Page 50 - Sensing, Intelligence, Motion : How Robots and Humans Move in an Unstructured World

BASIC CONCEPTS 25

There are different criteria of quality of robot paths. We may want the robot
to do one or more of these:

• Execute a predefined path.
• Find an optimal path (the shortest, or fastest, or one requiring a minimum
energy, etc.).
• Plan a “reasonable” path.
• Plan a path that respects some constraints—say, a path that would not make
the robot bang into the walls of an automotive painting booth.

Robots in the factory environment tend to follow predefined paths, sometimes
with deviations allowed by their programs. Robot car painting operation is a good
example. Such tasks often put a premium on path optimization: After all, in a
mass production environment, shaving 1–2 sec out of a 50-sec cycle can translate
into large savings. On the other hand, for a robot operating in an environment with
uncertainty, optimality is ruled out and more often than not is of little concern
anyway. For instance, a mobile robot that is used for food and drug delivery in a
hospital is expected to go along more or less reasonable, not necessarily optimal,
paths. Either of these systems can also be subject to additional constraints: For
example, an arm manipulator may need to work in a narrow space between
two walls.