ZED-F9K-Integration manual
•
Wheel tick sensor initialization: Solution enters fusion mode (fusionMode field in the UBX-
ESF-STATUS message is on 1:FUSION), even when wheel tick is not yet initialized, following a
UDR mode approach described in UDR fallback mode section. WT sensor parameters, such as
initial wheel tick factor, are estimated in parallel and are used once estimated with sufficient
accuracy. As long as the wheel tick parameters are not initialized, the status of the wheel
tick initialization (wtInitStatus) is flagged as 1:INITIALIZING in the UBX-ESF-STATUS
message. Once initialized, the wheel tick sensor initialization is flagged as 2:INITIALIZED,
WT data are used by the filter and the parameters are stored in non-volatile storage. If no wheel
tick data are required, the wheel tick initialization is flagged as 0:OFF.
• Sensor error (e.g. missing data) detected: Sensor timeout of more than 500 ms will trigger an
INS re-initialization.
Note that initialization phase requires good GNSS signal conditions as well as periods during which
vehicle is stationary and moving (including left and right turns). Once all required initialization steps
are achieved, fusion mode is triggered and continuous calibration begins.
3.2.6.1.2 Fusion mode
Once initialization phase is achieved, the receiver enters fusion mode. The receiver is in fusion
mode if the UBX-ESF-STATUS.fusionMode field is set to 1:FUSION. The fusion filter then
starts to compute combined GNSS/dead reckoning fixes (fused solutions) and to calibrate the
sensors required for computing the fused navigation solution. This is the case when the sensor
calibration status (UBX-ESF-STATUS.calibStatus) is set to 1:CALIBRATING. As soon as the
calibration reaches a status where optimal fusion performance can be expected, (UBX-ESF-
STATUS.calibStatus is set to 2/3:CALIBRATED.
3.2.6.1.2.1 UDR fallback mode
In case of WT sensor error / timeout (500 ms), or normal WT sensor initialization, the solution
falls back to UDR (untethered dead reckoning) mode. The UBX-ESF-STATUS.fusionMode field still
shows 1:FUSION when the receiver enters UDR fallback mode. However, the following flags can be
used to determine when the receiver has entered UDR mode:
•
The UBX-ESF-STATUS.wtInitStatus shows 1:INITIALIZING.
•
The WT fault flag, UBX-ESF-STATUS.missingMeas field, is set to 1, indicating a WT timeout
has been detected.
3.2.6.1.3 Suspended fusion mode
Sensor fusion is temporarily suspended in cases where no fused solution should/can be computed.
In this case, the receiver produces a GNSS-only solution. The receiver is considered to be
in temporarily-disabled fusion mode when the UBX-ESF-STATUS.fusionMode field is set to
2:SUSPENDED.
Fusion is suspended in the following scenarios:
• If one or several sensors deliver erroneous data or no data at all. Fusion is suspended during the
sensor failure period. The receiver automatically recovers once the affected sensor or sensors
are back to normal operation.
• If the vehicle is detected to be on a ferry or other moving platform, where odometer data does
not indicate any displacement.
3.2.6.1.4 Disabled fusion mode
Sensor fusion can be permanently disabled if recurrent fusion failures occur. The receiver is
considered to be in permanently disabled fusion mode if the UBX-ESF-STATUS.fusionMode field
is set to 3:DISABLED. In this case, the receiver produces a GNSS-only solution if possible.
Fusion is permanently disabled in the following cases:
UBX-20046189 - R01
3 Receiver functionality Page 24 of 105
C1-Public Early production information
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