Master Thesis - Hochschule Bonn-Rhein-Sieg

3. Hard- and software Master Thesis Björn Ostermann page 24 of 126
f
�n� t
�
max
end
6
i �1
�n� � tstart
�n� �t�� i � t �� i �
end
Equation 1: Calculating the factor f for the speed of the individual angle n
according to the description in [76]
f �n� factor to be applied to maximum speed of angle n
tstart �n� start time of movement for angle n
tend �n� end time of fastest movement for angle n
The other, more complex, method to move the robot’s endpoint from one position to another is to
calculate a straight path between those points. To achieve this, the desired line is separated into small
changes and for every such change the angles of the axes are calculated, using inverse transformation.
Afterwards the results are connected by interpolation. Thus, the more points are used, the higher the
accuracy of the path.
Moving on a straight path can cause problems, if singularities exist in the calculated path. Singularities
are special points in the robot’s workspace where two or more joints are collinear (joint four and six in
the shown configurations in Figure 6 and Figure 7). In those points a multitude of possible
configurations exist (see [70] chapter 3.23). The singularities can cause problems when they exist in a
calculated path, because the robot might have to change the arms configuration (e.g. from flip to
no flip), which can not be done instantly. Thus the robot has to stop at such a point, which in turn can
be bad for the process (e.g. in special welding cases).
While being one of the smaller Reis robots, the RV30-16 can still handle up to 16 kg, which should be
enough for demonstrative purposes. Also the speed of the robot, which can be up to 4 m/sec is
sufficient for this task.
The robot is also equipped with electronic safety trips [48], designed by REIS. These trips monitor the
position of all of the robot’s joints and shut down the robot, if any joint malfunctions. Malfunctioning
can be a diversion from the parameters transmitted by the robot’s PLC, a dangerous increase in the
joints speed, e.g. while driving through a singularity, or entering of a zone that has been prohibited in
the setup phase of the trips. Finally, the trips guaranty that the robot’s endeffector is at the desired
position.
start