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Issue 5 ， 2016
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High accuracy three-dimensional attitude angle measuring device
Abstract：A high accuracy measuring device and corresponding measuring method for three-dimensional attitude angles (yaw, pitch and roll) were designed based on an autocollimator and a coordinate rotary transfer matrix. The working principle and structural composition were introduced. A three-dimensional attitude angle measuring model was established and the theory algorithm by coordinate rotation matrix was derived based on the principle of autocollimation angle measurement. Then, the optical system was designed according to the demand of the measurement system. A single Field Programming Gate Array(FPGA) was used to implement double CMOS image sensor imaging, spot identifying, subdivision positioning, three-dimensional attitude angle calculation and rapid communication with a USB. To ensure the unity of the actual equipment parameter and design data, a high precision calibration method was researched for the three-dimensional attitude angle measuring device. Finally, three-dimensional attitude angles were tested to verify this measuring device, and the degrees and the factors affecting the angle measuring accuracy were analyzed as well. Calibration and experiment measurement results indicate that the measuring precisions of the yaw, pitch and roll angles for the measuring device are 2.2", 2.5" and 7.8" respectively in view field of ±20'. It shows that the three-dimensional attitude angle measuring device has higher precision, simpler structure as well as stronger stabilization, and can be widely applied to engineering practices.Keywords：three-dimensional attitude angle measurement;angle measuring device;two-axis autocollimator;roll angle;pitch angle;yaw angle;calibration- 54
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Published：2020-08-13 -
Effects of ageing treatment on light transmission and sensitivity of plastic optical fiber sensors
Abstract：To improve the sensitivity of a plastic optical fiber (POF) evanescent wave sensor with the normal core-cladding structure, the sensitive region of the sensor was aged in vacuum and distilled water. In the ageing treatment, the partial coating of the POF was removed firstly, the uncoated region with the normal core-cladding structure was employed as the sensing region of the sensor, then the sensing region of the sensor was aged in vacuum and distilled water, respectively. The light transmission and sensitivity of the sensor after ageing different time in vacuum and distilled water were compared, and the effects of ageing treatment on the light transmission and sensitivity of the sensor were analyzed. The research indicates that after ageing treatment, the core refractive index of the POF and the material composition are changed, which allows the light transmission mode in the optic fiber, the penetration depth and transmission length of the effective evanescent wave at the surface of sensing region to be changed, so that the light transmission property is dropped. The experimental results also show that the sensitivity of the aged sensor in the glucose solutions firstly is increased, subsequently decreased with the increase of the ageing time, and the maximum sensitivity in the vacuum has reached -0.0042/g·(100 mL)-1 at temperature of 105℃ and ageing time for 20 min, higher than that of sensors with the ageing treatment in the distilled water. The research provides technological supports for developments of POF evanescent wave sensors with higher sensitivity and normal core-cladding structures.Keywords：optical fiber sensor;evanescent wave sensor;plastic optical fiber;normal cladding-core structure;aging treatment;sensitivity;light transmission- 88
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- 1
Published：2020-08-13 -
Evaluation of mirror seeing based on PSSn
Abstract：As the design and assembly of optical systems in an optical telescope with large aperture mirrors are related to the mirror seeing, this paper introduces the normalized point source sensitivity (PSSn) to improve the limitation of traditional evaluation method and to realize the evaluation of mirror seeing in all frequencies. The concepts of the mirror seeing and its detection and evaluation methods were introduced and the shortcomings of the traditional evaluation methods and evaluation factors were pointed out. The evaluation index PSSn proposed by the 30 m large aperture telescope research group was introduced the new evaluation method. The PSSn properties were analyzed, and the expressions of the PSSn in different exposure conditions and seeing conditions were obtained based on the multiplication property and exposure conditions of the PSSn. The calculation procedure was given by considering the shutter time, mirror figure and atmosphere turbulence. Finally, with the help of random selection of sub-aperture on a large aperture wavefront, the ‘frozen turbulence’ was used to generate the simulated seeing condition over the mirror surface. The evaluation procedure was verified by this simulation. Based on the evaluation and analysis method presented in this paper, the system engineers could evaluate the mirror seeing for the large aperture optical system more objectively, and could build the error budget tree more reasonably to decrease the cost of the optical system.Keywords：large aperture telescope;mirror seeing;Normalized Point Source Sensitivity (PSSn);seeing evaluation;frozen turbulence;power spectral density- 50
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Published：2020-08-13 -
Comparison between pencil-beam and cone-beam in XLCT system
Abstract：The excitation characteristics of X-ray Luminescence Computed Tomography (XLCT) was researched. Two kinds of imaging systems for pencil-beam XLCT and cone-beam XLCT were introduced and their respective performance indexes such as the excitation schemes, scanning costs, reconstruction efficiency, spatial resolving capacity and reconstruction costs were compared and analyzed in detail. The comparison experiment shows that the scanning time of pencil-beam XLCT is 436 s but that of the cone-beam XLCT is only 10 s. In the experiment for a single target, the reconstruction time and location error of pencil-beam XLCT are 82.57 s and 0.47 mm, and those of the cone-beam XLCT are 172.63 s and 1.59 mm, respectively. In the two group experiments for double targets with edge distances of 1 mm and 0.5 mm respectively, the pencil-beam XLCT can accurately distinguish all targets with a reconstruction error less than 0.8 mm; however, the reconstruction error of the cone-beam XLCT reaches to 1.7 mm for the double targets with the edge distance of 1 mm and can not distinguish the targets at the edge distance to be reduced to 0.5 mm. Experimental results demonstrate that compared with the cone-beam XLCT, the pencil-beam XLCT has better performance in reconstruction time, location accuracy and spatial resolving due to its "excitation priors", but has obviously poor capability on the system scanning. This paper provides a valuable reference for researchers on the selection of appropriate XLCT systems.Keywords：optical molecular imaging;X-ray Luminescence Computed Tomography (XLCT);pencil-beam XLCT;cone-beam XLCT- 71
