined.Keywords：ultra-precision machine tool;restrictor;structural parameter;hydrostatic bearing;pressure filed distribution;load-bearing characteristics- 62
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Published：2020-08-12 -
Application of modified sensitivity matrix method in alignment of off-axis telescope
Abstract：To calculate the misalignments of optical elements accurately in an off-axis Mersenne afocal Cassegrain telescope, a computer-aided alignment method based on modified sensitivity matrix model was proposed. The principle and limitations of conventional sensitivity matrix method were analyzed. By means of adding a quadratic correction term to conventional sensitivity matrix model, the conventional computer-aided alignment technology was improved. For the off-axis telescope, the aberration characteristics were analyzed when the secondary mirror was misaligned. The modified model and conventional model were used to approximate the mapping relationships between misalignments and aberrations. Then the alignment of misaligned telescope was simulated. The simulation results in the range of decenter ±8 mm and tilt ±1.5° for a secondary mirror show that the root mean square error of x-,y-,z-decenters and α-,β-tilts of the secondary mirror calculated by conventional method are 2.689 mm, 2.494 mm, 0.194 mm and 0.500°, 0.525° respectively, and the corresponding calculations by modified method are 0.404 mm, 0.323 mm, 0.047 mm and 0.064°, 0.065° respectively. The calculation accuracy of the modified sensitivity matrix method is much higher than that of the conventional method. Finally, the telescope is well aligned with the modified method, and the results give that the Wavefront Errors(WFEs) RMS on axis is 0.056λ(λ=632.8 nm),while the WFEs RMS(Root Mean Square) in marginal field of view are better than 0.1λ.The results meet the design requirements.Keywords：off-axis telescope;computer-aided alignment;sensitivity matrix;misalignment;Zernike coefficient- 63
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Published：2020-08-12 -
Flowfield and flow rate properties of valve-less piezoelectric pump with flow-facing angle hemisphere-segment group
Abstract：The fluid delivery and fluid mixing functions of a valve-less piezoelectric pump by taking a hemisphere-segment group as no-moving part valve were researched. The influences of flow-facing angle θ change on pumping and mixing performance of the valve-less piezoelectric pump were simulated and verified experimentally. For the flow-facing angle changes in the range of 0°≤θ≤90°, several kinds of finite element models were established and the change laws of velocity field, pressure difference, flow resistance coefficient and flow rate caused by different flow-facing angles of hemisphere-segment group were simulated. The results show that when 0°≤θ≤45°, the simulation flow rate increases with the increasing of θ; when 45°<θ≤90°, that decreases with the increasing of θ, and when θ≈45°, that reaches to the maximum value of 96.13 mL/min. Meanwhile, the change laws of vortex size and strength caused by the change of flow-facing angle are the same as the simulation flow rate. The experiments on pumping flow rate with pump prototype verify the simulation results, the experimental flow rate reaches to the maximum value of 67.90 mL/min at θ≈45° the change trends of experimental and simulation flow rates are the same at the range of 0°<θ≤360°. During the flow-facing angle changes in a cycle, the flow rate and vortex strength reach to their forward and reverse maximum values twice respectively. The research in this paper lays a foundation for pumping performance optimization and fluid mixing delivery.- 46
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Published：2020-08-12 -
Influence of gravitation on moving mirror system in Fourier transform spectrometer
Abstract：The effect of space weightlessness on the moving mirror system in a Fourier transform spectrometer(FTS) was analyzed. Aiming at two critical factors of gravitation influence on the moving mirror system, solution schemes were put forward, and a validation method in the laboratory was designed. By taking different ground and space environments into account, the influences of gravitation on the moving mirror initial position without a driver and the restoring moment of moving mirror frame with the driver were analyzed. The initial accurate mechanical limit that allows moving mirror motion on a fixed starting point was designed. Then, a control strategy in combination with closed loop PID control and adjustable expected motion law was used to reduce the influence of restoring moment of moving mirror frame. Finally, the moving mirror mechanism of FTS was placed in up-down mode for ground validation. To obtain the bias of positive displacement and negative displacement of the moving mirror and the speed vibration in the uniform area, a test system was established. Experiments show that the bias of positive displacement and negative displacement for the moving mirror motion is less than 6 μm,and the speed vibration(RMS values) tested on upright and up-down frames are respectively 1.4% and 1.1%. The design satisfies the performance of FTS in simpleness and reliability, and provides a application technology for moving mirror systems in space.Keywords：Fourier transform spectrometer;moving mirror system;weightlessness;position of zero optical path difference;mechanical limit;closed loop control- 66
