User manual

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 DocumentMT0100P.N
©XsensTechnologiesB.V. MTiandMTxUserManualandTechnicalDocumentation
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3.2.4 XKFScenarios
As described above, XKF‐3 uses assumptions about the acceleration and the magnetic field to obtain
orientation.Becausethecharacteristicsoftheaccelerationormagneticfielddifferfordifferentapplications,
XKF‐3makesuseofscenariostobeabletousethecorrectassumptionsgiventheapplication.Thisway,XKF‐3
canbeoptimizedfordifferenttypesofmovement.Foroptimalperformance,thecorrectscenariomustbeset
by the user. For information on how to specify a scenario in XKF‐3, please refer to the MT Manager User
manualortheMTlow‐levelcommunicationprotocoldocumentation.
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The different scenarios are divided in 'human', 'machine' and 'marine' types of motion and are discussed
below.
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XKF‐3 Scenario IMU Magnetometer
Human
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Human_large_accel
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Machine
● ●
Machine_nomag
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Marine
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Table1:TheXKF‐3orientationalgorithmusesdifferentsourcesofinformationorassumptionsdependingon
theapplicationscenariothatisselected.
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Human
Two different scenarios are designed for human movements. The scenario 'human' assumes the somewhat
slower movements, also taking into account magnetic disturbances typical for an indoor environment. The
scenario'human_large_accel'isoptimizedforthefastmovementsuptoanangularvelocityof1200deg/sand
accelerationsupto5gthatmayoccurduringimpact.

Machine
Themachinescenarioisdesignedforaverybroad rangeofdifferentmovements.Theseincludeaccelerations
thataregenerallyslowerandoflongerperiodsoftimethanaccelerationstypicalforhumanmovement.
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Aseparatemachinescenarioisdesignedforsituationsinwhichthelocalearthmagneticfieldistoodistorted
tobeuseful.Thisscenarioislabelled‘machine_nomagfield’,itdoesnotmakeuseofthelocalearthmagnetic
field to obtain a heading estimate. This can be advantageous in scenarios in which extreme magnetic
disturbancesoccur,butithasthedisadvantagethattheheadingcannotbestabilizedandthatthegyrobiasof
the “vertical” gyroscope can not be observed. In other words: a heading change (delta) can be accurately
tracked,butforlongerperiodsoftimetheabsoluteheadingcannotbestabilized.Notethattherollandpitch
(the inclination, or attitude) are still accurately tracked using rate gyroscopes and accelerometers alone.
Considerutilizingthe“NoRotation”featuretoimprovegyrobiasobservabilityanddecreaseheadingdriftwhen
usingthisscenario,seealsosection3.3.
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Marine
The marine scenario is optimized for low, long term accelerations and mild magnetic disturbances. It is
assumedthatinatypicalmarinesetting,almostallmagneticdisturbancescanbeaccountedforbyaso‐called
magneticfieldmappingprocedure.Seesection7.2.3formoredetails.