Owner's manual

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Page28
NAV440UserManual
7430‐0131‐01Rev.F
Thefirstphaseofoperationisthehigh‐gaininitializationphase.Duringtheinitializationphase,theunitisexpected
tobestationaryorquasi‐staticsotheEKFweightstheaccelerometergravityreferenceandEarth’smagneticfield
referenceheavilyinordertorapidlyestimatetheX,Y,andZratesensorbias,andtheinitialattitudeandheadingof
theunit.Theinitializationphaselastsapproximately60seconds,andtheinitializationphasecanbemonitoredin
thesoftwareStatusBITtransmittedbydefaultineachmeasurementpacket.Aftertheinitializationphase,theunit
operateswithlowerlevelsoffeedback(alsoreferredtoasEKFgain)fromtheaccelerometersandmagnetometersto
continuouslyestimateandcorrectforroll,pitch,andheading(yaw)errors,aswellastoestimateX,Y,andZrate
sensorbias.
TheAHRS440providesthesamescaledsensorandanglemodepacketsoftheVG440.TheAHRS440defaultstothe
A1AnglePacketwhichoutputstherollangle,pitchangle,yawangle,anddigitalIMU440data.IntheAHRS440,the
A0andA1packetscontainaccuratemagnetometerreadings.RefertoChapter9.Communicatingwiththe440and
Chapter10.ProgrammingGuidelinesforfullpacketdescriptions.
NOTE:Forproperoperation,theunitreliesonmagneticfieldreadingsfromitsinternal3‐axismagnetometer.The
unitmustbeinstalledcorrectlyandcalibratedforhard‐ironandsoftironeffectstoavoidanysystem
perf
ormancedegradation.Referto
Chapter4.MagnetometerCalibrationandAlignmentGuidelinesfor
informationaboutmagneticcalibration;reviewthatinformationbeforeusingtheAHRS440.
NOTE:Theunitmustbemountedatleast24”awayfromlargeferrousobjectsandfluctuatingmagneticfields.
Failuretolocatetheunitinacleanmagneticenvironmentwillaffecttheattitudesolution.
AHRS440AdvancedSettings
Inadditiontotheconfigurablebaudrate,packetrate,axisorientation,andsensorlow‐passfiltersettings,theunit
providesadditionaladvancedsettingswhichareselectablefortailoringtheunittospecificapplication
requirements.TheAHRS440advancedsettingsarelistedin below:
Table7
Table7AHRS440SeriesAdvancedSettings
Setting DefaultValue Comments
BaudRate 38400 9600,19200,57600alsoavailable
PacketType A1 S0,S1,S2,A0,A2,N0,N1alsoavailable
PacketRate 25Hz
ThissettingsetstherateatwhichselectedPacketType,packetsareoutput.If
polledmodeisdesired,thenselectQuiet.
Orientation
See
Figure4on
page
22.
Toconfiguretheaxisorientation,selectthedesiredmeasurementforeachaxis:
NAV‐VIEW2.2willshowthecorrespondingimageoftheunit,soiteasyto
visualizethemodeofoperation.Referto
OrientationFieldonpage84forthe
twentyfourpossibleorientationsettings.Thedefaultsettingpointsthe
connectorAFT.