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Issue 2 ， 2015
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Highly coupling efficient mode-field adaptors for high power fiber lasers
Abstract：To improve the coupling efficiency for a Large-mode-area Fiber (LMAF) and a Single-mode Fiber(SMF), a Thermally Expanded Core (TEC) technique was used to expand the core of SMF to implement the mode field adaptation for the LMA double clad fiber 15/130 μm and the SMF 6/125 μm.The transmission loss of the Mode Field Adaptor(MFA) made by TEC processing was analyzed theoretically, and a homemade MFA and a commercial MFA was respectively measured through a self-built fiber laser source with a 1 064 nm central wavelength. Experiment results show that the TEC technique dramatically improves the coupling efficiency of the MFA between the LMA and the SMF. In contract with the commercial MFA, the homemade MFA is capable of a higher operating power, better heat treatment capacity and better reliability. The homemade MFA offers the operating power up to 100 W, and accumulated working time up to 120 min in an air-cooled condition. Furthermore, its single-mode output to be 73 W, and heat treatment capacity to be 27 W. The improvement of the performance of MFA meets the needs of the development of high-power fiber components and are suitable for achieving all-fiber-integration systems of fiber lasers.Keywords：large mode area fiber;single-mode fiber;thermally expanded core;mode field adaptor;coupled efficiency- 74
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Published：2020-08-13 -
OCT based air jet indentation for corneal biomechanical assessment
Abstract：Spectral Domain Optical Coherence Tomography (SDOCT) and air jet indentation technology were combined to assess the corneal biomechanical properties. A corneal mold was designed to make eight different stiffness phantoms with the thermal forming method. The Intraocular Pressure (IOP) of phantom was regulated through a medicine flask and measured by a pressure sensor. The air jet excitation was applied to the cornea, and the corneal dynamic deformation was recorded to obtain corneal deformation parameter: maximum Deformation Amplitude (DA) with the OCT. Then the corneal stiffness coefficient (k) was calculated to represent the corneal biomechanical properties. The correlation of stiffness coefficient and Young's modulus measured by traditional strip extensiometry was analyzed and the accuracy of OCT based air jet indentation was assessed through the analysis of repeatability and consistency. The experimental results show that the central thicknesses of corneal phantoms are (504.12±17.04) μm and the Young's modules of corneal phantoms range from 90 to 1 400 kPa. Moreover, there is a positive correlation between the corneal stiffness and the IOP. The experiment at the same IOP shows that it is a high repeatability for three time measurements of corneal phantom by the OCT based air jet indentation system, in which the value of ICC is 0.992 6. The measurements of DA by observers A and B are high consistency(the Difference is 1.1 μm). The k value also exhibits a linear relationship with the Young's modulus measured by the strip extensiometry (r=0.99, P<0.001). In conclusion, this technology provides a potential non-invasive means for the assessment of corneal biomechanical properties.Keywords：air jet indentation;optical coherence tomography;corneal;biomechanical property- 54
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Published：2020-08-13 -
Recognition of optical fiber pre-warning system based on image processing
Abstract：To reduce the time-consuming and misinformation of one dimensional signal recognition by the pre-warning system in a Phase-sensitivity Optical Time-domain Reflectometer(Φ-OTDR), a new method to acquire two dimension signals by the Φ-OTDR pre-warning system and to recognize events based on Relative Vector Machine(RVM) classifier was proposed. Firstly, the spatial and temporal two dimension signal was taken as an image and the image processing method was used for the threshold segmentation of different events according to the image characteristics. Then, the proposed feature extraction method based on morphology was used to extract different signal features by using the amplitude, area, shape and internal of region as feature vectors. Finally, the RVM classifiers and "one to one" strategy were used for multi-class recognition. The experiments on three pipeline safety events show that the feature extraction method proposed in this paper greatly improves the recognition accuracy with less computation time, the accuracy has been reached to 97.8% and the computing time is less than 1 s. As compared with traditional methods, the algorithm has better performance, thus is very suitable for the pre-warning system online monitoring of Φ-OTDRs.Keywords：fiber optics;Optical Time-domain Reflectometer (OTDR);optical fiber pre-warning system;pattern recognition;morphology;feature extraction- 64
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Published：2020-08-13 -
Elimination of wavefront aberration introduced from large aperture collimator in detection of large optical device
Abstract：When a large aperture collimator is used to test large aperture optical devices or components, the error introduced by the collimator will effect the measuring accuracy. This paper proposes a new method to eliminate the error from optical test results. The method uses an interferometer to obtain wavefront information of the collimator and the optical testing system, and adopts 37 Standard Zernike Phase polynomials to fit the wavefront. The error introduced by the collimator is then separated by subtraction of two sets of coefficients and the true wavefront information of tested optical system is obtained by simulating the light cone of a real optical system using the simulation model of tested optical system established in ZEMAX. The feasibility of this method in large aperture optical testing is verified by using the optical system model in ZEMAX, and an experiment is performed by using a small collimator with a focal length of 1 597 mm and an aperture of 150 mm, as well as a camera lens with a focal length of 50 mm. The experiment results show that the calculated wavefront P-V error is less than 0.005λ and the RMS error is less than 0.001λ after eliminating collimator error as compared to the real tested optical system wavefront. It meets the accuracy requirement of testing optical systems for image quality parameters in a laboratory.Keywords：optical test;larger optical device;collimator;Aberration;error separation;Zernike polynomial;ZEMAX- 45
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Published：2020-08-13 -
Rapid identification of coffee bean variety by near infrared hyperspectral imaging technology
