Master Thesis - Hochschule Bonn-Rhein-Sieg

4. Overall evading concept Master Thesis Björn Ostermann page 54 of 126
from
part 2
17
Collision
reset
Reset collision status
Transmit
collision status
to the Data
Exchange
Object
Collision
detected
Set robot’s speed to
zero
Figure 33: Flowchart path planning control thread – part 3
Handling collisions and transmitting the desired parameters
Transmit the
goal pose to the
Data Exchange
Object
Transmit the
robot’s speed to
the Data
Exchange
Object
Transmit the
movement
mode to the
Data Exchange
Object
Next Loop
If a collision is still reported, the robot’s speed has to be reduced to zero, which is handled in the next
step. Since, due to technical reasons, this may not stop the robot at all times, a speed of zero is handled
specially by the robot control thread (see chapter 4.5).
In the end of every path planning control thread loop, the goal pose, the desired speed and the
movement mode are transmitted via the data exchange object to the robot control thread.
4.5 Robot control
To be able to control the robot effectively, the exact pose of its tool centre point needs to be known.
This pose has to be acquired from the robot’s internal sensors and made known to the developed
program. On the other side, the pose data, computed in the path planning thread, have to be
transmitted to the robot’s PLC.
This data exchange between the PC-program and the robot is handled by the robot control task. Its
task, as shown in chapter 4.1 is to pull all necessary sensor information from the robot, containing the
current pose of all of the robot’s axes, and relay them to the path planning thread, as well as to relay
the movement commands from the path planning thread to the robot.
As a subtask, this thread also handles the manual movement commands, entered by the user in the
GUI.