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- 4
Published：2020-08-13 -
Measurement of continuous deformation of thin-walled spheres compressed by a rigid plate
Abstract：An optical measurement experimental system was proposed to research the continuous deformation and crushing behavior of thin-walled spheres compressed by a rigid plate. In experiments, ping pong balls were selected as thin-walled spheres because of its ideal material properties and very thin but uniform wall thickness and the quartz glass plate was regarded as a rigid body to compress ping pong balls. Then, the speckle pattern was captured by cameras clearly. Furthermore, the three dimensional digital image correlation (3D-DIC) method with advantages of non-contact, full-field measurement, and high-accuracy was employed to measure the continuous compression deformation of the contact surface of the ping pong balls directly. The two dimensional digital image correlation method combined with a pressure sensor was used to obtain force-displacement curves simultaneously. Experimental results demonstrate that the 3D-DIC method is able to implement the visualization of mechanical behaviors of thin-walled spheres compressed by the rigid plate, including the local flattening, axisymmetric inward dimpling and the unsymmetric polygon formation. Experimental result indicates that the measurement precision of ping pong balls is up to 0.5%, and the numerical results obtained by using Abaqus is in agreement well with experimental results. The experimental and numerical results both demonstrate the validity of the proposed method.Keywords：digital image correlation;continuous deformation measurement;3D deformation measurement;thin-walled sphere;buckling- 48
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Published：2020-08-13 -
Parameter optimization and direction recognition in angle measurement by laser self-mixing interference
Abstract：The nonlinear relationship between phase and rotation angle of a self-mixing interference signal caused by a reflector rotation was researched and an experimental parameter optimization method was proposed to reduce the nonlinear angle measurement errors from the nonlinear effect above mentioned. The physical approximate conditions in self-mixing type interferometry were re-evaluated for enlarged angle measurement range, the effect of experimental parameters on the errors of angle measurement was analyzed theoretically and simulations were carried out subsequently. A new method relied on the nonlinear relationship to recognize the direction of rotation was introduced. Finally, self-mixing interference experiments for angle measurement were performed and the results corresponding to different conditions were given. The results show that errors of focused laser self-mixing type interferometry are reduced remarkably, and the measurement precision reaches to 10-5 rad, which is increased by one order of magnitude as compared with that of the non-optimized scheme. These results verify the evidences of the optimization scheme for the recognition of rotating direction and the improvement of measurement accuracy. Moreover, as the high accuracy of measurement maintains angle measurement ranges enlarged, it broadens applications of laser self-mixing interferometry based on the reflector rotation.Keywords：laser self-mixing interferometry;angle measurement;nonlinear error;parameter optimization;rotating direction- 60
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- 15
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- 6
Published：2020-08-13 -
Design of optical film with microstructure for viewing angle deflection
Abstract：When a liquid crystal display is used in cockpits, its max luminance direction usually has a certain angle with the direction of viewers. Therefore, this paper designs an optical film with a microstructure surface to allow the max luminance to be changed with the direction of viewers. Based on the luminous distribution of common backlight, the microstructure surface of the optical film was designed as a right triangle. In consideration of the total reflection of the right-angle side, narrower half-luminance angle range and its cut-off angle, the height and the angle of the microstructure were optimized to improve the half-luminance angle ranges. To eliminate cut-off angle and to increase half-luminance angle ranges further, the microstructure was optimized once again, and the outline with two peaks for the microstructure was proposed. The simulation results show that when the horizontal viewing angle doesn't change, the vertical viewing angle is at about 20°,the transmittance is 87.3% and the half-luminance angle ranges are (-12.5°, 45°). On the basis of the design, a sample was produced and measured. The practical measurement results show that the angle of max luminance turns from 0° to 18.9°, the half-luminance viewing angle changes from (-24.1°, 23.5°) to (-9.2°, 45.3°), and the transmittance is 82.0% as compared with the common backlight without the optical film. These results satisfy the requirements of special viewing angles.Keywords：liquid crystal display;optical film;microstructure;backlight;viewing angle deflection- 32
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- 4
Published：2020-08-13 -
Spectral calibration of medical microscopic imaging spectrometer
Abstract：To accomplish the spectral calibration of a medical microscopic imaging spectrometer developed by ourselves for brain tumor operation, a spectral calibration system was designed. The system is composed of a monochromator, a tungsten-light source, a surgical microscope platform and a prism-grating-prism(PGP) imaging spectrometer. A software for spectral calibration was developed based on monochromator wavelength scanning method, the spectral data of the medical microscopic imaging spectrometer in full bands were obtained and the data processing and data analysis were performed. The spectral calibration was implemented by adjusting path, monochromator calibration and imager calibration. Experimental results show that the accuracy of the spectral calibration is better than 0.1 nm, the spectral ranges of the imaging spectrometer are greater than 400-900 nm and its spectral resolution is better than 3 nm. The test validation shows that the spectral calibration system is accurate, simple, compact, and easy to operate and meets the actual clinical requirements of microscopic imaging spectrometers.Keywords：medical imaging spectrometer;microscopic imaging spectrometer;spectral calibration;Monochromator- 57
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- 5
Published：2020-08-13 -
Multi-channel drop filter based on two-dimensional photonic crystal
