UMAX0608XX‐1000. Tri‐Axial J1939 CAN Inclinometer. Version 9B
Page: 30-66
2
The Auto-Null Command is not a real configuration parameter. It always returns No value when being
read.
The
Coordinate Rotation Yaw, Pitch and Roll Angles
𝜓, 𝜃, 𝜙
) are used to change the original
orientation of the unit frame. The original orientation is shown on the inclinometer label. The
coordinate rotation angles are Euler angles applied in the standard yaw-pitch-roll order to the
unit frame.
Normally, the coordinate rotation angles are taken in 90-degree increments: 0, ±90, ±180, but
theoretically they can be assigned any value in the [-180…+180] degree range.
After the coordinate system is rotated, the user can install the inclinometer on the machine and
set the initial installation pitch and roll angles.
The initial installation pitch and roll angles are Euler angles used to transform the unit
accelerations from the unit frame to the machine frame. They can be written manually or set up
automatically when
Auto-Null Command
is set to
Yes
.
To set up the initial installation angles automatically, the user issues the
Auto-Null Command
when the machine is in the initial null-angle position, leveled on the operation area. The
machine frame is coincident with the Earth reference frame in this position, see
Unit Reference
Frames
.
The user should avoid the gimbal lock condition when issuing the
Auto-Null Command
since in
this case the
Initial Roll Angle
cannot be accurately defined, and the resulting machine frame
orientation can be random, see
Gimbal Lock
.
3.4.1.1 Unit Frame Orientation Examples
The user can change the unit frame orientation by applying the
Coordinate Rotation Yaw, Pitch
and Roll Angles
𝜓, 𝜃, 𝜙
) to the original default orientation of the unit frame.
For example, let us assume that the AX060800 unit in the original null-angle position is placed
vertically on the machine, long side up, and the angle of interest will be measured as the unit
pitch angle, see Figure 14. Remember, that the measured angle cannot be yaw angle, only
pitch or roll angle, see
Practical Recommendations
.
Pitch Angle
Y
X
Y
Z
Pitch Angle
Required Unit Frame
Orientation
Front View
Y points towards the
viewer
Figure 14. Unit Frame Orientation Example. New Unit Frame Orientation
This assumption will require a new unit frame orientation presented in Figure 14. In the new
orientation, the Z-axis points down to be coincident with the gravity vector, the X and Y axes