Abstract：Four different Chinese domestic coffee beans were identified rapidly by combining near infrared hyperspectral imaging technique and five kinds of discriminant models. A near-infrared hyperspectral imaging system covering the spectral range of 874-1 734 nm was set up to capture hyperspectral images of coffee bean samples. The head and end of the spectra with obvious noises were removed, and the spectral data in the range of 925-1 680 nm were extracted to establish discriminant models in the experiment. The sensitive wavelengths were selected from the full spectra by Successive Projections Algorithm (SPA). Five discriminant methods, including Partial Least Square-discriminant Analysis (PLS-DA), Random Forest (RF), K-nearest Neighbor algorithm (KNN), Support Vector Machine (SVM) and Extreme Learning Machine (ELM) were applied to the establishment of discriminant models based on the full spectra and the selected sensitive wavelength variables. The properties of the models were compared and valuated by three parameters, sensitivity, precision and specificity. Among all discriminant models, the ELM models based on the full spectra and the selected sensitive wavelength variables show the best identification results, respectively. For each coffee bean cultivar, the sensitivity, precision and specificity of ELM models based on full spectra and the sensitive wavelengths are all over 93.5% in both the calibration set and the prediction set. It concludes that Chinese domestic coffee beans could be identified by near-infrared hyperspectral imaging combined with discriminant models rapidly. Selecting the sensitive wavelengths reduces variables, but the identification effect is the same as that of the full spectra.Keywords：near-infrared hyperspectral imaging;coffee bean;non-destructive identification;discriminant analysis model;extreme learning machine- 76
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Published：2020-08-13 -
Radiation calibration of infrared system by amendment of inner and outer calibrations
Abstract：As the existing radiation calibration for a shortwave infrared system with large aperture needs a huge infrared collimator and has poor motility and cost much, this paper proposes a new calibration method based on the amendment of inner and outer calibrations. This method sets a middle-high temperature cavity blackbody in the infrared system. By switching a mirror, it introduces the blackbody radiation into the infrared system to implement the inner calibration on parts of system at the middle-high temperature range. Then it uses a huge area blackbody to implement the outer calibration on the whole system at middle temperature range. The inner and outer calibration data at the common temperature range are picked up to calculate the amendatory coefficient in whole system. Finally, the radiation calibration data for whole system at the middle-high temperature range are captured by amending the inner calibration data. With this method, an Φ400 mm infrared system is calibrated, and the luminance error and temperature error are inverted based on the calibration results. The results show that the maximal luminance error is 1.67% and the maximal temperature error is 1.02 ℃. The results indicate that the proposed method is precise and effective for the radiation calibration of shortwave infrared systems with large apertures.Keywords：infrared measuring system;shortwave infrared;radiation calibration;inner calibration;outer calibration;radiation inversion- 50
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Published：2020-08-13 -
Measurement of space coordinates in hidden parts by combining non-diffracting attitude probe and total station
Abstract：A non-diffracting beam based probe was proposed, then the probe was integrated with a total station to form a combined measurement system for measuring space coordinates of hidden parts in a large-scale space. The constructs and principles of the optical probe for measuring spatial attitude and the combined measurement system were introduced,and the mapping relationships between the centre position of non-diffracting and the incident angle of laser was established. In the combined measurement system, the probe stylus was first set to touch the point of measurement, and the optical system of the probe was targeted by the total station or the laser tracker to measure the spatial coordinates of the probe. The laser beam to measure the distance was transformed into a non-diffracting beam through the axicon lens, and CCD images were produced. The center of the non-diffracting beam was mapped one to one to the incident direction of the laser, and the horizontal angle and the pitching angle of the probe were obtained via center fitting of the non-diffracting images. Finally, an inclinometer was used to measure the rolling angle of the probe, and the spatial coordinates of the measured point were obtained by combing all the measured attitude angles with the position coordinates and coordinate transformation. Experimental results indicate that the precisions of probe's attitude-measuring system and combing measurement system are 1 mrad and ±1 mm, respectively, which demonstrates that the combined system is more flexible and reliable and meets the measuring demands of space coordinates of hidden parts in large-scale spaces.Keywords：coordinate measurement;non-diffracting probe;total station;laser tracking instrument;hidden part- 75
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Published：2020-08-13 -
Rapid detection of oil yield of oil shale by combination of wavelengths in near infrared spectroscopy
Abstract：To detect rapidly the oil yield of an oil shale on a single point measurement, a detection method was proposed based on combination of wavelengths by a portable near infrared spectroscopy. By taking the kaolin mixed with oil simulating samples as the research object, how to select the combination of wavelengths by near infrared spectroscopy was performed. With proposed method, the full spectral reflectivity data were firstly acquired by the developed portable spectrometer. Then the preliminary selection for the combination of wavelengths was implemented by differential multiplicative scatter correction method and correlation coefficient method, and the optimum combination of wavelengths was determined by combination generation method and leave one cross validation Multiple Linear Regression (MLR). Finally, the data for the optimum combination of wavelengths were verified by MLR modeling. The results show that the optimum combination of wavelengths is 1 644,1 720,2 210 and 2 260 nm, and the determination coefficients for calibration set (Rc2), prediction set (Rp2) of 30 modeling samples and validation (Rp2) of 11 validation samples are 0.995 4,0.997 7 and 0.990 1, respectively. The method provides a basis for design of a rapid detecting spectrometer in oil yields of oil shapes.Keywords：Near-infrared spectroscopy;oil shale;oil yield;combination of wavelengths;leave one cross validation;multiple linear regression- 55
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Published：2020-08-13 -
Reflection process of fast-steering mirror of laser launching system
