
Using OpenAI Gym to train an open-source 3D printed robot - nicrusso7
https://github.com/nicrusso7/rex-gym
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gene-h
It's unfortunate that we still don't have cheap torque controlled robot
actuators. Controlling force rather than position led to a drastic improvement
in walking robots. I would also highly recommend using something beefier than
an arduino to control a walking robot as most approaches to walking robots
today rely on performing fast optimization. MIT's minicheetah has used a
control approach that involves simulating the robot about 0.5 seconds into the
future 50 times a second.

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jonnycowboy
We actually have very cheap and pretty powerful position-controlled actuators
(hobby servo motors). Attach any kind of spring and displacement measurement
device (potentiometer, hall sensor, optical, LVDT, etc) and voila, instant
torque controlled actuator.

You can look up Series Elastic Actuators for more info or use this article as
guidance (any spring will do as long as the force range and spring constant is
adequate).

[https://www.sciencedirect.com/science/article/pii/S240589631...](https://www.sciencedirect.com/science/article/pii/S2405896315026439)

~~~
gene-h
The servo they use is $493[0], at that price I wouldn't necessarily consider
it a hobby servo. The control for that specific series elastic servo needs
some work. There have been other attempts at making cheap series elastic
actuators. An interesting one was the programmable spring work[2][3]. Although
one problem with series elastic actuators is that they can be difficult to
control because of the compliance. Force servos were also an interesting
attempt at doing cheap force control[4] and by using load cells they avoided
the compliance problem. Unfortunately, force servos did not have any position
control.

[0][http://www.robotis.us/dynamixel-mx-106t/](http://www.robotis.us/dynamixel-
mx-106t/)
[1][https://www.youtube.com/watch?v=sjFR4ACVLmk](https://www.youtube.com/watch?v=sjFR4ACVLmk)
[2][http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.147....](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.147.3257)
[3][https://www.youtube.com/watch?v=_g79mOSvSsE](https://www.youtube.com/watch?v=_g79mOSvSsE)
[4][https://www.youtube.com/watch?v=sjFR4ACVLmk](https://www.youtube.com/watch?v=sjFR4ACVLmk)

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mrfusion
I recently came across this life sized robot you can 3d print:
[http://inmoov.fr/build-yours/](http://inmoov.fr/build-yours/)

I’d love to try it. I couldn’t determine if it can walk or not.

~~~
KingFelix
I've been wanting to build this for awhile, it looks pretty awesome.

~~~
mrfusion
Wow. Reach out if you do. I want to do it too but it looks like such a huge
undertaking.

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mkagenius
Is the aim of the project to ultimately make the printed robot to run and
walk?

Maybe the next step will involve fitting servo motors on to the robot?

~~~
akavel
IIUC, SpotMicro seems to be a project that already has this part sorted out:
[https://youtube.com/results?search_query=spotmicro](https://youtube.com/results?search_query=spotmicro)

~~~
ipsum2
I don't see any of those videos actually demonstrating Spot Mini walking
successfully. Some comments suggest that the motors are not strong enough, or
the body is too heavy.

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mrfusion
Is there any research on training a robot to walk from scratch. Ie having it
learn from the ground up just trying different motions.

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Cogito
As per the tradition [0]:

 _In the days when Sussman was a novice, Minsky once came to him as he sat
hacking at the PDP-6.

“What are you doing?”, asked Minsky.

“I am training a randomly wired neural net to play Tic-Tac-Toe” Sussman
replied.

“Why is the net wired randomly?”, asked Minsky.

“I do not want it to have any preconceptions of how to play”, Sussman said.

Minsky then shut his eyes.

“Why do you close your eyes?”, Sussman asked his teacher.

“So that the room will be empty.”

At that moment, Sussman was enlightened._

[0]
[http://catb.org/jargon/html/koans.html](http://catb.org/jargon/html/koans.html)

~~~
dekhn
The more times I read this, the deeper it gets, and the more I appreciate
modern machine learning.

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syntaxing
This is awesome! I wish there was a video showing the results. This might be
my next project!

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nicrusso7
Thanks! I'm currently working on the 'knowledge transfer', the aim is to build
an almost-real-time controller for the robot - I'll probably start with a web
app. Any contribution is welcomed!! :)

~~~
syntaxing
Yes!!! Is it part of the same repo? I'm a MechE but my software is decent
enough for prototypes!

~~~
nicrusso7
nope, I'll publish rex-robot repo asap ;)

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awinter-py
even cooler if the anatomy of the robot were optimized in the gym as well, and
then you just ship it to the printer

