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25 December 2012, Volume 32 Issue 6 Previous Issue    Next Issue

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ModelReducedMethodviaReverseProjectionfromBalancedSpacetoModalSpace CAO Li, ZHOU Zhi-Cheng, QU Guang-Ji 2012, 32 (6):  1-7.  doi: 10.3780/j.issn.1000-758X.2012.06.001 Abstract ( 1538 )   PDF (398KB) ( 1490 )   Save Duetotheindistinctphysicalmeaningsforinternalbalancingreductionandthedifficultyinextractingbalancecoordinatesfromsensorreadings,amodelreducedmethodfrombalancedspacetomodalspacewaspresentedviareverseprojectionbasedonthedynamicsmodelofflexiblespacecraft.Accordingtotheinvarianceofthetransferfunctionandtheeigenvaluesforstatespacetransformation,theeigenfrequencieswereobtainedbythezero-poletransferfunctionofbalancedreducedmodel.Thecorrespondingrelationshipbetweenthebalancedstatesandmodalcoordinateswasgivenandthereverseprojectionmatrixwasconstructed.Thefrequencyresponseandcontrollabilityandobservabilityanalysisshowsthatthestatesofreducedmodelinmodalsubspaceandthestatesoforiginalmodelarematched.Thereducedmodelwithdefinitephysicalmeaningisapplicabletosubsequentstructuralcontroldesign. Related Articles | Metrics

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Progress in Calculation Methods for Collision Probability of Spacecraft YANG Wei-Wei, ZHAO Yong, CHEN Xiao-Qian, WANG Zhen-Guo 2012, 32 (6):  8-15.  doi: 10.3780/j.issn.1000-758X.2012.06.002 Abstract ( 1827 )   PDF (577KB) ( 1714 )   Save To investigate the collision detection and prediction,the status and development of spacecraft collision probability computations was presented.Firstly,the characteristics and applicability of typical formulations were summarized for both linear and nonlinear encounters.Secondly,calculation methods of maximum instantaneous collision probability were discussed for certain applications with real-time collision warning requirements.Finally,some challenges and future directions were proposed based on the analysis of recent work.This work will benefit for future research and development in the field of trajectory safety. Related Articles | Metrics

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DesignandAnalysisofAutomaticDrillingSamplingMechanismforLunarExploration PANG Yu, LIU Zhi-Quan, LI Xin-Li 2012, 32 (6):  16-22.  doi: 10.3780/j.issn.1000-758X.2012.06.003 Abstract ( 2261 )   PDF (489KB) ( 1493 )   Save Automaticsamplingmechanismisoneoftheimportanttoolsforlunarexplorationsandplaysakeyroleinobtaininglunarsoilsamples.ThusautomaticsamplingtechniqueisakeytechniqueforChineselunarexplorationmission.Anautomaticdrillingsamplingmechanismschemewithcoaxialdouble-tubedrillsandaflexiblesamplebagpick-upwasputforwardfordeeplayerlunarsoilsampling.Thefunction,constructionandprincipleoftheautomaticdrillingsamplingmechanismweredescribedindetail.Byanalyzingthesamplingmechanicalproperty,theoptimizedresultsshowthatspiralangleis14°,axialspeedis5.7 mm/sandrotaryspeedoftheouterdrillis13.1 rad/s.Toobtainsoilfrom1 mdepth,thediameterofdrilltubecouldbebiggerthan7 mm.ThemechanicalmodelsforbothlunarsoilandthedrillwereestablishedbyABAQUSsoftware.Onthebasisofthesemodels,adynamicalsimulationfordrillingprocesswasperformed.Anaverageresistantforceisabout300 Nandanaverageresistanttorqueofthedrillis7.5N·m,whichprovidesimportantreferencesforengineeringdesignoftheautomaticdrillingsamplingmechanism. Related Articles | Metrics

