Abstract
This paper discusses the design of a novel compliant
in-pipe climbing modular robot for small diameter pipes. The
robot consists of a kinematic chain of 3 OmniCrawler modules
with a link connected in between 2 adjacent modules via
compliant joints. While the tank-like crawler mechanism provides
good traction on low friction surfaces, its circular cross-section
makes it holonomic. The holonomic motion assists it to re-
align in a direction to avoid obstacles during motion as well
as overcome turns with a minimal energy posture. Additionally,
the modularity enables it to negotiate T-junction without motion
singularity. The compliance is realized using 4 torsion springs
incorporated in joints joining 3 modules with 2 links. For a
desirable pipe diameter (Ø 75mm), the springs’ stiffness values
are obtained by formulating a constraint optimization problem
which has been simulated in ADAMS MSC and further validated
on a real robot prototype. In order to negotiate smooth vertical
bends and friction coefficient variations in pipes, the design was
later modified by replacing springs with series elastic actuators
(SEA) at 2 of the 4 joints.
