46 Unit One Principles of Robotics
air system running throughout assembly areas, air is an economical and
readily available energy source. This makes the installation of robots that
use pneumatic actuator drives easier and less costly than that of hydraulic
robots. For lightweight pick-and-place applications that require both speed
and accuracy, a pneumatic robot is potentially a good choice.
Pneumatic actuator drives work at high speeds and are most useful for
small-to-medium loads. They are economical to operate and maintain and
can be used in explosive atmospheres. However, since air is compressible,
precise placement and positioning require additional components to achieve
the smooth control possible with a hydraulic system. These components
are discussed in later chapters. It is also difficult to keep the air as clean
and dry as the control system requires. Robots that use pneumatic actuator
drives are noisy and vibrate as the air cylinders and motors stop.
Shape of the Work Envelope
Robots come in many sizes and shapes. The type of coordinate system
used by the manipulator also varies. The type of coordinate system, the
arrangement of joints, and the length of the manipulator’s segments all
help determine the shape of the work envelope. To identify the maximum
work area, a point on the robot’s wrist is used, rather than the tip of the
Figure 2-26. Large robots that use hydraulic drive systems perform a demonstration at a
manufacturing trade show. (ABB Robotics)