Chapter 4 SPAN Operation
CPT7 and CPT7700 Installation and Operation User Manual v9
104
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log will not be published or used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the INSPVA log no longer represents the orientation of the gimbal mount / vehicle,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 18: 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 19: Commands used with Variable Lever Arm
