Motor inovations for walking/running cheetah speed robots

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Motor inovations for walking/running cheetah speed robots

Post by mantrid » Fri Mar 08, 2013 4:40 pm

Post by mantrid
Fri Mar 08, 2013 4:40 pm

http://phys.org/news/2013-03-cheetah-ro ... iency.html

Building a robot the size, weight and speed of a cheetah now seems a reality.
The advanced design of motors and control mechanisms may be of
interest to anyone building walking or running robots. It will be interesting
to see how long it takes for the high efficiency high torque motors to be widely available but they do seem very interesting.
http://phys.org/news/2013-03-cheetah-ro ... iency.html

Building a robot the size, weight and speed of a cheetah now seems a reality.
The advanced design of motors and control mechanisms may be of
interest to anyone building walking or running robots. It will be interesting
to see how long it takes for the high efficiency high torque motors to be widely available but they do seem very interesting.
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Post by PaulL » Sat Mar 09, 2013 3:17 pm

Post by PaulL
Sat Mar 09, 2013 3:17 pm

This all makes perfect sense. Optimal design is, well, optimal design. The best processes (software, mechanical, etc, etc) are simple.

They say this is advanced, but the reality is that what they're doing is putting force where it is needed by design instead of adapting off-the-shelf hardware. The more simple (direct) the drive train is, the better it works, the more efficient it becomes.

Swinging large masses around is going to create loss, period. The lighter a bot can be, the better it will perform. Falls won't be as fatal in a lighter bot unless the design is weak. It won't need as much power, meaning smaller and lighter batteries or more run time - but in best case scenario, and optimization of both.

Personally, I'm a fan of brushless motors built into wheels (this has been done on automobiles). Minimal gearing of a single motor per wheel is a close second. There's an electric "super car" that is pretty phenomenal that uses per-wheel gear driven motors.

If the motors and control system they've designed is as unique as they suggest, it will not be available to the general public for a very long time.

I'm guessing what they've done is to use a brushless design (neo magnets on rotor), but with no metal in the windings - like a reverse-coreless motor, likely with a large rotor diameter and more "steps" (coils) to get the torque. This is the best design I can think of. A slick control system would allow you to vary not only the drive current but the regenerative braking to get the "damping" variation mentioned.
This all makes perfect sense. Optimal design is, well, optimal design. The best processes (software, mechanical, etc, etc) are simple.

They say this is advanced, but the reality is that what they're doing is putting force where it is needed by design instead of adapting off-the-shelf hardware. The more simple (direct) the drive train is, the better it works, the more efficient it becomes.

Swinging large masses around is going to create loss, period. The lighter a bot can be, the better it will perform. Falls won't be as fatal in a lighter bot unless the design is weak. It won't need as much power, meaning smaller and lighter batteries or more run time - but in best case scenario, and optimization of both.

Personally, I'm a fan of brushless motors built into wheels (this has been done on automobiles). Minimal gearing of a single motor per wheel is a close second. There's an electric "super car" that is pretty phenomenal that uses per-wheel gear driven motors.

If the motors and control system they've designed is as unique as they suggest, it will not be available to the general public for a very long time.

I'm guessing what they've done is to use a brushless design (neo magnets on rotor), but with no metal in the windings - like a reverse-coreless motor, likely with a large rotor diameter and more "steps" (coils) to get the torque. This is the best design I can think of. A slick control system would allow you to vary not only the drive current but the regenerative braking to get the "damping" variation mentioned.
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Post by billyzelsnack » Sat Mar 09, 2013 11:11 pm

Post by billyzelsnack
Sat Mar 09, 2013 11:11 pm

I think the recent brushless motor based camera gimbal developments in the quadcopter community are going to be super useful for the robotics community in the near term.

http://www.rcgroups.com/forums/showthread.php?t=1815204

In the past few months quite a few low cost, large diameter, and many pole brushless motors have been released for the quadcopter community. The gimbal crowd have taken these motors and rewinded them to work better for closed loop positioning control. I expect in the next few months we'll see a ton of lost cost brushless motors meant for position control along with low cost controllers for them. Swapping out their IMU feedback setup for a magnetic encoder and you have a very good start towards a nice robot servo.
I think the recent brushless motor based camera gimbal developments in the quadcopter community are going to be super useful for the robotics community in the near term.

http://www.rcgroups.com/forums/showthread.php?t=1815204

In the past few months quite a few low cost, large diameter, and many pole brushless motors have been released for the quadcopter community. The gimbal crowd have taken these motors and rewinded them to work better for closed loop positioning control. I expect in the next few months we'll see a ton of lost cost brushless motors meant for position control along with low cost controllers for them. Swapping out their IMU feedback setup for a magnetic encoder and you have a very good start towards a nice robot servo.
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