Instruction Manual

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Page28
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GNAV540UserManual
7430‐0808‐01Rev.B
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Setting DefaultValue Comments
Freely
Integrate
OFF
TheFreelyIntegratesettingallowsconfiguringtheunitintoafreegyroscope.In
freegyroscopemode,theroll,pitchandyawarecomputedexclusivelyfrom
angularratewithnoKalmanfilterbasedcorrectionsofroll,pitch,oryaw.When
turnedon,thereisnocouplingofaccelerationbasedsignalsintotherolland
ywith
pitch.Asaresult,theroll,pitch,andyawoutputswilldriftroughlylinearl
timeduetosensorbias.
Forbestperformance,theFreelyIntegratemodeshouldbeusedafterthe
algorithmhasinitialized.ThisallowstheKalmanFiltertoestimatetherolland
pitch e
ratesensorbiaspriortoenteringthefreegyroscopemode.Exitingthefre
scopemode(OFF),causesoneofthefollowingbehaviorstooccur:
•
gyro
Iftheunithasbeeninfreelyintegratemodeforlessthansixtyseconds,the
algorithmwillresumeoperationatnormalgainsettings.
Iftheunithasbeeninfreelyintegratemodeforgreaterthansixtyseconds,
thealgorithmwillforcearesetandreinitializewithhighgainsautomatically.
•

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

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indicatestheEKFcannotstabilize
theresultingrollandpitchreading.Iftheover‐rangesareexpectedtobeof
moperating
turnedoff.
shortduration(<1sec)andamodestpercentageoverthemaximu
range,itisrecommendedthattherestartonoverrangesettingbe
Han ganinertialratese
dlin nsorover‐rangeiscontrolledwiththe
rtOnOverRange
resta switch.
•
If
restartOnOverRangeisoff,thesystemwillflagtheoverRangestatusflag
andcontinuetooperatethroughit.
• If
restartOnOverRangeison,thesystemwillflagamasterFail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
ill
filteredratesensorfallsbelow3deg/sectobegininitialization.Thesystemw
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
turnswitchthreshold,thefeedbackgainsfromtheaccelerometersignalsfor
attitudecorrectionarereducedbecausetheyarelikelycorrupted.