Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

Chapter 8 Pipe Crawlers and Other Special Cases 225
Figure 8-6 Inchworm
multi-section roller walker
get high forces on the pipe walls, generating high-friction forces.
Steering, if needed, is accomplished by rotating the coupling between
the two sections.
This coupling is also the inchworm section, and forward motion of the
entire vehicle is done by retracting the front bladder, pushing it forward,
expanding it, retracting the rear section, pulling it towards the front section,
expanding it, then repeating the whole process. Travel is slow, and
this concept does not deal well with obstructions or sharp corners, but
the advantage of very low pressures on the pipe walls may necessitate
using this design. A concept that uses this design was proposed for moving
around in the flexible Kevlar pipes of the Space Shuttle.
Another inchworm style pipe crawler has a seemingly complex shape,
but this shape has certain unusual advantages. The large pipes inside
nuclear reactor steam pipes have sensors built into the pipes that extend in
from the inner walls nearly to the center of the pipe. These sensor wells
are made of the same material as the pipe, usually a high-grade stainless
steel, but cannot be scraped by the robot. The robot has to have a shape
that can get around these protrusions. An inchworm locomotion vehicle
consisting of three sections, each with extendable legs, provides great
mobility and variable geometry to negotiate these obstacles. Figure 8-6
shows a minimum layout of this concept.