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Published：2020-08-12 -
Error compensation of optical freeform surfaces in fast tool servo diamond turning
Abstract：Fast Tool Servo(FTS) diamond turning technology usually can not obtain satisfactory optical freeform surfaces by one-step turning because many error factors will drop the fabrication accuracy of freeform surfaces. Therefore, a higher precise contact in-side measuring method for freeform surfaces was proposed by using a Linear Variable Differential Transformer(LVDT). By combination with a two DOF fast tool servo system, the error compensation technology for optical freeform surfaces machined by fast tool servo diamond turning was implemented to enhance the fabrication accuracy. The experiment results show that the form accuracy has improved by 20% and surface roughness decreased by 18.1% with the proposed error compensation technology. This technology solves the synchronization between FTS system and tool movement, compensates movement errors in xyz directions of the machine tool and can used in correction of the machining errors of freeform surfaces. Moreover, it can be used to cut the large asymmetry surfaces and brittle materials, so that promotes the applications of high precision freeform surfaces.Keywords：optical freeform surface;fast tool servo;diamond turning;machining error;in-sit measurement;error compensation- 63
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Published：2020-08-12 -
High precision orientation of faint space objects
Abstract：A high precision orientation method for faint space objects was presented to improve the positioning accuracy of this kind of space objects in photoelectric reconnaissance. Several relevant algorithms were investigated, such as star centroid computing, star pattern matching, correction models for static pointing of optoelectronic telescope, and the astronomical orientation of space objects. The star centroid computing method and star identification using triangle algorithm were firstly analyzed. Then, the Tycho-2 catalog and basic parameter pointing model were used to correct the static pointing error of the optoelectronic telescope. Finally, by considering lower orientation precision of faint space objects, the high precision orientation algorithm of faint space objects was presented based on the improved traditional astronomical orientation method to realize the high precision orientation of space objects. Experimental results indicate that the measuring precision of the high precision orientation method for faint space objects is superior to 4", which satisfies the system requirements of faint space object surveillance for the precision and stabilization.Keywords：faint space object;star pattern matching;astronomical orientation;Charge Coupled Device(CCD)- 75
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Published：2020-08-12 -
Ultrasonic echo signal modeling and identification for minor defects in metallic materials
Abstract：To identify the minor defect echo from ultrasonic testing signals containing the noise of metallic materials, an ultrasonic echo signal model was established and a minor defect echo identification method was put forward. The composition of ultrasonic pulse echo signals with minor defects obtained from metallic materials was analyzed, and then optimized ultrasonic echo model was established based on the Gaussian echo theory and a scattering sound field. The identification method for echo locations of ultrasonic minor defects was designed. By proposed method, the ultrasonic pulse echo signal was first denoised. Then the pulse signal from a probe was taken as the reference signal and the correlation coefficient between reference signal and denoised signal was piecewise calculated. Finally, the correlation coefficient sequence was processed by threshold method and the location of flaw echo in the ultrasonic echo signal was obtained. The simulation signal and frequency spectra generated by the optimized ultrasonic echo model were compared with those of experimental ultrasonic signal. The experiment results show that the time and frequency domain features of the two signals are in good agreements. When the threshold is set as 60 percent of the max value of the correlation coefficient sequence, the minor flaw echo can be accurately identified from the ultrasonic echo signals of metallic materials.Keywords：metallic material;minor defect;ultrasonic pulse echo signal;echo model;correlation coefficient- 64