Abstract：The reflection process of the fast-steering mirror in an electro-optical tracking system was researched to improve its tracking precision. Firstly, the relationship of the turning angles between fast-steering mirror and reflection light was deduced, and the control method of the fast-steering mirror system was expatiated in detail as well as the software realization. Then, by taking the relationship mentioned above for the thesis, a servo control system for the fast-steering mirror was established. Furthermore, zero-locked and tracking experiments were performed to verify the performance of the control system, and the experimental results for the fast-steering mirror system and the main shafting system were compared. Obtained results indicate that the fast-steering system has fast-response and high-precision, and the residual error is less than 1" in the zero-locked experiment. Moreover, the Root Mean Square (RMS) error of azimuth tracking in the fast-steering system is 3.6" and the RMS error of elevation tracking is 8.7" in the tracking experiment, which meets the requirement of tracking system for the tracking speed and pointing precision. The conclusion is that the servo system for fast-steering mirror based on the thesis on reflection process is characterized by high precision and fast response.Keywords：opto-electro tracking;laser launching system;fast-steering mirror;reflection process;voice coil actuator- 93
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Published：2020-08-13 -
Estimation and measurement of signal-to-noise ratio for aviation multi-angular polarimetric radiometer
Abstract：To estimate the performance of an Aviation Multi-angular Polarimetric Radiometer (AMPR) precisely, its signals and noise were analyzed and the estimation processing for signal-to-noise ratios (SNRs) were investigated. The working principle of the AMPR was introduced and the formulas to calculate the detector SNRs and system SNRs were inferred. It indicates that the system SNR is proportional to intensity SNR while the requirement of detector SNR is inverse proportional to the polarimetric accuracy. However, the detector SNRs of AMPR should not be less than 245. The results make up the shortcoming from the traditional method that the precision of the polarization remote sensing instruments depends only on the detector SNRs. Finally, the system SNRs and the detector SNRs in a typical scene simulated by vector radiative transfer were estimated with the inferred formula and tested by a Spherical Integrating Source (SIS) and a polarization box in a dark laboratory. The results show that the SNRs of the AMPR detector meet the requirements of polarimetric detection.Keywords：aviation remote sensing;polarization radiometer;multi-angular polarimetry;Signal-to-Noise Ratio(SNR)- 52
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Published：2020-08-13 -
Infrared MWIR/LWIR dual-FOV common-path optical system
Abstract：In consideration of the serious chromatic aberration and lower energy transmittance of a multi-band infrared MWIR/LWIR(Medium Wave Infrared/Long Wave Infrared) dual-FOV(Field of View) common-path optical system, a dual-FOV and dual-band common-path refraction optical system is designed to implement the multi functions of the imaging system. The system is based on a cold 320 pixel×240 pixel MWIR/LWIR dual-band staring focal plane array detector and introduces aspherical optical components to improve its aberration correction ability to adjust the align structure of lenses. The optical system is made up of a zoom subsystem and a secondary imaging subsystem with a 50 mm focal length and a 200 mm focal length and satisfies 100% cold shield efficiency. The image evolution shows that the Modulation Transfer Function(MTF)of LWIR and MWIR is almost reaching the limit of diffraction and greater than 0.5 respectively at the spatial frequency of 17 lp/mm, and almost 80% of the energy is concentrated at one pixel. In addition, there is no obvious cold reflect phenomena observed, and the optical system has a preferable application foreground in military and civilian opto-electronic detective fields for its wide scopes of application, compact structure, small volume and good imaging.Keywords：optical design;infrared system;dual-FOV system;dual-band system;common-path system- 50
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Published：2020-08-13 -
Selection of MCP for array X-ray pulsar navigation detector
Abstract：According to the demands of an array detector in the X-ray pulsar navigation system for Micro-channel Plate(MCP), a selection method for the MCP was explored. Four key parameters for the selection of MCPs, the uniformity of gain, impedance matching, dark count rate and the gain coefficient were determined. Based on the four key parameters, corresponding experiments were designed and the selection process of MCPs was set out. The amplitudes and counting rates of MCPs selected by proposed method were tested. The tested results show that the relative error of each detection unit is not identical. When a single channel anode is used, the ranges of the maximum relative error Δ1i and minimum relative error Δ2i of the amplitudes for output signals from the ith anode are 7%-13.5% and 3%-6.7%, respectively, and when a four-channel anode is used, Δ1i and Δ2i are 7.8% and 3.1%, respectively. Moreover, the relative error between the anode count rate n1+n2+n3+n4 from the single channel and N from the four-channel shared anode is 4.38%, less than 10%. Obtained results indicate that the MCPs with good performance have been effectively chosen by the proposed selection method.Keywords：single photon detection;X-ray detector;pulsar navigation system;Microchannel Plate(MCP);MCP selection;pulse amplitude;count rate- 36
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Published：2020-08-13 -
Transient effect of dead time of photon-counting in micro-pulse lidar
Abstract：A photon counter model was established to analyze theoretically and measure actually the effect of dead time of the photon counter in a micro-pulse lidar. A correct method for the influence of photon-counting on micro-pulse lidar signals was proposed. The Markov chain was used to theoretically describe the detection process of the photon counter in the micro-pulse lidar theoretically. Then, the influence of dead time on photon counting was calculated based on MATLAB, and the transient morphological changes of the results due to the dead time of photon counting were described. After the theoretical analysis and computer simulation, a photon counting platform based on micro- pulse lidar was performed to illustrate the effect of the dead time on counting photons. Finally, the effect of the dead time was measured under different light intensities, and the correction method of the micro-pulse lidar signal was given. A correction experiment was carried out based on the proposed method. The results show that the effect of photon counting on the scattering light has been reduced by 50%. It concludes that the proposed method has well explained the signal shapes of small targets and achieves the correction of the detection results of photon counts.Keywords：micro-pulse lidar;photon counting;dead time;transient effect;Markov chain- 38
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Published：2020-08-13 -
Online measurement of coupled error angle between different axes of electrostatically suspended accelerometer
