Introduction
English, Revision 06, Date: 12.07.2011
6
For the detection of the track, a static procedure that compares the relevant selected
lines of the camera picture with a model track of predefined width, is used. The degree
of compliance is important. The higher the degree of compliance with regards to the
width and contrast of the line, the higher the so-called covariance value. If the covari-
ance value exceeds a threshold determined during the commissioning of the system,
the track becomes valid and the location of the covariance maximum is converted into
a deviation value.
In case there are two maxima the location of the stronger maximum is used for the cal-
culation of the track deviation. If there are two or more maximas and branching is
planned, the locations of the two biggest maxima are used. For the calculation of the
deviation, depending on the indicated branching mode, the right or left maxima are
used accordingly. Afterwards two different sets of parameters can be used for each of
the two connectable cameras.
NOTE!
For each optical image processing a constant lighting for good
results is required. Because of this, environmental light and its
reflection on the ground have to be shielded from the camera. A
shining/reflective dark track or background are also not good for
the camera for track detection.
1.3
Barcode
The following picture shows the recording of a track with an additional barcode. The
record was taken with a Frame Grabber, which is connected to the monitor exit of the
line tracker.
Figure 1
Track with barcode
The calculated track deviations will be displayed in combination with the covariance
values.
The code is read form the first and last line of the track marker, then it is decoded and
compared. If the codes match, it will be checked whether the minimal symbol contrast
exceeds the set threshold SCmin or not.
track marker
Rest areas
track
2/5 interleaved,
Barcode, 2-digit