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Published：2020-08-12 -
Design and validation of ballistic missile midcourse penetration trajectory
Abstract：For the ballistic missile midcourse penetration trajectory, this paper presents a new trajectory design optimization and evaluation method. Based on search and extended node in trajectory planning, the pulse ignition point in a multi-pulse trajectory was taken as a node and a multi-pulse maneuvering orbital transfer model was established. According to the model, the penetration trajectory was designed and optimized.Then, by taken the detection mechanism, performance, deployment of the enemy defense system into account, the prediction error between enemy prediction trajectory and real trajectory was as the evaluation index of penetration trajectory to reduce the prediction accuracy of enemy missile based on “game theory”. Finally, a ground verification platform for missile penetration effectiveness was designed to verify the validity of the penetration efficiency and trajectory evaluation method for the designed trajectory. As compared with the minimum energy trajectory, the experimental results show that the prediction error of ballistic missile defense system has increased by 5 to 15 times, reached 100—300 km, flight time is shortened by 8.53%, and the planning time is less than 140 s. These results show that the trajectory design method proposed in this paper can plan a ballistic with very high penetration probability in a short time.Keywords：ballistic missile;multi-pulse ballistic trajectory;trajectory planning;genetic algorithm;Kalman filter- 75
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Published：2020-08-12 -
Medical image registration based on salient texture
Abstract：Traditional registration methods based on geometric measurement can not match the medical image with local deformation. To solve the problem, an improved Iterative Closest Points (ICP) algorithm about human visual cognitive process is proposed base on the salient texture.Firstly, the method establishes the model for the salient texture feature of a medical image based on Active Appearance Model(AAM )algorithm, and it gives the feature point with more salient for a larger weight to complete the image match in the first step. Then,it introduces the salient texture distance to the traditional space distance. By simulating the human visual cognitive process proposed by Gestalt, the linear decreasing weight is used to balance the two kinds of distance measuring methods. With the algorithm, a whole registration is obtained by the geometric distance in the early stage. On the other hand, the feature points of local deformation are accurately registrated with the texture features in the later stage. At last, a series of experiments are performed on real live images.The experiment results show that the algorithm can get a good matching result, and the registration accuracy is 78.82%, increasing by 22.22% as compared with those of other popular algorithms. The experimental results also show that it is not sensitive to the rotation of the images. It concludes that the algorithm solves the registration problems of local deformation in medical organs and achieves higher precision and stronger robustness.Keywords：salient texture;medical image;image registration;Iterative Closest Point(ICP) algorithm;vision cognition- 68
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Published：2020-08-12 -
Feature preserving point cloud simplification
Abstract：3D scanning devices generally produce a large amount of dense points. This paper presents a feature preserving point cloud simplification method to reduce redundant points while preserving original geometric features well. Firstly, K-mean clustering algorithm was employed to globally gather similar points in a spatial domain. By constructing a K-d tree structure for the point cloud, some nodes of the K-d tree were used as initial clustering centroids. Then, normal vector of point cloud and candidate feature points were estimated with principal component analysis method. Traversing every cluster, if feature points were contained in the cluster, the cluster was subdivided into a series of sub-clusters and the cluster was mapped to a Gaussian sphere. Finally, adaptive mean shift algorithm was employed to classify the data in Gaussian sphere and the clusters in Gaussian sphere were corresponded to the sub-clusters in the spatial domain. The cluster centroids present the simplification data. Several real object models were used to verify the effectiveness of the proposed method. The experiment results demonstrate that the proposed method generates sparse sampling points in flat areas and high density points in high curvature regions. As comparing with the non-uniform grid, hierarchical agglomerative, and K-means methods, the proposed method obtains the smallest simplification error and preserves original geometric features.Keywords：point cloud simplification;principal component analysis;K-mean clustering;mean shift;Gauss mapping- 68
