Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

226 Chapter 8 Pipe Crawlers and Other Special Cases
EXTERNAL PIPE VEHICLES
There are some applications that require a vehicle to move along the outside
of a pipe, to remove unwanted or dangerous insulation, or to move
from one pipe to another in a process facility cluttered with pipes.
CMU’s asbestos removing external pipe walker, BOA, is just such a
vehicle. Though not a robot according to this book’s definition, it is still
worth including because it shows the wide range of mobility systems that
true robots might eventually have to have to move in unexpected environments.
BOA is a frame walker. Locomotion is accomplished by moving
and clamping one set of grippers on a pipe, extending another set
ahead on the pipe, and grasping the pipe with a second set of grippers.
RedZone Robotics’ Tarzan, an in-tank vertical pipe walking arm, is an
example of a very unusual concept proposed to move around inside a
tank filled with pipes. This vehicle is similar to the International Space
Station’s maintenance arm in that it moves from one pipe to another, on
the outside of the pipes. Unlike the ISS arm, Tarzan must work against
the force of gravity. Since Tarzan is not autonomous, it uses a tether to
get power and control signals from outside the tank. The arm is allhydraulic,
using both rotary actuators and cylinders. All together, there
are 18 actuators. Imagine the complexity of controlling 18 actuators and
managing a tether all on an arm that is walking completely out of view
inside a tank filled with a forest of pipes!
SNAKES
In nature, there is a whole class of animals that move around by squirming.
This has been applied to robots with a little success, especially those
intended to move in all three dimensions. Almost by definition, squirming
requires many actuators, flexible members, and/or clever mechanisms
to couple the segments. The advantage is that the robot is very
small in cross section, allowing it to fit into very complex environments,
propelling itself by pushing on things. The disadvantage is that the number
of actuators and high moving parts count.
There are many other unusual locomotion methods, and many more
are being developed in the rapidly growing field of mobile robots. The
reader is encouraged to search the web to learn more of these varied and
sometimes strange solutions to the problem of moving around in uncommon
environments like inside and outside pipes, inside underground
storage tanks, even, eventually, inside the human body.