2014 Vol. 43, No. S1
2014, 43(S1): 1-7.
Laser radar can obtain the three-dimensional shape information of objects, which is an effective method to identify vehicle on complex ground. A fast laser radar target recognition method based on projection dimension reduction was proposed in this paper. Firstly, the suspected target area was extracted and tested from the scene. Then the digital surface model(DSM) data was obtained. Finally, the combination of contour similarity measure value and the similarity of size measurement acted as the matching recognition criteria for target recognition. The experiments were performed by using the simulated point clouds data of 8 ground armored targets. The results show that the type recognition rate of this method is above 90%, and the real-time performance is far superior to the traditional algorithms. In view of the practical application, the influences of point cloud spatial resolution and laser radar system noise on target recognition were further studied.
2014, 43(S1): 8-12.
When pulse laser ranging for a non-cooperative target in space, due to the large distance span of the target, the corresponding echo signal dynamic range is also great. Single method of optical or electronic adjustment can't meet the requirements of whole range receiving. According to the different distance range, in the transmitter the output beam of pulsed fiber laser and pulsed solid state laser was coaxial by polarization beam combiner and the laser emission power was classified. In the receiver the magnification of avalanche photodiode was also classified. Introducing a narrow-pulse peak detector and a variable gain amplifier, the output of the receiving circuit was stabilized by closed-loop automatic control. The equivalent input dynamic range of 160 dB and measuring range of 15 m-20 km was realized in a pulse laser ranging system.
2014, 43(S1): 13-17.
Satellite atmospheric remote sensing by spaceborne lidar is a new type of active detection means after infrared, visible and microwave methods and data retrieval is the key technology of satellite applications. The measurement of atmosphere gas concentration, aerosol/cloud profile and three-dimensional wind is main application field of spaceborne lidar remote sensing. For atmospheric CO2 and aerosol/cloud, the space-based laser differential absorption and backscatter detection principle were introduced and the CO2 bottom-up inversion algorithm and aerosol/cloud level lookup and classification inversion algorithm were also explored. In addition, the ground and airborne verification means for satellite remote sensing data products were provided. This work can aid for top-level design of satellite.
2014, 43(S1): 18-23.
The rotating parts on the spacecraft can seriously disturb working payload. In order to decrease this effect, electronic magnetic technology was applied to adaptive vibration absorber. This EM frequency control system worked through the repulsions from two electromagnets: when the central magnet left the balance place, repulsions of the electromagnets on both sides of the magnet would change. Because of the nonlinearity of the repulsions, the combining force would point to the balance just like a restoring force. Theoretical analysis showed that if the distance between the two electromagnets was sufficiently small, such restoring force was proportional to the displacement of central magnet from the balance place. Furthermore, it was also proportional to the currency in the electromagnet. These conclusions are supported by simulation too. That means it can be taken as the base of an effective, high-accurate DVA control method. According to the theoretical calculation and FEM simulation results, the whole system can change its stiffness in a range of 4 500 N/m. Through choosing right mass ratio, the adaptive vibration absorber could adjust its working frequency in a range of 50 Hz. The performance of the vibration absorber can meet the need of spacecraft.
2014, 43(S1): 24-29.
Based on the secondary geodesic line method and the geometric characteristic of parabolic reflector, the approximate secondary geodesic line method was obtained. To get the expansion boundary of the space film in plane, polynomial fitting for the discrete point on the tailoring line was conducted. And the effects of the tailoring step length and tailoring film projection angle were analyzed. The results showed that step length affects the accuracy of tailoring less than projection angle. The error was only 0.27% when the projection angle was 10. The deformation analysis of the reflector was achieved by using beam structure for equivalence of the thin film. The equivalent method could avoid large deformation caused by the force out of thin film. Load test for the reflector was carried to verify the correct of the equivalent method. Spotlight experiment was conducted based on the tailoring analysis and deformation research. The spotlight result is good. The tailoring analysis method and equivalence method can be the bases of the design for large reflector.
2014, 43(S1): 30-35.
As the interface with the outside space environment simulation system, optical window is an indispensable important component parts. Space environment simulation system consists of two types of optical window. Based on both the windows, in this paper, components structure scheme design was carried out respectively. The strength theory formula was used to check the intensity of the window components; The finite element analysis software was used to calculate the effect of pressure on the optical glass surface deformation, and to analyze the impact of optical glass surface deformation results of the optical properties of the optical window assembly. The results show that aperture 150 mm, the work stress of optical window assembly is 0.82 MPa; Aperture 350 mm, the work stress is 3.28 MPa, meet the strength requirements. Zemax software was used to calculate the wavefront error(PV)of aperture 150 mm optical window assembly is /8; within 170 mm-190 mm band area, the optical path difference of aperture 350mm optical window assembly is 0.8 nm; Both of them can satisfy the requirements of optical performance. Therefore, this design meets not only the strength and reliability requirements, but also the optical performance requirements, So the design of entire window assembly is safe and reliable.