Abstract：The coupled angles between different axes of an Electrostatically Suspended Accelerometer (ESA) are related to the parallelism error of a sensor head, and it is hardly measured accurately by using classical methods. Therefore, a novel online measurement method for the coupling angles was proposed by a varying preload voltage. By modeling the relationship of the parallelism error, coupled angle, attitude angle and the electrostatic force coupled angle, the mechanism and equation of the varying preload voltage method for online measurement of the coupled angles were given. A ESA prototype was designed and then it was used to verify the proposed method. Experiment results show that the coupling angles of X/Y and X/Z are -5.10×10-4 rad and 2.36×10-5 rad, respectively, which are consistent with that of theoretical analysis. The method is also suitable for online measurement of the coupling angles for Y/X, Y/Z and Z/X,Z/Y. The result shows that this novel varying preload method can online identify the coupled angles of different axes of ESA effectively and accurately.Keywords：electrostatically suspended accelerometer;coupled error angle;attitude angle;varying preload;online measurement- 57
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Published：2020-08-13 -
Subspace identification for dynamically tuned gyroscope
Abstract：To deal with the problems of complex structure parameters, unknown interference factors and lower modeling precision in the Dynamically Tuned Gyroscope (DTG) mechanism modeling by the traditional Subspace Identification Method(SIM), an improved SIM was proposed. Firstly, the DTG state space model sets were determined and DTG inherent colored noises were discussed. Then, the traditional SIM were modified for the colored noise problem and the orthogonal projection of a data Hankel matrix was used to eliminate the SIM bias of traditional method. Finally, a confidence ellipse was introduced in the numerical simulation to analyze the statistics feature of the modified algorithm. Simulation results indicate that the identified results of modified algorithm are unbiased at different colored noise influences, and the variance is related to the noise strength and data length. The identification experiments show that the identification performance of modified SIM is apparently better than that of the traditional SIM, and the identification fitting degree is more than 90%, which means that the modified algorithm is suitable for the DTG system modeling.Keywords：Dynamically Tuned Gyroscopy(DTG);Subspace Identification Method(SIM);orthogonal projection;colored noise- 81
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Published：2020-08-13 -
Online compensation of thermal error for dual direct feed drive system with latent variable model
Abstract：The thermal error from a dual direct feed axis driven by linear motors was analyzed and the error compensation method was proposed to improve the accuracy of the system movement. The causes of thermal error generation in the motion processes and the complexity of the compensation were discussed. And then a compensation method based on Latent Variable Regression(LVR) was applied to improvement of the positioning accuracy of the feeding axis. With the method, a laser interferometer was utilized to obtain the thermal deformation of the feed axis in real-time. Some thermocouples and infrared thermometers were used to measure the temperatures of some key points at the linear axis. A regression model based on latent variable model was established to recognize the thermal deformation behavior of the mechanism. The prediction magnitude for on-line error compensation was acquired through the real-time regression calculation and a corresponding system was developed with output control strategy for the compensation process. To demonstrate the procedure of the proposed approach, an experiment was conducted on the self-construction gantry double direct feed axis test rig. the experimental results show that the method for thermal deformation error compensation reduces the linear feed axis thermally induced error by 75%.Keywords：linear motor;direct feed axis;thermal error;latent variable model;online compensation- 65
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Published：2020-08-13 -
Application of Bipod to supporting structure of minitype reflector
Abstract：A flexible supporting structure composed of 3 Bipods was designed to enhance the surface accuracy of a minitype reflector in complex environments. Firstly, the flexibility matrixes of the Bipods and whole support structure were established through matrix transformation and the defining design variables of the Bipods were optimized through MATLAB to meet the requirements of maximum of the axial stiffness when the radial stiffness was minimum. The simulation verification was then performed by applying different forces and thermal loads to the optimized supporting structure. Finally, a zygo interferometer was employed to verify the thermal stability of the supporting structure. The results show that the Bipod support structure keeps a fine surface accuracy under a thermal-structural load,meanwhile providing excellent dynamic performance. Except for giving the reflector a better thermal stability, the support rigidity of the structure resists the impact of the environmental dynamic load on the reflector. Moreover, the analysis indicates that the first order natural frequency of the flexible supporting structure is 1 781.7 Hz, and the relative error is 1% as compared with that of the theoretical calculation.Keywords：minitype reflector;Bipod;flexible supporting structure;flexible matrix;optimum design- 57
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Published：2020-08-13 -
MEMS based broadband electrochemical seismometer
Abstract：On the basis of Micro-electro-mechanical System(MEMS), a broadband electrochemical seismometer was developed. The structure parameters related to the seismometer were analyzed and a developing scheme based on MEMS technology was presented to extend the frequency band of the seismometer to a wider range. The effects of the lengths of insulating spacers and the pore widths in cathodes on the seismometer property were discussed by numerical simulation and the optimized structure parameters were obtained. Then, according to simulation results, the Su-8 series photoresist and a silicon wafer were applied to fabrication of spacers and electrodes with optimized sizes. These devices were packaged via a physical fastening method to avoid the leakage of electrolyte. Finally, the device characteristics were measured through frequency response test on a horizontal vibration platform and a micro seismic monitoring experiment was performed on the bedrock. Test results without frequency compensation demonstrate that the frequency band of the device packaged with spacers with thickness of 200 μm and cathodes with wide pores of 20 μm has reached 3-90 Hz, the fade degree at 60 S is less than 30 dB, and the seismometer's dynamic range is no less than 130 dB. This improved seismometer may function as a detecting device covering a wide frequency range in the marine oil exploration.Keywords：Micro-electro-mechanical System(MEMS);electrochemical seismometer;broadband;Su-8 insulating spacer- 69
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Published：2020-08-13 -
Mechanism and avoiding of polymer melting on non-forming surface during ultrasonic embossing
