Moog Crossbow GNAV540 User Manual
Page 34
Page 34
GNAV540 User Manual
7430‐0808‐01 Rev. B
Setting
Default Value
Comments
Restart On
Over Range
ON
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 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 operating range, it is
recommended that the restart on over range setting be turned off. Handling of
an in
nge
swit
ertial rate sensor over‐range is controlled using the restartOnOverRa
ch.
If this switch is off, the system will flag the overRange status flag and
continue to operate through it.
If this switch 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
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
time when there is known low dynamic acceleration
Turn Switch
Threshold
0.5 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.