2014, 43(S1): 36-42.
Aimed at solving the contradiction between the need of large diameter condensation structure for Space Power System and the limitation of the current carrying capacity, a deployable mechanism for the secondary mirror support was designed, based on a two-mirror off-axis condensation system. The major configuration of the deployment mechanism was made of a three-link serial mechanism, with two parallel four-bar mechanisms, which can deploy in the horizontal and vertical directions separately, and ensure that the secondary mirror component remains translational movement during the mechanism deployment. Kinematics equation of deployment was deduced, and the work space was solved to plan the scheme of the mechanism deployment. The position precision and attitude accuracy of the deployment was studied, and the sensitivity of structure parameters was given. Finally, the virtual prototype of the mechanism was built with ADAMS software, and the deployment was simulated to verify the correctness and rationality of the design.
2014, 43(S1): 43-48.
As the power transmission components of the vibration test of the satellite, the stand or fall of fixture performance directly affect the authenticity and reliability of the vibration test. The general design method of satellite vibration fixture was summarized, and a vibration fixture design work for a certain satellite was done very well. The dynamic characteristics of vibration fixture, such as the stiffness, quality and the natural frequency and dynamic response, were studied by using the finite element software MSC. NASTRAN. The analysis results shows that mean deviation of the dynamic characteristic response is about 6%, the maximum response deviation is about 11%. It is a reasonable range that the vibration fixture impact on the entire satellite dynamic characteristics. Now the vibration fixture has been successfully applied to the ground mechanics environmental test of a certain satellite which according to the mechanics experiment environment standard of GJB1032-90, and the expected results has been achieved. The method can also been applied to other satellite vibration fixture design process.
2014, 43(S1): 49-52.
In high-energetic particle burst experiment, target monitoring system has the function of bremsstrahlung conversion target filament accurate positioning, and acquiring the dynamic image of bremsstrahlung conversion target filament in experiment. First, an accurate positioning system of the micro target filament was designed to monitor the original position, according to the binocular stereo vision theory. Then, ICCD camera lens was developed to record the dynamic image collision experiment in working conditions. Finally, an experiment platform simulating the real using condition was established to test the positioning accuracy error of this system and high optical resolution. The experiment results indicate that the accuracy error of this positioning system is 2%, and the optical resolution of ICCD camera lens is better than 600 lp/mm, which illustrate that this built positioning system can reach the goal of the accurate positioning of the bremsstrahlung conversion target filament in the high-energetic particle burst experiments, and ICCD camera lens can meet the need of high-energetic particle burst experiment.
2014, 43(S1): 53-58.
The space to earth observation small satellite borne smart integration design was studied, combined with the engineering practice, the structure design of a dexterous small satellite. The organic combination of load structure and satellite structure together, and full consideration was given on the integration of design, structure and layout of the whole satellite cable, satellite integrated design of satellite structure and the entire star passive thermal control, the function density of the whole satellite was improved, onboard single computer layout was optimized, the entire star quality was effectively reduced, compression volume, and lower launch costs application were completed. Design and analysis results show that, the natural frequency of the entire star x is 56.465 Hz, the natural frequency of y is 59.704 Hz, the natural frequency of z is 218.88 Hz, the whole star high stiffness lay the foundation on fast mobile imaging smart satellite; large safety margin is reached 3.85 with random response and sine response in the controllable range, can withstand complex mechanical environment from transport to various emission process; satellite high functional density, passive thermal control design makes the whole satellite thermal control resources small power consumption with high space utilization rate, simple and convenient cable layout.
2014, 43(S1): 59-64.
With the development of information technology, space imaging has been developed toward high-definition and multi-channel direction. Real-time video compression system, based on general-purpose DSP and H.264/AVC video coding standard, due to short development cycle, high reliability, high processing speed, ease of upgrades, small size, low power consumption and high adaptability, can provide a solution for the new requirements. Therefore, it is of great importance to study real-time video encoder based on general-purpose DSP and advanced video compression technology. To meet the application needs of more and more high-definition video capture, coding and transmission, TI's new generation multi-core TMS320DM8168 chip was used for development, and the design and implementation of system was proposed, and then the H.264 video encode algorithm was realized for dual 1080p input video. The main processor of the scheme needs only a piece of DSP. Compared with the traditional video compression schemes which need multi processor, this highly integrated scheme reduces the number of parts and materials(BOM)cost, power requirements and the size of PCB, and increases the system integration.
