  It is difficult for robots to retrieve objects in densely cluttered lateral
access scenes with movable objects as jamming against adjacent objects and
walls can inhibit progress. We propose the use of two action primitives --
burrowing and excavating -- that can fluidize the scene to un-jam obstacles and
enable continued progress. Even when these primitives are implemented in an
open loop manner at clock-driven intervals, we observe a decrease in the final
distance to the target location. Furthermore, we combine the primitives into a
closed loop hybrid control strategy using tactile and proprioceptive
information to leverage the advantages of both primitives without being overly
disruptive. In doing so, we achieve a 10-fold increase in success rate above
the baseline control strategy and significantly improve completion times as
compared to the primitives alone or a naive combination of them.
