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Feb 24, 2016, 02:46 AM
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Regenerative springing

All the talk of motor braking brought up the subject of springs in legged walking robots. Springs are a popular topic in legged robots. The human body is modeled after springs which restore energy in the walking cycle. Actually, the human leg doesn't restore energy. Gravity extends the muscles, but all the energy required to contract the muscles in 1 cycle needs to be expended again in the next cycle. There is no restoration of energy in a human, but adding springs to robotic legs improves their efficiency.

Nevertheless, motors are very good at recovering the kinetic energy of a wheel. Not only can they stop wheels, but enough energy is recovered to recharge the battery & restart the wheels. An electric car in traffic is basically an electric spring with a small amount of energy added in each start to what is recovered in each braking.

Surely there is a way to replace the springs in the most efficient walking robots with some kind of regenerative braking & this mechanism could make legged mechanisms almost as efficient as wheels. It would be best realized in high voltage linear motors, but a good experiment would be trying to make a common brushless outrunner act like a spring with some kind of actively controlled capacitor, then measure the torque this mechanism can provide.

It probably could make a lot more torque with the capacitor mechanism than a motor driven straight from a battery. The capacitor could be charged to a very high voltage, pulsed through the motor to generate the 1st motion, then each subsequent motion would require a small topping off.

A legged robot driven by regenerative spring motors might be more efficient at running, but not at standing still.
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