2014, 43(S1): 65-71.
Kinematics analysis and driver design of multi-module deployable structure Due to the deployment need of deployable structure in space missions, kinematics analysis and driver design of the structure were important. Based on the studied space multi-module deployable structure with the periodicity characteristics of single module in circumference direction and incompletely periodicity of the multi-module linkage, kinematics modeling of single module was conducted by using plural and decomposed method. At the same time, the kinematics model of multi-module deployable structure was established, which satisfies the aimed surface fitting. Then kinematics analysis of multi-module deployable structure was achieved to get the relationship curve between the location of the moving parts and the deflection of the modules. It was found that the deflections of the modules increase with the displacement of slider and reach 1.22 degrees. Based on the kinematics analysis of structure, the force curves of the sliders and the joints under different driver styles during deploying are given. The diver analysis and driver design with low mass and high reliability for deployable structure which can guarantee the smoothly deploying.
2014, 43(S1): 72-77.
Two kinds of solar-sail attitude control mechanism were described in this paper, one was the centroid offet class, the other was the sail plane rotating class. Advantages and disadvantages of these two kinds of attitude control mechanism were analyzed. An attitude control roll stabilizer barsis was designed which was suitable for a kind of square solar sail which had extension boom and square sail surface. The boom's length of roll stabilizer bars is the key parameter, it was optimized under some constraints such as: configuration design, material strength, structural strength, quality optimization and control accuracy, it was calculated and verified through geometry relations and nonlinear static finite element simulation. The simulation result was 1.2 m. The rotate speed limit was obtained by power and speed relation formula according to the result of the boom's length, which was 20.83 ()/s. In this paper, an optimization design idea of roll stabilizer bars boom's length was given. The calculation and simulation results provide the key design parameters and design conditions for the solar-sail spacecraft attitude control system design, and the optimization results have reference value for practical engineering applications.
2014, 43(S1): 78-82.
In order to remedy the traditional target reporting, improve the efficiency of target reporting in training of airborneweapon-attacking over the ground, and put forward new method to realize real-time automatic target reporting in battlefields, the design method of the realization of real-time automatic target reporting system for simulant airborneweapon attacking over the ground was put forward by using intersection measurement method theory and adopting CCD imaging principle, image analysis method, the function of pick up all dynamic target, the function of correcting for distortional image, calculation of image threshold and method of focus(center of mass) extraction were solved, and the real-time measurement, caclulation, record and analysysis of hit points were realized. The result of experiment has proved that the capture rate of this system for light spot in the field of view is more than 97%, the relative error of hit points' coordinate is less than 0.23%.
2014, 43(S1): 83-88.
For some 1.1 m diameter space mirror opto-mechanical design task, in order to decrease the weight of the mirror, improve its environmental adaptability, a small gravity deformation and strong vibration resistance, high thermal stability of space mirror structure system was designed. Firstly, mirror and support structure material selection principles and the matters needing attention were analyzed in detail. Then, a semi-closed back with a fan-shaped lightweight hole mirror lightweight structure schemes was proposed, and by using the method of parametric modeling, analysis of its structural parameters optimization design was carried out. The back three-point flexible support scheme was used to support the mirror. By adjusting the flexibility of flexure hinge can solve the problem of mirror surface figure accuracy degradation caused by assembly position and thermal environment change. Finally, on the mechanical and thermal properties of the mirror subassembly analysis results show that, the surface figure accuracy of the mirror was PV 62.4 nm and RMS 5.7 nm under load case of 1 g gravity in the direction of X axis, in the 204 ℃ environment temperature range the surface figure accuracy reached PV 61.7 nm, RMS 6.3 nm, and the fundamental frequency of the mirror subassembly was 150 Hz which can satisfy the static stiffness, dynamic stiffness and thermal dimensional stability index requirements.
2014, 43(S1): 89-94.
