inspection & monitoring
repair damage to the interior of jet engines and turbine
blades. Several of the solutions being developed use an
innovative snake-arm robot that is guided deep inside an
engine to perform inspections and repair defects. The
snake-arm was developed over the past decade and uses a
compliant-joint structure and multiple continuous
sections that enable it to bend ± 90°. The snake-arm can
be different widths and crucially has a hollow interior,
through which different tools or instruments can be
fitted. The design’s flexibility in terms of size and
movement means it forms the basis of several projects,
including a walking hexapod robot.
BOREBLENDING
One of the first on-wing technology projects at the UTC
was the Remote Inspection and Engine Repair (REINER).
The project concluded last year and was funded by the
UK’s Aerospace Technologies Institute and Rolls-Royce.
Researchers at the UTC have developed a remotelycontrolled
robot that deploys non-destructive testing and
repair probes using a snake arm.
The REINER robot can be used to repair a compressor
blade in a jet engine. These blades can be damaged by
ingested debris. Today, to carry out this repair an
engineer has to travel to where the engine is, inspect the
engine and then repair damaged blades using a
1 // The snake arm robot is
also being developed for
use in the nuclear industry
(Photo: Alex Wilkinson
Media)
2 // The robots feature an
empty space in the middle
so they can deploy fiber
optics and other tools
78 SEPTEMBER 2019 \\ AEROSPACETESTINGINTERNATIONAL.COM
technique known as boreblending, resulting in downtime
and expense.
The robot developed by the REINER project is
attached to the engine’s inspection port and a probe
descends into the compressor. A stereo camera mounted
on the end of the probe is moved using electric actuators
and examines the damage. Software built into the probe
measures the defect and the data is used to program an
end-effector equipped with a drill bit.
Researcher on the REINER project David Alatorre
says, “The tool uses the point cloud supplied from the
probe to generate a trajectory which the drill bit can then
follow to mill the defect layer-by-layer, smoothing the
edges so it does not introduce stress points were cracks
could develop.
“This process normally takes days, but with REINER
it can take just a few hours.”
The instrument-tool hybrid was recently successfully
tested in use with a real engine at Rolls-Royce’s
headquarters in Derby using a combination of 3G mobile
networks and wifi.
LARGE OR SMALL SNAKE ARMS
The smallest snake arm developed at the UTC is 6mm
wide and 175mm long and is formed of off-the-shelf
motors and electronics. All of the control software it uses
was developed inhouse. The latest research with this
smaller snake-arm is looking at how it can be deployed to
the last stage of a high-pressure compressor in an engine
with tools attached to it, so it can mill or use a laser
probe to remove materials.
Researcher Jorge Barrientos says, “Three cables
enable the robot to move in different directions, creating
10 degrees of freedom. Modelling the arms has been very
challenging because it is hard to get sensors inside it to
get data – accessing the places that we want to inside the
engine is tricky.”
Another snake-arm project is placing a 200mm snake
arm on the end of a 5m cable and using an automated
feeding mechanism guided by a camera on the front. The
tip of the arm moves with six degrees of freedom and
delivers a laser ablation tool via a mirror mounted on the
“We design and build everything
here ourselves. We aren’t buying
robots, we are developing them”
The UTC at Nottingham University
celebrates its 20th anniversary this year.
Initially focused on manufacturing,
research at the UTC has shifted in recent
years to include the development of
testing and inspection technologies.
Axinte, a specialist in machine tools, sees
the recent advances in robotics as
presenting an opportunity to develop new
platforms for machine tools.
To further this idea, around 15 of the
40 people in the Manufacturing and
On-wing Technologies UTC are involved
full time in robotics research. They
typically develop projects to TRL 4,
although some have advanced as far as
TRL 6.
BLADE DAMAGE
The UTC has several non-destructive
testing and inspection systems in
development which are used while an
engine is still on an aircraft wing. The
research projects combine probes, optics,
machine tools and tele-operated controls
in robotic systems to detect, diagnose and
5m
Length of longest
snake-arm robot in
development
1
2
/AEROSPACETESTINGINTERNATIONAL.COM