Abstract：On the basis of the resonant coupling principle of light wave modes between the defect modes of line-defect waveguides and the ring resonators, a multi-channel drop filter consisting of a line-defect waveguide, ring resonators and 60° bend waveguides was designed by using the two-dimension triangular lattice photonic crystals. The energy structures of a complete photonic crystal and a line-defect waveguide were calculated by the plane-wave expansion method. The transmission characteristic of the filter was investigated with the two-dimensional finite difference time domain method. Then, the effect factors on coupling efficiency of devices were analyzed and an improved method was proposed. The analysis shows that the resonance frequencies of photonic crystal ring resonator depend on the radius of dielectric rods in the resonators and the coupling efficiencies between the line-defect waveguides and the ring resonators are improved by changing the shapes of dielectric rods in coupling region and replacing the straight waveguide with a 60°bend waveguide. The simulation results show that the optimized multi-channel two dimensional photonic crystal filter has good wavelength selection frequency performance, and the transmission efficiencies of all the resonance wavelengths are above 90%. The filter is characterized by a smaller size, simple structure, easy integration and good application prospects.Keywords：multi-channel drop filter;photonic crystal;line-defect waveguide;plane-wave expansion method;finite difference time domain method;device coupling- 48
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- 8
Published：2020-08-13 -
Single grate type time-grating displacement sensor based on photosensitive array direct modulation
Abstract：Because conventional Moiré fringe gratings are difficult to be manufactured and assembled, this paper proposes a single grate type time-grating displacement sensor based on a time subdivision space. Based on the particle characteristics of light, a generation method of light field electronic traveling wave by light field signal with orthogonal transform was analyzed. Then, by using dot matrix Light Emitting Diode(LED) modules as alternating light sources,the electronic traveling wave signals to response the displacement values were obtained by coupling the space orthogonal photosensitive array with the receiving device. Finally, the space linear displacement was measured by detecting the time difference of zero-crossing between electronic traveling wave signal and excitation signal. A principle prototype was developed and validated experimentally by using a common mechanical processing method. The testing results demonstrate that measuring errors of the developed prototype are controlled within ±2 μm after error correction in a measuring range of 440 mm. The single grate type time-grating displacement sensor relaxes the requirements for installation process and improves its anti-interference ability. Moreover, the measurement technique avoids the weaknesses of traditional coarse grating technologies such as difficult to improve measuring accuracy and poor dynamic characteristics and provides a new method not to be depend on mechanical subdivision for improving the precision of optical displacement measurement.Keywords：displacement sensor;single grate sensor;time-grating sensor;displacement measurement;photosensitive array;direct modulation- 73
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- 2
Published：2020-08-13 -
Radiation calibration of EUV space cameras
Abstract：There are no proper radiation calibration methods and devices for EUV space cameras, so this paper proposes a small target imaging radiation calibration method suitable for the EUV band and establishes a radiation calibration device based on the method in a lab. This method uses a standard transfer detector to calibrate the radiance of the small target. Then, a EUV space camera is used to take the small target's image in its center Field of View(FOV) and to get its radiance responsivity. Finally, by adjusting the motion platform, the small target's images in different FOVs are taken by the EUV camera, and the radiance responsivity in different FOVs are obtained. The developed radiation calibration device consists of a light source system, standard transfer detectors, a vacuum tank and a four-dimensional motion platform fixed in the camera. The light source system consists of a hollow cathode light source, an extreme ultraviolet grazing incidence monochromator, and a collimating mirror generating a parallel monochromatic beam. The standard transfer detectors are used to calibrate the beam's photon flux and small target's radiance and the motion platform enables the camera to take the small target's images in different FOVs and to get camera's responsivity in different FOVs. A EUV camera has been calibrated by this device, and the error sources are analyzed. The calibration results indicate that its accuracy is better than 15% and implements the radiation calibration for whole bands.Keywords：space camera;radiation calibration;small target imaging;standard transfer detector;extreme ultraviolet band- 99
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- 5
Published：2020-08-13 -
Control and experiment of micro-dispenser by piezoelectric drive
Abstract：For the requirement of micro components in bonding for non-contact micro-dispensing volumes, a piezoelectric micro-dispenser was designed and fabricated. The dispensing of micro-droplets was implemented by the instantaneous deformation from the extrusion between the capillary tube and the piezoelectric ceramic tube. The fluid behavior and droplet forming conditions in the capillary were analyzed, and a coupling model including a piezoelectric ceramic, a capillary and a fluid was established by using multidiscipline coupled-field analysis method. The influences of the driving voltage, nozzle diameter and the fluid viscosity on droplet formation were analyzed. An experiment to control the droplet formation was performed in an experimental platform. The compound actions of multiple parameters (nozzle diameter, fluid viscosity, voltage magnitude and pulse width) were discussed based on experiments. The non-contact micro-dispensing of the micro droplets with a size of pL level was achieved by matching the corresponding parameters. Experimental results indicate that the minimum droplet volume of 8.31 pL is obtained when the parameters are set by the fluid viscosity of 30 mPa·s, the nozzle diameter of 10 μm, the voltage magnitude of 50V and the pulse width of 37 μs. These results verify the feasibility of the proposed method and the fabricated micro-dispenser.Keywords：micro-dispenser;multi-physical field;piezoelectric drive;droplet control;droplet non-contact distribution- 57
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Published：2020-08-13 -
Improvement of bias stability of micromechanical silicon resonant accelerometer at room temperature
