  Precise perception of contact interactions is essential for fine-grained
manipulation skills for robots. In this paper, we present the design of
feedback skills for robots that must learn to stack complex-shaped objects on
top of each other (see Fig.1). To design such a system, a robot should be able
to reason about the stability of placement from very gentle contact
interactions. Our results demonstrate that it is possible to infer the
stability of object placement based on tactile readings during contact
formation between the object and its environment. In particular, we estimate
the contact patch between a grasped object and its environment using force and
tactile observations to estimate the stability of the object during a contact
formation. The contact patch could be used to estimate the stability of the
object upon release of the grasp. The proposed method is demonstrated in
various pairs of objects that are used in a very popular board game.