The Methods was proposed based on the analysis of Modulation Transfer Function(MTF) test error of spaceborne TDI CCD camera, the influence from grating period error, environment vibration and imaging noise was retained from MTF testing. The MTF testing is affected by grating period error, environment vibration and imaging noise. Through analyzing the influence mechanism, a mathematic module was established to describe the influence of grating period error, environment vibration and imaging noise. The correcting algorithm of the testing MTF error from grating period error was proposed, and the optimization mask of MTF testing was also proposed to reduce the influence from image noise. Based on the testing images, the horizontal scale of MTF mask should not exceed 4% of the Morie fringe horizontal period, the vertical scale of MTF mask should not exceed 2% of the Morie fringe vertical period. The analysis shows that if the mask is larger, the influence from noise is reduced, but the influences from the environment vibration and grating period error will increase. In the real project, the mask scale should be selected based on the imaging system noise level, and ensure the accuracy of the MTF testing.
2014, 43(S1): 95-100.
The measurement system of the surface backscattering characteristic was designed and setup in this paper. The send and receive in system was coaxial inhemisphere space. The laser is 1 550 nm linear polarization and narrow linewidth. The backscattering characteristic of grinding, vertical milling and plain milling samples with different surface microstructure was measured at different incidence angles from 0 to 60. The effect of the incident light polarization direction, azimuth angle, incidence angle and the surface microstructure on the backscattering was discussed. The reasons of these effects and the change of backscattering characteristic were analyzed. It was found that the incident light polarization direction, azimuth angle, incidence angle and the surface microstructure had regularity effect on the backscattering. They had both the common law, also had individual character. Surface microstructure determined the backscattering energy distribution and polarization characteristic with the change of incidence azimuth and angles. This result shall provide the reference value to the research of cooperation target measurement field and other surface measuring field.
2014, 43(S1): 101-107.
The large aperture primary mirror(PM) is the key component of space remote sensor. The mirror's stiffness and strength effect on the image quality crucially. In the early days of structural design, FEM analysis and dynamic test were performed on a Ф750 mm primary mirror assembly(PMA) to predict its maximum stress response under random vibration for safety margin. Firstly, the dynamic environment undergone was discussed by the space remote sensor and the equivalent sinusoidal load for random vibration. Then, the FEM model of PMA was built up to simulate the dynamic response using the equivalent loadcriterion. Finally, the dummy primary mirror made of Al alloy was manufactured and dynamic test was performed to acquire the stress response. The analysis and experiment results show that the maximum stress of PMA flexure under random vibrationare is 102.3 MPa、99.5 MPa、104.3 MPa, differ from the analysis result by 10.8%. The analysis accuracy is verified by test results, indicating that the flexure design is reliable to have a safety factor of 2.07, and the PMA can satisfy the design demands.
2014, 43(S1): 108-115.
A rapid attitude maneuver method of flexible satellite based on control moment gyroscope was presented. Combining the attitude dynamical equation, kinematic equation and vibration equation of flexible parts, the nonlinear predictive equation was given. Based on the optimization objective including tracking error, the energy of control moment and the energy of flexible parts, the nonlinear model predictive control method was used to propose the attitude maneuver law which had the rapid maneuver performance and attenuate the vibration of flexible parts. To further attenuate the flexible part's vibration, the input shaping method was applied to obtain the actual commands of control moment. Based on the actual control commands, the steering law of CMG pyramidal configuration was designed using the robust inverse approach, and achieved the moving optimization control of flexible satellite attitude maneuver. Simulation result indicates that, the designed control method can achieve 50 large attitude maneuver in 27 s, and the corresponding pointing accuracy and stability are 0.03and 0.03()/s.
2014, 43(S1): 116-122.
Solution of target pose is influenced by measurement error of 3D coordinate of target feature points directly, to determine error factors that influence target pose accurately, distribution and comprehensive on the errors reasonably is the key to improve measurement precision. At present, the accuracy of point extraction and feature points matching has reached a bottleneck according to the existing algorithm, but the internal structure and calibration of the camera which can reduce the measuring error has huge research space. In this paper, through establishing the coordinate measuring equation of image point, the impact of various error factors on location of the target was analyzed synthetically. Through the experimental analysis and simulation, the errors of internal structure and calibration which impact on the coordinate of imaging point is within a pixel, when f=0.031 9 m, and the distance of target is 20 m, measurement accuracy of the target is 0.029 4 m. It has great reference value on the design of the internal structure of optical imaging system and the selection of electronic devices.
2014, 43(S1): 123-129.
