An air for the future

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. Email Festo advanced projects Shadow Robot Company</a>


* 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

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