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ComparisononEKFandUKFforGeomagneticAttitudeEstimationofLEOSatellites YANG Bin, XU Guang-Han, JIN Jin, ZHOU You 2012, 32 (6):  23-30.  doi: 10.3780/j.issn.1000-758X.2012.06.004 Abstract ( 1849 )   PDF (480KB) ( 1549 )   Save AlowEarthorbit(LEO)satellitecanbestabilized    in3-axisbycorporatelyusingamagnetometer,reactionwheelsand3-axismagnetorquerrods.Itischallengingtodeterminate anappropriateattitudeforLEO.Toaddressthischallenge,thealgorithmsofextendedKalmanfilter(EKF)andunscentedKalmanfilter(UKF)werecomparedandasolutionwasproposedbyexploringtheinfluenceofthegeomagneticmodelerror,themagneticmeasurementerrorandtheremanenceontheperformanceofattitudedetermination.Inaddition,thecalculationofmeanandcovariancequaternionwasderived.TheEKFandUKFwereintroducedtoattitudedetermination,andthefactorswhichhaveinfluenceonthealgorithmperformancewerediscussed.Twoalgorithmswerecomparedonestimationaccuracy,convergencetimeandcomputationcomplexity.Withtheaccuracyrequirementsandthehardwarelimitations,theEKFalgorithmwasfinallychosenfortheattitudedetermination.Simulationresultsshowthattheearthpointingaccuracyoftheproposedsolutioncanreach1°withthestabilityof0.1(°)/s. Related Articles | Metrics

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Immersion and Invariance Based Attitude Controllers Subject to Input Saturation and Disturbances HU Jin-Chang, ZHANG Hong-Hua 2012, 32 (6):  31-38.  doi: 10.3780/j.issn.1000-758X.2012.06.005 Abstract ( 2226 )   PDF (435KB) ( 1359 )   Save A new attitude controller was proposed for rigidbody spacecraft subject to input saturation and slow-varying disturbances.Based on the immersion and invariance methodology,the slowvarying disturbances were regarded as unknown parameters and the estimation equation was then derived independent of the control input.The controller was designed based on the estimation of the disturbances,which was simply in the proportional and differential form plus a disturbance compension term.By means of the immersion and invariance method,the following results were obtained:when the disturbance is varying slowly,the attitude tracking errors can be regulated to a ball near the origin that can be arbitrarily small by adjusting some parameters;when the disturbances are constant,the influence of disturbances can be completely eliminated and global asymptotical stability is obtained.Finally,simulations were presented to validate the effectiveness of the proposed control scheme. Related Articles | Metrics

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FootprintOptimizationforRLVBasedonMixOptimalAlgorithm LI Hui-Feng, SUN Guo-Qing, HE Rui-Zhi 2012, 32 (6):  39-46.  doi: 10.3780/j.issn.1000-758X.2012.06.006 Abstract ( 1531 )   PDF (512KB) ( 1527 )   Save Amixoptimalalgorithmwiththebenefitsofbothglobalandlocalalgorithmswasproposedforfootprintoptimizationofreusablelaunchvehicle.Entryflightdynamicswasgiventodescribethefootprintproblem.Optimalbankanglecontrollawwasderivedbasedonthemaximumprincipleandtheconstraintsofthecontrolinputswerediscussed.Initialguessofparameterswasfoundedthroughgeneticalgorithms.Andthen,patternsearchmethodwasusedforrapidandpreciseparametersoptimization.Simulationresultsshowthattheproposedapproachprovidesaconvenientwayforrapidlyfindingfootprintwhileenforcingpathconstraintsandcontrolinputconstraints. Related Articles | Metrics

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OrbitControlforHighResolutionImagingofHong-WanArea ZHENG Ai-Wu, LIU Yong, ZHOU Jian-Ping 2012, 32 (6):  47-53.  doi: 10.3780/j.issn.1000-758X.2012.06.007 Abstract ( 1748 )   PDF (454KB) ( 1016 )   Save InordertoobtainhigherresolutionimagesofthewholelunarsurfaceandtakehighresolutionphotosofHong-Wanarea,whichisoneofthepreselectedlandingsiteofChang′E-3  (CE-3)    mission,theresolutionoftheCCDcameraofChang′E-2 (CE-2) satellitewasimproved.AndanimpulsewastakentomaneuverCE2fromtheheightof100 kmlunarcircularorbittoa100 km/15 kmellipticalorbit，whose perilune height was 15km and apolune height was 100 km tofurtherreducetheorbitalaltitudetotakephotosofHong-Wanareaneartheperilune.However,thesatellitecouldnotstayintheorbitforalongtimebecauseoftheenergylimitation.Thesunelevationoftheorbitwasalsorequiredtobehigherthan 15°forthesakeofhighqualityofimaging.Moreover,theprecisionrequirementsoforbitmeasurementanddeterminationdemandedenoughtrackingarcs.  Alltheserestrictionsbroughtforwardhighrequirementsforthedesign and control of the experiment orbit.Based on the engineering experience of Chang′E-1 mission,the characteristics of 100 km/15 km orbit with only academic stations considered to measure and control the satellite,andtwomethodswerepresentedtocalculatecontrolstrategiesoftheexperimentorbitincludingtimefixedignitionandfueloptimalmaneuveraccordingtotherequirementsoftheimagingconstraintsandorbitdetermination.Theresultsandtheerroranalysesshowthatthedesignmeetstheimagingrequirementsoftheexperimentorbit,anditisfeasiblewiththesafetyassuranceofthesatellite. Related Articles | Metrics