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Published：2020-08-12 -
Super-resolution imaging of multi-frame sub-pixel images based on self-learning LLE
Abstract：A super-resolution technology of combining hardware and software was researched. Firstly, the detector scanning was used to obtain multiple images with the same scene produced by different motion parameters and they were chosen to be training sets and input images. In consideration of that traditional Local Linear Embedding(LLE) super-resolution technology is over-relying on external training images and is inconvenient for processing image directly, a improved self-learning algorithm based on the LLE was proposed. The new LLE weight calculation method was proposed to obtain initial estimation of HR image. Meanwhile, self-learning LLE algorithm was used to recover lost high-frequency information of initial estimation and to obtain the final estimation. Simulation results show that the Peak Signal to Noise Radio(PSNR) of the reconstructed image by proposed algorithm improves 0.8 dB and operation time shortens by 75% as compared with those of conventional LLE method, respectively. Moreover, in the real scene experiment of micro-displacement platform, the Signal to Noise Radio (SNR) and information entropy of the reconstructed image by proposed algorithm have also greatly improved as compared with those of other algorithms. The algorithm provides high quality reconstruction image and improves the resolution of the captured image.Keywords：super-resolution imaging;sub-pixel image;Self-Learning;Local Linear Embedding(LLE);training set- 60
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Published：2020-08-12 -
Liver segmentation in CT image based on priori sparse dictionary and hole filling
Abstract：For complicated liver images, this paper presents a three-dimensional automatic liver segmentation method based on sparse dictionary and hole filling technologies.The Gabor feature of an abdominal CT image was extracted. The image blocks with the same size on the border of liver gold standard in Gabor images and CT images were selected as two groups of train sets. Then, the training sets were used to get the dictionaries and sparse coding. The golden standard image was registered with the image to be segmented, and registered liver boundary was taken as the initial liver boundary of the image to be segmented. Furthermore, two sets of images with the same size were selected as the training sets in ten neighborhoods on the initial boundary. The sparse coding and image reconstruction error were computed by using the testing sets and the block-sparse dictionary, and the final liver boundary with the smallest image reconstruction error was obtained. Finally, a hole filling method was designed for liver boundary completion and smoothing to obtain the final segmentation results. The proposed method for the liver segmentation was evaluated by using the data sets of MICCAI 2007. The results show that this method has better segmentation applicability and robustness for the liver. It shows a higher segmentation accuracy, the volume overlap error rate is reduced to 5.21±0.004 5, the relative volume error is 0.72±0.001 2, and the average symmetric surface distance error is reduced to (0.93±0.14) mm.Keywords：Computed Tomographic(CT) image;liver segmentation;sparse coding;dictionary learning;hole filling- 65
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Published：2020-08-12 -
Extracting heart rate from visible spectrum video based on diagonal cumulant algorithm
Abstract：Photoplethysmography(PPG) signal is usually acquired from a video image by using the classic Joint Approximate Diagonalization of Eigenmatrices(JADE) algorithm, and the heart rate is extracted from PPG signal using Fast Fourier Transform. However, the obtained value has larger deviation with the actual heart rate value. To improve the accuracy of measured results, a new blind source separation algorithm was proposed. The algorithm used diagonal cumulant to separate the PPG signal, and took the Fast Fourier Transform to extract the heart rate. Experiments were carried out by utilizing visible spectrum color video. Compared with the JADE algorithm, the results show that statistical parameter values of the absolute difference between heart rate values extracted from the diagonal cumulant algorithm and the actual heart rate values are decreased. The mean value, standard deviation, and root-mean-square deviation has reduced by 1.46,4.98 and 4.49,respectively. By analytical form of the Bland-Altman graph, the floating range of diagonal cumulant algorithm reduces more than twice as compared with the JADE method in a 95% confidence interval. It suggests that diagonal cumulant algorithm provides higher estimated accuracy, and relies less on intensity of skin and natural light. The calculation time can also be controlled less than 1 s after dramatically reducing the iterations by adjusting the parameter values in diagonal cumulant algorithm, which meets the demand of real-time electrocardiogram signal extraction.Keywords：Photoplethysmography(PPG);heart rate detection;diagonal cumulant algorithm;Joint Approximate Diagonalization of Eigenmatrice(JADE)- 77
