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LEGS
Why not give your robot some legs? In Robot Constructor, you can give your robot two legs or four legs.
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Four legs
Giving your robot four legs means it can walk up slopes or over uneven ground and it can also balance - which is a big issue for walking robots. With four or more legs, robots are said to have 'static stability' which means their centre of gravity is kept within their four legs and so they can still balance even when just three legs are in contact with the ground. Most static-balanced robots have six legs which makes them look like insects but also gives them even more stability than a four legged robot. Unfortunately, all those legs mean that the robot needs more motors or electromagnetic servos to propel it and it therefore uses a lot of power.
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Image courtesy of NASA/JPL/Caltech
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Two legs
Giving your robot two legs like the Honda P3 makes it lighter and more efficient than a four or six legged robot. But a two legged robot needs to be able to balance - and that's complicated. These robots have what's called, an inclinometer - a small, fluid filled bulb which senses the robot's orientation. Information from the inclinometer is sent to the robot's computer processor. Sensors located throughout the robot's body also send information to the processor so it knows precisely where the body, arms and legs are in space. The processor constantly analyses the information from both the inclinometer and sensors to allow it to decide how it should move the robot's arms and legs to ensure it keeps its balance. Two legged robots move in a series of leaps with the legs of the robot absorbing the forces when it lands before delivering a strong impulse for the next step. All this requires quite a lot of power as well as fast computing power to process all of the posture and balance information from the sensors.
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 So how do humans balance?
Fortunately, as well as allowing us to hear, our ears also have a very sensitive balancing mechanism. The ear has three distinct parts, the outer, middle and inner ear. The part we can see is the outer ear. This funnels the vibrating air carrying the sound in towards the ear drum. The vibrations are passed along the three small bones in the middle ear to the inner ear which does two things. It allows us to hear sound and also detect the position and movement of the head which allows us to balance.
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How do we know when our head moves?
The semi-circular canals send information to our brain about our position - for example, are we upright, laying down etc. The three fluid filled canals are positioned at right angles to each other and each has a swelling near one end, called the ampulla. Each ampulla has sensory hair cells (which are embedded in a blob of jelly) attached to nerve endings. When the head moves the fluid is set moving in one or more of the semi circular canals which in turn moves the jelly which bends the hair sending signals to the brain!
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MOBILITY legs crawler tracks wheels
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