Page 202 - Sensing, Intelligence, Motion : How Robots and Humans Move in an Unstructured World

CHAPTER 5

Motion Planning for Two-Dimensional
Arm Manipulators

If we imagine constructions to be made with rigid rods ... we should find that
different laws hold for these from those resulting on the basis of Euclidean plane
geometry. The surface is not a Euclidean continuum with respect to the rods,
and we cannot define Cartesian co-ordinates in the surface.
—Albert Einstein,
Relativity: The Special and General Theory

5.1 INTRODUCTION

In Chapter 3 we have developed the foundations of the SIM (Sensing–Intelli-
gence–Motion) paradigm (called also sensor-based robot motion planning). Basic
algorithms were developed for the simplest case of a point robot that possesses
tactile sensing and operates in a two-dimensional scene populated with obstacles
of arbitrary shapes. The algorithms were then extended to richer sensing such as
vision, as well as to algorithm versions that take into account robot dynamics.
When the robot starts on its journey, it knows nothing about the shapes, locations,
and number of individual obstacles in the scene. It acquires information about
its surroundings from its sensors—much the way we humans see and listen and
smell when moving in the physical world. The robot’s only goal is to arrive at
its target location. This means that when it arrives there, it may still know very
little about the scene. In other words, knowing more about the scene is not the
objective. In a way, the less the robot knows about the scene at the end—that is,
the less it wonders around trying to locate its target—the better its performance.
This chapter is devoted to developing sensor-based motion planning for robot
arm manipulators. This work will be heavily based on the developments in
Chapter 3. While the basic strategies developed there can be used for real-
world mobile robots, their one very important use is to serve as a foundation
for motion planning strategies for robot arm manipulators. The importance of
this area for practice is underscored by today’s situation in the field of robotics:
In terms of actual utilization, overall investment, and engineering complexity
Sensing, Intelligence, Motion, by Vladimir J. Lumelsky
Copyright  2006 John Wiley & Sons, Inc.
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