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No more gearboxes -- you can have direct drive motors controlling everything. This would revolutionize robotics, compared to current systems that require a larg

by tlb 4y ago

No more gearboxes -- you can have direct drive motors controlling everything. This would revolutionize robotics, compared to current systems that require a large gear ratio between motor and joint, adding large amounts of inertia.

kibwen 4y ago
Can you elaborate on this? How does a superconductor help here?
- mikewarot 4y ago
  The magnetic field of a coil depends on the current, and the number of turns. If you have a sufficiently thin superconductor, and keep below the critical current density, you can ramp up the number of turns until you reach the physical space limitations. When you're working with a copper conductor, the thinner the wire, the higher the resistance, and you trade off turns for conductance (1/resistance). Thus, a superconductor offers the ability to put many more turns, or much higher current, into a given volume. You're limited with steel cores as to the maximum magnetic flux, but you could get the same flux with much lower power levels using superconducting coils. Alternatively, you could redesign your motor or actuator to be a coreless design, and you can then use much, much higher magnetic fields (up to the critical field of the superconductor).
- tlb 4y ago
  In a typical brushless motor, the torque is proportional to the magnetic field from the rotor times the current in the stator (non-rotating part). The best conventional magnets and conductors (neodymium-iron-boron and copper) can only generate a certain amount of torque without overheating due to the I^2R loss in the copper. This isn't nearly enough for most applications from driving vehicle wheels to robot joints, so motors need a step-down gearbox. For something like a walking robot knee joint, it needs around 15:1 torque multiplication. This makes it move "robotically", and not be able to absorb the impacts of running and jumping. A superconductor can handle much larger amounts of current than copper, and maybe also generate a higher magnetic field in the rotor, so you could get much higher torques directly from the motor. Superconductors still aren't ideal -- they stop being super in really high magnetic fields, perhaps because the electrons are moving in curves rather than straight and the complicated quantum effect that causes superconductivity doesn't work. But plausible superconductors could give great results.

by tlb 4y ago

kibwen 4y ago

Can you elaborate on this? How does a superconductor help here?

mikewarot 4y ago
The magnetic field of a coil depends on the current, and the number of turns. If you have a sufficiently thin superconductor, and keep below the critical current density, you can ramp up the number of turns until you reach the physical space limitations. When you're working with a copper conductor, the thinner the wire, the higher the resistance, and you trade off turns for conductance (1/resistance). Thus, a superconductor offers the ability to put many more turns, or much higher current, into a given volume. You're limited with steel cores as to the maximum magnetic flux, but you could get the same flux with much lower power levels using superconducting coils. Alternatively, you could redesign your motor or actuator to be a coreless design, and you can then use much, much higher magnetic fields (up to the critical field of the superconductor).
tlb 4y ago
In a typical brushless motor, the torque is proportional to the magnetic field from the rotor times the current in the stator (non-rotating part). The best conventional magnets and conductors (neodymium-iron-boron and copper) can only generate a certain amount of torque without overheating due to the I^2R loss in the copper. This isn't nearly enough for most applications from driving vehicle wheels to robot joints, so motors need a step-down gearbox. For something like a walking robot knee joint, it needs around 15:1 torque multiplication. This makes it move "robotically", and not be able to absorb the impacts of running and jumping. A superconductor can handle much larger amounts of current than copper, and maybe also generate a higher magnetic field in the rotor, so you could get much higher torques directly from the motor. Superconductors still aren't ideal -- they stop being super in really high magnetic fields, perhaps because the electrons are moving in curves rather than straight and the complicated quantum effect that causes superconductivity doesn't work. But plausible superconductors could give great results.