A wheel rolling on the x-y plane of the world frame including
wheel mass and simple visualization. The rolling contact is
considered being ideal, i.e. there is no slip between the wheel and
the ground. The wheel can not take off but it can incline toward
the ground. The frame frame_a is placed in the wheel center point
and rotates with the wheel itself. Therefore, a rotational
joint with rotation axis n={0,1,0}
should be used
to connect the wheel to a carrier.
To work properly, the gravity acceleration vector g of the world must point in the negative z-axis, i.e.
inner Modelica.Mechanics.MultiBody.World world(n={0,0,-1});