Chapter 3 SPAN Operation
OEM7 SPAN Installation and Operation User Manual v14
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Log
Description
VARIABLELEVERARM
This log displays the calculated variable lever arm.
The VARIABLELEVERARM log is output in IMU Body frame.
The
VARIABLELEVERARM
log will not be published or used internally
unless a
SETINSROTATION RBM
command is sent.
GIMBALLEDPVA
This log has the same format as the INSPVA log, but contains the attitude rotated back
to the null gimbal position. When the gimbal mount is in its zero locked position, the
GIMBALLEDPVA attitude will match the attitude given in the INSPVA log. If the
translational offset to the gimbal center of rotation has been provided, the position and
velocity output are offset to this position. Otherwise, the position and velocity values are
given at the IMU center of navigation.
INSPVA,
INSPVAS,
INSPVAX
The INSPVA log is synchronous so does not depend on the entry of the
INPUTGIMBALANGLE
command. However when the gimbal angles are non-zero, the
INSPVA log no longer represents the orientation of the gimbal mount / vehicle, but rather
the current orientation of the unlocked gimbal platform. If the orientation of the vehicle is
important, use the GIMBALLEDPVA log.
Table 30: Logs used with Variable Lever Arm
Rotations and Translations
For the information provided by the system to be meaningful, the following offsets have to be set correctly. By
default the system assumes that the IMU Body frame, gimbal mount and Mount Body frame are coincident. If
this is not the case then additional commands are necessary to relate all of the different frames together using
the commands below. If attitude output is desired relative to an external camera, this can also be configured
using these commands.
When entering the SETINSROTATION commands described in the following table, the gimbal mount
should be locked (INPUTGIMBALANGLE rotations are zero).
Command
Purpose
SETINSROTATION
RBV
This command provides the orientation of the IMU Body frame while the gimbal frame is
in the locked null position. This is required information before the SPAN system can
complete an inertial alignment. The
SETINSROTATION RBV
command relates the
IMU Body frame (b) to the Vehicle frame (v).
Once an RBV rotation has been provided, default attitude output will be referenced to
the Vehicle frame.
SETINSROTATION
RBM
This command relates the IMU Body frame (b) to the Mount Body frame (m). This
information is required for interpreting the rotation angles from the
VARIABLELEVERARM
log correctly.
Table 31: Commands used with Variable Lever Arm
