Dynamic constraints to fix specific axes

[amosr]

Hi DART community,

I'm currently learning DART and am trying to model a ladder-climbing robot. The robot has multiple end-effectors which can hang from the rungs. Right now, I'm modelling the hanging end-effectors by adding dynamic ball-joint constraints, which fix the end-effector to a particular point on the ladder and allow free rotation. However, these ball-joint constraints don't exactly model the constraints on the real robot: in reality, the end-effector is able to slide along the ladder rung, and can only really rotate around the ladder rung axis. Is there any way to model such a constraint? I haven't been able to find any examples of this sort of thing yet, so any pointers would be appreciated.

If there's no built-in support for these constraints, it looks like it might be possible to create a new constraint type by subclassing DynamicJointConstraint and implementing some sort of fixed-axis constraints that way. Would this be a reasonable approach?

Thanks,
Amos