Sparse bins allow methods that avoid contact with other
obstacles to be successful. In APC 2015, once an object was
grasped (whether by suction or by fingers), it could be directly
extracted. However, more tightly-packed bins may require
brushing obstacles aside in order to reach and retrieve the
target object, as well as sliding the object along the bottom
or sides of the bin. The need to manipulate in contact may
radically change both the software and hardware methods
used in the APC (e.g., shifting the emphasis toward compliant
control and compliant hardware), and the level of sensing
required at the point of the manipulation (e.g., tactile and in hand
vision sensors). A key challenge to overcome in tightly packed
bins is to perform the necessary manipulation under
limited sensing and poor prior knowledge of the environment