True Ground Speed Sensor (TGSS) 740
12
Installation
i
I
NFORMATION
It cannot be known with certainty if there is a problem introduced from an
obstruction in the -10 db area, because there are too many other parameters that
come into play (ground texture, reflection coefficient of interference, vibration level
of interference, etc.). The best practice is to design the mount so that there is plenty
of clearance for the radar line of sight.
The model is based on a mounting height of 1 meter. Any other height will require
that the radar beam model be stretched ratiometrically with the new height. This is
done by looking at the model as spherical coordinates and scaling the radius
proportionally to the 1 meter in the model.
4.1.5.
Installation Validation
After an installation location has been determined, the TGSS needs to be mounted
and evaluated to see if the Doppler signal is of acceptable quality.
The strength of the signal reflected back to the radar is determined mainly by the
texture of the ground. The more irregular the surface, the higher the return signal.
This is due to a greater reflecting area. On a very smooth surface, most of the signal is
reflected away from the radar.
4.1.5.1.
Line of sight evaluation
With the vehicle stationary over a smooth surface, slowly sweep the engine rpm over
it’s range.
Monitor the TGSS speed output to see if any false speed is shown. If a false speed
reading occurs, there is either a line of sight or vibration issue.
4.1.5.2.
Vibration analysis
In order to determine if the mounting has vibration, the vehicle should be positioned
over a rough surface. With the vehicle stationary, the engine rpm should slowly be
ramped through its range. Monitor the radar output speed to determine if different
rpm are causing a vibration induced speed.
If there is vibration induced speed, it can be from two sources:
1.
Excess vibration motion of the radar.
2.
Something vibrating within the radar's line of sight.
If the false speed occurs on a smooth surface as well, it is likely that there is a line of
sight issue.
If the problem has been determined to be due to excessive vibration on the radar
mount, the vibration source needs to be reduced or high vibration isolation is
required. Possible things to investigate are:
3.
Add extra weight to the radar mount to increase it’s isolation from vibration.
4.
Add vibration isolation to the mounting bracket installed on the vehicle.
5.
Relocate the radar to an area of lower vibration.