Abstract：This paper analyzes the reason why the polymer is melted on a non-forming surface during ultrasonic embossing and proposes a method to inhibit the polymer melting. On the basis of the heating mechanism of ultrasonic, it points out that the polymer melting phenomenon on non-forming surface is resulted by the friction in a horn-substrate interface. Then, it proposed the method "two interfaces of different friction coefficients" to inhibit the polymer melting and implemented the method by coatings surface protection films on the non-forming surface. To optimize the protection films, and the influences of the four coating film conditions on the softening time are examined through Taguchi method. The results show that the Sekisui #622E-50 film shortens the softening time by 3.4 s and the Sekisui #622WB film reduces the softening time error by 0.64 s. It demonstrates that surface protection films coated can avoid polymer melting on the non-forming surface, and improve the process replication ability and the process stability in ultrasonic embossing.Keywords：polymer;ultrasonic embossing;softening time;ultrasonic friction heating;melting on non-forming surface;surface protection film- 44
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Published：2020-08-13 -
Application of high order observer in EO stabilized platform
Abstract：As Electric-Optic(EO) stabilized platform is effected by the disturbance of friction, windage, unbalance and base motion in stabilizing a Line of Sight(LOS), this paper explores the mechanism and method to eliminate the disturbance torque by a high order observer. The observer is consist of an inverse system of the control object and a modified filter, and the modified filter is implemented by a high order design. The observer is used for observing the disturbance torque, then the current loop with a very high bandwidth is utilized to compensate the disturbance torque. The eliminating disturbance ability of the system is simulated.The results show that the high-order disturbance observer has the ability to eliminate the high-order disturbance model: the 3th order observer eliminates the disturbance by 100% for the step and ramp disturbance; and eliminates the disturbance by 99.9999996% for the parabola disturbance. Moreover, the observer also has good robustness to the perturbation of the control object. The method improves the response speed of the servo system meanwhile ensuring the robustness of the system, so that it satisfies the application requirements of the EO stabilized platform.Keywords：electro-optical stabilized platform;disturbance torque;high-order disturbance model;high-order disturbance observer- 78
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Published：2020-08-13 -
Theory and experimental modal analysis of dual-mass vibrating silicon micro-gyroscope
Abstract：For designing silicon micro-gyroscopes and optimizing their structures, the effects of intrinsic frequency and modal of a silicon micro-gyroscope on its performance were researched. On the basis of energy theorem, a theoretical formula of the intrinsic frequency was established, and the lowest frequency mode of the dual-mass vibrating silicon micro-gyroscope was analyzed. Then the analytical results were validated by the Finite Element Method (FEM) simulation and the experiment. Analysis results show that the largest analytical errors with respect to simulation and experiment are 8.6% and 10.6%, respectively. Moreover, the Allan Variance analysis was used to conduct a static performance experiment, and the results demonstrate that the Angle Random Walk (ARW) is 0.057 8(°)/hr1/2 and the measured bias instability is 0.459(°)/hr. As compared with the traditional modal ordering method depending on the FEM, the proposed theoretical model avoids complex structure parameter adjustment processing, complements modal ordering of the silicon micro-gyroscope and can be used in the structure optimization of the silicon micro-gyroscope.Keywords：dual-mass vibrating silicon micro-gyroscope;dynamic eigen frequency;energy theorem;modal- 56
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Published：2020-08-13 -
Modeling and parameter identification for electro-optical stabilized platform servo systems
Abstract：A separated model parameter identification method for electro-optical stabilized platform servo systems was presented. The model of servo systems was separated into a linear part and a nonlinear part. In the process of parameter identification of the linear model, a differential inverse M sequence signal was utilized to excited servo systems, and least square method was used to identify the parameters of the linear discrete model part to reduce the influence of the nonlinear dynamics. In the process of parameter identification of the nonlinear model, the coupling dynamics between friction and unbalanced mass was considered, and the static parameters of the LuGre model and the parameters of the unbalanced mass model were firstly identified by using the least square method; Then, the dynamic parameters of the LuGre model were obtained by friction measurement through a current signal. An experimental system for single-axis electro-optical stabilized platform was constructed, and the dynamic model parameters were indentifies by proposed method. Experimental results indicate that the identification value of unbalanced mass torque is 0.183 N·m, which is a little larger than the theoretic value 0.18 N·m, and satisfied with the identification precision. So the parameters of linear and nonlinear models can be obtained by the presented identification method.Keywords：electro-optical stabilized platform;differential inverse M sequence;LuGre model;unbalance mass;parameter identification- 55
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Published：2020-08-13 -
Small satellite maneuver based on terminal sliding mode control
Abstract：The attitude maneuver and stable task of a small satellite by using a Single Gimbal Control Moment Gyro(SGCMG) as an actuator was explored with the terminal sliding mode control method. Firstly, a small satellite mathematical model was established based on the Modified Rodrigues Parameters (MRP), and the torque planning was made in the terminal sliding mode control method. Then, command torque was given through diagonal singular robust tracking control law using the SGCMG as an actuator. The performance of the control method was studied by mathematical simulation, and the changing law and chosen rule of design parameters of the terminal sliding mode control were presented. Finally, a small satellite three-axis air flotation turntable was used to verify the adaptability of terminal sliding mode control. The experimental results show that the attitude angle and attitude angular velocity control precision and steady state error is less than 0.1 ° and 0.01(°)/s, which is within the scope of the best control precision from the parameter selection principle in the three-axis air flotation turntable for small satellite maneuver stability experiment. It concludes that the terminal sliding mode control method has high control precision and stability and is able to give a good function for small satellite maneuvers.Keywords：small satellite maneuver stability;terminal sliding mode control;Single Gimbal Control Moment Gyroscope (SGCMG);air flotation turntable- 45
