Agriculture Reference
In-Depth Information
+20
+10
working -
width
24 m
12 m
0
24 m
12 m
-10
12 m
-20
24 m
0
1
2
3
4
5
tractor speed in m / s
0
3.6
7.2
10.8
14.4
18.0
tractor speed in km / h
Fig. 9.35 Positional lag error versus tractor speed for three fertilizer spreading techniques. The
positional lag error is the difference between the offset distance and the time-lag distance (From
Griepentrog and Persson 2001 , altered)
For precise site-specific application, the distance that the machinery moves in the
field within the time-lag is important. If this time-lag distance does not match the
total offset-distance, an error in the site-specific placement of the fertilizer results.
Any difference between the offset-distance and the time-lag distance here is called
positional lag error , which can be positive or negative.
The aim is to have a positional lag error close to zero. In case the positional lag
error is positive - i.e. the total offset-distance is larger than the time-lag distance - a
correction can rather easily be obtained by purposely increasing the response time
of the controller.
If the positional lag error is negative, the travel speed can be reduced in order to
decrease the time-lag distance. However, this deteriorates the labor efficiency of
field operations. So the question is, which positional lag errors occur with the pres-
ently dominating distributing techniques and their typical time lags.
As can be seen from Fig. 9.35 , the mounted centrifugal spreaders have posi-
tional lag errors that are positive except for very high tractor speeds. Yet these posi-
tive lag errors can rather easily be removed by adjusting the control devices for
longer response- or default times. Contrary to this, the mounted pneumatic spread-
ers have negative positional lag errors with the exception of very low tractor speeds.
These errors can only be avoided by driving more slowly.
Search WWH ::




Custom Search