Let's Make Robots!

812-R7 Biped

Walks in a circle (no, not on purpose)

*Update 2010 Jan. 26* 
I figured out one of the problems with R7 was there was too much flexibility in its feet. I added several polymorph goobers around the edge and against the brackets to strengthen them up a bit. Now it doesn't fall flat on its face anymore! I even managed to get some (crappy cellphone) video so you can have a look at R7 taking its first (mostly) successful steps. Definitely got quite a bit of work to do on the programming...


I've been wanting a biped for quite some time now. With the holiday acquisition of half-a-dozen micro servos and a kilogram of polymorph I've finally got this project underway. I won't write a whole helluva lot here right now, y'all will have to mostly settle for a few captioned photos.

Most of the polymorph is rolled flat using ~1/16 inch thick tongue depressors as guides. Then cut, sliced, bent, melted, rebent and stuck in a U shape. The pivots are 22g copper wire, not the most robust choice for hinge material.

Currently there are ten micro servos. I only had 8 of the Dagu servos, so the two black ones (shoulder rotate) are pirated from my helicopter.

The brain is an ATMega168 @ 16MHz running the Arduino bootloader for easy programming. The board is a Gadget Gangster half-size project board. 12 of the 'mega's digital pins are brought out to three-pin "servo style" headers, with a strip of female headers above. Obviously only ten are currently in use by servos. D13 has a bright blue LED for debugging just plugged into the female headers. None of the analog pins are brought out yet. Top left is a 1x6 right-angle header for the programming cable. There's a 5V LDO regulator to provide power to the chip from 4 AA or AAA batteries (alkaline, totalling ~6V). The servos get their power straight from the batteries.

In all the whole thing is quite wobbly. Combined with the fact that I don't have a clue what I'm doing, R7 manages to get about 1.5 steps before tipping over on its face. I'm fairly certain a redesign of the feet and ankles is my next step before working very hard on a walking sequence. I have managed to get it to move to standing on one foot though. That felt like at least a small win ;)

For now I need to get back to working on LMR again, so it may be a little bit before I do more on this. Hopefully I'll come up with a proper name for it too.


Hips and Knees - front

Right knee and ankle - front

closer view of right ankle - front

knees - front

hips - front

left shoulder and elbow - front

left elbow


legs - back

left ankle

left leg. Also shows a little bit of the Erector stand I knocked together to hang the bot for programming

Brain "backpack"

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I'm also building a biped robot from polymorph. I'm using normal servos rather than micro servos. So far its working good but I only have a foot and ankle. Check out my video here: http://www.youtube.com/watch?v=kIIj24QO-9o&list=PL070iJmUMvTimYlgl-lC6JS_RYqMMEnfc&index=1 any tips would be appreciated. :D

Yes, yes. Very impressive, a walking robot. But when will you add an eye patch and teach it to say, 'arrggghh!'

Seriously. Nice work.

Interesting picture, a ping))) or sharp with a patch over one "eye". Could be interesting.

Right now, though, it has no head at all. I always imagine that Denis Leary song ("Traditional Irish Folk Song") playing

They come over here and they take all our land
They chop of our heads and they boil them in oil
Our children are leaving and we have no heads
We drink and we sing and we drink and we die
We have no heads, no we have no heads


OK, if you robot can sing Denis Leary's "Traditional Irish Folk Song", that'd be OK too. Extra credit if it can dance a jig.
Oh well, the photos look great and Frits is excited, what more can you ask for :D

I grabbed some video with the better camera. Unfortunately it's pretty hard to see too, the lighting in my house blows. Still, here it is (~7MB) in .wmv format. Let me know if that works out for you. If it does I'll make sure to put future videos up in that format at that location in addition to ye olde youtube. If the formatting doesn't work I can try other things too, that one's converted to .wmv on a linux box (from .mov), so it may not be acceptable by a real windows machine.

I'll put real effort into watchable video after I get the code working better and the bot actually walking in a straight line ;) As it is now it kinda looks like it's been hitting the rum (or its programmer has)

Hey man, vid works fine for me on Windows 7 w/ generic brand Windows Media Player. 812's got the moves =)

Cool, thanks!

Just to clarify, 812 is my LMR user number, this bot is R7, my 7th since joining LMR. R5 (XMOS bot #1), R6 (Mr. General), and R8 (XMOS #2) aren't posted yet. I gave up trying to come up with "real" names at R3 ;)

...I knew that. I was just... referring to your pirate moves. Yes, that was it. Definitely.

Anyway R7 can also be seen displaying some fancy footwork =)

I'll get some video with the real camera in the next couple days and put it up somewhere else. this one is from my phone and nigh unwatchable anyway :)