[Studies in Computational Intelligence 481] Artur Babiarz, Robert Bieda, Karol Jędrasiak, Aleksander Nawrat (auth.), Aleksander Nawrat, Zygmunt Kuś (eds.) - Vision Based Systemsfor UAV Applications (2013, Sprin

A Distributed Control Group of Mobile Robots 161
• Change the speed of wheels i.e. set linear velocity of a robot.
• Rotate by given angle, at given angular velocity or at given constant radius.
• Move forward/backward by given distance.
• Go to a given location.
2.2 Skid Limits
Important fact is ensuring that the robot does not slide, as it would input errors to
the incremental magnetic encoder, which runs vital part of every algorithm at the
robot. That is why the on-board controller avoids skid of wheels, by limiting linear
and angular acceleration. It has to be taken into account by the Master Control
System, so that the system is cohesive. The limits are calculated in work [7] and
are listed in Table 1.
Table 1. Limits
Limit Value Unit
Acceleration 1
Angular acceleration 0.5
The was obtained experimentally by checking whether a set acceleration
causes any sliding and repeating the experiment successively. The value that is
used was additionally lowered by 50% in order to minimize the risk of skid, while
the was calculated from the interaction of wheels with the ground [7].
2.3 Vision System
The vision system provides coordinates and values of angles of robots and ball on
the playground. It acquires images from the camera, which is mounted permanently
above the playground, via a frame-grabber card. The view from the camera is
shown on an exemplary image at Figure 4.
Fig. 4. Playground seen by camera