  Contact can be conceptualized as a set of constraints imposed on two bodies
that are interacting with one another in some way. The nature of a contact,
whether a point, line, or surface, dictates how these bodies are able to move
with respect to one another given a force, and a set of contacts can provide
either partial or full constraint on a body's motion. Decades of work have
explored how to explicitly estimate the location of a contact and its dynamics,
e.g., frictional properties, but investigated methods have been computationally
expensive and there often exists significant uncertainty in the final
calculation. This has affected further advancements in contact-rich tasks that
are seemingly simple to humans, such as generalized peg-in-hole insertions. In
this work, instead of explicitly estimating the individual contact dynamics
between an object and its hole, we approach this problem by investigating
compliance-enabled contact formations. More formally, contact formations are
defined according to the constraints imposed on an object's available
degrees-of-freedom. Rather than estimating individual contact positions, we
abstract out this calculation to an implicit representation, allowing the robot
to either acquire, maintain, or release constraints on the object during the
insertion process, by monitoring forces enacted on the end effector through
time. Using a compliant robot, our method is desirable in that we are able to
complete industry-relevant insertion tasks of tolerances <0.25mm without prior
knowledge of the exact hole location or its orientation. We showcase our method
on more generalized insertion tasks, such as commercially available
non-cylindrical objects and open world plug tasks.
