Master Thesis - Hochschule Bonn-Rhein-Sieg

4. Overall evading concept Master Thesis Björn Ostermann page 38 of 126
The performance of the program must be known, in order to compute the necessary safety distance the
robot has to keep from the operator (see chapter 6.3). For measuring the performance of the single
parts of the program it is necessary to acquire the time a single loop takes to compute. Thus, at the
beginning of each loop the current processor time is taken and compared to the time of the last loop.
This allows for an estimation of the frames that are handled in a certain amount of time.
The number of frames handled per second changes within a small range between two loops. Thus, in
order to avoid problems in the depiction of the value, it is not continuously transferred to the thread of
the GUI, but is acquired by the GUI if the user pushes the respective button (“Get FPS” – Frames Per
Second) and displayed alongside the button. Also this has the advantage that the value can be better
taken during specific situations.
The first subpart that can be activated by the user in Figure 20 is the depiction of greyscale values.
These values represent the intensity of the light in the near infrared spectrum, reflected of observed
objects. A sample image is depicted in Figure 21a, including two operators in the workspace. The
depiction can be optionally enhanced by a histogram analyses that was developed during previous
work [78] (see chapter 5.1.1).
The second subpart is the depiction of the distance data as shown in the example in Figure 21b. This
algorithm (see chapter 5.1.2) was developed in another project [79] and already implemented in
previous work of this project [78].
a) b)
Figure 21: a) Intensity Image enhanced by histogram analysis and
b) Distance Image
These two subparts of the program are mainly used during the setup phase of the workplace, when it is
assembled or reassembled. In this phase the 3D camera has to be positioned and adjusted to the
workplace. Both views are useful, since they show the camera’s actual view. They show the region,
covered from the camera in its current position, as well as problematic parts of the regions, where the
distance values change during continuous measurements due to the camera’s inconsistencies (see
chapter 3.2 and report [80]). This can be used to manually optimize the camera’s position.