Tom Shelley reports on some striking developments based on pneumatics
Robotic fish, an ion rocket powered airship, a personal
hovercraft and a humanoid robot all graced one of the stands at
this year's Hannover Fair as demonstrations of some of the
possibilities of what can be achieved using air and pneumatics.
Most remarkable has to have been the fish, which swam round large
tanks on the Festo stand under radio control, spitting bubbles at
passers by. As well as demonstrating the capabilities of the
company's Fluidic Muscles and robotic controls, it looks to be
well capable of underwater surveillance, monitoring and robotic
tasks, and points a way forward for Biomimetics as a way to
design future underwater vehicles.
The 'Airacuda' is 1m long, 280mm wide and 450mm high, and is
powered by a 1.5 litre compressed air bottle charged to 300 bar.
This provides enough power for the fish to be able to swim for
about 35 minutes. Propulsion is by applying air to expand and
shorten the 5mm diameter elastomeric tubes forming the Fluidic
Muscles, actuating the tail and fin in an 'S' shaped pattern just
like a real fish. Depth control is also modelled on the method
used by real fishes with an air bladder that can be flooded with
water or air. All electronic and pneumatic components are housed
in the head. The head, structure and tail fin are made from laser
sintered polyamide and the skin from silicone.
Taking to the skies
Even more technically advanced is the b-IONIC Airfish, developed
at the Technical University of Berlin under Festo guidance. At
the tail end is an electrostatic ion jet engine, in which 20 to
30kV DC applied to thin copper wires ionises air molecules. The
positive ions are then accelerated towards negatively charged,
ring shaped, aluminium counter electrodes at 300 to 400m/s
pulling along additional neutral air molecules, creating an
effective gas stream moving at 10m/s. In addition, two small
wings near the front have on their rear edges what are described
as, "Plasma ray" drives. These incorporate pairs of
lamellar electrodes separated by a 0.4mm thick insulating layer
of 'Kapton' or 'Teflon'. These electrodes are excited by a 10kV,
11kHz signal leading to the generation of a cold, ionised plasma
which is accelerated by a 10 to 100Hz low frequency electric
field, dragging neutral air molecules along with them. Resulting
ion jet velocities are in the range 10m/s to 100m/s.
Total thrust is 8 to 10g which is orders of magnitude greater
than the mN thrusts typical of robotic deep space craft from
which the base technology originates. The Airfish body is a
streamlined, 9 cubic metre, helium filled balloon, 7.5m long and
1.83m in diameter. Project manager at TU Berlin was Dipl.-Ing
Berkant Göksel in the Institute for Process Engineering, Bionics
and Evolution Technology Department. Team members present seemed
somewhat disappointed that the show organisers would not let them
fly it round the hall.
While its 0.7m/s top speed is too slow for outdoor use, DTI
Global Watch reports that a Russian team at the General Physics
Institute in Moscow has a project to develop a microwave excited
air plasma jet engine for supersonic and hypersonic aircraft.
Research laboratories in many countries have looked at and are
still looking at air plasma generation to reduce or eliminate air
friction. The designers of the Airfish see advantage in using the
entire surface of an aircraft for plasma propulsion purposes,
generating thrust and eliminating friction both at the same time.
UFO watchers report having seen the occasional experimental craft
with tell-tale violet glows on wing edges in the UK and elsewhere
but we presently have no information on the success or otherwise
of any of these projects.
Personal hovercraft
Entirely suited to use outside, and something we imagine every
teenager would love to get their hands on is the personal
Hovercraft Vector developed by graduate students Dipl.-Ing Albert
Mielke and Dipl.Ing Daniel Wagner at the University of Applied
Sciences at Bielefeld.
The goal of their diploma thesis was to come up with better means
to steer and stop small hovercraft without having to turn them
round to direct their thrust in the opposite direction to their
original course.
Steering and stopping is achieved by distributing the airflow
from the propeller across the entrances to two ducts. Each of the
ducts has a pair of servo tabs that works in a similar manner to
the thrust reversers on jet engines. As a result, the amount of
air emitted either to the front or rear of the hovercraft can be
adjusted continuously. The prototype has been tested over land
and water and is said to have demonstrated high manoeuvrability
and showed up no problems when starting, stopping or cruising
forwards or backwards. Photographs taken by Festo show it being
driven around on a flat roof, which should give some indication
of the degree of confidence to be had in its controllability.
Length is 2.6m and width 1.5m. Dead weight is 160kg and maximum
weight, 320kg. It is powered by a 50kW, Rotax 552 engine acting
on a 760mm diameter 8 bladed Wingfan. Top speed is 85km/h
(53mph). Despite using no Festo parts whatsoever, the company
supported this project because the designers were again making
use of air.
Emulating the human
A long running project based on Fluidic Muscles has been to try
to build humanoid robots. The first attempts we reported were by
the Shadow Robot Company in North London, which to our knowledge
originally invented the Air Muscle concept used in the Fluidic
Muscle in 1982, and whose robotic hand was featured in Eureka's
July 2002 cover feature story. The complexity of emulating human
abilities is immense - Shadow Robot has been developing its
humanoid biped for nearly 20 years now - and so we were not
entirely surprised when the Humanoid Muscle-Robot being
demonstrated on the Festo stand got stopped. This particular
development is the result of a joint venture between Evologics,
the Department of Bionics and Evolutionary Technology at the
University of Berlin and Festo. It only attempts to reproduce
human movements of hands, arms and torso in response to sensors
attached to a human operator. It nonetheless requires four
microprocessors, 52 position sensors and 52 actuators. The goal
is to enable telerobotic operations with full human abilities in
hostile environments and advanced prosthetics. Development
continues.
www.festo.com
fish@de.festo.com Email
Festo advanced projects
www.shadowrobot.com
Shadow Robot Company</a>
Pointers
* A pneumatic biomimetic artificial fish opens up new avenues in
the design of remotely operated and autonomous underwater
vehicles
* Air plasma propulsion engines have been demonstrated to work in
an environment of other than high cost, top secret military
aerospace projects although these still exist
* Hovercraft control problems have finally been overcome thanks
to inspiration from jet engine thrust reversers
* The development of humanoid muscle robotics continues
For more technical
developments see www.eurekamagazine.co.uk