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viii PREFACE

the new age. Consequently the governor quickly became a sensation
throughout Europe.
Master-slave telerobotic mechanisms were used in the mid 1940’s at Oak
Ridge and Argonne National Laboratories for remote handling of radioactive
material. The first commercially available robot was marketed in the late
1950’s by Unimation (nearly coincidentally with Sputnik in 1957-thus the
space age and the age of robots began simultaneously). Like the flyball
governor, the motion of a robot manipulator is evident even for the untrained
eye, so that the potential of robotic devices can capture the imagination.
However, the high hopes of the 1960’s for autonomous robotic automation
in industry and unstructured environments have generally failed to materialize.
This is because robotics today is at the same stage as the steam engine was
shortly after the work of Newcomen in 1712.
Robotics is an interdisciplinary field involving diverse disciplines such as
physics, mechanical design, statics and dynamics, electronics, control theory,
sensors, vision, signal processing, computer programming, artificial
intelligence (AI), and manufacturing. Various specialists study various limited
aspects of robotics, but few engineers are able to confront all these areas
simultaneously. This further contributes to the romanticized nature of
robotics, for the control theorist, for instance, has a quixotic and fanciful
notion of AI.
We might break robotics into five major areas: motion control, sensors
and vision, planning and coordination, AI and decision-making, and
manmachine interface. Without a good control system, a robotic device is
useless. The robot arm plus its control system can be encapsulated as a
generalized data abstraction; that is, robot-plus-controller is considered a
single entity, or ‘agent’, for interaction with the external world.
The capabilities of the robotic agent are determined by the mechanical
precision of motion and force exertion capabilities, the number of degrees of
freedom of the arm, the degree of manipulability of the gripper, the sensors,
and the sophistication and reliability of the controller. The inputs for a robot
arm are simply motor currents and voltages, or hydraulic or pneumatic
pressures; however, the inputs for the robot-plus-controller agent can be
desired trajectories of motion, or desired exerted forces. Thus, the control
system lifts the robot up a level in a hierarchy of abstraction.
This book is intended to provide an in-depth study of control systems
for serial-link robot arms. It is a revised and expended version of our 1993
book. Chapters have been added on commercial robot manipulators and
devices, neural network intelligent control, and implementation of advanced
controllers on actual robotic systems. Chapter 1 places this book in the
context of existing commercial robotic systems by describing the robots
that are available and their limitations and capabilities, sensors, and
controllers.

Copyright © 2004 by Marcel Dekker, Inc.