To push or not to push: on the rearrangement of movable objects by a mobile robot

Formulates and addresses the problem of planning a pushing manipulation by a mobile robot which tries to rearrange several movable objects in its work space. The authors present an algorithm which, when given a set of goal configurations, plans a pushing path to the "cheapest" goal or announces that no such path exists. The pushing path is found using a two phase procedure: context sensitive back propagation of a cost function, and a pushing path restoration phase. The latter is based on a gradient descent procedure which considers, at each step, only admissible neighboring configurations. The admissibility mechanism provides a primary tool for expressing the unique characteristics of the pushing manipulation. It also allows a full integration of any geometrical constraints imposed by the pushing robot and the pushed objects. The authors have proved the algorithm to be optimal and (resolution-) complete and give some simulation results in different scenarios, as well as some experimental results using a real platform.