In order to detect electromechanical actuator fatal fault, an electromechanical actuator standard state sample was established according to fuzzy cluster method. Electromechanical actuator state can be classified to certain types by calculating least approximation distance between waiting test state sample and standard sample, so the state detection was realized. First, some original electromechanical actuator state sample data has been normalized. Then fuzzy similar matrix between each sample was established based on angle cosine law. After that iterative calculation of clustering center matrix and membership matrix was started. And iterative process was ended through setting maximum iterative error. So the standard state sample was obtained. Finally, test platform is established for state detection. The real-time state detection program runs in the electromechanical actuator controller in continuous operation test. And the program calculates distance of the sample under test and standard state sample. Experimental results indicate that runtime of electromechanical actuator state detection program just need 0.23us, and detection conclusion is completely right. This state detection method can satisfy the requirements of veracity and real-time for electromechanical actuator fault detection.
2014, 43(S1): 130-138.
With the development of space technology, satellite thermal control systems face new challenges. First, a detailed comparison of traditional and responsive thermal control systems was presented according to the characters of small speedy responsive space satellites, and then a new design process was derived for responsive thermal control systems. Each of the key technologies including a single hot and cold case design orbits, modular thermal architectures, fast analysis and virtual test method was introduced. Finally, the advanced equipment and materials for responsive thermal control were reviewed. In a word, the author considers that a robust modular scalable thermal control with new advanced smart thermal control device was the certain requirement and way to implement responsive thermal control systems.
2014, 43(S1): 139-144.
The Pulse Per Second(PPS) signal of Global Positioning System(GPS) receiver has large random error and the onboard clock exists cumulative error. Based on analyzing normal distribution characteristics of the PPS signal of GPS, the real-time correction algorithms for reference source of PPS and clock were proposed. In the real-time correction algorithms for reference source of PPS, the average value of pulse number in one second was obtained by averaging high frequency pulse accumulation, the average value of time error was obtained by averaging the pulse number of the time error between predict second pulse and coordinated universal time(UTC), thereby generating corrected second pulse. On the basis of the actual frequency of Temperature Compensated Crastal Oscillato(TCXO) which is obtained by the average method, pulse compensation algorithm was studied which is used for correcting the clock reference source. Simulation and experiment results show that the random error decreases 7.5 times by the use of real-time correction algorithm for reference source of PPS. Test error is less than 140 ns in 9.5 hours by the use of real-time correction algorithm for reference source of clock. The real-time correction algorithm for reference source can effectively reduce the errors based on PPS signal of GPS.
2014, 43(S1): 145-150.
To solve the non-uniformity response of multiple outputs in TDI CCD imaging systems, every factors that may influence the non-uniformity response were analyzed in detail according to the flow of video signal process. Compared with popular correction methods of non-uniformity response, an improved method based on single point calibration was proposed, which integrated the advance of single-point correction and two-point correction methods. The improved single-point method has the features of simple algorithm, high efficiency, good practical application, low work of measurement, and so on. The results of experiments show that the non-uniformity response of TDI CCD imaging system declines from 3.5% to 1.5% according to the images using the improved method of single point calibration. The maximum of non-uniformity responses among multiple outputs is less than 2.5% during the full response range. The improved method of single-point calibration can satisfy the requirements of TDI CCD image systems and be practical in engineering.
2014, 43(S1): 151-156.
For better testing and calibrating the space-used telescope, a novel calculating model was introduced to simulate tracing process of the satellite. The coordinate transform theory was used for the indoor rotating target, the result was coincident with the spherical trigonometry. A model was deduced to illustrate the relationship between the tracing errors and the position errors of detecting system and the telescope gyration centre. The result showed that, a position error of 0.2 m in the vertical axis direction simply causing a constant elevation angle tracing error of 5.658 74, without any influence on other tracing performance. An error of 0.002 m in the horizontal axis direction caused coupling tracing errors both in azimuth and elevation measurements, the azimuth angle tracing error ranged between 0.056 78~0.139 25, azimuth angular velocity error was 0.007 01 per second, the azimuth angular acceleration error was 0.002 56 degree per second square, while the elevation angle tracing error was about 10-4 order of magnitude, and the angular velocity and angular acceleration was about 10-6 order of magnitude. The tracing performance was independent of position error in the collimation axis direction. This conclusion provides reference for testing and assembling space-used telescope.
2014, 43(S1): 157-163.
