Master Thesis - Hochschule Bonn-Rhein-Sieg

5. Algorithms Master Thesis Björn Ostermann page 82 of 126
Since at this point the fluctuation noise and the robot have been identified, all other intrusions have to
be dynamic objects.
One main advantage of using the grown region rather than the position given by the robot’s PLC itself,
is that the grown regions also automatically include tools and workpieces the robot is wielding.
5.3 Detecting collisions
In the dynamic workplace, collisions between the robot and other dynamic objects are possible. This
can happen due to several facts:
- The robot is approached by dynamic objects while standing still (stopped by the proximity
monitoring).
- The dynamic object is approaching the robot faster than the robot can avoid it, due to its reduced
speed.
- The robot has no more space for avoiding motions.
If a collision between the robot and a dynamic object occurs their corresponding regions would merge,
and the algorithm distinguishing the robot from other objects would include the object into the robot.
This happens, since the robot is detected as the one region that includes the robot’s base centre (see
chapter 5.2.4.3). The dynamic object would then be no longer considered an obstacle for the robot’s
movement and the program would plan the robot’s movement accordingly, leading to possible
injuries / damages to the intruding object.
Figure 60a and b depicts the described case, where one of the dynamic objects from Figure 60a merges
due to its movement with the robot in Figure 60b.
To avoid this problem, the current robot region is checked against the intruding object regions,
detected in the previous frame. If the robot region and the last frame’s object regions overlap, a
collision took place (Figure 60c).