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Published：2020-08-12 -
Multiscale segmentation-based sparse coding for hyperspectral image classification
Abstract：For the sparse representation of hyperspectral characteristics, a spatial weighted algorithm based on multiscale segmentation is proposed for hyperspectral classification. The algorithm uses a more reasonable neighborhood definition to mine spatial prior information to optimize the sparse representation of a like-edge pixel. Firstly, spatial neighborhoods were obtained through multiscale segmentation, and Laplacian Scale Mixture, (LSM) priori was then combined for the spatial-weighted sparse representation of pixels in each neighborhood. Then, the probabilistic Support Vector Machine(SVM) was used to classify the hyperspectral images and to provide classification labels and their confidences. Finally, the multiscale segmentation was weighted by the confidence of each label and the classification map was obtained by the fusion of labels. Experiments show that the algorithm enhances the sparse and roughness characterized by spectral features and improves the classification accuracy. Under smaller sample training, the classification accuracy of single ground surface has increased by 30%,which verifies the practicability of the proposed algorithm in hyperspectral applications.Keywords：hyperspectral image classification;spectral sparse representation;spatial prior fusion;multiscale scheme- 55
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Published：2020-08-12 -
Feature matching electronic image stabilization based on binary robust invariant scalable keypionts
Abstract：To overcome the instability of video sequences caused by attitude changes and jitters of a projectile in the strapdown image guidance system, a robust high-precision fast electronic image stabilization algorithm based on Binary Robust Invariant Salable Keypoints(BRISK) was proposed. Firstly,the BRISK algorithm was used to extract BRISK feature descriptors of the image. To improve the matching accuracy and speeds, the mutual matching strategy was adopted to realize BRISK matching feature point tracking. Then, the improved Random Sample Consensus (RANSAC) method was used to eliminate the false matching points.Finally, the Least Square Algorithm (LSA) was taken to estimate the global motion parameters to realize image stabilization. The standard image matching test and real video shoot image results show that the strapdown image guidance stabilization technology based on BRISK algorithm can provide short processing time less than 30 ms and high positioning accuracy of 0.1 pixel. Moreover,the technology has stronger robustness to changed illumination, noise and complex environment barrier and can quickly and effectively compensate complex random jitters and improve the quality of video images.Keywords：strapdown image guidance;video stabilization;motion estimation;Binary Robust Invariant Scalable Keypoints(BRISK);feature matching;Random Sampling Consensus Algorithm(RANSAC)- 65
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Published：2020-08-12 -
Three projective transformations for image stitching
Abstract：A three projective transformation image stitching algorithm was proposed based on local warping method combined with different textures of buildings and ground planes to overcome the image distortion and improve the stitching speed for the stitched building image with ground plane information. With the method, the image was first segmented into different small images with different contents, and then the ones with the same content were stitched together before finishing the whole stitching process. In order to reduce the local distortion and warping caused by globally projective transformation methods, the locally projective transformation method was adopted three times during the whole process. As the method stitches the image based on image content segmentation, it has a very precise and reliable stitching result than traditional ones. Experimental results show that the proposed method obtains seamless stitching image and overcomes the defects caused by image distortion due to less texture information of the ground plane, as well as improves the speed by 20%—40% as compared with that of traditional method. The rapid speed and high fidelity of proposed method satisfies the requirements of image stitching.Keywords：image segmentation;Image stitching;Hough transformation;projective transformation- 46
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Published：2020-08-12
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