Master Thesis - Fachbereich Informatik

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5.3. EXPERIMENTAL RESULTS 119 (a) (b) (c) Figure 5.14: (a) Idealized cross-section of deformed tubes (frontal view). The measuring plane ΠM is defined based on an ideal circular tube (center). Deviations denoted as ∆1 (left) and ∆2 (right) influence the length measurement in the image projection. (b) Example of a deformed tube (No. 7 in Figure 5.12(b)) lying on the smaller side. The measuring points are closer to the camera and due to perspective, the tube appears measurable larger in the image. (c) The opposite effect occurs if a deformed tube (No. 11 in Figure 5.12(b)) lies on the larger contact area. changes in brightness, since they are more translucent than 8mm and 12mm tubes. At regions on the conveyor belt that transmit more light, the thin tubes almost disappear. Thus, one has to reduce the intensity of the light source. This is a tradeoff, because other regions that transmit less light get even darker while the structure of the belt is emphasized. If the contrast is too low, the tube can not be located in the profile. This problem could be prevented if one would use a more homogenously translucent conveyor belt. The 12mm diameter tubes yield generally a better contrast which can be seen on the detection rate of 98%. The number of per tube measurements ΩPTM is 3.12 compared to 2.8 for 6mm tubes. However, the average standard deviation is larger for the 12mm tubes with 0.24. A RMSE of 0.2 for both 6 and 12mm transparent tubes indicates the measuring results are almost equally accurate than black tubes of the same diameter, although the extrema are significantly larger. As already mentioned, these values can be influenced by a few outliers. The values of GT D show a much more uniform distribution of the deviations compared to black tubes. This is due to the fact that transparent tubes are more sensitive to strong background edges which can be wrongly detected as tube edge. Figure 5.17 gives an example of how the system can fail leading to a larger measured length. The poor contrast at the tube boundary can not be compensated by the stronger responses at thetubeedgeends. Themaximumcorrelationscoreisreachedatthebackgroundedge. This problem does not occur at black tubes due to the stronger contrast. Thus, in addition to the problems described for black tubes of 6 and 12mm diameter, transparent tubes may be measured longer than they really are. Figure 5.15 visualizes the experimental results with different diameters of transparent tubes. Again, this is only a section of the total number of measurements which are summarized more comprehensive in Figure 5.16 based on the ground truth distance. Compared to the experiments with black tubes there have been false negatives among the transparent tubes, i.e. tubes have
120 CHAPTER 5. RESULTS AND EVALUATION Length [mm] 52 51.5 51 50.5 50 49.5 49 48.5 48 measurements upper tolerance lower tolerance resulting mean length ground truth boundaries 0 10 20 Measurement number 30 (a) transparent, 6mm diameter Length [mm] 52 51.5 51 50.5 50 49.5 49 48.5 48 measurements upper tolerance lower tolerance resulting mean length ground truth boundaries 0 10 20 30 40 50 Measurement number (b) transparent, 12mm diameter Figure 5.15: Experimental results of transparent tubes (50mm length) with a diameter of 6 and 12mm at 30m/min. The plots show a section of the total number of tubes only. GTD [mm] 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 ground truth distance -0.7 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 Tube number (a) transparent, 6mm diameter GTD [mm] 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 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 Tube number (b) transparent, 12mm diameter Figure 5.16: Ground truth distance in mm of all measured transparent tubes with a diameter of 6 and 12mm at 30m/min.
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Fachbereich Informatik Department o
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Acknowledgments First of all, I wou
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Contents Acknowledgments iii Abstra
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Contents ix 5.3.7. TubeLength .....
