Posing polygonal objects in the plane by pushing

International Journal of Robotics Research, To appear January 1998.

Srinivas Akella and Matthew T. Mason

Abstract

This paper studies the use of pushing actions to orient and translate objects in the plane. We 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. We 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. We formulate the search for such a sequence of pushes as a linear programming problem. We 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; we prove this planner complete. The planner, which uses an analysis of the mechanics of pushing an object, generates open-loop plans that do not require sensing. We describe experiments that demonstrate the validity of the generated plans.