Rolling constraint for wheel that is always perpendicular to x-y plane


This information is part of the Modelica Standard Library maintained by the Modelica Association.

Joint for a wheel rolling on the x-y plane of the world frame intended for an idealized wheelset. To meet this objective, the wheel always runs upright and enables no slip in the longitudinal direction of the wheel/ground contact.

On the contrary, the wheel can optionally slip in the lateral direction which is reasonable for the wheelset where just one of the wheels should be laterally constrained.

The frame frame_a is placed in the intersection of the wheel spin axis with the wheel middle plane and rotates with the wheel itself. A wheel body collecting the mass and inertia should be connected to this frame.


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});

Parameters (2)



Type: Radius (m)

Description: Wheel radius


Value: true

Type: Boolean

Description: = true, if lateral sliding constraint taken into account, = false if lateral force = 0 (needed to avoid overconstraining if two ideal rolling wheels are connect on one axis)

Connectors (1)


Type: Frame_a

Description: Frame fixed in wheel center point. x-Axis: upwards, y-axis: along wheel axis

Used in Components (1)



Joint (no mass, no inertia) that describes an ideal rolling wheel set (two ideal rolling wheels connected together by an axis)