Master Thesis - Fachbereich Informatik

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5.3. EXPERIMENTAL RESULTS 123 Length [mm] 50.4 50.2 50 49.8 49.6 Measurements Mean 0 20 40 60 80 100 N (a) 1 0.8 0.6 0.4 0.2 Measurement distribution 0 49.4 49.6 49.8 50 Length [mm] 50.2 50.4 50.6 Figure 5.19: Repeatability results of a metallic cylinder simulating a tube of 49.99mm ground truth length. (a) 100 measurements of the gage at 30m/min. (b) Gaussian distribution of the results with µ =49.94 and σ =0.033. is also influenced by other parameters such as the tube orientation within the guide bars and the limits of the discrete input image (although subpixel techniques are applied). This experiment shows how accurate the vision-based system is able to measure even transparent tubes if the tube edge detection is successful. The experiment has been repeated with a metallic cylinder of 49.99mm length simulating an ideal tube (gage). The cross-section of this gage is circular and not deformable manually. The results of this experiment are shown in Figure 5.19(a) and (b). The mean over all 100 measurements is 49.94 with a standard deviation of 0.0331. This deviation is close to the error that has been estimated in Section 4.2.6 with respect to the maximum possible tube orientation within the guide bars. One can conclude, as long as the orientation within the guide bars is neglected, the maximum precision of the system is about 0.03mm for tubes that are ideally round and not bent. This is much more than twice as precise as human measurements. It is assumed that this precision could be even increased, if the tubes are not only approximately but ideally horizontally oriented. 5.3.6. Outlier The system is evaluated with respect to outliers in two steps. First more than 150 tubes (about 50mm, ∅8mm) are measured by the system at 30m/min. Approximately 1/3 of thetubesmeetthetoleranceswhiletheother2/3 have a manipulated length. The ground truth length of the tubes is known as well as the measuring order, i.e. each measurement can be assigned to a corresponding ground truth length. With the results of the previous experiments one can assume that the results of the black tubes will be better or equal to the transparent tube results. The results of this experiment are visualized in Figure 5.20. All of the 150 tubes are classified correctly. There is not a single false positive or false negative in the data. In the second stage of this experiment 30 manipulated and 22 good tubes are randomly mixed. All tubes are measured online at 30m/min while the blow out mechanism is (b)
124 CHAPTER 5. RESULTS AND EVALUATION 52 51.5 51 50.5 50 49.5 49 48.5 48 upper tolerance lower tolerance resulting mean length ground truth 0 20 40 60 80 100 120 140 Figure 5.20: 150 transparent tubes of both good and manipulated tubes have been measured by the system at 30m/min and compared to ground truth data. The system is able to reliably separate the tubes that meet the tolerances around the target length of 50mm from the manipulated tubes without any false positive or false negative. activated. This means tubes that do not meet the tolerances should be sorted out. Once all tubes have passed the measuring area it is checked how many of the manipulated tubes have also passed the blow out mechanism (false positives) and how many good tubes have been sorted out (false negatives). To simplify this task the manipulated tubes have been marked before. This experiment is repeated 22 times leading to a total number of 1144 inspected tubes. The results can be found in Table 5.7. The total detection rate is Ωtotal =0.99, i.e. 6 tubes out of 1144 could pass the measuring area without being measured at. Three tubes have been sorted out wrongly representing a false negative rate of ΩFN =0.0026, i.e. 2.6 . The false positives are more critical. 5 outliers have not been blown out correctly, thus, ΩFP =0.0043. However, it turns out that 4 of the 5 false positives occur at sequences with at least one non detected tube. Hence with the ratio of good and manipulated tubes of about 2:3, the probability is larger that the not inspected tube is a manipulated one. In this case the false positives are most likely not due to failures in measuring, but originated in the fact that these tubes have not been measured at all. At production, all non inspected tubes should be sorted out and revised to be sure that no outlier can pass. 5.3.7. Tube Length Measuring tubes of a different length requires the adaptation of the visual field of the camera. For tubes < 50mm this means placing the camera closer to the conveyor. However, due to the minimum object distance (250mm) of the 16mm lens used in the experiments before and with the consideration made in Section 3.2.1, a lens with a longer focal length is needed to yield the desired field of view. In this case a 25mm focal length lens is used.
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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
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4.4. TUBE LOCALIZATION 69 Global Th
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4.4. TUBE LOCALIZATION 71 but also
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Page 90 and 91: 4.5. MEASURING POINT DETECTION 75 f
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Page 94 and 95: 4.5. MEASURING POINT DETECTION 79 -
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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
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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 132 and 133: 5.3. EXPERIMENTAL RESULTS 117 Lengt
Page 134 and 135: 5.3. EXPERIMENTAL RESULTS 119 (a) (
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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
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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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