Abstract：In consideration of the effect of ambient temperature on the precise measurement of a micromechanical silicon resonant accelerometer (MSRA), the frequency drift of the resonant beam and suppression methods were analyzed to improve its zero-bias stability in the ambient temperature. The stress caused by structural thermal expansion was modeled and simulated and an improved structure with a lower thermal stress was designed and fabricated to reduce the frequency shift caused by non-matching of thermal expansion coefficients. The test experiments show that the temperature coefficient of resonant frequency of the single beam decreases from about 30 Hz/℃ to-1.5 Hz/℃, which is close to the simulated value of-1.14 Hz/℃. To further improve the bias stability of the MSRA, a precise temperature measurement circuit was designed to compensate the temperature shift, and the circuit shows its temperature sensitivity to be 96.25 mV/℃ and the noise to be 0.000 2℃. By proposed optimizing structure and linear temperature compensation method, the bias stability of the optimized MSRA is superior to 10 μg within 1 h at the room temperature, which is 80% higher than previous level of our laboratory (52 μg) and satisfies the requirements of high-precision acceleration measurement.Keywords：micromechanical silicon resonant accelerometer;resonant beam;structure optimization;temperature compensation;bias stability- 50
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Published：2020-08-13 -
Joint structure and processing parameters of ultrasonic precision bonding for point-of-care testing chips
Abstract：For the requirements of Point-Of-Care Testing(POCT) chips for bonding precision, bonding strength, productivity and biological compatibility, this paper designs a structured energy director and a weld limited joint structure based on ultrasonic bonding. The influence of ultrasonic bonding time and bonding pressure on microchannel's height maintenance was researched, and the optimum processing parameters of precision ultrasonic bonding were determined. After ultrasonic bonding, a high precision microscope, a tensile testing machine and the whole sheep blood were applied to test the microchannel height, bonding strength, microchannel leakproofness and the whole blood driving performance of ultrasonically bonded POCT chips respectively. Experimental results demonstrate that the structured energy director is rational, reliable and easy to integrate each functions. The weld limited joint structure can control the height of microchannel accurately during ultrasonic bonding, the bonding precision of the microchannel is 2 μm, and the time range of whole blood driving test is less than 20 s. Moreover, the optimum processing parameters are conductive the realization of the high bonding strength more than 2.5 MPa. It concludes that the joint structure and processing parameters have the advantages of high bonding precision, high bonding strength, biological compatibility and uniform welding for POCT chips, and are suitable for the application to medical POCT chips.Keywords：Point-Of-Care Testing(POCT) chip;ultrasonic bonding;joint structure;microchannel height;processing parameter- 39
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- 1
Published：2020-08-13 -
Structure design of nanometer positioning stage with a large stroke
Abstract：As the performance of a scanning interference field lithographic system using static three-step splicing exposure method is related to the positioning accuracy and stability, this paper designs a 2D positioning stage with a large stroke to achieve high positioning accuracy. The friction drive and piezoelectric ceramic micro displacement mechanism were combined to form a macro-micro feed mechanism. A closed gas hydrostatic guideway was used to drive the stage to implement the raster indexing and scanning movement along X, Y directions. The friction driving mechanism and aerostatic bearing structure were optimally designed in detail, and the natural frequency of overall structure of the stage was calculated by finite element analysis. An autocollimator was used to test the linearity of the guideways in X, Y directions,and results show that yaw and pitch accuracy in both directions are within ±0.04 μm. A laser interferometer was taken to detect the positioning accuracy and positioning noise of the guideway in X direction and the result shows that for the stage with a stroke of 220 mm in X direction and 300 mm in Y direction, the positioning accuracy of X direction is better than ±5 nm, and the positional stability is better than ±25 nm,meeting the requirements of scanning interference field exposure system stage for nanometer positioning precision.Keywords：scanning interference lithographic system;high-precision stage;gas hydrostatic guideway;Friction drive;nanometer positioning- 63
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- 5
Published：2020-08-13 -
Fabrication of micro diaphragm piezoelectric pump by using bulk PZT
Abstract：On the basis of the inverse piezoelectric effect of the PZT(Pb based Lanthanum doped Zirconate Titanate), a micro diaphragm piezoelectric pump was designed and fabricated. By converting the electrical energy into mechanical energy, the microfluidic control of liquid was realized. The micro pump was consisted of two parts, a micro actuator and a micro check valve. The micro actuator was mainly used to provide a driving force for the liquid, and the micro check valve was taken to control the flow direction of the liquid precisely. With the simulation analysis of the displacement and shape of the PZT-Si diaphragm, the design size of micro actuator was determined and the driving liquid performance of the actuator was estimated. By using eutectic bonding, grinding thinning, ICP-RIE(Inductively Coupled Plasma-Reactive Ion Etching), excimer laser processing and other micro fabrication processes, the micro actuator and the micro check valve were fabricated, respectively. A driven testing of the micro pump was carried out. The experimental results show that the resonance frequency is about 70 kHz, which can drive the displacement and movement of liquid with a micrometer volume. When the driving signal is 30 Vp-p at the frequency of 600 Hz, the drive flow rate of liquid is about 65 μL/min. The fabricated micro pump is characterized by a small volume and good linearity.Keywords：microfluidic analysis system;diaphragm piezoelectric micro pump;Pb based Lanthanum doped Zirconate Titanate (PZT);micro check valve;inverse piezoelectric effect;driving simulation;micro fabrication- 47
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- 2
Published：2020-08-13 -
Structural design and ANSYS thermal simulation for semiconductor laser system
Abstract：Conventional semiconductor laser technology always chooses a separate design with its controller system, so that the semiconductor laser volume can not be compressed any more. Meanwhile, the integrated structure of the semiconductor laser has serious radiation heat. To overcome the problems mentioned above, this paper proposes a new design method of the semiconductor laser for its integration and miniaturization. To guarantee the laser to be operated stably and to show good thermal management, the ANSYS software is used to perform a thermal simulation for the high-density components such as Print Circuit Board(PCB) to improve the structure reliability before the structure manufacturing. Simulation experiments indicate that designed novel structure allows the semiconductor laser to integrate with the drive controller., and has uniform temperature distribution and an appropriate space, and can guarantee the laser to operate stably. The whole sizes of the semiconductor is only 85 mm×95 mm×115 mm. Moreover, the appropriate space is left in the structure of the semiconductor, which is conductive to the design of a collimated light path for its future applications.Keywords：semiconductor laser;drive controller;ANSYS thermal simulation;miniaturization;Integration- 52
