Snake robot
to the rescue
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HYDRAULIC PRESSURE: The energy to move
the joints in the snake comes from a hydraulic water pressure
of 100 bar – strong enough to lift a car off the ground and
for the snake to break through a wall. Co-ordinated sequential
movements along the body move the snake forward.
PHOTO: Rune Petter Ness |
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A snake robot can perform life-saving operations
during a fire, an explosion and in other hostile environments.
Try to picture a snake-like robot that can
move into places that are too dangerous for humans to enter. The
snake can climb up stairs, force past beams and twist itself round
corners. Imagine that it has a built-in advanced water tap that
not only can be turned on and off, but can allow the direction of
the water flow to be altered.
VALVES AND
WATER HYDRAULIC MOTORS
This new robot system is now in the development stages at
SINTEF. A patent application has been filed and the research scientists
have built a demonstrator to prove that the particular research-related
challenges have been conquered. The work has so far consumed 18
months and a thesis at SINTEF. A Ph. D study, which is underway
at NTNU, is concerned with developing a control strategy for the
robot.
The snake contains 20 water hydraulic motors
that move the robotic joints – and a similar number of valves to
control the water flow to each motor. Each module consists of two
hydraulic motors and two valves. The outer layer is comprised of
a strong steel skeleton containing the joint modules,which can rotate
around two orthogonal axes. The joints are controlled by custom-built
electronics.
“It is much like the grab on an excavator
where different joints and movements are coordinated by the operator.
In this instance, the operator is the computer,” says Pål Liljebäck
of SINTEF. “There are angle sensors in each joint, and we can decide
with conplete accuracy the angle that we want in the joints. A camera
in the snake’s head makes operating the snake like driving a remote-controlled
car. The operator can tell the snake to move from A to B, and the
snake works out on its own how to accomplish this. It knows how
to cross a pile of materials, climb down on the back side and twist
itself round objects in order to get footing.”
The energy to move the joints comes from
100 bars of hydraulic water pressure. “This pressure is strong enough
to lift a car up off the ground, something that again explains how
the snake can in principle break through a wall. But both the hydraulic
pressure and the use of pure water without additives in the hydraulic
system have posed challenges”, Liljebäck says.
AT THE CUTTING
EDGE OF RESEARCH
A snake does not rely on any single part of its body to move
forward. Instead, it uses its entire body to create co-ordinated
movements that move it in the desired direction. Project manager
Øyvind Stavdahl says that the project, which is being conducted
in co-operation with NTNU Professor Kristin Y. Pettersen, is at
the cutting edge of research because of its attempts to recreate
a snake’s movement.
The steel skeleton and motors are being custom-built
at local workshops in Trondheim, partly because the research scientists
needed to take a novel approach in the construction of the water
hydraulic valves.
“The lack of space has been a major challenge,”
says Liljebäck. “We needed power valves that were small, water tolerant
and capable of controlling both the direction and the amount of
the water flow. The closest thing we found on the market that met
the criteria was valves used in Formula One racing cars, but these
cost NOK 100,000 each and didn’t tolerate water. As a result, we
decided to manufacture our own valves and, in co-operation with
a local workshop, we built a prototype from scratch.”
APPLICATIONS
The snake has a wide variety of applications: fighting fires where
humans can not enter due to heat or the risk of building collapse;
underwater operations in connection with maintenance of oil installations
on the sea floor; rescue operations in earthquake areas and potentially
explosive situations.
“Tunnel fires are explosive and it is extremely
dangerous for firefighters to enter the tunnel to extinguish the
fire,” says Stavdahl. “In such situations, it is possible to imagine
a whole nest of snakes slithering out from a layer in the tunnel.
Since the snake has modules, it is possible to design snakes for
different functions: snakes can, for example, provide oxygen masks
to people trapped in the tunnel, light up the tunnel or carry a
camera that provides firefighters outside an overview of the situation
without requiring them to enter.”
The research scientists are now talking with
American businesses concerning possible sales. Further research
is still required until a commercial model is available. But the
concept is clear. The project has been financed by Norsk Hydro’s
fund for SINTEF.
By Åse Dragland
Contact Pål Liljebäck, SINTEF
ICT
Tel: +47 73 59 44 74, email: pal.liljeback@sintef.no
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