Master Thesis - Hochschule Bonn-Rhein-Sieg

5. Algorithms Master Thesis Björn Ostermann page 81 of 126
noise, the size of a region is counted while it is being filling (see chapter 5.2.4.1). If this size is below
a certain threshold, the region is dropped from further processing. Figure 58 shows the objects of the
sample workspace set-up that remain after size filtering.
Figure 58: Remaining objects after region size filter
Objects that only partially enter the camera’s view from the outside cause only small regions. For
example this is the case, if only the hand of a human enters the visual field. If the number of pixels in
those regions is smaller than the threshold, they are eliminated as well. Therefore the application of
this filter is only possible in a workplace, where the camera’s view on the robot is larger than the
robot’s possible reach (see Evaluation of safety in chapter 6.3).
5.2.4.3 Distinguishing the robot from objects
To distinguish the robot from other dynamic objects in the environment, the robot’s base was targeted
manually in the intrusion map (see chapter 3.3).
Every region that is extracted by the region growing algorithm (see chapter 5.2.4.1) is cross referenced
with the base’s centre position. If this position is in the given region, the region is set as the robot’s
region, as shown in Figure 59.
Figure 59: Robot region identified by its base’s centre (blue cross)