Submitted version of the thesis - Airlab, the Artificial Intelligence ...

Chapter 4
Control
The motion mechanism is inspired from the ones that have been introduced.
In this Chapter, we will explain the wheel configuration model, movement
types, the script that is used to calculate the motor contributions
according to a set point, motor control behavior and the software implementation.
4.1 Wheel configuration
The configuration space of an omnidirectional mobile robot, is a smooth
3-manifold and can then be locally embedded in Euclidean space R 3 . The
robot has three degrees of freedom, i.e., two dimension linear motion and
one dimension rotational motion. There are three universal wheels mounted
along the edge of the robot chassis 120 ◦ apart from each other, and each
wheel has a set of rollers aligned with its rim, as shown in Figure 3.8. Because
of its special mechanism, the robot is able to simultaneously rotate
and translate. Therefore, the path planning can be significantly simplified
by directly defining the tracking task with the orientation and position errors
obtained by the visual feedback.
For a nonholonomic robot, the robot’s velocity state is modeled as the
motion around its instantaneous center of rotation (ICR). As a 2D point in
the robot frame, the ICR position can be represented using two independent
parameters. One can use either Cartesian or polar coordinates, but
singularities arise when the robot moves in a straight line (the ICR thus lies
at infinity). Hence, we used a hybrid approach that is defining the robot