Moog Crossbow NAV440 Series User Manual

Page 29

NAV440 User Manual

7430‐0131‐01 Rev. F

Page 29

Setting

Default Value

Comments

Freely
Integrate

OFF

The Freely Integrate setting allows a user to turn the unit into a free gyroscope. In
free gyroscope 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

tch, and

or magnetometer based signals to the yaw. Due to sensor bias., the roll, pi

yaw outputs will drift roughly linearly with time.
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 rat

the free

e sensor bias prior to entering the free gyroscope mode. Upon exiting

gyroscope mode (OFF), one of two behaviors will occur:

•

nds,

If the unit has been in freely integrate mode for less than sixty seco
the algorithm will resume operation at normal gain settings

• If the unit 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

The

for y

Use Mags setting allows users to turn on and off the magnetometer feedback

aw/heading stabilization.

• The default setting is ON. When Use Mags is turned ON, the 440 Series unit

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

unit will drift and freely integrate. In effect, this setting converts the

be done on

functionality to VG. However, unlike a unit in the VG440, this can
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 moves in close
proximity to a large ferrous object. When the Use Mags switch is turned from

FF to ON, the unit will reinitialize the yaw/heading angle with the compass

eading provided from the magnetic field sensor readings.