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Lucy MkI used simple servomotors rigged up to behave roughly like pairs of muscles. However, these had many problems:
For Lucy MkII we needed far more powerful and responsive muscles, with more biologically realistic qualities. This latter point is important. The vast majority of robots use 'stiff' motor systems - their limbs are directly connected to the gearboxes of the motors. This is very unlike the muscles of animals in several ways:
Unfortunately, there are no current technologies that can match animal muscle for length of stroke, speed, elasticity, strength and efficiency. There are many materials under development - memory alloys, hydrogels, pneumatics, etc. - that may fit the bill one day, but for the moment ordinary DC motors are about the only easily accessible source of motive power. The problem is how to make motors emulate muscles. My first solution was to use an elastic actuator, similar in concept to those used in MIT's Cog robot. This had both practical and theoretical problems. The second solution was really neat - much simpler, cheaper and more biological in its qualities. However, so far I've been unable to reduce the vibration to a satisfactory level, given the engineering facilities available and the space constraints in the robot. Sadly I couldn't perfect this method and eventually ran out of time and money, so finally I've plumped for a third solution which is nowhere near as nice but has the considerable advantage of actually working! |
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