ZED-F9R-Integration manual
At higher navigation rates, it is strongly recommended to check (and maybe reduce)
the number of enabled output messages. CPU load, memory and interface bandwidth
constraints may be a limiting factor.
3.2.7 Operation
This section describes how the HPS receiver operates.
3.2.7.1 Fusion filter modes
The fusion filter operates in different modes which are output in the UBX-ESF-STATUS message.
The table below summarizes the different fusion filter modes with the receiver's associated tasks.
Mode Performed tasks / Possible causes Published fix type
Initialization
Initialization of IMU
Initialization of IMU-mount alignment
Initialization of INS (position, velocity, attitude)
IMU sensor error (e.g. missing data) detected
3D-fix (GNSS)
Fusion
Fine-calibration of IMU-mount misalignment angles
Fine-calibration of IMU sensors
Fine-calibration of wheel tick factors
Degraded HPS mode when missing WT data detected
GNSS/DR fix
Suspended fusion
Sensor error (e.g. missing data) detected
Ferry detected
3D-fix (GNSS)
Disabled fusion
Fatal fusion filter error occurred
Fusion filter turned off by user
3D-fix (GNSS)
Table 11: Fusion modes
More details about each fusion mode are given in the following sections.
3.2.7.1.1 Initialization mode
The purpose of the initialization phase is to estimate all unknown parameters which are required
for achieving fusion. The initialization phase is triggered after a receiver cold start or a filter reset
in case of fusion failure. The receiver is in initialization mode if the fusionMode field in the UBX-
ESF-STATUS message is 0:INITIALIZING. In this case the required sensor calibration status
(calibStatus) is flagged as 0: NOT CALIBRATED and the navigation solution output during
initialization is based on GNSS solely.
The initialization phase comprises the following internal steps whose status is published in the
initStatus field of the UBX-ESF-STATUS message:
• IMU initialization: Unknown crucial IMU parameters such as sensor sampling frequency are
estimated during initialization. As long as all required IMU parameters are not initialized, the
status of the IMU initialization (imuInitStatus) is flagged as 1:INITIALIZING in the UBX-
ESF-STATUS message. Moreover, the required sensor calibration statuses (calibStatus)
are flagged as 0:NOT CALIBRATED in the UBX-ESF-STATUS message. Note that if the user
configured all required sensor settings, this step is skipped and IMU initialization is flagged as
2:INITIALIZED.
• IMU-mount alignment initialization: If automatic IMU-mount alignment is enabled (see the
Automatic IMU-mount alignment section), initial IMU-mount roll, pitch and yaw angles need to
be estimated. For that, good GNSS signal reception as well as sufficient vehicle dynamics (i.e.
a series of left and right turns during a normal drive) need to be at hand. As long as the IMU-
mount alignment is not initialized, the status of the IMU-mount alignment (mntAlgStatus)
UBX-20039643 - R06
3 Receiver functionality Page 30 of 119
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