z00 3rdInternational Corerence on Advanced Computer Theor and Engineering (ICA CTE) Air-launchedRocketAttitudeControlof SeparationStageBasedonRCS XUZhi College of Astronautics Northwester Polytecnical University Xi' a, China e-mail:xuzhi@nwpu.edu.cn b5lr0Cln this paper,attitudecontrolproblemofcarbinairlaunchingduingseparationstagesbetweenplaneandvehicle byreactioncontrolsystem(ReS)wasstudied.Firstanalyzed movementunderdifferentseparationconditionsbetween launchrocketandplane,thendeterminedlaunchvehicle fightstatuswhenReSfredanddesignedrocketpitching program.Onthisbasis,giventhestandardtrajectory programsandReSconfguration.Usingpulsewidthandpulse frequencymodulationmethod,ReSthrusterswitchcontroller isdesigned.Thesimulationresultsshowthecorrectnessof ReSthrusterconfguration. Agw0r05-C0m0ncnl; 0r-l0unChc0; rc0Cl0n C0nlr0l 5J5lcm;C0nlr0l5J5lcm1.INTRODUCTION Thecabinai-launchedrocketisthatthelaunchVehicle insidethecabinofcaryingplaneandplanethrowlaunch vehicleithespecifedlocation,bythecontrolsystemto adjustitspostureandposition,whentolaunchrequest,the engineignitionandthepayloadwasputintoorbit.The advantageofthemethodishigherreliability,butsmall launch vehicle payload.The launch vehiclefying within the atmosphereforcabinair-launchedmethodisdifferentfom ground-launchedfighttrajectory:ontheonehand,the separatingbetweenlauchvehicleandplanefacecomplex process,requiringtheuseofassistiveattitudestabilization and control means, to obtain a suitable engine ignition timing; theotherhand,alaunchvehiclefightattitudeadjustment andthepresenceoflargeangleofattackfightproblems, whichtheattitudecontrolsystemcontrolabilityofthenew requirements.Inresponseto thesetwo issues,using reaction jet control system (RCS) for attitude stabilization and control to track the standard trajectory,and under the control request oftheinitialfighttrajectory,giventheRCStuster confguration,thelaunchvehicleattitudecontrollerof treechannelaredesignedbyusingpulsewidthandpulse fequency(PWPF)modulation,andfnishsixdegreesof feedom trajectory simulation. II.PROGRAM OF FLIGHT PROCEDURES WhenusingtheRCSattitudestabilizationmethod,the initiallaunchvehiclefighttrajectoryshowninFigure1. Whentherocketfllslidesoutofplaneandreachtheright position,RCS attitude control system begin to control launch vehicle attitude.Launch vehicle roll attitude and yaw attitude TANGShuo College of Astronautics Northwester Polytecnical University Xi'an, China e-mail:suotang@nwpu.edu.cn requiredtomaintainthezeroposition,thepitchattitudeis expectedalongtheplanedchangesinfightprocedures. Beforethelaunchvehicleengineignition,launchvehicle pitchattituderequiredatabout900Herethemainpitchin font of the engine ignition design of fight procedures,fight proceduresaferengineignitionstillusetheprogramsgiven earlier. Figure 1.the initial launch vehicle mission Rocketengineignitionbeforethefightprocedurescan bedividedintotwosections,onesectionofattitude adjustment,thesecondparagraphistomaintainattitude. AttitudeAdjustmentsectionofpitchangleofRCSfreto reach900;thenlaunchvehiclepitchangletomaintain900, untiltheengineignition.Herethedesignoftheattitude adjustmentproceduresweresinusoidalpitchparagraph,as follows qc =90sin ( Ot +) Pitch angular velocity ic =90Ocos ( Ot +) (1) (2) AngularfequencyO andphase bytheinitialconditions and terinal conditions, and the following {qco =90sin ( Oto +) (3) 90 =90 sin ( Otl+) to isRCSfretime,qco isexpectedlaunchvehiclepitch anglewhenRCSfre,tlfortherockettoreach900pitch angle of the moment.Pitch attitude to maintain procedures qc =90' (4) Initial trajectoryofthefightplanasshowninFigure2. Thefgure,l_ is the time for the rocketengineignition,l_ is starttimeforthelaunchvehicleprogramtum,l 4isfight time for the end of launch vehicle. V-1-4Z44-J4Z-Z/$Z.00" Z010III N3-1Vz010 3rdInternational Conference on Advanced Computer Theor and Engineering (ICACTE) / Figure 2.the initial trajectory fight procedures TABLE I.1IVEOllLICH1lkOCEDUkES!ODEfight proced uresValue t1 -to3.2s tz -to3.5s t3 -tolOs t4 -to73.5s III.CONTROL SYSTEM DESIGN . RCSthruster confguration Accordingtothefightcontroltasks,determinetheRCS thrusterconfguration,numberandthrustshowninTable1, thelaunchvehicletrusteronthelayoutshowninFigure3. Forthepitchchannel,whenonlyonethrusterwork,then start on the 2nd thruster; when the need to work two thrusters thenstatthe1,3 thruster.Yawandpitchchannelsusigthe' samecontrolchannelallocationlogic.Rollattitudecontrol channelisalwaysused4setsofrollthrustertrustinthe opposite direction the two of them to get the roll axis relative to the launch vehicle control moment. TABLE II.RCS 1HkUS1EkI!1ECkA1IO!lLA!HLSconfgurationSingle Engine Thrust (N)Number Pitch60006 Yaw60006 Roll3004 Figure 3.RCS thruster confguration and layout D. RCS Controller Aerodynamiccontrolsurfacesorenginewiththrust vectorattitudecontrolsystem,thecontroliscontinuous whentheoutputisnotsaturated.ReactionControlSystem usuallyprovidestheamountofnon-continuousswitching control.Switchingcontrolfortheamountofcontrollaw designavarietyofways,eitherdiectlyusingnonlinear switchingcontrollawdesignmethodcanalsobea continuouscontrollawisfrstdesigned,thenamethodto generatetheequivalentofswitchcontrolcommands.RCS controller designed with this latter approach,thatfrst design acontinuouscontroller,andthenusepulsewidthandpulse fequency(PWPF)modulatortogenerateanequivalent amount of continuous thrust control switch commad. PWPFmodulatorblockdiagramshowninFigure4,the formercontainsaninertiallinktothechannelandaband widthofdeadzoneandhysteresisrelaylinkrelaylink,also known as the Schmitt trigger. Inertiallinkparametersincludetheamplifcationfactor _ ,thetimeconstantJ_ ,Schmitttriggerparameters includigpulseoutputamplitude_, switchingthreshold C__ andU 1'(/)+ e(/) Y(/) Figure 4.PWPF modulator Thisprogramusesmulti-RCSthrustercombination,and thereforeneedtoconsiderthecontrolofdistribution.Here multi-level Schmitt trigger to achieve more than allocation of thrustercontrollogic,showninFigure5forthethree Schmitttrigger,itcanbeachievedbythethreethruster control allocation logic. Figure 5.three Schmitt Trigger WiththeclassicalPIDcontrollaw,RCSattitudecontrol system block diagram of the program shown in Figure 6. attit.i._'ecoad attitudeccd'+ +- a; SFigure 6.RCS attitude control scheme block diagram IV.SIX DEGREES OF FREEDOM TRAJECTORY SIMULATION InitialtrajectorysimulationfomtheRCSignition,until theendoflaunchvehiclefrststagefight.Theroleofthe wind is considered, The initial conditions shown in Table 3. N3-Zz010 3rdInternational Conference on Advanced Computer Theor and Engineering (ICACTE) TABLE III. 1kAJEC1OkYI!I1IALCO!DI1IO!SInitial ConditionValue Altitude9992.6m Velocity143.7m/s Pitch Angle30. 30 Yaw Angle3.00 Roll Angle3.00 Trajectory angle_3.90 Pitch rate29.10 Is Yaw rate2.00 Is Roll rate1.00 Is Figure 7 to Figure 12 shows the simulation results I0c]