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Published：2020-08-13 -
Performance analysis and test of blowing-type PZT wind energy harvester
Abstract：A blowing-type PZT wind energy harvester consisting of a piezo-cantilever and a proof mass on its free-end was presented. By considering the static balance deformation of the piezoelectric vibrator, an analysis model of a flexible piezoelectric vibrator was established and simulated on the basis of the theory of vortex-induced vibration. Then, the influences of thickness ratios, wind speeds and proof masses on the electrical energy generation were obtained. The results show that there are individual optimal thickness ratios for the generated voltage, energy and the output power to achieve peaks, and the optimal thickness ratios for the generated voltage/energy/power are 0.5/0.65/0.65, respectively. Under other parameters given, there are optimal wind speeds and optimal proof masses for the voltage to achieve their peaks, and the optimal wind speed (proof mass) decreases with the increasing of proof mass (wind speed). A PZT wind energy harvester was fabricated and tested under different proof masses and wind speeds. The experiment results show that the achieved optimal proof masses and optimal voltages under wind speeds of 4.8/7.2/10 m/s are 15/11/7g and 1.9/3.94/6.18 V respectively. In the case of wind speed of 10 m/s, the generated voltages under 10 g proof mass is 4.1/1.2 times those under 0/20g proof mass respectively. It concludes that a reasonable proof mass is helpful for a PZT wind energy harvester to generate more energies.Keywords：piezoelectric wind energy harvester;blowing-type wind energy harvester;wind speed;electrical energy generation- 55
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Published：2020-08-13 -
Optimization design and error distribution for secondary mirror adjusting mechanism of large optical payload
Abstract：A Hexapod precision positioning platform called the Secondary Mirror Adjustment Mechanism(SMAM) was designed to precisely adjust the second mirror of a large optical payload. The structure configurations were optimized based on the multi-objective function, and the errors of each strut and the upper (lower) hinges were distributed by the optimization algorithm. A kinematic model and a static flexibility model for the Hexapod platform were established, and the influences of main structure parameters on the mechanism performance were analyzed. Then, the positioning accuracy and anti-deformation indexes were put forward. By using the structural parameters as variables, the optimization functions were established, and two single-objective functions were optimized by the genetic algorithm. At the same time, a unified constraint function of weight factor was constructed, and the multi-objective function was also optimized by the genetic algorithm. Afterwards, a nonlinear optimized error distribution model was established, and it was used to distribute the errors for each strut and the upper (lower) hinges. Finally, by testing the performance indexes of a prototype, the efficiency of the proposed method was verified. The research results after optimization show that the positioning accuracy and the anti-deformation capacity are improved by 8.3% and 62.5%, respectively. The upper and lower hinge error bounds increase from 2.7 μm to 6.3 μm, and each strut error bound increases from 1.3 μm to 3.2 μm. Moreover, the relative positing accuracy and the static stiffness of Z axis are 0.6% and 41.14 N/μm, respectively. The research in this paper improves the positioning accuracy and anti-deformation ability, and saves the design cycles and processing costs.Keywords：space camera;optical payload;secondary mirror adjusting mechanism;positioning accuracy;anti-deformation;multi-objective optimization;error distribution- 63
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Published：2020-08-13 -
Driving and controlling of high accuracy scanning servo-system in space
Abstract：A high accurate servo control technology was explored for the scanning servo-system of a spacecraft. When payloads such as space communication, observation and reconnaissance scan the targets on the ground, the servo system of payloads usually is required to provide high accuracy and low speed performance. So, this paper proposes a control scheme by using a Permanent Magnet Synchronous Motor (PMSM) as the servo driving system. It avoids the middle processing of a reducer and improves the control accuracy of servo system. A Field Programming Gate Array(FPGA) was used in the servo driving control system as the signal processing chip to improve the process speeds and control accuracy, and a higher precise absolute photoelectric encoder was taken to detect the rotation position to increase the detection accuracy of the speed and position. Furthermore, a power linear amplification was used in the main circuit to obtain smoother and smaller fluctuation wave forms. As the control scheme uses simulation sinusoidal signal driving and it avoids speed fluctuation come from switching and dead zones of the pulse width modulation(PWM) signals in low speeds, the experiments indicate that the control scheme realizes the speed control with high accuracy. The speed is smooth, and the speed fluctuation is within 1% when the operating is in an even speed. Moreover, the testing curves of the voltage and current are smoother without harmonic disturbance. The scan servo system meets the requirements of dynamic and static experiments, and provides a new solution for low speed and high precision scanning servo systems.Keywords：spacecraft;scanning servo-system;driving and control;PMSM;linear amplifying;low speed performance- 61
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Published：2020-08-13 -
Hysteresis characteristics of piezoelectric ceramic actuators
