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The development of the design

Richard worked for a time for a robotics company making turtles (G) for the education market but he found he disagreed with their approach. So he started building the first simple joint for a humanoid robot in his own home which he says was "amazingly successful". This was an articulated (G), knee-like arrangement which pushed a leg out.

However, he realised that the human body works by pulling - muscles pulling bones via tendons - and this was what he wanted to achieve. So he developed an air driven device rather like a wiggly, tubed air bed that shortened in length when it was inflated - thus pulling. This was the first step in developing the air muscle, which has become a very special product used world-wide. As a result people can now build robots that are more like humans: softer, more compliant.

Next Richard thought of using a mesh (G) and bought a batch of children's wedding gloves so he would have a supply to work with. He put a balloon inside some of this mesh, inflated it and it worked - the length of it shortened. This meant that he had a powered mechanism that showed potential for the smooth movements he wanted. It used the standard air supply, would fit in tight spaces, many of them together, without interfering with each other. The amount of movement was small but this was easily amplified by using a lever.

Looking around for alternative materials to use he found some braiding that was used for wrapping wires together. He used this with a rubber tube inside and established the fundamentals of the design. In the pictures of air muscles you can see the outer mesh or braiding and the feed tube for connecting to a compressed air supply to operate the muscles. This feeds air into the inner tube that you cannot see.

   A 40 mm diameter (large) air muscle

He then patented the system to protect his right to benefit from the ideas in it. The patent covers the whole system: an air muscle working a lever with a sensor to provide feedback to the controller about the distance moved. He has also filed patent applications to cover the way in which the rubber tube and mesh combination is sealed at the ends, as this is critical to the success of the design - and a bit tricky. The inner tube is made specially for the company and its specification is a 'trade secret'.

Other companies have made similar products but have had technical problems with them and only briefly sold them which emphasises the importance of details in Richard's design such as the sealing method. This means that the Shadow Company are the world leaders in both manufacturing and using air muscles. This brings financial benefits from sales but has also 'put them on the map' by linking them to people who build robots across the world.

The air muscle continues to sell because it has some special advantages over other alternatives. These include:

• light weight

• easy attachment

• heir ruggedness, high efficiency

• high power over short distances.

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