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Published：2020-08-13 -
Wideband/low frequency piezoelectric vibration energy harvester based on pneumato-coupling
Abstract：A piezoelectric energy harvester based on Pneumato-coupling Piezoelectric Vibration (PHPV) was presented for the energy harvesting of low-frequency/high-level vibration and the self-powered active vibration control based on energy harvesting. The structure and working principle of the PHPV were introduced, and the energy harvesting performance was studied theoretically and experimentally. The theoretic analysis results show that the output performance of the PHPV depends on the vibration level/frequency, the structural size and material parameters of the cylinder/ piezodisc, proof-mass, backpressure, and so on. Under constant other parameters, there are an optimal frequency for the PHPV to generate a peak voltage and a minimal critical frequency for the PHPV to work normally. The increasing of proof-mass and backpressure can enhance the output voltage and bandwidth in different degrees, but exerts no influence on the optimal frequency. By a piezodisc with with piezodisc measured Ф 60×0.9 mm3 and cylinder measured Ф16×100 mm3, a PHPV prototype was fabricated and its voltage-frequency performance was tested at different backpressures/proof-masses. The obtained influence regularities of proof-mass/backpressure on the optimal-frequency/critical-frequency/maximal-voltage/bandwidth are in agreement with the analysis results. The optimal frequency almost is the same of 55 Hz at different test conditions. At given backpressure of 0.4 MPa and proof mass of 10 kg, the obtained critical-frequency/maximal-voltage/bandwidth relative to output voltage of 25 V are 9 Hz/88 V/72 Hz, which are 0.36/2/2.2 times those at 0.4 MPa and 10 kg, respectively.Keywords：piezoelectric vibration energy harvester;pneumato-coupling vibration;energy harvesting;electric energy generation- 46
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Published：2020-08-13 -
Simulation of thermal deformation of cylindrical mechanical parts bounded by boundary constraint based on conversion mechanism of thermal into mechanics
Abstract：An accurate analysis theory of thermal deformation and a simulation method were proposed to ensure the optimum performance of mechanical aparts affected by thermal errors. From the view of microscopic molecular mechanics theory, an analysis theory of conversion of thermal into mechanics for thermal deformation was put forward, by which the thermal deformation of a part was equivalent to the force deformation by taking the effect of material properties, temperatures and the boundary constraints of shape on thermal deformation into account fully. Then, measurement experiments of thermal deformation of hollow cylinder parts were carried out, and a simulation method of thermal deformation based on ANSYS Workbench was given. Finally, simulation and experiment results were compared. The results show that thermal expansion coefficients of the outer circle are approximately twice that of the inner circle in the radial direction when an aluminum alloy hollow cylinder part is deformated under a high temperature. Meanwhile, the simulation results based on the proposed theory are consistent with the experimental results very well and the fit is more than 98%, which validates the rationality of our theory. As the method makes up the drawback that traditional thermal analysis of ANSYS Workbench completely ignores the physical boundary constraints affecting part thermal deformation, it provides an important reference for the structure design of thermal robustness subsequently.Keywords：hollow cylinder;thermal deformation;conversion of heat into force;boundary constraint of shape;simulation analysis- 53
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Published：2020-08-13 -
Design and aerodynamic simulation of low Reynolds number rotor airfoil
Abstract：This research focuses on the thin circular arc rotor airfoils at a low Reynolds number. A novel thin circular arc airfoil with a convex structure was designed in consideration of its demand for high aerodynamic performance, high structural strength, lightweighting and easy manufacture. A convex curve on the upper surface of the airfoil was adopted to increase the thickness of airfoil at the partial chord and a stiffener in the airfoil was installed to improve the structural strength of blade span wise. The designed thin circular arc airfoil has the maximum thickness of 4.3%, a circular average thickness of 2.5%,the maximum camber of 5.5% and an average camber of 4.5%. Numerical simulations for computing the aerodynamic performance of the airfoil were performed at the representative Reynolds number between 40,000 and 100,000, and the angle of attack (AOA) from -4°to 12° by using the two dimensional steady and incompressible Navier-Stoke equations. The pressure coefficient distribution line of airfoil surfaces and the velocity vector were acquired. A carbon fiber rotor with a diameter of 40 cm, a mass of 15 g and rotor pitch of 15.7 cm was manufactured with the present airfoil, and the experiments on the lift force and the structural strength in a hover state were performed and the results show the performance of the airfoil meets the use requirments. At present, the developed rotor airfoil has been successfully used in a rotor aircraft.Keywords：low Reynolds number;airfoil design;aerodynamic performance;simulation- 52
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Published：2020-08-13 -
Target positioning in high power laser device
Abstract：A target positioning method based on simulation primary adjustment and experimental error analysis was proposed to improve the efficiency and precision of target positioning in a high power laser device. A 3-CCD sensor was used to positioning and the "OpenGL" graphics software was used to capture CCD simulation images and to construct a cylindrical cavity target and a target-sending mechanism virtually. Then, the positioning precision of the experimental system was discussed, including the image detection error, the calibration error of 3-CCD sensor and the movement errors of the target-sending mechanism. The accuracy of the positioning method was confirmed in the simulation system independently by adjusting the target to a desired position without errors. In the experiment, the precision of the target positioning is less than ±5 μm and the orientation error is ±0.015°. It indicates that the simulation primary adjustment can be implemented from the experimental platform, so the working efficiency is improved. The experimental result shows that the proposed method satisfies the precision requirements of the target positioning in high power laser devices.Keywords：high power laser device;CCD measurement;target positioning;OpenGL;error analysis- 64
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Published：2020-08-13 -
Orbit determination for space target based on opto-electrical imaging, tracking and ranging on satellite
