Quad 4DOF Mech - Immortal

**cire** · 09-25-2010

After several years of saying I'm going to build a robot for a competition, I finally decided to go for it at the beginning of September. Mech Warfare looked like the sweetest thing since I saw it a few months ago on Botjunkie.com.

One of my main goals for this project is to learn more about electronics and programming. I have been exposed a bit to both before, but I still don't really know what I'm doing in either. Hopefully I can take away some new knowledge from this project.

After much research I decided that I'd buy a Bioloid kit since it comes with enough servo's to make a good bot and I would be able to try out a walking robot before I start designing the rest of my robot, since I've only dealt with wheeled robots before.

Edit <Added pictures of my Bioloid adventures>

The first thing I did when I got the Bioloid kit was build the humanoid, which was pretty cool. I spent a day or two playing around Robotis programs. I installed Roboplus and made some pretty cool actions.

I found it really hard to get the biped walking good, so i decided I would start off with a quadraped since this is my first step into walking robots. Here is gen 1 quad:

I didn't quite like my setup, I wanted to bring the legs in a little closer so I rebuilt it using the same sort of setup that the ankles of the bioloid kit has, I also added supper bouncy balls as feet since I thought it would be cool:

I didn't like the lack of freedom the legs had though, and this was when I decided that I should make my bot like an Immortal from Starcraft 2, bringing my other hobby of playing video games into my hobby of building robots

The shoulder joints are all very close to the center, and the legs can extend out very long.

Starcraft 2 unit "Immortal" in the map editor:

I have used this to analyze what basic shape the Immortal has, and its walking animations. I didn't really have very high hopes on the walking animation actually being useful, since its an video game and not the real world. I decided to use the Bioloid motion tools to make it walk like the immortal anyways, and it turns out that it worked REALLY well. I will post a video when my card reader gets here. It is pretty much the sweetest thing ever, although I am slightly worried if I'll be able to program it.

Here is the video of the immortal mock up walking:

[ame="http://www.youtube.com/watch?v=wnQmmqA0CGQ"]YouTube - Immortal Walking[/ame]

I tried to keep to the shape of the Immortal as close as possible, just because I think its cool. Eventually I want to put some sort of shell on it so it can look just like the real thing.

After I proved that it could walk, I started making the actual design in SolidWorks, it is by no means complete yet, but here is the current progress (as of this post):

Question - Are those target plate position legal (red squares)? I know the rules say they have to be on your turret if you have one, but I don't want to add more weight to the turret

. Although I know that the legs might interfere with the targets. Right now I am looking at having 2 tank guns, one on each side of the turret. If anyone has 3d models for those tank guns, it would be helpful!

The majority is either purchased parts or sheet metal parts that I will probably have bigbluesaw.com waterjet for me. I have limited access to tooling in my apartment so outsourcing the majority is required. I plan on buying a small brake to bend all the brackets.

My next steps are:
Finish CAD Model
Learn how to use my Arbotix
Buy a soldering Iron (I'm not even sure what I'll have to do electronic wise)
many more...

Thanks for reading!

~ Cire

**cire** · 09-26-2010

I decided to revisit my legs and make them using a sheet metal method similar to whats used on aircraft. Instead of having thick pieces to make a sort of frame I used thinner material and made a skin for the the legs, which also allowed me to make it much closer to what the "real" thing looks like too. Overall it weighs 40 grams less as well. It will make bending the brackets much more challenging though...

**Xevel** · 09-27-2010

This looks nice!
The second version looks much more impressive (huge legs!). I look forward to see how it will evolves.

**Stobs** · 09-28-2010

[s]I was wonder what drawing program you used for this cire?[/s] [Edit: SolidWorks; that's what I get for not reading the entire post & all posts in the thread first! :/] Were the servos and other pieces part of an included/add-on library, or did you create them yourself as an item/object?

**cire** · 09-28-2010

Originally Posted by Stobs

[s]I was wonder what drawing program you used for this cire?[/s] [Edit: SolidWorks; that's what I get for not reading the entire post & all posts in the thread first! :/] Were the servos and other pieces part of an included/add-on library, or did you create them yourself as an item/object?