In order to meet the needs of low-cost, high integration space instruments for space power systems, a space-based instrument C8051F040 chip power controller was designed. The major difference between the controller and the traditional design approach is the use of highly integrated lithium-ion battery controller chip (bq77PL900) as an integrated controller chip instead of analog circuits. By employing the bq77PL900, the size of power controller is reduced and the energy of the power controller used is decreased, and the anti-jamming ability of the system is enhanced. To improve the reliability of the system, the system uses the online EEPROM re-injection technology, which can be used to discover the knocked data. This experiment proves that this design not only greatly simple and reliable, but also enhance the efficiency of the system by 5%. This design can wildly used in low-cost space instruments and small satellites.
2014, 43(S1): 164-168.
SRAM-based FPGA in the space radiation environment is effected by single event, which leads to the occurrence of FPGA memory cell bit flip. When the flip up to a certain extent, the function may become errors. To assess the sensitivity of FPGA single event and improve the reliability of FPGA single event, the key technology to realize fault injection was studied, the existing technology was analyzed, SEU sensitive bit test system was designed, based on partial reconfiguration feature of SRAM-based FPGA, and the modified FPGA configuration data bits was used to simulate a fault zone, the method accelerated the process of system failure, realized the single event upset sensitive position detection and statistics. Experiments show that the design is reasonable, implementation is flexibale, and cost is low, and provides favorable support for SRAM-based FPGA anti-tolerant design.
2014, 43(S1): 169-176.
One of the major problems that restricts the widely use of hard and brittle materials is the quality and efficiency of fabrication. To deal with this,improving fabricaiton efficiency and quality of hard and brittle materials needs to be quickly solved. To a large extent, high efficiency could imply the quality may get worse. Keeping up high efficiency and good quality seems to be contradictory in the meantime. Since the grinding thermal situation was one of the key elements that could affect the fabrication quality, this article aims to analyze the thermal situation in the process of fabrication of carbon dioxide and aluminum oxide by studying the relationships between grinding temperature and grinding parameters which include grinding wheel linear velocity, grinding depth and workpiece speed. In the meanwhile, it compared the thermal results between carbon dioxide and aluminum oxide in purpose of providing useful information and reference for fabrication.
2014, 43(S1): 177-182.
A high-accuracy temperature control system for light filter of auroral imager was proposed in the paper. Platinum resistance was used as the temperature sensor, and the temperature measuring circuit can collect the temperature with an accuracy of 0.05 ℃. A DSP was used as the main control unit, which implemented a full digital control system. The heater plate used constant current source circuit as its driving circuit, implementing the high precision and low noise heating power control. The mathematical model of the system was established, and the key parameters were identified from step response curves of the practical light filter system. The controller was designed based on the identified model and simulation results show the performance of the designed controller. Then, the parameters of the controller were tuned in experiments and experiment results show that better performance is obtained using optimized controller. At last, experiments results were discussed and show that high accuracy temperature control of the light filter system was implemented.
2014, 43(S1): 183-187.
The stability of space remote pointing mirror plays a vital role in improving image geometric accuracy, and it is determined by adhesives. First of all, the requirement of remote sensor to pointing mirror's stability was analyzed in this paper. Then the three commonly used for aerospace adhesive were compared comprehensively. Combining with the actual requirements of pointing mirror, HY914 and SE-14-80 adhesives were chose to compare the stress of glue bonding. By setting a reasonable curing process for both adhesives, and under the same conditions, the pointing stability was examined before and after the test verification. Experimental results show that with the specific curing process,the pointing error of pointing mirror using SE-14-80 adhesive was 1 before and after bonding, and SE-14-80 is more suitable for use in bonding in space optical remote sensor pointing mirror. Given its excellent adhesion, this adhesive is applied in a research project.
2014, 43(S1): 188-192.
The gel-casting of reaction bonded silicon carbide, which is a material of space mirror, was processed by organic precursor impregnation. A silicon carbide ceramic component with fine secondary -SiC distributed uniformly in the matrix was prepared. The density and the microstructure in the impregnation process were investigated. The density of the sample without impregnation process was 2.945 g/cm3 after reaction sintered. Density increased to 2.969 g/cm3 after one time impregnation, and increased to 3.011 g/cm3 after two times impregnation. The proportion of fine SiC in microstructure went up with the increasing of the impregnation times. In which the reaction sintered process, the carbon introduced by impregnation and silicon reacted to form fine -SiC dispersed in matrix. Bending test was conducted for the samples. The bending strength of the sample without impregnation process was 308 Mpa. Bending strength increased to 339 Mpa after one time impregnation, strength increased by 10.1%, and increased to 380 MPa after two times impregnation, strength increased by 23.4%, which improve the mechanical properties greatly.
2014, 43(S1): 193-196.
