Owner's manual

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7430‐0131‐01Rev.F
Page27
NAV440UserManual
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Setting DefaultValue Comments
RestartOn
OverRange
OFF
Thissettingforcesanalgorithmresetwhenasensoroverrangeoccursi.e.,a
rotationalrateonanyofthethreeaxesexceedsthemaximumrange.Thedefault
settingisOFF.Algorithmresetreturnstheunittoahighgainstate,wherethe
unitrapidlyestimatesthegyroscopebiasandusestheaccelerometerfeedback
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heavily.Thissettingisrecommendedwhenthesourceofover‐rangeislikelyto
besustainedandpotentiallymuchgreaterthantheratesensoroperatinglimit.
Largeandsustainedangularrateover‐rangesresultinunrecoverableerrorsin
rollandpitchoutputs.AnunrecoverableerrorisonewheretheEKFcannot
stabilizetheresultingrollandpitchreading.Iftheover‐rangesareexpectedto
beofshortduration(<1sec)andamodestpercentageoverthemaximum
settingbe
operatingrange,itisrecommendedthattherestartonoverrange
turnedoff.
Han nganinertialrates
dli ensorover‐rangeiscontrolledwiththe
rtOnOverRange
resta switch.
• tOnOverRange 
If
restar isoff,thesystemwillflagtheoverRangestatusflagand
continuetooperatethroughit.
• If
restartOnOverRangeison,thesystemwillflagamasterFailerrorduringan
over‐rangeconditionandcontinuetooperatewiththisflaguntilaquasi‐
staticconditionismettoallowforanalgorithmrestart.
Thequasi‐staticconditionrequiredisthattheabsolutevalueofeachlow‐pass
ratesensorfallsbelow3deg/sectobegininitialization.Thesystemwillthen
attemptanormalalgorithmstart.
Dynamic
Motion
ON
ThedefaultsettingisON.Turningoffthedynamicmotionsettingresultsina
highergainstatethatusestheaccelerometerfeedbackheavily.Duringperiodsof
doff
timewhenthereisknownlowdynamicacceleration,thisswitchcanbeturne
toallowtheattitudeestimatetoquicklystabilize.
TurnSwitch
threshold
10.0deg/sec
Withrespecttocentripetalorfalsegravityforcesfromturningdynamics(or
coordinatedturn),theunitmonitorstheyaw‐rate.Iftheyawrateexceedsagiven
turnSwitchthreshold,thefeedbackgainsfromtheaccelerometersignalsfor
attitudecorrectionarereducedbecausetheyarelikelycorrupted.
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AHRS440Function
TheAHRS440(AttitudeHeadingReferenceSystem)unitincludesanadditionalinternal3‐axismagnetometerand
associatedsoftwarerunningontheDSPprocessor.Thisenablesthecomputationofdynamicheading,aswellas
dynamicrollandpitch.AHRS440dataprovidesdynamicheading,roll,andpitchmeasurements,inadditiontothe
VG440andIMU440data.Thedynamicheadingmeasurementisstabilizedusingthe3‐axismagnetometerasa
magneticnorthreference.Thedynamicrollandpitchmeasurementsarestabilizedusingtheaccelerometersasa
fined
long‐termgravityreference.Theunitcanbeconfiguredtoturnonandoffthemagneticreferenceforuserde
periodsoftime.
Thisfunctionutilizesdatafromcalibratedsensors,thegyroscopes,theaccelerometersandamagnetometer
(internalorexternal).FordetailsoftheIMUfunctions,referto
IMU440Functiononpage23.FordetailsoftheVG
functions,referto
VG440(VerticalGyroscope)Function),onpage25.Inadditiontothosefeatures,theAHRS440
algorithmhastwomajorphasesofoperation.