Hanson, John

English

Loughborough University Library: Open Journals

IT IN D&TMuscling in:usingShadowMuscles forModellingEducational TechnologyConsultant, W. YorkshireI was recently bemoaning the inadequacies ofpneumatic equipment for technology when afriend drew my attention to a new developmentby Shadow Project, called Shadow Muscles.Intrigued by what I heard, I contacted them andwas lent a set to tryout.A Shadow Muscle looks like a long thin rubberbag in a tube of black plastic mesh similar tothe nets which oranges are packed in. Theycome in different sizes, most being about lOcmlong and 2cm wide; the longest is about 30cmlong and 2cm wide. Metal clips which can besqueezed on to close each end form loops inthe plastic mesh for fixing, and an air tubeemerges from one end. When you allowpressurised air into the tube, the rubber bagexpands and the mesh, also expanded, shortensits length and produces a pull on both ends.The plastic mesh restrains the rubber bag sothat it can expand fairly uniformly down itslength. They work (and look) like a humanbiceps muscle bending an arm and this analogyproduced the most rewarding model I madewith them.Shadow Muscle is a brilliantly simple conceptand much of the cleverness of this system liesin the software, interface and air control. On asturdy base plate is the computer interface andfour air control valves which require anexternal supply of pressurised air. The air pipesare easy to fit and helpful diagrams show youhow to connect them. You can work themdirectly by inflating one muscle from eachvalve, or use two valves for each muscle,which allows you to inflate the muscle, hold itinflated and actively empty it, all with precisecontrol.The interface is well built but unboxed. I liketo see the electronics showing: this helps toremove the black box mystique, but somepeople may find it intimidating, and others maybe tempted to tamper with it. The interfaceconnects with the serial port on the computerand has an expansion port which enables theconnection of additional interfaces and airvalves, and sockets for the connection ofsensors. The sensors are also sturdy with wellmade, easily obtainable components such asswitches which could easily be adapted to theuser's requirements. The software, which Iused with an Acorn Archimedes, is very visual,easy to use and very forgiving. I found thedirect control facility invaluable for testing theoperation of mechanisms I had built, before Ibegan to program them.I had several days of entertainment from usingthe system. Fairly experienced in the use ofinterfaces and control mechanisms, I waspleasantly surprised by the ease with which Icould build and use models with this system.The first model I tried was a Lego version of alife-sized animated head, which was originallybuilt as an illustration for the NCET IT in D&TGEST material. The large original had taken acolleague several days to build from wood andwas driven by large, conventional pneumaticvalves controlled by a separate interface. MyLego and Shadow Muscle version was roughlyhalf life size and although not as smoothlyoperating as the original, performed almost allthe same functions: the head turned, the tonguewent in and out and the eyes and ears moved.My model took about two hours to build, and Ispent less than half an hour producing aworkable program.Using the muscles rather than the usualpneumatic brute force pistons made me thinkmuch more carefully about the angles andpositions used in the construction. The musclesand the elastic bands used as antagonists to themuscles exert a tremendous static force on themodel, and several times joints collapsed underthese forces. At one point I managed to get themuscles to work in reverse because I had putthem under insufficient tension, and on severaloccasions a small change of angle producedvery large improvements. By the time I hadfinished construction, I had relearned severalvaluable lessons on forces and elasticity.The best model I built was a simple one of anarm, with a 30cm long Shadow Muscle as thebiceps and an elastic band as the triceps. IIT IN D&Tspent several hours experimenting with thissimple and easily constructed model andeventually, by adjusting the air valves and thetimings of the program, produced a verysmooth-running simulation of the arm lifting apair of scissors.The air can be supplied by a normalcompressor and the valves allow for a widerange of adjustment of pressure, but I workedthe system at home using a small air canisterand connection for an air brush, and had fewproblems. The ease of use and flexibility of airsupply could put this interesting area ofpneumatics within the reach of primary schoolswithout compressors.This is a very interesting and excitingdevelopment in control technology and willstrongly contribute to the use of pneumatics. Ican see some very useful teaching points in thearea of forces, angles and elasticity. Theconcept is a radical jump away fromconventional pneumatics and makes a difficultarea much easier to understand. It does notrelate in any way to the industrial use ofpneumatics but is very appropriate to themechanisms used at school level. Wellsupported by an excellent manual, goodsoftware and sturdy equipment, ShadowMuscle gives the impression of careful thoughtand quality. A little more development in itsuse in a range of educational situations (andadaptation to other computer platforms andinterfaces), and it provides a creative, pleasingand long needed innovation.Shadow Muscle is available from ShadowProject, 357 Liverpool Road, London N1 1NL.Tel: 071-7002487. The Shadow Kit costs £299and includes control board, software, 11muscles, sensors, switches, air pipes and 12vpower supply.

Muscling in: using Shadow Muscles for Modelling

https://ojs.lboro.ac.uk/DTT/article/view/1371/1331

Muscling in: using Shadow Muscles for Modelling

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