Abstract：As the inherent hysteresis phenomena of a piezoelectric ceramic actuator affects its positioning accuracy badly, this paper analyzes and verifies the characteristics of the hysteresis phenomena. The causes of hysteresis were analyzed through microscopic polarization mechanism and electromechanical coupling effects.Some experiments were designed to compare the hysteresis characteristics under different travels,different positions of the whole travel and different initial voltages.The experimental results indicate that:for the driving travel of 10 V, the output of average displacement increases at first then decreases and the average hysteresis error decreases from 0.419 3 μm to 0.158 9 μm as the increases of voltage intervals; for the driving travel of 100 V, the output of average displacement decreases from 42.882 5 μm to 25.92 μm and the average hysteresis error decreases from 3.999 3 μm to 1.692 3 μm as the increases of initial voltages. Moreover, when the initial voltage increases by 15 V,the output of displacement decreases by 5.654 2 μm on average,and the hysteresis error decreases by 0.769 μm on average.These results reflect the influence of domain switching status in the initial phase on electromechanical coupling efficiency in the driving process and also verify the domain switching theory effectively. The experiments suggest that the compensation for hysteresis errors of the piezoelectric ceramic actuator according to the hysteresis characteristics of domain switching in different steps can correct or reduce the effects by hysteresis errors, and can provide scientific reference for improving the control accuracy of positing systems.Keywords：piezoelectric ceramic actuator;hysteresis;domain switching;hysteresis characteristic curve;positioning and control- 91
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Published：2020-08-13 -
Frequency response of imaging quality by micro-vibration for large-aperture space-borne telescope
Abstract：The imaging quality of a large-aperture space-borne telescope is very sensitive to the micro-vibration induced by space environmental variation and the vibration inner of a satellite. Therefore, this paper researches the calculation method of frequency response of imaging quality effected by the micro-vibration to improve the dynamic imaging quality of the satellite in orbit. By using a real optical model to replace the linear optical model, it establishes an optical-mechanical integrated model to calculate the frequency response of the micro-vibration. Firstly, it builds Finite Element Model(FEM) for a space-borne telescope to calculate the structural frequency response and to obtain the displacement and phase of the optical surface nodes for each sampling frequency point. Then, the Monte-Carlo statistical method is used to establish the the optical-mechanical integrated model, and the root-mean-square (RMS) of system dynamic Modulation Transfer Function(MTF) and the Line of Sight(LOS) drift are analyzed to measure dynamic imaging performance of the large-aperture space-borne telescope. Finally, a structural prototype of large-aperture space-borne telescope is developed to verify the reliability of the FEM. The results show that the measured frequency is close to that of the FEM analysis and the error is under 5%, which meets the requirements of large-aperture space-borne telescopes for analysis of the dynamic imaging quality.Keywords：large-aperture camera;space-borne telescope;image quality;micro-vibration;line-of-sight jitter;integrated analysis- 64
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Published：2020-08-13 -
Modeling of dynamic nonlinear multi-field coupling for precision magnetostrictive actuator
Abstract：To improve the precision of a Giant Magnetostrictive Actuator (GMA) used in a precision machining field and to describe its complex hysteresis behavior under dynamic and quasi-static conditions, a GMA with an accurate displacement output was designed. By consideration of both the eddy current losses and hysteresis, a dynamic nonlinear model with multi-field coupling effects was also established. Relationships among energy loss, hysteresis and frequency and other working performance were studied. Firstly, the GMA was designed through the modular method. Then, based on the thermodynamic theory and energy conservation law, a nonlinear multi-field coupling constitutive model for giant magnetostrictive materials was established. Finally, a nonlinear multi-field coupling dynamic model for the GMA was proposed through analyzing the coupling process between the nonlinear constitutive behaviors of materials and the dynamic behavior of system structure. The effects of energy loss and pretightening force on the system characteristics were analyzed. The experiment results show that pretightening force improves the output characteristic of GMA and there is an optimal preloaded state. The model predicts the displacement accurately and the average relative error is about 4.5%. The hysteresis behavior is attributed to the energy losses generated in the irreversible motion process of domain. With the increase of frequency, the abnormal and eddy current energy losses and hysteresis increase. The eddy current effect can not be ignored when precision GMA is under a high frequency. The model describes the complex hysteresis behaviors of the GMA under dynamic and quasi-static conditions accurately. As the material's constitutive coupling and structure's dynamic behavior coupling are considered, the precision of the GMA is improved greatly.Keywords：Giant Magnetostrictive Actuator (GMA);nonlinear multi field coupling model;hysteresis behavior;eddy curren loss- 37
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Published：2020-08-13 -
Electrical properties of electrospinning under sheath gas focusing
Abstract：How to increase the ejection efficiency of an electrospinning jet by inducing sheath gas focusing was investigated, and an electrospinning experimental setup with sheath gas focusing was built up. The ejection and movement behaviors of electrospinning jet under the sheath gas was analyzed. The effect of some of technological parameters such as the pressure of sheath gas on a electrospinning current was studied based on the theoretical model. The experiments indicate that the sheath gas promotes the stretching and thinning of the electrospinning jet, by which the critical voltage of electrospinning and the diameter and distribution area of a nanofiber have been decreased. As the pressure of sheath gas is increased from 0 kPa to 50 kPa, the critical voltage of electrospinning decreases from 10.2 kV to 2.9 kV. When the applied voltage is 4 kV, the front-end of electrospinning jet takes 4.4 s to reach a collector and produces a peak current of 532 nA. The electrospinning current ranges from 300 nA to 500 nA during the stable ejection process. Moreover, both the diameter and surface charge density of electrospinning jet have been decreased by the sheath gas focusing, and the electrospinning current is only one seventh of that without sheath gas. Under the sheath gas focusing, the electrospinning current decreases with the increasing of gas pressure and the distance between nozzle and collector, but increases with the increasing of applied voltage and the concentration of polymer solution. It concludes that the sheath gas focusing restrains the charge interferences in electrospinning processing, decreases the diameter of electrospinning, improves both the injection stability of electrospinning and uniformity of nanofiber. This work provides a good way to improve the control level of electrospinning technology.Keywords：electrospinning current;micro current measurement;sheath gas;focused restriction;controlled ejection- 51
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Published：2020-08-13 -
Sub-step identification of LuGre friction parameters of inertially stabilized platform for airborne remote sensing
