11.1.3 User-Defined Generalized Constraint

If the selection of predefined generalized coordinate constraints is not sufficient, the GenConstraint function can be used to create constraints with any number of generalized coordinates representing any geometric relationship between two bodies that can be written algebraically.

The user-defined generalized coordinate constraint.

In Modeler2D, rotation is a counterclockwise angle. In Modeler3D, rotation is specified in the {ang, axis} format, and it can be a single rotation or a sequence of rotations of the form used by RotationLock3.
The trick to creating a valid constraint with GenConstraint is to make the pointi and rotation arguments symbolic functions of the generalized coordinate symbols symi. For example, the following constraint object would introduce a slave body that is constrained so that its origin lies on a parabola in the Y-Z plane, and its rotation is about the Z axis only. The position of the body along the parabola is represented by tau, and the rotation angle of the body about the Z axis is represented by phi.

Here is a GenConstraint example.

In[11]:=

Out[11]=