The join slurry is composed by silicon carbide(SiC) powder, phenolic resin and carbon black. Joining SiC green body after deairing, and then the reaction bonded SiC(RBSiC) joining mirror blank was prepared by reaction sintering. The relationship of the slurry formula and the microstructure of weld were discussed. The bending strength and the coefficient of thermal expansion of joining RBSiC ceramic were tested. The research shows that PEG200 and PVP can make carbon black dispersing homogeneous in the join slurry, and there is no residual carbon black in the weld after reaction sintering, so the microstructure of RBSiC ceramic is no different from the weld. The blending strength of joining green body and joining RBSiC ceramic are 24.9 MPa and 322.9 MP arespectively, and the fracture occurred in the base material. The CTE of base and weld material is only 0.011 4 ppm during -100-400 ℃.
2014, 43(S1): 197-202.
The effects of nano-SiC power additive on rheological behavior of SiC slurry and mechanical properties of RBSC were investigated. SiC blanks were prepared with gel-casting method, through drying, burning out the organic elements, infiltrating silicon and reaction sintering, the RBSC with nano-SiC particles were fabricated. Influence of solid loading, ball-milling time and nano-SiC particles on rheological behavior of SiC slurry was discussed. Due to the addition of nano-SiC particles, SiC slurry rheological behavior was changed from shear thinning to first shear thickening, then shear thinning. With 7% nano-SiC powder, the bending strength and elastic modulus of RBSC were elevated to 345 MPa and 339 GPa,respectively increasing by 18.1% and 13.8%. RBSC mechanical properties were improved with the addition of nano-SiC powder.
2014, 43(S1): 203-208.
In order to achieve a clear dynamic staring imaging, the imaging model of satellite real-time imaging to track the target was designed, body posture angular velocity relative orbital coordinate system were designed when satellite staring imaging, the coordinate transformation method was used to real-time compute the time of the line transfer process in the gazing, the method of Monte Carlo was used to statistical calculate the influence of imaging under the satellite's attitude point precision and stability in the mode of staring-imaging. Finally, the CMOS prototype and the minitype three-axis air bearing table constructed for attitude control were used to simulate the digital domain CMOS staring imaging.The results show that in the satellite staring imaging process, the integration time in the image plane which caused by satellite attitude change and attitude dynamic tracking is greater than the accuracy of the detector, analysis and simulation results show, in order to meet shift of less than or equal to the detection element size requirements, simulation platform dynamic tracking accuracy better than 0.002()/s, can achieve satellite getting 2 m clear resolution dynamic imaging in 500 km.
2014, 43(S1): 209-213.
At present, there are some conditions in the research field of the space camera. For example, the imaging mode is single of the optical imaging reconnaissance satellite in our country. The detection efficiency of the satellite is very low for banded target curve. Therefore, it need to carry out a research about the new drift adjusting method of the space camera. This research requires a basis that is the real time compensation technology for the image motion of the camera. First, the theory of the new drift adjusting method of the space camera was introduced, and a drift adjusting mechanism was designed. This mechanism can make the space camera with the real time compensation technology for the image motion. At present, the traditional drift adjusting method is that making all of the TDI-CCDs which have been assembled running together. Know from this, the new drift adjusting method make the TDI-CCD running singly to achieve the time compensation. At last, the transmission accuracy of the flow deviation was analyzed and tested. The test results show that there are many advantages of the drift adjusting mechanism which designed in this article, such as the transmission accuracy is high, and the response speed of structure system is quickly. With this drift mechanism, the space camera can complete the agile imaging reconnaissance tasks.
2014, 43(S1): 214-218.
To resolve the problem that brought by the complex drift angle adjusting structure in the current image motion compensation method, a new drift angle adjusting method based on image was proposed in this paper, which was suitable for the CMOS remote sensing cameras based on TDI in digital domain. The method was based on digital images, and accumulates the matching image pixel in digital domain to adjusts the image motion mismatch caused by the drift angle. Finally, in order to verify the effectiveness of the proposed algorithm, the imaging experiment was conducted. And the results show that when the drift angle is 26.56 degrees, the of the image gotten directly before using the proposed algorithm is 0.132 8, while the contrast transfer function is increased to 0.444 7 after using the proposed method. So it proves that the drift angle adjusting method based on image can improve imaging results significantly and is feasible and effective. The proposed method gets rid of the limit of the idea of adjusting the drift angle by mechanical structure, and it is of high precision but simple, without the need for any additional hardware expenses, which is helpful to improve the current image motion compensation system.
