Master Thesis - Fachbereich Informatik

5.3. EXPERIMENTAL RESULTS 113
GTD [mm]
0.7
0.6
0.5
0.4
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0.2
0.1
0
-0.1
-0.2
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ground truth distance
-0.7
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105
Tube number
(a)
1
0.8
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0
Measurement distribution
Ground truth distribution
49 49.2 49.4 49.6 49.8 50 50.2 50.4 50.6 50.8 51
Length [mm]
Figure 5.8: (a) Ground truth distance GT D in mm for black tubes (50mm length, ∅8mm)
at 30m/min. (b) Gaussian distribution of all measurements compared to the ground truth
distribution.
v[m/min] Ωtotal ΩPTM σtube GT Dmin GT Dmax GT D RMSE
10 0.99 9.6 0.06 -0.14 0.32 0.09 0.13
20 0.98 5.2 0.09 -0.16 0.29 0.08 0.11
30 1 3.9 0.15 -0.16 0.66 0.15 0.20
40 0.97 2.4 0.18 -0.27 0.75 0.23 0.28
Table 5.5: Evaluation results at different conveyor velocities v for transparent tubes (50mm
length, ∅8mm). The accuracy seems to decrease with faster velocities as can be seen at the
RMSE and the mean per tube standard deviation σtube. The number of per tube measurements
ΩPTM is smaller for transparent tubes. Due to the lower contrast it is more likely that
a tube is not detected as measurable.
are only marginally less precise. Furthermore, as an additional benefit, it is possible to
show that a sequence of tubes is systematically shorter than the target length (although
still in the tolerances). This information could be used to adjust the cutting machine until
µseq approximates the given target length.
Transparent Tubes The same experiments have been repeated with transparent tubes.
The results are summarized in Table 5.5.
The detection rate Ωtotal tends to decrease with an increasing velocity, although all
tubes have been detected at 30m/min in this experiment. 3% of the tubes have passed
the visual field of the camera without being measured at 40m/min.
Due to the poorer contrast of transparent tubes the probability increases that a tube
can not be located in the profile analysis step. This can be seen on the average number
of per tube measurements ΩPTM. While black tubes are measured about 11.4 timesat
v = 10m/min, the transparent tubes reach only 9.6 measurements per tube at the same
velocity. At 40m/min this number decreases to 2.4. At faster velocities, e.g. 55m/min,
the number of per tube measurements falls short of 1. Reliable measurements are not
(b)