Page 40 - Sensing, Intelligence, Motion : How Robots and Humans Move in an Unstructured World

BASIC CONCEPTS 15

With an eye on the primary subject of this book—robots capable of handling
tasks in an unstructured environment—we accept that reacting to sensing data is
essential for a robot’s being a robot. The definition of a robot accepted in this
text is as follows:

A robot is an automatic or semiautomatic machine capable of purposeful motion
in response to its surroundings in an unstructured environment.

Added in parentheses or seen as unavoidably tied to the defined ability is a clause
that a robot must include mechanical, computing, and sensing components.
While this definition disqualifies many of today’s robots as robots, it satisfies
what for centuries people intuitively meant by robots—which is not a bad thing.
Purists may still point to the vagueness of some concepts, like “purposeful”
(intelligent) and “unstructured.” This is true of all other attempts above and of
human definitions in general. Be it as it may, for the purpose of this book this is
a working definition, and we will leave it at that.

1.2.2 Space. Objects
A robot operates in its environment (workspace, work cell). The real-world robot
environment appears either in two-dimensional space (2D), as, for example, with
a mobile robot moving on the hospital floor, or in three-dimensional space (3D),
as with an arm manipulator doing car body painting.
Robot workspace is physical continuous space. Depending on approaches to
motion planning, one can model the robot workspace as continuous or discrete.
Robotics deals with moving or still objects. Each object may be

• A point—for example, an abstract robot automaton used for algorithm
development
• A rigid body—for example, boxes in a warehouse, autonomous vehicles,
arm links
• A hinged body made of rigid bodies—for example, a robot arm manipulator

The robot environment may includes obstacles. Obstacles are objects; depend-
ing on the model used and space dimensionality, obstacles can be

• Points
• Polygonal (polyhedral) objects, which can be rigid or hinged bodies
• Other analytically described objects
• Arbitrarily shaped (physically realizable) objects

1.2.3 Input Information. Sensing
Similar to humans and animals, robots need input information in order to plan
their motion. As discussed above, there may be two situations: (a) Complete
information about all objects in the robot environment is available. (b) There is