VN-200 User Manual
UM004
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5.10
Reference Frame Rotation
Reference Frame Rotation
Register ID :
26
Firmware :
v0.1 and up
Access :
Read / Write
Comment :
Allows the measurements of the VN-200 to be rotated into a different reference
frame.
Size (Bytes):
36
Example Serial Read Register
Response:
$VNRRG,26,1,0,0,0,1,0,0,0,1*6A
Byte
Offset Name
Number
Format
Unit
Description
0
C[0,0]
F4
-
4
C[0,1]
F4
-
8
C[0,2]
F4
-
12
C[1,0]
F4
-
16
C[1,1]
F4
-
20
C[1,2]
F4
-
24
C[2,0]
F4
-
28
C[2,1]
F4
-
32
C[2,2]
F4
-
This register contains a transformation matrix that allows for the transformation of measured
acceleration, magnetic, and angular rates from the body frame of the VN-200 to any other arbitrary
frame of reference. The use of this register allows for the sensor to be placed in any arbitrary
orientation with respect to the user’s desired body coordinate frame. This register can also be used to
correct for any orientation errors due to mounting the VN-200 on the user’s circuit board.
{
}
[
] {
}
The variables
{ }
are a measured parameter such as acceleration in the body reference frame
with respect to the VN-200. The variables
{ }
are a measured parameter, such as acceleration in
the user’s frame of reference. The reference frame rotation register needs to be loaded with the
transformation matrix that will transform measurements from the body reference frame of the VN-200
to the desired user frame of reference. It is crucial that these two frames of reference be rigidly
attached to each other. All nine numbers are represented by single-precision floating-points.
The reference frame rotation is performed on all vector measurements prior to entering the
INS filter. As such, changing this register while the attitude filter is running may lead to
unexpected behavior in the INS output. After setting the reference frame rotation register to
its new value, send a write settings command and then reset the VN-200. This will allow the
INS filter to startup with the newly set reference frame rotation.