Abstract：A kind of orbit determination technology for a space target based on satellite borne electro-optical imaging, tracking and ranging was proposed to obtain the orbit movement information of the space target. On the basis of surveying, the relative movement information between satellite and target was obtained by the satellite borne optical measuring system, the angle flowing information of satellite attitude angles and rotation angles of tracking frame was captured by corresponding angle sensors, and the absolute motion information of the space target in an earth coordinate system was computed completely through a series of coordinate transformations. The state equation and measurement equation of the target in earth coordinate system were gained after describing physical model, coordinate systems and basic principle in turn. Furthermore, a mathematic simulation was researched after analyzing many models including space-based surveillance satellite orbit, opto-electronic tracking and control, target characteristics and optical imaging and ranging, and the computation results were discussed.The experiments show that the precision of orbit determination is better than 0.5 km for ideal models.Keywords：space-based surveillance;orbit determination for target;opto-electrical tracking;opto-electrical imaging;laser ranging;modeling and simulation- 104
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Published：2020-08-13 -
Robot vision system for 3D reconstruction in low texture environment
Abstract：To realize the obstacle avoidance and automatic navigation of a robot in a low texture environment, an active stereo visual system consisting a binocular camera and a compact laser projector was established. The dense stereo matching algorithm was investigated. Firstly, the compact laser projector generated the spot patterns with excellent uniqueness and anti-noise performance for increasing the texture information. Then, an adaptive-window matching algorithm was proposed based on Integral Grayscale Variance(IGSV)and Integral Gradient Variance(IGV). The algorithm was used calculate the integral variance in a matching window using the integral image obtained by the left image. If it was greater than the variance threshold, the correlation between the left and right image pixels was calculated to get the dense disparity maps. Experimental results show that the vision system accurately gets the 3D dense scene around the robot and the 3D reconstruction accuracy is 0.16 mm, which is suitable for the obstacle avoidance and automatic navigation. As compared with the traditional methods, the computation cost of dense matching has at least decreased by 93% since the computation used for image variance could not increase with the size of the matching window.Keywords：robot vision;three-dimensional reconstruction;integral image;grayscale variance;gradient variance;adaptive-window;stereo matching- 28
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Published：2020-08-13 -
Texture-guided sparse tensor representation and its application in lung CT images
Abstract：On the basis of tensor-based theory applied to the high-dimensional image processing, a tensor-based sparse representation algorithm was proposed to preprocess lung CT images and to enhance the useful information for the images. Firstly, a Tensor-based Orthogonal Matching Pursuit (TOMP) was designed for sparse representation and a Higher-order K-Singular Value Decomposition (K-HOSVD) was constructed for updating the dictionary. Then, the main parameters of the tensor multiplication was optimized. It means that the 3D gray-level co-occurrence matrix was constructed and the relationship between tensor multiplication model and texture features was established. Finally, the proposed method was used in 150 sets of lung CT images from LIDC database and the sparse representation performance of the proposed scheme was evaluated. The results from proposed algorithm show that the Peak Signal to Noise Ratio (PSNR) is increased by 1.5% and the Mean Square Error (MSE) is decreased by 1.2% as compared with that of other common schemes. Furthermore, the edge bias error is decreased by 3.0% and the volume overlap is increased by 1.2% as compared with that of preprocessing segmentation result. The conclusion indicates that the proposed algorithm is more suitable for the sparse representation of three-dimensional images.Keywords：computer-aided diagnosis;CT Image;sparse representation;tensor theory;gray-level co-occurrence matrix- 73
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Published：2020-08-13 -
Registration between multiple sequences for scene reconstruction
Abstract：As traditional single sequence scene reconstruction method is easy to loss scene information and has a lower data utilization, this paper proposes an approach to the registration between multiple sequences for scene reconstruction. The method uses a similarity transformational as the registration model and proposes the separating initial registration method to deal with the scale, rotation and translation respectively. Then, it fits the observed plane to suppress the noise data and select the co-visible points. Finally, the registration between multiple sequences with different scales, positions is performed and the registration results are applied in successive subsequent reconstruction. The experiment shows that the initial error has been reduced from 17.69% to 46.86%, and the terminated error reduced from 27.5% to 71.96% after suppression of noise data along the oriented orientation. Moreover, the 10 596 vertices are reconstructed from 47 frame images, more better than 3 893 vertices reconstructed by traditional single sequential method. The proposed method full makes use of the observation images and allows the ultimate fitting surface of the scene to have more scene details.Keywords：three-dimensional reconstruction;point cloud;transformational model of registration;initial registration;noise suppression;co-visible point- 54
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Published：2020-08-13 -
Artificial target recognition and location based on Mars exploration
Abstract：To recognize and locate artificial targets of a rover and a lander in Mars exploration, a two-step artificial target location method is proposed by combination of the characters of artificial targets of the curiosity rover with Mars environments. The first step is to recognize the artificial targets in the image and to locate them preliminary. The edge information is obtained by edge detection, and contour feature-points are extracted by edge tracing. As the artificial targets in the Mars surface environment always are adhered and deposited by dust particles and are suffer from the uneven illumination and shadow block,the paper proposes an adaptive edge detection algorithm based on Mars environment. The algorithm uses least square ellipse fitting method to fit and recognize the artificial targets in the image and locate the center of each artificial target preliminary. The secont step is to locate every artificial targets accurately. According to the preliminary result of ellipse fitting, the image is cut into pieces with one ellipse in each piece. Since the center of the artificial target is the intersection point of two intersecting lines, the Hough transform is used to detect the lines. The coordinate of intersection point is relocated and to obtain the center of the artificial target precisely. Experiments are carried out based on artificial target images of curiosity rover. The experimental results indicate that the method proposed can be used in the targets with largely deformation, and the location accuracy is within 1 pixel. The method is robust to the dust adhesion, illumination and shadow effects, and satisfies the Mars exploration system requirements for the resolution and robustness.Keywords：mars exploration;target recognition;artificial target;target location;illumination robust- 72
