Posing polygonal objects in the plane by pushing

Abstract

This paper studies the use of pushing actions to orient and translate objects in the plane. The authors use linear normal pushes, which are straight-line pushes in a direction normal to the pushing fence. These pushes are specified by the fence orientation and push distance. The authors show that a set of linear normal pushes can always be found to move any polygonal object from any initial configuration to any goal configuration in the obstacle-free plane. The object configuration is specified by its pose; that is, its position and orientation. The authors formulate the search for such a sequence of pushes as a linear programming problem. They then describe an implemented pose planner that uses this formulation to identify a sequence of linear normal pushes given any polygonal object, any initial pose, and any goal pose. This planner is proven to be complete and to have polynomial time complexity. The planner, which uses an analysis of the mechanics of pushing an object, generates open-loop plans that do not require sensing. The authors describe experiements that demonstrate the validity of the generated plans.