A Case Study of Flexible Object Manipulation

This article describes a project undertaken to explore programming physical operations on complex flexible objects. Uncertainty about the exact state of the object makes it impossible to precisely specify the actions to be performed at the time the program is written. Furthermore, the detailed consequences of manipulations on flexible objects cannot be determined before the action is performed. Lacking precise specifications, the programmer must abstract the essential properties of objects and actions. In an effort to study manipulation offlexible objects, a system to tie knots in rope with a robot arm was developed. The system includes an extensible graph representation for knots, a vision system that binds the contour of a physical rope to an abstract description, and a knot-tying language based on parametric motion commands. Knots of modest complexity, such as a bowline or figure 8, can be tied in a variety of ropes with minimal constraints on the initial configuration of the rope. The work highlights the importance of software engineering principles and a good programming environment for robot program development.