
Ghost Robotics' Minitaur Quadruped Conquers Stairs, Doors, Fences - sohkamyung
http://spectrum.ieee.org/automaton/robotics/robotics-hardware/ghost-robotics-minitaur-quadruped
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ChuckMcM
That is super awesome and even more awesome when I read that those are _direct
drive_ motors. All the compliance is done in software. This is something I
must spend some time playing with. That advent of these small brushless motors
with insane amounts of torque makes all sort of things possible that weren't
before.

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Terr_
I imagine that this stuff will be great for prototyping algorithms and
figuring out good applications/requirements, but eventually (like when stuff
has to be mass-produced) you'll see physical structures coming back in.

Either gearwork or biologically-inspired designs, replacing some flexible
electric rules and brawn with structures that have rules and brawn "baked in".

Sort of like how your knees aren't "soft-coded" for a particular set of
angles, it's an emergent property of a system shaped by a particular use.

~~~
ansible
_I imagine that this stuff will be great for prototyping algorithms and
figuring out good applications /requirements, but eventually (like when stuff
has to be mass-produced) you'll see physical structures coming back in._

I don't know about that.

This platform can be fairly cheap in mass production. The legs are really
cheap. No gears. And just two motors per leg. No extra force sensors, just the
control electronics.

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mdda
But if you added (say) a spring into the linkages, the rest-position could be
tuned mechanically to be more energy efficient (e.g: zero power). The effect
of the spring could be backed out in software.

But it's not until people have played with the use-cases, etc, that one really
needs to think about efficiency in terms of battery life.

~~~
ansible
_But if you added (say) a spring into the linkages, the rest-position could be
tuned mechanically to be more energy efficient (e.g: zero power)._

That might help with one particular gait, but I think it wouldn't give as much
benefit for a system as flexible as this, which can run, hop, trot, and more.

And the spring itself would need to be modeled, and would make the position
and force measurements less sensitive. That's why I don't think it would be a
net win.

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tlb
Impressive to make it work with direct-drive actuators. The previous lowest
gear ratio I know about was the MIT Cheetah, at 5.8:1. Detailed comparative
analysis at [http://biomimetics.mit.edu/research/optimal-actuator-
design](http://biomimetics.mit.edu/research/optimal-actuator-design)

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scotty79
I'm quite amazed that using springs in robots is sort of a new thing.

I was thinking about making amateur robot with two wiper motors, in-parallel,
through strings, per joint. Wiper motors seem to me to be pretty fast and
strong (and cheap), and use worm gear so they could hold the springs tensed
without using energy proportional to tension. Keyword: "variable stiffness
joint"
[http://www.mdpi.com/actuators/actuators-03-00270/article_dep...](http://www.mdpi.com/actuators/actuators-03-00270/article_deploy/html/images/actuators-03-00270-g002-1024.png)

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acupofnope
Surely I'm not the only one who thinks this robot looks like a very happy
little goat? :-)

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eggy
The door opening and fence climbing sequence were impressive. Did onboard
video, CV and CPU result in being able to do the acrobatics trajectory to hit
the door handle, or was it human operator driven?

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sohkamyung
I believe it was all onboard, not human operator driven. In the article,
Kenneally describes how the robot opens the door and says this: _Once it
perceives contact with the door knob, it retracts the leg, moves it over a
little bit, and then extends it, and that actually all happens within 50
milliseconds, so it’s incredibly fast._

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eggy
Thanks! I'll give it a closer read later. Impressive in any case.

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unhelpful
It runs just like loca
[https://www.youtube.com/watch?v=x2RJN9a_jdM](https://www.youtube.com/watch?v=x2RJN9a_jdM)

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jotux
Reminds me of this robot from a researcher at McGill:
[http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.61....](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.61.8511&rep=rep1&type=pdf)

[https://www.youtube.com/watch?v=KW5FR3rmI4w](https://www.youtube.com/watch?v=KW5FR3rmI4w)

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Animats
That's where Boston Dynamics got their legged locomotion technology. They
hired the professor at McGill, Dr. Martin Buehler, who was in charge of that
project.

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_Adam
This is super cool. What motor does it use? I didn't know such a small,
torquey direct drive actuator existed!

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ziikutv
They use direct-drive electric motors. Those are motors that you typically see
on washing machines. They have super high torque but low speed which works in
their use case.

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brak2718
A similar concept -- variable compliance -- that's been around for a while is
called series elastic actuators. With geared motors you think in terms of
position and speed. With direct drive or series elastic you are instead
controlling torque.

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JoeAltmaier
Some thoughts: Looks too cute. Only two legs away from being a giant spider.
Bouncing around like that, it may not be a very useful robot. Won't be
carrying my drinks for instance. Or taking non-blurry pictures of anything.

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ansible
Less parts, more smarts.

I love this design.

