DMU380ZA Series
User’s Manual
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Doc# 7430-3810 Rev.02
Page 21
The AHRS380ZA and INS380ZA
units must be mounted at least 24” away from large
ferrous objects and fluctuating magnetic fields. Failure to locate the unit in a clean
magnetic environment will affect the attitude solution.
3.4.2
AHRS380ZA Advanced Settings
In addition to the configurable baud rate, packet rate, axis orientation, and sensor low-
pass filter settings, the AHRS380ZA provides additional advanced settings which are
selectable for tailoring the AHRS380ZA to a specific application requirements. The
AHRS380ZA advanced settings are shown in Table 10:
Table 10 AHRS380ZA Series Advanced Settings
Setting
Default
Comments
Baud Rate
38,400
baud
9600, 19200, 57600 also available
Packet
Type
A1
S0, S1, A2, N0, N1 also available
Packet
Rate
25 Hz
This setting sets the rate at which selected Packet Type, packets are output. If polled
mode is desired, then select Quiet. If Quiet is selected, the VG380ZA will only send
measurement packets in response to GP commands.
Orientation
To configure the axis orientation, select the desired measurement for each axes: NAV-
VIEW will show the corresponding image of the AHRS380ZA, so it easy to visualize the
mode of operation. See section 8.4 Orientation Field settings for the twenty four possible
orientation settings. The default setting points the connector AFT.
Filter
Settings
20 Hz
accels
20 Hz
rates
The low pass filters are set to a default of 20Hz for the accelerometers, and 20Hz for the
angular rate sensors. There is one filter setting for all three angular rate sensors. There
is one filter setting for all three accelerometer sensors. The reason for filtering the
accelerometers is that in many installations, the vibration level can be high, and it can
prove helpful to filter accelerometers.
Freely
Integrate
OFF
The Freely Integrate setting allows a user to turn the AHRS380ZA
into a ‘free gyro’.
In
free gyro mode, the roll, pitch and yaw are computed exclusively from angular rate with
no kalman filter based corrections of roll, pitch, or yaw. When turned on, there is no
coupling of acceleration based signals into the roll and pitch or magnetometer based
signals to the yaw. As a result, the roll, pitch, and yaw outputs will drift roughly linearly
with time due to sensor bias. For best performance, the Freely Integrate mode should be
used after the algorithm has initialized. This allows the Kalman Filter to estimate the roll
and pitch rate sensor bias prior to entering the free gyro mode.
Upon exiting the ‘free
gyro’ mode
(OFF), one of two behaviors will occur
(1) If the AHRS380ZA has been in freely integrate mode for less than sixty
seconds, the algorithm will resume operation at normal gain settings
(2) If the AHRS380ZA has been in freely integrate mode for greater than sixty
seconds, the algorithm will force a reset and reinitialize with high gains
automatically.
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 AHRS380ZA. When
Use Mags is turned ON, the AHRS380ZA 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 Use Mags is turned OFF, the
heading (yaw) angle measurement of the AHRS380ZA will drift and freely integrate.
In effect, this setting converts an AHRS380ZA into the functionality of the
VG380ZA. However, unlike a VG380ZA this can be done on a selectable basis and
changed in real time during a mission. 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 system temporarily
