Micro Quadrapod

[Tyberius]

Hey guys,

Just thought I'd share a side project I'm working on (Johnny 5 project has most my spare time tied up atm). This is a fully custom quadrapod based on the HS-81 micro servos. It was designed in Autocad and machined via a CNC machine (much thanks to JonHylands for that service).

Here are a few shots of it without electronics mounted:

http://img84.imageshack.us/img84/7643/dscn0268gv3.th.jpg (http://img84.imageshack.us/my.php?image=dscn0268gv3.jpg)

http://img165.imageshack.us/img165/756/dscn0269rt1.th.jpg (http://img165.imageshack.us/my.php?image=dscn0269rt1.jpg)

http://img101.imageshack.us/img101/1818/dscn0270nf0.th.jpg (http://img101.imageshack.us/my.php?image=dscn0270nf0.jpg)

http://img101.imageshack.us/img101/1779/dscn0271hn4.th.jpg (http://img101.imageshack.us/my.php?image=dscn0271hn4.jpg)

http://img84.imageshack.us/img84/7672/dscn0272ku5.th.jpg (http://img84.imageshack.us/my.php?image=dscn0272ku5.jpg)

http://img84.imageshack.us/img84/5907/dscn0273hf7.th.jpg (http://img84.imageshack.us/my.php?image=dscn0273hf7.jpg)

For size comparison:

http://img165.imageshack.us/img165/4336/dscn0274gg1.th.jpg (http://img165.imageshack.us/my.php?image=dscn0274gg1.jpg)

http://img171.imageshack.us/img171/8458/pict0013hd1.th.jpg (http://img171.imageshack.us/my.php?image=pict0013hd1.jpg)



Here it is with the SSC-32 and Bluesmirf Bluetooth module mounted:

http://img525.imageshack.us/img525/4360/img0401qb0.th.jpg (http://img525.imageshack.us/my.php?image=img0401qb0.jpg)

http://img143.imageshack.us/img143/2880/img0402xk6.th.jpg (http://img143.imageshack.us/my.php?image=img0402xk6.jpg)

http://img143.imageshack.us/img143/2301/img0404yr8.th.jpg (http://img143.imageshack.us/my.php?image=img0404yr8.jpg)


Batteries will be mounted around the body standoffs in between the top and bottom plates, I have some very small sub-c style nimh batteries (1400mh) that I'm creating a custom battery pack with. For now while I develop the walking gaits, I'm just going to be controlling it directly from my laptop via the Bluesmirf link and creating the gaits in SEQ. The next phase, once the gaits are established, is to develop an autonomous navigation program using a spare Ping ultrasonic sensor I have.

I'm undecided as to what onboard microcontroller I want to use (I might go with a Gumstix, I've heard good things about those). As far as navigation, I'm looking at mounting the Ping sensor on a small stepper motor for 360 degree distance measurement, ideally it would take distance measurements at every say... 5-15 degrees and create a small radial map, and then use that for navigation.

Once I get things a bit more finalized with my Johnny 5 pico-itx project, I'll move back to this one. I'll post video once I get the walking gaits finished though.

Anyway, still work in progress. Let me know what you think ;)

[asbrandsson]

Hello,

That is very interesting. What are you planning to mount on top of it?

Asbrandsson

[Tyberius]

As little as possible, at most a microcontroller and ultrasonic sensor turret for navigation. As it's pretty small, and uses micro-servos, I need to keep weight to a minimum.

[Matt]

IT'S SOOOOO CUTE! :robotsurprised:

I want video! You should cover it in fuzzy skin to creep out girls with it. (I know, I'm totally 5 years old still)

Nice design BTW, I like the simplicity of using servo horns for connecting pieces and double stick tape to just secure two servos to each other. Keeps things light weight and costs down. I could see this being a nice learning kit eventually.

[Tyberius]

Unfortunately for now, it's back to the drawing board on this one. The servos I used just don't feel like they're going to be solid enough for consistent use. It's jittery just standing on 4 legs and has seizures when it goes up on 3... and this is without batteries onboard yet :(

I'm thinking this could be fixed easily with some higher torque micro servos, but unfortunately my robot budget is being eaten up by a ton of upgrades I have in the works for my Johnny 5, so for the time being this project is being shelved.

[Matt]

Maybe you could try just shortening the leg sections. They do look a little long for those tiny servos. His steps will be shorter, but that would be cool anyhow, skittering around like a tiny bug.

[Tyberius]

That's actually what I did when I first powered him up and noticed that, I removed the middle servo arms that made up the center femur piece and just used the two half-arms together. It helped a bit, but once I added the weight of the batteries, it started trembling just as bad.

It would be feasible using these servos if it were a 2 dof walker, and the vertical motion were setup through an indirect drive... but I've built 2dof quadrapods before and I wanted to experiment with 3dof on this project. I'm probably just going to end up redesigning the tibias and body, and use higher torque servos, I could still keep him tiny.

[tom_chang79]

How about a LiPo solution to your battery weight problem? Going with a stronger servo would be the ultimate solution, but adding another two legs and turning it into a hexapod is also a solution since you'll have two extra legs to offload some of the payload.