STABLE PUSHING - MECHANICS, CONTROLLABILITY, AND PLANNING

We would like to give robots the ability to position and orient parts in the plane by pushing, particularly when the parts are too large or heavy to be grasped and lifted. Unfortunately, the motion of a pushed object is generally unpredictable due to unknown support friction forc es. With multiple pushing contact points, however it is possible to fi nd pushing directions that cause the object to remain fixed to the man ipulator These are called stable pushing directions. In this article w e consider the problem of planning pushing paths using stable pushes. Pushing imposes a set of nonholonomic velocity constraints on the moti on of the object, and we study the issues of local and global controll ability during pushing with point contact or stable line contact. We d escribe a planner for finding stable pushing paths among obstacles, an d the planner is demonstrated on several manipulation tasks.