DMU380SA Series
User’s Manual
________________________________________________________________________
Doc# 7430-0026 Rev. 01
Page 40
Use GPS
ON
The Use GPS setting allows users to turn on and off the GPS feedback. The default
setting is ON for the INS380SA. When Use GPS is turned OFF, the INS380SA
’s behavior
will revert to that of an AHRS380SA. See the AHRS380SA Theory of Operation for
detailed description.
Stationary Yaw
Lock
OFF
This setting defaults to OFF on the INS380SA, and it is recommended to be OFF for the
INS380SA. The stationary yaw lock setting is only recommended for consideration when
the INS380SA is operating with GPS (Use GPS = ON) and WITHOUT magnetometer
feedback (Use Mags = OFF). Stationary yaw lock may be appropriate if the user platform
is a wheeled land vehicle.
Use Mags
ON
The Use Mags setting allows users to turn on and off the magnetometer feedback for
yaw/heading stabilization. The default setting is ON for the INS380SA. When Use Mags
is turned ON, the INS380SA uses the magnetic field sensor readings to stabilize the drift
in yaw, and it slaves the yaw to the compass reading provided from the magnetic field
sensor readings. When UseMags is turned OFF, the heading (yaw) angle measurement
of the INS380SA will be slaved to the GPS heading if GPS is available, otherwise the
heading will drift feely. The reason for this setting is to give the user an ability to turn off
the magnetometer stabilization when severe magnetic distortion may be occurring. This
setting is desirable when the user vehicle temporarily moves in close proximity to a large
ferrous object. When the Use Mags switch is turned from OFF to ON, the INS380SA will
reinitialize the yaw/heading angle with the compass reading provided from the magnetic
field sensor readings.
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 for
the INS380SA. Algorithm reset returns the INS380SA to a high gain state, where the
INS380SA rapidly estimates the gyro 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 can not 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 inertial rate sensor over-range is
controlled using the restartOnOverRange switch. 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-passed rate sensor
fall below 3 deg/sec to begin initialization. The system will then attempt a normal
algorithm start.
Dynamic
Motion
ON
The default setting is ON for the INS380SA. 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, this switch can be turned
off to allow the attitude estimate to quickly stabilize.
Turn Switch
threshold
0.5
deg/sec
With respect to centripetal or false gravity forces from turning dynamics (or coordinated
turn), the INS380SA 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.
BIT
See 4.5.3
4.5.3
INS380SA Built-In Test
As with the IMU, VG and AHRS380SA, the Built-In Test capability allows users of the
INS380SA to monitor health, diagnostic, and system status information of the unit in
real-time. The Built-In Test information consists of a BIT word (2 bytes) transmitted in
every measurement packet.
In addition, there is a diagnostic packet ‘T0’ that can be
requested via the Get Packet ‘GP’ command which contains a complete set of status for
