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1.2 Commercial Robot Configurations and Types 9

are able to precisely move large loads. These robots have been used for
example in machining and surface finishing of precision industrial and
aerospace components such as bulkheads and air vehicle outer skins.

Figure 1.2.6: Cylindrical arm using scissor mechanism for radial prismatic motion
(courtesy of Yamaha Robotics).

The parallel-link robot is a closed-kinematic-chain system, and as such is
relatively difficult to analyze [Liu and Lewis 1993]. The control system design
problem is more difficult for these robots.

Drive Types of Commercial Robots

The vast majority of commercial industrial robots use electric servo-motor
drives with speed reducing transmissions. Both AC and DC motors are
popular. Some servo-hydraulic articulated arm robots are available now for
painting applications. It is rare to find robots with servo-pneumatic drive
axes. All types of mechanical transmissions are used, but the tendency is
toward low- and zero-backlash type drives. Some robots use direct drive
methods to eliminate the amplification of inertia and mechanical backlash
associated with other drives. Joint angle position sensors, required for real-
time servo-level control, are generally considered an important part of the
drive train. Less often, velocity feedback sensors are provided.

Copyright © 2004 by Marcel Dekker, Inc.