# 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.