Magnetic Locomotion for In-Pipe Inspection Robots

Pipeline Inspection Gauge’s, (PIGs) currently inspect 95.4% of the United
Kingdom’s National Transmission System (NTS) for the transportation of
natural gas. The remaining 4.6% found in Above Ground Installations
(AGIs) is deemed ”unpiggable” due to its complex geometry. Current robotic
technology entering these pipelines requires expensive modifications
to the pipeline to gain inspection access. A system that can bypass modifying
the pipe and complete a condition inspection could generate a minimum
saving of £60 million and 2145 tonnes of CO2 over a 20 year period.
This thesis explores new approaches towards the robotic inspection of
ferrous pipeline systems with the design and development of a wheeled magnetic
robot for sub 100mm pipelines. The work begins with a thorough
literature review surrounding the field of in-pipe robotics. The target environment
is analysed and the requirements and specification of the robot
are generated. Methods of creating magnetic traction wheels are explored
and a rubber coated flux plate magnetic array wheel is developed and tested
experimentally. The developed flux plate array wheels were found to channel
the power of 6 rare-earth magnets into a single wheel contact point and
created a force equal to that of the 6 magnets (83N) combined at the cost
of a 90% reduced field depth. The application of rubber coating increased
the frictional co-efficient μs of the wheels from 0.27 to 0.71, at the cost of
halving the contact force to a mean of 41N. A high level LabVIEW control
system was developed to communicate with the robot’s micro-controller
over wireless Bluetooth using a custom serial protocol to minimise the message
size for speed. Conceptual mechanical designs were conceived and two
systems chosen to suit requirements for a 2-inch (50.8mm) pipeline, and a
4-inch (101.6mm) pipeline were developed further. A robust prototype of
the 4-inch robot was fabricated using 3D printing techniques, the design
was preferred for its curved wheelbase geometry, allowing it to negotiate
convex and concave corner cases. Unlike current magnetic systems of its
size the robot was found to complete all orientations of descending convex
cases as well as all corner case angles of 115 degrees or greater.