Unilateral contact constraints are not respected when importing a model from CAD into Simscape Multibody. To add these constraints, you will need to post-process the model after it is imported.
There are two ways to add the constraint that the end-effector does not go through walls in the the model:
1. Add a Planar Joint to the model that connects the World Frame and the end-effector. Then set limits on the x and y prismatic primitives of the joint that coincide with the walls.
2. Add two Spatial Contact Force blocks to the model to model the contact between the walls and the end-effector. However, Spatial Contact Force blocks cannot currently be used with CAD geometry, so the user would have to add "proxy geometry" as discussed here: Modeling Contact Force Between Two Solids
