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10 Commercial Robot Manipulators

Figure 1.2.7: Parallel-link robot (courtesy of ABB Robotics).

1.3 Commercial Robot Controllers

Commercial robot controllers are specialized multiprocessor computing
systems that provide four basic processes allowing integration of the robot
into an automation system: Motion Trajectory Generation and Following,
Motion/Process Integration and Sequencing, Human User integration, and
Information Integration.

Motion Trajectory Generation and Following. There are two important
controller-related aspects of industrial robot motion generation. One is the
extent of manipulation that can be programmed, the other is the ability to
execute controlled programmed motion. A unique aspect of each robot system
is its real-time servo-level motion control. The details of real-time control
are typically not revealed to the user due to safety and proprietary information
secrecy reasons. Each robot controller, through its operating system programs,
converts digital data from higher-level coordinators into coordinated arm
motion through precise computation and high-speed distribution and
communication of the individual axis motion commands which are executed
by individual joint servo-controllers. Most commercial robot controllers
operate at a sample period of 16 msec. The real-time motion controller
invariably uses classical independent-joint proportional-integral-derivative
(PID) control or simple modifications of PID. This makes commercially
available controllers suitable for point-to-point motion, but most are not
suitable for following continuous position/velocity profiles or exerting
prescribed forces without considerable programming effort, if at all.
Recently, more advanced controllers have appeared. The Adept Windows
family of automation controllers (http://www.adept.com) integrates
robotics, motion control, machine vision, force sensing, and manufacturing

Copyright © 2004 by Marcel Dekker, Inc.