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Published：2020-08-13 -
Performance on sparse representation of star images
Abstract：The sparsity of a star image was explored in different representation approaches to apply better sparse representation to the compressive imaging process of a star tracker. The sparsity of star image was analyzed in two ways. In the first way, the Discrete Cosine Transform (DCT), Discrete Fourier Transform (DFT) and the Discrete Wavelet Transform (DWT) were used to construct complete representation bases and to examine the sparsity of star image in different complete representation bases. In the second way, the DCT complete basis was selected to create the overcomplete dictionary and learning dictionary to analyze the sparsity of the star image in different representation approaches. The simulation result shows that the average Peak Signal to Noise Ratio(PSNR) of the star image is 15-20 dB higher than that of the common scene image by complete based representation, while the overcomplete dictionary and learning dictionary based representations improve the PSNR by 2-20 dB with different sparsities. Regarding the quality of star point reconstruction, the rate of successful reconstruction is mostly higher than 95% when the sparsity is more than 10% in different representation approaches. The results verify that the star image has the preferable sparsity and meets the requirement of compressive imaging.The reconstruction of the star image maintains the position of star centroid position suitable for attitude determination to a large extent,which verifies the sparse precondition and feasibility for applying the compressive sensing in star trackers.Keywords：star image;sparse representation;compressive sensing;star tracker- 62
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Published：2020-08-13 -
Articulation training for children with hearing disorder based on visualization model of tongue
Abstract：An articulation training method for children with hearing disorder was proposed based on a visualization tongue model. By training on the position of articulation for children who have residual hearing and hearing compensation, these children could acquire the accurate place and way of articulation. A tongue three dimensional model was established based on the tongue rehabilitation training with the combination of three-dimensional modeling technology and sensor technology. The three-dimensional positions of tongue during the process of articulation was acquired by a palate sensor. Then, 23 initial consonants were selected as samples for establishing a sample database of tongue positions of children with normal hearing during articulation. Such the tongue model could be activated to provide a guidance for children with hearing disorder during training on the position of articulation. This method displays the movement of tongues of children with normal hearing during articulation and overcomes the shortcomings that has been neglected in tongue training and language training. Experimental result indicates that this method improves the effect of articulation training for children with hearing disorder and shortens training time. Especially for those articulation processes involving complicated coordination between tongue, lower jaw and unobvious position of articulation, the method increases the accuracy of articulation training by 15%.Keywords：children with hearing disorder;three-dimensional modeling;tongue visualization model;articulation position;rehabilitation training- 49
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Published：2020-08-13 -
Fast recognition and precise orientation of space objects in star background
Abstract：To improve the real-time performance and positioning accuracy of space object surveillance using an optoelectronic telescope, a fast recognition and precise orientation system for space objects was established. The algorithms for the motion characteristics, fast recognition, star centroid computing, and the astronomical orientation of space objects were investigated. The system constitution and working principle of the opto-electric observing system for space objects were introduced, the motion characteristics of space objects in a visible field of the CCD chip were analyzed and a fast recognition algorithm was presented firstly. Then the fast recognition for space objects was implemented by using the frame subtraction and the mathematical morphology. Finally, the astronomical orientation method was investigated and the precise orientation of space objects was realized in the usage of Tycho-2 catalogue. Experimental results indicate that the average processing time of fast recognition and real-time astronomical orientation for space objects is respectively 10 ms and 25 ms, and the precision of real-time astronomical orientation is less than 4". It concludes that the results obtained satisfy the requirements of space object surveillance for high real-time, high precision, good stability and reliability.Keywords：space objects;object identification;astronomical orientation;Charge Coupled Device (CCD)- 73
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Published：2020-08-13 -
Blind moving image restoration based on sparse representation and Weber's law
Abstract：For the motion blur problem of a visual image produced in moving processing, a blind image restoration method based on sparse representation and Weber's law is proposed. The method uses a shock filter to predict the sharp edges of blurred images, and a multi-scale strategy to estimate the blur kernel from a coarse estimation to a fine one. The sparse representation is treated as a priori knowledge for regularization constraint of blind image restoration model, and the Weber's law which reflects the human visual characteristics is combined to conduct blind restoration for the synthetic blurred image and the real blurred image. Experimental results show that the proposed method achieves better restoration results both for the performance indexes and the image textures. As compared with the Rob Fergus's method and Xu Li's method developed in recent years, it shows that the structural similarity (SSIM) is 0.762 4 and the Peak Signal to Noise Ratio (PSNR) is improved by 1.82 dB to 2.99 dB for the deblurred Lena image, and the SSIM is 0.858 9; and the PSNR has improved by 2.46 dB to 5.58 dB for the deblurred Cameraman image. Moreover, the proposed method reduces the boundary artifacts of the restored image, which is better consistent with human visual perception characteristics.Keywords：blind image restoration;moving image;sparse representation;Weber's law;shock filter;regularization constraint- 47
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Published：2020-08-13
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