Abstract：A preliminary and accurate LuGre friction parameter identification method was put forward to improve the control precision of an inertially stabilized platform for airborne remote sensing due to its limited gimbal angular motion. From the digital control system, the parameter identification system of a friction model was constructed to transform the identification problem into that of a curve fitting. By limiting the amplitude and frequency of a input signal, the difficulties of parameter identification of friction model caused by the limited gimbal angular motion were solved. On the basis of the digital control system, the linear friction parameter was preferentially identified. Then, according to the stationary and dynamic characteristics of LuGre model, a sub-step bi-directional approach and a sub-step searching method were proposed to identify the remaining friction parameters in turn, and the preliminary identification was completed. Furthermore, the accurate identification was achieved by making full use of preliminary identification results and genetic algorithm. Simulation results indicate that parameter errors of preliminary identification are less than 5% while that of accurate identification are down to 0.7%. After adding a friction compensator designed by identified friction parameters, the ability to suppress the interference caused by low frequency angular motion of a base is improved by 4 times. An experiment for the identification and compensation of friction parameters based on a principle prototype, and the results show that the control precision of system is double that of the traditional one, which verified that the validity of identification method proposed and its engineering meanings.Keywords：airborne remote sensing;inertially stabilized platform;LuGre model;sub-step identification;genetic algorithm;feedforward friction compensation- 91
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Published：2020-08-13 -
Image deblurring for laser active illumination based on light vein features
Abstract：The images captured by a laser active illumination system are easily blurred by optical system defocus, atmospheric disturbance and platform vibration, and traditional deblurring methods can not achieve good image restoration. Therefore, this paper proposes a blind deconvolution restoration method based on light vein features to implement the image deblurring. Firstly, the blurred images were down-sampled, a scale pyramid was established, and the light vein patches were searched along a scale space. Then, according to the laser illumination imaging characterized by more saturated pixels, a new nonlinear image degradation model was proposed. Finally, to implement the three steps, blurred kernel estimation, light vein patch renewal and the image restoration, the proper energy function was proposed and the latent image without noise was iterated and recovered. A laser active illumination system was established and the experiments were performed on the images captured by the system and compared with state-of-art deblurred methods, The experiment results indicate that the proposed method not only obtains more clear images, but also availably suppresses ringing artifacts, and its Peak Signal to Noise Ratio (PSNR) is superior to that of other algorithms.Keywords：laser active illumination;image deblurring;light vein feature;Energy function;ringing artifact- 78
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Published：2020-08-13 -
Iteratively reweighted least squares method for camera pose estimation based on coplanar line correspondences
Abstract：To estimate the camera poses for calibrated or uncalibrated cameras, a novel pose estimation algorithm was proposed based on coplanar line correspondences and iteratively reweighted least squares. Firstly, a linear equation for the focus length and pose of the camera was established. The pose parameter was solved by more than four coplanar line correspondences. Then, the iteratively reweighted least square method was applied to optimizing the parameter, and the higher accurate estimated parameter and line weight were obtained. Finally, the focus length and pose parameters of the camera were obtained by calculation of line weight and the invariant distance of Euclidean transformation. Experimental results with simulative data indicate that the precision of angle is better than 0.2°, the precision of relative position is better than 0.5%, and consuming time is about 1 ms, when the focus length is known, and number of lines and noise level are 20 and 5, respectively. Moreover, the experimental results with real data indicate that the precision of proposed algorithm is close to chessboard calibration. As compared with the existing algorithm, the proposed algorithm is more accurate, robust, and is capable of estimating the pose of uncalibrated cameras based on a single image.Keywords：space camera;internal parameter calibration;pose estimation;line correspondences;iteratively reweighted least squares- 69
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Published：2020-08-13 -
No-reference color image quality assessment based on local features
Abstract：For the poor consistency of traditional no-reference color image quality assessment methods and human visual perceptive results, a new no reference color image quality assessment method was proposed based on the colorfulness, sharpness and contrast of images. A new sharpness measuring model for a color image was proposed based on the local feature of sharpness. Then, a novel contrast measuring model for the color image was established based on the local feature of contrast and the feature of Buchsbaum curve. Finally, a novel no-reference color image quality assessment function was constructed based on the linear combination of the colorfulness measuring model, sharpness measuring model and the contrast measuring model. The performance of the sharpness measuring model, contrast measuring model and the no-reference color image quality assessment function was verified by three kinds of degraded images(Gaussian blurred image, contrast changed image and noise image). The experiment results indicate that comparing the traditional methods, the performance of the proposed sharpness measuring model and the contrast measuring model is better than that of the traditional ones. The Spearman Rank Order Correlation Coefficient(SROCC), Kendall Rank-Order Correlation Coefficient(KROCC), and the Pearson Linear Correlation Coefficient(PLCC) of the proposed color image quality assessment function are 0.904, 0.865 and 0.922, respectively, which has better consistency as compared with those of the traditional methods.Keywords：no-reference image quality assessment;color image;sharpness measurement;contrast measurement;colorfulness measurement;quality assessment function- 53
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Published：2020-08-13 -
Test case generation of aerospace software based on modeling requirements