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FX Correlation Scheme and Improvement on Delete Algorithm LU Wei-Tao, YANG Wen-Ge, HONG Jia-Cai, SHI Xue-Shu 2012, 32 (6):  54-61.  doi: 10.3780/j.issn.1000-758X.2012.06.008 Abstract ( 1906 )   PDF (499KB) ( 1390 )   Save Based on the analysis of the FX correlation in interferometry technology such as VLBI,a novel FX correlation scheme was proposed.The new scheme reduced the timedelay between different station signals to less than one bit by compensating the integer bit timedelay twice,which avoided phase wrapping and omitted fraction compensation.Then,analysis on the new scheme was made,including correlation length and computational complexity.In addition,an outlier delete algorithm was mended,which made the delete procedure unaffected by the trend phase change according to the frequency.Monte Caro simulation and CE-2 satellite measured data processing results prove the validity and effectiveness of the improvements. Related Articles | Metrics

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Optimizing Method for Fin-tube Fluid-loop Radiator FENG Mao-Long, FAN Han-Lin, HUANG Jia-Rong, ZHONG Qi 2012, 32 (6):  62-67.  doi: 10.3780/j.issn.1000-758X.2012.06.009 Abstract ( 1696 )   PDF (428KB) ( 1246 )   Save The heat transfer process of SZ-spaceship′s radiator was analyzed and optimized for the finwidth of fintube single phase flood-loop radiator,the popular evaluation method of space radiatorsheat rejectionweight（HR/W）ratio equation.Through analytic and numerical method,HR/W ratio equation was introduced and solved and the best fin-width expression for max and microheat rejectionweight ratio were obtained.In the end,The parameters of SZ-spaceship radiator vsthe optimized radiator was compared.It shows that the proposed method provides useful references for radiator optimization design. Related Articles | Metrics

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Multi-frequencySame-beamInterferometryonGeneralTT&CSignal CHEN Lue, TANG Ge-Shi, CHEN Ming, HAN Song-Tao, LIU Hui-Cui, WANG Mei 2012, 32 (6):  68-74.  doi: 10.3780/j.issn.1000-758X.2012.06.010 Abstract ( 1560 )   PDF (470KB) ( 965 )   Save Themethodofmultifrequencysamebeaminterferometryutilizinggeneraltracking,telemetryandcontrol(TT&C)signalwasproposedtoimplementtwospacecraftrelativepositioning.Themathematicalcalculationofthedifferencephasedelaywasanalyzed,amodelmodificationmethodofdifferentialdelaymeasurementerrorwasproposed,andtheobservingconditioninlunarorbitofsamebeaminterferometryutilizinggroundmeasurementstationswasanalyzed.Utilizingthemulti-frequencyinformationofthegeneralTT&Csignalofthetwospacecraft,thesimulationresultsshowthatpicosecondleveldifferentialdelaymeasurementvalueisobtainedviadelayerrormodelmodification.Thisprovidesreliablemeasurementinformationforrelativepositionbetweentwospacecraftindeepspacemissions. Related Articles | Metrics

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A Carrier Frequency Synchronization Method in Satellite Communications System Lü Qiang , QI Wei-Kong, XUE Yong 2012, 32 (6):  75-80.  doi: 10.3780/j.issn.1000-758X.2012.06.011 Abstract ( 1752 )   PDF (368KB) ( 1523 )   Save Aiming at the low precision of the traditional carrier frequency synchronization method,a new frequency estimation method was proposed,using the traditional method to get primary frequency estimation before demodulation and using the decoding information to estimate and compensate the rudimental frequency.Simulation results show the proposed method can effectively control the fluctuation of the rudimental frequency which was brought by the traditional method，decrease the influence on system performance,get better decoding performance,reduce the demodulation threshold and lead to more efficient use of system power while not occupy more frequency band. Related Articles | Metrics