I downloaded all of the brackets from Trossen's website, if you click on the individual brackets in the store you can download a zip file with an Inventor part and a SolidWorks part for all the brackets as well as the servo's. Although the ax12 link wasn't working so I downloaded it from another website, of which I cannot remember right now.

**Stobs** · 09-29-2010

Thanks for the reply cire, much appreciated.

**cire** · 09-30-2010

I got my card reader today, and I uploaded some better pictures and a video of it walking! (In the first post)

And your welcome Stobs

**cire** · 10-13-2010

Its been a while since I updated this, but heres what I've been up to:

I got my battery and Arbotix all set up and got code working with some help from Fergs, although I still haven't been able to get it to walk with the NUKE code, something I will work on later. For now I have just been ignore the foot servo on each leg so I can use the 3dof code.

Last Friday I got my parts in from BigBlueSaw, which is quite impressive how fast they got those here... Here is a picture of each unique part straight from the box:

I opted not to pay for a basic finish, so I spent a couple days filing all those rough edges down. Everything seemed to fit pretty well, although all of the holes for bearings had to be cleaned a bit to make sure they fit properly. The first thing I did was assemble Immortals chassis with the existing Bioloid legs I had made previously, and all the servo's fit properly. The chassis is quite rigid, even though the material is only 0.040" thick, mostly due to the fact that theres 5 servo's acting as spacers between the two sheets. I was also impressed at how good the "IMMORTAL" Lettering came out, I just imported StarCraft font directly into my model, and the only part that got cut out was the O, everything else stayed in tact.

On Monday I got my 24" Finger brake from Grizzly, It was pretty much ready to go straight out of the box. Since I am using 6061 Aluminum I made a few test bends before I went ahead and started bending my waterjet parts, and I was quite happy with the bends I was getting, as long as I left a decent gab between the apron and the finger knife edge. The radius is sufficient enough for the thin material to not crack, but still be a good bend.

Now I had my parts profiled out, and my brake, I started bending the parts.. This is when reality set in and I realized what I was too afraid to think about before, the fact that none of my parts can actualy be completely bent by a my little finger brake... Either it was interference with the short fingers, or just interference within the part itself, I had lots of issues with all the parts. One prime example is the foot, The way its layed out I had to bend the triangle portion and the servo mounting portions about 10 degrees at a time, so that I didn't deform the foot. This wasn't too bad though, since I only have to make 4 of them. The other big one is the shoulder bracket, which I had already known was impossible to bend since its essentialy a tube. I managed to get around these by bending them mostly on the brake, and then finishing off the bend by hand or adjustable wrench. Here are some of the first parts I bent, before the finishing touches by hand:

Here is the first leg I put together, which also brought a bunch of realities I hadn't really thought about before when I designed it. First off, its an extreme pain to assemble the portions where I have to put 4 screws in with 2 spacers on each, on the far inside of the leg where the servo makes it impossible to get anything in there. I spent a really long time getting it together. The other thing, is that the shortest screws that come with the Bioloid kit are actually too long when bolting into the servo horns, because the sheet metal is so thin the bolts just barely run into the face of the servo... It took me a while to realize why the servo's were so hard to turn, and then I noticed little bits of black plastic coming out of them... So I temporary have solved this by using longer screws and my spacers.

Here is the robot chassis, with 3 Bioloid legs attached, and the new leg next to it. I also have the Arbotix and battery mounted underneath, which you can't really see in the picture.

Also, an updated Solidworks Model of Immortal, currently with 2 defenders up top... I haven't picked out the details for my guns fully yet.

I still have a ton to do, but Its starting to take shape now!

**Stobs** · 10-13-2010

cire, did you use the same servos as original to the Bioloid kit to build Immortal, or did you change them up along with the (SWEET!) brackets? Project's looking good!

Stobs/Paul

[PS: am I misinterpreting the drawing or are the scoring panels going to cover up the "Immortal" plates? ^.o]