Abstract：A model-driven software test case generation approach was researched to improve the efficiency and coverage rate of aerospace soft test and to increase the validity of test. According to the characteristics of aerospace software test, the strategy of step-layer test case optimization was put forward instead of case-layer optimization. Firstly, a model for testing requirements was presented based on meta-modeling method. Then, the test requirements were split by model building to obtain the relationship between the test requirements and the dependence of the test requirements on the test steps. With the constructed path graph of test requirements, test cases were gotten based on traversing for the graph. Finally, the approach was applied to the test of aerospace software test. The results of application show that this approach reduces the risk of test case optimization and is effective to ensuring the adequacy and validity of testing activities. The number of test cases are reduced more than 40%, and the whole workload of test is saved more than 18%. It meets the coverage rate of software test and improves the efficiency of test.Keywords：software test;aerospace software;test case generation;optimization of test case;test requirement;model- 66
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Published：2020-08-13 -
Image mosaic algorithm based on area blocking and SIFT
Abstract：For a large amount of calculation and poor real-time performance of image matching algorithms, this paper proposes a novel image mosaic algorithm based on area blocking and Scale Invariable Feature Transformation (SIFT). This algorithm uses a normalized cross-correlation coefficient from the image energy to search the similar region between the reference image and the image to be matched, and then it takes the SIFT algorithm to extract image feature points in a overlapped region to implement the rapid and accurate image registration. Finally, it performs the image geometry adjustment and image fusion to get a seamless image. The experimental results show that the algorithm reduces the large number of useless search of the traditional SIFT algorithm, ovecomes the image geometric distortion, lowers algorithm complexity, and improves the speed of image matching. With ensuring the accuracy of image matching over 90%, its computation time has decreased by nearly 50% than that of the traditional SIFT algorithm. In conclusion, the algorithm implements accurately and rapidly seamless mosaicking for the images with deformation and scale transform.Keywords：Scale Invariable Feature Transformation (SIFT);area blocking;image matching;image mosaic;normalized cross correlation- 148
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Published：2020-08-13 -
Separating and clustering of structured light stripe color
Abstract：To overcome the misrecognition for the stripe color from a color structure light system caused by the interference of object surface color and the color crosstalk among the stripes, a method to separate and cluster the structured light stripe color was proposed. Firstly, a novel color correction method for a camera and a projector was designed to avoid the crosstalk phenomenon of color sequence from ambient light and the system and to solve the coupling issues of the system. Then,a reflective separation mechanism was presented to extract the diffuse component and the specular component of object surfaces and to correct the effect of object background color on color-coded stripes. Finally, the color clustering algorithm was used to classify the modulated stripe color and to correct the interference among stripes and recover the information of stripe color due to energy consumption of the system. The feasibility of the proposed method was verified. Experimental results show that this method has higher anti-jamming capability and stronger robustness. It recognizes correctly the interfered colored stripes, and the recognition rate reaches about 92%.Keywords：computer vision;color structured light;color object;reflection separation;color separation;color clustering- 65
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Published：2020-08-13 -
Spatio-temporal context tracking algorithm based on dual-object model
Abstract：The original spatio-temporal context (STC) tracking algorithm does not take the tracking results into account when it updates an object model, so the object model is wrongly updated and hard to be recovered after long term occlusion. To solve this problem, an improved spatio-temporal context tracking algorithm based on a dual-object model is proposed in this paper. In this method, an auxiliary object model is introduced to evaluate the effectiveness of original STC algorithm, and to update the object model based on the tracking results accordingly. By using texture information rather than correlation information as the characteristics, the auxiliary object model evaluates exactly the updated contents and corrects wrong updates after long-term occlusion. Experimental results on several groups dada sets indicate that the success rate of the proposed algorithm is 82%, and the center location error is 8 pixels. It implements the stable tracking and the tracking precision is superior to that of the original STC algorithm in complex scenes, especially after long-term occlusions.Keywords：object tracking;Spatio-temporal Context (STC) tracking algorithm;dual-object model;cascade classifier- 61
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Published：2020-08-13 -
Slice interpolation on multilevel modified curvature-based registration
Abstract：When 3D medical and industrial images are reconstructed, the differences of volume data resolution in three directions often lead to detail missing and surface discontinuous. Therefore, a slice interpolation algorithm was proposed based on multilevel modified curvature-based registration. With the method, a back projection method was used to enhance the image details and to improve the definition and contrast of the matched images. Then, the cubic convolution interpolation was used to construct a low resolution image for preserving image detail and to improve the matching accuracy. A new scheme from low resolution coarse registration to high resolution fine registration was proposed to reduce the calculation time to improve the calculation efficiency. Furthermore, a modified curvature-based registration model was built based on the symmetric transformation between the pixels in the slice images to resolve the problem of transformation inconsistency in image matching. Finally, the Discrete Cosine Transform, (DCT)was used to minimize and optimize the joint criterion of a deformation field and the deformation field data were used to perform the linear interpolation for the slice to obtain the slice image. Experiment results show the proposed method eliminates the blurred edges of the slice interpolation image. As compared with the linear interpolation method, the Mean Square Deviation(MSD) of the proposed method has reduced by 40%, which is higher than that of the classical curvature mode and the time consuming also is 20% that of the classical one.Keywords：image reconstruction;volume data reconstruction;slice interpolation;curvature-based registration;image registration- 70
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Published：2020-08-13
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