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List of Tables 1.1. Rangeoftubetype
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List of Figures 2.1. AccuracyandPre
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1. Introduction Heat shrinkable tub
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1.2. PROBLEM STATEMENT 3 hazards, r
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1.4. RELATED WORK 5 Length [mm] Tol
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1.5. THESIS OUTLINE 7 The vision pa
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2. Technical Background 2.1. Visual
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2.1. VISUAL MEASUREMENTS 11 (a) Fig
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2.1. VISUAL MEASUREMENTS 13 Figure
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2.1. VISUAL MEASUREMENTS 15 � xd
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2.2. ILLUMINATION 17 tubes alternat
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2.2. ILLUMINATION 19 effect of comp
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2.3. EDGE DETECTION 21 i 2 i 1 0 (a
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2.3. EDGE DETECTION 23 N × 1 kerne
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2.3. EDGE DETECTION 25 These operat
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2.3. EDGE DETECTION 27 (a) 0 ◦ (b
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2.4. TEMPLATE MATCHING 29 accuracy
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3. Hardware Configuration This chap
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3.2. CAMERA SETUP 33 3.2. Camera se
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3.2. CAMERA SETUP 35 eachcolorchann
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3.2. CAMERA SETUP 37 Figure 3.4: Co
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3.2. CAMERA SETUP 39 adjusting scre
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3.2. CAMERA SETUP 41 further distan
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3.3. ILLUMINATION 43 f V 12mm 129mm
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3.3. ILLUMINATION 45 (a) (b) (c) Fi
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3.3. ILLUMINATION 47 (a) (b) Figure
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3.4. BLOW OUT MECHANISM 49 A light
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4. Length Measurement Approach Whil
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4.2. MODEL KNOWLEDGE AND ASSUMPTION
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4.3. CAMERA CALIBRATION 59 4.2.7. B
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4.3. CAMERA CALIBRATION 61 Figure 4
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4.3. CAMERA CALIBRATION 63 is compu
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4.4. TUBE LOCALIZATION 65 (a) (b) F
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4.4. TUBE LOCALIZATION 67 � 1 Psm
Page 84 and 85: 4.4. TUBE LOCALIZATION 69 Global Th
Page 86 and 87: 4.4. TUBE LOCALIZATION 71 but also
Page 88 and 89: 4.4. TUBE LOCALIZATION 73 Global Re
Page 90 and 91: 4.5. MEASURING POINT DETECTION 75 f
Page 92 and 93: 4.5. MEASURING POINT DETECTION 77 T
Page 94 and 95: 4.5. MEASURING POINT DETECTION 79 -
Page 96 and 97: 4.5. MEASURING POINT DETECTION 81 0
Page 98 and 99: 4.5. MEASURING POINT DETECTION 83 o
Page 100 and 101: 4.5. MEASURING POINT DETECTION 85 (
Page 102 and 103: 4.5. MEASURING POINT DETECTION 87 w
Page 104 and 105: 4.6. MEASURING 89 side of the tube,
Page 106 and 107: 4.6. MEASURING 91 fcor(x) =−(c1x
Page 108 and 109: 4.7. TEACH-IN 93 inthemeasuringplan
Page 110 and 111: 4.7. TEACH-IN 95 The pair of a pixe
Page 112 and 113: 5. Results and Evaluation 5.1. Expe
Page 114 and 115: 5.1. EXPERIMENTAL DESIGN 99 between
Page 116 and 117: 5.1. EXPERIMENTAL DESIGN 101 where
Page 118 and 119: 5.1. EXPERIMENTAL DESIGN 103 Ground
Page 120 and 121: 5.2. TEST SCENARIOS 105 enough, the
Page 122 and 123: 5.3. EXPERIMENTAL RESULTS 107 The t
Page 124 and 125: 5.3. EXPERIMENTAL RESULTS 109 Detec
Page 126 and 127: 5.3. EXPERIMENTAL RESULTS 111 Lengt
Page 128 and 129: 5.3. EXPERIMENTAL RESULTS 113 GTD [
Page 130 and 131: 5.3. EXPERIMENTAL RESULTS 115 gray
Page 136 and 137: 5.3. EXPERIMENTAL RESULTS 121 (a) (
Page 140 and 141: 5.3. EXPERIMENTAL RESULTS 125 Total
Page 142 and 143: 5.3. EXPERIMENTAL RESULTS 127 Color
Page 144 and 145: 5.3. EXPERIMENTAL RESULTS 129 Task
Page 146 and 147: 5.4. DISCUSSION AND FUTURE WORK 131
Page 148 and 149: 6. Conclusion In this thesis a func
Page 150: Appendix 135
Page 153 and 154: 138 APPENDIX A. PROFILE ANALYSIS IM
Page 155 and 156: 140 APPENDIX A. PROFILE ANALYSIS IM
Page 157 and 158: 142 APPENDIX B. HARDWARE COMPONENTS
Page 159 and 160: 144 APPENDIX B. HARDWARE COMPONENTS
Page 161 and 162: 146 Bibliography [18] C. Demant, B.
Page 163 and 164: 148 Bibliography [51] K.K. Pingle.
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Master Thesis - Fachbereich Informatik

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