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2 Commercial Robot Manipulators

Flexible Robotic Workcells

In factory automation and elsewhere it was once common to use fixed
layouts built around conveyors or other transportation systems in which
each robot performed a specific task. These assembly lines had distinct
workstations, each performing a dedicated function. Robots have been
used at the workstation level to perform operations such as assembly,
drilling, surface finishing, welding, palletizing, and so on. In the assembly
line, parts are routed sequentially to the workstations by the transport
system. Such systems are very expensive to install, require a cadre of
engineering experts to design and program, and are extremely difficult to
modify or reprogram as needs change. In today’s high-mix low-volume
(HMLV) manufacturing scenario, these characteristics tolled the death knell
for such rigid antiquated designs.

Figure 1.1.1: UTA’s Automation and Robotics Test Cell.

In the assembly line, the robot is restricted by placing it into a rigid
sequential system. Robots are versatile machines with many capabilities,
and their potential can be significantly increased by using them as a basis
for flexible robotic workcells [Decelle 1988], [Jamshidi et al. 1992], [Pugh
1983] such as the UTA Automation and Robotics Test Cell in Figure 1.1.1.
In the flexible robotic workcell, robots are used for part handling, assembly,
and other process operations. By reprogramming the robots one changes the
entire functionality of the workcell. The workcell is designed to make full
use of the workspace of the robots, and components such as milling machines,
drilling machines, vibratory part feeders, and so on are placed within the
robots’ workspaces to allow servicing by the robots. Contrary to the assembly
line, the physical layout does not impose a priori a fixed sequencing of the
operations or jobs. Thus, as product requirements change, all that is required
is to reprogram the workcell in software [Mireles and Lewis 2001]. The

Copyright © 2004 by Marcel Dekker, Inc.