POWER November 2020 - 33

GENERATOR MAINTENANCE
the fact finder. A special wireless protocol
allows the VIR to operate wirelessly,
while still ensuring full high-definition
(HD) image quality. The total height of
the robot is a mere 19 mm, which allows
it to be easily deployed in most generators
(Figure 1). The unique motor drive
layout enables the VIR to move freely
along the lateral surface of the generator
rotor. Diagonal travel and turning in place
thus become helpful maneuvers.
There are two options when it comes
to piloting the VIR. It can either be
driven manually to gather a quick status
overview, or it can operate in fully
automated mode by autonomously following
the visible edge between a generator
wedge and the rotor main body.
The initial concept was for the VIR to
be manual, but it became apparent that
there were advantages in having autonomous
driving options. In manual mode
the VIR drives like a tank with the two
sides controlled independently so that it
moves forward, backward, or sideways
by alternating both speeds. The advantage
of the autonomous driving mode
is that the specialist can study the images
in real time, rather than having to
concentrate on controlling the robot.
The pictures are transmitted with low
latency so the inspector can view the
results as they are scanned.
An Impressive First Outing
All this effort finally came to fruition in
October 2019 when the project team
successfully deployed the robot commercially
for the first time on a built-in
generator in Asia. The customer was
incredibly pleased with the technical
implementation and the significant time
savings compared to dismantling.
During the inspection, it was discovered
using the VIR that there was a
problem with condensation. This was
evidenced by the presence of rust (Figure
2). The VIR is operated by a specialist
who can interpret the images instantly,
allowing timely feedback to be delivered
to the customer. During this assessment,
the specialist determined that the
condensation problem was based on the
temperature and the humidity in the region,
and was able to discuss different
ways to control the temperature when
the generator was not in operation.
Rusting is not the only discrepancy
that a visual inspection can identify.
When a generator suffers local short
circuit events, it leaves slight discolorations-the
area affected has a blue tint
to it. Another crucial check is that all the
November 2020 | POWER
to a computer as opposed to manual detection
by a specialist.
The final objective is pattern recognition,
but to achieve this requires inspectors
to build a library of similar images,
which is lacking at present. This library
of images needs to be taken from the
same camera angle, with identical lighting
and similar focus-all challenges that
have yet to be overcome.
There are other inspection robots
on the market but what makes the VIR
unique is the ability to select its own
route. Most of the other devices drive on
the stator because this has a natural gap
that can be used to guide the robot; they
run essentially on a " train track, " held in
position magnetically. The unique thing
about the VIR is that users can drive anywhere
they want to inside the generator.
The other unique attribute is that the
VIR is wireless-it has traditionally been
challenging to get a signal out of 50 tons
of copper.
2. This image shows areas of corrosion that
were identified inside a generator using the
VIR. Courtesy: Siemens
cooling holes are unobstructed, this is
especially important in smaller generators
that rely on air cooling to control
their temperature.
Adding Intelligence to the Robotic
Platform
At present, the VIR relies on the experience
and knowledge of the inspector,
but there are plans to incorporate added
intelligence to the platform. The robot
and robot inspection are being continuously
refined, and the development
team is collaborating with the University
of Heidelberg to enhance the process.
This work is being performed in four
phases, the first of which is to develop
an algorithm that generates a cohesive
overall image of the inspected routes
from the individual images of each video.
The challenge here was overcoming the
blurring effect on the images caused by
the robot's movement. The next step
was to stitch those individual pictures
taken by the robot into a " strip " representing
the lateral surface of the stator
or rotor.
With that established, the plan is to
move on to some historical analysis. The
team wants to be able to compare images
from different inspections and have
the program automatically highlight any
changes. This is a task that is well-suited
www.powermag.com
When Size Matters
The present VIR is 300 mm x 300 mm
and 19 mm high, the highest points are
the wheels, and a level of clearance has
been incorporated there. The overall size
is determined by the parts that have been
used. For example, the team wanted a 4K
camera and video transmission capability,
along with excellent lighting. Any reduction
in size of these components comes
with a resultant loss of performance, so
it is a balancing act. It is the same for the
motors and gearboxes, the smaller the
design becomes, the less torque is available
and the more strain the components
are placed under, which results in an increased
chance of failure.
The current version is designated as
the first commercial version and Siemens
has three sets of these-each set
comprises two robots for redundancy.
However, the company sees this as a
case of continuous improvement. It will
evaluate feedback from every job undertaken
and the engineers will constantly
enhance the robot. This process, again,
is hastened by the ability that 3D printing
gives the team to try and test things
rapidly. One thing is already clear: this
impressive robot can save users many
days of unnecessary downtime and hundreds
of hours of work on the part of the
assembly team. ■
-Mirko Düsel is CEO Generation
Service of Power Plants with Siemens,
Thomas Hullmann is VIR project lead,
Stefan Obermayr is VIR inventor, and
Paul Dreischer is VIR software engineer.
33
http://www.powermag.com
POWER November 2020

Table of Contents for the Digital Edition of POWER November 2020