2014, 43(S1): 219-224.
In order to detect soluble solids content(SSC) of apple conveniently and rapidly, a portable apple soluble solids content spectrometer was designed with ARM9 as controller, miniature spectrometer as spectrum detector, WinCE as embedded operating system. The total number of 80 apples was for the calibration(n=60) and prediction(n=20) sets. Different spectral pretreatment methods, including smoothing, standard normal variate(SNV) and multiplicative scatter correction(MSC) were performed. Uninformative variable elimination(UVE) and successive projections algorithm(SPA) were proposed to select effective wavelength variables. Partial least squares(PLS) models combined with whole wavelength and selected wavelengths were established to detect SSC of apple. The results indicated that the best model was developed using PLS with respect to the spectra in whole wavelength range. The correlation coefficient (Rp) and root mean square error of prediction(RMSEP) for prediction sets were 0.853, 0.534 for SSC. The model is reliable and the predicted result is effective. The meter can meet the requirement of quick measuring SSC of apple. The study can provide a reference for development of portable apple soluble solids content spectrometer.
2014, 43(S1): 225-230.
In order to improve the efficiency and accuracy of the projected grating three-dimensional measurement system, a sub-pixel matching method based on epipolar line rectification was proposed. Firstly, the epipolar line rectification algorithm was used to transform the bi-stereo geometry into the epipolar standard geometry, so the certain point on the left image had the same horizontal epipolar line with the same row coordinate on the right image. Then, the new phase images of left and right camera were achieved by bilinear interpolation algorithm, and the initial matching points were obtained using the proposed method of stereo matching algorithm based on phase region matching. Thirdly, the local minimum of the surface was achieved by the least squares fitting of 33 neighborhood similarity metric of the initial matching points to be a quadratic surface. Then the right camera matching point coordinate was acquired which had the same phase with the left camera matching point. The planeness of a standard planar was measured to evaluate the accuracy of the proposed method. The results show that the proposed method can achieve the stereo matching fastly and accurately.
2014, 43(S1): 231-237.
Random dot stereograms were used to study the factors of the key problem that existed in the visual comfort of stereo display and was caused by stereo vision comfortable fusion. Subjective behavior experiments were done to analysis the factors to affect CFL(Comfortable fusion limits) of stereo vision by changing the size and shape of a hidden graph, the dots density and dot size in random dot stereograms. Then a prediction model of these factors to CFL was put forward. The results showed that these factors had different influences on CFL under crossed disparity and uncrossed disparity. Under uncrossed disparity, the subjects can stand bigger size of hidden graph, and the perception of fusion limit for the shape is opposite to the perception under crossed disparity. Correlation detection was measured between the prediction values calculated by the prediction model and the measured values. The correlation coefficient achieved 0.998 and 0.977, respectively, under crossed disparity and uncrossed disparity, which indicated that the prediction model could more accurately predict the CFL.
2014, 43(S1): 238-242.
Digital imaging devices require color space characterization while transferring or showing image between various devices which is a crucial part of color management for digital devices. In order to keep the color reproduction ability for output image, a high dynamic range digital(HDR) camera requires characterization based on the device properties. For existing characterization algorithms, which are in most cases for 8-bit-digital cameras, the processes of transformation matrix calibration are involved in some complex approaches, which are easy to cause system errors and influence the precision of color space transformation matrix. Accordingly, a color management approach was proposed for a high dynamic range colorful digital camera that using a color space mapping from camera RGB space to CIE1931 XYZ color space to estimate the function relation between two color spaces and using the least square method to achieve color matrix calibration. Eventually the camera RGB color space was transformed to sRGB standard color space which achieves characterization for HDR camera. Experimental results show that this method is of good robustness and easy to realize as well as the mean square error is less than 0.08.
2014, 43(S1): 243-247.
The existing Singular Value Decomposition (SVD) based color information encryption system provided an optical matrix composition scheme, secure ciphertexts and very sensitive keys. As the Higher-order SVD (HOSVD) is a natural multi-linear extension of the matrix SVD, an HOSVD based color image encryption algorithm was proposed. In the encryption procedure, HOSVD can generate more multiplication orders of the ciphertexts (decomposition parts) than what SVD provides. These multiplication orders can be used as effective keys to make unauthorized decryption harder. In the decryption procedure, the reconstruction accuracy of HOSVD is higher than that of SVD. These advantages enhance the accuracy, security and robustness. Numerical simulations based on a test dataset of 100 images support the viability of the proposed algorithm.