-trackD" % 0 =" -l:C 90B00,05040J003 0j0 J0 4050!ime(s)- - cemmanub 70Figure 7.launch vehicle pitch angle curve }0

00j0000,00} !imes)Figure 8.launch vehicle attitude angle tracking error N3-Z1" = " = 8 oc0 ' U c --]C " = " 8 e oc0 ' u J

1 ]JJ _ _

Time(s)Figure 9. RC5 thruster pitch channel switch curve ]J1J Jc- J -1-1J-]

o1 ] J J 1ime(s)Figure 10.RC5 thrusteryaw channel switch curve 1J1J ]_____-_____ o1 ] J J !ime(s)Figure II.RC5 thruster roll channel switch curve z0103rdInternational Corerence on Advanced Computer Theor and Engineering (ICACTE) x1o -1 @ J] J 1 JJ J1 z,r,x10 Figure 12.Rocket three-dimensional relative motiontrajectory Figure 7 launch vehicle pitch angle tacking cuve can be seenfomthelaunchvehiclepitchangleisconsistentwith thefightprogra.Figure forthetree-channellaunch vehicleattitudetrackingeror,thefgurecurvesshowthat the elimination of the initial attitude eror,the launch vehicle attitudetrackingerorislessthan10.Theresultsshowthe Resattitudecontrolsystemeffectivenessoftheprogram. Figure9,Figure10 andFigure11respectively,pitch,yaw, roll three-channel ReSthruster switching curve.Adjustment processintheinitialposture,pitch,yawchannelofthree thrustersatthesametimethereworkingconditions;ina fight,theelevationchanneluptousetwothrusters,yaw channelisonlyusedathruster.Theseresultsshowthatthe rocketenginebeforeignitionoftheResthrustersfor attitude control is the most demanding requirements. ACKNOWLEDGMENT Inthispaper,applicationofRestoachieveseparation stage launch vehicle rocket aircraf attitude control,designed thethree-channelReSthrusterconfguration,usingpulse widthmodulated pulsefequency(PWPF)modulationthreechanneldesignofthelaunchvehicleattitudecontrol,and throughsixfeedegreetrajectorsimulationverifedthe effectivenessof design. REFERENCES [I)Saigul-KlijnN, NoelC, Sarigul-KlijnM.AirLaunchingEath-toOrbitVehicles:DeltaVgainsfomLaunchConditionsandVehicle Aerodynamics.AlAA 2004-872. (2)Saigul-Klijn M, Sarigul-KlijnN, HudsonG, eta!.TradeStudiesfor Air Launching aSmall Launch Vehicle from aCargo Aircraf.AIAA 2005-621. (3)HudsonGC.QuickReachResponsiveLaunchSystem.AlAA-RS4 2006-2003. [4)WieH, PlesicaCT.AttitudeStabilizationofFlexibleSpacecraf During Stationkeeping Maneuvers.J.Guidance.1984,7(4). (5)KrovelTD.OptimalTuningofPWPFModulatorforAttitude Contro!.NorwegianUniversityof Scienceand Technology, 2005. (6)AgrawalH A,McclellandRS,SongGH. AttitudeControlof FlexibleSpacecrafUsingPulse-WidthPulse-FrequencyModulated Thrusters.Space Techno!.1997, 17(1). NJ-ZZ